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Variation in an isolated population of shrews of the Vagrans-Obscurus group Jackson, Mary Fairfield 1951

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VARIATION IN AN ISOLATED POPULATION OF SHREWS OF THE VAGRANS-OBSCURUS GROUP. by MARY FAIRFIELD JACKSON A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF' MASTER OF ARTS in the Department of Zoology. We accept t h i s thesis as conforming to the standard required from candidates f o r the degree of MASTER OF ARTS Members of the Department of Zoology THE UNIVERSITY OF BRITISH COLUMBIA October, 1 9 5 1 ABSTRACT. A . s t u d y o f s h r e w s o f t h e g e n u s S o r e x w a s u n d e r t a k e n a t P o i n t G r e y , V a n c o u v e r , B . C . T r a p p i n g c o m m e n c e d i n O c t o b e r 1 9 4 9 a n d w a s c o n t i n u e d e x c e p t f o r b r i e f p e r i o d s u n t i l M a y 1951. A t o t a l o f 1 2 9 o s m a l l m a m m a l s , i n c l u d i n g $ 7 0 s h r e w s w j r e o b -t a i n e d d u r i n g t h e p e r i o d . I n t h e l a b o r a t o r y t h e a n i m a l s w e r e e x a m i n e d f o r p a r a s i t e s a n d c o n d i t i o n o f t h e r e p r o d u c t i v e s y s t e m . S t a n d a r d s k u l l a n d b o d y m e a s u r e m e n t s , a n d c o u n t s o f t h e n u m b e r o f c a u d a l v e r t e b r a e w e r e m a d e o n a l l s h r e w s . C o m p l e t e s e p a r -a t i o n o f t h e t T O - s p e c i e s o f s h r e w s r e p o r t e d t o b e p r e s e n t o n t h e c a m p u s ( S o r e x v a g r a n s a n d S o r e x o b s c u r u s ) w a s f o u n d t o b e i m p o s s i b l e o n t h e b a s i s o f t h e s e m e a s u r e m e n t s , e v e n i n h e n s e x a n d a g e o f t h e a n i m a l s w e r e c o n s i d e r e d . A n a r b i t r a r y s e p a r a t -i o n o f 95 p e r c e n t o f t h e m a t e r i a l b a s e d o n t a i l l e n g t h a n d l e n g t h o f t h e m a x i l l a r y t o o t h r ® w w a s a c h i e v e d . D i f f e r e n c e s i n p e l a g e w e a ? e a p p a r e n t , b u t n o t s u f f i c i e n t t o s e p a r a t e t h e t w o s p e c i e s . I n t e r g r a d a t i o n i n a l l m o r p h o l o g i c a l f e a t u r e s w a s t a k e n a s e v i d e n c e t h a t t h e t w o s p e c i e s a r e h y b r i d i z i n g t o a c o n s i d e r a b l e e x t e n t . S o m e e v i d e n c e t h a t t h e b r e a k d o w n o f m e c h a n i s m s i s o l a t i n g t h e t w o p o p u l a t i o n s h a s n o t b e e n c o m p l e t e i s p r e s e n t e d . H y b r i d i z a t i o n i n a l o c a l p o p u l a t i o n s u c h a s t h e o n e s t u d i ^ w a s n o t c o n s i d e r e d a s u f f i c i e n t b a s i s t o c h a n g e t h e s p e c i f i c s t a t u s o f S . v a g r a n s a n d 8. o b s c u r u s . F u r t h e r s t u d y o f t h e s e t w o s p e c i e s i n o t h e r a r e a s w h e r e t h e y c o e x i s t i n t h e s a m e h a b i t a t i s i n d i c a t e d . T A B L E O F C O N T E N T S . P a g e I N T R O D U C T I O N 1 A C K N O W L E D G E M E N T S 3 M E T H O D S 4 R E S U L T S H a b i t a t s a n d a s s o c i a t e s 9 S e a s o n a l v a r i a t i o n i n n u m b e r s 13 R e p r o d u c t i o n 1 4 S e x R a t i o s 1 4 R e p r o d u c t i o n i n t h e m a l e 15 R e p r o d u c t i o n i n t h e f e m a l e _ 19 P e l a g e v a r i a t i o n a n d m o l t 25 S u m m e r p e l a g e i n j u v e n i l e s 26 F a l l m o l t i n j u v e n i l e s . 2 8 W i n t e r p e l a g e 30 S p r i n g a n d s u m m e r m o l t s 31 S u m m e r p e l a g e i n a d u l t s 3 & C o l o u r a b n o r m a l i t i e s 37 Q u a n t i t a t i v e M o r p h o l o g i c a l v a r i a t i o n 3 9 ' S e x u a l v a r i a t i o n 4 0 A g e v a r i a t i o n 4 3 V a r i a t i o n i n n u m b e r o f t a i l v e r t e b r a e 4 7 V a r i a t i o n b e t w e e n s p e c i e s 4 8 D I S C U S S I O N T a x o n o m i c p o s i t i o n o f t h e P o i n t G r e y p o p u l a t i o n 52 P a g e S U M M A R Y 59 L I T E R A T U R E C I T E D 6 2 A P B E M D T X I . S t a t i s t i c a l t a b l e s f o r q u a n t i t a t i v e v a r i a t i o n . A P P E N D I X I I . - F r e q u e n c y d i s t r i b u t i o n h i s t o g r a m s f o r q u a n t -i t a t i v e v a r i a t i o n . VARIATION IN AN ISOLATED POPULATION  OF SHREWS OF THE VAGRANS-OBSCURUS GROUP. INTRODUCTION Although shrews are often some of the commonest small mammals- occurring wherever there i s s u f f i c i e n t vegetation to provide cover f o * them and enough invertebrates as t h e i r food, much les s i s known of t h e i r habits, breeding behaviour and population phenomena, than of t h e i r associates such as Microtus and Peromysdus. Part of the reason f o r t h i s lack of knowledge con-cerning shrews i s the d i f f i c u l t y of l i v e - t r a p p i n g them and keeping them i n c a p t i v i t y . Moreover, since they have not been considered economically important, what few investigations have been car r i e d out on them, have been from the standpoint of basic research only. The biology of reproduction i n Sorex araneus, a European species, has been thoroughly investigated by Brambell ( 1955 ) i n a study based on dead animals. He demon* strated the d e t a i l s of the oestrus cycle i n the female and the seasonal changes i n the reproductive organs of the male. IH a l a t e r paper Brambell and H a l l ( 193& ) published the r e s u l t s of a s i m i l a r study on Sorex Mlnutus. No study of this type has yet teen car r i e d out on any American species of Sorex. Hamilton ( 1940 ) published a paper concerning the biology of Sorex fumeus i n New York state. He discussed molt, associates, food habits, reproductive biology, population behaviour, pred&tors and parasites, and set the basic pattern f o r further work on the genus i n North America. An excellent survey of breeding behaviour and the biology of reproduction i n BTarina a related genus, was: presented by Pearson ( 1944 ) • His study was based on experiments with and observations on mole shrews; i n c a p t i v i t y , and i s the only detailed study on American Sorici&ae* Later ( 1945 ) Pearson published a second paper on BTarina