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Systematic and ecological relations of Peromyscus oreas and P. maniculatas Sheppe, Walter Alvin 1958

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SYSTEMATIC AND ECOLOGICAL RELATIONS OF PEROMYSCUS OREAS AND P. MANICULATUS hy WALTER ALVIN SHEPPE, JR. A t h e s i s submitted i n p a r t i a l f u l f i l l m e n t of the requirements f o r the degree of DOCTOR OF PHILOSOPHY i n the Department of Zoology We accept t h i s t h e s i s as conforming t o the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA May, 1958 %[]t P t t t t i e r g t t g of ^ r i t t s i j Columbia F a c u l t y o f G r a d u a t e S t u d i e s P R O G R A M M E O F T H E FINAL ORAL EXAMINATION F O R T H E D E G R E E O F DOCTOR OF PHILOSOPHY of W A L T E R A L V I N S H E P P E , JR. B. A. College of William and Mary M . A . University of British Columbia IN R O O M 187A, BIOLOGICAL SCIENCES BUILDING M O N D A Y , A P R I L 28, 1958 at 2:30 p. m. C O M M I T T E E I N C H A R G E D E A N G . M . SHRUM, Chairman I. McT. C O W A N . T. M . C. T A Y L O R W. S. H O A R G. S. A L L E N C. C. L I N D S E Y F . L A S S E R R E J. R. A D A M S M . D. F . U D V A R D Y External Examiner: 0. P. P E A R S O N University of California A B S T R A C T Systematic analysis of 2500 Peromyscus specimens from Washington and British Columbia shows that P. oreas is largely reproductively isolated from P. maniculatus, and it is raised to specific status. These species maintain their identities over large areas in which they are sympatric. Some specimens may be hybrids, and a few samples may be from intergrade populations. P. m. austerus and P. m. artemisiae produced fertile hybrids in the laboratory, but P. oreas failed to breed. Field studies revealed that oreas and maniculatus are in part ecologically isolated in areas where both occur. Both species have more restricted habitat distri-bution in the presence of the other, and interspecific competition is suggested as a cause. Greatest reproductive activity was in spring and early summer; there was no breeding in late summer. Oreas ceased to breed earlier than maniculatus. .In June adults outnumbered young of the year in the catch, but, by July this was reversed. Young males were caught more often than young females, but adult females were caught more often than adult males, suggesting that females live longer than males. Oreas prob-ably developed partial reproductive isolation when separated from other Peromyscus stocks by Pleistocene glaciation. It has remained distinct from maniculatus through a combination of geographical, ecological, temporal, psychological, and genetic isolation. P U B L I C A T I O N Sheppe, W . A . and J. R. Adams. The pathogenic effect of Trypano-soma duttoni in hosts under stress conditions. Jour. Parasit. 43: 55-59, 1957. G R A D U A T E S T U D I E S Field of Study: Mammalogy Biology of Vertebrates I. M c T . Cowan Population Dynamics P. A . larkin Terrestrial Zoogeography M . D . F. Udvardy Advanced Parasitology J. R- Adams Systematic Mammalogy S. Benson Dynamics of Vertebarte Populations F. A . Pitelka Other Studies: Plant Ecology Immunology i i . ABSTRACT Systematic analysis of 2500 Peromyscus specimens from Washington and British Columbia shows that P. oreas i s largely reproduetively isolated from P. maniculatus. and i t i s raised to specific status. These species maintain their identities over large areas i n which they are sympa-t r i c . Some specimens may be hybrids, and a few samples may be from intergrade populations. P. m. austerus and P. m. artemisiae produced f e r t i l e hybrids i n the laboratory, but P. oreas failed to breed. Field studies revealed that oreas and maniculatus are i n part ecologically isolated i n areas where both occur. Both species have more restricted habitat distribution i n the presence of the other, and inter-specific competition i s suggested as a cause. Greatest re-productive activity was i n spring and early summer; there was no breeding in late summer. Oreas ceased to breed ear-l i e r than maniculatus. In June adults outnumbered young of the year in the catch, but by July this was reversed. Young males were caught more often than young females, but adult females were caught more often than adult males, suggesting that females liv e longer than males. Oreas probably developed partial reproductive isolation when separated from other Pero- myscus stocks by Pleistocene glaciation. It has remained dis-i i i . tinct from maniculatus through a combination of geographical, ecological, temporal, psychological, and genetic isolation. We aeeept this thesis as conforming to the required standard i F a c u l t y o f G r a d u a t e S t u d i e s P R O G R A M M E O F T H E FINAL ORAL EXAMINATION F O R T H E D E G R E E O F DOCTOR OF PHILOSOPHY of W A L T E R A L V I N S H E P P E , JR. B. A. College of William and Mary M . A . University of British Columbia IN R O O M 187A, BIOLOGICAL SCIENCES BUILDING M O N D A Y , A P R I L 28, 1958 at 2:30 p. m. C O M M I T T E E I N C H A R G E D E A N G . M . SHRUM, Chairman I. McT. COWAN T. M . C. T A Y L O R W. S. HOAR G. S. A L L E N C. C. L I N D S E Y F . L A S S E R R E J. R. A D A M S M . D. F . U D V A R D Y External Examiner: O. P. P E A R S O N University of California A B S T R A C T Systematic analysis of 2500 Peromyscus specimens from Washington and British Columbia shows that P. oreas is largely reproductively isolated from P. maniculatus, and it is raised to specific status. These species maintain their identities over large areas in which they are sympatric. Some specimens may be hybrids, and a few samples may be from intergrade populations. P. m. austerus and P. m. artemisiae produced fertile hybrids in the laboratory, but P. oreas failed to breed. Field studies revealed that oreas and maniculatus are in part ecologically isolated in areas where both occur. Both species have more restricted habitat distri-bution in the presence of the other, and interspecific competition is suggested as a cause. Greatest reproductive activity was in spring and early summer; there was no breeding in late summer. Oreas ceased to breed earlier than maniculatus. In June adults outnumbered young of the year in the catch, but by July this was reversed. Young males were caught more often than young females, but adult females were caught more often than adult males, suggesting that females live longer than males. Oreas prob-ably developed partial reproductive isolation when separated from other Peromyscus stocks by Pleistocene glaciation. It has remained distinct from maniculatus through a combination of geographical, ecological, temporal, psychological, and genetic isolation. P U B L I C A T I O N S Sheppe, W . A . and J. R. Adams. The pathogenic effect of Trypano-soma duttoni in hosts under stress conditions. Jour. Parasit. 43: 55-59, 1957. G R A D U A T E S T U D I E S Field of Study: Mammalogy Biology of Vertebrates I. McT. Cowan Population Dynamics P. A . Larkin Terrestrial Zoogeography M . D . K Udvardy Advanced Parasitology J. R. Adams Systematic Mammalogy S. Benson Dynamics of Vertebarte Populations F. A . Pitelka Other Studies: Plant Ecology Immunology In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. Department of Zoology The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8 , Canada. Date A p r i l 8, 1958 i v . TABLE OF CONTENTS ABSTRACT page i i TABLE OF CONTENTS i v LIST OF FIGURES • v i i ACKNOWLEDGEMENT S x i A. INTRODUCTION 1 B. PROCEDURE 4 C. SYSTEMATIC RELATIONS I . VARIATION IN PEROMYSCUS 1. Sources of v a r i a t i o n 6 2 . Method of aging 8 3 . Taxonomic characters 11 a. Body len g t h 13 b. Weight 19 c. T a i l length 19 d. B i v a r i a t e a n a l y s i s — t a i l length/body l e n g t h 24 e. Hind f o o t l e n g t h 32 f . E a r leng t h 37 g. Pelage characters 37 h. S k u l l , characters 40 i . Baculum 41 I I . .ANALYSIS OF POPULATIONS 43 oreas and gambeli 45 2 . oreas and art e m i s i a e 52 3. oreas and austerus 4 . oreas and macrorhinus 5« gambeli and austerus 6 . gambeli and artemisiae 7. artemisiae and austerus 8 . artemisiae and macrorhinus 9 . austerus and macrorhinus I I I . EXPERIMENT AL HYBRIDIZATION IV. DISCUSSION OF SYSTEMATIC RELATIONS D. ECOLOGICAL RELATIONS I. REGIONAL ENVIRONMENT 1. Topography 2. Climate 3. B i o t i c areas I I . HABITAT RELATIONS oreas and gambeli 2. oreas and artemisiae 3. oreas and austerus I I I . MAMMALIAN ASSOCIATES IV. DISCUSSION OF ECOLOGICAL RELATIONS E. DISTRIBUTIONAL AND EVOLUTIONARY HISTORY F. LIFE HISTORY I . REPRODUCTION 1. Breeding season 2. Age at m a t u r i t y 181 3 . L i t t e r s i z e 182 I I . POPULATION STRUCTURE 182 1. Age composition 182 2 . Sex r a t i o 183 I I I . BEHAVIOUR 186 G. DISCUSSION 190 H. SUMMARY 199 APPENDICES Appendix 1 . E x t e r n a l dimensions of f i v e races of Peromyscus* 202 Appendix 2 . L o c a t i o n of s t a t i o n s and source of m a t e r i a l s . 203 Appendix 3 . S t a t i s t i c a l methods. 214 Appendix 4 . S c i e n t i f i c names of p l a n t s r e f e r r e d t o i n t e x t . 215 LITERATURE CITED 217 T i l . F i g . LIST OF FIGURES 1 . Age and sex v a r i a t i o n i n body length, of P. oreas. 14 2 . Age and sex v a r i a t i o n i n body l e n g t h of P. m. a r t e m i s i a e . 15 3 . Age and sex v a r i a t i o n i n body len g t h of P. m. austerus. 15 4 . Body length of f i v e races of Peromyscus. 17 5 . Body length of P. oreas from v a r i o u s l o c a l i t i e s . 18 6. Body l e n g t h of P. m. a r t e m i s i a e from va r i o u s l o c a l i t i e s . 18 7. Body len g t h of P. m. austerus from va r i o u s l o c a l i t i e s . 18 8. Body length of P. m. macrorhinus from v a r i o u s l o c a l i t i e s . 18 9. Age and sex v a r i a t i o n i n t a i l l e n g t h of P. oreas. 20 1 0 . Age and sex v a r i a t i o n i n t a i l l e n g t h of P. m. a r t e m i s i a e . 21 1 1 . Age and sex v a r i a t i o n i n t a i l l e ngth of P. m. austerus. 21 1 2 . T a i l l e n g t h of f i v e races of Peromyscus. 22 1 3 . T a i l l ength of P. oreas from various l o c a l i t i e s 23 1 4 . T a i l l e n g t h of P. m. a r t e m i s i a e from va r i o u s l o c a l i t i e s 23 1 5 . T a i l l ength of P. m. austerus from va r i o u s l o c a l i t i e s 23 16. T a i l l e n g t h of P. m. macrorhinus from v a r i o u s l o c a l i t i e s 23 v i i i . F i g . 1 7 . Equal frequency e l l i p s e s ( t a i l l e n g t h / body length) f o r samples of P. oreas and P. m. a r t e m i s i a e . 26 18. Composite equal frequency e l l i p s e s ( t a i l length/body length) f o r f i v e races of Peromyscus. 28 19. Age and sex v a r i a t i o n i n hind f o o t l e n g t h of P. oreas. 33 2 0 . Age and sex v a r i a t i o n i n hind f o o t length of P. m. a r t e m i s i a e . 34 2 1 . Age and sex v a r i a t i o n i n hind f o o t l e n g t h of P. m. austerus. 34 2 2 . Hind f o o t l e n g t h of f i v e races of Peromyscus. 35 2 3 . Hind f o o t l e n g t h of P. oreas from v a r i o u s l o c a l i t i e s . 36 2 4 . Hind f o o t l e n g t h of P. m. a r t e m i s i a e from various l o c a l i t i e s . 36 2 5 . Hind f o o t l e n g t h of P. m. austerus from v a r i o u s l o c a l i t i e s . 36 26. Hind f o o t l e n g t h of P. m. macrorhinus from v a r i o u s l o c a l i t i e s . 36 2 7 . S c a t t e r diagram of t a i l length/body l e n g t h data f o r Peromyscus from R i v e r Bend and Cottonwood. 49 28. S c a t t e r diagram of t a i l length/body len g t h data f o r P. oreas and P. m. gambeli from American F o r k s . 50 2 9 . S c a t t e r diagram of t a i l length/body l e n g t h data f o r Peromyscus from Pinewoods. 57 3 0 . S c a t t e r diagram of t a i l length/body l e n g t h data f o r P. oreas and P. m. ar t e m i s i a e from Wright's Ranch. 60 I X . F i g . 31. S c a t t e r diagram of t a i l length/body len g t h data f o r P. m. a r t e m i s i a e from Okanagan Lake. 62 32. S c a t t e r diagram of t a i l length/body len g t h data f o r P. oreas from Neah Bay. 68 33. S c a t t e r diagram of t a i l length/body length data f o r P. m. austerus from Vancouver, B.C. 75 34. S c a t t e r diagram of t a i l length/body l e n g t h data f o r Peromyscus from Hope. 78 35. S c a t t e r diagram of t a i l length/body l e n g t h data f o r Peromyscus from Loon Lake. 82 36. S c a t t e r diagram of t a i l length/body len g t h data f o r P. m. macrorhinus from C e n t r a l Coast. 88 37. S c a t t e r diagram of t a i l length/body len g t h data f o r Peromyscus from R i v e r s I n l e t . 88 38. Mean t a i l l e n g t h and body len g t h of Peromyscus from the Fraser-Thompson Canyon. 94 39. Line 20, C l e a r Lake. 121 40. Line 18, C l e a r Lake. 121 41. L i n e 19, C l e a r Lake. 122 42. Line 17, R i v e r Bend. 122 43. Looking south toward the r a v i n e at Wright's Ranch. 141 44. P. oreas h a b i t a t i n the ravine at Wright's Ranch. 141 45. Looking north toward P r i n c e t o n Golf ..Club. 149 X. F i g . 46. Ponderosa pine forest at Princeton 149 Golf Club. 47. Coast forest on upper Skagit River. 155 48. Breeding status of Peromyscus, May to October. 179 1. C o l l e c t i n g stations i n Washington and southern B r i t i s h Columbia. 2 . C o l l e c t i n g stations i n B r i t i s h Columbia. inside back 3. Representative l o c a l i t i e s at which cover Peromyscus oreas and P. maniculatus have been col l e c t e d i n western Washington and B r i t i s h Columbia. x i . ACKNOWLEDGEMENT S T h i s work has been made p o s s i b l e by the generous help of many persons and i n s t i t u t i o n s . Dr. I . MoT. Cowan was my f a c u l t y a d v i s o r ; he obtained f i n a n c i a l support and provided necessary f a c i l i t i e s . The work was supported i n part by the U n i v e r s i t y of B r i t i s h Columbia Research Com-mitte e and the N a t i o n a l Research C o u n c i l of Canada. P a r t of the work was done during a year spent at the Museum of Vertebrate Zoology of the U n i v e r s i t y of C a l i f o r n i a . Dr. Alden M i l l e r , the d i r e c t o r , made the f a c i l i t i e s of t h a t i n -s t i t u t i o n a v a i l a b l e to me, and Drs. Seth Benson and Frank P i t e l k a gave generously of t h e i r time and advice. The f i e l d work was made much more pleasant and pro-f i t a b l e by the h o s p i t a l i t y of l o c a l r e s i d e n t s , i n c l u d i n g Mr. and Mrs. Charles Gough, Mr. Reginald Tupper and Mr. Robert Tupper, Mr. and Mrs. Pat Wright, Mr. David F r a n c i s , Mr. Edward Borup, and Mr. and Mrs. Ch a r l e s M c N e i l . Mr. George Dibblee and Mr. Alan G i l l of the B r i t i s h Columbia Game Commission were very h e l p f u l . Mr. Robert Weeden helped w i t h some of the f i e l d work. The B r i t i s h Columbia F o r e s t S e r v i c e , the B r i t i s h Columbia Game Commission, and the U n i t e d States N a t i o n a l Park S e r v i c e provided c o l l e c t i n g permits f o r areas under t h e i r c o n t r o l . Dr. P. A. L a r k i n of the U n i v e r s i t y of B r i t i s h Columbia I n s t i t u t e of F i s h e r i e s provided e s s e n t i a l f i e l d equipment. x i i . The d i r e c t o r s of the Uni t e d States N a t i o n a l Museum, the N a t i o n a l Museum of Canada, and the B r i t i s h Columbia P r o v i n c i a l Museum l e n t many va l u a b l e specimens from t h e i r c o l l e c t i o n s . Dr. Frank Richardson of the Washington S t a t e Museum permitted me t o examine the c o l l e c t i o n s under h i s care. Dr. Donald Smith c o l l e c t e d specimens i n Manning Park at my request. Miss Mary Jackson l e n t me specimens from her c o l l e c t i o n . Mr. P i e r r e J o l i c o e u r was of great help i n planning the s t a t i s t i c a l a n a l y s i s . Dr. W. H. Mathews provided i n -formation on the recent g e o l o g i c a l h i s t o r y of the Northwest. Mr. M. T. Myres and Drs. C . C . Lindsey and J . F. S. B e n d e l l read a l l or parts of the manuscript and made many h e l p f u l suggestions. The help of a l l of the above people has been of the greatest v a l u e , and I am deeply g r a t e f u l to them. They are not r e s p o n s i b l e f o r the e r r o r s i n t h i s paper; indeed, I have p e r s i s t e d i n many of them i n s p i t e of advice t o the co n t r a r y . A. INTRODUCTION Peromyscus maniculatus (Wagner) has perhaps the g r e a t e s t geographic and environmental range of any North American mammal. I t occurs from c e n t r a l Mexico to the a r c t i c t i m b e r l i n e , being absent only from part of eastern and south-e r n United S t a t e s . W i t h i n i t s range i t Is found i n almost a l l t e r r e s t r i a l h a b i t a t s , from open p r a i r i e s to the most dense f o r e s t s . C o r r e l a t e d w i t h t h i s geographic range and h a b i t a t d i v e r s i t y Is the extent of v a r i a t i o n i n response to l o c a l environmental c o n d i t i o n s . The t o t a l range of v a r i a -t i o n i s not l a r g e , but there i s almost i n f i n i t e gradation and recombination of characters w i t h i n t h i s range. M i l l e r and K e l l o g g (1955) recognize over 60 subspecies, but t h i s does not adequately represent the amount of microgeographic d i f f e r e n t i a t i o n . The current concept of t h i s species i s e s s e n t i a l l y t h a t of Osgood (1909)> the l a s t r e v i s e r of the genus. He placed i n maniculatus a number of forms p r e v i o u s l y considered d i s t i n c t species, basing t h i s a c t i o n on t h e i r apparent i n t e r -g r a d a t i o n w i t h maniculatus. U n f o r t u n a t e l y he presented no evidence f o r such i n t e r g r a d a t i o n , and i t i s d i f f i c u l t even to determine which are the l o c a l i t i e s w i t h i n t e r g r a d e popu-l a t i o n s . One of the species reduced to s u b s p e c i f i c s t a t u s by Osgood was Peromyscus oreas Bangs. Osgood reported t h a t - 1 -2. oreas intergrad.es w i t h each of the subspecies of P. manicu-l a t u s w i t h which i t comes i n contact. L a t e r workers have g e n e r a l l y supported t h i s , again p r e s e n t i n g l i t t l e or no evidence f o r i t . However, a number of workers have r e -ported t a k i n g both oreas and the race P. m. austerus at some l o c a l i t i e s without f i n d i n g evidence of i n t e r g r a d a t i o n , while they are s a i d to intergrade i n other areas. The purpose of the present work i s to c l a r i f y the b i o l o g i c a l r e l a t i o n s between oreas and the races w i t h which i t comes i n contact. E x t e n s i v e c o l l e c t i n g was done t o de-termine more p r e c i s e l y the geographic d i s t r i b u t i o n of these forms and t o search f o r evidence of i n t e r g r a d a t i o n . B r i e f l y , the r e s u l t s show tha t oreas i s s u b s t a n t i a l l y r e p r o d u c t i v e l y i s o l a t e d from maniculatus and t h e r e f o r e deserves f u l l spe-c i f i c s t a t u s . Peromyscus oreas occurs from the eastern fo o t of the Cascade Mountains and B r i t i s h Columbia Coast Range to the P a c i f i c Ocean, from the lower Columbia R i v e r north t o R i v -ers I n l e t , B.C. Adjacent and overlapping races of P. manicu-l a t u s are: (1) P. m. austerus ( B a i r d ) , which occurs through-out much of western Washington and on the southern B r i t i s h Columbia coast west of the Coast Range summit; (2) P. m. macrorhinus (Rhoads), which occupies the northern B r i t i s h Columbia coast and extends northward i n t o A l a s k a ; (3) P. m. a r t e m i s i a e (Rhoads), which occupies a l a r g e area east of the Cascades-Coast Range from c e n t r a l ¥/ashington north to c e n t r a l 3. B r i t i s h Columbia and east t o Montana; (4) P. m. gambeli ( B a i r d ) , which occurs east of the Cascades i n southern Wash-ington and south through Oregon and C a l i f o r n i a . T r a d i t i o n a l t r i n o m i a l nomenclature i s used i n the present paper, though the author recognizes the v a l i d i t y of som e of the arguments which have been advanced against i t (Wilson and Brown 1953, Burt 1954). Each of the races of maniculatus considered here (except perhaps a r t e m i s i a e v s. gambeli) d i f f e r s from the other by a number of good charac-t e r s , these characters vary more-or-less concordantly, and the d i f f e r e n c e s between the races are much greater than be-tween populations of -one race. Almost every i n d i v i d u a l of macrorhinus, austerus, and artemisiae-gambeli could be sepa-r a t e d from the other races by a person f a m i l i a r with these forms. The P a c i f i c Northwest o f f e r s a maximum of geographic i s o l a t i o n and environmental d i f f e r e n c e s , so t h a t subspecies could be expected to be more c l e a r l y defined here than i n some areas. Throughout t h i s paper I have used the term "race" i n the general sense of "form" or "taxon", without i m p l i c a t i o n as to h i e r a r c h i c s t a t u s . The value of studi e s such as t h i s i s tw o - f o l d . F i r s t , a sound knowledge of systematic r e l a t i o n s i s a necessary pre-r e q u i s i t e to s t u d i e s i n other f i e l d s . I n the past, f a u l t y systematics has reduced the value of various museum and l a b o r -a t o r y s t u d i e s on the Peromyscus t r e a t e d here. The su b j e c t s rof such s t u d i e s have been i n c o r r e c t l y i d e n t i f i e d , and even mixed stocks have been used. Second, s t u d i e s combining systematics, 4. ecology, l i f e h i s t o r y , and d i s t r i b u t i o n a l h i s t o r y are one of the most e f f e c t i v e approaches t o the problem of how evo-l u t i o n takes p l a c e . They can provide information on how, when, and where genetic d i s c o n t i n u i t i e s a r i s e . B. PROCEDURE Approximately 33 weeks were spent i n the f i e l d d u r i n g the summers of 1955-1957. Most of t h i s time was devoted p r i m a r i l y to c o l l e c t i n g Peromyscus. Because the most v a l u -able c r i t e r i a f o r d i s t i n g u i s h i n g between the races i n ques-t i o n are those of dimensions r a t h e r than pelage, e f f o r t was concentrated on making e x t e r n a l measurements and c o l l e c t i n g s k u l l s of l a r g e numbers of i n d i v i d u a l s , while r e l a t i v e l y -few study s k i n s were made. I have c o l l e c t e d 1076 Peromyscus during the course of t h i s study. I n a d d i t i o n , I have examined the c o l l e c t i o n s of the U n i v e r s i t y of B r i t i s h Columbia Museum of Zoology, the B r i t -i s h Columbia P r o v i n c i a l Museum, the.Washington State Museum, the Museum of Vertebrate Zoology of the U n i v e r s i t y of C a l i -f o r n i a , the N a t i o n a l Museum of Canada, and the United States N a t i o n a l Museum, as w e l l as specimens i n a few p r i v a t e c o l -l e c t i o n s . The source of specimens from each l o c a l i t y i s i n d i c a t e d i n Appendix 1. A l t o g e t h e r , I have examined a p p r o x i -mately 2500 specimens during t h i s study. The primary purpose of the study was to determine the nature of the r e l a t i o n s between neighboring r a c e s , i . e . t o determine whether they i n t e r g r a d e , h y b r i d i z e , or do not i n t e r -5. breed at a l l . Because of t h i s , the main method of a n a l y s i s has been to attempt the p o s i t i v e i d e n t i f i c a t i o n of each specimen. S t a t i s t i c a l a n a l y s i s of whole samples has been used as a supplement to i n d i v i d u a l i d e n t i f i c a t i o n . Some a t t e n t i o n has a l s o been p a i d to geographic v a r i a t i o n w i t h i n each r a c e . A l a b o r a t o r y colony of oreas, austerus, and artemisiae has been kept f o r s i x months to determine the a b i l i t y of these races to i n t e r b r e e d . During the f i e l d work s p e c i a l a t t e n t i o n was paid to the h a b i t a t s i n which the mice were found. The h a b i t a t d i s -t r i b u t i o n of these races i s described i n S e c t i o n D, and the p o s s i b l e reasons f o r t h i s d i s t r i b u t i o n are considered. The e v o l u t i o n a r y h i s t o r y of these races i s discussed i n S e c t i o n E, i n the l i g h t of t h e i r systematic status and d i s t r i b u t i o n , and the geologic h i s t o r y of the r e g i o n . I n S e c t i o n F f i e l d and l a b o r a t o r y data o n l l i f e h i s t o r y , gathered i n c i d e n t a l l y t o the main purpose of the study, are examined f o r i n f o r m a t i o n on r e p r o d u c t i o n , p o p u l a t i o n s t r u c -t u r e , and behaviour. 6. C . SYSTEMATIC RELATIONS I . VARIATION IN Peromyscus 1. Sources of v a r i a t i o n The p r i n c i p a l sources of sample v a r i a t i o n are e r r o r s of measurement, d i f f e r e n c e s w i t h i n p o p u l a t i o n s , and d i f f e r -ences between p o p u l a t i o n s . Only the l a s t g r o u p — d i f f e r e n c e s between p o p u l a t i o n s — a r e of taxonomic s i g n i f i c a n c e , and other sources of v a r i a t i o n must be estimated before popu-l a t i o n d i f f e r e n c e s can be s t u d i e d . The most u s e f u l systematic characters i n the races under study are the standard measurements of e x t e r n a l d i -mensions taken by c o l l e c t o r s i n the f i e l d — t o t a l l e n g t h , t a i l l e n g t h , and hind f o o t l e n g t h . A l l these dimensions are subject to s i g n i f i c a n t e r r o r s of measurement. D i f f e r e n t workers use s l i g h t l y d i f f e r e n t techniques of measurement and t h e i r data are not e n t i r e l y comparable. T h i s i s i n d i c a t e d by the f a c t t h a t data c o l l e c t e d by one worker u s u a l l y show l e s s v a r i a b i l i t y than do the pooled data of many workers. Mice c o l l e c t e d i n a c r i t i c a l area by one worker showed mixed r a c i a l characters and were o r i g i n a l l y thought to be p o s s i b l e i n t e r g r a d e s . L a t e r i t was found t h a t t h i s c o l l e c t o r ' s measurements of hind foot l e n g t h were c o n s i s -t e n t l y 2-3 mm. s h o r t e r than those of other c o l l e c t o r s . Undoubtedly t h i s type of er r o r i s common but unrecognized i n the a v a i l a b l e data. I t presumably i s at a minimum i n the c o l l e c t i o n s of any one experienced worker. At the s t a r t of the present study I was i n the process of s t a n d a r d i z i n g 7. my own techniques, and t h e r e f o r e not a l l my data are f u l l y comparable. There i s a c e r t a i n amount of i n d i v i d u a l v a r i a t i o n w i t h i n every p o p u l a t i o n . I f the po p u l a t i o n i s to be char-a c t e r i z e d s t a t i s t i c a l l y the sample must r e f l e c t the v a r i a t i o n present, that i s i t must be unbiased and s u f f i c i e n t l y l a r g e . I d e a l l y , a l l animals trapped should be c o l l e c t e d . T h i s would e l i m i n a t e b i a s by the c o l l e c t o r , but would not e l i m i -nate t h a t caused by d i f f e r e n t t r a p s u s c e p t i b i l i t y of d i f f e r -ent elements of the po p u l a t i o n . When two species are pre-sent i n a l o c a l i t y and have somewhat d i f f e r e n t h a b i t a t d i s -t r i b u t i o n s i t i s not p o s s i b l e t o sample them i d e n t i c a l l y . T h i s does not a f f e c t systematic a n a l y s i s , because each species i s t r e a t e d s e p a r a t e l y . Most c o l l e c t o r s preserve o n l y the best specimens a v a i l a b l e , u s u a l l y f u l l a d u l t s considered to be i n good c o n d i t i o n . The age composition of the catch v a r i e s from mostly a d u l t s i n s p r i n g to mostly young of the year i n l a t e summer, and samples from d i f f e r e n t l o c a l i t i e s c o l l e c t e d at d i f f e r e n t seasons w i l l r e f l e c t t h i s . Some workers seem to s e l e c t mostly males f o r p r e s e r v a t i o n . Such sources of bias can be l a r g e l y discounted i f sexes and age groups are con-sid e r e d s e p a r a t e l y . Age composition o f t e n can be ignored i f b i v a r i a t e a n a l y s i s i s used. The causes of geographic v a r i a t i o n w i l l be discussed i n a l a t e r s e c t i o n . 8. 2. Method of aging Fundamental t o any u n i v a r i a t e a n a l y s i s f o r systematic purposes i s the establishment of s a t i s f a c t o r y age c r i t e r i a , so that comparisons may be r e s t r i c t e d to i n d i v i d u a l s i n a s i m i l a r s t a t e of development. Two c r i t e r i a are commonly a p p l i e d t o Peromyscus—pelage c o l o r and degree of t o o t h wear. There are three p r i n c i p a l p e l a g e s — j u v e n a l , post-j u v e n a l , and a d u l t . The juvenal pelage, acquired s h o r t l y a f t e r b i r t h , i s of a uniform dark gray c o l o r . Between the f o u r t h and eigh t h weeks of age i t i s replaced by the post-j u v e n a l , which i s predominantly brown but w i t h a strong g r a y i s h c a s t . When the i n d i v i d u a l i s s i x to seven months o l d t h i s pelage i s replaced by the more r i c h l y c o l o r e d a d u l t pelage. A f t e r t h i s no major change i n c o l o r occurs d u r i n g the l i f e of the animal. There i s a s i n g l e y e a r l y molt, u s u a l l y o c c u r r i n g i n the f a l l . T h i s account of pelages i s drawn l a r g e l y from C o l l i n s (1923). There i s i n d i v i d u a l v a r i a t i o n i n the number and t i m i n g of molts, and perhaps r a c i a l and geographic v a r i a t i o n , but the general sequence o u t l i n e d above a p p l i e s to a l l forms. Because molt i s complex and u s u a l l y takes weeks f o r com-p l e t i o n i t f r e q u e n t l y i s not p o s s i b l e to a s s i g n an i n d i v i -d ual to a p r e c i s e age c l a s s on thns b a s i s . Some f i e l d ex-perience i s necessary before post-juvenals can be d i s t i n -guished from juvenals and a d u l t s with any degree of accuracy. Each race has d i f f e r e n t pelage c h a r a c t e r i s t i c s and must be t r e a t e d d i f f e r e n t l y . F i n a l l y , some r a c i a l d i f f e r e n c e s tend t o p a r a l l e l age d i f f e r e n c e s , making aging more d i f f i c u l t where the races occur together. For these reasons, I have r a r e l y used pelage characters i n aging specimens. The degree of wear on the cheek t e e t h provides a more s a t i s f a c t o r y means of aging Peromyscus than does pelage. The amount of wear undoubtedly v a r i e s w i t h the i n d i v i d u a l , and absolute age determinations cannot be made, but a s s i g n -ment to a general age group u s u a l l y can be made with some confidence. I have found i t convenient to recognize f i v e age groups based on t o o t h wear, s i m i l a r to those of H o f f -meister (1951). My groups, from youngest t o o l d e s t , are: (1) M3 ( t h i r d upper molar) not f u l l y erupted; (2) M3 f u l l y erupted but showing l i t t l e or no wear; (3) M3 basined but cusps s t i l l apparent, Ml and M2 showing appreciable wear but cusps s t i l l prominent; (4) a l l molars basined, cusps of M3 worn away, cusps of M l and M2 g r e a t l y worn but r e -entrant angles s t i l l apparent; (5) cusps and re-entrant angles of M l and M2 almost e n t i r e l y worn away, r o o t s u s u a l l y p r o t r u d i n g w e l l beyond the a l v e o l u s . Group 1 represents the e a r l y juvenal stage. Group 2 i s entered while the animal i s s t i l l i n juvenal pelage, and i s maintained throughout the f i r s t summer, corresponding roughly to the p e r i o d of the post-juvenal pelage. Group 3 animals c o l l e c t e d during the summer apparently were born the previous year. T h i s i s based on three kinds of evidence: (1) In c o l l e c t i o n s made during the summer 1 0 . groups 2 and 3 can be r e a d i l y d i s t i n g u i s h e d , while mice k i l l e d i n winter o f t e n are intermediate between these groups. (2) Mice i n group 3 average d i s t i n c t l y l a r g e r than those i n group 2, while there i s l i t t l e d i f f e r e n c e between groups 3 , 4 , and 5 . ( 3 ) The p r o p o r t i o n of group 2 in~the catch increased from spring; to l a t e summer, while the p r o p o r t i o n of group 3 decreased. I n June group 3 outnumbered group 2 (40% of the catch, vs. 29%), but by August group 2 was more than seven times as numerous as group 3 (71% v s . 1 0 % ) . The great r i s e i n r e l a t i v e abundance of group 2 animals undoubt-edly was a r e s u l t of increment of i n d i v i d u a l s born e a r l i e r i n the same summer. The r e l a t i v e drop i n group 3 can be explained p a r t l y by the d i l u t i o n of the sample by group 2 animals. F i e l d experience s t r o n g l y i n d i c a t e s , though, th a t group 3 animals are indeed a b s o l u t e l y much l e s s abundant i n l a t e summer. T h i s presumably r e s u l t s l a r g e l y from m o r t a l i t y , but a l s o p a r t l y from t h e i r advancing i n t o group 4 . L i m i t e d data suggest t h a t some mice born i n the s p r i n g enter group 3 as e a r l y as September. Groups 4 and 5 cannot r e a d i l y be i n t e r p r e t e d i n terras of absolute age. Group 5 animals must be at l e a s t two years o l d . Peromyscus have been kept i n c a p t i v i t y u n t i l they died of " o l d age" when over seven years o l d (Dice 1 9 3 6 ) . Some f i e l d - c a u g h t specimens that I have examined have had molars worn almost to the r o o t s . I t i s d i f f i c u l t to see how these animals could have fed f o r even another year. 11. There i s no apparent d i f f e r e n c e between the sexes or the races i n the stages of t o o t h wear and t h e i r seasonal occurrence. Some i n d i v i d u a l v a r i a t i o n i n p a t t e r n of wear occurs, but seldom enough to make aging on t h i s basis i m p o s s i b l e . Groupings must always be i n t e r p r e t e d w i t h season of capture i n mind. W i t h i n broad l i m i t s , t h i s method of age grouping has proven of r e a l value i n studying age v a r i a t i o n . 3 . Taxonomic characters I n t h i s s e c t i o n each of the taxonomic c h a r a c t e r s w i l l be examined s e p a r a t e l y f o r age, sex, i n d i v i d u a l , and geo-graphic v a r i a t i o n i n each race. A n a l y s i s has been based on the l a r g e s t a v a i l a b l e samples of p o s i t i v e l y i d e n t i f i e d animals. Some samples too sm a l l f o r i n d i v i d u a l a n a l y s i s have been pooled. The l o c a t i o n of the c o l l e c t i n g s t a t i o n s i s shown i n Maps 1 and 2; numbers i n parentheses r e f e r to the key numbers on these maps. The samples considered here are: oreas American Forks ( 1 7 ) — e a s t e r n side of Cascades i n c e n t r a l Washington. C r y s t a l S p r i n g s — i n c l u d e s C r y s t a l Springs (21) and Pleasant V a l l e y (18) samples, from north and west of American F o r k s . G o o d f e l l o w — i n c l u d e s Goodfellow Creek (40) and Copper Creek (41) samples, from the eastern side of the Cascades i n southern B r i t i s h Columbia. Wright's ( 4 3 ) — n o r t h of Goodfellow. D e n n y — i n c l u d e s Denny Creek (112), Twin Creeks (111), and La Wis Wis (95) samples, from the western side of the Cascades i n c e n t r a l Washington. Neah 12. Bay ( 7 6 ) — n o r t h w e s t corner of the Olympic P e n i n s u l a . K i n g -come ( 1 6 1 ) — c e n t r a l B r i t i s h Columbia coast; t h i s sample was not included i n the t o t a l s . a r t e misiae G-oodfellow—as above. W r i g h t ' s — a s above. Okanagan ( 4 5 ) — s o u t h e r n B r i t i s h Columbia east of 'Wright's. Anahim ( 1 6 6 ) — c e n t r a l B r i t i s h Columbia east of the Coast Range. gambeli Only one sample of t h i s race i s analyzed here. I t i s composed of mice from American F o r k s , R i v e r Bend (14), and Cottonwood (15), a l l on the eastern side of the Cascades i n c e n t r a l Washington. austerus Puget Sound—from S e a t t l e (107), Kent (105), North Bend, A r i e t t a (82), P u y a l l u p (103), Tacoma (100), and Steilacoom (99), i n K i n g and P i e r c e counties i n the Puget Sound r e g i o n of Washington. Vancouver (127)--extreme south-western B r i t i s h Columbia. C u l t u s — f r o m C u l t u s Lake (129) and Robertson's (130), on the southern edge of the F r a s e r D e l t a at the f o o t of the Cascades. B. C. C o a s t — f r o m Lund (150), Bute I n l e t (151), and Loughborough I n l e t (152), on the coast north of Vancouver. macrorhinus C e n t r a l C o a s t — f r o m Koeye R i v e r (157), Beaver S e i n i n g Grounds (I56), Tom Bay (155), Kynoch I n l e t (154), and Lowe I n l e t (153) on the c e n t r a l B r i t i s h Columbia coast; t h i s i s the o n l y sample i n c l u d e d i n the t o t a l s . Neekas ( 1 5 8 ) — c e n t r a l B r i t i s h Columbia coast. Eutsuk ( 1 7 0 ) — from Eutsuk Lake i n we s t - c e n t r a l B r i t i s h Columbia east of 13. the Coast Range. S t i k i n e ( 1 7 1 ) — f r o m the S t i k i n e R i v e r i n northern B r i t i s h Columbia. a. Body l e n g t h Body l e n g t h i s sometimes of systema-t i c value i t s e l f , and i t serves as a measure of general body s i z e t o which other dimensions can be compared. The c o l l e c -t o r measures t o t a l l e n g t h , from t i p of nose to t i p of t a i l , and t a i l l e n g t h , from base of t a i l to t i p of t a i l . Body l e n g t h i s obtained by s u b t r a c t i n g t a i l length from t o t a l l e n g t h . T h i s derived measurement does not correspond ex-a c t l y to the r e a l l e n g t h of the body, but i t i s adequate f o r systematic purposes i f measured i n a uniform manner. The c o n d i t i o n of the body and the degree to which i t i s s t r e t c h e d during measurement i n f l u e n c e the reading appre-c i a b l y . I have measured most specimens during r i g o r m o r t i s , a f t e r r e l a x i n g the body by p u l l i n g on opposite l e g s . F r e s h l y k i l l e d mice or those which have been dead f o r some time give l a r g e r readings than those measured during t h i s p e r i o d . Pooled body length data f o r the above samples of oreas, a r t e m i s i a e , and austerus are analyzed f o r age and sex v a r i a -t i o n i n F i g u r e s 1, 2, and 3. These f i g u r e s are drawn i n the manner suggested by Hubbs and Hubbs (1953). The h o r i z o n t a l l i n e represents the range of v a r i a t i o n i n the sample and the v e r t i c a l l i n e represents the mean. The hollow r e c t a n g l e s represent one standard d e v i a t i o n on e i t h e r s i d e of the siean, while the s o l i d r e c t a n g l e s represent two standard e r r o r s of the mean on e i t h e r s i d e of the mean. Standard d e v i a t i o n and 14. ' standard e r r o r were not c a l c u l a t e d f o r samples of l e s s than 10 specimens; the number of specimens i n such samples i s i n d i c a t e d i n parentheses on the r i g h t . The range i n d i c a t e s the t o t a l amount of age v a r i a t i o n , i n d i v i d u a l v a r i a t i o n , and measurement e r r o r i n the sub-sample. The l e n g t h of the standard d e v i a t i o n blocks i s an i n d i c a t i o n of the amount of v a r i a b i l i t y i n the sample; the length of the standard e r r o r blocks i n d i c a t e s the r e l i a b i -l i t y of the mean. Hubbs and Hubbs present a means of i n t e r -p r e t i n g these f i g u r e s i n terms of s t a t i s t i c a l s i g n i f i c a n c e . Roughly, i f the standard e r r o r blocks of two samples do not. overlap the d i f f e r e n c e between the samples i s s t a t i s t i c a l l y s i g n i f i c a n t at the 0.05 l e v e l or l e s s . For present purposes the trend of the means i s as important as s t a t i s t i c a l s i g -n i f i c a n c e . oreas 3<f z% 1 • • l l 9 I (3) Id" I (6) • l l 1 1 : 1 5 0 6 0 7 0 8 0 9 0 1 0 0 B O O Y F i g u r e 1. Age and sex v a r i a t i o n i n body length of P. oreas. F i g u r e 2. Age and sex v a r i a t i o n i n body length of P. m. a r t e m i s i a e . F i g u r e 3 . Age and sex v a r i a t i o n i n body len g t h of P. m. austerus. To face page 15. 17. i d e n t i f y i n g i n d i v i d u a l specimens, but i t i s sometimes of supplementary value i n c h a r a c t e r i z i n g samples. oreas gambeli artemisiae austerus macrorhinus 7 0 8 0 9 0 100 no B O D Y F i g u r e U. Body length of f i v e races of Peromyscus. The values of samples of each race from various l o c a l i -t i e s are given i n F i g u r e s 5-8. Oreas i s remarkably uniform i n body l e n g t h throughout i t s range, seven samples showing mean d i f f e r e n c e s not exceeding 5 mm. There are no apparent geographical t r e n d s . The two samples with l a r g e s t means are the most northern and the most southern. Samples from the Olympic P e n i n s u l a , the western side of the Cascades, and the eastern s i d e of the Cascades are almost i d e n t i c a l . The macrorhinus sample from C e n t r a l Coast seems to be r e p r e s e n t a t i v e of t h i s r ace, and i s the only one i n c l u d e d i n the t o t a l s above. The sample from Neekas averages s i g -n i f i c a n t l y longer, though the l o c a l i t i e s are c l o s e together. At l e a s t part of the d i f f e r e n c e i s a r e s u l t of d i f f e r e n t age composition. The S t i k i n e and Eutsuk samples are s i m i l a r t o the C e n t r a l Coast sample i n t h i s c h a r a c t e r . F i g u r e 5. Body l e n g t h of P. oreas from v a r i o u s l o c a l i t i e s . F i g u r e 6. Body length of P. m. a r t e m i s i a e from v a r i o u s l o c a l i t i e s . F i g u r e 7. Body l e n g t h of P. m. austerus from v a r i o u s l o c a l i t i e s . F i g u r e 8. Body l e n g t h of P. m. macrorhinus from v a r i o u s l o c a l i t i e s . To face page 18. 