dealing with longevity and c e r t a i n population phenomena based on a l i v e ^ t r a p p i n g study. It was with the aim of further c l a r i f y i n g the biology of the genus Sorex, p a r t i c u l a r l y with respect to reproduction and population phenomena, that the present study was under*? taken at Point Grey, Vancouver, B r i t i s h Columbia, where two species off shrews, Sorex vagrans and Sorex obscurus were known to occur ( Cowan, 1930 ) I t soon became apparent that the two species could not r e a d i l y be d i f f e r e n t i a t e d from one another, and that the primary problem was therefore taxonomic. With t h i s end i n view an analysis of v a r i a t i o n i n the Sorex population of Point Grey was carried out. - 3 -i ACKNOWLEDGEMEKTS I wish to express my sincere gratitude to Dr. I. McT. Cowan, under whose d i r e c t i o n t h i s study was un-dertaken, f o r the sound advice and encouragement he has given me throughout the course of the study, and to Professor W.A. Clemens, Head of the department of Zoology, f o r the constant i n t e r e s t he has shown. I am indebted to Dr, P.A. Larkin f o r his advice on s t a t i s t i c a l problems, and to my fellow-students p a r t i c u l a r l y Miss M.H. Thorn, f o r t h e i r i n t e r e s t and assistance. I wish also to thank the University of B r i t i s h Columbia which provided funds under a research grant, with* out which work during the summers of 1950 and 1951 would have been impossible. -4-METHODS. Of 1296 small mammals taken i n west Point Grey from October 1949 to May 1950, 670 or 52.6% were long-tailed shrews belonging to the subgenus Sorex. Of these 658 were obtained i n V i c t o r snap-traps, six were found dead i n l i v e traps, three died i n ca p t i v i t y , and three were found dead i n the f i e l d . A standard trapping technique was followed through-out the course of the study. Traps were spaced about three yards apart i n l i n e s 50 to 100 yards long. Each trap was placed in the ": most l i k e l y spot " within a one-foot radius of the empirically selected station. " Most l i k e l y spots " included tunnel entrances, the bases of stumps, or ©alien logs. Traps were v i s i t e d at least once a day and were rebaited when necessary. Some l i n e s were run three or four times a day to determine diurnal a c t i v i t y patterns. The traps were usually baited with walnut pieces. Other ba i t s such as cheese, peanut butter with r o l l e d oats, and cheese with r o l l e d oats were t r i e d out but i t was found that these baits did not stay on the traps as long as walnuts and were therefore l e s s e f f e c t -ive. The trap-lines were for the most part set i n wooded or brushy areas, although an attempt was made to trap a l l habitat types. Several very successful l i n e s were placed in beach debris just above the high tide l i n e . Two l i n e s were set i n undisturbed grassy meadow. Trapping was carried out i n October and November 1949, from February to August 1950, and from January to May, 1951. A l l animals were removed from traps and immediately wrapped i n paper or placed i n small paper bags. In the lab-oratory most of the shrews were immediately examined for ectoparasites, which were transferred to 70% alcohol. Standard body measurements ( t o t a l length, t a i l length, and hind foot ) and weights were recorded for a l l species, and the condition of the reproductive and secondary sexual organs was noted. The length of the testes was measured i n a l l males, and the complete reproductive tract of a l l adult and some juvenile females, was preserved i n Bouin*s f i x a t i v e . Skins of most shrews were saved, an i n c i s i o n being made on the underside from the mouth to the base of the t a i l , and the skin stretched f l a t on cardboard to dry. A few were made up as museum specimens. After skinning^the t a i l s of shrews trapped during the spring of 1951 were removed at the base of the sacrum, and a count of the number of t a i l vertebrae was made. Many of the shrews were examined for in t e r n a l parasites, special attention being given to the i n t e s t i n a l tract and associated organs, parasites found were fixed i n hot alcohol or hot Bouin*s f i x a t i v e and preserved i n 70% alcohol. An attempt was made to i d e n t i f y the stomach contents of shrews, but only the most heavily c h i t i n i z e d parts of In-vertebrates such as leg fragments, antennae and the e ^ t J a ^ - 6 -of beetles were identifiable. The practice was soon dis-continued as it was felt that any analysis of food habits made on this basis would be biased, since softer-bodied animals and possibly plant material could not be identified. Skulls of a l l shrews were removed and cleaned. Six standard measurements- condylobasal length, cranial breadth, interorbital breadth, maxillary breadth, maxillary tooth row length and palatal length - were made on the skull with vernier calipers reading to 0 . 1 mm. A technique for aging shrews on the basis of tooth wear was developed. The lower jaws were removed from the skulls, cleaned in xylol and mounted, with the inside surface of the jaw up, in balsam on standard microscope slides, With the jaws mounted in this fashion the line at the base of the enamel of the teeth was sharply defined. Measurements were made of the height of the protoconid of the f irst lower molar, and of the length of the same tooth at its base, using an occular micrometer in a 5x occular with a 2/3 inch ( lOx ) objective. The animals were divided into four broad classes for the purpose of in i t ia l statistical treatment - male adults, female adults, male juveniles, and female juveniles. Animals were classed as adults when taken any time after the f irst o? January of the year following the one in which they were born. This corresponds fairly closely to the onset of sexual maturity. E a c h o f t h e s e g r o u p s w a s t r e a t e d s e p a r a t e l y i n a n a t t e m p t t o s e p a r a t e S . o b s c u r u s f r o m S . v a g r a n s . A b s o l u t e s e p a r a t i o n o f t h e t w o s p e c i e s w a s f o u n d t o b e i m p o s s i b l e o n t h e b a s i s o f s t a n d a r d m e a s u r e m e n t s o r s i m p l e r a t i o s o f t h e m . T h e t w o c h a r a c t e r s s h o w i n g g r e a t e s t d i v e r g e n c e w e r e t a i l l e n g t h a n d l e n g t h o f t h e m a x i l l a r y t o o t h r o w . A r b i t r a r y s e p a r a t i o n o n t h e b a s i s o f t h e s e t w o c r i t e r i a t a k e n i n c o n j u n c t i o n w i t h e a c h o t h e r r e -s u l t e d i n s p e c i f i c c l a s s i f i c a t i o n o f 95 p e r c e n t o f t h e m a t e r i a l . T h e d a t a M&S t h e n a n a l y s e d s t a t i s t i c a l l y t o d e t e r m i n e t h e a m o u n t o f s e x u a l , a g e a n d s e a s o n a l v a r i a t i o n i n s i z e . S t r e t c h e d s k i n s w e r e e x a m i n e d e x t e r n a l l y f o r m o l t a n d p e l a g e c h a r a c t e r i s t i c s . I t w a s f o u n d t h a t m o l t p a t t e r n c o u l d b e d e t e r m i n e d m o r e a c c u r a t e l y o n t h e b a s i s o f d a r k p i g m e n t a t i o n o c c u r r i n g o n t h e i n n e r s u r f a c e o f t h e s k i n a s t h e n e w f u r g r o w s i n t h a n b y e x a m i n a t i o n o f t h e f u r r e d s i d e o f t h e s k i n . T h e s k i n s s h o w i n g n o m o l t w e r e d i v i d e d i n t o t h r e e p e l a g e g r o u p s -s u m m e r j u v e n i l e , w i n t e r , a n d s u m m e r a d u l t . I n e a c h g r o u p t h e s k i n s w e r e a r r a n g e d , i n s e r i e s f r o m t h o s e m o s t c l o s e l y r e s e m b l -i n g S o r e x v a g r a n s t h r o u g h t o t h o s e m o s t l i k e S . o b s c u r u s . A s w i t h m e a s u r e m e n t s t h e r e w a s n o c l e a r c u t d i s t i n c t i o n , b e t w e e n t h e t w o s p e c i e s . D e s c r i p t i o n s o f s p e c i e s a r e b a s e d o n t h e a r b i t r a r y s e p a r a t i o n o u t l i n e d a b o v e . C o l o u r d e s c r i p t i o n s w e r e m a d e o n t h e b a s i s o f K i d g w a y ' s C o l o u r s t a n d a r d s ( 1912 ) . N o t e w a s m a d e o f a n y p e l a g e a b n o r m a l i t i e s o r p o s s i b l e m u t a t i o n s . A n a t t e m p t w a s m a d e t o c a p t u r e l i v e s h r e w s f o r c l o s e r -8-s t u d y i n t h e l a b o r a t o r y . B o t h b u c k e t - t y p e a n d t u n n e l l i v e -t r a p s w e r e - u s e d , n e i t h e r t y p e b e i n g v e r y s u c c e s s f u l . T h e b u c k e t - t r a p s t e n d e d t o f i l l w i t h w a t e r i n w h i c h t h e a n i m a l s d r o w n e d , a n d t h e t u n n e l - t r a p s o f t e n f a i l e d t o h o l d t h e s h r e w s . T r a p s w e r e v i s i t e d a s o f t e n a s p o s s i b l e , a t l e a s t s e v e r a l t i m e s a d a y . I n s p i t e o f t h i s , f i v e o f t h e e i g h t a n i m a l s t a k e n i n l i v e t r a p s w e r e d e a d w h e n f o u n d . T h e t h r e e a n i m a l s o b t a i n e d a l i v e w e r e p l a c e d i n a c o o l , s o m e w h a t d a r k e n e d r o o m i n g l a s s a q u a r i a l i n e d w i t h s l i g h t l y m o i s t e n e d s a w d u s t . T h e y w e r e p r o v i d e d w i t h n e s t - b o x e s l i n e d w i t h c o t t o n w o o l a n d f e d o n d o g m e a l m o i s t e n e d t o a p a s t e w i t h w a t e r , s u p p l e m e n t e d w i t h m i l k , r a w l i v e r , a n d t h e c a r c a s s e s o f m i c e a n d s h r e w s . I n s p i t e o f t h i s n o n e s u r -v i v e d m o r e t h a n t e n d a y s . -9-R E S U L T S . H a b i t a t s a n d A s s o c i a t e s . A n a t t e m p t w a s m a d e t o t r a p a l l h a b i t a t s a v a i l a b l e t o s h r e w s o n o r c l o s e t o t h e u n i v e r s i t y c a m p u s . T h e r e i s l i t t l e v a r i a t i o n i n h a b i t a t , a l m o s t a l l t h e a r e a b e i n g c o v e r e d w i t h s e c o n d g r o w t h m i x e d c o n i f e r o u s - d e c i d u o u s f o r e s t e x c e p t t h a t p a r t o c c u -p i e d b y b u i l d i n g s o r u n d e r c u l t i v a t i o n o r p a s t u r e . S m a l l a r e a s o f u n d i s t u r b e d m e a d o w a l o n g f a r m r o a d s , w h e r e t h e g r a s s e s a n d o t h e r v e g e t a t i o n h a v e b e e n a l l o w e d t o f o r m a d e n s e m a t o f c o v e r c o n s t i t u t e d a s e c o n d t y p e o f h a b i t a t . B e a c h d e b r i s a b o v e t h e h i g h t i d e l i n e p r o v i d e d a t h i r d d i s t i n c t h a b i t a t t y p e . H e r e l a r g e s t u m p s , l o g s a n d b o u l d e r s a r e i n t e r s p e r s e d w i t h a d e n s e g r o u n d c o v e r o f t w i g s a n d d e a d l e a v e s , a n d b a c k e d b y a s t e e p w e l l - w o o d e d h i l l s i d e . S e v e r a l s p r i n g s e m e r g e f r o m t h e b a s e o f t h e h i l l p r o -v i d i n g m o i s t g r o u n d a n d a f e w s m a l l p o o l s . T h e w o o d e d h a b i t a t s w e r e d i v i d e d i n t o t w o a r e a s a b o u t a m i l e a p a r t . T h e f i r s t ( d e s i g n a t e d W o o d e d I ) i s n e a r e r t o t h e m a i n p a r t o f t h e c a m p u s . I t i s r e l a t i v e l y o p e n , a n d i s c u t b y f o o t p a t h s a n d d i t c h e s b o r d e r e d b y s h r u b b y g r o w t h a n d p a t c h e s o f g r a s s . T r a p - l i n e s w e r e s e t a l o n g t h e p a t h s a n d d i t c h e s . T h e s e c o n d r e g i o n ( W o o d e d I I ) w a s a b o u t a m i l e a w a y i n l e s s d i s t u r b e d f o r e s t . T h e a r e a s t r a p p e d w e r e p r e d o m i n a n t l y c o n i f e r -o u s , a n d t h e c a n o p y w a s g e n e r a l l y d e n s e r t h a n i n W o o d e d I . T h e s h r u b a n d h e r b a c e o u s c o v e r w a s c o r r e s p o n d i n g l y l e s s d e n s e . S h r e w s w e r e t r a p p e d i n a l l h a b i t a t s . ( - 1 0 -S e v e n o t h e r s p e c i e s o f s m a l l m a m m a l s w e r e t a k e n i n t h e t r a p l i n e s i n a d d i t i o n t o S o r e x v a g r a n s a n d S o r e x o b s c u r u s ; -S c a p a n u s o r a r i u s s c h e f f e r i J a c k s o n . S c h e f f e r ' s M o l e N e u r o t r i c h u s g i b s i i g i b b s i i ( B a i r d ) . S h r e w M o l e S o r e x b e n d i r i i b e n d i r i i ( M e r r i a m ) . M a r s h S h r e w P e r o m y