7 0 8 0 9 0 o r e a s KIN G COME N E AH BAY DENNY WRIGHT'S G O O D F E L L O W C R Y S T A L S P R I N G S 190 11.0 A M E R I C A N F O R K S (6) a r t e m i s i a e ANAHIM O K A N A G A N WRIGHT'S G O O D F E L L O W austerus B. a C O A S T C U L T U S V A N C O U V E R P U G E T S O U N D macrorhinus STIKINE E U T S U K (5) N E E K A S C E N T R A L C O A S T 7 0 1 8 0 9 0 B O D Y IOO no 19. The three samples of austerus from the Puget Sound-F r a s e r D e l t a area are no more d i f f e r e n t from each other than could he expected from d i f f e r e n c e s i n sample composition and measurement techniques. The B. C. Coast sample, composed of mice from three l o c a l i t i e s north of Burrard I n l e t , i s much l a r g e r than the more southern samples. The three samples of arte m i s i a e from southern B r i t i s h Columbia are s i m i l a r , but the one from Anahim Lake, much f a r t h e r n o r t h , i s much l a r g e r . Only one sample of gambeli l a r g e enough to a n a l y z e . i s a v a i l a b l e . b. Weight For some purposes weight i s the best i n d i -c a t i o n of general body s i z e , but i t i s subject to i n f l u e n c e s such as amount of f a t and presence of large f e t u s e s or mam-mary glands. However, there i s f a i r l y good c o r r e l a t i o n be-tween weight and body l e n g t h , and there i s l i t t l e d i f f e r e n c e between the races i n weight at a given body l e n g t h . Weights of a d u l t s i n my c o l l e c t i o n are: N Mean Range oreas 15 22.7 16-31 gm ar t e m i s i a e 8 22.2 17-29 austerus 20 20.0 17-27 c. T a i l l ength The " t a i l l ength" used by mammalogists i s a convenient f i c t i o n , not corresponding c l o s e l y t o t r u e t a i l l e n g t h . I t excludes s e v e r a l caudal vertebrae near the tbase and inc l u d e s the s k i n over the t i p of the t a i l , but not the h a i r s at the t i p . The t a i l i s subject to a c c i d e n t a l 20. shortening which may not be n o t i c e d by the c o l l e c t o r . T a i l s which obviously have been damaged i n t h i s way can be discarded, but i n some i n d i v i d u a l s the t a i l looks as i f i t may have been damaged but the length i s approximately c o r r e c t f o r the race. I t i s e s p e c i a l l y d i f f i c u l t to i n t e r p r e t questionable measure-ments made by other workers. Age and sex v a r i a t i o n i n t a i l l e n g t h of oreas, a r t e -misiae , and austerus i s shown i n F i g u r e s 9-11. As with body l e n g t h , the greatest age d i f f e r e n c e s are between groups 1 and 2 and groups 2 and 3, though growth seems to continue s l o w l y throughout l i f e . I n four of the f i v e races s t u d i e d group 2 males have longer t a i l s than do females, and i n two 5 8 J (5) 5<f I (3) or e o s 4 d - I (9) 2 8 2 <? _ I J L_ (3) Id" I (6) f i i i • 1 1 '—~> 6 0 7 0 8 0 9^ 0 100 110 1 2 0 130 T A I L F i g u r e 9. Age and sex v a r i a t i o n i n t a i l l e n g t h of P. oreas. F i g u r e 10. Age and sex v a r i a t i o n i n t a i l l e n g t h of P. m. a r t e m i s i a e . F i g u r e 11. Age and sex v a r i a t i o n i n t a i l l e ngth of P. m. austerus. To face page 21. 5 « 5 0 6 0 7 0 8 0 TAIL —i— 9 0 110 22. of these the d i f f e r e n c e i s s i g n i f i c a n t . Adult females aver-age greater than a d u l t males (10 of Ik sub-samples, two of them s i g n i f i c a n t ) . T h i s character has proved to be the most u s e f u l one f o r d i s t i n g u i s h i n g between oreas and most of the races of maniculatus. F i g u r e 12 shows th a t the range of v a r i a t i o n of oreas does not overlap that of a r t e m i s i a e and gambeli, and overlaps that of austerus only s l i g h t l y . Oreas and oreas gdmbeli artemisiae austerus macrorhinus 6 0 7 0 8 0 9 0 100 110 120 130 T A I L F i g u r e 12. T a i l l ength of f i v e races of Peromyscus. macrorhinus are s i m i l a r i n t h i s dimension, averaging 112.92 mm. and 110.22 mm. r e s p e c t i v e l y . I n these two races.the t a i l i s always longer than the body. I n artemisiae (79.89 mm.) a n (^ gambeli (78.38 mm.) i t i s almost always s h o r t e r than the body, and i n austerus (88.72 mm.) i t may be e i t h e r longer or s h o r t e r . The seven samples of oreas (Fig.13) show l i t t l e d i f -erence i n mean t a i l l e n g t h , ranging from 109.93 mm. to 116.00 mm. The sample of macrorhinus from Heekas (Fig.16) averages much l a r g e r than the C e n t r a l Coast sample, c o r r e l a t e d with i t s g r e a t e r body s i z e . The Eutsuk sample i s s i m i l a r to the C e n t r a l F i g u r e 13. T a i l length of P. oreas from v a r i o u s l o c a l i t i e s . F i g u r e 14. T a i l l e n g t h of P. m. artemisiae from v a r i o u s l o c a l i t i e s . F i g u r e 15. T a i l length of P. m. austerus from v a r i o u s l o c a l i t i e s . F i g u r e 16. T a i l length of P. m. macrorhinus from v a r i o u s l o c a l i t i e s . To face page 23. 23. oreas K I N G C O M E N E A H B A Y D E N N Y W R I G H T ' S 60 i _ 70 I 80 90 100 i no 120 130 G O O D F E L L O W C R Y S T A L S P R I N G S A M E R I C A N F O R K S (6) artemisiae A N A H I M 0 K A N A G A N W R I G H T ' S G O O O F E L L O W austerus B. C. C O A S T C U L T U " S V A N C O U V E R P U G E T S O U N D macrorhinus S T I K I N E E U T S U K N E E K A S (5) C E N T R A L C O A S T r— 60 70 I 80 l 90 I 100 I 110 120 ISO T A I L 2 4 . Coast sample, but the S t i k i n e sample has much shorter t a i l s . Three of the austerus samples (Fig.15) have almost i d e n t i c a l mean values f o r t a i l l e n g t h , but the Cultus sample has s i g n i -f i c a n t l y longer t a i l s . There are no noteworthy d i f f e r e n c e s between the a r t e m i s i a e samples (Fig.14). d. B i v a r i a t e a n a l y s i s — t a i l length/body l e n g t h At the beginning of t h i s study i t was found t h a t s c a t t e r diagrams of t a i l length against body len g t h provide a more s a t i s f a c t o r y means of a n a l y s i s than e i t h e r dimension considered alone. The e n t i r e sample can be considered simultaneously r a t h e r than broken i n t o age groups, and d i f f e r e n c e s which p r e v i o u s l y were obscure o f t e n become c l e a r - c u t . The p o i n t s f o r each race tend to be grouped together, separate from those f o r other races. These groupings, i f the po i n t s are normally d i s t r i b u t e d , may be con v e n i e n t l y described by the equal-frequency e l l i p s e method of Defrise-Cussenhoven (1955). These e l l i p s e s are c a l c u l a t e d t o inc l u d e approximately 95$ of the points composing the sample. Samples may be more r e a d i l y compared by means of t h e i r e l l i p s e s than by the o r i -g i n a l s c a t t e r of p o i n t s . I n c a l c u l a t i n g e l l i p s e s I have used a method shown me by Mr. P i e r r e J o l i c o e u r (Appendix 3)• The e l l i p s e i s c h a r a c t e r i z e d by midpoint, length of major and minor a x i s , and slope of major a x i s (m). The mid-point i s determined by the means of the two dimensions. I t s value i s greater f o r samples composed l a r g e l y of a d u l t s than f o r those c o n t a i n i n g many young animals. The leng t h of the major a x i s r e f l e c t s the age composition of the sample; the le n g t h of the minor a x i s r e f l e c t s the degree of correlatio-n between the two dimensions. I f the c o r r e l a t i o n i s p e r f e c t a l l p o i n t s w i l l f a l l i n a l i n e and the minor a x i s w i l l equal zero, while i f there i s no c o r r e l a t i o n the points w i l l form a c i r c l e and the minor a x i s w i l l equal the major a x i s . The slope of the major a x i s shows the mathematical r e l a t i o n be-tween the two dimensions. I n the a n a l y s i s of populations ( S e c t i o n I I ) s c a t t e r diagrams of t a i l / b o d y data f o r some of the l a r g e samples are shown f i t t e d w ith equal frequency e l l i p s e s . The e l l i p s e s f o r three samples of oreas and three of ar t e m i s i a e are super-imposed i n F i g u r e 17. I n s p i t e of great d i f f e r e n c e s the e l -l i p s e s f o r the v a r i o u s samples of a race tend t o overlap broadly, the d i f f e r e n c e s between samples being i n t e r p r e t a b l e p r i m a r i l y i n terms of age composition or amount of v a r i a b i l i t y , r a t h e r than of systematic v a r i a t i o n . The oreas sample from Wright's covers a broad range of ages and t h e r e f o r e has an elongate major a x i s . The Denny and Neah Bay samples c o n s i s t l a r g e l y of a d u l t s , and thus have shor t e r major axes. A d u l t animals c h a r a c t e r i s t i c a l l y show greater v a r i a b i l i t y than young ones, and the long minor axes of these two samples and short minor a x i s of the Wright's sample can be explained on t h i s b a s i s . The ar t e m i s i a e sample from Wright's c o n s i s t s l a r g e l y of young of the year, and l i k e the oreas sample from t h i s s t a -t i o n has a much t h i n n e r e l l i p s e than do the samples c o n s i s t i n g 2 6 . F i g u r e 17. Equal frequency e l l i p s e s ( t a i l length/body length) f o r samples of P. oreas and P. m. a r t e m i s i a e . 27. l a r g e l y of a d u l t s . The l a r g e amount of v a r i a b i l i t y i n the Okanagan sample i s d i f f i c u l t . t o understand, but the higher p o s i t i o n of the Anahim e l l i p s e probably r e f l e c t s genuine geo-graphic v a r i a t i o n . These samples w i l l be discussed f u r t h e r i n the f o l l o w i n g s e c t i o n . F i g u r e 18 shows the o u t l i n e of the combined e l l i p s e s f o r each race. The oreas and a r t e m i s i a e f i g u r e s are based on the e l l i p s e s shown i n F i g u r e 17. The m a c r o r h i n u s . e l l i p s e i s that of the C e n t r a l Coast sample; the gambeli e l l i p s e i s t h a t of the R i v e r Bend sample. The austerus e l l i p s e shown here i s t h a t of the Vancouver sample, the Cultus e l l i p s e being included e n t i r e l y w i t h i n i t . Artemisiae and gambeli have s i m i l a r p o s i t i o n s on the graph, oreas i s above them, and austerus i s i n t e r m e d i a t e , as would be expected from the u n i v a r i a t e a n a l y s i s above. Macrorhinus i s on a l e v e l w i t h the adult oreas samples, but t o t h e i r r i g h t , r e f l e c t i n g the greater body length of that race. D i f f e r e n c e s i n slope are apparent f o r some of the e l l i p s e s . Huxley (1932) has shown that study o f growth i n one dimension i n r e l a t i o n to growth i n another can throw l i g h t on a v a r i e t y of b i o l o g i c a l problems. His a l l o m e t r i c growth formula, y = bx , has been found to give a good f i t to many sets of growth data, though the value of "a" may change once or more during growth. I t can be a p p l i e d to both s t r a i g h t -l i n e and c u r v i l i n e a r data. Most r e l a t i v e growth l i n e s are curved during the period of r a p i d growth, but l a t e r become almost, s t r a i g h t . When the 5 0 I I I l ' ' ' 5 0 6 0 7 0 8 0 9 0 100 110 BODY F i g u r e 18. Composite equal frequency e l l i p s e s ( t a i l l e n g t h / "body length) f o r f i v e races of Peromyscus. 29. observed data come only from the per i o d of s t r a i g h t - l i n e growth an a r i t h m e t i c v e r s i o n of the above growth formula can be used: y = b / ax. "y" i s the dependent v a r i a b l e , "i" the independent v a r i a b l e , "b" the value of "y" when x = 1, and "a" a constant r e p r e s e n t i n g the growth r a t e of "y" r e l a t i v e t o t h a t of "x". When a = 1, "x" and "y" are growing at the same r a t e ; when a> 1, "y" i s growing f a s t e r than n x " ; when a< 1, "x" i s growing f a s t e r than "y".. T h i s formula has the advantage that i t can be c a l c u l a t e d from the o r i g i n a l data, r a t h e r than from logarithms. I f c o r r e l a t i o n i s p e r f e c t only one l i n e can be drawn connecting the p o i n t s and only one slope (the r e l a t i v e growth constant "a") i s p o s s i b l e . When the c o r r e l a t i o n i s l e s s than p e r f e c t many l i n e s can be drawn to show the trend of the s c a t -t e r of p o i n t s . The poorer the c o r r e l a t i o n the l e s s r e l i a b l e i s any value of "a" and the more divergent are the values c a l c u l a t e d according to d i f f e r e n t formulas. The major a x i s of the equal frequency e l l i p s e i s one growth l i n e . I t i s not e n t i r e l y s a t i s f a c t o r y because i t i s d i f f i c u l t to compute, and the value of "a" depends on the s c a l e used. The t r e n d l i n e most f r e q u e n t l y used i s the r e -g r e s s i o n l i n e . I t i s e a s i l y computed and i s independent of s c a l e , but i t assumes th a t one dimension i s e n t i r e l y dependent on the other and t h i s i s seldom b i o l o g i c a l l y t r u e . Two d i f -f e r e n t l i n e s can be obtained from the same d a t a — r e g r e s s i o n of "y" on "x" and r e g r e s s i o n of "x" on "y". 30. The "standard major a x i s " of T e s s i e r and Haldane (see Imbrie 1956) i n contrast makes no assumption of dependence and independence and thus i s b i o l o g i c a l l y p r e f e r a b l e to r e -g r e s s i o n . The value of t h i s l i n e f a l l s between those of the two. r e g r e s s i o n l i n e s . I t s slope i s the r a t i o of the standard d e v i a t i o n s of the two v a r i a b l e s (S^/S^). The l i n e i s com-puted from the formula: y = y / Sy (x - x) , which i s de-Sx" r i v e d from the a r i t h m e t i c growth formula given above. A number of s t u d i e s have shown t h a t r e l a t i v e growth constants may be of systematic value. Green (1933) showed t h a t the constants f o r v a r i o u s p a i r s of s k u l l dimensions are s i g n i f i c a n t l y d i f f e r e n t i n the c l o s e l y r e l a t e d species Mus musculus and M. ba c t r i a n u s . Lumer and S c h u l t z (1941) found that the subgenera o'f Macaca are c h a r a c t e r i z e d by d i s -t i n c t i v e r e l a t i v e growth constants f o r limbs and t a i l . Growth constants ( t a i l length/body length) f o r s e v e r a l samples of Peromyscus are l i s t e d i n Table I . Slopes f o r both the major a x i s of the equal frequency e l l i p s e (m) and the standard major a x i s (a) are given. I t w i l l be seen t h a t the l a t t e r value i s always c l o s e r t o 1, that i s that the standard major a x i s i n d i c a t e s l e s s a l l o m e t r y than does the a x i s of the e l l i p s e , "m" and "a" are i n the same order i n the s e r i e s of samples except f o r the Wright's and Denny samples of oreas, where they are transposed. 31. Table I . Growth constants of t a i l length on body l e n g t h f o r samples of Peromyscus. Race L o c a l i t y m a oreas Wright's 1.520 I.466 Denny 1.767 1.357 Neah Bay 1.953 1.273 gambeli R i v e r Bend 1.289 1.142 artemisiae Wright's 1.117 1.089 Okanagan 0.729 0.882 Anahim 0.892 0.970 austerus Vancouver 1.198 1.1.18 Cu l t u s 1.048 1.023 macrorhinus C e n t r a l Coast 1.022 1.013 The values f o r a l l samples of oreas, computed by both methods, are higher than the corresponding value f o r manicu-l a t u s . A l l samples of maniculatus have growth constants l e s s than 1.15; a l l samples of oreas have constants greater than 1.25 (by the standard major a x i s formula). The r e l a t i v e l y long t a i l of oreas r e s u l t s from i t s f a s t e r r a t e of growth i n r e l a t i o n t o the body. There are no co n s i s t e n t d i f f e r e n c e s i n the growth constants of the races of maniculatus. i n s p i t e of a l l the v a r i e t y of s i z e and p r o p o r t i o n which they e x h i b i t . The s i g n i f i c a n c e of the d i f f e r e n c e s between samples i s not at a l l c l e a r . None of the a v a i l a b l e samples i s e n t i r e l y 32. s a t i s f a c t o r y f o r such a n a l y s i s and few of those i n the museums are at a l l s u i t a b l e . The samples on which the computations are based are not uniform i n composition. I n some of them v a r i a b i l i t y i s so great and the range- of growth i n c l u d e d i s so s l i g h t t h a t the constants are not very r e l i a b l e . The s c a t t e r of points diagrams do not show any d i s -c e r n i b l e curvature, but i n each of the races f o r which growth constants have been c a l c u l a t e d f o r more than one sample these constants are highest i n the sample w i t h the highest propor-t i o n of young animals. T h i s suggests that the r e l a t i v e growth of t a i l on body i s greater In young animals than i n a d u l t s . T h i s d i f f e r e n c e probably i s not great enough to ob-v i a t e the use of the a r i t h m e t i c growth formula, but i t i s best to compare samples of s i m i l a r age composition. Two of the samples of a r t e m i s i a e have growth constants of l e s s than 1, i n d i c a t i n g that the body grows at a f a s t e r r a t e than the t a i l over the observed range of v a r i a t i o n . These samples c o n s i s t l a r g e l y of a d u l t s . O f the races of maniculatus, austerus has the highest t a i l / b o d y r a t i o and would be expected to have the highest r e l a t i v e growth r a t e . I nstead, the sample of gambeli has a higher r a t e than e i t h e r austerus sample and one artemisiae sample has a higher r a t e than one austerus sample. T h i s too seems to be c o r r e l a t e d w i t h d i f f e r e n c e s i n age composition of the samples. e. Hind f o o t l e n g t h T h i s dimension Is measured from the back of the h e e l t o the end of the longest claw. I t i s 3 3 . subject t o smaller e r r o r s of measurement than the other ex-t e r n a l dimensions, but an e r r o r of even one m i l l i m e t e r may be m i s l e a d i n g . F i g u r e s 19-21 analyze age and sex v a r i a t i o n i n oreas, a r t e m i s i a e , and austerus. The hind f o o t has a t -t a i n e d almost f u l l a d u l t s i z e i n group 2 animals, and there i s l i t t l e or no growth i n the o l d e r groups. Males c o n s i s -t e n t l y average longer hind f e e t , except i n one sub-sample where the sexes are almost equal. There are 19 sub-samples of groups 2-5 f o r the f i v e r a c e s . With males greater i n 18 of them the d i f f e r e n c e i s s t a t i s t i c a l l y s i g n i f i c a n t at l e s s than the 1<?0 l e v e l (Dixon and Mood 1946). 5 i | (5) oreas 5o» I (3) « 8 4o* I (9) 3<r C = = S ^ B = I 28 i i 2 d> i I 18 . I (3) I d> I (6) \% £5 IT. Iz li iS 2s HINO FOOT F i g u r e 19. Age and sex v a r i a t i o n i n hind f o o t length of P. oreas. F i g u r e 20. Age and sex v a r i a t i o n i n hind f o o t length of P. m. a r t e m i s i a e . F i g u r e 21. Age and sex v a r i a t i o n i n hind f o o t l e n g t h of P. m. austerus. To face page 3 4 . 34. artemisiae 5 $ 1 (6) • f —I 14) i J* x (I) 16 19 15 zi I3 HIND FOOT 35. Hind f o o t lengths f o r a d u l t s of each race are shown i n Fig u r e 22. The range and means of hind f o o t length of oreas and macrorhinus are almost i d e n t i c a l , while the other races have means 2i-3 mm. lower. I n my c o l l e c t i o n almost a l l oreas have hind f e e t more than 22 mm. long and almost a l l austerus, a r t e m i s i a e , and gambeli have hind f e e t s h o r t e r than t h i s . T h i s dimension i s one of the most valuable characters f o r separating oreas from maniculatus (except macrorhinus). oreas macrorhinus 18 19 2 0 21 2 2 2 3 2 4 2 5 , H I N D F O O T , F i g u r e 22. Hind f o o t length of f i v e races of Peromyscus. I n seven samples of oreas mean hind foot length covers a range of about 1 mm., but there are no apparent geographic trends (Fig.23) . The Neekas sample of macrorhinus i s s i g n i -f i c a n t l y g r e a t e r i n t h i s dimension than the C e n t r a l Coast sample (24.05 mm. vs. 23.30 mm.), and the Eutsuk Lake and S t i k i n e R i v e r samples are s i g n i f i c a n t l y lower (22.40 mm. and 22.68 mm.)(Fig.26). The three samples of austerus from south of Burrard I n l e t are almost i d e n t i c a l , but the one from north of there i s s i g n i f i c a n t l y g r e a t e r (Fig.25) . None of F i g u r e 23. Hind f o o t length of P. oreas from v a r i o u s l o c a l i t i e s . F i g u r e 24. Hind f o o t l e n g t h of P. m. a r t e m i s i a e from various l o c a l i t i e s . F i g u r e 25. Hind foot length of P. m. austerus from v a r i o u s l o c a l i t i e s . F i g u r e 26. Hind f o o t length of P. m. macrorhinus from v a r i o u s l o c a l i t i e s . To f a c e page 36. 36. I * i Ci. 2 3 2 4 2 5 1 1 • 1 1 oreas K IN G C O M E N E A H B A Y D E N N Y W R I G H T ' S G O O D F E L L O W C R Y S T A L S P R I N G S A M E R I C A N F O R K S (6) artemi s iae A N A H I M O K A N A G A N W R I G H T ' S G O O D F E L L O W austerus B . C . C O A S T C U L T U S V A N C O U V E R P U G E T S O U N D m a c r o r h i n u s S T I K I N E E U T S U K N E E K A S (5) C E N T R A L C O A S T I— 18 —r-19 I 2 0 21 —I— 2 2 I 2 3 2 4 H I N D F O O T 2 5 3 7 . the a r t e m i s i a e samples i s c l e a r l y d i f f e r e n t from a l l the o t h e r s , but the Anahim Lake and Okanagan samples are s i g n i -f i c a n t l y d i f f e r e n t ( 2 0 . 9 0 mm. and 2 0 . 1 2 mm.J(Fig .24). f • Ear l e n g t h P r e l i m i n a r y a n a l y s i s of ear length data showed that any d i f f e r e n c e s between the races were so s l i g h t as to be masked by the high v a r i a b i l i t y . T h i s char-a c t e r was not considered f u r t h e r . g. Pelage characters Pelage c h a r a c t e r s are of value i n d i s t i n g u i s h i n g between most of these races. Geographic, age, and i n d i v i d u a l v a r i a t i o n w i t h i n each race i s so great, though, that many i n d i v i d u a l s cannot be s a t i s f a c t o r i l y iden-t i f i e d on t h i s b a s i s alone. Four characters have proven use-f u l : (1) i n t e n s i t y of d o r s a l s t r i p e , (2) c o l o r of side s t r i p e , (3) h a i r i n e s s of t a i l , and (4) h a i r i n e s s of sole of f o o t . oreas and a r t e m i s i a e I n oreas the d o r s a l s t r i p e i s darker and more d i s t i n c t than i n a r t e m i s i a e . The s i d e s are r i c h i n c o l o r i n oreas, compared to the r a t h e r faded c o l o r of a r t e m i s i a e . The t a i l of oreas i s sparsely h a i r e d , w i t h the s k i n r e a d i l y v i s i b l e , w h i l e that of artemisiae i s densely h a i r e d , the s k i n l i t t l e i f at a l l v i s i b l e . The s o l e of the f o o t i s more densely h a i r e d i n a r t e m i s i a e than i n oreas. These races u s u a l l y can be d i s t i n g u i s h e d by means of these c h a r a c t e r s . oreas and gambeli Gambeli i s s i m i l a r i n pelage char-a c t e r s to a r t e m i s i a e . I t i s somewhat l i g h t e r and l e s s red-38. dish, i n c o l o r and seldom has a d i s t i n c t d o r s a l s t r i p e . I t u s u a l l y can be d i s t i n g u i s h e d from oreas by pelage. oreas and austerus Osgood (1909) and Dice (1949) were unable t o f i n d c o n s i s t e n t c o l o r d i f f e r e n c e s between these races. The pelage of austerus averages darker than t h a t of oreas. The d o r s a l s t r i p e c h a r a c t e r i s t i c a l l y i s b l a c k i s h i n austerus, but i n oreas i s u u s u a l l y l i t t l e darker than the s i d e s . The side s t r i p e s of austerus tend to be darker, w i t h a g r a y i s h t i n t . Oreas never shows the extreme black c o n d i t i o n of many austerus, but f u l l y a dult austerus may be j u s t as l i g h t as any oreas. Oreas from c o a s t a l s t a -t i o n s i n Yfeshington show a tendency toward the b l a c k i s h con-d i t i o n of austerus. Austerus tends to have t a i l and sole of f o o t more densely ha i r e d than oreas, but the d i f f e r e n c e i s s l i g h t and not c o n s i s t e n t . Most i n d i v i d u a l s of these races cannot be s a t i s f a c t o r i l y d i s t i n g u i s h e d by pelage c h a r a c t e r s . oreas and macrorhinus These races are almost i d e n t i c a l i n pelage c h a r a c t e r s . There may be s l i g h t average d i f f e r -ences, but these are masked by i n d i v i d u a l and geographic v a r i a b i l i t y and these characters have been of no value i n s e p a r a t i n g these two forms. Some macrorhinus from mainland s t a t i o n s on the c e n t r a l B r i t i s h Columbia coast e x h i b i t the red venter, t a i l u n i f o r m l y brown above and below, and brown d o r s a l surface of hind f o o t c h a r a c t e r i s t i c of i s l a n d populations which have been named P. m. r u b r i v e n t e r by McCabe and Cowan (1945). 3 9 . The presence of these r u b r i v e n t e r characters i n a mainland specimen i s an i n d i c a t i o n t h a t i t i s maniculatus r a t h e r than oreas. Red venter and brown undersurface of t a i l were infrequent i n the samples examined, but brown hind f o o t was more common. There seems t o be much v a r i a t i o n i n t h i s c haracter. F o r i n s t a n c e , the few macrorhinus from Eutsuk Lake, east of the Coast Range, a l l show hind f e e t w i t h a d i s t i n c t brownish c a s t , unlike the white f e e t of oreas. A l l specimens from Beaver S e i n i n g Ground, on the coast, have f e e t u n i f o r m l y brown, but i n the sample from Lowe I n l e t there are only two specimens w i t h brownish f e e t . The Neekas mice have white, brown, or mottled f e e t . white spot on t a i l Some oreas show a d i s t i n c t white spot on the d o r s a l side of the t a i l , at or near the t i p . Sometimes only the t u f t of h a i r s at the t i p i s white, but as much as 25 mm. of the t a i l may be a f f e c t e d . The frequency of t h i s character In the samples examined ranges from zero to o n e - t h i r d . I t seems to be much more common on the coast than i n the mountains. Very few specimens of maniculatus show white spot at a l l , and i n these i t u s u a l l y i s l i m i t e d to the t u f t of h a i r s at the t i p . T h i s character i s of some value i n confirming the i d e n t i f i c a t i o n of a mouse as oreas. The s k i n of some t a i l s Is brown r a t h e r than white, the d i s t r i b u t i o n and i n t e n s i t y of the pigment v a r y i n g g r e a t l y . I t may occur along much of the length of the t a i l or on s c a t -t e r e d segments; i t may be confined to the d o r s a l surface or 40. completely e n c i r c l e the t a i l . O c c a s i o n a l l y the s k i n i s pigmented beneath a d o r s a l white spot. The taxonomic s i g n i -f i c a n c e , i f any, of s k i n pigmentation i s not known. h. S k u l l characters The s k u l l provides a large num-ber of p o t e n t i a l taxonomic characters of s i z e and shape. Measurements of many dimensions can be made with more accu-racy than i s p o s s i b l e w i t h e x t e r n a l dimensions, and a l l meas-urements are made by one worker. On the other hand, the s k u l l s of mice are so small t h a t very small e r r o r s may be s i g n i f i c a n t . Measurements are made with v e r n i e r or d i a l c a l i p e r s , to 0.1 mm. Repeated, measurements of the same d i -mension u s u a l l y give r e s u l t s over a range of 0.2-0.3 mm., so that only an approximation of the true length i s p o s s i b l e . I have f a i l e d to f i n d any s k u l l character very u s e f u l f o r separating oreas from the races of maniculatus w i t h which i t comes i n contact. I t of t e n i s p o s s i b l e to i d e n t i f y by i n s p e c t i o n most of the s k u l l s i n a s e r i e s of oreas and one of the races of maniculatus. The d i f f e r e n c e s are s u b t l e , though, and f o r the most part d i f f i c u l t to describe and im-po s s i b l e to measure. I have not used t h i s approach w i t h m a t e r i a l of questionable i d e n t i t y . The s k u l l of macrorhinus i s g e n e r a l l y l a r g e r than that o f oreas, and the s k u l l s of austerus, a r t e m i s i a e , and gambeli are g e n e r a l l y s m a l l e r , but there i s more overlap than d i f f e r -e n t i a t i o n . A number of dimensions were measured on a s e r i e s of s k u l l s of oreas, a r t e m i s i a e , and austerus i n an e f f o r t t o 41. f i n d the ones which give the best s e p a r a t i o n . Most were found to be of no val u e , but two were se l e c t e d f o r f u r t h e r u s e — g r e a t e s t length ( d i s t a n c e from t i p of nasals to most p o s t e r i o r extension of o c c i p i t a l s ) and le n g t h of na s a l ( d i s - , tance from t i p of l e f t n a s a l t o i t s most p o s t e r i o r point}. Oreas s k u l l s reach a greater l e n g t h than those of a r t e -misiae and austerus (maximum 27.7 mm. vs. 26.6 mm. and 27.0 mm.), but tend t o have r e l a t i v e l y s horter n a s a l s . Gambeli s k u l l s are s i m i l a r i n leng t h to those of a r t e m i s i a e , but are intermediate between a r t e m i s i a e and oreas i n r e l a t i v e length of n a s a l , Macrorhinus s k u l l s average longer than those of oreas (maximum 29.0), but the na s a l i s of the same r e l a t i v e l ength as i n that r a c e . Length of n a s a l i s the only character that I have found to be a b s o l u t e l y or p r o p o r t i o n a t e l y greater i n a r t e m i s i a e , austerus, and gambeli than i n oreas, but the d i f f e r e n c e i s not s u f f i c i e n t l y c o n s i s t e n t to be of much value. Some macro-r h i n u s may be d i s t i n g u i s h a b l e from oreas by s k u l l l e n g t h , but t h i s i s l a r g e l y a r e f l e c t i o n of t h e i r g r e a t e r body l e n g t h . I n the po p u l a t i o n analyses s k u l l dimensions w i l l be considered only where other c r i t e r i a are not e n t i r e l y s a t i s f a c t o r y . i . Baculum T h i s s t r u c t u r e provides u s e f u l systematic c r i t e r i a i n some groups of mammals, but i t has not been widely used i n studies of Peromyscus. I n t h i s genus the baculum i s r e l a t i v e l y l a r g e , c o n s i s t i n g of a broad f l a t base and a long t h i n s h a f t , capped with a short length of c a r t i l a g e . There i s a s l i g h t d o r s o - v e n t r a l curvature of the s h a f t . I have c o l l e c t e d a few bacula of oreas, a r t e m i s i a e , and austerus. They were prepared by heating i n a double b o i l e r i n a d i l u t e s o l u t i o n of ammonia and soap. The f l e s h y part of the penis was softened by t h i s treatment, and was then removed w i t h f o r c e p s . The bacula were mounted under scotch tape on microscope s l i d e s . They were compared f o r shape and width of base, length of bone, and shape of d i s t a l c a r t i l a g e . T h i s c a r t i l a g e , however, had been removed from most of the bacula during the clea n i n g process. Measurements of l e n g t h were made w i t h d i a l c a l i p e r s , measurements of width w i t h o c u l a r micrometer under 28X m a g n i f i c a t i o n . Range and mean of length and width of these bacula are given i n Table I I . There i s broad overlap of a l l three races i n both dimensions, making these characters of l i t t l e or no systematic value. The few d i s t a l c a r t i l a g e s which were pre-served showed no v a r i a t i o n a t t r i b u t a b l e to subspecies d i f -f e r e n c e s . Table I I . Dimensions of Peromyscus bacula. (mm.) Length Width  Race N Range Mean Range Mean oreas 23 8.2-10.3 8.97 0.8-1.3 1.16 austerus 24 8.1- 9.6 8.63 1.0-1.6 1.21 art e m i s i a e 5 8.1- 9.0 8.60 1.0-1.3 1.14' 4 3 . I I . ANALYSIS OF POPULATIONS Th i s s e c t i o n i s devoted to an a n a l y s i s of the compo-s i t i o n of the sample a v a i l a b l e from each c o l l e c t i n g s t a t i o n . I t s purpose i s to define as p r e c i s e l y as p o s s i b l e the geo-graphic d i s t r i b u t i o n of each race, and to seek evidence of i n t e r g r a d a t i o n or h y b r i d i z a t i o n between the races. When the sys t e m a t i s t can c o n f i d e n t l y a s s i g n a l l h i s specimens to one taxonomic group or another he knows that he i s working w i t h d i s c r e t e e n t i t i e s , but when he f i n d s spe-cimens which are intermediate between two groups i n one or more characters he i s faced with the p o s s i b i l i t y of gene exchange by the groups. To determine the genetic h i s t o r y of a po p u l a t i o n c o n t a i n i n g int ermediate i n d i v i d u a l s the sys-t e m a t i s t should: (1) become thoroughly f a m i l i a r withthe parent types, e s p e c i a l l y with the extremes of v a r i a t i o n of a number of taxonomic characters; (2) analyze l a r g e samples from the populations c o n t a i n i n g i n t e r m e d i a t e s , paying p a r t i -c u l a r a t t e n t i o n to sample v a r i a b i l i t y and frequency of d i f -f e r e n t phenotypes; and (3) r e l a t e t h i s i n f o r m a t i o n to the present and past geographic d i s t r i b u t i o n and the biology of the groups. Intermediate i n d i v i d u a l s may a r i s e i n s e v e r a l ways without gene exchange between p o p u l a t i o n s . Apparent examples may r e s u l t from error by c o l l e c t o r , c u r a t o r , or s y s t e m a t i s t . A measurement may be made i n c o r r e c t l y , a l a b e l may be placed on the wrong specimen, or a s k u l l may be a s s o c i a t e d with the 44. wrong s k i n . Such e r r o r s can seldom he r u l e d out e n t i r e l y . Unfavorable environmental c o n d i t i o n s may r e s u l t i n s t u n t i n g . A short t a i l may r e s u l t from a mutant s h o r t - t a i l gene or from a c c i d e n t a l shortening. Two non-interbreeding popula-t i o n s may come to resemble each other through common adap-t a t i o n t o s i m i l a r environmental c a f l i t i o n s . These p o s s i b i -l i t i e s r e q u i r e t h a t c a u t i o n be used i n i n t e r p r e t i n g i n t e r -mediates i n terms of gene exchange between po p u l a t i o n s . The patterns of such gene exchange are h i g h l y v a r i e d , but two p r i n c i p a l types are r e c o g n i z e d — i n t e r g r a d a t i o n and h y b r i d i s a t i o n . These terms are fundamental to modern sys-tem a t i c s , but they are used so l o o s e l y that they are mean-i n g l e s s unless the worker e x p l a i n s j u s t what he means by them and gives the evidence on which he bases h i s conclu-s i o n s . I w i l l use these terms i n the sense of Hayr, L i n s l e y , and Usinger (1953, p. 101), who s t a t e t h a t " I n gener a l , we speak of i n t e r g r a d a t i o n when a s e r i e s of intermediate popu-l a t i o n s i s i n t e r c a l a t e d between two subspecies, each w i t h approximately the same amount of v a r i a b i l i t y as any popula-t i o n o f . e i t h e r subspecies. We speak of a l l o p a t r i c h y b r i d i -z a t i o n when the two subspecies meet i n a w e l l - d e f i n e d zone and form there a h y b r i d p o p u l a t i o n w i t h g r e a t l y increased v a r i a b i l i t y , o f t e n c o n t a i n i n g the e n t i r e spectrum of charac-t e r combinations from subspecies a to subspecies b". Thus the observed range of the characters d i s t i n g u i s h i n g the sub-45. species w i l l be s i m i l a r i n magnitude but intermediate i n p o s i t i o n i n i n t e r g r a d e p o p u l a t i o n s , but i n h y b r i d populations w i l l be much g r e a t e r , perhaps i n c l u d i n g the e n t i r e range of both subspecies. I n both cases characters r e s u l t i n g from the a c t i o n of m u l t i p l e genes w i l l u s u a l l y be intermediate i n c o n d i t i o n , but characters i n h e r i t e d i n simple Mendelian f a s h i o n w i l l show t h e i r mixed o r i g i n through recombination. The r e l a t i o n of oreas to each of the surrounding races of maniculatus w i l l now be t r e a t e d i n d e t a i l , a f t e r w h i ch the r e l a t i o n s of these races t o each other w i l l be considered b r i e f l y . The e l e v a t i o n of each s t a t i o n , the l o c a t i o n of the s t a t i o n s at which I c o l l e c t e d , and the sources of specimens are given i n Appendix 2. The d i s t r i b u t i o n of oreas and mani-culatus i s shown i n Map 3, "the Washington l o c a l i t i e s i n Map 1, and the B r i t i s h Columbia l o c a l i t i e s i n Map 2. Numbers i n parentheses i n the t e x t r e f e r to Maps 1 and 2. 1. oreas and gambeli These races meet at the eastern edge of the Cascades i n southern Washington. Osgood (1909) does not mention d i -r e c t i n t e r g r a d a t i o n between them, but says t h a t they i n t e r -grade through a r t e m i s i a e . Dalquest (1948, p.91) says that "The p a l e , s h o r t - t a i l e d desert mice (gambelii) g r a d u a l l y change to the dark, l o n g - t a i l e d subspecies, oreas, t h a t occupies the Cascade Mountains". He l i s t s no l o c a l i t i e s w i t h intermediate populations. Fox (1948) s t a t e s that these races apparently i n t e r b r e e d , but not f r e e l y , i n Skamania 4 6 . County, Washington. I n h i s samples mice t y p i c a l of the parent stocks were more p l e n t i f u l than intermediate types. The s i t u a t i o n i s complicated by the f a c t t h a t gambeli of the i n t e r i o r and austerus of the coast probably intergrade along the Columbia R i v e r ( S e c t i o n I I - 5 ) , i n t r o d u c i n g the l o n g - t a i l , d a r k - c o l o r genes of austerus i n t o the region east of the mountains. Skamania County T h i s county i s i n the southern Cas-cades of Washington, bounded on the south by the Columbia R i v e r . Oreas, gambeli, and austerus have a l l been reported from here. A few i n d i v i d u a l s from the eastern part of the county are c l e a r l y gambeli, others are c l e a r l y oreas, but s e v e r a l cannot be assigned c o n f i d e n t l y to e i t h e r race on the b a s i s of a v a i l a b l e data. These are the specimens that Fox (1948) thought to be hybrids of oreas and gambeli. Spe-cimens from the f o l l o w i n g l o c a l i t i e s are: Mosquitoe Lake, one oreas; Ice Caves ( 1 ) , two oreas, two gambeli, one ques-t i o n a b l e ; Cayuse Meadow, two oreas, one questionable; Twin Buttes ( 2 ) , two oreas, two gambeli, f i v e questionable. Ex-t e r n a l dimensions of the questionable specimens are given i n Table I I I . Bingen ( 3 ) , where Dice (1949) found Peromyscus i n t e r -mediate between austerus and gambeli, i s southeast of these s t a t i o n s , i n K l i c k i t a t County. I t i s p o s s i b l e t h a t the aus-t e r u s i n f l u e n c e has extended north i n t o the mountains from the r i v e r . T h i s may account f o r some o f the t a i l s which are 47. T a b l e I I I . E x t e r n a l dimensions of indeterminable Peromyscus from Skamania County, Wash. MVZ No. L o c a l i t y Age Group Body T a i l Foot' 87.606 Twin Buttes 4 89 9 4 22 8 7 6 0 7 » 4 9 1 100 23 8 7 6 0 8 t t 4 90 97 22 8 7 6 1 3 t t 2 72 75 19 8 7 6 1 4 f t 4 99 97 23 8 7 6 1 6 Cayuse Meadows 4 100 104 23 8 7 6 1 8 Ice Caves 4 96 1 0 1 23 'too long f o r gambeli and too short f o r oreas, but would not e x p l a i n hind f o o t measurements of 23. I t i s not p o s s i b l e t o r u l e out h y b r i d i z a t i o n as the cause of these intermediate specimens. K l i c k i t a t County i s on the Columbia R i v e r east of Skamania County. Specimens from Grand D a l l e s (4)—5, Wish-ram (5)—5, M a r y h i l l ( 6 ) — 7 , M i l l e r ' s I s l a n d — 3 , and Roose-v e l t — 2 , a l l on or near the Columbia R i v e r , are c l e a r l y gam-b e l i (maximum t a i l l e n g t h 90, maximum hind foot length 22). According to Dice (1949) Peromyscus from Bingen, on the r i v e r i n the southwestern corner of the county, are intermediate between gambeli and austerus. Two specimens from Husum (7) i n the western part of the county probably are oreas, but t h e i r t a i l s are p r o p o r t i o n a t e l y too short (age group 3, body 98, t a i l 102, hind foot 23; group 4, 100-105-23). Four specimens from T r o u t l a k e (8) are oreas, one i s gambeli, and 48. one i s probably oreas (group 2, 90-95-22). Nine specimens from Satus Pass (9) i n the n o r t h - c e n t r a l part of the county are gambeli. Yakima County i s north of K l i c k i t a t County. Specimens from Yakima (10)—4, S e l a h — 3 , and Moxee—4 , i n the north-e a s t e r n part of the county, are gambeli. Specimens from s t a t i o n s i n the eastern Cascades include one oreas from Got-chen Creek, two from Beaver Spri n g s , three from two mil e s southwest of Conrad Meadows, one from ei g h t m i l e s west of Glenwood, a l l i n the v i c i n i t y of Mt. Adams (11). There are three oreas and three gambeli from S i g n a l Peak (12), on the Yakima Indian R e s e r v a t i o n . There i s one oreas from Dog Lake (13) two miles east of the Cascade summit, two gambeli from three miles east of Dog Lake (3800 f e e t ) , and three oreas from Goose P r a i r i e . R i v e r Bend (14) and Cottonwood (15) are i n the eastern f o o t h i l l s of the Cascades. F i g u r e 27 i s a s c a t t e r diagram of t a i l length against body len g t h f o r the 19 mice from R i v e r Bend and the four from Cottonwood. An equal frequency e l l i p s e has been f i t t e d to these p o i n t s . A l l these mice are gambeli; maximum lengths are 90-90-22. C l e a r Lake i s on the east slope of the Cascades, west of R i v e r Bend. A sample of 50 mice from here includes nine gambeli, 39 oreas, and two questionable. One of these two was i n juvenal pelage, group 2, 69-75-21, s k i n not a v a i l a b l e . I t probably i s oreas. The other i s i n group 5, 98-100-23, 49. 