s c u s m a n i c u l a t u s a u s t e r u s ( B a i r d ) , ? v r h i t e - f o o t e d M o u s e M i c r o t u s t o w n s e n d i i ( B a c h m a n ) . T o w n s e n d ' s v o l e M i c . r o t u s s e r p e n s M e r r i a m . C r e e p i n g V o l e Z a p u s t r i n o t a t u s t r i n o t a t u s R h o a d s . J u m p i n g M o u s e . T h e a b u n d a n c e o f t h e s e s p e c i e s a s m e a s u r e d b y t o t a l c a t c h p e r h u n d r e d t r a p - n i g h t s i s g i v e n i n T a b l e 1. T h i s m e t h o d o f d e t e r m i n i n g a b u n d a n c e i s n o t j ^ p ^ a c c u r a t e , b u t s o m e i d e a o f t h e r e l a t i v e a b u n d a n c e o f e a c h s p e c i e s i n e a c h h a b i t a t m a y b e d e r i v e d f r o m i t . T a b l e 2. s h o w s t h e p e r c e n t a g e c o m p o s i t i o n o f t h e t o t a l c a t c h i n e a c h t r a p l i n e . S c h e f f e r ' s m o l e w a s . t a k e n o n l y o n c e d u r i n g t h e e n t i r e t r a p p i n g p e r i o d i n s p i t e o f a b u n d a n t e v i d e n c e o f i t s p r e s e n c e i n t h e f o r m o f m o u n d s a n d t u n n e l s . I t s f o s s o r i a l h a b i t s a n d i n -d i f f e r e n c e t o b a i t r e n d e r i t u n a v a i l a b l e i n m o s t c a s e s . W o r k i n g s o f t h i s s p e c i e s w e r e s e e n i n a l l h a b i t a t t j r p e s e x c e p t W o o d e d I I . T h e s h r e w m o l e w a s f o u n d i n s m a l l n u m b e r s i n a l l h a b i t a t t y p e s e x c e p t m e a d o w . I t t o o m a y b e m o r e a b u n d a n t t h a n i s i n d i c -a t e d b y t h e c a t c h , a l t h o u g h i t i s l e s s f o s s o r i a l i n h a b i t ' t h a n S c h e f f e r ' s M o l e a n d a p p e a r s t o b e a t t r a c t e d b y w a l n u t b a i t . B o t h t h i s a n d t h e p r e v i o u s s p e c i e s a l m o s t c e r t a i n l y c o m p e t e w i t h S o r e x T A B L E 1. A b u n d a n c e o f S o r e x a n d a s s o c i a t e s m a l l m a m m a l s i n d i f f e r e n t h a b i t a t t y p e s . H a b i t a t N u m b e r o f t r a p -n i g h t s C a t c h p e r 100 t r a p n i g h t s . - S o r e x S o r e x * T o t a l S c a p a n u s o b s c u r u s v a e r a n s S o r e x N e u r o -t r i c h u s S o r e x P e r o m -1 b e n d i r i i y s e u s M i c r o t u s M i c r o t u s t o w n s e n d i i o r e g a n u s Z a p u s T o t a l a l l s p e c i e s . W o o d e d I 5638 0.87 4 . 2 4 5.39 0 0.80 .005 3.19 0 0.16 0 . 4 8 1 0 . 0 4 Y J o o d e d I I 725 2.34 1.66 4.00 0 0 . 1 4 0 3.72 0 0 0 7 . 8 6 B e a c h 3947 1.37 4.56 6.36 0.84 0.84 0.25 3 . 7 2 0 0.03 0 . 0 3 11.23 M e a d o w 250 0 7.20 7.20 0 0 0 2 . 8 0 3.20 0 0 13.20 T o t a l a l l 10560 h a b i t a t s 1.13 4.08 5 . 7 0 0.01 0.75 0 . 0 1 3 . 4 2 0 . 0 9 0.10 0.27 1 0 . 4 2 * N o t e : T o t a l S o r e x i n c l u d e s t h e s e a n i m a I s n o t s p e c i f i c a l l y • i d e n t i f i e d a s S . v a g r a n s o r S . o b s c u r u s . T A B L E 2. P e r c e n t a g e c a t c h o f S o r e x a n d a s s o c i a t e s i n d i f f e r e n t h a b i t a t t y p e s . H a b i t a t N u m b e r o f a n i m a l s P e r c e n t a g e o f t o t a l c a t c h . S o r e x S o r e x * T o t a l S c a n a n u s : o b s c u r u s v a g r a n s S o r e x N e u r o -t r i c h u s S o r e x b e n d i r i i P e r o m - ] y s c u s l i c r o t u s t o w n s e n d i * M i c r o t u s o r e g a n u s Z a p u s W o o d e d I 566 8.5 4 2 . 2 54.7 0 8 . 0 0 . 2 31.8 0 1.6 4 . 8 W o o d e d I I 57 ' 2 9 . 8 21.1 5-0.9 0 1.8 0 4 7 . 4 0 0 0 B e a c h 4 4 4 12.2 4 0 . 3 56.5 0.2 7 . 4 2.3 3 3 . 1 0 0 . 2 0.2 M e a d o w 33 0 54.5 54.5 0 0 0 21.2 2 4 . 2 0 0 T o t a l a l l 1100 1 0 . 9 39.2 5 4 . 7 0.1 7.2 1.0 32.8 0.7 0 . 9 2.5 h a b i t a t s * N o t e : T o t a l S o r e x i n c l u d e s t h o s e a n i m a l s n o t s p e c i f i c a l l y i d e n t i f i e d a s S . v a g r a n s o r S . o b s c u r u s . - l i -f e - r f o o d , t o s o m e e x t e n t a t l e a s t . M a r s h s h r e w s w e r e c o n f i n e d t o t h e w e t a r e a s . N i n e o f t h e 10 i n d i v i d u a l s t a k e n w e r e f r o m t h e l i n e s i n b e a c h d e b r i s w h e r e s p r i n g s k e e p t h e g r o u n d m o i s t a n d t h e r e a r e s o m e s m a l l p o o l s . O n e m a r s h s h r e w w a s t a k e n i n W o o d e d I o n t h e e d g e o f a d i t c h , w h i c h h a d r u n n i n g w a t e r o r a t l e a s t s t a g n a n t p o o l s e x -c e p t f o r a f e w w e e k s d u r i n g t h e d r i e s t p a r t o f t h e s u m m e r . T h i s s p e c i e s p r o b a b l y f o r m s a c o n s t a n t , t h o u g h s m a l l p a r t o f t h e s m a l l m a m m a l p o p u l a t i o n o f P o i n t G r e y , o c c u r r i n g w h e r e v e r t h e r e i s p e r m a n e n t m o i s t u r e . ' T h e w h i t e - f o o t e d m o u s e w a s s e c o n d o n l y t o S o r e x i n a b u n d -a n c e a n d w a s c o m m o n i n a l l h a b i t a t t y p e s , a l t h o u g h l e s s a b u n -d a n t i n t h e m e a d o w t h a n i n o t h e r a r e a s . I t c o n s t i t u t e s 22 t o 47 p e r c e n t o f t h e s m a l l m a m m a l p o p u l a t i o n . T h e r e i s p r o b a b l y l i t t l e o r n o c o m p e t i t i o n b e t w e e n t h i s s p e c i e s a n d s h r e w s s i n c e f o o d h a b i t s a r e s o d i f f e r e n t . T h e T o w n s e n d v o l e w a s c o n f i n e d t o t h e m e a d o w h a b i t a t . H e r e i t s n u m b e r s w e r e h i g h , b u t S o r e x w a s s t i l l m o r e a b u n d a n t . A l l t r a p s i n t h e m e a d o w w e r e s e t i n f r e s h M i c r o t u s r u n w a y s . T h e s h r e w s a p p a r e n t l y u t i l i z e t h e s e r u n w a y s t o a c o n s i d e r a b l e e x t e n t . T h e c r e e p i n g v o l e w a s t a k e n i n a l l h a b i t a t s e x c e p t t h e m e a d o w , w h e r e i t i s r e p l a c e d b y i t s l a r g e r r e l a t i v e . I t d o e s n o t a p p e a r i n t h e t a b l e f o r W o o d e d I I b u t w a s t a k e n i n a t r a p -12-.plot i n the same region. Jumping mice may have been present i n a l l habitats. It..was not taken i n meadow, but trapping of this area was