1 0 0 • 9 0 S 8 0 7 0 o YOUNG , • AOULT -1 1 ' 1 6 0 T 5 0 6 0 7 0 8 0 9 0 1 0 0 H O B O D Y F i g u r e 27. S c a t t e r diagram of t a i l length/body length data f o r Peromyscus from R i v e r Bend and Cottonwood. pelage c o l o r and h a i r i n e s s of t a i l and f o o t l i k e oreas. I t resembles oreas i n a l l c haracters except t a i l l e n g t h . The t i p of the t a i l seems to be mi s s i n g , the end being b l u n t e r than normal and l a c k i n g the t u f t of h a i r s . T h i s mouse seems to be a good oreas. American Forks (17) T h i s s t a t i o n i s on the east slope of the Cascades, n o r t h of C l e a r Lake. T a i l and body length data f o r 59 mice from here are shown i n F i g u r e 28, w i t h the e l l i p s e s of the oreas from Wright's and the gambeli from R i v e r Bend. The gambeli i n t h i s sample are younger F i g u r e 28. S c a t t e r diagram of t a i l length/body le n g t h data f o r P. oreas and P. m. gambeli from American F o r k s . Equal frequency e l l i p s e s f o r oreas from W r i g h t 1 s and gambeli from R i v e r Bend have been superimposed. To face page 50. 50 51. than those from R i v e r Bend, and do not f i t the e l l i p s e w e l l . Only one i n d i v i d u a l i s questionable (group 4, 90-95-20). Apparently i t i s an unusually l a r g e gambeli. Pleasant V a l l e y (18) i s at 3300 f e e t , west of Ameri-can "Forks. Of 23 Peromyscus from here, a l l but one are oreas. T h i s one i s i n group 1, dimensions 78-79-22, no s k i n made. I t may be gambeli, but seems too l a r g e f o r t h a t age. Dice (1949) has taken both oreas and gambeli at Lodge-pole Camp, between Pleasant V a l l e y and Chinook Pass. K i t t i t a s County i s north of Yakima County. A sample from Easton (19)» at the eastern f o o t of the Cascades, con-s i s t s of f i v e oreas and three gambeli. A sample from the opposite side of the r i v e r near here c o n s i s t s of one oreas and s i x gambeli. Three specimens from Lake Keechelus (20) i n the Cascades west of Easton are oreas, as are 27 from C r y s t a l Springs (21). I n summary, oreas and gambeli occur together i n a zone of v a r i a b l e width on the eastern side of the Cascades. At C l e a r Lake, American F o r k s , and Easton both races were taken, with few i f any in t e r m e d i a t e s . A few specimens from Skamania County and other s i t e s i n southern Washington seem to have mixed or intermediate characters and may be h y b r i d s . There i s no evidence of r e a l i n t e r g r a d a t i o n , and h y b r i d i z a -t i o n probably i s r a r e I f i t occurs at a l l . 52. 2. oreas and arte m i s i a e Osgood conceived of ar t e n i i s i a e as "an aggregation of intermediates, but s u f f i c i e n t l y constant and r e s t r i c t e d i n range to merit r e c o g n i t i o n . . . I n a way, i t connects the long-t a i l e d and the s h o r t - t a i l e d forms of the maniculatus group... The gradation from gambeli v i a ar t e m i s i a e to oreas seems to be complete, although at c e r t a i n l o c a l i t i e s r e p r e s e n t a t i v e s of each may be found apparently p r e s e r v i n g d i s t i n c t n e s s " (1909, p.59). Elsewhere he says t h a t "Oreas appears to inter g r a d e w i t h a r c t i c u s = b o r e a l i s l , most of the i n t e r -mediate specimens having been r e f e r r e d to artemi s i a e " (1909, H i s concept of i n t e r g r a d a t i o n i s brought i n question when he says that specimens from F i e l d , G l a c i e r , , and Golden, B.C., are "approaching oreas and a r c t i c u s " (p .60). These l o c a l i t i e s are i n the eastern part of the province, hundreds of miles from the range of oreas. Presumably the specimens r e f e r r e d t o are P. m. al p i n u s Cowan, which resembles oreas i n some re s p e c t s . Osgood l i s t s 87 specimens of ar t e m i s i a e from Hope, B.C., and near Hope. T h i s l o c a l i t y i s at the western f o o t of the Cascades, f a r from the range of t h i s r a ce. Anderson (1946) and Dalquest (1948) also s t a t e that a r t e m i s i a e i n t e r g r a d e s with oreas, but do not mention spe-c i f i c l o c a l i t i e s where t h i s occurs. C a r l , Guiguet, and Hardy (1952, p.74) say that oreas "occupies the greater part P. 53). 53. [of Manning Park] , i n t e r g r a d i n g with Peromyscus m. ar t e m i s i a e (Rhoads) i n the Goodfellow? Creek area to the east where spe-cimens of both races were secured." They do not say tha t they found intermediate specimens. Washington Chelan County i s i n the eastern Cascades, north of , K i t t i t a s County. F i v e specimens i n the U. S. B i o l o g i c a l Survey c o l l e c t i o n from Wenatchee (22) i n the south-eastern corner of the county have pelage l i k e t hat of a r t e m i s i a e , but t h e i r measurements are c l o s e r to oreas ( t a i l 96-105, f o o t 22-23). Wenatchee i s on the Columbia R i v e r , m i l e s east of the nearest s u i t a b l e oreas h a b i t a t . These measure-ments probably are i n c o r r e c t . Two specimens from Chelan (23) are a r t e m i s i a e . One from Stehekin (24) i s a r t e m i s i a e (group 4, 97-84-20) and two have questionable measurements (group 3, 93-101-22^; group 3, 98-100-22). One from Lyman Lake (25) i n group 4 measures 100-105-22, the t a i l too long f o r a r t e m i s i a e and p r o p o r t i o n a t e l y too short f o r oreas. The The dimensions of three specimens from Cascade Tunnel (26) a r e — g r o u p 4, 94-98-22; Group 3, 89-108-22; group 4, 103-109-22. Of three specimens from Hart Lake (27) one i s oreas, one gambeli, and one questionable (group 4, 91-99-22). The Lyman Lake and Cascade Tunnel specimens and the questionable Hart Lake specimen resemble oreas i n pelage c h a r a c t e r s . I f the measurements are c o r r e c t some of these specimens may be oreas x artemisiae h y b r i d s . 54. Okanogan County Is north and east of Chelan County, i n the eastern Cascades and Okanogan Highlands. Specimens from the f o l l o w i n g l o w - l e v e l s t a t i o n s (2100 f e e t or l e s s ) a l l are a r t e m i s i a e : O r o v i l l e — 1 , Twisp (28) — 5, Conconully (29) — 5, Mazarna (30)—2, Loomis (31) — 3. Two specimens from Snowshoe Camp, Chopaka Mt. (32, 5700 f e e t ) and one from Bauerman Ridge (6500 f e e t ) are oreas. Whatcom County l i e s immediately west of Okanogan County, between the Cascade c r e s t and the P a c i f i c Ocean. Apparently oreas, a r t e m i s i a e , and austerus a l l occur i n the Skagit watershed i n the eastern h a l f of the county. Oreas and austerus are known to occur i n the Sk a g i t R i v e r v a l l e y at the I n t e r n a t i o n a l Boundary, 10 m i l e s west of the c r e s t . Oreas and arte m i s i a e occur together near the mouth of the Pasayten R i v e r , 10 miles east of the c r e s t and 10 m i l e s north of the Boundary. The Skagit R i v e r flows south bound-i n g the area on the west, I t s v a l l e y p r o v i d i n g a l o w - l e v e l c o r r i d o r along which austerus penetrates deep i n t o the moun-t a i n s . The Pasayten R i v e r flows north somewhat east of the c r e s t , and i n B r i t i s h Columbia at l e a s t i t s v a l l e y i s good artemisiae h a b i t a t . Two specimens from Hannegan Pass are. oreas. There are two oreas and one artemisiae from Canyon Creek (33) and one ar t e m i s i a e from Ruby Creek (34). Of two specimens from Barron (35), one i s artemisiae (group 4, 90-87-21, pelage l i k e a r t e m i s i a e ) , the other shows mixed char-a c t e r s (group 4, 93-99-21, pelage i n t e r m e d i a t e ) . T h i s county 55. i s the only area west of the Cascade c r e s t from which I have seen a r t e m i s i a e . B r i t i s h Columbia A l l i s o n Pass (36) i s on the Cascade c r e s t i n southern B r i t i s h Columbia, at 4404 f e e t . My c o l l e c t i o n i n c l u d e s 27 specimens taken w i t h i n two mile s east or west of here. A l l but one of these specimens are good oreas. The dimensions of the s i n g l e exception a r e — g r o u p 4, 89-90-23, no s k i n . T a i l length i s the only questionable c h a r a c t e r , and i t i s marked w i t h a "?" i n my f i e l d notes, suggesting that i t - may not be r e l i a b l e . Twelve specimens c o l l e c t e d by D. Smith one mile east of the pass present an a l t o g e t h e r d i f f e r e n t p i c t u r e . A few seem to be good oreas, but most of the t a i l s are 10-20 mm. too short f o r the body l e n g t h . Only one has hind f o o t length l e s s than 22. Some may be ar t e m i s i a e on the ba s i s of t a i l / body r a t i o , but are much too l a r g e f o r t h e i r age (group 2). Some of the l o n g - t a i l group have body lengths too great f o r e i t h e r race (104, 106). T h i s sample may i n c l u d e oreas x a r t -emisiae h y b r i d s , or may be explained by co n s i s t e n t e r r o r s of measurement of body length . I t seems u n l i k e l y that I could hav'e trapped i n s i m i l a r h a b i t a t s i n the same immediate area and taken only one mouse d o u b t f u l l y resembling those o f Smith. Three oreas were taken at Gibson Pass (37), south of A l l i s o n Pass. One oreas and one art e m i s i a e were taken at 56. C o l d s p r i n g Camp, fo u r m i l e s east of A l l i s o n Pass. Three specimens from T i m b e r l i n e V a l l e y (38)> northeast of Cold-s p r i n g , are oreas. Pinewoods (39) i s f i v e m i l e s east of A l l i s o n Pass, at 4000 f e e t . The e x t e r n a l measurements of the mice from here are p l o t t e d In Fi g u r e 29, with the e l l i p s e s f o r the Neah Bay oreas and the Okanagan a r t e m i s i a e . Some hind f o o t measurements i n t h i s sample are known to be i n c o r r e c t ; d i s -cordant measurements b e l i e v e d to be c o r r e c t are i n d i c a t e d i n the f i g u r e . The points form a continuous s e r i e s , from the bottom of the artemisiae e l l i p s e to the top of the oreas e l l i p s e . Most f a l l i n one of the e l l i p s e s , but they are centered i n the upper part of the arte m i s i a e e l l i p s e , the lower part of the oreas e l l i p s e , and the area between. Most of the animals w i t h i n the ar t e m i s i a e e l l i p s e were i n juvenal pelage, but t h e i r s k u l l s are not a v a i l a b l e f o r aging. Most of the animals w i t h i n the oreas e l l i p s e are a d u l t . Almost a l l of the animals c o l l e c t e d by me have measure-ments c h a r a c t e r i s t i c of oreas, while most of Smith's s p e c i -mens f a l l outside the oreas e l l i p s e . They average g r e a t e r i n body length than mine do, as at A l l i s o n Pass, while those of other workers tend to be intermediate. A continuous, almost v e r t i c a l s c a t t e r of points l i k e t h i s would be expected from two f r e e l y h y b r i d i z i n g popula-t i o n s i f the sample c o n s i s t e d e n t i r e l y of a d u l t s , but there F i g u r e 2 9 . S c a t t e r diagram of t a i l length/body l e n g t h data f o r Peromyscus from Pinewoods. E q u a l frequency e l l i p s e s f o r oreas from Neah Bay and ar t e m i s i a e from Okanagan have been superimposed. Numbers beside p o i n t s show hind f o o t l e n g t h . To face page'57. 57. 58. are many young animals i n t h i s sample that average almost as great i n body l e n g t h as the a d u l t s . Some of the p u z z l i n g f e a t u r e s of the sample may r e s u l t from c o n s i s t e n t e r r o r s of body length measurement by one or more c o l l e c t o r s , but others seem to be a t t r i b u t a b l e to h y b r i d i z a t i o n . Adult t a i l lengths range from 90 to 125 (one exce p t i o n ) , extending from the upper part of the arte m i s i a e range t o the upper part of the oreas range. Of my 15 specimens, 13 seem to be oreas and two are intermediate (group 3, 87-98-20; group 3, 81-95-21). The a v a i l a b l e skins show mixed characters and the s k u l l s are of l i t t l e v alue. Four specimens from t h i s area i n the U n i -v e r s i t y of B r i t i s h Columbia c o l l e c t i o n l a b e l l e d "oreas x arte m i s i a e " may w e l l be hybrids. One of two specimens i n t h i s c o l l e c t i o n l a b e l l e d "oreas x austerus" appears to be art e m i s i a e (group 4, 78-65-22). The other may be an oreas x artem i s i a e h y b r i d (group 3, 86-94-22). T h i s i s a confusing sample, and cannot be f u l l y i n t e r -preted at the present time. Some of the e x t e r n a l measure-ments are not c o r r e c t and others are questionable, but even a f t e r allowance i s made f o r t h i s questions s t i l l remain t o be answered. Some specimens are Intermediate between the rac e s , but there are many t y p i c a l oreas and few i f any t y p i -c a l a r t e m i s i a e . The popu l a t i o n can h a r d l y be c a l l e d t r u l y i n t e r g r a d e , but i f i t c o n s i s t s of d i s t i n c t oreas and a r t e -misiae populations and hybrids between them, where are the artemisiae? 59. Goodfellow Creek (40) i s e i g h t m i l e s northeast of Pinewoods. The sample from here i s analysed i n S e c t i o n I . I t i n c l u d e s 30 oreas, 20 a r t e m i s i a e , and one apparent i n t e r -mediate (group 4 , 88-97-21). T h i s i n d i v i d u a l may be a h y b r i d . C a r l et a l . (1952) took both races at t h i s s t a t i o n and con-cluded that they Intergrade here. My c o l l e c t i o n confirms the occurrence of both races here, but provides no evidence of i n t e r g r a d a t i o n . Copper Creek (41) i s nine m i l e s north of Goodfellow Creek. The sample from here and Sunday Summit i s i n c l u d e d i n the Goodfellow sample analysed i n S e c t i o n I . T h i r t y -nine Peromyscus w^ere taken near the mouth of the creek. T h i r t y - t h r e e of these were a r t e m i s i a e , f i v e were oreas, and one was u n c e r t a i n (group 5, 99-100 -23 ) . T h i s s t a t i o n i s east of the p r e v i o u s l y reported eastern l i m i t of oreas. E i g h t specimens from two m i l e s north of Copper Creek are a r t e m i s i a e , as i s one from Sunday Summit, three m i l e s f a r t h e r n o r t h. Two oreas and seven a r t e m i s i a e were taken at Tupper's M i l l ( 4 2 ) , between Sunday Summit and Wright's Ranch. Wright's Ranch (43) i s at 2800 f e e t , three m i l e s south-west of P r i n c e t o n . The sample from here i s analysed i n Sec-t i o n I . F i g u r e 30 shows th a t the 139 specimens from here f a l l Into d i s t i n c t l o n g - t a i l and s h o r t - t a i l groups when t a i l l e n g t h i s p l o t t e d against body l e n g t h , though they are not separable when e i t h e r dimension i s considered alone. F i g u r e 3 0 . S c a t t e r diagram of t a i l length/body l e n g t h data f o r P. oreas and P. m. a r t e m i s i a e from Wright's Ranch. Equal frequency e l l i p s e s have been f i t t e d to these data, o m i t t i n g the p o i n t s i n double c i r c l e s . To face page 60. 60. 61. These groups have been f i t t e d w ith equal frequency e l l i p s e s . S e v e r a l very young i n d i v i d u a l s are of u n c e r t a i n i d e n t i t y on t h i s b a s i s , but only one l a r g e r one i s questionable. T h i s i n d i v i d u a l i s i n age group 2 and measures 84-95-23. Appar-e n t l y i t i s an oreas w i t h t a i l s l i g h t l y s h o r t e r than I s t y p i -cal.:": T h i s i s the easternmost l o c a l i t y f o r oreas. Three artemisiae were trapped on the west bank of the Similkameen R i v e r one mile south of P r i n c e t o n . Twenty-seven were trapped at the P r i n c e t o n G o l f Club (44), on the east side of the r i v e r one mile east of P r i n c e t o n . Okanagan (45) T h i s sample c o n s i s t s of specimens from v a r i o u s l o c a l i t i e s i n the Okanagan Lake area. E i g h t y specimens from here have been stud i e d ( F i g s . 6 , 14, 24, 31). T h i s i s the most v a r i a b l e s i n g l e - r a c e sample that I have examined, although a l l measurements were made by one worker. F i v e specimens from Osoyoos (46), south of Okanagan, are a r t e m i s i a e . Treasure Mountain (47) T h i s s t a t i o n i s s i t u a t e d among low, rounded mountains i n the eastern Cascades. The sample inc l u d e s f o u r young i n d i v i d u a l s , a l l oreas, and 19 a d u l t s . F i f t e e n of the a d u l t s have t a i l s longer than 106 and f e e t 22 or longer and are c l e a r l y oreas. The other four show mixed c h a r a c t e r s . One, wi t h measurements 93-97-20, may be an unusually large a r t e m i s i a e . The others measure 89-102-21, 91-105-20, and 95-103-21, and could h a r d l y be pure a r t e -m i s i a e . These f o u r specimens were c o l l e c t e d e a r l y i n my 5 0 i • I I I , , , 5 0 GO 7 0 8 0 9 0 100 110 B O D Y Figure 31. S c a t t e r diagram of t a i l length/body le n g t h data f o r P. m. art e m i s i a e from Okanagan Lake. An equal frequency e l l i p s e has been f i t t e d to these data. f i e l d work and t h e r e f o r e the measurements may not be r e l i -a b l e . I t i s e n t i r e l y p o s s i b l e that they are oreas x a r t e -misiae h y b r i d s . E c o l o g i c a l l y the s t a t i o n i s favorable f o r the occurrence of both races. 63. Two specimens from Glimpse Lake (48} on trie southern Cariboo P l a t e a u are a r t e m i s i a e , as are 14 from Kamloops (49) f a r t h e r n o r t h . A sample from the Cascade Mountains f i v e m i l e s east of Boston Bar (50) i n c l u d e s f i v e oreas and one ad u l t a r t e - m i s i a e . I n a d d i t i o n there i s a j u v e n i l e that apparently i s a r t e m i s i a e (69-72-20) and an a d u l t that probably i s oreas (91-107-21J). Ten specimens from L y t t o n (51) on the F r a s e r R i v e r are a r t e m i s i a e . From Botanie Mountain near L y t t o n there are two ar t e m i s i a e and one po s s i b l e oreas (age un-known, 69-79-21). I have examined 11 specimens from Ash-c r o f t (52), the type l o c a l i t y of a r t e m i s i a e . A l l were mem-bers of t h i s race, the three a d u l t s measuring 94-69-21, 94-86-21, and 83-72-20. Seven specimens from L i l l o o e t (53), west of A s h c r o f t , are a r t e m i s i a e . A s m a l l sample from M c G i l l i v r a y Creek (54) near Anderson Lake i n the Coast Range shows c e r t a i n incon-gruous measurements (e.g. one body length of 116) and the data are questionable. Apparently i t contains both oreas  a n d a r t e m i s i a e , and perhaps i n t e r m e d i a t e s . Artemisiae are a v a i l a b l e from the f o l l o w i n g l o c a l i t i e s east of the Coast Range: Blackwater L a k e — 2 , Minto Mine (55)—3, B i g Bar Lake (56)—2, A l e x i s Creek (57)--6, Kleena Kleene (58)—2, Nimpo Lake (59)—2. I n summary, a r t e m i s i a e , l i k e gambeli, occurs with oreas i n a zone along the eastern side of the Cascades. Both races 64 • were found at s e v e r a l l o c a l i t i e s along the Similkameen R i v e r , but there i s evidence that extensive h y b r i d i z a t i o n may occur at other l o c a l i t i e s , notably Pinewoods. 3. oreas and austerus The r e l a t i o n of oreas to austerus has been studied more e x t e n s i v e l y than i t s r e l a t i o n to any other race, but i t has been a frequent puzzle t o s y s t e m a t i s t s . T h i s i s at l e a s t p a r t l y because austerus i s separated from oreas by l e s s d i s t i n c t i v e morphological characters than are the i n -t e r i o r r a c e s . Osgood (1909, p.52-53) commented th a t the systematic r e l a t i o n s h i p of these two forms " i s d i f f i c u l t t o understand...It i s already known t h a t oreas and austerus occur together at a number of l o c a l i t i e s and apparently maintain t h e i r r e s p e c t i v e c h a r a c t e r s . At other places only . one form has thus f a r been found, at others extremes of both forms and intermediates occur, and at s t i l l others intermediates only...Specimens which appear to be interme-d i a t e between oreas and austerus may i n r e a l its' - represent s p e c i a l d i f f e r e n t i a t i o n s of the one or the other showing a c c i d e n t a l p a r a l l e l i s m . " He l i s t s samples of both races t h a t are intermediate i n character or c o n t a i n intermediate specimens. T h i s confusion s t i l l e x i s t s , and these two forms are rep o r t e d by d i f f e r e n t workers as i n t e r g r a d i n g or not i n t e r -grading at v a r i o u s l o c a l i t i e s . T a y l o r and Shaw (1929) say 65. t h a t they apparently occur together over a wide area. Dice (1932) says that G-aige c o l l e c t e d both races at Lake Cushnian on the Olympic P e n i n s u l a , apparently without f i n d i n g i n t e r -grades. Dice himself (1949) c o l l e c t e d both races at s e v e r a l l o c a l i t i e s i n the Puget Sound r e g i o n . S v i h l a (1933) found both races occupying the same h a b i t a t on the Olympic P e n i n s u l a without i n t e r g r a d i n g . S i m i -l a r r e s u l t s are reported by Dalquest (1948, p.93), who says t h a t "these two subspecies appear not to in t e r b r e e d i n nature, since no int e r g r a d e s were taken at any of the numerous l o c a l -i t i e s i n western Washington where the mice were trapped. Pure populations of the two subspecies e x i s t w i t h i n a few mi l e s of each other." Fox (1948) b e l i e v e d that the two forms i n t e r b r e e d , but not f r e e l y , i n C l a r k and C o w l i t z Coun-t i e s . He found the parent stocks more p l e n t i f u l than i n t e r -mediates . I n t e r g r a d a t i o n between these races i n B r i t i s h Columbia has been reported by s e v e r a l workers. Anderson (1946) says t h a t on the western slopes of the Cascades east of the coas-t a l p l a i n oreas i n t e r g r a d e s w i t h austerus i n some areas. C a r l _et a l . (1952) b e l i e v e that these races may int e r g r a d e i n the Hope area, as one specimen taken there shows charac-t e r s of both r a c e s . According t o Cowan and Guiguet (1956, p.188) "there i s gradual blending between austerus and oreas between A l d e r -grove and Cultus Lake along the I n t e r n a t i o n a l Boundary and 66. up the slopes of the adjacent h i l l s . " McCabe and Cowan (1945) say that oreas and austerus occur together at Lough-borough I n l e t , apparently without i n t e r g r a d a t i o n . Washington Wahkiakum County i s on the Columbia R i v e r near i t s mouth. A sample from Cathlamet (60), on the r i v e r , i n c l u d e s o n e austerus, three oreas, and two indeterminable (group 4, 95-100-24; group 3, 93-102-22(?)). E i g h t specimens from Skamokawa (61), on the r i v e r west of Cathlamet, are oreas. P a c i f i c County i s i n the southwest corner of the s t a t e . A sample from Chinook (62), on the Columbia R i v e r , i n c l u d e s 28 oreas, one austerus (group 4, 97-92-19), and two of mixed characters (group 5, 95-97-23; group 4, 97-105-20). Three specimens from Ilwaco (63), a l s o on the r i v e r , are oreas, three are austerus, and one i s indeterminable (group 3, 92-104-22, resembles austerus i n some pelage c h a r a c t e r s ) . Two from Long Beach (64), on the ocean, are oreas. From Long I s l a n d (65), i n W i l l a p a Bay, are three oreas and one probable austerus (group 3, 90-96-22). There i s one oreas from Oys-t e r v i l l e (66), on W i l l a p a Bay, and one from South Bend (67), on the W i l l a p a R i v e r near- the bay. A sample from Tokeland (68), on the north side of the bay, includes s i x or eas and two austerus. Grays Harbor County i s on the ocean north of P a c i f i c County. Both oreas and austerus are present i n samples from 67. O a k v i l l e (69)—3 and 1, and C e d a r v i l l e — 2 and 1, east of the W i l l a p a H i l l s . From Aberdeen (70), on Grays Harbor, there are s i x oreas, one austerus (group 3, 80-92-22), and one indeterminable (group 1, 90-94-22). A l l seven specimens from Lake Q/uinault (71), at the base of the Olympic Moun-t a i n s , are oreas. C l a l l a m County forms the northern part of the Olympic P e n i n s u l a . There are 14 specimens of oreas from Lapush (72), on the ocean, and three m i l e s east of Lapush. According t o the l a b e l s the hind f e e t of s e v e r a l measured 21, too sm a l l f o r oreas, but even when dry these f e e t measure at l e a s t 22, and i t i s apparent th a t the measurements on the l a b e l s are i n c o r r e c t . These specimens and those from Neah Bay have darker d o r s a l s t r i p e than i s c h a r a c t e r i s t i c of oreas, but the measurements d e f i n i t e l y place them i n t h i s s p e c i e s . T h i s greater degree of s a t u r a t i o n , i f t r u l y c h a r a c t e r i s t i c of the pop u l a t i o n s , may r e s u l t from ada p t a t i o n to the extreme oceanic c o n d i t i o n of. these s t a t i o n s . Specimens from. Forks (73)—2, Ozette Lake (74)—1, Sooez-f6) and Solduc R i v e r (75)—1, are oreas. A c o l l e c t i o n of 34 specimens from the northwest t i p of the county at Neah Bay (76) c o n s i s t s e n t i r e l y of oreas. The e x t e r n a l measure-ments are analyzed i n F i g u r e s 5, 13, 23, and 32. S i x s p e c i -mens have a white spot on the t a i l , averaging 9 mm. long. F i v e specimens from the Elwha R i v e r (77) at the north base of the Olympic Mountains i n c l u d e two oreas, two austerus, 68. 130 -| 90 I l i i l I I 50 60 70 80 90 100 N< BODY F i g u r e 32. S c a t t e r diagram of t a i l length/body length data f o r P. oreas from Neah Bay. An equal frequency e l l i p s e has been f i t t e d to these data. and one indeterminable (group 4, 92-101-23). There are fou r oreas from near Mt. Angeles (78), south of Port Angeles. Specimens from 12 m i l e s south of Port Angeles include two> oreas, one austerus, and two of mixed characters (group 5, 103-105-20; group 5, 97-114-20). 69. A c o l l e c t i o n from Dungeness Hatchery (79) i n the eastern part of the county four m i l e s south of Sequim i n -cludes two oreas and eight austerus. T h i r t y - s i x specimens from the j u n c t i o n of the Dungeness and Greywolf R i v e r s (80) are a l l a d u l t s . They f a l l i n t o two d i s t i n c t groups on the b a s i s of t a i l / b o d y measurements. A group of s i x s h o r t - t a i l mice (body 82-87, t a i l 82-88, f o o t 20-21) i s separated by a gap of eight mm. from a group of 29 l o n g - t a i l mice (body 77-101, t a i l 97-115, f o o t 21-24). Pelage c o l o r ranges from very dark to very l i g h t , but shows no c o r r e l a t i o n with other c h a r a c t e r s . The s h o r t - t a i l mice and an i s o l a t e d i n d i v i d u a l (101-95-22) can be i d e n t i f i e d as austerus and most of the l o n g - t a i l e d mice can be i d e n t i f i e d as oreas. Nine mice of the l o n g - t a i l group have t a i l s of 103 or l e s s , too short f o r a d u l t oreas. Foot length i n these nine i s 21-24, and the s k u l l dimensions f i t both, s p e c i e s . T h i s group may belong to e i t h e r species or may be hy b r i d s . Three Peromyscus from P o r t Orchard (81), near Puget Sound i n K i t s a p County, are oreas. Four from A r i e t t a (82), on the west side of Puget Sound i n P i e r c e County, are aus-t e r u s . Mason County forms the southeast part of the Olympic P e n i n s u l a . A c o l l e c t i o n from Lake Cushman (83) at the base of the Olympic Mountains i n c l u d e s four oreas and one austerus. From the north f o r k of the Skokomish R i v e r are 13 oreas, one austerus, and one questionable (group 3, 96-101-23, resembles 70. austerus i n some pelage c h a r a c t e r s ) . Three specimens from Shelton (84) are oreas, three probably oreas, three austerus, and two indeterminable (no s k u l l , 95' -95-23; no s k u l l , 115-110-22). Skamania County i s i n the Cascade Mountains north of the Columbia R i v e r . From Skamania (85) on the r i v e r are two oreas and one austerus; from Stevenson (86), on the r i v e r f a r t h e r east, are two or eas. There are two oreas from 15 m i l e s north; of Carson. A c o l l e c t i o n from S p i r i t Lake (87) i n the northwest part of the county i n c l u d e s f o u r oreas, one probable oreas (group 3, 101-103-24), and one p o s s i b l e austerus (no s k u l l , 97-97-22). C l a r k County i s on the Columbia R i v e r west of Skamania County. F i v e specimens from Vancouver (88), on the r i v e r , are austerus. Two from 1^ mil e s west of Y a c o l t (89) are austerus. A sample of 20 specimens from 3 i mil e s west and f i v e m i l e s north of Y a c o l t i n c l u d e s both oreas and austerus. On the basi s of t a i l l e n g t h there are two d i s t i n c t g r o u p s — 88-95 and 101-112. The s h o r t - t a i l group probably c o n s i s t s e n t i r e l y of austerus, though one i n d i v i d u a l has hind foot 23. The l o n g - t a i l group includes a number of mice wi t h t a i l l eng-ths near the oreas-austerus b o r d e r l i n e . A l l but one have hind, f o o t 22 or greater and most are undoubtedly oreas. Measurements of the two questionable i n d i v i d u a l s a r e — g r o u p 3, 90-95-23; group 4, 101-103-21. Specimens from Ambo'-y (90), north of Y a c o l t , i n c l u d e three oreas, seven austerus, and one probable austerus (group 2, 75-81-23). 7 1 -C o w l i t z County i s on the Columbia R i v e r north of C l a r k County. A s e r i e s c o l l e c t e d along the Kalama R i v e r i n c l u d e s f o u r austerus from the mouth (91), f i v e from two m i l e s east of the mouth, and one from three m i l e s east. From four miles east i s a probable oreas (group 4, 96-106-22) . From s i x m i l e s east there are an austerus and a pro-bable oreas (group 3, 91-109-21). One specimen from K e l s o (92), j u s t north of the Columbia R i v e r , i s austerus, and two from C a s t l e Rock (93), f a r t h e r north, are oreas. Lewis County i s north of C o w l i t z County, extending from the W i l l a p a H i l l s east across the Puget Sound Lowlands to the Cascade summit. From Chehalis (94), i n the lowlands, are f o u r austerus, one probable austerus (group 4, 88-92-23) , and two questionable (group 3, 107-98-24; group 3, 104-104-24). From eig h t m i l e s west of Ch e h a l i s are s i x austerus and two oreas. The sample of 25 oreas from La Wis Wis (95) i n the Cascades i s analyzed with the Denny Creek sample. Thurston County i s north of Lewis County, at the south end of Puget Sound. C o l l e c t i o n s from here include f i v e aus-t e r u s from Rochester (96), seven oreas and three austerus from Tenino (97), one austerus from Olympia (98), one oreas from four miles south of t h e r e , two oreas from 10 mi l e s south of there, and f o u r austerus from N i s q u a l l y F l a t s . P i e r c e County l i e s between Puget Sound and the Cascade summit. Steilacoom (99) on Puget Sound i s the type l o c a l i t y of austerus. Eighteen specimens from here belong to t h i s 72.. race. Maximum t a i l l e n g t h i s 91; maximum hind f o o t length i s 22. None has a white spot on the t a i l . One specimen from Tacoma (100) i s oreas; f o u r from s i x m i l e s south of there are austerus. There are an oreas and an austerus from Roy (101), f a r t h e r south, an cr eas from Kapowsin (102), east of Roy, and eig h t austerus from P u y a l l u p (103), east of Tacoma. Most specimens from a number of l o c a l i t i e s on or near Mt. R a i n i e r (104) are oreas. Some specimens have apparent austerus or mixed charact e r s , but at l e a s t some of these are a r e s u l t of measurement e r r o r s . Some h i n d f o o t measure-ments are o b v i o u s l y too low, and one specimen from 10,000 f e e t e l e v a t i o n has t a i l length 100, i n the austerus range. A specimen from N i c k e l Creek (3350 f e e t ) may w e l l be aus-t e r u s (group 3, 82-98-20). Of two from Tahoma Creek (2500 f e e t ) , one i s oreas and the other has mixed characters (group 3, 96-96-232, s k i n resembles a u s t e r u s ) . The l a b e l s of most of e i g h t skins from "5,000 f e e t , Mt. R a i n i e r " bear some measurements c h a r a c t e r i s t i c of austerus. These are o l d s k i n s , p o o r l y prepared, and i t seems a l t o g e t h e r u n l i k e l y t h a t austerus occurs at such an e l e v a t i o n . K i n g County i s north of P i e r c e County, between Puget Sound and the Cascade c r e s t . F i v e specimens from Kent (105), south of S e a t t l e , are austerus, as are eight from Vashon I s -land (106) i n Puget Sound. A l l 85 specimens that I have exa-mined from S e a t t l e (107) are austerus. I have not analyzed 73. t h i s c o l l e c t i o n s t a t i s t i c a l l y (except f o r a few MVZ s p e c i -mens included i n the Puget Sound sample) because I b e l i e v e t h a t the data are e s p e c i a l l y l i a b l e to e r r o r . The great m a j o r i t y of specimens have both body and t a i l l e n g t h of l e s s than 95. Exceptions a r e — b o d y 97 ( 3 ) , 99 ( 1 ) ; t a i l 95, 97, 100, 103. Two specimens have f o o t length 23. None has a white spot on the t a i l . A specimen from \ mile east of K i r k l a n d (108), north-east of S e a t t l e , i s austerus. From one mile east are an austerus and an oreas, and from three m i l e s east f o u r aus-t e r u s and three probable oreas. A c o l l e c t i o n of 25 specie mens from B o t h e l l (109), north of S e a t t l e , c o n s i s t s of 21 austerus and f o u r oreas. None has a white spot on the t a i l . One specimen from Enumclaw (110), i n the southern part of the count;/, i s an oreas. Seventeen specimens from Twin creeks (111), east of Enumc lav/ at the f o o t of the Cascades, are oreas. Denny Creek (112) i s east of S e a t t l e , two m i l e s west of the Cascade c r e s t . Twenty-four specimens from here are oreas. The Denny Creek, Twin Creeks, and La Wis Wis samples are analyzed together i n F i g u r e s 5, 13, and 23 and t h e i r t a i l / b o d y e l l i p s e i s shown i n F i g u r e 17. Snohomish County i s north of King County. Two mice from Monroe (113), northeast of B o t h e l l , are austerus. Two from Index (114), east of Monroe, are oreas. From four m i l e s south of E v e r e t t (115), near Puget Sound, are f o u r austerus and one oreas. S i x specimens from A r l i n g t o n (116), 74. north of E v e r e t t , are austerus, as are two from Oso (117) and two from Darrington (118), i n the Cascades. I s l a n d County E l e v e n specimens from Whidby I s l a n d (119), i n Puget Sound o f f Snohomish County, are austerus. S k a g i t County i s north of Snohomish County. Four spe-cimens from La Conner (120), on Puget Sound, are austerus. A c o l l e c t i o n from Mt. Vernon (121), east of La Conner, i n -cludes 17 austerus and four oreas. Hamilton (122) and Rock-port (123), on the Skagit R i v e r i n the c e n t r a l part o f the county, are represented by two austerus each. Whatcom County l i e s between Skagit County and the i n -t e r n a t i o n a l boundary. Three specimens from Bellingham (124) and two from B l a i n e (125) are austerus. Both l o c a l i t i e s are on Puget Sound. T-wo specimens from U. S. Cabin, 2600 f e e t , C h i l l i w a c k R i v e r (126), i n age group 3, measure 81-103-22 and 87-98-22. T h e i r pelage i s l i k e that of oreas. B r i t i s h Columbia Vancouver (127) i s at the mouth of the F r a s e r R i v e r , separated from the B r i t i s h Columbia Coast Range by Burrard I n l e t . The large c o l l e c t i o n of Peromyscus from here (142 specimens) c o n s i s t s e n t i r e l y of austerus. Most specimens are from P o i n t Grey, at the western end of the c i t y . The ex t e r n a l measurements are analyzed i n F i g u r e s 7, 15, 25, and 33. Greatest body lengths are 94 (6) and 95 ( 3 ) ; l e a s t a d u l t body lengths are 70, 71 ( 3 ) , 72, and 74. Greatest t a i l lengths are 95 ( 3 ) , 97 ( 3 ) , 99, 100, 101, 102 (2), and F i g u r e 33. S c a t t e r diagram of t a i l length/body l e n g t h data f o r P. m. austerus from Vancouver, B.C. An equal frequency e l l i p s e has been f i t t e d to these data. To face page 75. 76. 103; l e a s t a d u l t t a i l lengths are 71, 75 ( 2 ) , 73 ( 3 ) , and 79. One hind f o o t length i s 23, the others 22 or l e s s . Pelages cover the complete c o l o r range from very l i g h t w i t h almost no d r o s a l s t r i p e to dark w i t h a broad black d o r s a l s t r i p e . None has a white spot on the t a i l . Austerus a l s o i s a v a i l a b l e from Huntingdon (128), 8; and Sumas, 3, on the F r a s e r D e l t a east of Vancouver. Cu l t u s Lake (129) i s on the southern edge of the F r a -ser D e l t a at the f o o t of the Cascades. My c o l l e c t i o n of 27 specimens from here c o n s i s t s e n t i r e l y of austerus. One spe-cimen by another c o l l e c t o r has mixed characters (no s k u l l , 93-110-21, pelage resembles a u s t e r u s ) . I f these measure-ments are c o r r e c t t h i s i n d i v i d u a l may be a hybrid of oreas and austerus. There are f i v e austerus and one specimen with mixed characters (no s k u l l , 95-107-21) from Vedder C r o s s i n g , j u s t n o r t h of Cultus Lake. Seventeen specimens from Robert-son's (130), on t h e C h i l l i w a c k R i v e r two m i l e s east of Ved-der C r o s s i n g , are austerus. The Cultus Lake and Robertson's data are analyzed i n F i g u r e s 7, 15, and 25. The t a i l / b o d y e l l i p s e (not shown) f a l l s e n t i r e l y w i t h i n that f o r Vancouver. Greatest lengths are 89-101-22. A c o l l e c t i o n from 1100 f e e t on the C h i l l i w a c k R i v e r 16 miles east of Vedder C r o s s i n g (131) c o n s i s t s of seven austerus and one oreas. Lihumitson Mountain (132) i s on the I n t e r n a t i o n a l Boundary southeast of Vedder C r o s s i n g , h i g h i n the Cascades. I t i s near the type l o c a l i t y of oreas. 77. Twenty specimens from here belong to t h i s s p e c i e s . From Welch Peak (133), north of the C h i l l i w a c k R i v e r , are three oreas and one questionable (group 3, 101-97-22). From Wah-l e a c h Lake (134), north of Welch Peak, are two oreas. Hope (135) i s at the eastern end of the F r a s e r D e l t a , at the f o o t of the Cascade Mountains. C o l l e c t i n g was c a r -r i e d out along the highway f o r s e v e r a l miles east and west of here, at 150-900 f e e t e l e v a t i o n . The t a i l / b o d y data are shown i n F i g u r e 34, w i t h the e l l i p s e s f o r the Wright's Ranch oreas and the "Vancouver austerus. Most of the mice which f a l l w i t h i n the upper part of the oreas e l l i p s e had hind f e e t of 22 or more; most of those i n the austerus e l l i p s e had hind f e e t 21 or l e s s . Hind f o o t lengths of the excep-t i o n s are i n d i c a t e d i n the f i g u r e . T h i s sample shows s e v e r a l unusual f e a t u r e s . The t a i l s of the younger i n d i v i d u a l s are f a i r l y uniform i n l e n g t h and are somewhat intermediate between austerus and oreas. The a d u l t s show greater v a r i a b i l i t y , t a i l l e n g t h ranging from 90 to 120. T h i s i n c l u d e s almost the f u l l range of oreas, but only the upper part of the austerus range. The long-t a i l p o i n t s f i t the narrow Wright's e l l i p s e w e l l , r a t h e r than the broad Heah Bay and Denny e l l i p s e s . Young animals extend much higher i n the e l l i p s e i n t h i s sample than i n those from other l o c a l i t i e s , and are mixed w i t h a d u l t s over a wide range of t a i l and body length . A number of long-t a i l mice have hind f e e t only 21. F i g u r e 34. S c a t t e r diagram of t a i l length/body l e n g t h data f o r Peromyscus from Hope. Equal frequency e l l i p s e s f o r oreas from Wright's and austerus from Vancouver have been superimposed. Numbers beside p o i n t s show hind f o o t l e n g t h . To face page 78. 78. 