carr i e d out early i n the spring while, the jumping mice were s t i l l i n hibernation. Jumping mice were taken i n the trap plot in Wooded II, although they were absent from standard trap l i n e s on which the tables are based. Since these animals hibernate except during the summer months, they are absent from the catch throughout the rest of the year, and therefore estimates of r e l a t i v e and absol-ute abundance are c e r t a i n l y low. The smaller shrews ( Sorex vagrans and S. obscurus ) were the most abundant mammals, constituting about 55 per cent of the t o t a l small mammal population i n a l l habitat types. Their absolute abundance varies considerably with the season ( see Fi g . I ), but r e l a t i v e l y l i t t l e with habitat type. They are most abundant i n the meadow and least abundant i n Wooded I I . When Sorex vagrans i s separated from Sorex pbscurus on the ar b i t r a r y basis outlined i n the section on s p e c i f i c determinat-ion, some habitat s e l e c t i o n i s apparent. S. vagrans is the more abundant of the two species i n a l l habitat types except Wooded I I , and i s the only species of shrew taken i n the meadow. I t i s three to four times as abundant as S. obscurus on the average. How-ever" i n Wooded II S. obscurus outnumbers S. vagrans, though not by much. This difference i n abundance possibly indicates a preference by S, vagrans for open or p a r t i a l l y open areas, and -13-by S. obscurus for more heavily forested regions, e s p e c i a l l y where conifers are predominant. Seasonal Variation i n Numbers . Since a l l adult shrews die at the end of t h e i r f i r s t breeding season, there is a 100 percent annual population turn-over. The juveniles produced during one breeding season are adults the following summer, and the l i f e span of the oldest animals i s never much more than a year. Adults and juveniles are r e a d i l y distinguished. Thus i t is possible to follow through each annual population from i t s beginning during one breeding season u n t i l i t is exterminated at the end of the following breeding season. F i g . I shows the abundance of shrews f o r monthly periods from October 1949 to A p r i l 1951. Each annual population i s treated separately. The population increases rapidly a f t e r the young f i r s t s t a r t running i n early A p r i l and reaches a peak in June. Mortality i s apparently high during the late summer i n the young shrews, and i s much lower during the winter months when jjhe population remains at a f a i r l y constant l e v e l . Mor-t a l i t y of the adults i s not marked u n t i l July, when the catch f a l l s o f f r a p i d l y . Only three adults.were taken after the end of August - a male and a female in October, 194-9 and a very old male i n January 1951. F i g . I. Seasonal v a r i a t i o n i n numbers of Sorex. Note: No trapping i n December, 1949; January, 1950; September to December, 1950. -14-In spite of rather crude methods of estimating abund-ance, further aspects of population phenomena could have been evaluated,.but were considered out of l i n e i n the present study. This short analysis has been included merely to give a general picture of the v a r i a t i o n in numbers and turnover present i n the population under consideration. Reproduction Sex Ratios. Of 2 6 l adult shrews taken from October 1949 to A p r i l 1951» 171 or 66 percent were males. This male predominance i s highly s i g n i f i c a n t { P * . 0 1 ). Taken by monthly periods, only i n May and June 1950 i s male predominance s i g n i f i c a n t , although the same trend i s evident i n a l l months i n which adults were obtained. ( See Table 3 ). The sex r a t i o i n 397 juveniles obtained over the same period was 203 males to 197 females. T h i s , i s not s i g n i f i c a n t l y d i f f e r e n t from the expected 50 percent sex r a t i o . The unbalanced r a t i o i n adults may be explained i n two ways. Either the males have a greater longevity, or they show a greater tendency to wander than do females during the breeding season, or both, factors may be operating. There i s l i t t l e d i r e c t evidence that males are longer l i v e d than females, aside from that of sex r a t i o s . However i t does seem possible TABLE 3 . Sex Ratios of Adults and Juveniles f o r Monthly Periods. Adults Juveniles Month Total Number Percent Males To t a l Numb er Percen Males October 1949 2 50 31 58 November 0 18 45 February 1930 16 63 0 __ March 16 69 0 — A p r i l 28 54 2 0 May 39 69 85 54 June 55 73 108 50 July 16 '63 77 52 August 14 57 71 51 January 1931 7 71 0 — February 18 55 0 --March 21 67 0 A p r i l 20 60 2 50 Total 261 66 397 51 - 1 5 -that the s t r a i n imposed on the female during the reproductive period would he higher than that imposed on the male. On the other hand there i s good evidence that shrews show a higher tendency to wander than do most other small mammals. The catch of shrews i n a permanent trap l i n e does not drop s i g n i f i c a n t l y a f t e r the f i r s t three days, and shrews are s t i l l taken regular-l y i n the same trap l i n e after a period of two months. Adult females might he expected to be r e s t r i c t e d to a more li m i t e d ragge during most of the summer when they are nursing young, and might therefore be taken less frequently in established trap l i n e s . I f the sex r a t i o s of the shrews caught during the f i r s t three days of trapping i n l i n e s established during A p r i l , May and June are compared, they are found not to d i f f e r s i g n i f -i c a n t l y from the expected 50 per cent sex r a t i o . Of 25 adults taken at this time 13 were females. .Reproduction i n the Male. Male shrews do not mature during the breeding season in which they are born. Smears to detect presence or absence of sperm were not made, but the difference i n testes size be-tween young and adults was marked. Hamilton { 1940 ) states that i n Sorex fumeus " those individuals which are not fecund have small testes, seldom exceeding 2 mm. . . . . Sexually mature individuals possessed testes measuring 4 x 6 mm. to 4 .5 x 8 mm. ,r Sorex fumeus i s s l i g h t l y larger than S. obscurus, adult males weighing 