79. A l l these data are from my own c o l l e c t i o n , and the nrnsurement s should at l e a s t be c o n s i s t e n t . The uniform and intermediate sample of young mice could be drawn from an intergrade p o p u l a t i o n . The lower end of the range of adult t a i l length i s also intermediate between those of oreas and austerus, but the upper end i s c h a r a c t e r i s t i c of oreas. There could be an intergrade population at the lower e l e v a t i o n s and pure oreas at the higher ones, but the a c t u a l geographic d i s t r i b u t i o n does not f i t t h i s p i c t u r e . Both l o n g - t a i l and s h o r t - t a i l mice were taken on the ex-treme eastern and western t r a p l i n e s and on most of the l i n e s between, and a l l the mice with t a i l s longer than 106 are from low e l e v a t i o n s . The l o n g - t a i l , s h o r t - f o o t c o n d i t i o n could r e s u l t from h y b r i d i z a t i o n i f these are u n i t c h a r a c t e r s , but there i s no reason to b e l i e v e that t h i s i s t r u e . The apparent youth of some larg e i n d i v i d u a l s could r e s u l t from an unusually slow r a t e of molar wear or from any of s e v e r a l types of e r r o r , but t h i s seems u n l i k e l y . A c o l l e c t i o n from the C o q u i h a l l a R i v e r , f i v e m i l e s northeast of Hope (136), includes three austerus, one.oreas, and two probable oreas (group 2, 81-98-22; group 2, 85-99-22). Upper Skagit R i v e r (137) C o l l e c t i o n s were made along the Skagit and Sumallo R i v e r s f o r two m i l e s above t h e i r junc-t i o n , at e l e v a t i o n s of 2000-2500 f e e t . The ad u l t s i n the c o l l e c t i o n are d i v i s i b l e i n t o a s h o r t - t a i l group (90 or l e s s ) 80. and. a l o n g - t a i l group (98 or more). The s h o r t - t a i l mice e v i d e n t l y are austerus, and most of the l o n g - t a i l mice are oreas. The lower members of the l o n g - t a i l group are ques-t i o n a b l e . Some could belong to e i t h e r race; others show mixed characters (group 4, 88-98-23; no s k u l l , 90-104-21). There are three a d u l t s with t a i l 90 or l e s s and hind f o o t 22 or l e s s , 26 w i t h t a i l 105 or more and hind f o o t 22 or more, and nine w i t h t a i l 98-104 and hind f o o t 21-23. Ross Lake (138) i s an impoundement of the Skagit R i v e r , extending across the I n t e r n a t i o n a l Boundary i n t o B r i t i s h Columbia. A s e r i e s from s e v e r a l l o c a l i t i e s a few m i l e s n o r t h of here i n c l u d e s 15 austerus, e i g h t oreas, and two questionable. The hind f o o t measurements f o r most of these specimens are not c o r r e c t . Specimens from Agassiz (139), 7; H a r r i s o n Lake (140), 1; and H a t z i c (141), 1; on the north side of the F r a s e r R i v e r , are austerus. Haney (142) i s on the north s i d e of the r i v e r , 30 m i l e s east of Vancouver. A s e r i e s of mice from one mile (50 f e e t ) and three m i l e s (450 f e e t ) north of here i s f a i r -l y uniform i n t a i l / b o d y measurements, and i s approximately intermediate between austerus and oreas i n t a i l l e n g t h . T a i l lengths of a d u l t s range from 89 to 105; hind f o o t lengths range from 21 t o 23. T h i s intermediate c o n d i t i o n s t r o n g l y suggests t h a t the p o p u l a t i o n i s an i n t e r g r a d e one. Arguing against t h i s i s the low value f o r the slope of the. 81. standard major a x i s (a = 1.007). T h i s i s lower than the values f o r the Vancouver and Cultus Lake austerus, although an intergrade p o p u l a t i o n should have a higher value. Loon Lake (143) i s f i v e m i l e s north of Haney, at 1150 f e e t . A larg e s e r i e s from here have e x t e r n a l dimensions s i m i l a r to those of the Haney s e r i e s . The smaller mice have uniform and intermediate t a i l / b o d y measurements, and the l a r g e r ones have a s i m i l a r range of t a i l l e ngth (85-105) (Fig.35) . The l o n g - t a i l mice have a wide range of body length (71-92), causing the s c a t t e r of points to be much wider at the top .than at the bottom. There i s over-lap i n the d i s t r i b u t i o n of fo o t lengths c h a r a c t e r i s t i c of oreas and austerus, the extremes being t a i l 98, foot 23 and t a i l 104., f o o t 21. Pelage characters are not d i s t i n c -t i v e . T h i s p o p u l a t i o n may be intergrade between oreas and austerus or may be a l o c a l d e v i a t i o n from the c h a r a c t e r i s -t i c ' austerus c o n d i t i o n . Hybrid o r i g i n i s u n l i k e l y , because no oreas are known t o occur i n the area. Some i n d i v i d u a l s i n the c o l l e c t i o n may be oreas, but i f t h i s species i s pre-sent at a l l the c o l l e c t i o n should i n c l u d e some i n d i v i d u a l s w i t h t a i l s longer than 105. The s t a t i o n i s w i t h i n a few hundred f e e t of the top of a h i l l and i s surrounded by lower e l e v a t i o n s , so that there i s no apparent place where oreas might occur nearby. I f i n t e r g r a d a t i o n does occur here i t must extend over a wide area and a wide range of e l e v a t i o n s , r a t h e r than be confined to a narrow a l t i t u d i n a l zone. F i g u r e 35. S c a t t e r diagram of t a i l length/body length data f o r Peromyscus from Loon Lake. Equal frequency e l l i p s e s f o r oreas from Wright's and austerus from Vancouver have been superimposed. To face page 82. 8 2 . 83. E i g h t oreas were taken at Port Moody (144) by one c o l -l e c t o r , one oreas and eight austerus by another. Port Moody i s at the head of Burrard I n l e t , a t the f o o t of the Coast Range. The c o l l e c t o r s probably trapped i n d i f f e r e n t places i n t h i s area. Mount Seymour (145) i s 25 miles west of Loon Lake, and l i k e i t i s i n the Coast Range immediately north of the F r a s e r V a l l e y . The Peromyscus c o l l e c t i o n s from these s t a -t i o n s are a l t o g e t h e r d i f f e r e n t , though. On Mount Seymour only austerus was taken up to e l e v a t i o n s much higher than t h a t of Loon Lake and at the highest e l e v a t i o n s o n l y oreas was taken. There i s an intermediate zone i n which both occur. Fourteen austerus were taken at 1500 f e e t , w i t h maxi-mum t a i l l e ngth 99, maximum foo t l e n g t h 22. Another s p e c i -men from there i s questioia ble (group 4, 90-105-22). Four austerus (maximum 98-22) were taken at 2200 f e e t . E i g h t oreas were taken at 2900 f e e t ( t a i l 109-124, f o o t 22J-25). At 2500-2700 f e e t both races and questionable i n d i v i d u a l s were taken. Two oreas, one austerus, and two questionable (group 2, 78-94-22; group 2, 77-90-22^) are from 2 500 f e e t . From 2700 f e e t there are 10 oreas, two austerus, and nine indeterminable. The indeterminable specimens may belong to e i t h e r race or may be hy b r i d s . There c l e a r l y i s no i n t e r -grade population here. The zone of a l t i t u d i n a l overlap i s wider than shown by t h i s s e r i e s , because one d e f i n i t e austerus 84. was taken during l i v e - t r a p p i n g at e l e v a t i o n s 2900-3300 f e e t . Some of the other mice taken at these e l e v a t i o n s may be i n -termediate i n measurements, but i n general appearance they resemble oreas. North Vancouver (146) i s n o r t h of Burrard I n l e t at the base of the Coast Range. Both oreas and austerus are represented i n the c o l l e c t i o n s from v a r i o u s l o c a l i t i e s i n t h i s area: North Vancouver—3 austerus; 600 f e e t — t h r e e oreas, 2 austerus; Mahon P a r k — 3 austerus; Makay C r e e k — 2 oreas; Grouse M o u n t a i n — 1 austerus; 3000 f e e t — 1 oreas; Dog Mountain, 4000 f e e t — 1 oreas, 1 austerus. Some s p e c i -mens w i t h austerus measurements are from l o c a l i t i e s which seem too high f o r th a t race. Austerus has been taken at Squamish (147), 3; Hop-k i n s Landing (148), 4; and Gibsons Landing (148), 8, on Hovve Sound. A l t a Lake (149) i s i n a low pass (2100 f e e t ) through the Coast Range. The Peromyscus of t h i s area have been i d e n t i f i e d as oreas (Racey and Cowan 1935) hut some s p e c i -mens do not have e x t e r n a l dimensions c h a r a c t e r i s t i c of t h a t s p e c i e s . One of the 20 specimens examined has e x t e r n a l d i -mensions of austerus but resembles oreas more c l o s e l y i n s k u l l and pelage characters (group 3, 92-92-21). Question-able specimens are: Group 4, 96-96-23; group 5, 108-102-22; group 3, 101-104-23; group 3,. 87-96-23. Some of these specimens could be oreas x austerus h y b r i d s , but those w i t h 8 5 . body length over 100 could.not be explained i n t h i s way. Some of these measurements may be i n c o r r e c t . Two t a i l s have a white spot, 3 and 4 mm. long. Austerus was taken at higher e l e v a t i o n s than t h i s on Mount Seymour and might be expected to occur here too. B r i t i s h Columbia Coast T h i s sample c o n s i s t s of c o l -l e c t i o n s from s e v e r a l c o a s t a l s t a t i o n s north of Howe Sound, a l l presumably near sea l e v e l . E l e v e n specimens from Lund (150) are austerus. There are nine austerus and one oreas from Bute I n l e t ( 1 5 1 ) . The c o l l e c t i o n from Loughborough I n -l e t (152) includes nine specimens with t a i l length 102-117, f o o t length 2 2 - 2 4 , and 19 specimens w i t h t a i l length 7 5 - 9 7 , f o o t length 21-22. McCabe and Cowan (1945) undoubtedly are co r r e c t i n saying that oreas and austerus occur together here, apparently without i n t e r b r e e d i n g . T h i s i s the north-ernmost s t a t i o n from which 1 have seen austerus. E x t e r n a l dimensions of austerus from .these s t a t i o n s are analyzed i n Fig u r e s 7, 15, and 2 5 . I n summary, oreas and austerus occur together over much of western Washington and i n a zone on the western side of the Cascades-Coast Range i n B r i t i s h Columbia. The lack of completely d i s t i n c t i v e characters f o r separating these races makes i n t e r p r e t a t i o n of t h e i r taxonomic r e l a t i o n s d i f -f i c u l t . The Upper Skagit R i v e r , Mt. Seymour, and other sam-pl e s c o n s i s t of a mixture of the two races , but many samples c o n t a i n p o s s i b l e h y b r i d s and some, e.g. Hope and Loon Lake, 86. may be from intergrade populations. I n s p i t e of t h i s , both races maintain t h e i r separate i d e n t i t i e s over a larg e area of sympatry. 4. oreas and macrorhinus 1 The r e l a t i o n between these races cannot be determined at the present time. McCabe and Cowan (1945) have t r e a t e d macrorhinus and neighboring forms i n some d e t a i l , but the a v a i l a b l e c o l l e c t i o n s are not s u f f i c i e n t t o permit f i n a l a n a l y s i s of a s i t u a t i o n as complex as t h i s . The Peromyscus populations of the c e n t r a l B r i t i s h Columbia coast probably have been i n f l u e n c e d by the v a r i e d populations of the o f f -shore i s l a n d s to the west, the populations of the Coast Range to the east, and, through the mountain passes, the populations of the i n t e r i o r of the province. Furthermore, the coast i s deeply d i s s e c t e d by i n l e t s which produce a high degree of l o c a l i s o l a t i o n i n the c o a s t a l populations. There i s great topographic d i v e r s i t y , e l e v a t i o n s ranging from sea l e v e l t o many thousands of f e e t . A l l a u t h o r i t i e s have s a i d t h a t macrorhinus intergrades w i t h oreas. Osgood (1909) placed the area of i n t e r g r a d a t i o n at R i v e r s I n l e t , where some i n d i v i d u a l s could be r e f e r r e d t o one or the other of these races while others were i n t e r -mediate. Anderson (1946) reported i n t e r g r a d a t i o n f a r t h e r n o r t h , i n the B e l l a Coola area, but Cowan and Guiguet (1956) consider these specimens to be intergrades between macro-r h i n u s and a r t e m i s i a e . McCabe and Cowan (1945) i d e n t i f i e d 87. mice from Kingcome I n l e t , south of R i v e r s I n l e t , as i n t e r -grades between macrorhinus and oreas. They suggest that these races may be i n contact over a long d i s t a n c e , oreas occupying the mountains and macrorhinus the adjacent coast. C e n t r a l Coast T h i s sample c o n s i s t s of c o l l e c t i o n s from s e v e r a l s t a t i o n s on the B r i t i s h Columbia mainland oppo-s i t e Q,ueen C h a r l o t t e Sound. I t i s analyzed i n F i g u r e s 8 , 16, 26 , and 36. The l a r g e s t c o l l e c t i o n i s from the most northern s t a t i o n , Lowe I n l e t ( 153) . The Lowe I n l e t sample f i t s the common equal frequency e l l i p s e f o r t a i l / b o d y data w e l l and seems t y p i c a l of the subspecies. Two of the 21 specimens have some brown on the hind f e e t , but none show the other r u b r i v e n t e r c h a r a c t e r s . Two have a 3 mm. white spot on the t a i l , and two have white t i p t u f t s . The Kynoch I n l e t (154) c o l l e c t i o n also i s included i n the C e n t r a l Coast sample. Four specimens from here are mac-r o r h i n u s . One has s k u l l l e n g t h greater than any oreas. (27.9). The hind f e e t show a s l i g h t brownish tendency. Of seven spe-cimens from Tom Bay ( 155) , three have some red on the venter and t a i l brown below. One has a 2 mu. white spot on the t a i l . Some have brown f e e t . One of 10 specimens from Beaver S e i n i n g Grounds (156) has red on the venter but t a i l b i c o l o r . One has white t a i l t i p . A l l have brown f e e t . These s p e c i -mens average smaller than the other samples, but the sample i s too s m a l l f o r t h i s t o be s i g n i f i c a n t . The Koeye R i v e r (157) sample of 16 macrorhinus averages l a r g e r than the others F i g u r e 36. S c a t t e r diagram of t a i l length/body l e n g t h data f o r P. m. macrorhinus from C e n t r a l Coast. An equal frequency e l l i p s e has been f i t t e d to these data, o m i t t i n g the p o i n t s i n double c i r c l e s . F i g u r e 37. S c a t t e r diagram of t a i l length/body le n g t h data f o r Peromyscus from R i v e r s I n l e t . Equal f r e -quency e l l i p s e s f o r oreas from Neah Bay and macro-rh i n u s from C e n t r a l Coast have been superimposed. To face page 83. 89. i n the C e n t r a l Coast sample, but again t h i s may r e s u l t from small sample s i z e . One has some re d on venter but t a i l b i c o l o r . Two have white t a i l t i p . Neekas Creek (158) i s near Tom Bay, but the mice from there are quite d i f f e r e n t i n dimensions. F i g u r e s 8, 16, and 26 show that t h i s sample averages l a r g e r than the C e n t r a l Coast sample. The d i f f e r e n c e i s s t a t i s t i c a l l y h i g h l y s i g -n i f i c a n t f o r a l l three e x t e r n a l dimensions. T h i s g r e a t e r s i z e may represent l o c a l v a r i a t i o n . I t could not r e s u l t from i n t e r g r a d a t i o n with another mainland race because the neighboring races are s m a l l e r . S i x of 27 specimens have red on venter and seven of 26 have t a i l brown below. The hind f e e t are white, brown, or m o t t l e d . None of the t a i l s has a white spot. T h i s s t a t i o n i s i n a f a v o r a b l e p o s i t i o n t o r e c e i v e immigrants from the i s l a n d s with populations of rub-r i v e n t e r , which could e x p l a i n the l a r g e r s i z e as w e l l as the h i g h frequency of r u b r i v e n t e r pelage c h a r a c t e r s . R i v e r s I n l e t (159) i s south of the C e n t r a l Coast l o c a -l i t i e s . The Peromyscus population(s) at t h i s s t a t i o n has long puzzled s y s t e m a t i s t s . Osgood (1909) considered them in t e r g r a d e s between oreas and macrorhinus. The t a i l / b o d y data f o r t h i s sample are p l o t t e d i n F i g u r e 37. The s c a t t e r of p o i n t s i s almost c i r c u l a r , u n l i k e the elongate form char-a c t e r i s t i c of such f i g u r e s . T h i s suggests t h a t the sample may be a mixture of r a c e s . The e l l i p s e s f o r the Neah Bay oreas and the C e n t r a l Coast macrorhinus have been super-imposed on t h i s graph, and together include a l l but two of 90. the p o i n t s . As would he expected i f the sample i s mixed, the points are more dense where the e l l i p s e s o verlap, but the d i f f e r e n c e i s too great to be explained on t h i s basis alone. The area of overlap i s somewhat l e s s than h a l f the t o t a l area of the combined e l l i p s e s , but i t i n c l u d e s 58 of the 65 poin t s w i t h i n the e l l i p s e s . None of these specimens shows the r u b r i v e n t e r pelage c h a r a c t e r s . Ten have white spots on the t a i l , averaging 9 mm. long. A l l i n d i v i d u a l s with white spot are included i n the oreas e l l i p s e . The sample i s not separable i n t o two components on the b a s i s of pelage c o l o r , t h e r e being no more v a r i a b i l i t y here than i n other samples from the B r i t i s h C o l -umbia coast. The sample i s composed of specimens from s e v e r a l l o -c a l i t i e s , a l l of them e i t h e r at or near the head of R i v e r s I n l e t (159) or at or near the head of Owikeno Lake (160). T h i s lake i s east of and drains d i r e c t l y i n t o R i v e r s I n l e t . The head of the lake i s about 25 m i l e s east of the head of the i n l e t . The specimens from the head of the l a k e are d i s -t i n c t l y smaller than those from the head of the i n l e t . The small e r body s i z e may i n d i c a t e that the mice from the head of the lake are oreas, but these mice also have sho r t e r t a i l s , which would not be true of oreas. A l l these s p e c i -mens are included i n the oreas e l l i p s e , but three are not included i n the macrorhinus e l l i p s e . Hind foot length i s s i m i l a r i n both samples, and both samples inc l u d e mice wi t h white spot on the t a i l . McCabe and Cowan (1945) found t h a t samples from i n l e t heads are smaller than those from the head-lands, and an extension of t h i s phenomenon f a r t h e r i n l a n d might e x p l a i n the smaller s i z e of the specimens from the head of Owikeno Lake. The p e c u l i a r character of t h i s sample can he at l e a s t p a r t l y explained i n any of s e v e r a l ways. Oreas and macro-rhi n u s may occur together i n t h i s area without i n t e r b r e e d i n g , or they may h y b r i d i z e to a l i m i t e d extent. The po p u l a t i o n could not be c a l l e d a tru e intergrade one, because both pa-ren t forms are i n c l u d e d and v a r i a b i l i t y i s h i g h . Kingcome I n l e t (161) i s south of R i v e r s I n l e t . McCabe and Cowan (1945) considered specimens from here t o be i n t e r -grades between oreas and macrorhinus, saying that they r e -semble oreas i n c r a n i a l measurements, approach macrorhinus i n c o l o r , and are noncommital i n e x t e r n a l measurements. The average body l e n g t h ( 9 3 . 2 9 ) i s intermediate between t h a t of oreas ( 9 0 . 4 5 ) and tha t of macrorhinus ( 9 6 . 8 6 ) . However, s i x specimens of oreas from American Forks average 9 4 . 8 3 and 14 from G-oodfellow average 9 2 . 6 4 , and the Kingcome sample may be oreas that are s l i g h t l y l a r g e r than average. Seven of 20 t a i l s have a white spot, averaging s i x mm. lo n g . None of the r u b r i y e n t e r characters i s present. E x t e r n a l dimen-sions of t h i s sample are shown i n F i g u r e s 5 , 1 3 , and 2 3 . The t a i l / b o d y data f o r t h i s sample f i t the e l l i p s e f o r Neah Bay oreas f a i r l y w e l l , but f i t the one f o r C e n t r a l Coast macrorhinus p o o r l y . The standard major a x i s of t h i s sample 92. has a growth constant of a = 1.353, compared to 1.013 f o r the C e n t r a l Coast macrorhinus and a minimum of 1.273 f o r the oreas samples (Table I ) . T h i s i n d i c a t e s that the K i n g -come mice are pure oreas, not i n t e r g r a d e s . Oreas and macrorhinus are remarkably a l i k e . The s l i g h t l y longer body of macrorhinus and low t a i l / b o d y growth constant of that race are the p r i n c i p a l t h i n g s d i s -t i n g u i s h i n g i t from oreas. They do seem d i s t i n c t , though, and there i s no good evidence t h a t they i n t e r g r a d e , so i t i s j u s t i f i a b l e to separate them s p e c i f i c a l l y pending f u r t h e r f i e l d s t u d i e s on the c e n t r a l B r i t i s h Columbia coast. Such s t u d i e s should i n c l u d e p a r t i c u l a r a t t e n t i o n to h a b i t a t , e l e -v a t i o n , and r e l a t i o n to the c o a s t l i n e . U n t i l such work has been done f u r t h e r s p e c u l a t i o n on the subject i s l i k e l y t o prove s t e r i l e . 5 . gambeli and austerus Both races have been c o l l e c t e d i n Skamania County, i n the Cascades of southern Washington, but t h e i r r e l a t i o n -s h i p there i s not known. They presumably intergrade along the Columbia R i v e r , and Dice (1949) has reported that a stock of Peromyscus from Bingen, on the north shore i n southwestern K l i c k i t a t County, i s intermediate between these races. Apparently n e i t h e r race reaches the mountain passes f a r t h e r north. Snoqualmie Pass (3010 f e e t ) i s the lowest, and c o l l e c t i n g at s t a t i o n s s e v e r a l m i l e s east and 93. west of there y i e l d e d only oreas, though gambeli was taken at higher e l e v a t i o n s i n other areas. 6. gambeli and artemisiae The maniculatus populations of eastern Washington ex-h i b i t much microgeographic v a r i a t i o n w i t h i n a narrow range of t o t a l v a r i a t i o n . S u b s p e c i f i c designations probably mean l i t t l e here, but specimens t h a t I have examined from north-eastern .Washington and from the Blue Mountains of southeastern Washington seem to be s l i g h t l y l a r g e r and darker than those from the c e n t r a l part of the s t a t e , and probably should be separated from them as Dalquest (1948) has done. Samples from near the Columbia R i v e r i n northern Grant County (162) c o n s i s t e n t i r e l y of maniculatus. They are l a b e l l e d "gambeli" but f i t the a r t e m i s i a e e l l i p s e s b e t t e r . T h i s area i s near the artemisiae-gambeli border as drawn by Dalquest. 7 . a r t e m i s i a e and austerus The Cascade Mountains are separated from the B r i t i s h Columbia Coast Range by the canyon of the F r a s e r R i v e r , which forms a low r-level c o r r i d o r from the dry i n t e r i o r to the humid coa s t . The mountains on both sides of the canyon exceed 6000 f e e t e l e v a t i o n , but the maximum e l e v a t i o n of the r i v e r i s about 500 f e e t , near L y t t o n . Cowan and Guiguet (1956) i n d i c a t e that the Canyon i s occupied by oreas, but t r a p p i n g at a number of s t a t i o n s i n the canyon bottom has y i e l d e d only maniculatus. Both species 9h. were taken at a s t a t i o n i n the mountains east of the r i v e r ( f i v e m i l e s east of Boston Bar, 50). L i m i t e d samples sug-gest that the I n t e r i o r and c o a s t a l races of maniculatus i n t e r g r a d e along the Canyon. Mean t a i l and body length data f o r these samples are p l o t t e d i n Figure 38. 100 i 90 • 70 60 60 o YOUNG • ADULT I 70 I 80 BODY I 90 2. SPUZZUM (6,7) I. EMORY CR. (2,D 6. ASHCROFT (8,2) 5. L Y T T O N (6,1) • 4. K E E L E R ' S (6,10) 3. ALEXANDRA (6,16) —I 100 F i g u r e 38. Mean t a i l l e n g t h and body length of Peromyscus  maniculatus from the Fraser-Thompson Canyon. E x p l a n a t i o n i n t e x t . The v e r t i c a l l i n e on the r i g h t i n d i c a t e s the approxi-mate s t r a i g h t - l i n e distance between the s t a t i o n s . The f i g u r e s i n parentheses i n d i c a t e the number of young and a d u l t s p e c i -mens. Emory Creek i s near the southern end of the Canyon and, l i k e Spuzzum (163) , i s on the west side of the r i v e r . Alexandra ( 1 6 4 ) , K e e l e r ' s M i l l (I65), and L y t t o n (51) are on the east side of the r i v e r . The F r a s e r R i v e r i s j o i n e d by the Thompson R i v e r from the northeast at L y t t o n . Ash-c r o f t (52), on the east side of the Thompson R i v e r at about 12 00 f e e t e l e v a t i o n , i s the type l o c a l i t y of a r t e m i s i a e . The l i n e s on the l e f t represent animals of age group 2, those on the r i g h t animals of groups 3-5. The heavy l i n e s connect the mean values f o r austerus and a r t e m i s i a e des-c r i b e d i n S e c t i o n I . The l i g h t l i n e s connect the means f o r the s i x s t a t i o n s , i n order from north to south. The p o i n t s f o r austerus and f o r the southern s t a t i o n s are above those f o r a r t e misiae and the northern s t a t i o n s . The samples are not large enough to be analyzed s t a -t i s t i c a l l y , but the trend of the means i s reasonably c o n s i s -t e n t , and p a r a l l e l s the d i f f e r e n c e s between the r a c e s . For some reason the samples from the northern and southern s t a -t i o n s i n the Canyon are more d i f f e r e n t than are the austerus and artemisiae t o t a l s . The range of v a r i a t i o n i s roughly the same f o r each sample, the maximum and minimum body values decreasing from n o r t h to south and the t a i l values i n c r e a s i n g . Adult t a i l l e ngth at K e e l e r ' s M i l l ranges from 77 to 93, at Spuzzum from 84 to 99. Both artemisiae and austerus occur w i t h i n a fev/ m i l e s of A l l i s o n Pass, and they may meet at places along the Cascade 96. summit. Only oreas was taken at A l l i s o n Pass and Gibson Pass, though. Both races occur i n the Skagit R i v e r water-shed i n northern Washington, and may be expected to i n t e r -grade t h e r e . 8 . artemisiae and macrorhinus There are no records of oreas from north of R i v e r s I n l e t , but t h i s means l i t t l e as there are almost no c o l l e c -t i o n s from the mountains north of the r e . T h i s species may extend north beyond t h i s s t a t i o n f o r some d i s t a n c e . I f not, i t i s probable t h a t artemisiae from the i n t e r i o r and macro-r h i n u s from the coast meet somewhere i n or near the mountains, presumably i n t e r g r a d i n g where they come i n contact. The f o l -lowing are the only p e r t i n e n t c o l l e c t i o n s . Anahim Lake (166) l i e s at 3500 f e e t on the C h i l c o t i n P l a t e a u , east of the Coast Range but i n the c o a s t a l water-shed. The large c o l l e c t i o n of ar t e m i s i a e from here averages l a r g e r than the c o l l e c t i o n s from the southern s t a t i o n s i n body length and hind f o o t l e n g t h , but not i n t a i l l e n g t h ( F i g s . 6 , 14, and 2k). The r e l a t i v e growth constant of t a i l / body i s s l i g h t l y g r eater f o r t h i s sample than f o r the one from Okanagan (Table I ) . The equal frequency e l l i p s e f o r these data i s shown i n Fi g u r e 26. Hagensborg (167) i s i n the B e l l a Coo l a v a l l e y , across the mountains 55 m i l e s west of Anahim Lake, and e i g h t miles from s a l t water. McCabe and Cowan (1945) say t h a t charac-t e r i s t i c macrorhinus occur here, but I have not examined t h i s 97. c o l l e c t i o n . L i k e other c o l l e c t i o n s from near i n l e t heads, i t averages sm a l l e r i n body s i z e than those from the outer coast. S t u i e (168) Although 20 m i l e s east of Hagensborg and surrounded by h i g h mountains, t h i s s t a t i o n l i e s i n the B e l l a Coola v a l l e y at only 460 f e e t e l e v a t i o n . There i s o n l y a minor height of land between here and Anahim Lake, 35 miles t o the east. Four s k i n s taken at " S t u i e " by one c o l l e c t o r are a r t e m i s i a e , but a s e r i e s of 13 specimens c o l l e c t e d at " S t u i e , j e t Atnarko R. and Whitewater R." by another party shows mixed c h a r a c t e r s . McCabe and Cowan (1945) b e l i e v e d t h a t these specimens were in t e r g r a d e s of a r t e m i s i a e w i t h e i t h e r oreas or macrorhinus. A l l but one of these specimens have body lengths be-tween 81 and 90. T a i l lengths f a l l i n t o three g r o u p s — 7 9 -85 (7 specimens), 93-95 ( 3 ) , and 102-111 ( 8 ) . The lower group a l l f a l l near the center of the Anahim e l l i p s e ( a r t e -misiae ) and have hind foot lengths of 22 or l e s s ; they pre-sumably are a r t e m i s i a e . The upper group f a l l near the cen-t e r of the C e n t r a l Coast e l l i p s e (macrorhinus) but do not f i t the Neah Bay e l l i p s e (oreas) w e l l ; t h e i r hind f o o t meas-urements are 22 or more. On these grounds t h i s group i s pro-bably macrorhinus. The middle group f a l l s near the upper l i m i t of the Anahim e l l i p s e and has hind foot lengths of 22. These three mice may be extreme a r t e m i s i a e , but because of t h e i r i s o l a t e d p o s i t i o n i t seems more l i k e l y that they are a r t e m i s i a e x macrorhinus h y b r i d s . 98. The s k u l l dimensions (grea t e s t length of s k u l l and leng t h of nasal) of these groups overlap completely, but when p l o t t e d against each other are p a r t l y separated. Those f o r the l o n g - t a i l group f a l l c l o s e together among the p o i n t s of the C e n t r a l Coast macrorhinus sample. The p o i n t s f o r the s h o r t - t a i l group are s c a t t e r e d i n the upper part of the a r t e -misiae e l l i p s e . The two p o i n t s f o r the intermediate group are somewhat intermediate i n p o s i t i o n . The specimens cannot be e n t i r e l y separated on pelage c h a r a c t e r s . The s h o r t - t a i l i n d i v i d u a l s f o r the most part agree w e l l w i t h a r t e m i s i a e from Anahim Lake, and there seems to be no reason not to place them i n t h i s r a c e . The long-t a i l i n d i v i d u a l s are c l o s e r to macrorhinus i n pelage char-a c t e r s , but at l e a s t some could a l s o be a r t e m i s i a e . The sol e of the ""foot resembles macrorhinus, but the h a i r i n e s s of the t a i l i s not h e l p f u l . One specimen wi t h t a i l of i n t e r -mediate length c l o s e l y resembles macrorhinus; the other two are intermediate i n pelage c h a r a c t e r s . The most obvious i n t e r p r e t a t i o n of t h i s sample i s t h a t i t c o n s i s t s of a group of pure a r t e m i s i a e , a group of pure macrorhinus, and s e v e r a l h y b r i d s . I t may be, though, th a t the S t u i e p o p u l a t i o n i s a hybrid swarm, c o n s i s t i n g of i n d i -v i d u a l s w i t h a l l p o s s i b l e combinations of characters and i n c l u d i n g few i f any r a c i a l l y pure i n d i v i d u a l s . There are no specimens wi t h t a i l s near the extremes f o r these r a c e s , but t h i s may be a r e s u l t of small sample s i z e . I t seems 99. probable t h a t the l o n g - t a i l group i s macrorhinus r a t h e r than oreas. Mt. B r i l l i a n t (169) I have been unable to l o c a t e t h i s s t a t i o n . According t o the l a b e l s i t i s i n the Rainbow Mts, B.C. There are two Rainbow Ranges l i s t e d i n the "Gaze-t e e r of Ca n a d a / B r i t i s h Columbia"(1953). The range r e f e r r e d t o here presumably i s the one on the east side of the Coast Range, between Anahim Lake and Eutsuk Lake. Twelve s p e c i -mens from here a l l c l o s e l y resemble ar t e m i s i a e i n pelage c h a r a c t e r s , but have greater e x t e r n a l dimensions than any sample of art e m i s i a e (body 88-113, mean 98.25; t a i l 80-92, mean 85.00; hind f o o t 20-23, mean 21.50). Age groups are not known, but a l l specimens are a d u l t s . T h i s l a r g e s i z e may i n d i c a t e i n t e r g r a d a t i o n w i t h macrorhinus to the west, but the r e l a t i v e l e n g t h of t a i l and body i s s i m i l a r t o t h a t of a r t e m i s i a e . T h i s s t a t i o n i s the highest (5500-6500 f e e t ) from which I have seen a r t e m i s i a e . Eutsuk Lake (170) i s In the eastern part of the Coast Range, north of the Rainbow Range. The western end of the l a k e , where t h i s sample was c o l l e c t e d , i s very near the Coast Range summit. F i v e specimens from here average smal-l e r i n e x t e r n a l measurements than the C e n t r a l Coast sample of macrorhinus, but the d i f f e r e n c e i s not great enough to be s i g n i f i c a n t f o r so small a sample ( F i g s . 8, 16, 26). A l l hind f e e t have a s l i g h t brownish c a s t , but none of the s p e c i -mens has red on venter or undersurface of t a i l brown. One 100. has a white t a i l t i p . These mice are macrorhinus, perhaps showing a s l i g h t tendency toward a r t e m i s i a e . S t i k i n e R i v e r (171) T h i r t y - s e v e n specimens from sev-e r a l l o c a l i t i e s on t h i s r i v e r i n the Coast Range of n o r t h -ern B r i t i s h Columbia are not d i s t i n g u i s h a b l e from C e n t r a l Coast macrorhinus i n body l e n g t h , but have much sh o r t e r t a i l s and s i g n i f i c a n t l y shorter hind f e e t ( F i g s . 8, 16, 26). They can h a r d l y be c a l l e d macrorhinus, and may represent the i n -flu e n c e of P. m. b o r e a l i s Mearns from the east. B o r e a l i s i s s i m i l a r t o a r t e m i s i a e , and replaces i t i n the northern h a l f of the province. 9. austerus and macrorhinus The most northern s t a t i o n f o r austerus (Loughborough I n l e t ) and the most southern f o r macrorhinus (Rivers I n l e t ) are over 100 m i l e s apart. The only c o l l e c t i o n from an I n t e r -mediate s t a t i o n (Kingcome I n l e t ) c o n s i s t s e n t i r e l y of oreas. The B r i t i s h Columbia Coast sample of austerus averages greater i n body length and hind foot length than samples from areas f a r t h e r south, but i s not l a r g e r i n t a i l l e n g t h ( F i g s . 7, 15, 25). I f these populations are i n f l u e n c e d gene-t i c a l l y by the macrorhinus populations to the north they should be g r e a t e r i n a l l three dimensions. F u r t h e r c o l l e c t -i n g along the coast w i l l throw l i g h t on t h i s problem. 101. I I I . EXPER MENTAL HYBRIDIZATION There seems to he general agreement th a t species are c h a r a c t e r i z e d by r e p r o d u c t i v e i s o l a t i o n from a l l r e l a t e d forms, but there i s no such agreement on j u s t what repro-ductive i s o l a t i o n Is or how i t s existence i s to be deter-mined. Most present-day s y s t e m a t i s t s consider i t to be the f a i l u r e of two races to i n t e r b r e e d f r e e l y where they come i n contact i n nature. Occasional h y b r i d i z a t i o n may occur, but the two forms w i l l remain d i s t i n c t . Some workers, e s p e c i a l l y g e n e t i c i s t s , at one time r e -garded reproductive i s o l a t i o n as synonymous wi t h i n t e r -s t e r i l i t y . They concluded that i f any two i n d i v i d u a l s could under any c o n d i t i o n s produce f e r t i l e o f f s p r i n g they belonged to the same species. T h i s view has long since been abandoned, because too many c l e a r l y d i s t i n c t species i n t e r -breed f r e e l y i n c e i p t i v i t y but not i n nature. R e l a t e d views are s t i l l h e l d by some workers, though. The e s s e n t i a l d i f f e r e n c e between the approach of the t r a d i t i o n a l s y s t e m a t i s t and that of the e x p e r i m e n t a l i s t i s t h a t the former works wi t h museum specimens which presumably r e f l e c t the behaviour of the animals i n nature, while the e x p e r i m e n t a l i s t s t u d i e s the behaviour of i n d i v i d u a l s d i r e c t l y i n the l a b o r a t o r y . S e v e r a l workers have s t u d i e d the behavioural and r e -productive r e l a t i o n s of various races of Peromyscus i n the l a b o r a t o r y (see Dice 1940, B l a i r 1954). Two approaches have 102. been u s e d — c o n f i n i n g a male of one form with a female of another; and c o n f i n i n g two p a i r s , one of each of tv/o forms, together. The f i r s t method permits determining i n t e r f e r t i -l i t y d i r e c t l y but does not present the animals w i t h a choice of mates. The second method permits them to s e l e c t a mate of the same or a d i f f e r e n t race, but does not permit p o s i -t i v e determination of i n t e r b r e e d i n g . Work i n t h i s f i e l d has shown that under the e x p e r i -mental c o n d i t i o n s the members of d i f f e r e n t species groups o f Peromyscus (as d i s t i n g u i s h e d by Osgood 1909) are com-p l e t e l y i n t e r s t e r i l e . No inter-group hybrids have been pro-duced. Two species i n the same species group may be com-p l e t e l y i n t e r f e r t i l e or may show reduced i n t e r f e r t i l i t y . I n s o c i a l i t y t e s t s , mice tend to choose mates of t h e i r own sp e c i e s . Subspecies of the same species i n t e r b r e e d f r e e l y , and show no s o c i a l d i s c r i m i n a t i o n . B l a i r (1947) reported crosses of oreas and P. m. bl a n -dus Osgood of New Mexico, but h i s oreas stocks were l a t e r determined by Dice (1949) t o be austerus. The measurements presented by Dice c l e a r l y place the animals i n t h i s r a c e , r a t h e r than i n oreas. Dalquest (1948) attempted without success to cross oreas and austerus, but he apparently had no c o n t r o l s . Dice (1949) bred stocks of Peromyscus from various l o -c a l i t i e s i n Washington i n h i s l a b o r a t o r y . Of h i s 16 st o c k s , 11 c o n s i s t e d e n t i r e l y of austerus; these a l l bred success-103. f u l l y . Two of h i s stocks c o n s i s t e d e n t i r e l y of oreas; these bred, but l e s s r e a d i l y . Two stocks a c c i d e n t a l l y con-t a i n e d both oreas and austerus. One of these did not breed at a l l , and i n the other only the austerus bred. One stock (Chinook Pass) a c c i d e n t a l l y contained both oreas and gambeli; i t d i d not breed. The mixed composition of these three stocks was not recqgnized u n t i l a f t e r the end of the exper-iment, and complete records are not a v a i l a b l e . Austerus i n t e r b r e d w i t h blandus, but oreas f a i l e d t o do so. Rece n t l y L i u (1954) has reported matings between oreas and P. m. g r a c i l i s (Le Conte) of the mid-west. These mat-ings u s u a l l y f a i l e d to produce o f f s p r i n g , and the o n l y hy-b r i d to reach adult age, a male, was s t e r i l e . Dice f e e l s t h a t because oreas and austerus occur t o -gether i n nature, apparently without i n t e r b r e e d i n g , and be-cause they f a i l e d t o int e r b r e e d i n the l a b o r a t o r y i t i s pro-bable t h a t there i s some kind of f e r t i l i t y b a r r i e r to t h e i r i n t e r b r e e d i n g . He suggests t h a t oreas and austerus may a c t u -a l l y "represent two d i f f e r e n t s p e c i e s , which i n t h i s r e g i o n do not i n t e r b r e e d , but whose ranges here p a r t l y o v e r l a p . Such a hypothesis could best be t e s t e d by making matings be-tween p o s i t i v e l y i d e n t i f i e d i n d i v i d u a l s of both forms" (1949, P.23). I n an attempt to c l a r i f y the re p r o d u c t i v e r e l a t i o n -s h i p s of oreas and maniculatus I have made a number of ex-perimental matings. The colony c o n s i s t e d i n i t i a l l y of 20 104. male oreas and 13 female oreas from Mount Seymour, 16 male and 12 female a r t e m i s i a e from Wright's Ranch, and nine male and 23 female austerus from Vancouver. The mice were kept i n wooden cages w i t h wood shavings on the f l o o r . Food (the standard mouse r a t i o n of the U n i v e r s i t y of B r i t i s h Columbia Animal N u t r i t i o n Laboratory) and water were provided at a l l times. The r a t i o n was o c c a s i o n a l l y supplemented by cod l i v e r o i l , beef l i v e r , or green vegetables. Most matlngs c o n s i s t e d of one male, a female of the same race, and a female of another r a c e , as f o l l o w s — male female female  austerus  a r t e m i s i a e  oreas a r t emi s iae  oreas  austerus Three r e p l i c a t i o n s of these matings were made, In so f a r as mice of the necessary race and sex were a v a i l a b l e . I n a d d i t i o n , a number of matings of s i n g l e males and females was made, In various combinations of r a c e s . The mice were trapped during August and September. One female artemisiae was pregnant when trapped i n August, but none of the other mice seemed to be i n breeding c o n d i -t i o n . Whitaker (1940) found that although P. leucopus did not breed during the winter under n a t u r a l c o n d i t i o n s , i t d i d oreas oreas austerus austerus a r t e m i s i a e a r t e m i s i a e 105. • breed when exposed to an a r t i f i c i a l 18-hour day. Breeding could be produced by l i g h t of i n t e n s i t y as low as one f o o t -candle power. A c c o r d i n g l y , I provided a r t i f i c i a l i l l u m i n a t i o n f o r 18 hours each day, from 3:00 AM u n t i l 9:00 PM. I l l u m i n a t i o n was by a 150-watt photoflood lamp, and was of three to ei g h t foot-candle power i n t e n s i t y measured at the tops of the cages.. P a r t of the i n t e r i o r of the cages was d i r e c t l y l i t , but most was i n shadow. The cages a l s o r e c e i v e d n a t u r a l i l l u m i n a t i o n through a small window i n the colony room. T h i s l i g h t i n g schedule was begun on October 25 and the i n i t i a l matings were made on November 9. By the end of November most of the females were i n breeding c o n d i t i o n , i n d i c a t e d by the open vagina, and the f i r s t l i t t e r was born, on December 11. One other l i t t e r was born that month, f i v e were born i n January, two i n February, and two i n March. The r e s u l t s of the experimental matings are given i n Table IV. Oreas f a i l e d to breed at a l l , so t h a t the e x p e r i -ment was of no value i n determining i t s reproductive r e l a -t i o n s w i t h maniculatus. Both austerus and artemisiae bred i n t e r se. Two female austerus produced young by a r t e m i s i a e males, one of them t w i c e . The hybrids appear to be f u l l y as v i a b l e as the o f f s p r i n g of s i n g l e - r a c e matings. One f e -male hyb r i d has produced young when backcrossed to an austerus male, and another when backcrossed to an a r t e m i s i a e male. Only two male hybrids were born. One died when 10 weeks o l d , 106. Table IV. L i t t e r s born i n Peromyscus colony, December 1957-' March 1958. • Female Male Mated L i t t e r Born L i t t e r S i z e ' a r t e m i s i a e 80 artemisiae 103 Nov 9 Jan 17 5 t» 178 tt 269 Ian 3 Jan 28 6 tt 250 tt 181 Nov 9 Dec 29 3 austerus 154 tt 269 Nov 11 Jan 8 3 it tt tt 181 Jan 3 Feb 5 1 ? tt 156 austerus 113 Nov 9 Jan 2 -tt 158 a r t e m i s i a e 249 Nov 9 Dec 11 4 n 298 «? — Jan 18 -a r t x aus 106 a r t e m i s i a e 243 Jan 17 Feb 27 5 tt tt t» tt tt Mar 28 5 tt 272 austerus 179 Jan 17 Mar 4 5 as a r e s u l t of an a c c i d e n t ; the other i s 12 weeks i old at the time of w r i t i n g . Neither male hybrid bred, but t h i s means nothing, i n view of t h e i r young age and the poor breed-i n g record of the colony. I n an attempt to stimulate breeding i n my stocks I gave a number of mice of each race i n j e c t i o n s of c h o r i o n i c gonadotropin i n February. The p r e p a r a t i o n used was "P.M.S.", No. 2224, f o r m e r l y produced by A y e r s t , McKenna and H a r r i s o n L t d . , of Montreal. I t was not p o s s i b l e to o b t a i n a f r e s h supply of t h i s p r e p a r a t i o n and a supply of unknown age and. d i l u t i o n was used i n s t e a d . Dosage used was 0.02 c c , which 107. would c o n t a i n 20 I n t e r n a t i o n a l U n i t s of gonadotropin i f d i -l u t e d according to i n s t r u c t i o n s . Recommended dosage f o r mink i s 50 u n i t s f o r females, 100 f o r males, so that t h i s dosage should be much more than needed f o r Peromyscus i f the p r e p a r a t i o n i s i n good c o n d i t i o n and d i l u t e d p r o p e r l y . Each mouse re c e i v e d three i n j e c t i o n s i n e i g h t days. Whereas almost a l l of the females had closed vaginas when i n j e c t i o n s were begun, almost a l l had open vaginas when examined at the time of the second or t h i r d i n j e c t i o n s , suggesting that the p r e p a r a t i o n had some e f f e c t . No preg-nancies were obtained as a r e s u l t of t h i s treatment, though. Two t r e a t e d females subsequently gave b i r t h to young, but so soon a f t e r treatment t h a t they must have been pregnant before the beginning of treatment. These l i m i t e d r e s u l t s suggest t h a t austerus and a r t e -misiae are completely i n t e r f e r t i l e and produce f e r t i l e hy-b r i d s . T h i s agrees with the r e s u l t s obtained by other work-e r s , mentioned above, who found f u l l i n t e r f e r t i l i t y between subspecies of the same s p e c i e s . I t a l s o i s i n accord w i t h the f i e l d data, which show intergra.dation of these races i n the Eraser Canyon. I cannot e x p l a i n the f a i l u r e of oreas to breed i n my colony. P o s s i b l e explanations are d i e t a r y d e f i c i e n c y , un-s a t i s f a c t o r y l i g h t i n g schedule, or un s u i t a b l e p s y c h o l o g i -c a l c o n d i t i o n s . Dice (1949) reported t h a t t h i s race bred i n h i s colony, but l e s s r e a d i l y than other r a c e s . S v i h l a (1936) reported on breeding i n caged mice i d e n t i f i e d as 108. oreas, but the measurements th a t he gives are those of aus-t e r u s . B l a i r ' s (1947) "oreas" a l s o were austerus, as men-tio n e d above. L i u (1954), who worked w i t h Dice's s t o c k s , s t a t e s t h a t the breeding record of oreas i n t h e i r laboratory-has been poor. I t seems that oreas's p r e r e q u i s i t e s f o r breeding are d i f f e r e n t from those of austerus and a r t e m i s i a e . The s i g n i f i c a n c e of l a b o r a t o r y breeding experiments t o the systematist i s questionable. Dice, B l a i r , and others have suggested t h a t experimental matings are the best t e s t of systematic r e l a t i o n s h i p , but I cannot agree with t h i s . The e x p e r i m e n t a l i s t goes too f a r when he attempts to supplant the accepted systematic c r i t e r i a by l a b o r a t o r y c r i t e r i a . A f t e r a l l , our species concept i s not an a r b i t r a r y one which we are f r e e t o define i n any way that we choose. To the evo-l u t i o n a r y b i o l o g i s t the species i s an Independent e v o l u t i o n -a r y u n i t (or lineage)(Simpson 1951). I f two races i n t e r b r e e d f r e e l y i n nature and produce f u l l y f e r t i l e o f f s p r i n g they are n e c e s s a r i l y e v o l v i n g as a u n i t and hence are c o n s p e c i f i c . I f they do not do t h i s they are not e v o l v i n g as a u n i t and t h e r e -f o r e are not c o n s p e c i f i c . The behaviour of i n d i v i d u a l s of these two races i n the l a b o r a t o r y r e a l l y has no d i r e c t bear-i n g on the problem. A l l o p a t r i c races cannot be judged by the c r i t e r i o n of i n t e r b r e e d i n g , and cases of c i r c u l a r over-l a p i n which two i n t e r s t e r i l e races are connected by other races w i t h which both are i n t e r f e r t i l e are another e x c e p t i o n . Laboratory s t u d i e s of t h i s k i n d are of value i n determining 109. the mechanisms r e s p o n s i b l e f o r r e p r o d u c t i v e i s o l a t i o n which has been demonstrated i n the f i e l d , but they cannot stand alone as systematic evidence. IV. DISCUSSION OF SYSTEMATIC RELATIONS The ranges of Peromyscus oreas and the adjacent sub-species of P. maniculatus overlap widely. •Oreas occurs from the eastern side of the Cascade Mountains and B r i t i s h Columbia Coast Range to the P a c i f i c Ocean, and from the lower Columbia R i v e r north at l e a s t to R i v e r s I n l e t , B.C. I n t h i s area i t i s absent only from the F r a s e r D e l t a of B r i t i s h Columbia and parts of the Puget Sound lowlands of Washington. Maniculatus occurs throughout Washington and B r i t i s h Columbia, except i n the highest p a r t s of the Cas-cades-Coast Range, the western part of the Olympic P e n i n s u l a , and perhaps parts of the B r i t i s h Colimibia coast. W i t h i n t h i s zone of overlap both species have been taken at many s t a t i o n s . At some s t a t i o n s both species and apparently intermediate i n d i v i d u a l s have been taken, sug-g e s t i n g t h a t these forms may h y b r i d i z e under c e r t a i n condi-t i o n s . No d e f i n i t e intergrade population has been found, but c e r t a i n samples suggest i n t e r g r a d a t i o n , e.g. those from Hope, Haney, and Loon Lake. The i n t e r p r e t a t i o n of such samples i s complicated by the f a c t that no two of them show the same c h a r a c t e r i s t i c s . I n both the Hope and Loon Lake samples the young mice are 110. f a i r l y uniform i n t a i l l e ngth and more-or-less intermediate between oreas and austerus, but adult t a i l measurements i n the Hope sample i n c l u d e the upper austerus range and the f u l l oreas range, while those i n the Loon Lake sample i n -clude the upper austerus range and o n l y the lower oreas range. At Hope s e v e r a l l o n g - t a i l , s h o r t - f o o t mice were taken, but at Loon Lake both l o n g - t a i l , s h o r t - f o o t and s h o r t - t a i l , long-foot mice were taken. The adult Pinewoods mice range from l o n g - t a i l a r t e m i s i a e t o l o n g - t a i l oreas, comparable to the Hope mice, but the d i s t r i b u t i o n of t a i l / body p o i n t s f o r the young i s not at a l l l i k e t h a t i n the Hope-./sample. No i n d i v i d u a l or p o p u l a t i o n can be c o n f i d e n t l y con-s i d e r e d of h y b r i d or i n t e r g r a d e o r i g i n at the present time, but i t seems probable that at l e a s t some of the intermediate specimens must be explained i n t h i s way. T h i s r a i s e s a problem of nomenclature. Races which h y b r i d i z e only r a r e l y i n nature are considered d i s t i n c t s p e c i e s , w h i l e races v/hich merge i n a zone of i n t e r g r a d a t i o n wherever they come i n con-t a c t are considered c o n s p e c i f i c . There i s every degree of intermediate c o n d i t i o n , though, and no r u l e i s a v a i l a b l e f o r i n t e r p r e t i n g them. The nomenclatural i n t e r p r e t a t i o n of v a r i -ous frequencies of h y b r i d i z a t i o n , and of i n t e r g r a d a t i o n i n some places but not i n others, must be made by each worker. The races of Peromyscus i n t e r a c t i n a v a r i e t y of ways, and any nomenclatural d e c i s i o n about some s i t u a t i o n s w i l l 111. n e c e s s a r i l y be a r b i t r a r y . Few cases of i n t e r g r a d a t i o n or h y b r i d i z a t i o n have been c a r e f u l l y analyzed. One of the best such analyses i s Sumner's (1929) study of i n t e r g r a -d a t i o n between two races of P. pol i o n o t u s (Wagner) i n F l o -r i d a . He found a narrow zone i n which most i n d i v i d u a l s were intermediate between the two races. Dice (1940) found a broad zone of i n t e r g r a d a t i o n between P. m. b a i r d i (Hoy and K e n n i c o t t ) and P. m. osgoodi Mearns i n North Dakota. I n t e r g r a d a t i o n was i r r e g u l a r and i n places the trend was reversed, but apparently most of the samples showed s i m i l a r v a r i a b i l i t y . Such i n t e r g r a d a t i o n i s known to occur between v a r i o u s of the races comprising the great complex of P. maniculatus, but some of the races apparently meet without i n t e r g r a d i n g . Dice (1931) r e p o r t s t h a t P. m. b a i r d i and P. m. g r a c i l i s occur together i n much of Michigan -without i n t e r b r e e d i n g , and Murie (1933) found P. m. osgoodi and P. m. a r t e m i s i a e l i v i n g i n the same area i n Montana without i n t e r m e d i a t e s . I n both cases the races are l a r g e l y e c o l o g i c a l l y i s o l a t e d , but there i s at l e a s t some d i r e c t contact between i n d i v i -duals of the two ra c e s . These races are considered conspe-c i f i c because they are thought to be connected by a s e r i e s of other races w i t h which they do i n t e r g r a d e . Apparent h y b r i d i z a t i o n between two species of the same species group has been described by McCarley (1954). P. l e u -copus and P. gossypinus meet i n many places over a vide f r o n t 112. from V i r g i n i a t o Texas. I n some areas no hybrids have been found, i n others o c c a s i o n a l hybrids occur, and i n at l e a s t one area h y b r i d i z a t i o n i s frequent. T h i s seems to be s i m i -l a r t o the r e l a t i o n s of oreas and maniculatus i n the North-west . Whatever the c o r r e c t i n t e r p r e t a t i o n of the apparent cases of h y b r i d i z a t i o n and i n t e r g r a d a t i o n between oreas and maniculatus, there i s no evidence t h a t these races have es-t a b l i s h e d a common gene pool or t h a t they are i n process of doing so. Instead, we f i n d t h a t although they are sympatric over l a r g e areas they s t i l l m a i ntain t h e i r r e s p e c t i v e iden-t i t i e s . Maniculatus i s d i v i d e d i n t o s e v e r a l geographic races which e x h i b i t some v a r i a t i o n w i t h i n themselves, but none of t h i s v a r i a t i o n i s c o r r e l a t e d with the presence or absence of oreas. Oreas i s q u i t e uniform throughout i t s range. I t seems de s i r e a b l e t o remove oreas from the species P. manicu-l a t u s and r e f e r to i t as P. oreas Bangs. D . ECOLOGICAL RELATIONS I . REGIONAL ENVIRONMENT 1. Topography The dominant topographic f e a t u r e of the P a c i f i c North-west i s the great chain of mountains that p a r a l l e l s the c o a s t . Between the Columbia R i v e r and the F r a s e r R i v e r i s the northern Cascade Range; north of the F r a s e r R i v e r i s the B r i t i s h Columbia Coast Range. Both ranges are of great 1 1 3 . geological and topographic complexity. The crest l i n e i s at 6000-8000 feet, while many peaks exceed 10 ,000 f e e t . Both ranges are up to 100 miles i n width. Low, narrow r i v e r v a l l e y s penetrate f a r into these ranges from east and west. On the B r i t i s h Columbia coast the mouths of these v a l l e y s are flooded by the sea, forming the numerous i n l e t s of that area. The lowest of the moun-t a i n passes are over 3000 feet i n elevation. The Columbia and Fraser Rivers have cut through the mountains, forming low-level corridors from the i n t e r i o r plateaus to the coast. The Cascades are bounded on the west by the lowlands of Puget Sound and the Fraser Delta, extending from the Co l -umbia River to Burrard I n l e t . North of here the B r i t i s h Columbia Coast Range descends almost d i r e c t l y into the sea, without an extensive border of lowlands. West of the Puget Sound lowlands i n southern Washington are low h i l l s , but farthe r north, west of Puget Sound i t s e l f , are the mountains of the Olympic Peninsula, lower than the Cascades but f u l l y as rugged. The Peninsula i s bordered by lowlands on a l l sides. To the east of the Cascades i n central and southern Washington i s the Columbia Plateau, r o l l i n g country of gen-e r a l l y l e s s than 2000 feet elevation. In northern Washing-ton and southern B r i t i s h Columbia are the Okanagan High-lands, r e l a t i v e l y low and rounded mountains which separate the Columbia Plateau from the i n t e r i o r plateaus of B r i t i s h 114. Columbia. These plateaus are mostly between 3000 and 5000 feet i n elevation. 2. Climate As would be expected i n an area of such topographic d i v e r s i t y , the climate of the Northwest shows, much regional and l o c a l v a r i a t i o n . In general, areas west of the mountains have mild, rainy climates while those east of the mountains have dry climates with temperatures lower i n winter and higher i n summer than on the coast. In the mountains the summers are short and cool, and winter snowfall i s heavy. Winter i s the time of maximum p r e c i p i t a t i o n , usually i n the form of r a i n on the coast, of snow i n the mountains and i n -t e r i o r . Summers are usually dry and sunny throughout the region except on the exposed coast, where r a i n may f a l l a l -most every day. 3. B i o t i c areas In keeping with the topographic and cli m a t i c diver-s i t y of the region, there i s a wide range of b i o t i c communi-t i e s , from the dense forests of the coast to the semi-arid grasslands of the i n t e r i o r . The occurrence of these commu-n i t i e s i s determined primarily by climate, secondarily by s o i l . The b i o t i c areas c l a s s i f i c a t i o n of Munro and Cowan (1947), a combination of the " b i o t i c province" and " l i f e zone" concepts, i s the most convenient c l a s s i f i c a t i o n of nat-u r a l communities available for the Northwest. Larrison (1946) 115. has c l a s s i f i e d the b i o t i c areas of Washington on a somewhat d i f f e r e n t b a s i s but w i t h comparable r e s u l t s . The termino-logy of Munro and Cowan i s used i n the f o l l o w i n g b r i e f des-c r i p t i o n of the b i o t i c areas i n which I have c o l l e c t e d . Puget Sound Lowlands B i o t i c Area T h i s i s the o n l y area of extensive lowlands i n the..region. I t i n c l u d e s the shores of Puget Sound and the S t r a i g h t of Georgia north to Burrard I n l e t and extends south from Puget Sound to the Co-lumbia R i v e r . On the d e l t a of the F r a s e r R i v e r i t penetrates i n t o the mountains to 100 m i l e s from the sea. The o r i g i n a l f o r e s t s were of western hemlock and western red cedar as c l i -max and Douglas f i r as subclimax ( s c i e n t i f i c names of p l a n t s are l i s t e d i n Appendix 4). These f o r e s t s have l a r g e l y been f e l l e d and replaced by open farmland or deciduous f o r e s t s of red a l d e r , broadleaf maple, vine maple, black cottonwood, western dogwood, and other t r e e s and shrubs. Wooded areas are c h a r a c t e r i z e d by dense underbrush. T h i s area has many species of p l a n t s and animals found nowhere e l s e i n the r e g i o n . Coast F o r e s t B i o t i c Area T h i s area i n c l u d e s the west-ern slopes of the mountains, extending t o the sea i n the n o r t h and i n t e r g r a d i n g with the Puget Sound Lowlands B i o t i c Area i n the south. I t shares many species w i t h t h a t area. The climate i s wetter and c o o l e r than i n the lowlands. C l i -max dominants are western hemlock and western red cedar. Dense undergrowth of s a l a l , Vaccinium spp., and Rubus spp. 116. may be present. I n Washington i s o l a t e d pockets of coast f o r e s t occur east of the summit. Subalpine F o r e s t B i o t i c Area T h i s area i s s i t u a t e d above the coast f o r e s t s of the west and the dry f o r e s t s of the i n t e r i o r , and below the a l p i n e meadows. I t grades com-p l e x l y i n t o a l l t h r e e . Temperatures are lower than at lower e l e v a t i o n s ; p r e c i p i t a t i o n i s high, and much of i t f a l l s as snow. On the coast mountain hemlock and y e l l o w cedar are dominant, but these species are replaced i n the i n t e r i o r by Engelmann spruce and a l p i n e f i r . Western white pine i s wide-spread but s c a t t e r e d . I n Washington western l a r c h and white f i r are common east of the summit. The f o r e s t s l a c k the dense understory of shrubs common i n the coast f o r e s t s . These f o r e s t s occupy extensive areas east of the c r e s t of the Coast Range. Dry F o r e s t B i o t i c Area T h i s area occupies the ea s t -ern slopes of the Cascade Mountains. I t s l o c a l r e l a t i o n s w i t h the subalpine f o r e s t depend l a r g e l y on exposure. The cli m a t e i s warmer than that of the subalpine area, and there i s l e s s p r e c i p i t a t i o n ; i n f a c t , t h i s area has the h o t t e s t summers and l e a s t p r e c i p i t a t i o n of any considered here. The conspicuous v e g e t a t i o n types are gra s s l a n d , pon-derosa pine, and Douglas f i r , i n order on i n c r e a s i n g wet-ness. The f o r e s t f l o o r i s u s u a l l y open, though s c a t t e r e d bushes o f t e n are present. 117. The above o u t l i n e i s a mere sketch of some of the more obvious b i o t i c f e a t u r e s of the r e g i o n . Montane areas always show great v a r i e t y of v e g e t a t i o n types, and i n t h i s r e g i o n f u r t h e r c o m p l i c a t i o n i s caused by the sharp c o n t r a s t between the very wet coast and the dry rain-shadow zone east of the mountains. Each of the mountain t r a n s e c t s t h a t I have made i s d i s t i n c t i v e , e s p e c i a l l y on the eastern slope of the moun-t a i n s where I have done most of my work. I have found coas-t a l b i o t i c types extending f a r t h e r east i n Washington than i n B r i t i s h Columbia. I I . HABITAT RELATIONS The f o l l o w i n g d i s c u s s i o n of Peromyscus h a b i t a t s i s based l a r g e l y on my own data because, w h i l e f a r from exhaus-t i v e , they are more d e t a i l e d than any other a v a i l a b l e to me. The f i e l d notes of most of the c o l l e c t o r s whose specimens I have examined have not been a v a i l a b l e , and those notes t h a t I have seen have t r e a t e d h a b i t a t only i n general terms. I t i s e s s e n t i a l f o r s t u d i e s such as t h i s to be able to asso-c i a t e a p a r t i c u l a r specimen w i t h a p a r t i c u l a r , c a r e f u l l y d e s c r i b e d , spot. Peromyscus i s found i n almost a l l t e r r e s t r i a l h a b i -t a t s i n the r e g i o n where I have c o l l e c t e d , but i t v a r i e s g r e a t l y i n abundance i n d i f f e r e n t h a b i t a t types. The sam-p l e s are too small to permit drawing d e t a i l e d c o n c l u s i o n s , but a general p i c t u r e emerges f a i r l y c l e a r l y . Random samp-118. l i n g would be meaningless f o r my purposes, and I have a t -tempted to t r a p i n a l l the p r i n c i p a l h a b i t a t s present, keep-i n g each t r a p l i n e w i t h i n one h a b i t a t type as much as p o s s i b l e . Peromyscus oreas has been found to be p a r t i a l l y i s o -l a t e d e c o l o g i c a l l y from P. maniculatus i n a l l the areas where I have found them sympatric. I t s r e l a t i o n s with gam-b e l i , a r t e m i s i a e , and austerus w i l l be considered, a f t e r which the p o s s i b l e governing mechanisms w i l l be dis c u s s e d . 1. oreas and gambeli These races occur together on the ea s t e r n s i d e of the Cascades i n southern Washington. P r e v i o u s r e p o r t s have con-t a i n e d l i t t l e i n f o r m a t i o n on t h e i r h a b i t a t d i s t r i b u t i o n i n the area. The authors b e l i e v e d that they i n t e r g r a d e d and t h e r e f o r e were not a l e r t to the p o s s i b i l i t y of d i f f e r e n t i a l h a b i t a t d i s t r i b u t i o n . C o l l e c t i n g that I d i d i n the r e g i o n showed t h a t the races overlap without i n t e r g r a d i n g , and t h a t they are i n part e c o l o g i c a l l y i s o l a t e d i n the zone of sym-p a t r y . I trapped along three highways, i n the zone of sym-pa t r y and both east and west of i t . These t r a n s e c t s w i l l be described i n order from south to north, from the westernmost t o the easternmost s t a t i o n s . The f i r s t t r a n s e c t was along the branch of State Route 5 running from White Pass to the Naches R i v e r , p a r a l l e l i n g the T i e t o n R i v e r most of the way. The h a b i t a t d i s t r i b u t i o n of mice on t h i s t r a n s e c t i s given i n Table V . A few t r a p s 119 Table V. Habitat r e l a t i o n s of P. oreas and P. m. gambeli i n the Tieton River v a l l e y , Washington. Traps Catch Lihe(Nights) o g ? tot Habitat ' Dog Lake, 4200 f e e t , 2 miles east of White Pass 24 20(1) 1 1 Western l a r c h dominant, i n semi-open stand; many logs, some bushes & herbs.  5 miles east of White Pass, 3800 feet 25 21(1) 2 2 Open stand of large ponderosa pine on steep h i l l , w/many.logs & much shrubbery, no grass. Clear Lake, 3300 feet, 8 miles east of White Pass 18 33(2) 3 3 Open stand of large ponderosa pine & Douglas f i r on steep h i l l w/grass, few shrubs & logs. 19 30(2) 1 5 1 7 Denser stand of Douglas f i r & subalpine f i r w/many logs but l i t t l e ground vegetation. 20 30(1) 14 14 Red cedar-western hemlock stand by creek w/abundant logs or ground vegetation. 21 23(1) 2 2 Mature stand of subalpine f i r etc. w/many logs & some ground vegetation. 22 24(1) 11 1 12 Red cedar-subalpine f i r stand by creek, w/many logs & some ground vegetation. 23 30(1) 5 1 6 Steep h i l l w/open stand of large Douglas f i r & some ponderosa pine & grass; part of l i n e i n subalpine f i r w/logs but l i t t l e ground vegetation. 170 33 9 2 44  River Bend, 2500 f e e t , 18 miles east of White Pass 16 56(1) 11 11 Along creek i n h i l l s ; open grassland, Douglas fir-ponder-osa pine stands, or dense bushes by creek. 17 48(2) 18 18 Douglas fir-ponderosa pine stand by r i v e r , w/thick undergrowth i n places. 104 29 29 120. set i n subalpine f o r e s t at Dog Lake (13) took one oreas. Traps set i n ponderosa pine f o r e s t three miles f a r t h e r east took two gambeli. T h i s was the westernmost stand of pon-derosa pine on the highway. The p r i n c i p a l s t a t i o n on t h i s t r a n s e c t was C l e a r Lake (16), a r e s e r v o i r on the T i e t o n R i v e r . A v a r i e t y of f o r e s t types were c l o s e l y a s s o c i a t e d here, i n c l u d i n g those charac-t e r i s t i c of the Coast F o r e s t , Subalpine F o r e s t , and Dry F o r e s t B i o t i c Areas. Dense stands of red cedar and western hemlock (Line 20, F i g . 39) were found w i t h i n a short d i s -tance of open stands of ponderosa pine ( L i n e 18, F i g . 40). These were the wettest and d r i e s t h a b i t a t s at t h i s s t a t i o n , and occupied only a s m a l l part of the area. Most of the area was occupied by mesic f o r e s t s of subalpine f i r and Douglas f i r (Line 19, F i g . 41; L i n e 21). The wet f o r e s t s had good ground cover, e i t h e r logs or low v e g e t a t i o n or both, while the dry f o r e s t s had very l i t -t l e . The mesic f o r e s t s c h a r a c t e r i s t i c a l l y were intermediate i n f o r e s t type and amount of ground cover. Only oreas was taken i n wet f o r e s t . One l i n e i n mesic f o r e s t took only oreas, the other took more gambeli than oreas. One l i n e i n dry f o r e s t took o n l y gambeli; the other took mostly oreas, probably because there was a dense p o p u l a t i o n of t h a t race i n wet f o r e s t 100 f e e t away (Line 22). E x t r a p o l a t i n g these r e s u l t s to the C l e a r Lake area as a whole, i t i s probable t h a t both races are widespread 121 Figure 40. Line 18, Clear Lake 122. F i g u r e 41. Line 19, C l e a r Lake F i g u r e 42. Line 17, R i v e r Bend 123. and. occur together i n most of the f o r e s t . They may be pre-sent i n s i m i l a r o v e r a l l d e n s i t i e s , but oreas occurs i n much greater l o c a l d e n s i t y . P o p u l a t i o n pressure i n f a v o r a b l e h a b i t a t s may f o r c e oreas out i n t o h a b i t a t s which i t other-wise would not occupy. The easternmost s t a t i o n on t h i s t r a n s e c t was. .at R i v e r Bend Camp, on the T i e t o n R i v e r . T h i s s t a t i o n was d e f i n i t e l y i n the Dry F o r e s t B i o t i c Area, with no montane f o r e s t types present. Gambeli was found i n greater numbers here than at Cl e a r Lake, and was e s p e c i a l l y common i n the dense shrubbery along streams ( F i g . 42). Trapping was not extensive enough to determine c l o s e l y the l i m i t s of d i s t r i b u t i o n of the two races on t h i s t r a n s e c t . W i t h i n two mil e s east of C l e a r Lake (3200 f e e t ) the montane f o r e s t types end completely and only dry f o r e s t types occur. T h i s probably marks the eastern l i m i t of oreas. Gambeli occurs to at l e a s t three m i l e s west of C l e a r Lake (3800 f e e t ) . The dry f o r e s t s extend l i t t l e i f any f a r t h e r west than t h i s and t h i s probably i s the western l i m i t of gambeli. The zone of sympatry seems to be no more than f i v e m i l e s wide i n t h i s v a l l e y , and to cover a v e r t i c a l d i stance of l i t t l e more than 600 f e e t . The next t r a n s e c t was about 25 m i l e s f a r t h e r n o r t h . I t f o l lowed the American and Naches R i v e r s along U. S. Route 410. Dice (1949) r e p o r t s t h a t both oreas and gambeli were trapped at Lodgepole Camp (4500 f e e t ) , s i x m i l e s east of 124. Chinook Pass. They were taken i n " f a i r l y dense second-growth forest of lodgepole pine, tamarack, white pine, spruce, and a few Douglas f i r " (p.3). My westernmost st a -t i o n was at Pleasant Valley (18), where I took 17 oreas and one animal of questionable i d e n t i t y (Table VT). The vege-t a t i o n here was more dense than at Lodgepole Camp, and Douglas f i r was the most abundant species. The h i l l s north of the v a l l e y were d r i e r , and may have been occupied by gambeli. The next s t a t i o n was American Forks (17), where the American and Bumping Rivers j o i n to form the Naches River. This area was selected for trapping because i t included a va r i e t y of habitats, s i m i l a r to those of the Subalpine For-est and Dry Forest B i o t i c Areas. Line 38 was near the f o r k s . A few traps set i n camp i n t h i s area took two oreas and two gambeli i n f i v e nights, i n addition to those l i s t e d i n the table. Lines 44 and 45 were on the American River two miles west of the forks. Line 42 was on the Bumping River one mile south of the forks. The other l i n e s were on the Naches River below the f o r k s — L i n e 40 -| mile east, Line 39 one mile east, Line 43 just east of Line 39, and Line 41 two miles east of the f o r k s . One l i n e yielded no Peromyscus; a l l but one of the others yielded both oreas and gambeli. Cottonwood Camp (15), the easternmost s t a t i o n , was on the Naches River i n the Dry Forest B i o t i c Area. Open Doug-1 2 5 . Table V I . H a b i t a t r e l a t i o n s of oreas and gambeli i n the American and Naches R i v e r v a l l e y s , Washington.  Traps Catch L i n e ( N i g h t s ) o g ? t o t Habitat Pleasant V a l l e y , 33GO f e e t 34 36(1) 4 4 35 14(1) 2 2 36 5(1) 1 1 B ( l ) 2 2 14 (1 ) 0 37 22(1) 8 1 9 99 17 1 18 unerican F o r k s , 2800 f e e t . 38 56(1) 11 1 12 16(1) 4 1 5 39 19(1) 4 2 6 42(2) 40 40(1) 0 41 37(1) 5 5 7 (1 ) 1 5 6 42 33(1) 6 6 18(1) 1 1 43 31(1) 2 2 4 44 19(1) 4 4 45 49(1) 3 2 5 367 31 23 54 , 19 m i l e s east of Chinook Pass Open stand of lodgepole pine, Doug-l a s f i r , western l a r c h , w/good ground cover of logs & bushes; on gentle slope £ m i l e from r i v e r . Mature Douglas f i r stand, w/many l o g s ; i n places dense w/o ground v e g e t a t i o n , i n places open w/good herb cover. Thick bushes i n c l e a r i n g by r i v e r . I n or at edge of f o r e s t by r i v e r . Large meadow by r i v e r . Engelmann spruce woods by r i v e r , w/many logs & i n places t h i c k bushes. 8 m i l e s east of Pleasant V a l l e y Mature grand f i r , western l a r c h , red cedar on f l o o d p l a i n ; l o g s abundant, ground v e g e t a t i o n sparse, Douglas f i r stand s i m i l a r to above but f a r t h e r from r i v e r . From r i v e r bank to t e r r a c e 50 f e e t above r i v e r , w/grand f i r , Douglas f i r , ponderosa pine most common; good ground cover i n p l a c e s . Terrace £ mile from r i v e r , w/open ponderosa pine-grass & denser grand f i r stands; some ground v e g e t a t i o n & l o g s . Base of t a l u s slope 100 f e e t from r i v e r . S cattered v e g e t a t i o n on r i v e r bank, Grand f i r - r e d cedar stand on r i v e r bank, w/many l o g s , l i t t l e ground v e g e t a t i o n . Small t a l u s slope on dry h i l l s i d e 100 f e e t from r i v e r . Garbage dump i n open Douglas f i r -grand f i r - p o n d e r o s a pine stand. Steep dry h i l l w/grand f i r , Doug-l a s f i r , some ponderosa pine, l i t t l e ground cover. Below Line 44 by r i v e r ; grand f i r dominant, w/Douglas f i r , cedar, l a r c h ; good logs or bushes. 126. Table V I , cont'd Traps Catch Lin e (Nights) o _g' ? t o t H a b i t a t Cottonwood Camp, 2300 f e e t , 12 m i l e s east of American Fork s 32 30(1) 2 2 Open stand of l a r g e ponderosa pine, Douglas f i r , black c o t t o n -wood on r i v e r bank, w/dense bushes i n places but few l o g s . 33 8(1) 0 R i v e r bank w/scattered t r e e s , shrubs, r o c k s , l o g s . 17(1) 0 Wide f l a t area between r i v e r & h i l l s , w/scattered ponderosa pine , some logs & bushes, much grass. 21(1) 2 2 Steep h i l l w/good cover of s m a l l Douglas f i r & Douglas maple, some l o g s , l i t t l e undergrowth. 76 4 4 l a s f i r - p o n d e r o s a pine stands and g r a s s l a n d were c h a r a c t e r -i s t i c of the s t a t i o n , with f a i r l y dense deciduous shrubbery and a few black poplar along the r i v e r . Four gambeli were taken here, i n the more h e a v i l y vegetated s i t e s . The t r a n s i t i o n between mountain and i n t e r i o r b i o t a i s l e s s abrupt on t h i s t r a n s e c t than on the previous one and the zone of sympatry of oreas and gambeli i s correspondingly w i d e r — a t l e a s t 20 m i l e s , and 1700 f e e t v e r t i c a l l y . The l o c a l e c o l o g i c a l c o n t r a s t s are a l s o l e s s marked here, n e i -t h e r coast f o r e s t nor f u l l y t y p i c a l dry f o r e s t being present near American F o r k s . The two races of Peromyscus are p a r t i -a l l y e c o l o g i c a l l y i s o l a t e d here, but l e s s markedly so than at C l e a r Lake. Oreas was somewhat more common i n the wetter s i t e s , gambeli i n the d r i e r ones. The most northern t r a n s e c t i n Washington was IT. S. Route 10, p a r a l l e l i n g the Yakima R i v e r 20 m i l e s north of 1 2 7 . Route 4 1 0 . The f o r e s t s at C r y s t a l Springs were s i m i l a r to those of the Coast F o r e s t B i o t i c Area; only oreas was trapped here (Table V I I ) . The other s t a t i o n on t h i s t r a n -sect was on the north side of the Yakima R i v e r near Easton ( 1 9 ) . The f o r e s t here was t r a n s i t i o n a l between mountain and i n t e r i o r types; much of i t had been cut over and r e -placed by e a r l y s u c c e s s i o n a l stages or plowed f i e l d s . I took one oreas and 13 gambeli here, but another c o l l e c t o r took f i v e oreas and three gambeli near Easton. Table V I I . H a b i t a t r e l a t i o n s of oreas and gambeli i n the Yakima R i v e r v a l l e y , Washington.  Traps Catch  Line (Nights) o g ? t o t H a b i t a t  C r y s t a l Springs, 2300 f e e t , 11 mi east Snoqualmie Pass 26 25 (1 ) 21 21 Mature stand of western hemlock w/some red cedar & grand f i r by r i v e r ; many l o g s , l i t t l e ground v e g e t a t i o n . 27 25(1) 13 13 By r i v e r , grand f i r dominant, w/ some Douglas f i r , western hem-l o c k , red cedar; most places w/ lu s h ground v e g e t a t i o n , many w/ l o g s . 50 34 34 E a s t o n , 2200 f e e t , 10 mi east C r y s t a l Springs 28 30(1) 6 6 Logged t e r r a c e high above r i v e r , w/many logs & much ground vege-t a t i o n . 6(1 ) 1 1 F o r e s t e d h i l l s i d e (Douglas f i r ) . . 15(1) 3 3 F l o o d p l a i n i mile from r i v e r , mixed c l e a r i n g s & t r a n s i t i o n f o r e s t . 29 12(1) 1 3 4 Along road i n Douglas f i r stand near r i v e r , w/some logs & bushes. 12(1) 0 In center of same f i r stand, w/ ^ many logs but few bushes. 75 5713 14 128. S u p e r f i c i a l study of the f o r e s t s of the Yakima R i v e r v a l l e y suggests t h a t the zone of sympatry of these two races i s narrow. The Dry F o r e s t B i o t i c Area begins j u s t east of Easton, and the subalpine f o r e s t extends east almost to Easton. T h i s i s an o v e r s i m p l i f i c a t i o n , because on t h i s t r a n s e c t there i s a more uniform, gradual change i n f o r e s t t ype, r a t h e r than a complex i n t e r m i x t u r e of d i s t i n c t t y p e s . The zone of sympatry probably i s at l e a s t s e v e r a l m i l e s wide. Both races were taken at 2200 f e e t , o n l y oreas at 2300 f e e t . I n summary, oreas and gambeli are sympatric on the eastern side of the Cascades i n a zone v a r y i n g from s e v e r a l t o at l e a s t 20 m i l e s wide. I n the T i e t o n R i v e r v a l l e y a wide range of diverse f o r e s t types occur i n a s m a l l area and the change from montane to i n t e r i o r f o r e s t s i s f a i r l y abrupt. Gambeli was taken as f a r west as f i v e m i l e s from the summit, at 3800 f e e t e l e v a t i o n ; oreas was taken as f a r east as eight m i l e s from the summit, at 3300 f e e t . The h o r i z o n t a l o v e r l a p t h e r e f o r e i s at l e a s t three m i l e s , the v e r t i c a l o verlap at l e a s t 500 f e e t . Because of the d i s t r i b u t i o n of f o r e s t types i t i s u n l i k e l y t h a t the races extend much be-yond these l i m i t s . I n the American R i v e r v a l l e y f o r e s t t r a n s i t i o n i s more gradual. Gambeli apparently extends west to at l e a s t w i t h i n s i x m i l e s of the summit, at 4500 f e e t e l e v a t i o n , though i t may be absent from some areas f a r t h e r east ( P l e a -sant V a l l e y ) . I n the Naches R i v e r v a l l e y below the f o r k s 129. oreas was c o l l e c t e d as f a r east as 27 m i l e s from the summit, at 2800 f e e t . The h o r i z o n t a l overlap here then i s over 20 m i l e s , and the v e r t i c a l o v e r l a p at l e a s t 1700 f e e t . A v a i l -able i n f o r m a t i o n does not permit e s t i m a t i n g the o v e r l a p i n the Yakima R i v e r v a l l e y . Both races were taken at 2200 f e e t , 21 miles from the summit, and i t i s probable that n e i t h e r race extends f a r beyond t h i s p o i n t . On the T i e t o n R i v e r oreas probably does not occur below 3000 f e e t nor gambeli above 4000 f e e t . On the Naches R i v e r oreas occurs as low as 2800 f e e t but probably not lower than 2500 f e e t ; gambeli occurs at l e a s t to 4500 f e e t . On the Yakima R i v e r both races occur at 2200 f e e t , oreas probably not below 2000 f e e t nor gambeli above 2500 f e e t . In other words, the zone of v e r t i c a l overlap may be at en-t i r e l y d i f f e r e n t a l t i t u d e s i n areas t h a t are c l o s e together. The common f a c t o r of the zone of overlap i n each of these v a l l e y s i s the occurrence of mixed or i n t e r g r a d i n g montane and i n t e r i o r f o r e s t , and both races are found wherever these cord i t i o n s occur. The occurrence of such f o r e s t s i s deter-mined by a complex of c l i m a t i c and edaphic c o n d i t i o n s which vary w i t h the geology and topography of the area. I t usu-a l l y was p o s s i b l e to p r e d i c t which races would be found at a s t a t i o n , but i t o f t e n was not p o s s i b l e to do t h i s f o r each t r a p l i n e . The f a c t o r s determining l o c a l d i s t r i b u t i o n proved t o be too complex f o r such c a s u a l a n a l y s i s . 130. 2. oreas and art e m i s i a e The geographic and e c o l o g i c a l r e l a t i o n s of these races are s i m i l a r to those of oreas and gambeli. Artemisiae r e -places gambeli i n northern Washington and southern B r i t i s h Columbia, but i t i s m o r p h o l o g i c a l l y and e c o l o g i c a l l y e q u i -v a l e n t . The only t r a n s e c t made through the oreas-artemisiae r e g i o n was along the Hope-Princeton Highway i n southern B r i t -i s h Columbia. At s e v e r a l s t a t i o n s an attempt was made t o determine the r e l a t i v e abundance of Peromyscus i n var i o u s h a b i t a t s by f o l l o w i n g a standard t r a p p i n g procedure. Nine t r a p l i n e s were l a i d out at each s t a t i o n , s i x (I-YI) c o n s i s t i n g of 10 t r a p s i t e s spaced 50 f e e t apart and three (VII-IX) of f i v e t r a p s i t e s spaced 25 f e e t a p a r t . Two t r a p s were s e t at each s i t e . Each l i n e was set e n t i r e l y w i t h i n one uniform h a b i t a t t ype, and a l l the p r i n c i p a l types at each s t a t i o n were sam-p l e d . Each s t a t i o n was trapped f o r two n i g h t s i n e a r l y J u l y and two n i g h t s i n e a r l y August of 1956. The r e s u l t s are given i n Tables V I I I - X I . The t r a n s e c t f o l l o w e d the course of the Similkameen R i v e r , which flows l a r g e l y from south t o north, r a t h e r than west to east. The mountains t r e n d roughly north-north-west here, so tha t the t r a n s e c t cuts through them at perhaps a 45° angle. There i s a change from Subalpine F o r e s t to Dry F o r e s t B i o t i c Areas along the highway, but i t i s i r r e g u l a r , i n f l u e n c e d by height above the r i v e r and presence of o l d 131. "burns. Oreas occurs i n the mountains west of the r i v e r , and the populations along the t r a n s e c t probably are con-tinuous v/ith those of the adjacent mountains more than w i t h populations i n other parts of the v a l l e y . T h i s species pro-bably does not occur east of the Similkameen-Pasayten R i v e r s . The true width of the zone of sympatry cannot be de-termined from t h i s t r a n s e c t . The races were taken together along more than 40 m i l e s of highway, but the zone of sympatry cannot be ne a r l y t h i s wide. At the l a t i t u d e of Pinewoods i t must be between f i v e and 10 m i l e s wide. Oreas occurs as low as 2800 f e e t , a r t e m i s i a e as high as 4000 f e e t , g i v i n g a zone of v e r t i c a l overlap of at l e a s t 1200 f e e t . The westernmost s t a t i o n was at A l l i s o n Pass (36), at 4402 f e e t on the Cascade summit. The mountains r i s e t o over 6000-feet above the pass. T r a p l i n e s were set along the h i g h -way from two m i l e s west of the pass to two mile s east of i t , at e l e v a t i o n s of 4300-4400 f e e t . The s t a t i o n was i n the Subalpine F o r e s t B i o t i c Area. A l p i n e f i r , subalpine f i r , and Engelmann spruce were climax, with Douglas f i r and lodge-pole pine as pioneer s p e c i e s . At the western end of the s t a -t i o n was a larg e burn with much bare s o i l and only s c a t t e r e d low v e g e t a t i o n . Peromyscus was taken on a l l nine t r a p l i n e s a t t h i s s t a -t i o n (Table V I H ) . The catch c o n s i s t e d of 26 oreas and one animal of questionable i d e n t i t y . H a b i t a t s trapped i n c l u d e d moist subalpine f o r e s t , dry open lodgepole pine f o r e s t , a 132 Table V I I I . H a b i t a t d i s t r i b u t i o n of Peromyscus at A l l i s o n Pass. Trap- Catch Line n i g h t s o a ? t o t H a b i t a t I 80 4 4 Old burn on open h i l l s i d e , vegeta-t i o n sparse, some l o g s , s o i l eroded & dry. I I 80 3 3 Subalpine fir-Engelmann spruce stand on steep slope near Line I ; l i t t l e ground v e g e t a t i o n . I I I 80 1 1 Lodgepole pine stand w/dense dwarf vaccinium, no l o g s . IV 80 8 1 9 Lodgepole pine stand w/dwarf vac-cinium & abundant s m a l l l o g s . V 80 3 3 A l p i n e f i r dominant; good ground cover of logs & v e g e t a t i o n . VI 80 2 2 Stand o f large Engelmann spruce & a l p i n e f i r on f l o o d p l a i n ; good cover of logs & bushes. V I I 40 1 1 T a l u s s l i d e , almost devoid of ve g e t a t i o n . V I I I 40 3 3 Open stand of l a r g e Engelmann sprue by stream, w / l i t t l e ground cover. IX 40 1 1 Narrow r a v i n e w7/creek, marsh, a l -pine f i r , Engelmann spruce. 600 26 1 27 t a l u s s l i d e , and an open burn. Ground cover v a r i e d from almost none to abundant v e g e t a t i o n and l o g s . S o i l s included p r i n c i p a l l y shallow h i l l s i d e podsols and t h i c k e r a l l u v i a l s o i l s of stream v a l l e y s . Both the highest and lowest catches were made i n stands of lodgepole pine. The p r i n c i p a l d i f f e r e n c e between these two stands was that the one w i t h the high catch of Peromys-cus (Line IV) had many logs s e v e r a l inches i n diameter, while the other (Line I I I ) had few l o g s . A l l other l i n e s y i e l d e d so few animals t h a t the d i f f e r e n c e s between them are not s i g -n i f i c a n t . E c o l o g i c a l data are not a v a i l a b l e f o r Smith's c o l -l e c t i o n . 133. The one oreas and one art e m i s i a e from C o l d s p r i n g Camp were trapped i n a ten t p i t c h e d i n lodgepole pine-Engelmann spruce woods near a r i v e r . The i d e n t i t y of the mice from Pinewoods (39) i s not c e r t a i n . T h i s sample was c o l l e c t e d i n predominantly lodge-pole pine woods. The mice from Cambie Camp were trapped i n open pine woods a few yards from a r i v e r . Almost no ground cover was present, but undisturbed lodgepole pine-Engelmann spruce woods extended t o w i t h i n 100 f e e t of the area. The other mice were trapped at the Ranger S t a t i o n , on a gentle slope \ m i l e from the r i v e r . At Goodfellow Creek (40) oreas c o n s t i t u t e d the major part of the catch, but there was a l s o a l a r g e catch of a r t e -misiae (Table I X ) . T h i s s t a t i o n extended from s i x to eight m i l e s northeast of Pinewoods, i n the v a l l e y of the S i m i l k a -meen R i v e r . The r i v e r i s at 3400 f e e t e l e v a t i o n , and the h i l l s on e i t h e r side reach about 5400 f e e t . Traps were set at 3600-3700 f e e t . The gradient of the r i v e r i s low, and the r i v e r meanders from side t o side of i t s v a l l e y . The v a l -l e y f l o o r i s 5 to J mile wide. T h i s area i s t r a n s i t i o n a l between the Subalpine F o r e s t and Dry F o r e s t B i o t i c Areas. Douglas f i r and Engelmann spruce f o r e s t occupies the wettest of the lowlands along the r i v e r and the more s h e l t e r e d s i t e s on the h i l l s i d e s . Lodge-pole pine dominates the d r i e r p a r t s of the v a l l e y bottom, and occurs mixed w i t h other species on most s i t e s . The d r i e s t 134. Table IX. H a b i t a t d i s t r i b u t i o n of Peromyscus at Goodfellow Creek.  