8 to 11 grams, i n comparison with 5 to 8 grams i n the l a t t e r species. The testes of immature shrews collected at Point Grey from the end of A p r i l to November were only 1 to 2 mm. in length, and the other reproductive organs were not enlarged. The dermal flank glands could be detected in juveniles as somewhat glandular areas on the inside of the skin, but were not nearly so prominent as i n adults. The fur i n the region of the flank glands i n juveniles i s not d i f f e r -entiated as i t i s in adults. Healthy adult shrews trapped during the breeding season and presumably sexually mature had testes measuring from 5 to 8 mm. in length. Several adults taken i n May and June at the height of the breeding season were heavily infested with nematodes encysted in the subcutaneous tissue. ( One shrew had 284 of these small roundworms encysted in the conn-ective tissue throughout the entire body ). In these animals the testes were somewhat reduced i n si z e , measuring 4 to 5 mm. i n length,' and the body weight was lower than average, 5.5 to 6.6 gm. as compared with an average adult weight of 7.04 gm. Whether or not t h i s high degree of parasitism affected fecund-i t y i s not known, but the small sige of the testes may indicate that i t did. In f u l l y mature males the dermal flank glands are very prominent. According to Johnsen's account ( 1914 ) the gland i n Sorex araneus consists of a central oval area in which there are numerous sweat glands, and a peripheral r i n g of en-larged sebaceous glands. In f r e s h specimens of adult male -17-Sorex obscurus and S. vagrans the glands appear at highly vas-cularized oval patches of thickened skjfcn. The hairs growing i n t h i s region are d i f f e r e n t i a t e d from those on the rest of the body, being short, s t i f f and b r i s t l e - l i k e . Johnsen attributed a sexual function to these glands, stating that the secretion produced by them provides a means of a t t r a c t i o n between the sexes at the time of mating. The glands are present i n adult females, but are not as highly developed as i n males. According to Johnsen ( 1914 ) only sweat glands take part i n th e i r formation i n females. The region i s not highly vascularized and the fur i s not d i f f -erentiated from that on the rest of the body. Sexual maturity i n males i s attained i n February. An increase in body weight and development of the flank glands are correlated with the onset of sexual maturity. A male, taken an January 22, 1951, had testes measuring 3 .5 mm. i n length. The accessory organs ( vas deferens, penis, prostate and Cowper's glands) [ were somewhat enlarged but had not attained the s i z e found i n f u l l y mature males. The central part of the flank gland was pigmented, but the hair covering i t had not become d i f f e r -entiated from that on the rest of the body. Animals taken i n late January and early February, in which the central part of the gland i s well developed, but i n which f u r i s being molted i n a peripheral r i n g around the gland, have testes measuring 4 .5 to 5 mm. in length - somewhat smaller than i n f u l l y mature - 1 8 -i n d i v i d u a l s . A m o r e c o m p l e t e d e s c r i p t i o n o f m o l t i n t h e r e g i o n o f t h e s i d e g l a n d i s g i v e n o n P . 3 2 . A f t e r F e b r u a r y 2 4 a l l a n i m a l s t a k e n h a d c o m p l e t e d t h e m o l t o f t h e s i d e g l a n d s a n d h a d t e s t e s m e a s u r i n g 5 m m . o r m o r e , e x c e p t f o r t h e h e a v i l y p a r a s i t i z e d i n d i v i d u a l s a l r e a d y d i s c u s s e d . T h e c o r r e l a t i o n b e t w e e n b o d y w e i g h t a n d t h e o n s e t o f s e x u a l m a t u r i t y i s i n d i c a t e d i n F i g . I I . - J u v e n i l e m a l e s i n O c t o b e r a n d N o v e m b e r a v e r a g e d 5.1 a n d 4 . 6 g m . r e s p e c t i v e l y ; i n J a n u a r y a n d F e b r u a r y t h i s h a d i n c r e a s e d t o 6.1 a n d 6.3 g m . I n c r e a s e i n w e i g h t c o n t i n u e d t o a p e a k o f 7.2 g m . i n A p r i l , a f t e r w h i c h t h e a v e r a g e w e i g h t i n a d u l t s g r a d u a l l y f e l l o f f t o 6.3 g m . i n A u g u s t . P r a c t i c a l l y a l l a d u l t s a r e d e a d b y t h e e n d o f A u g u s t . O n e a d u l t m a l e t a k e n i n O c t o b e r 1 9 4 9 w a s a p p a r e n t l y s t i l l s e x -u a l l y m a t u r e , w i t h t e s t e s m e a s u r i n g 6 m m . A v e r y o l d m a l e , t a k e n o n J a n u a r y 23, 1951 w a s a l s o a p p a r e n t l y f e c u n d . T h e r e i s n o i n -d i c a t i o n t h a t t h e r e p r o d u c t i v e o r g a n s o f t h e f e w r e m a i n i n g a d u l t m a l e s r e g r e s s d u r i n g t h e w i n t e r , e i t h e r i n t h e p r e s e n t s t u d y , o r i n s t u d i e s c a r r i e d o u t b y o t h e r w o r k e r s . B r a m b e l l ( 1935 ) r e p o r t s a f e c u n d a d u l t m a l e S o r e x a r a n e u s t a k e n o n N o v e m b e r 12. W h i l e t h e e v i d e n c e i n s u p p o r t o f t h i s t h e o r y i s b a s e d o n v e r y f e w s p e c i m e n s , t h e r e i s n o c o n t r a d i c t o r y e v i d e n c e . I f i t i s t r u e , s h r e w s a r e m o s t u n u s u a l a m o n g o t h e r m a m m a l s i n t h a t t h e l i f e c y c l e i s k e y e d , n o t t o a n n u a l s e a s o n s b u t t o a s i n g l e p e r i o d o f r e p r o d u c t i v e a c t i v i t y w h i c h i s t e r m i n a t e d o n l y b y d e a t h . Fig. II. Seasonal variation in weight of males - 1 9 -T h e d u r a t i o n o f t h e b r e e d i n g s e a s o n i n t h e m a l e , a s i n d i c a t e d b y m a x i m a l t e s t e s s i z e , w a s f r o m t h e e n d o f F e b r u a r y u n t i l t h e d e a t h o f m o s t o f t h e - a d u l t s i n A u g u s t . T h o s e f e w a n i m a l s w h i c h w e r e n o t d e a d ' b y t h e e n d o f A u g u s t r e m a i n e d i n b r e e d i n g c o n d i t i o n . T h e b r e e d i n g s e a s o n o f S . . o b s c u r u s a n d S . v a g r a n s s t a r t s s o m e w h a t e a r l i e r t h a n i n o t h e r s p e c i e s o f s h r e w s . B r a m b e l l ( 1 9 3 5 ) s t a t e s t h a