Trap- Catch Line n i g h t s o a ? t o t H a b i t a t I SO 2 1 3 Dry open lodgepole pine woods by r i v e r ; l i t t l e ground cover, s o i l hard. I I 80 1 7 8 Douglas f i r - l o d g e p o l e pine-ponder-osa pine woods on h i l l s i d e ; some' ground cover of logs & v e g e t a t i o n . I l l 80 5 3 8 Douglas f i r - l o d g e p o l e pine f o r e s t on h i l l s i d e , w/grass, herbs,logs. IV 80 13 13 M o i s t s i t e by r i v e r , w/Engelmann spruce, lodgepole p i n e , & dense undergrowth. V 80 5 5 10 Lodgepole pine-Douglas f i r - E n g e l -mann spruce f o r e s t on h i l l s i d e , w/ l i t t l e ground v e g e t a t i o n but many lo g s . VI 80 4 4 Lodgepole pine-Douglas f i r - E n g e l -mann spruce f o r e s t by r i v e r , w/ l i t t l e ground cover, s o i l sandy. V I I 40 0 Small f l a t dry meadow. V I I I 40 6 6 Open stand of black poplar & E n g e l -mann spruce by r i v e r ; l i t t l e ground cover, but denser v e g e t a t i o n nearby. IX 40 4 1 5 Talus slope w/some juni p e r & poplar. c"0T> Jc~20 I 57 h i l l s i d e s i t e s are occupied by Douglas f i r - p o n d e r o s a pine f o r e s t . T h i s i s the westernmost occurrence of ponderosa pine on t h i s t r a n s e c t . Three t r a p l i n e s took only oreas, i n c l u d i n g the l i n e w i t h the greatest t o t a l catch (Line I V ) . T h i s l i n e was i n a r e l a t i v e l y moist s i t e near the r i v e r , w i t h dense under-growth. P a r t of the l i n e had much l e s s undergrowth than the r e s t , but y i e l d e d f u l l y as many Peromyscus. Both of the other l i n e s which y i e l d e d only oreas (Lines VI and V I I I ) also were near the r i v e r , but had r e l a t i v e l y sparse ground cover. 135. L i n e I I , on a t h i n l y wooded h i l l s i d e with l i t t l e ground cover, took a..large m a j o r i t y of a r t e m i s i a e . L i n e DC, on a t a l u s s l o p e , produced four a r t e m i s i a e and an un-i d e n t i f i a b l e i n d i v i d u a l . Three l i n e s took approximately equal numbers of both r a c e s . The two oreas and one a r t e m i s i a e from Line I were taken at s i m i l a r s i t e s . On L i n e I I I three oreas and three a r t e m i s i a e were taken at the same t w o . s i t e s , the s i t e s w i t h almost the greatest amount of l o g cover on the l i n e . I n a d d i t i o n , two oreas were taken a t a s i t e w i t h no l o g s , but w i t h a l i t t l e brush and ground v e g e t a t i o n . The s i t e with more logs than any other y i e l d e d no Peromyscus. On L i n e V both races were a s s o c i a t e d with abundant l o g s , but i t i s not p o s s i b l e to d i s t i n g u i s h h a b i t a t d i f f e r e n c e s between the r a c e s . At Copper Creek (41) the Similkameen R i v e r flows n o r t h and the character of i t s v a l l e y has changed, becoming deeper and narrower with l i t t l e f l o o d p l a i n . The only f l a t l a n d i s at the mouths of the l a r g e r t r i b u t a r y creeks. The subalpine elements of the v e g e t a t i o n are f u r t h e r reduced and the dry f o r e s t elements more prominent. T r a p l i n e s I , I I I , and VII-BC were lo c a t e d near the mouth of Copper Creek, a.t about 3100 f e e t e l e v a t i o n . L i n e s I I and IV were l o c a t e d h i g h above the r i v e r (3600 f e e t ) two miles north of Copper Creek. Lines V and VI were l o c a t e d at Sunday Summit, three m i l e s f a r t h e r north at 4200 f e e t . Sunday Summit i s i n an extensive area of d i s c l i m a x lodgepole pine f o r e s t . 136. The t r a p s at Copper Creek took 29 a r t e m i s i a e and f i v e oreas (Table X ) . A l l l i n e s took a r t e m i s i a e , but the oreas a l l were taken on one l i n e . T h i s Line (No. V I I ) , which was the most moist and most densely vegetated at t h i s s t a t i o n , had much the highest y i e l d per t r a p n i g h t of a l l l i n e s . The two species were taken i n approximately equal numbers here. The f i v e t r a p s i t e s on t h i s l i n e were much a l i k e , and the records show no d i f f e r e n c e s between the species i n d i s t r i b u -t i o n on t h i s l i n e . Table X. Ha b i t a t d i s t r i b u t i o n of Peromyscus at Copper Creek and Sunday Summit.  Trap- Catch L i n e n i g h t s o a. ? t o t H a b i t a t I 80 10 10 Open lodgepole pine stand w/some bushes & many s m a l l l o g s , on dry t e r r a c e above r i v e r . I I 80 5 5 Open Douglas f i r - l o d g e p o l e pine-ponderosa pine f o r e s t w/grass & a few l o g s ; one end by stream. I l l 80 3 3 Douglas f i r f o r e s t w/some E n g e l -mann spruce & lodgepole p i n e , by r i v e r ; much low v e g e t a t i o n & lo g s , IV . 80 3 3 Douglas f i r - l o d g e p o l e pine stand h i g h above r i v e r , w/logs & dense gr a s s . Mature lodgepole pine f o r e s t w/ much grass, bushes, l o g s , s l a s h . Dense stand of lodgepole pine s a p l i n g s . By creek between o s i e r t h i c k e t & meadow of dense grass. Mature EngeLmann spruce-black pop-l a r stand by r i v e r , w / l i t t l e ground v e g e t a t i o n . Meadow on t e r r a c e above r i v e r . V 80 0 VT 80 1 1 V U 40 5 7 12 V I I I 40 6 6 IX 40 3 3 600 5 38 43 137. Line I , the next most productive, was i n a dry lodge-pole pine stand w i t h l i t t l e cover except many l o g s . L i n e s I I I and V I I I were s i t u a t e d c l o s e together. L i n e H I had much more ground cover, but produced o n l y one^quarter as many Peromyscus per t r a p - n i g h t ; Line V I I I was on the r i v e r bank. The two l i n e s ( I I and IV) two m i l e s north of Copper Creek took eight Peromyscus, a l l a r t e m i s i a e . Traps set near a s m a l l stream were more s u c c e s s f u l than others. One of the l i n e s a t Sunday Summit took no Peromyscus at a l l ; the other, i n d r i e r and more barren h a b i t a t , took one a r t e m i s i a e . Seven a r t e m i s i a e and two oreas were taken at Tupper's M i l l (42), s i x m i l e s north of Sunday Summit and 10 m i l e s south of P r i n c e t o n . T h i s s t a t i o n i s near the r i m of the Similkameen canyon, at 3700 f e e t e l e v a t i o n . Douglas f i r and lodgepole pine were the most abundant t r e e s , though patches of ponderosa pine a l s o were present. The two oreas were taken i n moist s i t e s , one i n an a l d e r t h i c k e t along a creek, the other i n a dense Douglas f i r stand on the n o r t h - f a c i n g slope of a deep r a v i n e , a l s o near a creek. The seven a r t e -misiae were taken i n open Douglas f i r - l o d g e p o l e pine woods, on a rock s l i d e , and i n a camp. Both oreas and artemisiae were taken at Wright's Ranch (43), three miles southwest of P r i n c e t o n at 2800 f e e t . The ranch i s i n a broad area of low r e l i e f between the mountains and the deep v a l l e y s of the Similkameen and Tulameen R i v e r s . 138. I t i s i n the Dry F o r e s t B i o t i c Area, but near i t s western l i m i t . Four p r i n c i p a l h a b i t a t types are p r e s e n t — o p e n grass-l a n d , ponderosa pine, Douglas f i r , and Engelmann spruce, i n order of i n c r e a s i n g wetness. The f i r s t three types each oc-cupy l a r g e areas, but Engelmann spruce i s confined to a few s h e l t e r e d s i t e s such as n o r t h - f a c i n g r a v i n e s . E c o l o g i c a l segregation of the two species of Peromys-cus was complete on the o r i g i n a l t r a p l i n e s (Table X I ) . F i v e l i n e s y i e l d e d only a r t e m i s i a e , one only oreas, and three no Peromyscus at a l l . The d i s t r i b u t i o n of oreas was much more Table X I . H a b i t a t d i s t r i b u t i o n of Peromyscus at Wright's Ranch.  Trap- Catch  Line n i g h t s o a ? t o t Hab i t a t  I 80 1 1 Immature ponderosa pine, w/few shrubs & l o g s , sparse g r a s s . I I 80 10 10 Large r a v i n e w/Engelmann spruce & aspen, dense shrub l a y e r of o s i e r & a l d e r , some l o g s . I l l 80 0 Open grassland on h i l l , grass very sparse. IV 80 4 4 Mature Douglas f i r on h i l l , l i t t l e ground v e g e t a t i o n , good brush & l o g s . V 80 2 2 Open lodgepole pine stand w/some Douglas f i r on dry f l a t ground. VI 80 1 1 Ponderosa pine w/grass, some l o g s , few shrubs. V I I 40 0 Aspen grove by creek, w/grass & low bushes, few l o g s . V I I I 40 4 4 Sagebrush, bunchgrass, & bare ground on h i l l s i d e . LX 40 0 Aspen, gra s s , a few bushes at edge of pond, w/few l o g s . 600 10 12 0 22 139. r e s t r i c t e d than t h a t of a r t e m i s i a e , but on the one l i n e on which i t was found oreas occurred i n greater d e n s i t y than d i d a r temisiae on the other l i n e s . Line I I y i e l d e d 10 oreas i n 80 t r a p n i g h t s , while the l i n e s on which artemisjae was taken y i e l d e d only 12 animals i n 360 t r a p n i g h t s . The l i n e on which oreas was taken had much the best cover of any at t h i s s t a t i o n . The other l i n e s were l a r g e l y l a c k i n g i n good cover, but some were not conspicuously poorer i n t h i s respect than some h a b i t a t s which y i e l d e d oreas at other s t a t i o n s . The l i n e which produced the g r e a t e s t number of a r t e -m i s i a e per t r a p n i g h t (Line V I I I ) was l o c a t e d on a sagebrush-covered h i l l s i d e . T h i s h a b i t a t was dry and barren, and the s o i l was hard and without organic matter. Apparently the dense but s c a t t e r e d cover o f f e r e d by the sage i s f a v o r a b l e t o these mice. One of the l i n e s on which no Peromyscus was taken was on an over-grazed grassy h i l l s i d e , devoid of food and cover. The two other l i n e s y i e l d i n g no Peromyscus were w i t h i n a few f e e t of open water and o f f e r e d a c e r t a i n amount of ground cover. T h i s s t a t i o n provided the most c l e a r - c u t example of e c o l o g i c a l i s o l a t i o n between oreas and maniculatus that was encountered i n the p r e l i m i n a r y t r a p p i n g . I t seemed d e s i r -a ble t h e r e f o r e t o give f u r t h e r a t t e n t i o n t o the r e l a t i o n s between the two species here. During the next summer two 140. weeks was spent t r a p p i n g i n t h i s area, w i t h most of the work concentrated on the spruce r a v i n e ( s i t e of Line I I ) and the iu r r o u h d i n g h i l l s i d e s . The o b j e c t i v e s of t h i s work were: (1) to o b t a i n a large sample of both species f o r sys-tematic a n a l y s i s , (2) t o determine i n d e t a i l the h a b i t a t d i s t r i b u t i o n of the species i n and around the r a v i n e , and (3) t o car r y out a f i e l d experiment on the causes of the ob-served h a b i t a t r e s t r i c t i o n . The r a v i n e i s roughly 500 yards long, 100 yards wide at the mouth, and 200 f e e t i n gr e a t e s t depth. I t f a c e s n o r t h , opening onto a c u l t i v a t e d f i e l d through which a small creek flows ( F i g . 43). The ra v i n e i t s e l f has almost no sur-face water, but i s marshy i n a few spots. I t s r e l a t i v e wet-ness i s a r e s u l t of i t s northern exposure and of drainage from the surrounding h i l l s . . The r a v i n e f l o o r i s wide and f a i r l y f l a t , r i s i n g i r r e g u l a r l y toward i t s head. Near the head i t s p l i t s i n t o s e v e r a l small steep g u l l i e s . The v e g e t a t i o n of the r a v i n e i s denser than that of any other part of the ranch ( F i g . 44), hut i t v a r i e s g r e a t l y from place to p l a c e . The lower parts are wetter and conse-quen t l y have denser v e g e t a t i o n than the upper p a r t s . The g u l l i e s at the head are as dry and as s p a r s e l y vegetated as the surrounding h i l l s . The v e g e t a t i o n has been much d i s t u r -bed by human a c t i v i t y . Logging has thinned the timber and i n one area completely removed i t . The rav i n e i s frequented by c a t t l e during p a r t of the year and they have trampled the F i g u r e 43. Looking south toward the r a v i n e at Wright's Ranch. The r a v i n e i s i n the center of the p i c t u r e . F i g u r e 44. P. oreas h a b i t a t i n the r a v i n e at Wright's Ranch. 142. undergrowth, severely browsed the shrubs, and contributed to the enrichment of the s o i l . Engelmann spruce i s the most ch a r a c t e r i s t i c tree here. Near the mouth i t forms small stands of trees 3 i n . to 10 i n . i n diameter. Farther up i t i s less common, but there are a few much larger trees. There are several clumps of large aspen near the middle of the ravine bottom. Small Douglas f i r are scattered throughout and are dominant near the head of the ravine. Most of the ravine i s not under tree canopy. In the open areas i n the middle and lower parts of the ravine shrubs are dense, the most abundant being o s i e r . A l -der and other also are present. At most places there i s l i t -t l e ground vegetation. Small logs are abundant in, some places, absent from others. There i s some brush scattered on the ground, and a few large brush p i l e s . There are no rocks i n the ravine. A t y p i c a l s o i l p r o f i l e i n the areas of dense vegetation shows two inches of surface l i t t e r underlain by almost a foot of f i n e f r i a b l e humus. The humus i s dark brown, loosely bound by roots and mycelia. Beneath the humus i s f i n e mineral loam. The s o i l i n the less heavily vegetated parts of the ravine and on the h i l l s i d e s consists of weathered loam under a t h i n layer of l i t t e r , with l i t t l e humus content. The h i l l s i d e s east and west of the ravine are irr e g u l a r i n contour, the grade varying from gentle to f a i r l y steep. The eastern slope i s completely forested, the f i r s t 100 feet 1 4 3 . f e e t from the bottom with Douglas f i r and Engelmann spruce 3 i n . t o 10 i n . i n diameter, the middle and upper l e v e l s w i t h only Douglas f i r , 1 i n . to 4 i n . i n diameter. There i s almost no herb or shrub l a y e r , and l i t t l e ground cover of any k i n d . The western slope i s more gradual than the eastern, and with more open v e g e t a t i o n . Here there are bushes i n p l a c e s , a carpet of grass i n o t h e r s , lodgepole pine i n others, and here i s the only i n t r u s i o n of ponderosa pine i n t o the r a v i n e . Spruce i s absent, but s m a l l aspen are common i n p l a c e s . Douglas f i r i s perhaps the most abundant t r e e s p e c i e s . Most of the t r e e s are l e s s than 4 i n . i n diameter, but a few Douglas f i r and ponderosa pine reach more than 24 i n . i n diameter. Behind the r a v i n e i s a l e v e l h i l l t o p , w i t h stands of ponderosa pine, lodgepole p i n e , and Douglas f i r of v a r y i n g s i z e and d e n s i t y . There i s a good deal of open space with grass. At the mouth of the r a v i n e i s an open f i e l d , through which, 25 yards from the mouth, a s m a l l stream flows. For p a r t of i t s way through the f i e l d the stream i s l i n e d on both sides w i t h aspen and some undergrowth. Both above and below the l e v e l of the r a v i n e the stream flows c l o s e against the f o o t of the h i l l s , where the northern exposure and p r o x i -mity of the stream permit denser v e g e t a t i o n and some spruce to occur. Traps set i n and around the r a v i n e took 69 oreas and 45 a r t e m i s i a e . The area where the oreas were trapped c o r r e s -144. ponds c l o s e l y to tha t occupied by the denser v e g e t a t i o n . I t was taken i n the woods near the mouth of the r a v i n e , on the r a v i n e f l o o r throughout i t s lower h a l f , and f o r a short d i s -tance along the creek west of the r a v i n e . The only areas without dense v e g e t a t i o n that y i e l d e d oreas were the upper h a l f of the ravine and the lower part of the western h i l l -s i d e , where a few mice of t h i s species were taken among s c a t -t e r e d pines and grass. No oreas were taken on the eastern h i l l s i d e , on the h i l l behind the r a v i n e , among the aspen i n the open f i e l d , or along the creek east of the r a v i n e . The oreas taken on the western slope may have been r e s i d e n t s of the ravine bottom f o r a g i n g on the h i l l s i d e . The apparent r e s t r i c t i o n of oreas to the r a v i n e bottom may have r e s u l t e d p a r t l y from the t r a p p i n g procedure; F i f t y -two of the 69 oreas were caught i n the f i r s t three n i g h t s of t r a p p i n g , when most of the t r a p s were set i n the more f a v o r -able oreas h a b i t a t . The upper part of the ravine was ade-quately sampled duri n g t h i s time, though, and y i e l d e d only a few mice of t h i s s p e c i e s . Subsequent t r a p p i n g produced some oreas i n the f a v o r a b l e h a b i t a t s but f a i l e d t o produce any i n h a b i t a t s other than those mentioned above. The d i s t r i b u t i o n of artemisiae was almost complementary t o t h a t of oreas. I t was found i n sm a l l numbers completely e n c i r c l i n g the r a v i n e - - i n the brush and t r e e s near the mouth, on the h i l l s i d e s f l a n k i n g the r a v i n e , on the h i l l behind the 1 4 5 . r a v i n e , and among the aspen along the stream i n the f i e l d . I t a l s o was taken i n the upper parts of the r a v i n e , where the v e g e t a t i o n i s sparse and oreas i s r a r e . Ten oreas were taken i n the hushes along the creek west of the r a v i n e . JMo a r t e m i s i a e were taken by the creek, but four were taken i n s m a l l aspen at the f o o t of the h i l l 30 f e e t from the creek. There i s a zone around the ravine i n which both species occur. T h i s zone seems t o be narrow, perhaps only a few yards wide, on the eastern s i d e and along the mouth of the r a v i n e , but somewhat wider on the western side and i n the upper part of the r a v i n e . Oreas i s l e s s common i n t h i s zone of overlap than i n the areas which i t occupies e x c l u s i v e l y . The t r a p p i n g program was so i r r e g u l a r i n both space and time t h a t i t does not seem p e r m i s s i b l e to attempt a nu-m e r i c a l estimate of the r e l a t i v e abundance of the two s p e c i e s . I n the f i r s t three n i g h t s of t r a p p i n g 6 9 t r a p s set i n the best oreas h a b i t a t took 2 7 oreas and two a r t e m i s i a e . L a t e r 90 traps set on the eastern h i l l s i d e and the h i l l behind the r a v i n e i n t y p i c a l a r t e m i s i a e h a b i t a t took one oreas and 11 artemisiae i n three n i g h t s . The highest l o c a l c o n c e n t r a t i o n of a r t e m i s i a e was found i n the bushes and aspen along the creek i n the open f i e l d , where 16 t r a p s took 10 mice of t h i s race i n three n i g h t s . T h i s i n t e n s i v e t r a p p i n g program confirmed .the r e s u l t s of the p r e l i m i n a r y t r a p p i n g , namely t h a t oreas i s confined 1 4 6 . almost e n t i r e l y t o the f l o o r of the r a v i n e , that a r t e m i s i a e occurs only around the edges of the r a v i n e , and that oreas, while of much more r e s t r i c t e d d i s t r i b u t i o n than a r t e m i s i a e , i s found i n much gr e a t e r density where i t does occur. Trapping outside the r a v i n e revealed t h a t t h i s popu-l a t i o n of oreas i s q u i t e i s o l a t e d from a l l o t h e r s . The only oreas trapped outside the r a v i n e were a few taken along the creek to the west. Above here the creek flows through an extensive area of mine wastes and l i t t l e v e g e t a t i o n , t o t a l l y unsuited to oreas. From my tr a p p i n g and observations i n other parts of the reg i o n I b e l i e v e t h a t there i s no other oreas population w i t h i n s e v e r a l m i l e s . The s m a l l and i s o l a t e d nature of t h i s p o p u l a t i o n made i t p o s s i b l e t o attempt t r a p p i n g a l l of the oreas present. I d i d not succeed i n removing the e n t i r e p o p u l a t i o n , but probably d i d remove a high percentage of i t . The l a s t sev-e r a l hundred t r a p n i g h t s i n good oreas h a b i t a t y i e l d e d only f o u r Peromyscus, a l l of them oreas. Two ni g h t s of t r a p p i n g i n the same h a b i t a t seven weeks l a t e r y i e l d e d three oreas and two a r t e m i s i a e . Apparently there was no reproduction during t h i s time, and i f we assume no immigration the m i n i -mum oreas p o p u l a t i o n at the beginning of the t r a p p i n g pro-gram was 72 . The a c t u a l population s i z e probably was not much greater than t h i s . The primary reason f o r t r y i n g to remove a l l of the oreas was an experiment t o he l p e x p l a i n 1 4 7 . the proximate causes of the d i f f e r e n t i a l h a b i t a t d i s t r i b u -t i o n of the two s p e c i e s . T h i s w i l l be discussed l a t e r . The r a v i n e i n which oreas was taken at Wright's Ranch i s one m i l e west of the r i m of the deep v a l l e y of the S i m i l -kameen R i v e r , which here i s at 2200 f e e t e l e v a t i o n . The area between the r a v i n e and the r i v e r i s mostly i n grass or open ponderosa pine stands, but some dense Douglas f i r stands are present. Trapping i n these h a b i t a t s y i e l d e d o n l y a r t e -m i s i a e . I n s p e c t i o n of the v a l l e y at r i v e r l e v e l f a i l e d to r e -v e a l any spruce or areas of dense v e g e t a t i o n . The wettest* s i t e found was one m i l e south of P r i n c e t o n , where Douglas f i r , w i l l o w s , r o s e s , and grasses provided the best cover i n the v a l l e y . P o r t y t r a p s set here f o r two n i g h t s took o n l y t h r e e Peromyscus, a l l a r t e m i s i a e . The easternmost s t a t i o n on t h i s t r a n s e c t was a t the P r i n c e t o n Golf Club ( 4 4 ) , two m i l e s east of P r i n c e t o n . The s t a t i o n l i e s a t 2100 f e e t e l e v a t i o n on the east s i d e of the Similkameen R i v e r , i n the Dry F o r e s t B i o t i c Area. I t i s i n the narrow v a l l e y of the r i v e r , where ponderosa pine and open grassland are the c h a r a c t e r i s t i c h a b i t a t s . On north-f a c i n g slopes Douglas f i r becomes dominant. F o r e s t cover maps i n d i c a t e that i n the r o l l i n g country above the v a l l e y Engelmann spruce and Douglas f i r are climax, but I was unable to l o c a t e such f o r e s t s . U S . The h a b i t a t s at t h i s s t a t i o n are shown i n F i g u r e 4 5 . The most h e a v i l y trapped h a b i t a t type was ponderosa pine woods ( F i g . 4 6 ) . I n 136 t r a p n i g h t s o n l y two Peromyscus were taken i n these woods. In mixed ponderosa pine-Douglas f i r woods, however, two Peromyscus were taken i n only 18 t r a p -n i g h t s . I n 130 t r a p n i g h t s among the t r e e s , shrubs, and brush p i l e s along a r i v e r bank 10 Peromyscus were taken. The lower edge of a t a l u s slope y i e l d e d s i x mice i n 30 t r a p -n i g h t s . An open f i e l d w i t h dry but r e l a t i v e l y l u x u r i a n t ( f o r t h i s area) grass and many s m a l l , p a r t l y b u r i e d , boulders y i e l d e d 12 mice i n 84 t r a p n i g h t s . A l l Peromyscus taken at t h i s s t a t i o n were a r t e m i s i a e . Ponderosa pine woods are the h a b i t a t l e a s t favorable f o r Peromyscus at t h i s s t a t i o n . R e s u l t s here correspond w e l l w i t h those a t Wright's Ranch, where such woods a l s o y i e l d e d few of these mice. A l l other h a b i t a t s here y i e l d e d much higher catches per u n i t e f f o r t . Cover i n ponderosa pine woods c o n s i s t s of sparse ground v e g e t a t i o n and s c a t -t e r e d l o g s . The higher catches i n most other h a b i t a t s can be a t t r i b u t e d to b e t t e r cover, but t h i s does not seem to apply to the open grass f i e l d . The grass and herbs here reached about a f o o t i n height, but hardly provided more cover than the ground v e g e t a t i o n i n ponderosa pine woods. The boulders, averaging about a f o o t i n diameter, were h a l f b u r i e d and provided no r e a l cover. The f i e l d was surrounded by ponderosa pine woods. F i g u r e 45. Looking north toward. P r i n c e t o n G o l f Club. The c l u b i s i n foreground; Similkameen R i v e r i s i n middle d i s t a n c e . F i g u r e 4 6 . Ponderosa pine f o r e s t at P r i n c e t o n Golf Club. 150. The Gibson Pass area (37), s e v e r a l m i l e s south of A l l i s o n Pass, was almost devoid of Peromyscus. Only t h r e e , a l l oreas, were caught i n 260 t r a p n i g h t s . Traps were set over an area of s e v e r a l m i l e s , near the Cascade summit. Most t r a p p i n g was done at Gibson Pass (4500 f e e t ) i t s e l f , i n open lodgepole pine woods, i n c l e a r i n g s of grass and shrubs, along the marshy bank of a s m a l l stream, and i n Engelmann-spruce-alpine f i r woods. One of the three mice was taken on a r a t h e r dry h i l l s i d e w ith some ground cover and s c a t t e r e d l a r g e t r e e s . One was taken i n dense spruce-f i r woods i n the pass. The t h i r d was taken two m i l e s n o r t h -east of the pass (5000 f e e t ) , i n a s m a l l a l p i n e f i r stand surrounded by a l p i n e meadow. Treasure Mountain (47) i s at the same l a t i t u d e as Hope and P r i n c e t o n , l y i n g somewhat c l o s e r to Hope. Trap-p i n g was done on the lower part of the south slope of the mountain, at 4700 f e e t . Apparently the e n t i r e mountain was f o r e s t e d at one. time, but as a r e s u l t of f i r e t r e e s are now r e s t r i c t e d to a zone near the bottom. Engelmann spruce and subalpine f i r are the common t r e e s p e c i e s . The upper parts of the mountains are vegetated by blueberry, l u p i n e , and other shrubs and herbs c h a r a c t e r i s t i c of the h i g h Cascades. Most of the t r a p p i n g was done near the present t i m b e r l i n e . Oreas was common i n the woods and on the d r i e r brushy h i l l -s i d e s , but was not taken i n wet meadows. Se v e r a l specimens from here may be a r t e m i s i a e . 151. 3. oreas and austerus Osgood (1909) s t a t e d t h a t these forms l i v e under appa-r e n t l y i d e n t i c a l c o n d i t i o n s , and S v i h l a (1933) took both forms i n the same h a b i t a t s on the Olympic P e n i n s u l a . D a l -quest (1948, p.92) on the other hand says t h a t " w i t h i n the range of austerus and w i t h i n the range of oreas only one subspecies i s found whether the h a b i t a t be coniferous f o r e s t or t h i c k e t s of a l d e r and w i l l o w , but where the ranges of the two subspecies meet austerus occurs only i n the t h i c k e t s of aspen and w i l l o w and oreas occurs only i n the con i f e r o u s f o r e s t s . " I have l i t t l e s a t i s f a c t o r y i n f o r m a t i o n on the h a b i t a t r e l a t i o n s of these forms i n the zone of sympatry. I n Wash-ing t o n t h i s zone i s wide, extending from the western Cascades t o the P a c i f i c Ocean, though at some places w i t h i n t h i s zone only one form occurs. The zone of overlap i s narrower i n B r i t i s h Columbia, apparently occupying only the lower slopes of the mountains. The d i f f i c u l t y of i d e n t i f y i n g many i n d i -v i d u a l s and the p o s s i b i l i t y of h y b r i d i z a t i o n make i t d i f f i -c u l t t o study the h a b i t a t d i s t r i b u t i o n of these races i n the zone of overlap. Both oreas and austerus were taken at Ilwaco (63) > at the mouth of the Columbia R i v e r . According t o i n f o r m a t i o n on the l a b e l s , two austerus, one oreas, and one indetermin-able specimen were trapped i n a wet creek bed, one austerus i n damp woods, and two oreas i n a swamp. At Tokeland (68) 152. on W i l l a p a Bay three oreas were trapped i n damp woods near the beach and two were trapped i n dry pines. Two austerus were trapped i n a grassy swamp. At She l t o n (84), near Puget Sound, both races were trapped i n a wet creek bottom; one oreas and one indeterminable specimen were trapped on a dry h i l l s i d e . Both races were taken i n dry woods at Ch e h a l i s (94). A larg e sample of Peromyscus was taken at La Wis Wis Camp (95) on the C o w l i t z R i v e r i n the Coast F o r e s t B i o t i c Area. Trapping was done along both banks of the r i v e r and as f a r as 100 f e e t from the r i v e r . The f o r e s t c o n s i s t e d of l a r g e Douglas f i r , western hemlock, and red cedar. Ground v e g e t a t i o n and logs were abundant i n many p l a c e s . The C o w l i t z R i v e r would be expected t o provide s u i t a b l e h a b i -t a t f o r austerus from the lowlands to La Wis Wis, the a l t i -tude here was only 1000 f e e t , and austerus has been taken i n s i m i l a r h a b i t a t s elsewhere, but only oreas was taken here. T h i r t y - e i g h t mice of t h i s species were taken by 88 t r a p s i n one n i g h t . The Twin Creeks s t a t i o n (111) was on the bank of the White R i v e r at 1500 f e e t e l e v a t i o n , i n the Coast F o r e s t B i o -t i c Area. The land here was f l a t , but there were f o o t h i l l s l e s s than \ m i l e away. The e n t i r e area had been logged and was covered by s e r a i v e g e t a t i o n . The t r a p s were set near the r i v e r i n dense growth of a l d e r and shrubs. Some western 153. hemlock, Douglas f i r , and red cedar s a p l i n g s were present, and a few hemlock and a l d e r up to one f o o t i n diameter. F i f t y - f i v e t r a p s took 22 oreas i n one n i g h t . At Denny Creek (112)(2400 f e e t ) the t r a p s were set on the f l o o d p l a i n of a large creek and near the bottom of the adjacent h i l l s i d e . T h i s s t a t i o n was also i n the Coast F o r e s t B i o t i c Area. A l d e r was the most abundant t r e e near the creek, while mature red cedar and western hemlock were dominant elsewhere. Undergrowth was t h i c k i n many pl a c e s . E i g h t y - s i x t r a p s took 34 oreas i n one n i g h t . A l l h a b i t a t s y i e l d e d some, but the dense undergrowth near the creek was most h e a v i l y populated. The la r g e c o l l e c t i o n of austerus from Cultus Lake (129) and Robertson's (130), on the edge of the Puget Sound Low-lands B i o t i c Area, was made by open water i n predominatly red cedar-western hemlock f o r e s t . A l d e r was abundant and undergrowth was dense i n p l a c e s . The c o l l e c t i o n from 1100 f e e t on the C h i l l i w a c k R i v e r 16 mil e s east of Vedder Cross-i n g (131) i n the Coast F o r e s t B i o t i c Area c o n s i s t e d of both austerus and oreas. Three austerus and the s i n g l e oreas were taken i n an undisturbed red cedar-western hemlock f o r -est near the r i v e r . Three austerus were taken i n the dense v e g e t a t i o n of an o l d burn on a dry t e r r a c e above the r i v e r . The systematic st a t u s of the animals i n the Hope (135) sample i s too confused to permit a n a l y s i s of h a b i t a t p r e f e r -ences at t h a t s t a t i o n . The C o q u i h a l l a R i v e r s t a t i o n (136) 154. was on a mountainside (1000 f e e t ) high above the r i v e r i n the Coast F o r e s t B i o t i c Area. Two austerus were taken along a road i n coast f o r e s t . One austerus, one oreas, and two probable oreas were taken i n the dense s e r a i growth of an area that had been logged s e v e r a l years e a r l i e r . The h a b i t a t d i s t r i b u t i o n of oreas and austerus at the Upper Skagit R i v e r s t a t i o n (137) i s given i n Table X I I . T h i s s t a t i o n was i n the Coast F o r e s t B i o t i c Area, shown i n F i g u r e 47. Here oreas was taken on a l l l i n e s (2000-2500 Table X I I . H a b i t a t d i s t r i b u t i o n of Peromyscus on the Upper Skagit R i v e r .  Trap- Catch Lin e n i g h t s o a ? t o t H a b i t a t I 80 8 8 Mature western hemlock-red cedar-Douglas f i r stand on t e r r a c e above creek, w / l i t t l e ground cover. I I 80 6 6 Old western hemlock-red cedar-Douglas f i r w/vine maple, some l o g s , l i t t l e ground v e g e t a t i o n . I l l 80 2 1 3 Mature western hemlook-red cedar-Douglas f i r stand on steep s l o p e , w/some logs & ground v e g e t a t i o n . IV 80 2 2 4 Large red cedar & western hemlock by r i v e r , w/many l o g s , l i t t l e ground v e g e t a t i o n , much bare ground, V 80 3 1 4 Dry t e r r a c e w/Douglas f i r , rhodo-dendron, Pachystima, l i t t l e ground cover. VI 80 1 3 4 S i m i l a r to Line V. VII 40 4 1 5 Mature western hemlock & red cedar by creek, w/many logs & brush but l i t t l e ground v e g e t a t i o n . V I I I 40 4 4 Dense o s i e r t h i c k e t by r i v e r . IX 40 1 4 1 6 Talus s l o p e . oOO 31 10 3 44 155. F i g u r e 47. Coast f o r e s t on upper Skagit R i v e r . f e e t ) , while mice d e f i n i t e l y i d e n t i f i e d as austerus were taken on only four l i n e s (2100-2200 f e e t ) . I t i s d i f f i -c u l t to determine any p a t t e r n of h a b i t a t preference from these l i m i t e d data. Both forms were taken i n both wet and dry h a b i t a t s , with the amount of cover probably the main f a c t o r determining o v e r a l l abundance. The highest austerus/  oreas r a t i o s were obtained on the d r i e s t l i n e s (VI and I X ) . Near Ross Lake (138) two oreas and two austerus were trapped i n second-growth coast f o r e s t . The s i t e was near a creek, and had a moderate amount of ground v e g e t a t i o n . The Mount Seymour (145) sample was c o l l e c t e d on the south side of the mountain. The r e s u l t s of snap-trapping 156. are given i n Table XI1T. I n a d d i t i o n , l i v e - t r a p p i n g at 2900 f e e t , near L i n e 61, y i e l d e d a number of oreas and one austerus. E x t e n s i v e l i v e - t r a p p i n g at 3300 f e e t y i e l d e d only oreas (some of them q u e s t i o n a b l e ) . The f o r e s t here was an o l d stand of mountain hemlock, y e l l o w cedar, and subalpine f i r . Peromyscus was l e s s abundant here than at lower e l e -v a t i o n s . The e n t i r e mountainside below 2700 f e e t was burned many years ago, but above t h i s l e v e l there i s e s s e n t i a l l y undisturbed subalpine f o r e s t . The coast f o r e s t of western hemlock, red cedar, and Douglas f i r i s replaced by subalpine f o r e s t of mountain hemlock, y e l l o w cedar, and subalpine f i r Table X I I I . Habitat d i s t r i b u t i o n of Peromyscus on Mt.Seymour Traps Catch E l e v . Line (Nights) o a ? t o t ( f e e t ) H a b i t a t  59 31(2) 14 1 15 1500 Mature red cedar & western hemlock, some Douglas f i r , a l d e r & bushes, many logs & rock s , on gentle slope. 60 18(1) 4 4 2200 Small red cedar, western hem-l o c k , Douglas f i r , a l d e r ; much underbrush, some l o g s , on steep dry slope. 64 26(1) 2 1 2 5 2500 Small red cedar & western hemlock, much underbrush, some logs & rocks. 62 33(2). 2 4 6 2700 Small western hemlock, some red cedar, on gentle s l o p e , much "Vaccinium, few herbs, many logs & stumps. 63 32(2) 8 2 5 15 2700 Mature western hemlock-red cedar-subalpine f i r above stream; many l o g s , l i t t l e ground v e g e t a t i o n . 61 33(2) 8 8 2900 As 63, but few l o g s . T73 20 21 12 53 . 157. at 2700-3200 f e e t . Of the subalpine species, subalpine f i r extends t o the lowest e l e v a t i o n s . The d i s t r i b u t i o n of the races of Peromyscus i s l o o s e l y c o r r e l a t e d with t h a t of both climax f o r e s t .type and extent of o l d burn. I have not found the s t r i c t h a b i t a t segregation of oreas and austerus that Dalquest d e s c r i b e s . On the c o n t r a r y , they have been trapped s i d e by side on many l i n e s . Undoubt-e d l y , though, there i s some tendency toward preference f o r d i f f e r e n t h a b i t a t s . T h i s i s suggested by the c o l l e c t i o n data above and by the absence of one of the races from p a r t s of the r e g i o n where they are sympatric. I t would be d i f f i -c u l t t o e x p l a i n the apparent absence of austerus from the west side of the Olympic P e n i n s u l a otherwise, but i t a l s o i s d i f f i c u l t to imagine what the e c o l o g i c a l f a c t o r s can be th a t exclude i t from that r e g i o n . Much of the r e g i o n has been cut or burned i n the past and now i s t h i c k i n scrub growth, seemingly b e t t e r s u i t e d t o austerus than to oreas. The a l t i t u d i n a l r e l a t i o n s of oreas w i t h austerus are as v a r i e d as wit h the races on the eastern side of the Cas-cades. On the P a c i f i c Coast of Washington and on the B r i t -i s h Columbia coast n o r t h of Howe Sound oreas l i v e s a t sea l e v e l , alone i n some places and with austerus i n othe r s . On Mount Seymour, though, i t apparently does not occur much below 2500 f e e t . On Mount Seymour austerus occurs to at l e a s t 2900 f e e t , i n the Skagit V a l l e y to at l e a s t 2200 f e e t , and yet i t was not found at 1500 f e e t at Twin Creeks or at 158. 1000 f e e t at La Wis Wis. I t s occurrence on Mount Seymour seemed t o be c o r r e l a t e d with, the d i s t r i b u t i o n of d i s t u r b e d coast f o r e s t , yet the f o r e s t at Twin Creeks was even more d i s t u r b e d . I t does not seem a d v i s a b l e t o attemp an a n a l y s i s of the f a c t o r s c o n t r o l l i n g the geographic and h a b i t a t d i s -t r i b u t i o n of these forms u n t i l a thorough f i e l d study has been made. I I I . MAMMALIAN ASSOCIATES Most of the species of small mammals known t o occur i n the Northwest were trapped during the present study, but i n such small numbers that the r e s u l t s are of l i t t l e value f o r the study of h a b i t a t d i s t r i b u t i o n . The most f r e q u e n t l y trapped s p e c i e s , other than Peromyscus, was Clethrionomys  gapperi ( V i g o r s ) . I t was u s u a l l y trapped i n h a b i t a t s where Peromyscus oreas a l s o occurred, but seldom was found asso-c i a t e d w i t h P. maniculatus. There i s no reason to b e l i e v e t h a t there i s a d i r e c t r e l a t i o n between Clethrionomys and oreas; r a t h e r , they seem to have s i m i l a r h a b i t a t r e q u i r e -ments. Oreas o f t e n , i n f a c t u s u a l l y , was taken without Clethrionomys, but Clethrionomys was seldom taken without oreas. Clethrionomys seems to be confined to e l e v a t i o n s above 2000 f e e t i n the areas t h a t I trapped. On the Upper S k a g i t R i v e r s t a t i o n Clethrionomys and oreas were taken together on two l i n e s , without austerus. w h i l e a l l three forms were taken on one l i n e . No C l e t h r i -159. onomys were taken on s i x l i n e s . At A l l i s o n Pass oreas was taken on a l l nine l i n e s , Clethrionomys on s i x , and maniculatus on none. At Goodfellow Creek both oreas and ar t e m i s i a e were taken on f i v e l i n e s , while oreas and C l e t h -rionomys were taken on three other l i n e s . No Clethrionomys were trapped at Copper Creek, but one was trapped at Sunday Summit on a l i n e where no Peromyscus were taken. At Wright's Ranch Clethrionomys was common i n the ravine i n h a b i t e d by oreas, but was not taken elsewhere. At C l e a r Lake only one Clethrionomys was trapped, on a l i n e on which oreas was trapped, but not gambeli. At American Forks Clethrionomys was trapped on two l i n e s , on both of which oreas and gambeli were trapped. These l i n e s were those where oreas was most abundant and gambeli was l e a s t abundant. On Mount Seymour Clethrionomys was almost confined t o the subalpine f o r e s t where oreas was found, h a r d l y o v e r l a p p i n g the d i s t r i b u t i o n of austerus. Data on other mammals are too few to permit a n a l y s i s . Sorex was o f t e n abundant, but s p e c i f i c i d e n t i f i c a t i o n was u n c e r t a i n . A few Zapus were trapped, u s u a l l y i n h a b i t a t s occupied by oreas. Eutamias townsendi (Bachman), a c o a s t a l form, was found i n oreas h a b i t a t at places i n the zone of sympatry of oreas with a r t e m i s i a e and gambeli, while E. amoe-nus a f f i n i s ( J . A . A l l e n ) of the i n t e r i o r was a s s o c i a t e d w i t h a r t e m i s i a e and gambeli. At A l l i s o n Pass, where no race of maniculatus occurred, oreas was taken i n a burn which had a l a r g e amoenus p o p u l a t i o n . 160. IV. DISCUSSION OF ECOLOGICAL RELATIONS Many s t u d i e s have been made of the h a b i t a t d i s t r i b u -t i o n of v e r t e b r a t e s , u s u a l l y c o n s i s t i n g l a r g e l y i n c o r r e l a -t i o n of species occurrence with t h a t of the dominant vege-t a t i o n or some other conspicuous environmental f e a t u r e . Such s t u d i e s , w h i l e v a l u a b l e , have the shortcoming common to a l l c o r r e l a t i o n s t u d i e s of not showing causal r e l a t i o n -s h i p s . We know l i t t l e of the nature of the things t h a t ac-t u a l l y determine the h a b i t a t d i s t r i b u t i o n of animals. I t has not been p o s s i b l e i n the present study to d i s -cover the mechanisms, proximate or u l t i m a t e , r e s p o n s i b l e f o r the observed h a b i t a t d i s t r i b u t i o n of Peromyscus. The places where mice were found have been described i n g e n e r a l terms, but i t i s d i f f i c u l t to go f u r t h e r and sort out the f a c t o r or combination of f a c t o r s that i s of most importance. However, although my data are not s u i t a b l e f o r s t a t i s t i c a l a n a l y s i s and the data f o r i n d i v i d u a l t r a p l i n e s are too few to be very r e l i a b l e , c e r t a i n trends stand out. At the most s u p e r f i c i a l l e v e l of a n a l y s i s , we f i n d t h a t the Dry Forest B i o t i c Area i s i n h a b i t e d almost e x c l u -s i v e l y by arte m i s i a e and gambeli, w h i l e the adjacent Subal-pine F o r e s t B i o t i c Area i s i n h a b i t e d by oreas. The Coast F o r e s t B i o t i c Area may be i n h a b i t e d e x c l u s i v e l y by oreas (Washington s t a t i o n s ) , by both oreas and austerus (Upper Skagit R i v e r ) , or by austerus only (Mount Seymour). The Pu-get Sound Lowlands B i o t i c Area i s p r i m a r i l y the home of aus-161. t e r u s , though oreas a l s o occurs there i n many pl a c e s . These b i o t i c areas are very rough g e n e r a l i z a t i o n s of complex geo-g r a p h i c - e c o l o g i c a l phenomena, and the a s s o c i a t i o n of races of Peromyscus w i t h them i s correspondingly rough. There are many e c o l o g i c a l v a r i a b l e s a s s o c i a t e d w i t h these d i f f e r e n c e s i n b i o t i c communities. Temperature, r a i n -f a l l , snow cover, and other c l i m a t i c f a c t o r s a f f e c t animals d i r e c t l y and through the v e g e t a t i o n . Topography, s o i l , and other animal species may be important. Most important of a l l , perhaps, i s the nature of the v e g e t a t i o n , i n c l u d i n g both i t s p h y s i c a l s t r u c t u r e and i t s species composition. Two environmental f a c t o r s u s u a l l y were a s s o c i a t e d with hi g h d e n s i t i e s of Peromyscus—good ground cover and the pre-sence of water. Ground cover was i n the form of t h i c k bushes or herbs, l o g s , or t a l u s s l o p e s . Water was u s u a l l y i n the form of streams. Good cover and p l e n t i f u l water are u s u a l l y a s s o c i a t e d i n nature, but Peromyscus has been found abundant i n h a b i t a t s w i t h only one of them. The importance of cover to animals subject to heavy p r e d a t i o n i s obvious, but the s i g n i f i c a n c e of water i s not c l e a r . The Peromyscus trapped i n streamside l o c a t i o n s w i t h l i t t l e ground cover pro-bably nested i n b e t t e r cover nearby. The c o m p l e x i t i e s of h a b i t a t are so great t h a t i t does not seem j u s t i f i a b l e to base f u r t h e r g e n e r a l i z a t i o n s on the a v a i l a b l e data. We w i l l now consider the p o s s i b l e reasons 162. f o r the f a c t s o u t l i n e d above. The f a c t o r s c o n t r o l l i n g the d i s t r i b u t i o n and abundance of animals are i n t i m a t e l y con-nected w i t h the problems of t h e i r e v o l u t i o n a r y h i s t o r y and the nature of a d a p t a t i o n . The t h i n g s which l i m i t the geo-graphic d i s t r i b u t i o n of an animal may a l s o be the t h i n g s which l i m i t i t s e c o l o g i c a l d i s t r i b u t i o n i n a given area, or they may be q u i t e d i f f e r e n t . Abundance may or may not be determined by the f a c t o r s t h a t c o n t r o l d i s t r i b u t i o n . Among the t h i n g s t h a t determine d i s t r i b u t i o n and abun-dance a r e — ( 1 ) the a b i l i t y of the species t o s u r v i v e i n the area or h a b i t a t (adaptiveness), (2) the innate response of the species to the h a b i t a t ( h a b i t a t s e l e c t i o n ) , and (3) the presence of competing s p e c i e s . (1) Two p r i n c i p a l adaptive types are found i n Peromys-cus maniculatus ( B l a i r 1 9 5 3 ) — l i g h t - c o l o r e d forms of the c o n t i n e n t a l i n t e r i o r , with short t a i l s and short hind f e e t , and darker forms of the mountains and coasts, with long t a i l s and long hind f e e t . T h i s d i s t r i b u t i o n corresponds t o that of the p r a i r i e s and f o r e s t s , s h o r t - t a i l mice l i v i n g on the open p r a i r i e s and l o n g - t a i l mice l i v i n g i n f o r e s t e d r e g i o n s . The characters of these two groups are a s s o c i a t e d w i t h the two aspects of s u r v i v a l i n a given h a b i t a t — f i n d i n g the necessary requirements of food and s h e l t e r , and a v o i d i n g being k i l l e d by predators. F o r e s t - d w e l l i n g Peromyscus are 163. known t o "be p a r t l y a r b o r e a l i n h a b i t , and Horner ( 1 9 5 4 ) has shown e x p e r i m e n t a l l y t h a t the long t a i l c h a r a c t e r i s t i c of such races i s of value i n c l i m b i n g . T h i s appears t o be tr u e of long h i n d f o o t a l s o . Among the races included i n the present study a r t e m i s i a e and gambeli have the sh o r t e s t t a i l s , and they occur i n the most open h a b i t a t s . They a l s o have hind f e e t s h o r t e r than those of oreas. Austerus, how-ever, which l i v e s i n dense v e g e t a t i o n , has f e e t as short as those of ar t e m i s i a e and gambeli, and t a i l s i n t ermediate be-tween these races and oreas. Dalquest ( 1 9 4 8 ) b e l i e v e s that oreas i s f r e q u e n t l y a r b o r e a l but that austerus i s not. Numerous s t u d i e s have shown t h a t c o l o r a t i o n i n Pero-myscus i s c r y p t i c and i s adapted to match the c o l o r of the background, apparently as a defense against p r e d a t i o n . Dark-colored Peromyscus are found on dark backgrounds, whe-ther i n humid f o r e s t s or on desert l a v a beds, w h i l e l i g h t -c o l o r e d mice are found on l i g h t backgrounds, whether p r a i -r i e s or ocean beaches. The c o l o r a t i o n of the races i n the present study corresponds i n general w i t h the c o l o r a t i o n of the background—artemisiae and gambeli, the l i g h t e s t , are found i n open, l i g h t - c o l o r e d areas, while austerus, the darkest, i s confined to the dark f o r e s t s of the coast. ( 2 ) Horner ( 1 9 5 4 ) r e p o r t s that races of Peromyscus. from f o r e s t e d regions showed a greater tendency to climb than did those from open country. H a r r i s ( 1 9 5 1 ) has found 164.. e x p e r i m e n t a l l y t h a t one of the f o r e s t - d w e l l i n g races of mani-c u l a t u s p r e f e r r e d a simulated f o r e s t environment to simulated g r a s s l a n d , while a p r a i r i e - d w e l l i n g race p r e f e r r e d the simu-l a t e d g r a s s l a n d . These and other s t u d i e s suggest t h a t Pero-myscus has innate r e a c t i o n s to c e r t a i n f e a t u r e s of i t s e n v i -ronment, r e a c t i n g p o s i t i v e l y to some f e a t u r e s and a v o i d i n g o t h e r s ; i n other words, i t a c t i v e l y chooses i t s h a b i t a t . T h i s choice i s made p r i m a r i l y at the time of sexuall m a t u r i t y , when the young mouse leaves i t s p a r e n t a l home and wanders o f f i n search of a new one. Even adu l t mice f r e q u e n t l y s h i f t t h e i r home ranges. N a t u r a l s e l e c t i o n may have f i x e d a pre-ference f o r the most advantageous h a b i t a t as a r a c i a l char-a c t e r . (3) The concept of competition has been questioned r e -c e n t l y by Andrewartha and B i r c h (1954) and)others, but I can see no o b j e c t i o n t o the use of the term provided i t i s care-f u l l y d efined, and then demonstrated r a t h e r than assumed. I n t e r s p e c i f i c competition, w i t h which we are concerned here, may be defined as i n t e r a c t i o n among populations of d i f f e r e n t species i n v o l v i n g the use of a common resource and r e s u l t i n g i n some adverse e f f e c t on one or both p o p u l a t i o n s . I t s e f -f e c t may be d i r e c t or i n d i r e c t , and i t may a f f e c t the popu-l a t i o n s i n terms of n a t u r a l s e l e c t i o n , p o p u l a t i o n s i z e , or geographic or e c o l o g i c a l d i s t r i b u t i o n . I t s e f f e c t on ec o l o -g i c a l d i s t r i b u t i o n w i l l be considered here. 165. I f we can show th a t one species i s able and w i l l i n g t o l i v e i n a c e r t a i n h a b i t a t type but does not do so because of the presence of another s p e c i e s , then we are j u s t i f i e d i n concluding t h a t competition i s l i m i t i n g the d i s t r i b u t i o n of the absent s p e c i e s . The genus Peromyscus occupies most of the t e r r e s t r i a l h a b i t a t s w i t h i n i t s geographic range. Where o n l y one species occurs i t occupies a wide range of h a b i t a t s ; where two or more species occur together one or more of them may be s h a r p l y l i m i t e d i n h a b i t a t d i s t r i b u t i o n (e.g. Dice 1942, McCabe and Blanchard 1950). I t may be t h a t the h a b i -t a t s i n the area of sympatry are not i d e n t i c a l to those i n the a l l o p a t r i c areas and t h a t a species i s absent from them because i t cannot or w i l l not l i v e i n them. On the other hand, i t may be absent because another species i s l i v i n g i n them. The d i s t r i b u t i o n a l data presented above f o r oreas and the i n t e r i o r races of maniculatus ( a r t e m i s i a e and gambeli) show th a t both species occupy almost a l l h a b i t a t s where they occur alone but are more r e s t r i c t e d where they are sympatric. At A l l i s o n Pass oreas was the o n l y race found and here i t was taken i n a l l h a b i t a t s , i n c l u d i n g a l a r g e area of burned-over f o r e s t and lodgepole pine woods, both w i t h l i t t l e cover, as w e l l as the denser, wetter f o r e s t s . At P r i n c e t o n G-olf Club o n l y a r t e m i s i a e was found, and i t too was taken i n a l l h a b i -t a t s , i n c l u d i n g the r e l a t i v e l y dense v e g e t a t i o n of a r i v e r bank. At Wright's Ranch, where both races were found, they 166. occupied complementary h a b i t a t s . Oreas was taken o n l y i n the densest v e g e t a t i o n and ar t e m i s i a e was taken o n l y i n other h a b i t a t s . Both races a l s o were found at Goodfellow Creek and Copper Creek, but a t these s t a t i o n s the e c o l o g i -c a l segregation was l e s s marked. A s i m i l a r r e l a t i o n s h i p e x i s t e d between oreas and gambeli on the T i e t o n R i v e r , though the data are l e s s complete here. I n the zone of sympatry oreas u s u a l l y occurs i n greater l o c a l d e n s i t y than do art e m i s i a e and gambeli. T h i s was not-a b l y t r u e at Goodfellow Creek, Wright's Ranch, and C l e a r Lake. I t probably i s because the h a b i t a t s occupied by oreas are those most fa v o r a b l e f o r Peromyscus. Going from west t o east the p r o p o r t i o n of the area occupied by oreas becomes more r e s t r i c t e d , w h i l e t h a t occupied by a r t e m i s i a e and gam-b e l i i n c r e a s e s . Nevertheless oreas continues t o occupy the best h a b i t a t s , and even at the extreme eastern l i m i t of i t s range i t may occur i n greater l o c a l c o n c e n t r a t i o n than a r t e -m i s i a e and gambeli. Several m i l e s to the east, where no o r -eas occur, a r t e m i s i a e and gambeli are found i n a l l h a b i t a t s , and i n greater average d e n s i t y . A notable exception to t h i s was the low p o p u l a t i o n of gambeli at Cottonwood Camp, but t r a p p i n g here was so b r i e f that the .results mean l i t t l e . These data show t h a t i n the zone of sympatry both o r -eas and the i n t e r i o r races of maniculatus occupy a narrower h a b i t a t range than they do outside t h i s zone. They suggest, but do not prove, t h a t t h i s h a b i t a t r e s t r i c t i o n r e s u l t s i n 167. part from the presence of the other s p e c i e s . U n f o r t u n a t e l y , the h a b i t a t s i n the zone of sympatry are not i d e n t i c a l t o those on e i t h e r side of t h i s zone, but the d i f f e r e n c e s be-tween, say, the densest f o r e s t s of the zone of sympatry and the densest f o r e s t s of the r e g i o n where ar t e m i s i a e occurs along seem l e s s important ( t o the human observer) than the d i f f e r e n c e s between f o r e s t and grassland i n the a r t e m i s i a e r e g i o n . Outside the area of the present study, t he f o r e s t s of the Columbia R i v e r v a l l e y i n s o u t h - c e n t r a l B r i t i s h Columbia are s i m i l a r to those of the coast, i n c l u d i n g the presence of abundant Douglas f i r , red cedar, and western hemlock. Ar t e m i s i a e i s the only race of Peromyscus i n the r e g i o n , and i t occurs i n these f o r e s t s . I n the Cascades, where oreas a l s o i s present, a r t e m i s i a e and gambeli are not found i n such f o r e s t s . However, artemisiae does not extend f a r i n t o the subalpine f o r e s t s of the mountains of the Columbia R i v e r r e g i o n , and these f o r e s t s are l a r g e l y devoid of Pero-myscus (Cowan and Guiguet 1956). I n other words, i n t h i s r e g i o n a r t e m i s i a e occurs i n some h a b i t a t s s i m i l a r t o h a b i -t a t s which i t does not occupy i n the Cascades, but I t i s absent from some h a b i t a t s even i n the absence of other species of Peromyscus. C a r e f u l o b s e r v a t i o n of the c o n d i t i o n s under which a n i -mals occur i n nature can provide valuable evidence f o r or agains t the hypothesis t h a t the d i s t r i b u t i o n of one species 168. i s i n f l u e n c e d by the presence of another. Laboratory experi-. ments can show t h a t competition may be important .under • the c o n d i t i o n s provided, and can c l a r i f y the mechanisms of com-p e t i t i o n . A t h i r d approach i s f i e l d experimentation, the m a n i p u l a t i o n of e n t i r e n a t u r a l p o p u l a t i o n s . Such studi e s would be of great v a l u e , but are d i f f i c u l t to c a r r y out. They would c o n s i s t i n removing a p o p u l a t i o n of one species i n the zone of sympatry or i n i n t r o d u c i n g an e x o t i c species i n t o a region where o n l y one species occurs n a t u r a l l y . The s t r i c t e c o l o g i c a l segregation of oreas and a r t e -misiae at Wright's Ranch and the s m a l l , i s o l a t e d nature of the oreas p o p u l a t i o n there presented an unusual o p p o r t u n i t y to c a r r y out an experiment of the f i r s t type. I attempted to remove the e n t i r e p o p u l a t i o n of oreas from the r a v i n e where i t occurred and observe whether the surrounding popu-l a t i o n of a r t e m i s i a e would then c o l o n i z e the r a v i n e . The success of the experiment depended on the i s o l a t i o n of t h i s p o p u l a t i o n of oreas from a l l others and on removing a l l the oreas present. Trapping outside the r a v i n e showed t h a t t h i s p o p u lation i s probably i s o l a t e d . The p o p u l a t i o n was reduced to a s m a l l f r a c t i o n of i t s o r i g i n a l s i z e , but i t was not p o s s i b l e t o remove a l l of the mice. The surrounding population of a r t e m i s i a e was at a low i n i t i a l d e n s i t y , and by the end of my t r a p p i n g i t too had been g r e a t l y reduced. Furthermore, no r e p r o d u c t i o n was t a k i n g place at t h i s time (August). The o n l y source of Peromyscus 169. t o repopulate the r a v i n e immediately was the low pop u l a t i o n of a r t e m i s i a e i n surrounding untrapped areas or the reduced p o p u l a t i o n i n the trapped areas. When the area was trapped seven weeks l a t e r (October), 76 t r a p s set i n good oreas h a b i t a t i n the ravine f o r two ni g h t s took three oreas and two a r t e m i s i a e . F i v e a r t e m i s i a e were taken by 94 t r a p s set around the perip h e r y . Apparently the ravine had not been repopulated by e i t h e r species during the i n t e r v a l between t r a p p i n g p e r i o d s . F u r t h e r t r a p p i n g w i l l be done at t h i s s t a t i o n . I f i t y i e l d s the same r e s u l t s as the o r i g i n a l t r a p p i n g — o r e a s i n the ravine and a r t e m i s i a e e l s e w h e r e — i t w i l l mean e i t h e r t h a t a lar g e enough breeding stock of oreas was l e f t t o r e -populate the r a v i n e or tha t the r a v i n e has been r e c o l o n i z e d by i n d i v i d u a l s from another population of t h i s s p e c i e s . I f ar t e m i s i a e i s found i n the center of the r a v i n e , and espe-c i a l l y i f i t i s i n greater d e n s i t y there than outside the r a v i n e , i t w i l l i n d i c a t e t h a t o n l y the presence of oreas was keeping i t out o r i g i n a l l y . I f the r a v i n e i s not popu-l a t e d by Peromyscus at a l l , w h i l e a r t e m i s i a e i s found around the periphery, i t w i l l i n d i c a t e t h a t a r t e m i s i a e was absent from the rav i n e because i t was unable or u n w i l l i n g to l i v e t h e r e , not because oreas was t h e r e . Presumably the r a v i n e w i l l e v e n t u a l l y be repopulated by oreas, but there may be a time before the oreas p o p u l a t i o n has b u i l t up to l a r g e s i z e when art e m i s i a e w i l l be found there too. 170. The above d i s c u s s i o n presents some evidence t h a t the presence of the other species r e s t r i c t s the h a b i t a t d i s t r i -b u t i o n of both oreas and maniculatus. I f t h i s i s t r u e i t may r e s u l t from e i t h e r d i r e c t or i n d i r e c t i n t e r a c t i o n of the two s p e c i e s . The i n t e r a c t i o n i s i n d i r e c t i f one species changes the environment so t h a t the other species cannot or w i l l not l i v e t h e r e. The most obvious such change would be u t i l i z a t i o n of the a v a i l a b l e food or n e s t i n g m a t e r i a l s un-t i l they are present i n q u a n t i t i e s submarginal f o r the other s p e c i e s . Because oreas i s more a r b o r e a l i n a d a p t a t i o n and h a b i t than artemisiae and gambeli i t s e f f e c t i v e h a b i t a t i n a wooded area i s much l a r g e r than t h a t of the other forms, and t h i s may give i t a commanding competitive advantage. A more l i k e l y e x p l a n a t i o n f o r the absence of manicu-l a t u s from such h a b i t a t s as the r a v i n e at Wright's i s t h a t the species i n t e r a c t d i r e c t l y , because oreas could make the environment t o t a l l y u n s u i t a b l e f o r maniculatus only be r e -ducing i t s o v e r a l l value to i t s e l f . A r t e misiae may a v o i d places occupied by oreas or t h e r e may be d i r e c t c o n f l i c t between i n d i v i d u a l s of the two s p e c i e s . That i s , competi-t i o n may be f o r space. Peromyscus i s not t e r r i t o r i a l , and the home ranges of i n d i v i d u a l s o v e r lap widely (e.g. B l a i r 1942, McCabe and B l a n -chard 1950). However, the nest i t s e l f i s defended, and t h i s may act t o keep a p o p u l a t i o n dispersed where there are l i m i t e d 171. numbers of nest s i t e s . McCabe and Blanchard have p o s t u l a t e d t h a t the a v a i l a b i l i t y of s u i t a b l e nest s i t e s i s a bas i c popu-l a t i o n c o n t r o l i n Peromyscus. They b e l i e v e t h a t a young mouse seeking t o e s t a b l i s h i t s e l f i n a strange area a f t e r l e a v i n g i t s o r i g i n a l home may be dr i v e n from a l l s u i t a b l e nest s i t e s by the occupants and i n the absence of an accep-t a b l e home may simply d i e . I have no evidence t h a t t h i s occurs, but something of the s o r t may be r e s p o n s i b l e f o r keeping a r t e m i s i a e out of h a b i t a t s occupied by oreas. B l a i r (1953, 1954) found t h a t members of two species of Peromyscus tended to s e l e c t mates of t h e i r own species i n the l a b o r a t o r y , w h i l e members of d i f f e r e n t subspecies of maniculatus mated at random. I n the breeding experiments described above there was no evidence of species or subspecies d i s c r i m i n a t i o n . F i g h t i n g , m u t i l a t i n g , and k i l l i n g were com-mon, but seemed to have no r e l a t i o n t o race or sex. However i t i s p o s s i b l e , i f not probable, t h a t under n a t u r a l c o n d i t i o n s such d i s c r i m i n a t i o n does occur. I f so, the r e l a t i v e advantage of the two species must be i n d e l i c a t e balance, f a v o r i n g oreas i n one h a b i t a t , a r t e m i s i a e i n another, and i n a t h i r d being so n e a r l y equal that both species can l i v e side by s i d e . T h i s c o n s i d e r a t i o n of the e c o l o g i c a l r e l a t i o n s of oreas and maniculatus began with a h i g h l y s i m p l i f i e d d e s c r i p t i o n of the h a b i t a t s where these species were found to l i v e and ended w i t h s p e c u l a t i o n about the reasons f o r t h i s h a b i t a t 172. d i s t r i b u t i o n . The reasons undoubtedly are many and complex, but I b e l i e v e t h a t the evidence from t h i s and other s t u d i e s p o i n t s to behaviour as the key to h a b i t a t d i s t r i b u t i o n i n Peromyscus. The mice choose c e r t a i n h a b i t a t s and avo i d o t h e r s . The r e a c t i o n to c e r t a i n unknown f e a t u r e s of the environment probably i s an innate c h a r a c t e r i s t i c of the rac e . I f i t i s i n f l u e n c e d by the presence of another species we may say that i n t e r s p e c i f i c competition occurs. I n some places and at some times t h i s may be the primary f a c t o r con-t r o l l i n g d i s t r i b u t i o n , while other environmental f a c t o r s act p r i m a r i l y by c o n t r o l l i n g the c o n d i t i o n s of competition. E. DISTRIBUTIONAL AND EVOLUTIONARY HISTORY Peromyscus oreas has developed s u b s t a n t i a l , perhaps complete, r e p r o d u c t i v e i s o l a t i o n from P. maniculatus. We b e l i e v e t h a t r e p r o d u c t i v e i s o l a t i o n can a r i s e o n l y during geographic i s o l a t i o n (Mayr 1942) and i t seems l i k e l y t h e r e -f o r e t h a t at some time i n the f a i r l y recent past t he parent stock of oreas was separated from other stocks of manicula-tus long enough f o r reproductive i s o l a t i o n to develop. The most l i k e l y time f o r such i s o l a t i o n i s the l a s t g l a c i a l p e r i o d , which has had profound e f f e c t s on the e v o -l u t i o n of many kinds of animals i n the Northwest. T h i s ac-count of the g l a c i a l h i s t o r y of t h i s r e g i o n i s drawn from many sources, notably conversation with Dr. W. H. Mathews 173. of the Department of Geology and. Geography of the U n i v e r s i t y of B r i t i s h Columbia. Almost a l l of B r i t i s h Columbia and the northern h a l f of Washington were covered by a t h i c k i c e sheet (the Vashon-Wisconsin) as r e c e n t l y as 12,000 years ago, and the present b i o t a has developed since then. The ranges of many p l a n t s and animals are s t i l l i n the process of readjustment, d i s -t r i b u t i o n a l l i m i t s s h i f t i n g n o r t h or south as time and s l i g h t c l i m a t i c changes permit. At the g l a c i a l maximum a l l of B r i t i s h Columbia was under i c e , except f o r i s o l a t e d mountain peaks. The i c e sheet extended south on the west side of the Cascades to the south-ern end of Puget Sound, and on the east side i n t o northern Washington. The Cascades of northern Washington were com-p l e t e l y covered, except f o r i s o l a t e d peaks, but i n southern Washington and i n Oregon only i s o l a t e d v a l l e y g l a c i e r s were present. Most of the Olympic P e n i n s u l a was not g l a c i a t e d , except f o r v a l l e y g l a c i e r s i n the mountains. C e n t r a l Alaska was not g l a c i a t e d , but the e n t i r e southern coast of the Ter-r i t o r y was. Peromyscus i s not a boreal animal, and i t almost s u r e l y c o u l d not have survived t he g l a c i a l p e r i o d e i t h e r i n c e n t r a l A l a s k a , as some mammals d i d , or on i s o l a t e d peaks w i t h i n the g l a c i a t e d areas f a r t h e r south. I t s mainland d i s t r i b u t i o n must have been l i m i t e d to the area south of the i c e sheet. 174. A l l the races of the Northwest have entered the r e g i o n s i n c e the end of the l a s t g l a c i a t i o n , the d i f f e r e n t races e i t h e r coming i n from d i f f e r e n t d i r e c t i o n s , f o l l o w i n g each other i n s e r i e s , or developing i n s i t u i n response to l o c a l e n v i -ronmental c o n d i t i o n s . There i s reason t o b e l i e v e t h a t each of these processes has occurred i n the Northwest. P. m. austerus of western B r i t i s h Columbia and Wash-in g t o n i s s i m i l a r t o and undoubtedly derived from P. m. r u -bidus of the coast of Oregon and northern C a l i f o r n i a . I t i s one of the many races of mammals confined to the North-west coast. The Peromyscus of southern Washington east of the Cascades are not d i s t i n g u i s h a b l e from the populations of eastern Oregon and c e n t r a l C a l i f o r n i a , and the name P. m. gambeli i s at present a p p l i e d to a l l of them. Those i n Washington undoubtedly entered from adjacent p a r t s of Ore-gon. P. m. a r t e m i s i a e extends from c e n t r a l Washington t o c e n t r a l B r i t i s h Columbia, and east to western Montana. I t al s o occurs f a r t h e r south i n Idaho and eastern-most Oregon and i n the Blue Mountains of southeastern Washington. I t probably entered Washington and B r i t i s h Columbia from the southeast, i f i t i s a phylogenetic u n i t a t a l l . P. m. macrorhinus i s the race most s i m i l a r t o oreas, and the one whose o r i g i n i s most d i f f i c u l t t o e x p l a i n . I f i t i s r e p r o d u c t i v e l y i s o l a t e d from oreas, which has not been proven, i t must have been g e o g r a p h i c a l l y i s o l a t e d from i t at 175. some time. I t s e n t i r e present range i s thought t o have been under i c e during the l a s t g l a c i a t i o n . I t i s q u i t e d i s t i n c t from a l l other mainland races of maniculatus and none of them can c o n v i n c i n g l y be designated as i t s ancestor. Other p o s s i b i l i t i e s are ( l ) t h a t i t i s a p o s t - g l a c i a l d e r i v a t i v e of oreas, from the south, and (2) t h a t i t i s de-r i v e d from P. m. keeni of the Queen C h a r l o t t e I s l a n d s . These i s l a n d s are adjacent to the range of macrorhinus, but are separated from i t by 30 :'.or more miles of water. There i s evidence that they were not e n t i r e l y g l a c i a t e d at the Vashon-Wisconsin maximum, and they may have served as a r e -fuge f o r Peromyscus at t h a t time. Macrorhinus i s more l i k e keeni than l i k e any of the other neighboring races of mani-c u l a t u s . I t a l s o i s very much l i k e oreas, d i f f e r i n g mainly i n i t s l a r g e r s i z e and r e l a t i v e l y s horter t a i l . I t i s c e r t a i n -l y r a c i a l l y d i s t i n c t , but s p e c i f i c d i s t i n c t n e s s has not been demonstrated. The f a i r l y uniform character of both races throughout most of t h e i r ranges and the apparent occurrence of both forms at R i v e r s I n l e t suggest t h a t they are s p e c i f i -c a l l y d i s t i n c t , but e i t h e r race may have been d e r i v e d o r i g i -n a l l y from the o t h e r . Oreas i t s e l f occurs throughout western Washington and f a r up the coast and mountains i n B r i t i s h Columbia. There i s no evidence t h a t i t has ever occurred north of i t s present 176. l i m i t , east of the Cascades-Coast Range, or south of the Columbia R i v e r . I t i s probable t h a t i t survived the l a s t g l a c i a t i o n i n southern Washington, developed i t s present morphological d i s t i n c t n e s s and rep r o d u c t i v e i s o l a t i o n during t h a t time, and sin c e the r e t r e a t of the g l a c i e r s has ex-tended i t s range f a r t h e r north. T h i s hypothesis r e q u i r e s the assumption that the C o l -umbia R i v e r was a great enough b a r r i e r t o d i s p e r s a l to pre-vent gene f l o w between the populations of Washington and Oregon. At the present time i t i s enough of a b a r r i e r to permit the maniculatus populations of western Washington t o remain somewhat d i s t i n c t from those of western Oregon. Another p o s s i b i l i t y i s t h a t oreas o r i g i n a t e d i n Oregon from a stock i s o l a t e d from other Peromyscus populations by the presumably snow-covered Klamath Range of southern Oregon and northern C a l i f o r n i a . There i s no agreement as to the c o n d i t i o n s t h a t ex-i s t e d near the southern edge of the i c e sheet. Some wor-kers b e l i e v e t h a t a l l forms of l i f e were f o r c e d t o r e t r e a t f a r t o the south, which would have made i t impossible f o r Peromyscus to l i v e i n Washington at a l l . There seems to be an i n c r e a s i n g body of evidence, though, t h a t subalpine f o r e s t e x i s t e d c l o s e to the g l a c i a l border throughout the pe r i o d of g l a c i a t i o n . I f t h i s i s t r u e oreas could have sur-v i v e d the g l a c i a l p e r i o d i n southern Washington (or Oregon), 177. w h i l e a r t e m i s i a e , gambeli, and austerus (or t h e i r a n c e s t r a l s t o c k s ) , which do not l i v e I n such f o r e s t s , would have been f o r c e d f a r t h e r south. Dalquest (1948), who b e l i e v e d t h a t oreas i n t e r g r a d e s w i t h the races to the ea s t , i n t e r p r e t e d c e r t a i n c h a r a c t e r -i s t i c s of Peromyscus populations of Oregon, northeastern Washington, eastern B r i t i s h Columbia, the San Juan I s l a n d s of Washington, and Vancouver I s l a n d as i n d i c a t o r s of the genetic i n f l u e n c e of oreas. P. m. h o l l i s t e r i Osgood of the San Juan I s l a n d s i s g e o g r a p h i c a l l y i s o l a t e d and i t s r e l a t i o n t o maniculatus i s presumptive. P. m. i n t e r d i c t u s Anderson of Vancouver I s l a n d , which somewhat resembles oreas, i s contiguous w i t h P. m. angustus H a l l of that I s l a n d , which resembles austerus. They are s a i d to i n t e r g r a d e , but t h i s has not been demonstrated. P. m. a l p i n u s Cowan, a l s o r e -sembling oreas i n some ch a r a c t e r s , occupies a small range i n eastern B r i t i s h Columbia. I t i s completely surrounded by a r t e m i s i a e , but again i n t e r g r a d a t i o n has not been demon-s t r a t e d . I f these forms are g e n e t i c a l l y continuous w i t h mani-cu l a t u s they may a l l be deriv e d from the same parent stock as oreas or they may have developed t h e i r o r e a s - l i k e char-a c t e r s independently. I f they are not g e n e t i c a l l y c o n t i n -uous with maniculatus they may have been derived d i r e c t l y from oreas. I n the present s t a t e of our knowledge of these forms i t i s f u t i l e t o speculate f u r t h e r on t h e i r h i s t o r y . 178. In summary, I b e l i e v e t h a t the oreas stock survived the l a s t g l a c i a l p e r i o d i n southern Washington, w h i l e a l l other forms were f o r c e d f a r t h e r south. During t h i s time, probably many thousands of years, oreas developed r e p r o d u c t i v e c h a r a c t e r i s t i c s which have reduced 'or e n t i r e l y prevented i n t e r b r e e d i n g with other races of Peromyscus. With the r e -t r e a t of the g l a c i e r s and the re-establishment of s u i t a b l e p l a n t cover i n the formerly g l a c i a t e d area oreas extended i t s range f a r t h e r n o r t h . I n the meantime other races r e -invaded the area from the south and southeast, and i n many places occupied t e r r i t o r y a l s o occupied by or eas. I n the 10,000 to 15,000 years since t h i s occurred the two species have been p a r t l y sympatric but have maintained t h e i r gene-t i c d i s t i n c t n e s s . F. LIFE HISTORY I . REPRODUCTION 1. Breeding season The l i m i t e d breeding data a v a i l a b l e f o r oreas and maniculatus are given i n F i g u r e 48. Data f o r three years and many l o c a l i t i e s are combined. Breeding males are de-f i n e d as those w i t h t e s t e s eight mm. or more l o n g . Jame-son (1950) s t a t e s t h a t i n l a t e summer and f a l l t e s t e s are re g r e s s i n g and though they may be more than eight mm. long the animals are not f e r t i l e . He says that such i n d i v i d u a l s 179 <? oreas CD P O S T - P A R T U M • B R E E D I N G • N O N - B R E E D I N G 9 oreas maniculatus X L JJLIJI. Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A Y A 8 - IS- 22 - 2 9 -14 21 28 9 5- 13- 2 0 -12 19 56 27- 4 - II- 18- 2 5 -3 10 17 24 31 8- 15-14 21 2 l i 2 9 i F i g u r e 48. Breeding status of Peromyscus, May t o October. Each, square represents one i n d i v i d u a l . 180. may be recognized by t h e i r o l i v e - c o l o r e d , f l a c c i d , more slender t e s t e s . I have seen many b l u i s h or g r e e n i s h t e s t e s , throughout the summer, but none were more than f i v e mm. l o n g . The eight mm. d i v i d i n g l i n e i s somewhat a r b i t r a r y , but most males have t e s t e s l e s s than s i x mm. long or more than nine mm. long and can be c l a s s i f i e d as breeding or non-breeding w i t h some confidence. Non-breeding females are those t h a t are n e i t h e r preg-nant nor show p l a c e n t a l s c a r s . Breeding females are those t h a t are c l e a r l y pregnant; females i n e a r l y pregnancy would be recorded as non-breeding. Post-partum females are those t h a t are l a c t a t i n g or show f r e s h p l a c e n t a l s c a r s . The e a r l i e s t records (May) f o r both species are of animals i n breeding c o n d i t i o n . The June 27-July 3 c o l l e c -t i o n s i n c l u d e d both a young oreas and a young maniculatus t h a t were post-partum. The g e s t a t i o n p e r i o d i s three to f o u r weeks, age at m a t u r i t y i s about e i g h t t o nine weeks, t h e r e f o r e these two young females must have been conceived by mid-March. Oreas continued t o breed through J u l y , but no breeding animals of e i t h e r sex were taken a f t e r the end of t h a t month. Maniculatus continued t o breed at l e a s t u n t i l mid-August. The Haney and Loon Lake samples are not included i n the f i g u r e because t h e i r taxonomic s t a t u s i s u n c e r t a i n . Two males from Loon Lake trapped on September 4 were i n breeding 181. c o n d i t i o n ; a l l other animals i n these samples were e i t h e r non-breeding or post-partum. T h i s scanty evidence suggests t h a t both oreas and maniculatus begin to breed i n l a t e win-t e r , but t h a t maniculatus may continue to breed f o r s e v e r a l weeks a f t e r oreas has ceased t o breed. There i s reason to b e l i e v e t h a t there i s a f a l l breeding season, but apparent-l y i t had not begun by e a r l y October. Most of the " a d u l t " mice of l a t e September and e a r l y October were young of the year t h a t had entered age group 3 on the basis of t o o t h wear. These r e s u l t s are i n contrast to those of Howard (1949), who found t h a t more P. m. b a i r d i were born i n Octo-ber than i n any other month, that there was a lower peak i n A p r i l , and t h a t no mice were born i n December to March and few during the summer. 2. Age at m a t u r i t y F i g u r e 48 shows that animals born e a r l y i n the breed-i n g season (age group 2) are mature by June. Most mice born l a t e r i n the season are not mature by the end of the summer breeding season and thus apparently do not breed u n t i l l a t e i n the year or the f o l l o w i n g s p r i n g . No mice i n age group 1 were i n breeding c o n d i t i o n . According to C l a r k (1938), sexual m a t u r i t y comes at about 50 days of age i n females, at 60 i n males. 182. 3. L i t t e r s i z e I n oreas l i t t e r s i z e ranged from f i v e to nine and averaged 6.1, the d i s t r i b u t i o n being skewed s t r o n g l y to the l e f t . I n maniculatus l i t t e r s i z e ranged from two t o n i n e , averaging 5.6, w i t h approximately normal d i s t r i b u -t i o n . F i v e and s i x were the most frequent l i t t e r s i z e s i n both s p e c i e s . I I . POPULATION STRUCTURE Some idea of p o p u l a t i o n s t r u c t u r e can be gained from snap-trap data which are known to be unbiased, but musuem c o l l e c t i o n s u s u a l l y are biased by the c o l l e c t o r and cannot be used f o r p o p u l a t i o n a n a l y s i s . At best snap-trap data i n d i c a t e the s t r u c t u r e of the trappable p o p u l a t i o n . The most obvious non-trappable c l a s s i s young animals, which do not enter the catch u n t i l one or two months of age. 1. Age composition The r e l a t i v e frequency of the tooth-wear c l a s s e s from June through September i s shown i n Table XIV. The t a b l e i s based on those of my samples which i n c l u d e a l l the Peromys-cus trapped at a l o c a l i t y . Age group 1 never formed a l a r g e part of the c a t c h , but was present at a low l e v e l throughout the summer. The seven mice i n t h i s group which were caught i n September were caught e a r l y i n the month and probably were born l a t e i n J u l y . 183. Table XIV. Frequency of the tooth-wear groups i n the Pero-myscus. catch, June to September. Jun J u l Aug Sep Group No. 1o No. % No. 1o No. io 1 7 7.4 17 5.3 9 4.0 7 5.3 2 27 28 .7 165 51.2 159 70.7 68 51.1 ' 3 38 40.4 69 21.4 22 9.8 49 36.8 4 17 18.1 60 18.6 24 10.7 9 6.8 5 5 5.3 11 3.4 11 4.9 0 0 I n June group 2 was outnumbered by group 3, hut i n J u l y i t outnumbered group 3 by more than two to one and i n August by more than seven t o one. I n September i t s t i l l was more numerous, but by l e s s than two to one. The i n c r e a s i n g abundance of group 2 during the summer was a r e s u l t of i n -crement of mice born i n the s p r i n g , while group 3 was being depleted by death. By September the increment of group 2 i n d i v i d u a l s had been slowed down by the late-summer r e p r o -ductive h i a t u s and some i n d i v i d u a l s born e a r l y i n the season had entered group 3. Groups 4 and 5 always formed a s m a l l part of the ca t c h . Group 4 decreased i n r e l a t i v e abundance during the summer, but the data are too few t o be very meaningful. 