t m a l e S . a r a n e u s d o n o t m a t u r e u n t i l M a r c h o r e a r l y A p r i l , a n d H a m i l t o n ( 1 9 4 1 ) g i v e s t h e s a m e m o n t h s f o r t h e b e g i n n i n g o f t h e b r e e d i n g s e a s o n i n A m a l e s , a s d o B r a m b e l l a n d H a l l ( 1 9 3 6 ) f o r S . m i n u t u s . * R e p r o d u c t i o n i n t h e F e m a l e . L i k e t h e m a l e s , t h e f e m a l e s d o n o t a t t a i n s e x u a l m a t u r i t y u n t i l t h e s p r i n g o f t h e y e a r f o l l o w i n g t h e o n e i n w h i c h t h e y a r e b o r n . T h e g e n i t a l t r a c t r e m a i n e d m i n u t e i n s i z e u n t i l l a t e F e b r u a r y o r e a r l y M a r c h , a n d t h e m a m m a r y g l a n d s w e r e u n d e r -d e v e l o p e d u n t i l s h o r t l y b e f o r e t h e b i r t h o f t h e f i r s t l i t t e r . T h i s i s i n a c c o r d w i t h t h e r e s u l t s o f m o s t o t h e r w o r k e r s i n t h e g e n u s . B r a m b e l l ( 1 9 3 5 ' ) s t a t e s t h a t ' * s o m e y o u n g a n i m a l s , p r e s u m a b l y b o r n e a r l i e r i n t h e s e a s o n , e x h i b i t t o w a r d i t s c l o s e p r e p u b e r t a l d e v e l o p m e n t o f t h e r e p r o d u c t i v e o r g a n s b u t t h e r e i s n o e v i d e n c e t h a t t h e y a t t a i n o e s t r u s ; . " A c c o r d i n g t o H a m i l t o n ( 1 9 4 0 ) i n y o u n g f e m a l e S o r e x f u m e u s t r t h e o v a r i e s m i c r o s c o p -i c a l l y s h o w n o i n d i c a t i o n o f s e x u a l a c t i v i t y . n O f S o r e x m i n -u t u s B r a m b e l l a n d H a l l ( 1 9 3 6 ) s t a t e t h a t " ' t h e r e w e r e n o i n d i c a t i o n s t h a t t h e y o u n g a n i m a l s o f e i t h e r s e x b e c o m e m a t u r e - 2 0 -i n the season i n which they are born. n The only exception to this know:., to the writer occurred in a population of Sorex  cinereus i n Algonquin Park, Ontario. Here six females, c l a s s i -f i e d as young of the year on the basis of tooth and pelage char-a c t e r i s t i c s , were found to be breeding. Of these animals, a l l taken during the month of July, three were pregnant, and three had recently given b i r t h to young and were l a c t a t i n g . There i s no reasonable explanation for t h i s discrepancy, except that the shrew population at the time was much higher than i n f i v e other years i n which i t was studied. No sign of reproductive a c t i v i t y was nested i n females u n t i l the middle of February, when some of the individuals collected were found to have swollen u t e r i . After the f i r s t of March no females were co l l e c t e d which did not show signs of breeding a c t i v i t y i n the form of swollen u t e r i , pregnancy or l a c t a t i o n . The f i r s t pregnant animals were taken on March 22, 1950 and A p r i l 1, 1951. These contained embryos measuring 2.5 and 4 .5 mm. respectively i n crown rump length. Since no mic-roscopic examination of the ovaries or uterus was made, some pregnancies in the ear l y stages were probably overlooked p r i o r to t h i s date. The f i r s t l i t t e r s were born early in A p r i l . Lactat-ing females which had recently given b i r t h to young were f i r s t taken on A p r i l 6, 1950 and A p r i l 2 3 , 1951. - 2 1 -A post-partum oestrus has been suggested"by Hamilton ( 1940 ) f o r Sorex fumeus and by Brambell ( 1935 ) for Sorex araneus, and has d e f i n i t e l y been shown by Pearson ( 1944 ) for Blari n a brevicauda. A s i m i l a r condition i s suggested for So rex  vagrans and Sorex obscurus at Point Grey, since several gravid females taken throughout the summer were l a c t a t i n g heavily. Females taken on A p r i l 25 and May 8, 1950 were lac t a t i n g heavily and contained small embryos, presumably a second l i t t e r . The f i r s t juvenile shrews were trapped on A p r i l 29, 1950 and A p r i l 2:8, 1951, four to f i v e weeks after the f i r s t pregnant shrews were taken. Brambell ( 1935 ) suggests that the gestation period i s 18 days or le s s , and that pregnancy i s not macroscopically evident for the f i r s t h a l f of t h i s per-iod. The length of time from b i r t h to weaning must be approx-imately the same as or shorter than the gestation period, unless one of the l i t t e r s i s s a c r i f i c e d . Thus a theoret i c a l period of :just over f i v e weeks from conception to weaning i s about the same as that found i n the Point Grey population, allowing an extra week to ten days for undetected e a r l y pregnancies, i . e . March 22 to A p r i l 29, 1950 and A p r i l 1 to A p r i l 28, 1951. Breeding i s continuous throughout the summer although some animals taken i n August apparently f a i l e d to mate, possibly because of the scarcity of males. These individuals were not l a c t a t i n g , the mammary glands being somewhat shrunken, and while -22-s o m e w e r e m a c r o s c o p i c a l l y p r e g n a n t , o t h e r s h a d s w o l l e n u t e r i b u t n o e v i d e n c e o f e m b r y o s . B r a m b e l l ( 1935 ) s t a t e s t h a t r e t r o g r e s s i o n o f t h e m a m m a r y g l a n d s a f t e r n u r s i n g h a s c e a s e d i s e x t r e m e l y r a p i d . I t i s p o s s i b l e t h a t t h e s e a n i m a l s h a d e i t h e r f a i l e d t o m a t e a t t h e p o s t - p a r t u m o e s t r u s , o r t h a t t h e y h a d l o s t t h e i r l i t t e r s a n d w e r e i n t h e e a r l y s t a g e s o f p r e g n a n c y w h i c h c o u l d n o t b e d e t e c t e d m a c r o s c o p i c a l l y . O n l y o n e a d u l t f e m a l e w a s t a k e n a f t e r t h e e n d o f A u g u s t . T h i s a n i m a l , w h i c h w a s p r e g n a n t " b u t n o t a c t i v e l y l a c -t a t i n g , w a s t a k e n o n O c t o b e r 9 , 1949. T h u s t h e a d u l t f e m a l e s , l i k e t h e m a l e s , a p p a r e n t l y a l l d i e i n t h e f a l l . T h i s a g a i n i s i n a c c o r d w i t h t h e f i n d i n g s o f o t h e r w o r k e r s i n t h e g e n u s . H a m i l t o n ( 1 9 4 0 ) f o u n d n o a d u l t f e m a l e s S o r e x f u m e u s a f t e r t h e e n d o f A u g u s t , a l t h o u g h h e r e p