2. Sex r a t i o The sex r a t i o of the catch f o r each age group i s given i n Table XV, based on samples which are known to be unbiased f o r sex by the c o l l e c t o r . I n both oreas and maniculatus 184. Table XV. Sex r a t i o of the catch at various ages. Group Sex oreas maniculatus N % N % 1 male 6 67 6 67 female 3 33 3 33 2 male 95 55 65 56 female 78 45 51 44 3 male 21 34 20 47 female 40 66 23 53 4 male 2 11 22 61 female 16 89 14 39 5 male 1 17 1 14 female 5 83 6 86 young males (groups 1 and 2) outnumber young females, but adult females outnumber adult males. Group 4 maniculatus are the only exception to t h i s . In oreas the percentage of males drops continuously from 67% i n group 1 to 11% i n group 4 . In group 5 the single male forms 17% of the catch. The percentage also drops steadily i n maniculatus, except for group 4 . The figures for groups 1, 2 , and 5 are re-markably close i n the two species, though i n groups 1 and 5 the numbers involved are too small to be r e l i a b l e . These figures represent the sex r a t i o of the catch, not of the population. In most rodents there usually i s a s l i g h t excess of males at b i r t h , which could explain the greater frequency of young males i n the catch. I t i s the general experience of small-mammal c o l l e c t o r s that males of a l l ages s l i g h t l y outnumber females i n the catch. This i s 185. thought to r e s u l t i n part from the f a c t that males seem to t r a v e l over l a r g e r areas and hence have a greater chance of f i n d i n g a t r a p . I n a study of P. m. g r a c i l i s B l a i r (1942) found t h a t while a d u l t males had s i g n i f i c a n t l y l a r g e r home ranges than adult females, young males had s l i g h t l y smaller home ranges than young females. Snyder (1956) found t h a t marked male P. leucopus con-s i s t e n t l y disappeared from h i s study area at a f a s t e r r a t e than females. For mice born i n the f a l l of 1949 the d i f f e r -ence was h i g h l y s i g n i f i c a n t . The l a s t capture of a male was at 23 weeks of age, of a female at 43 weeks of age. For mice born i n the s p r i n g and summer and i n the f a l l of 1950 the d i f f e r e n c e was s l i g h t . Disappearances r e s u l t e d from emigration as w e l l as death, but Snyder b e l i e v e s t h a t the observed d i f f e r e n c e s r e f l e c t a genuine d i f f e r e n c e i n death r a t e of the two sexes. The most s t r i k i n g instance of predominance of females i n my adult catches was at Wright's Ranch, where almost the e n t i r e i s o l a t e d p o p u l a t i o n of oreas was trapped d u r i n g a two-week period i n 1957. The sex r a t i o was approximately 50:50 i n young of the year (27 males, 30 females), but the a d u l t catch c o n s i s t e d e n t i r e l y of 12 females. One adul t f e -male was caught there seven weeks l a t e r , and two had been caught there i n 1956, but no ad u l t male oreas was caught at t h i s s t a t i o n at any time. I n 1956 four young males and f o u r 186. young females were caught there; t h i s i s the y e a r - c l a s s from which most of the 1957 a d u l t s were taken, and i t too seems to have had an i n i t i a l sex r a t i o of about 50:50. The preponderance of females i n the a d u l t catch might r e s u l t from greater s u s c e p t i b i l i t y to t r a p p i n g , but t h i s i s the opposite of the usual s i t u a t i o n . The f a i l u r e to f i n d any adult males i n the n e a r - t o t a l sample of cr eas from Wright's could h a r d l y be explained on t h i s b a s i s . These very l i m i t e d data suggest t h a t i n the Northwest females l i v e longer than males. The preponderance of males i n group 4 maniculatus i n d i c a t e s that f o r d i f f e r e n t species and d i f f e r -ent y e a r - c l a s s e s t h i s may not always be t r u e , as was a l s o suggested by Snyder's data. I I I . BEHAVIOUR The breeding experiment described above provided an opportunity t o make casual observations on the general be-haviour of c a p t i v e oreas, austerus, and a r t e m i s i a e . Repro-ductive behaviour has been considered i n S e c t i o n C. A l l the mice i n the colony remained w i l d throughout the p e r i o d of o b s e r v a t i o n . Y/hen d i s t u r b e d they showed one of f o u r r e a c t i o n s , i n order of decreasing frequency—cower-i n g , running, escape jump, and d i g g i n g i n the shavings on the bottom of the cage. On the average, oreas was d i s t i n c t -l y more a c t i v e and more nervous than austerus and a r t e m i s i a e , and i t used the escape jump more o f t e n . T h i s movements i s a 137. quick jump away from an alarming o b j e c t . When the cage was opened (by removing the top) some i n d i v i d u a l s of each race would jump as i f t r y i n g to escape, but these jumps were s e l -dom e f f e c t i v e . Only a few i n d i v i d u a l s a c t u a l l y escaped i n t h i s way, but some of these did so s e v e r a l times. The cages were made of wood and f o r s e v e r a l months the mice a c t i v e l y a t t a c k ed a l l i r r e g u l a r i t i e s i n the wood surface with t h e i r t e e t h and some of them succeeded i n making holes l a r g e enough to escape through. L a t e r t h i s a c t i v i t y was g r e a t l y reduced. I n the w i l d , Peromyscus i s almost e x c l u s i v e l y noctur-n a l , and the colony mice r e t a i n e d t h i s p a t t e r n of a c t i v i t y . "When observed during the day they were almost- almost always huddled together unless d i s t u r b e d , but at night they were w i l d l y a c t i v e . Night observations were made between 8:00 and 10:00 PM, the p e r i o d of greatest a c t i v i t y i n nature. A c t i v i t y increased markedly a f t e r sunset, although a b r i g h t e l e c t r i c l i g h t was burning i n the room, but i t d i d not reach i t s g r e a t e s t i n t e n s i t y u n t i l a f t e r 9*«00 PM, when the l i g h t was turned o f f . Some i n d i v i d u a l s made repeated back somer-s a u l t s — f l o o r t o w a l l t o top t o opposite w a l l to f l o o r . These somersaults would be continued f o r some time at the r a t e of perhaps one per second. In the morning the area around the cages was strewn with sawdust k i c k e d out by the mice d u r i n g the n i g h t . Peromyscus i s noted f o r i t s s o c i a l behaviour. Through the use of a r t i f i c i a l nest boxes Howard (1949) found t h a t i n 188. P. m. b a i r d i members of a f a m i l y u s u a l l y nest together, and th a t u n r e l a t e d i n d i v i d u a l s and even members of d i f f e r e n t species may be found i n the same nest. I n my colony a l l i n d i v i d u a l s i n a cage, re g a r d l e s s of ra c e , huddled together when not a c t i v e . Huddling i s thought to be a means of con-s e r v i n g heat. I t was my p r a c t i c e when p u t t i n g strange mice together always t o put them i n t o a cage th a t was strange t o both of them, to avoid i n t r o d u c i n g mice i n t o the e s t a b l i s h e d n e s t i n g t e r r i t o r i e s of o l d occupants. T h i s probably reduced the amount of f i g h t i n g which occurred when new combinations were made, but i t by no means e l i m i n a t e d i t . Many animals d i d not f i g h t , but many others d i d , and new cagemates were f r e -q u ently k i l l e d . U s u a l l y a l l f i g h t i n g had ended by the next day and the mice l i v e d together p e a c e f u l l y t h e r e a f t e r . There was d e f i n i t e s o c i a l dominance. Some i n d i v i d u a l s were dominant as soon as placed i n a cage with s e v e r a l strange mice, and chased the others around the cage. Those being chased sought p r o t e c t i o n by running, by c l i n g i n g t o the wire r o o f of the cage, or by l y i n g s u b m i s s i v e l y on t h e i r backs w h i l e under a t t a c k . The most submissive i n d i v i d u a l s would l i e s t i l l while p e r s i s t e n t l y nuzzled and perhaps even b i t t e n by dominant i n d i v i d u a l s . Some mice k i l l e d most of t h e i r cage mates, others k i l -l e d o n l y r a r e l y , and most never k i l l e d . One female artemi-189. s l a e k i l l e d s e v e r a l males and females of va r i o u s races be-f o r e being i s o l a t e d . When mated w i t h a male s e v e r a l weeks l a t e r she i n s t a n t l y dominated him and began a v i o l e n t a t -tack which he made no attempt to r e s i s t ; I separated them a f t e r s e v e r a l minutes. L a t e r a male art e m i s i a e k i l l e d sev-e r a l mates and att a c k e d others. He was placed w i t h the k i l -l e r female a nd a b r i e f but v i o l e n t f i g h t ensued. The male was v i c t o r i o u s , and l i v e d p e a c e f u l l y with the female f o r some time. She gave b i r t h t o a l i t t e r 25 days a f t e r the mating. The male continued t o l i v e i n the nest w i t h female and young, but when the young were two weeks o l d the f e -male was found dead and the young had been almost e n t i r e l y eaten. K i l l i n g s u s u a l l y occurred w i t h i n the f i r s t 24 hours a f t e r the mice were put together. None of the dead mice showed any gross p h y s i c a l i n j u r y , though the s k u l l s of some were bloody but unbroken. There i s a st r o n g suggestion that the deaths r e s u l t e d from nervous or p h y s i o l o g i c a l , rather, than p h y s i c a l , causes. T h i s would accord with the hypothe-s i s of MeCabe and Blanchard (1950) that Peromyscus may o f t e n d i e f o r p s y c h o l o g i c a l reasons. M u t i l a t i o n was as common as k i l l i n g , but i t occurred among e s t a b l i s h e d cagemates, r a t h e r than s t r a n g e r s . The most common form was l o s s of a hind l e g , though sometimes a f r o n t l e g was l o s t . One mouse l o s t i t s e n t i r e t a i l , and two l o s t 190. a l a r g e part of t h e i r noses. A l l the mice i n a cage would be found huddled q u i e t l y together on one day, a l l i n t a c t . S e v e r a l days l a t e r they would be huddled together as before, but one or more of them would have l o s t a l e g . Presumably the m u t i l a t i o n occurred at n i g h t , when the mice are a c t i v e . P o s s i b l e reasons f o r the m u t i l a t i o n are n u t r i t i o n a l d e f i c i -ency or inadequacy of space f o r a c t i v i t y . Most m u t i l a t i o n s occurred i n October and February, one and f i v e months a f t e r most of the mice were captured. The simultaneous occurrence of m u t i l a t i o n s i n a number of cages suggests t h a t a k i n d of f r e n z y may have run through the e n t i r e colony. None of the m u t i l a t e d mice died as a r e s u l t of t h e i r i n j u r i e s . No race or sex had a c o n s i s t e n t advantage i n domi-nance, k i l l i n g , or m u t i l a t i n g . A l l p o s s i b l e combinations of i n t e r a c t i o n s occurred. Artemisiae seemed t o be the most aggressive, austerus the l e a s t so, both i n t e r r a c i a l l y and i n t r a r a c i a l l y . Gr, DISCUSSION The systematic and e c o l o g i c a l r e l a t i o n s of P. oreas and P. maniculatus have been discussed at l e n g t h , c e r t a i n aspects of t h e i r l i f e h i s t o r y have been t r e a t e d b r i e f l y , and s p e c u l a t i o n has been made on t h e i r d i s t r i b u t i o n a l and e v o l u t i o n a r y h i s t o r y . A f a i r l y c l e a r p i c t u r e emerges— oreas i s not g e n e t i c a l l y continuous w i t h the surrounding 191. races of maniculatus and i t d i f f e r s from them i n many ways. There i s a large number of morphological characters by which i t d i f f e r s from most of them, though these characters are not so d i s t i n c t t h a t a l l i n d i v i d u a l s can be p o s i t i v e l y iden-t i f i e d . The h a b i t a t requirements of the two species o v e r l a p but are not i d e n t i c a l . Oreas i s d i f f e r e n t i n behaviour and physiology ( i n d i c a t e d by the apparent d i f f e r e n c e i n time of end of breeding season and by the f a i l u r e of oreas to breed i n my l a b o r a t o r y when maniculatus was doing so). We cannot p r o f i t a b l y speculate on the nature of the Peromyscus populations of the Northwest p r i o r to the l a s t g l a c i a t i o n . I t seems l i k e l y t hat during t h i s g l a c i a t i o n a s m a l l stock of Peromyscus su r v i v e d i n southern Washington and developed i n t o the form t h a t we recognize as oreas. At the same time i t developed i s o l a t i n g mechanisms which have kept i t g e n e t i c a l l y d i s t i n c t from maniculatus ever s i n c e . Since the end of the l a s t g l a c i a l p e r i o d maniculatus has re-entered Washington and B r i t i s h Columbia from the south (austerus and gambeli), and the southeast ( a r t e m i s i a e ) . There are many t h i n g s t h a t can keep two races from i n t e r b r e e d i n g , and a number of them may be a c t i n g to prevent h y b r i d i z a t i o n between oreas and maniculatus. The most o b v i -ous i s o l a t i n g mechanism i s a l l o p a t r y . Some oreas p o p u l a t i o n s are i n areas devoid of maniculatus, but over much of i t s range oreas i s sympatric w i t h t h a t s p e c i e s . The h a b i t a t 192. d i f f e r e n c e s of the two species provide another means of par-t i a l i s o l a t i o n , but again t h i s i s o l a t i o n i s incomplete. The extremes of the e c o l o g i c a l scale u s u a l l y are occupied by only one species i n the area of sympatry, but intermediate h a b i t a t s support both species side by s i d e . P a r t i a l tem-p o r a l i s o l a t i o n i s i n d i c a t e d by the s l i g h t d i f f e r e n c e i n breeding season shown by the f i e l d data, but the peak of the breeding season f o r both species seems to occur a t the same time. These mechanisms together would serve to keep most i n -d i v i d u a l s of the t o t a l oreas p o p u l a t i o n from breeding w i t h maniculatus v-. but, ;they are not s u f f i c i e n t to have prevented the swamping of oreas by maniculatus during the thousands of years t h a t they have been sympatric. Oreas could have r e -mained m o r p h o l o g i c a l l y d i s t i n c t through s u p e r i o r a d a p t a t i o n to l o c a l environmental c o n d i t i o n s even i f i t i n t e r b r e d f r e e l y w i t h other r a c e s , but only i f i t occupied an e x c l u s i v e geo-graphic range and contacted other races o n l y p e r i p h e r a l l y . There must be something about these species t h a t keeps them from i n t e r b r e e d i n g even when both of them are i n breed-i n g c o n d i t i o n at the same time and p l a c e . T h i s could be be-h a v i o u r a l or p h y s i o l o g i c a l - c y t o l o g i c a l . The experiments of B l a i r and others have shown that although c e r t a i n c l o s e l y r e l a t e d species of Peromyscus may be capable of producing f e r t i l e hybrids they tend t o choose mates of the same species. I t i s a l t o g e t h e r probable t h a t t h i s i s true of oreas and mani-193. c u l a t u s a l s o . The most l i k e l y mechanism of species recog-n i t i o n i n Peromyscus i s s m e l l , hut no work has been done t o demonstrate t h i s . The r e s u l t s reported by L i u show that oreas and mani-c u l a t u s w i l l mate i n the l a b o r a t o r y , but that young are r a r e l y produced by such matings. No i n f o r m a t i o n i s a v a i l -able on the mating preferences of these s p e c i e s , or on the occurrence of c o p u l a t i o n i n mated p a i r s . In the absence of such data we cannot determine the degree of i n t e r s t e r i l i t y r e s u l t i n g from p h y s i o l o g i c a l or c y t o l o g i c a l i n c o m p a t i b i l i t y . The poor s u r v i v a l r e c o r d of L i u ' s few hybrids and the s t e r i -l i t y of the only h y b r i d to reach breeding age suggest t h a t , while these species are p a r t i a l l y i n t e r f e r t i l e , t h e i r hy-b r i d s have poor v i a b i l i t y and may be s t e r i l e . T h i s would permit the appearance of F]_ hybrids i n n a t u r a l p o p u l a t i o n s , but would keep both parent stocks g e n e t i c a l l y pure. Thus we see t h a t oreas remains d i s t i n c t from manicu-l a t u s as a r e s u l t of the accumulated e f f e c t s of many h i g h l y v a r i e d i s o l a t i n g mechanisms. Geographic, e c o l o g i c a l , tem-p o r a l , and behavioural d i f f e r e n c e s between the species a l l serve t o reduce i n t e r b r e e d i n g . When i n t e r b r e e d i n g does occur the young do not s u r v i v e w e l l , and those hybrids t h a t reach m a t u r i t y may be s t e r i l e . Much of t h i s i s l a r g e l y s p e c u l a t i o n , but there i s some evidence f o r a l l of i t . The hypothesis presented above can e x p l a i n many of the t h i n g s known about the systematic r e l a t i o n s of these mice. 194. I t can e x p l a i n how a few oreas can l i v e i n the same t h i c k e t as a r t e m i s i a e at Copper Creek, surrounded by ar t e m i s i a e on the adjacent h i l l s , and yet ma i n t a i n t h e i r d i s t i n c t n e s s . I t can e x p l a i n how pure oreas, pure austerus, and apparent i n -termediates can occur together over most of western Washing-t o n i n s p i t e of the thousands of years during which they must have been l i v i n g together and i n t e r b r e e d i n g here, i f they do i n t e r b r e e d a t a l l . Some th i n g s cannot be explained by t h i s hypothesis, though. I t does not e x p l a i n why the Peromyscus p o p u l a t i o n at Pinewoods appears t o be an oreas x a r t e m i s i a e h y b r i d swarm, whil e at Goodfellow Creek s e v e r a l m i l e s away both races were found i n pure form, w i t h only one p o s s i b l e h y b r i d . I t does not e x p l a i n the p o s s i b l e intergrade character of the Hope and Loon Lake p o p u l a t i o n s . The systematic status of these and other p u z z l i n g populations i s not yet c l e a r , but i f they do c o n s i s t of int e r g r a d e s or hybrids i t means tha t the r e l a -t i o n s between the species vary from place t o p l a c e , and t h a t no one explanation can cover a l l p o p u l a t i o n s . When oreas was i s o l a t e d from maniculatus i t developed d i f f e r e n c e s i n behaviour and physiology which c o l l e c t i v e l y r e s u l t e d i n p a r t i a l r eproductive i s o l a t i o n between these spe-c i e s . When the species came i n t o contact a f t e r the end of the g l a c i a l p e r i o d t h i s r eproductive i s o l a t i o n was great enough t o permit them t o remain g e n e t i c a l l y d i s t i n c t . P a r-195. t i a l r e p roductive i s o l a t i o n i s an unstable c o n d i t i o n . There w i l l be a tendency f o r i t e i t h e r to become complete, prevent-i n g a l l gene exchange, or to break down a l t o g e t h e r , permit-t i n g f r e e gene exchange. . I t may be t h a t both of these pro-cesses have taken place i n d i f f e r e n t p a r ts of the area of sympatry of oreas and maniculatus. E s s e n t i a l l y complete i s o l a t i o n seems t o be the r u l e , but there are many p o s s i b l e hybrids i n the samples that I have examined and some samples may r e f l e c t a complete breakdown of i s o l a t i n g mechanisms. A s i m i l a r s i t u a t i o n i n Peromyscus has been described by McCarley (1954), as mentioned e a r l i e r . Another example i s provided by towhees of the genus P i p i l o i n Mexico by S i b -l e y (1950, 1954). Two species of t h i s genus are l a r g e l y a l l o p a t r i c , but they come i n contact i n s e v e r a l areas. I n at l e a s t one area they appear not t o i n t e r b r e e d , i n others there i s some h y b r i d i z a t i o n , and i n s t i l l others there i s a complex mixture of recombinations of the sp e c i e s c h a r a c t e r s . As S i b l e y has pointed out, such s i t u a t i o n s provide e v i -dence f o r the theory t h a t species a r i s e through the accumula-t i o n of small genetic changes duri n g geographic i s o l a t i o n , r a t h e r than as a r e s u l t of s i n g l e l a r g e mutations. I f r e -productive i s o l a t i o n i s g r a d u a l l y acquired i t may be i n any stage of completeness when the races again come i n con t a c t . We may expect to f i n d examples ranging from complete i n t e r -f e r t i l i t y through various degrees of l i m i t e d i n t e r b r e e d i n g 196. to complete f a i l u r e to in t e r b r e e d along the zone of contact. Examples of intermediate stages i n development of reproduc-t i v e i s o l a t i o n are provided by P i p i l o , and, I b e l i e v e , by Peromyscus i n the Northwest. S i b l e y b e l i e v e s that h y b r i d i z a t i o n i n P i p i l o has r e -s u l t e d from human disturbance of the h a b i t a t . Man has de-stroyed the n a t u r a l v e g e t a t i o n and produced new h a b i t a t types i n which the two species have come together over a broad f r o n t . There i s no i n d i c a t i o n that such disturbance has been r e s p o n s i b l e f o r the apparent h y b r i d i z a t i o n between oreas and maniculatus. Most of the samples that I have examined are from areas t h a t have been i n f l u e n c e d to some extent by human a c t i v i t y , but there i s no c o r r e l a t i o n between degree of disturbance and occurrence of p o s s i b l y intermediate Pero-myscus populations. For i n s t a n c e , Loon Lake, where a pos-s i b l e intergrade p o p u l a t i o n was found, i s one of the l e a s t d i s t u r b e d areas. I f oreas were subject to the i n t r o g r e s s i o n of genie m a t e r i a l from the surrounding races of maniculatus the oreas p o p u l a t i o n at any l o c a l i t y should tend to resemble the race nearest t o i t . I n s t e a d , F i g u r e s 5, 13, and 23 show th a t oreas i s remarkably constant throughout i t s range, at l e a s t i n e x t e r n a l dimensions. The t a i l lengths and h i n d f o o t lengths of t h i s species from Wright's Ranch, where i t i s sympatric with a r t e m i s i a e , are almost i d e n t i c a l t o those of 197. the Denny sample, from areas where oreas occurs alone. The Goodfellow sample i s also from the zone of sympatry w i t h a r t e m i s i a e . I t has the s h o r t e s t mean t a i l and h i n d f o o t l e n g t h s , tending toward a r t e m i s i a e i n those c h a r a c t e r s , but i t has one of the greatest mean body l e n g t h s . The various races of maniculatus show greater geo-graphic v a r i a t i o n than does oreas. I n both austerus and a r t e m i s i a e the northern-most populations have longer bodies and hind f e e t than the other samples of those r a c e s , but not longer t a i l s . The greater body s i z e happens to f o l l o w Berg-mann's r u l e that northern races tend to be l a r g e r than r e -l a t e d southern ones, but there i s no general north-south c l i n e i n any dimension w i t h i n any of the races considered here. S e v e r a l species of Peromyscus appear to be c l o s e l y r e l a t e d to maniculatus (Osgood 1909, M i l l e r and K e l l o g g 1955). A l l of them have much smaller geographic ranges and show much l e s s morphological d i f f e r e n t i a t i o n than does mani-culatus . P. melanotis A l l e n and Chapman of Mexico apparent-l y i s i s o l a t e d from the Mexican races of maniculatus by a l -t i t u d i n a l d i s t r i b u t i o n . P. p o l i o n o t u s (Wagner) of the south-eastern U n i t e d States i s separated from maniculatus by a wide area i n which n e i t h e r occurs. P. s i t k e n s i s Merriam i s con-f i n e d to c e r t a i n i s l a n d s o f f the coast of B r i t i s h Columbia and southeastern A l a s k a . I t does not occur on i s l a n d s inha-198. b i t e d by maniculatus. P. s e j u g i s Burt and P. s l e v i n i M a i l -l i a r d are confined t o one or two i s l a n d s i n the Gulf of Mex-i c o . T h e i r status i s not known. P. oreas must now be added to t h i s l i s t . Apparently maniculatus i s not sympatric w i t h any of these species except oreas. The others are separated from i t by waterj a l t i t u d e , or simply unoccupied area, and con-sequently t h e i r s p e c i f i c s t a t u s cannot be determined d i r e c t -l y . Nothing i s known of the f e r t i l i t y r e l a t i o n s of manicu-l a t u s w i t h most of these s p e c i e s , but i t i s known to be r e -p r o d u c t i v e l y i s o l a t e d from p o l i o n o t u s i n the l a b o r a t o r y ( ( B l a i r and Howard 1944). A l l of these species are p e r i p h e r a l to maniculatus i n d i s t r i b u t i o n and apparently have been deri v e d from i t during some p e r i o d of i s o l a t i o n i n the past. S i t k e n s i s , s e j u g j s . and s l e v i n i are i n s u l a r forms and may never have been more i s o l a t e d than at present. P o l i o n o t u s was i s o l a t e d from mani-c u l a t u s by the e f f e c t s of P l e i s t o c e n e g l a c i a t i o n ( B l a i r 1950) and these forms have not come i n contact again. Oreas pro-bably was i s o l a t e d at the same time, but f o l l o w i n g the end of the g l a c i a l p e r i o d maniculatus extended i t s range n o r t h -ward and soon r e - e s t a b l i s h e d contact. These p e r i p h e r a l species are not d i s t i n g u i s h e d from maniculatus by any common c h a r a c t e r s , u n l i k e the examples given by Brown (1957) as evidence f o r c e n t r i f u g a l s p e c i a t i o n . 199. Rather, they most c l o s e l y resemble neighboring races of maniculatus, P o l i o n o t u s i s the sma l l e s t member of the maniculatus species group, and i s an extreme development of the s h o r t - t a i l members of t h a t group. S i t k e n s i s i s the l a r g e s t member, and i s an extreme development of the l a r g e races of the Northwest coast. Oreas of the same r e g i o n i s another large form. H. SUMMARY 1. Peromyscus oreas i s l a r g e l y r e p r o d u c t i v e l y i s o -l a t e d from P. maniculatus. H y b r i d i z a t i o n may occur, and there may be int e r g r a d e populations i n some p l a c e s , but both species were found i n pure form at many p l a c e s . T h e i r ranges overlap w i d e l y , but the species maintain t h e i r i d e n -t i t y . T herefore, oreas i s removed from the species manicu-l a t u s and r e s t o r e d to f u l l s p e c i f i c s t a t u s . 2. The range of oreas overlaps those of P. m. a r t e -misiae and P. m. gambeli i n a zone of v a r i a b l e width on the east side of the Cascade Range. Oreas and P. m. aus-t e r u s occur together i n much of western Washington, but i n only a narrow zone i n B r i t i s h Columbia. Oreas i s absent from the F r a s e r D e l t a and much of the Puget Sound lowlands; austerus i s absent from the western part of the Olympic Pe-n i n s u l a . Maniculatus does not occur i n the higher p a r t s of the Cascades, but the i n t e r i o r and c o a s t a l races intergrade 200. along r i v e r v a l l e y s which, cut through the mountains. 3. I n the l a b o r a t o r y a r t e m i s i a e and austerus produced f e r t i l e h y b r i d s , but oreas f a i l e d to breed. Other i n v e s t i -g ators have had d i f f i c u l t y i n o b t a i n i n g oreas x maniculatus h y b r i d s , and such hybrids have shown low v i a b i l i t y and may be s t e r i l e . 4. Oreas i s p a r t i a l l y i s o l a t e d from maniculatus i n the zone of sympatry by d i f f e r e n t h a b i t a t preferences. Both species have more r e s t r i c t e d h a b i t a t d i s t r i b u t i o n i n the zone of sympatry than where each occurs alone. I t i s sug-gested t h a t t h i s r e s t r i c t i o n may r e s u l t i n part from i n t e r -s p e c i f i c competition. 5. Oreas probably developed reproductive i s o l a t i o n d uring the l a s t g l a c i a l p e r i o d , which i t may have survived i n southern Washington while other stocks of Peromyscus were f o r c e d f a r t h e r south. 6 . S p r i n g and e a r l y summer are the peak of the breed-i n g season, and there i s no breeding i n l a t e summer. Oreas ceases t o breed before maniculatus does. Mice born e a r l y i n the season breed before the end of the season. L i t t e r s i z e i s u s u a l l y f i v e or s i x . 7. I n June a d u l t s outnumber young of the year, but by J u l y t h i s i s reversed and i n August young are f a r more numer' ous. Young males are s l i g h t l y more common i n the catch than young females, but adult females outnumber a d u l t males, i n d i ' 201. e a t i n g t h a t females survive b e t t e r than males. Only minor behavioural d i f f e r e n c e s between these species have been noted, but species d i s c r i m i n a t i o n i s expected on the basis of work done by other i n v e s t i g a t o r s . 8 . Oreas i s i s o l a t e d from maniculatus i n part by space, by h a b i t a t , by breeding season, and apparently by p s y c h o l o g i c a l and p h y s i o l o g i c a l - c y t o l o g i c a l i n c o m p a t i b i l i t y . The e f f e c t i v e n e s s of these i s o l a t i n g mechanisms seems t o vary from place to pla c e . I n places there i s no i n t e r b r e e d -i n g , i n others few t o many hybrids may be found, and i n s t i l l others t h e r e may be intergrade p o p u l a t i o n s . T h i s i s i n t e r p r e t e d as evidence that oreas had developed only par-t i a l r e p r o d u c t i v e i s o l a t i o n while g e o g r a p h i c a l l y i s o l a t e d , and that since contact w i t h maniculatus has been r e - e s t a b -l i s h e d t h i s r e p r o d u c t i v e i s o l a t i o n has been r e i n f o r c e d i n most places but has broken down i n o t h e r s . 9 . Oreas i s one of a s e r i e s of species which have been derived from maniculatus around the periphery of i t s range. Apparently a l l have o r i g i n a t e d while g e o g r a p h i c a l l y i s o l a t e d . 2 0 2 . Appendix 1 . E x t e r n a l dimensions of f i v e races of Peromyscus. Race N OR TL £ Body length: oreas 119 78--100 90.45 £ 0 .42 gambeli 21 75--90 83.24 £ 1.04 art e m i s i a e 118 71--104 90.36 £ 0.65 austerus 184 70--100 86.04 £ 0.46 macrorhinus 37 83--108 96.86 £ 1.90 T a i l length: oreas 119 100- -126 112 .92 £ 0 . 5 5 gambeli 21 70- -95 7 S . 3 8 £ 1.32 a r t e m i s i a e 118 61--95 7 9 . 8 9 £ 0 . 5 8 austerus 184 70- -103 88 .72 £ 0 . 4 9 macrorhinus 37 100- -121 110 .22 £ 0 .88 Hind f o o t l e n g t h : oreas 119 21--25 23.16 £ 0.07 gambeli 21 19--22 20.26 £ 0.18 artemisiae 118 19--23 20 . 52 £ 0.07 austerus 184 18--23 20.70 £ 0.06 macrorhinus 37 21--25 23.30 £ 0.16 203. Appendix 2. L o c a t i o n of s t a t i o n s and source of m a t e r i a l s . The approximate l o c a t i o n of each s t a t i o n has been given i n the t e x t . T h i s appendix gives the l o c a t i o n of my own c o l -l e c t i n g s t a t i o n s , the approximate e l e v a t i o n of s t a t i o n s over 500 f e e t , and the source of the specimens which I have exam-ined. S t a t i o n s are l i s t e d i n the order i n which they are t r e a t e d i n S e c t i o n C. Numbers r e f e r t o Maps 1 and 2. Sources of m a t e r i a l s are: DS - Donald Smith MFJ - Mary P. Jackson MVZ - Museum of Vertebrate Zoology, Berkeley NMC - N a t i o n a l Museum of Canada, Ottawa PM - B r i t i s h Columbia P r o v i n c i a l Museum, V i c t o r i a UBC - U n i v e r s i t y of B r i t i s h Columbia Museum of Zoology, Vancouver USNM - United States N a t i o n a l Museum ( i n c l u d i n g B i o l o -g i c a l Survey c o l l e c t i o n ) , Washington WAS - Walter A. Sheppe WSM - Washington State Museum, S e a t t l e oreas - gambeli Mosquitoe Lake— 4 0 0 0 f t ; MVZ. 1. Ice Caves—2800 f t ; MVZ. • Cayuse Meadow—3800 f t ; MVZ. 2. Twin B u t t e s — 4 3 0 0 f t ; MVZ. 3. Bingen—no specimens seen. 204. 4. Grand Dalles—USNM. 5. Wishram~MVZ. 6. M a r y h i l l — M V Z . M i l l e r ' s I s l a n d — M V Z . Roosevelt—MVZ. 7. Husum—el. ?; USNM. 8. Trout lake —1940 f t ; USNM. 9. Satus Pass—-3200 f t ; MVZ. 1 0 . Yakima—1000 f t ; MVZ. S e l a h — n e a r Yakima; WSM. Moxee—near Yakima; MVZ. 11. Gotchen C r e e k — 5500 f t ; USNM. 11. Beaver S p r i n g s — 3 8 0 0 f t ; USNM. 11. Two mi l e s southwest Conrad Meadows—4200 f t ; USNM. 12. S i g n a l Peak—4000 f t ; USNM. 13. Dog Lake—4200 f t , two mil e s east of "White Pass on State Route 5; WAS. Goose P r a i r i e — 3 3 0 0 f t ; USNM. 1 4 . R i v e r Bend—2500 f t ; camp on T i e t o n R i v e r , 18 m i l e s east of White Pass on State Route 5; WAS. 15. Cottonwood—2300 f t , camp on Baches R i v e r 39 m i l e s east of Chinook Pass on U.S. Route 410; WAS. 16. Glear Lake—3300 f t , r e s e r v o i r on T i e t o n R i v e r e i g h t m i l e s east of White Pass; WAS. 17. American P o r k s — 2 8 0 0 f t , j u n c t i o n of American and Bumping R i v e r s ; WAS. 2 0 5 . 18. Pleasant V a l l e y — 3 3 0 0 f t , camp on American R i v e r 19 mi l e s east of Chinook Pass; WAS. 19. Easton—2200 f t , north bank of Yakima R i v e r 21 m i l e s east of Snoqualmie Pass; WAS. South bank ? —USNM. 20. Lake K e e c h e l u s —2 5 0 0 f t ; USNM. 21. C r y s t a l S p r i n g s — 2 3 0 0 f t , camp 11 mi l e s east of Sno-qualmie Pass on U.S. Route 10; WAS. oreas - ar t e m i s i a e 2 2 . Wenatchee—700 f t ; USNM. 2 3 . Chelan—1200 f t ; WSM. 2 4 . Stehekin—1100 f t ; USNM. 25. Lyman Lake—5500 f t ; USNM. 26. Cascade Tunnel—3400 f t ; USNM. 2 7 . Hart L a k e — e l . ?; USNM. O r o v i l l e — 1 0 0 0 f t ; USNM. 28. Twisp—1600 f t ; USNM. 29. C o n c o n u l l y —2 3 0 0 f t ; USNM. 3 0 . Mazama—2100 f t ; USNM. 31. Loomis—1500 f t ; USNM. 3 2 . Snowshoe Camp, Chopaka Mt.—5700 f t ; USNM. Bauerman Ridge—65OO f t ; USNM. Hannegan Pass—4300 f t ; USNM. 3 3 . Canyon Creek—2800 f t ; USNM. 3 4 . Ruby Creek—2000 f t ; USNM. 35. Barron—5000 f t ; USNM. 206. 36. A l l i s o n Pass—4300 to 4400 f t , at Cascade summit on Hope-Princeton Highway; DS, WAS. 37. Gibson Pass—4500 to 5000 f t , on Cascade summit south of A l l i s o n Pass; WAS. Co l d s p r i n g Camp—4000 f t , on Hope-Princeton Highway f o u r m i l e s east of A l l i s o n Pass; WAS. 38. Timber l i n e V a l l e y — e l . ?; PM. 39. Pinewoods—4000 f t ; Cambie Camp, Ranger S t a t i o n , and v i c i n i t y , on Hope-Princeton Highway f i v e m i l e s east of A l l i s o n Pass; DS, PM, UBC, WAS. 40. Goodfellow Creek—3600 f t , on Hope-Princeton Highway s i x t o eight m i l e s east of Pinewoods; WAS. 41. Copper Creek—3100 f t , near mouth of creek; WAS. Two mi l e s north of Copper Creek—3700 f t , on Hope-Princeton Highway; WAS. Sunday Summit—4200 f t , on highway f i v e m i l e s n o r t h of Copper Creek; WAS. 42. Tupper's M i l l — 3 8 0 0 f t , v i c i n i t y of Western I n t e r i o r Sawmill, 13 m i l e s south of P r i n c e t o n on Hope-Princeton Highway; WAS. 43. Wright's Ranch—2800 f t , near highway three m i l e s south-west of P r i n c e t o n ; WAS. One mile south of Princeton—2 3 0 0 f t , on west bank of S i m i l -kameen R i v e r ; WAS. 44. Princeton G o l f Club—2100 f t , two mi l e s east of P r i n c e -* ton; WAS. 207. 45. Okanagan—1200 f t ; PM. 46. Osoyoos—1000 f t ; PM, UBC. 47. Treasure Mountain—4700 f t , S i l v e r H i l l Mine on south side of mountain, near head of Tulameen R i v e r ; WAS. 48. Glimpse Lake—3800 f t ; UBC. 49. Kamloops—1200 f t ; UBC, USNM. 50. F i v e miles east of Boston Bar—2500 f t , on log g i n g road n o r t h of Anerson R i v e r ; WAS. 51. L y t t o n — 6 0 0 f t ; MVZ, PM. B o t a n i e — e l . ?; PM, USNM. 52. Ashcroft—1 2 0 0 f t ; USNM. 53. L i l l o o e t — 8 0 0 f t ; NMC, PM. 54. M c G i l l i v r a y Creek—5000 f t ; NMC. Blackwater L a k e — e l . ?; PM. 55. Minto C i t y (Minto Mine)—2500 f t ; MVZ. 56. B i g Bar Lake —3500 f t ; PM. 57. A l e x i s Creek—2000 f t ; MVZ. 58. Kleena Kleene—3000 f t ; MVZ. 59. Nimpo Lake—3525 f t ; UBC. oreas - austerus 60. Cathlamet—USNM. 61. Skamokawa—MVZ. 62. Chinook—MVZ. 63. Ilwaco—USNM. 64. Long Beach—USNM. 65. Long Island—USNM. 208., 66. O y s t e r v i l l e — U S N M . 67. South Bend—MVZ. 68. T ok eland--USNM. 69. Oakvllle—USNM. C e d a r v i l i e — U S N M . 70. Aberdeen—USNM. 71. Lake Q u i n a u l t — e l . ?; USNM. 72. Lapush—USNM. 73. Forks—USNM. 74. Ozette L a k e — USNM. Sooez (Suez)—10 m i l e s south of Neah Bay; USNM. 75. Solduc R i v e r — e l . ?, below Hot Springs; USNM. 76. Neah Bay—USNM. 77. Elwha R i v e r — o n e ; USNM. Two from mouth of Boulder Creek, 560 f t ; USNM. Two from highway; MVZ. 78. Mount A n g e l e s — t w o from two mi l e s southwest, 6000 f t ; two from head of L i t t l e R i v e r , 5000 f t ; USNM. 12 m i l e s south of Po r t A n g e l e s — e l . ?; WSM. 79. Dungeness Hatchery—500 f t ; MVZ. 80. J u n c t i o n Dungeness and Greywolf R i v e r s — 8 0 0 f t ; MVZ. 81. Port Orchard—USNM. 82. A r i e t t a — M V Z . 83. Lake Cushman—el. ?; USNM. North Fork Skokomish R i v e r — e l . ?; USNM. 84. She I t on—USNM. 85. Skamania—USNM. 209. 86. Stevenson—USNM. 15 miles north of C a r s o n — e l . ?; USNM. 87. S p i r i t Lake—3200 f t ; USNM. 88. Vancouver, Wash.—USNM. 89. lh m i l e s west of Y a c o l t — 8 0 0 f t ; MVZ. 3 i m i l e s west, f i v e m i l e s n o r t h of Y a c o l t —500 f t ; MVZ. 90. Amboy—MVZ. 91. Kalama R i v e r — M V Z . 92. Kelso—MVZ. 93. C a s t l e Rock—USNM. 94. C h e h a l i s — USNM. E i g h t m i l e s west of C h e h a l i s — e l . ?; USNM. 95. La Wis Wis—1000 f t , on C o w l i t z R i v e r at j u n c t i o n of C l e a r Fork and Muddy Fork; WAS. 96. Rochester—USNM. 97. Tenino—USNM. 98. Olympia—USNM. N i s q u a l l y F l a t s — U S N M . 99. Steilacoom—USNM. 100. Tacoma—MVZ. S i x miles south of Tacoma—USNM. 101. Roy—USNM. 102. Kapowsin—USNM. • -103. Puyallup—USNM. 104. Mount Rainier—USNM. 105. Kent—MVZ, USNM. 210. 106. Vashon Island—USNM. 107. S e a t t l e — M V Z , WSM. 108. Kirkland—USNM. 109. Bothell—WSM. 110. Enumclaw—750 f t ; USNM. 111. Twin Greeks—1500 f t , on White R i v e r 15 m i l e s east of Enumclaw; WAS. 112. Denny Creek—2400 f t , camp two m i l e s west of Snoqualmie Pass on U.S. Route 10; WAS. 113. Monroe—WSM. 114. Index—USNM. 115. Four m i l e s south of Everett—USNM. 116. Arlington—WSM. 117. Oso—550 f t ; USNM. 118. D a r r i n g t o n — 6 0 0 f t ; USNM. 119. Whidby Island—USNM. 120. La Conner—USNM. 121. Mount Vernon—USNM. 122. H a m i l t o n — e l . ?; USNM. 123. Rockport — e l . ?; USNM. 124. Bellingham—WSM. 125. Blaine—USNM. 126. U.S. C a b i n — e l . ?; USNM. 127. Vancouver, B.C.—MFJ, MVZ, PM, UBC, USNM. 128. Huntingdon—UBC . Sumas—USNM. 211. 129. C u l t u s Lake—WAS c o l l e c t i o n from f i s h hatchery on east shore; others UBC. Vedder C r o s s i n g — P M . 130. R o b e r t s o n ' s — n o r t h bank of C h i l l i w a c k R i v e r two m i l e s east of Vedder C r o s s i n g ; WAS. 131. C h i l l i w a c k R i v e r 16 m i l e s east of Vedder C r o s s i n g — 1100 f t ; WAS. 132. Lihumitson Park (Lihumption, L i u m c h e n ) — e l . ?; NMC. 133. Welch P e a k — e l . ?; MVZ. 134. Wahleach Lake (Jones Lake)—2100 f t ; MVZ. 135. Hope—150 t o 900 f t , along highway from two miles west t o f o u r m i l e s east of Hope; WAS. 136. C o q u i h a l l a River—1 0 0 0 f t , on mountainside south of r i v e r , f i v e m i l e s northwest of Hope; WAS. 137. Upper Skagit River—2 0 0 0 to 2500 f t , along S k a g i t and Sumallo R i v e r s f o r two m i l e s above j u n c t i o n ; WAS. 138. Ross Lake—1700 f t , i n S k a g i t v a l l e y north of I n t e r -n a t i o n a l Boundary; PM, WAS. 139. Agassiz—USNM. 140. H a r r i s o n Lake—USNM. 141. Hatzic—USNM. 142. Haney—one m i l e n o r t h , 50 f t , on A l o u e t t e R i v e r ; three m i l e s n o r t h , 450 f t , at o f f i c e of U n i v e r s i t y of B r i t i s h Columbia Research F o r e s t ; WAS. 143. Loon Lake—1150 f t , f i v e m i l e s north of Haney; WAS. 144. Port Moody—USNM. 212. 145. Mount Seymour—elevations i n t e x t , a l l l i n e s near road; WAS. 146. North V a n c o u v e r — e l e v a t i o n s i n t e x t ; UBC. 147. Squamish—MVZ. 14S. Hopkins Landing—MVZ. 148. Gibsons Landing—USNM. 149. A l t a Lake—2100 f t ; UBC. 150. Lund—USNM. 151. Bute I n l e t — F a w n B l u f f ; NMC. 152. Loughborough Inlet—NMC . oreas - macrorhinus 153. Lowe I n l e t — P M , UBC. 154. Kynoch I n l e t — P M , UBC. 155. Tom Bay—PM. 156. Beaver S e i n i n g Grounds, Schooner Passage, F i t z h u g h Sound—PM. 157. Koeye R i v e r , F i t z h u g h Sound—PM, UBC. 158. Neekas Creek (Neekis R i v e r ) , Don P e n i n s u l a — P M . 159. R i v e r s Inlet—NMC . 160. Owikeno L a k e — NMC . 161. Kingcome I n l e t — N M C . gambeli - a r t e m i s i a e 162. Grant C o u n t y — e l . ?; WSM. 213. artemisiae - austerus Emory Creek—!five miles south of Yale, on Fraser River at mouth of creek; WAS. 163. Spuzzum—on Transcanada Highway 0-1 mile south of Alex-. andra Bridge; WAS. 164. Alexandra—camp at east end of Alexandra Bridge; WAS. 165. Keeler's M i l l (Blue Lake, Fishblue Lake)—1300 f t , 18 miles south of Lytton; WAS. artemisiae - macrorhinus 166. Anahim Lake—3500 f t ; MVZ, UBC. 167. Hagensborg—no specimens seen. 168. Stuie—460 f t ; MVZ, NMC. 169. Mount Brilliant—5500 to 6500 f t ; NMC. 170. Eutsuk Lake, west end—2900 f t ; PM. 171. Stikine River, at Dokdaon (Dock-da-on) Creek, Flood Glacier, Great G l a c i e r — e l . ?; MVZ. 214. Appendix 3« S t a t i s t i c a l methods. The bar graphs were drawn i n the manner suggested by Hubbs and Hubbs (1953). Mr. P i e r r e J o l i c o e u r was of great help i n planning the other s t a t i s t i c a l a nalyses, and c a l c u -l a t i o n s were made according to formulae s u p p l i e d by him: variance S 2 = H I x 2 - £ x ) 2 z N(N - 1) standard d e v i a t i o n S z standard e r r o r of mean = SX/JW covariance S = NSIxy - (Ix)(£y) x y N(N - 1) E l l i p s e s were c a l c u l a t e d t o include approximately 95$ of the i n d i v i d u a l s i n the sample ( t 2 = * 2 s 5.99, DP = ^  ): J ( s / - S y 2 } 2 / 4 ( S ^ ) 2 = b S x 2 / S y 2 / b = L X s x 2 r S y 2 - b = L 2 2 2 2 _ a x y / 1 r — J a L 2 - c 2 The coordinates of the major a x i s are given by: x - x / c i Y = 7 £ mc]_ The coordinates of the minor a x i s are given by: x = x £ mc 2 y = y £ c 2 215. Appendix 4. S c i e n t i f i c names of p l a n t s r e f e r r e d to i n t e x t . a l d e r aspen blueberry-cedar, red y e l l o w dogwood, western f i r , Douglas a l p i n e grand noble subalpine hemlock, mountain western j u n i p e r l a r c h , we s t e r n l u p i n e maple, broadleaf Douglas v i n e o s i e r , red p i n e , lodgepole ponderosa white Alnus sp. Populus tremuloides Vaccinium sp. Thu.ja p l i c a t a Chamaecyparis nootkatensis Gornus n u t t a l l i Pseudotsuga t a x i f o l i a Abies l a s c i o c a r p a A. grandis A. n o b i l i s A. a m a b i l i s Tsuga mertensiana T. h e t e r o p h y l l a Juniperus sp. L a r i x o c c i d e n t a l i s Lupinus sp. Acer macrophyllum A. glabrum A. o i r c i n a t u m Cornus s t o l o n i f e r a Pinus c o n t o r t a P. ponderosa P. O c c i d e n t a l i s poplar, black rhododendron rose sagebrush s a l a l spruce, Engelmann thimbleberry vaccinium, dwarf Populus t r i c h o c a r p a  Rhododendron c a l i f o r n i c u m  Rosa sp. Artemisia.' sp. G-aultheria s h a l l o n  P i c e a engelmanni  Rubus p a r v i f l o r u s  Vaccinium scoparium 217. LITERATURE CITED Anderson, R. M. 1946. Catalogue of Canadian recent mammals. Nat.Mus.Canada Bull . N o . 1G2, Ottawa. 238 p. Andrewartha, H. G. and L. C. B i r c h . 1954. The d i s t r i b u t i o n and abundance of animals. Univ.Chicago P r e s s , Chicago. 782 p. B l a i r , W. F. 1942. S i z e of home range and notes on the l i f e h i s t o r y of the woodland deer-mouse and eastern chipmunk i n northern Michigan. Jour.Mam. 23: 27-36. 1947. The occurrence of buff and gray pelage i n w i d e l y separated geographic races of the deer-mouse (Peromyscus  man i c u l a t u s ) . C o n t r i b . L a b . V e r t . B i o l . U n i v . M i c h i g a n 38. 13p. 1950. 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S u r v i v a l r a t e s , l o n g e v i t y , and popu l a t i o n f l u c t u a t i o n s i n the white-footed mouse, Peromyscus leuco-pus, i n southeastern Michigan. Misc.Publ.Mus.Zool.Univ. Mich. No. 95. 33 p. Sumner, F. B. 1929. The a n a l y s i s of a concrete case of i n t e r g r a d a t i o n betv/een two subspecies. Proc .Nat .Acad. S c i . 15: 110-120. S v i h l a , A. 1936. Development and growth of Peromyscus mani-culatus oreas. Jour.Mam. 17: 132-137. and Ruth D. S v i h l a . 1933. Mammals of C l a l l a m County, Washington. M u r r e l e t 14: 37-41. T a y l o r , W. P. and W. T. Shaw. 1929. P r o v i s i o n a l l i s t of land mammals of the State of Washington. Occ.Pap.Charles R.Conner Mus. 2:1-32. Whitaker, W. L. 1940. Some e f f e c t s of a r t i f i c i a l i l l u m i n a -t i o n on re p r o d u c t i o n i n the white-footed mouse, Peromys-cus leucopus noveboracensis. Jour.Exp.Zool. 83: 33-60. Wi l s o n , E. 0. and W. L. Brown, J r . 1953. The subspecies con-cept and i t s taxonomic a p p l i c a t i o n . S y s t . Z o o l . 2: 97-111. Map 1. C o l l e c t i n g stations i n Washington and southern B r i t i s h Columbia. Key i s given i n text and i n Appendix 2. Map 2. C o l l e c t i n g stations i n B r i t i s h Columbia. Key i s given i n text and i n Appendix 2. Map 3. Representative l o c a l i t i e s at which Peromyscus  oreas and P. maniculatus have been c o l l e c t e d i n western Washington and B r i t i s h Columbia. i eo 45 o o r e a s x m a n i c u l a t u s ® b o t h • q u e s t i o n a b l e in NORTH PACIFIC COAST SCALE I inch to 60miles 1:3,801,600 100 200 WERNERS EQUAL-AREA PROJECTION ® DRAWN S COPYRIGHTED 1950, by WILLIAM R. HEAD CARTOGRAPHY LABORATORY GEOGRAPHY DEPARTMENT UNIVERSITY OF WASHINGTON ® ® 

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