o r t s t w o i n s t a n c e s o f r e c e n t l y l a c t a t i n g f e m a l e s b e i n g t a k e n i n O c t o b e r . B r a m b e l l a n d H a l l ( 1936 ) t o o k n o a d u l t S o r e x m i n u t u s a f t e r t h e e n d o f A u g u s t , e x c e p t o n e f e m a l e i n O c t o b e r . A c c o r d i n g t o B r a m b e l l ( 1935 ) t h e a d u l t f e m a l e s o f S o r e x a r a n e u s a r e t a k e n n o t u n c o m m o n l y u n t i l e a r l y N o v e m b e r . A f t e r t h i s t i m e h e t o o k o n l y t w o -o n e i n F e b r u a r y a n d o n e i n M a r c h . B o t h o f t h e s e w e r e p a r o u s n o n - p r e g n a n t a n i m a l s w h i c h h a d n o t r e c e n t l y b e e n l a c t a t i n g . H e a s s u m e d t h a t t h e y w e r e i n w i n t e r a n o e s t r u s , b u t f a i l u r e t o b r e e d m a y a l s o h a v e b e e n d u e t o a b s e n c e o f f e c u n d m a l e s . A t P o i n t G r e y t h e b r e e d i n g s e a s o n i n f e m a l e s l a s t s f r o m e a r l y m a r c h u n t i l t h e a d u l t p o p u l a t i o n d i e s o u t d u r i n g -23-the summer or early f a l l . In spite of heavy trapping only 6 adult females were obtained i n July and six i n August. Prob-ably most of the adult population dies by midsummer. Thus a shrew that weaned her f i r s t l i t t e r at the end of A p r i l , i f succ-e s s f u l l y mated at each post-partum oestrus, would have raised f i v e l i t t e r s by the middle of July. If the female taken i n October had one l i t t e r every three weeks, i t could have raised a possible t o t a l of eight l i t t e r s . The average l i t t e r size based on embryo counts i n 23 pregnant shrews was 3*30, including resorbing embryos, and the range was 2 to 7 ( see i'ig. I l l ). Based on healthy embryos the average l i t t e r size was 5.14. This compares with an aver-age of 5«5 i n Sorex fumeus ( Hamilton, 1940 ), 6.45 i n Sorex  araneus ( Brambell, 1935 ) and 6.23 i n Sorex minutus ( Brambell and H a l l , 1936 ). These counts were a l l based on r e l a t i v e l y large samples ( 42 or more i n each case ). Jackson ( 1928 } gives 5.8 as the average l i t t e r size i n 8 Sorex vagrans and 5.4 i n 16 S. obscurus. Thus the average l i t t e r size of the Point Grey population i s considerably lower than i n most species of Sorex for which data are available including estimates based on other populations of S. vagrans and S. obscurus. Evidence that embryos were resorbing was found i n 5 out of 22, or 23 percent of healthy shrews ( see Table 4 ) . In four cases, one embryo of each l i t t e r was being resorbed. TABLE 4. L i t t e r size and resorption of embryos. Date No. of embryos Resorption i n l e f t horn i n right horn of uterus of uterus March 22, 1950 3 3 A p r i l 7 3 3 1 i n ri g h t horn 9 2. 3 20 2 4 25 4 3 25 3 3 1 i n l e f t horn May 6 2 3 8 2 2 18 3 3 19 3 3 June 8 2 3 9 4 3 21 3 3 11 i n l e f t horn 23 1 1 29 2 2 a l l ( see text ) July 6 2 2 1 i n l e f t horn Aug. 21 2 2 Oct. 9 4 3 2 i n ri g h t horn Apr. 1, 1951 3 3 ' 16 3 3 '" 18 2 3 May 5 2 3 July 24 2 2 -24-An adult female was captured, a l i v e on June 20, 1950. At t h i s time she was or had re c e n t l y "been l a c t a t i n g . The mammary glands were enlarged and the teats prominent. At her death nine days l a t e r she was found to have four embrgros, a l l of which were being resorbed. The mammary glands and teats were very much shrunken i n size at this time. Since considerable d i f f i c u l t y was ex-perienced i n keeping shrews a l i v e i n c a p t i v i t y , i t i s highly possible that the additional s t r a i n imposed by c a p t i v i t y was responsible for the loss of the embryos. Brambell ( 1936 ) reports three pregnancies i n which embryos were resorbing, or 6.2 percent i n a t o t a l of 49 pregnant females. This represented a loss by resorption of 7 embryos, or 2.1 percent i n a t o t a l of 327 embrpos. These figures are con-siderably lower than those f o r the Point Grey population. Re-sorbing embryos were found i n 23 percent of pregnant females, and represented a loss of 7.4f0 in a t o t a l of 122 embryos. Brambell ( 1935 ) has shown that the l i t t e r size of Sorex araneus decreases toward the end o f the breeding season. The same appears to be. true for the Sorex vagrans.- Sorex ob-scurus population of Point Grey. Average l i t t e r size decreases from a high of 6 .0 i n March to a low of 4.0 i n July and August ( See F i g . IT ). The average l i t t e r size based on counts of healthy embryos i s 5.14. I f each female l i v e d u n t i l the middle of July, and weaned a l i t t e r every three weeks, 9r 3 l i t t e r s i n a l l , the F i g , I I I . Frequency d i s t r i b u t i o n of embryo counts. MAR. APR. MAV JUNE JULY AUG. - 2 5 -reproductive pot e n t i a l of each adult female would he 2.6 young born during the breeding season. Pelage v a r i a t i o n and, molt. Shrews undergo two molts and are found i n three d i s t i n c t pelages from the time they leave the nest u n t i l they die the following summer. The juvenile summer pelage i s present when the animals f i r s t k a v e the nest and are caught i n traps. This i s maintained u n t i l October, when the winter pelage i s attained following a rapid molt. This winter pelage l a s t s u n t i l the following spring, when there i s a second molt, e a r l i e r i n females than i n males, and the adult summer pelage grows i n . In some males t h i s molt is absent or slow and i r r e g u l a r , and some i n -dividuals are found i n worn winter pelage well into the summer. There does not appear to be any regular f a l l molt i n the few surviving adults. The three adults taken after the end of Aug-ust - two i n October and one i n January - were s t i l l i n trorn summer pelage. Jackson ( 1928 ) states that " externally, shrews display l i t t l e v a r i a t i o n with age. As a rule young animals appear slenderer than adults and have their t a l i s a t r i f l e more hairy and slenderer. " This was not found to be the case i n the Point Grey population. Juveniles and adults i n summer can usually be separated on the basis of pelage char-a c t e r i s t i c s . Juveniles are browner i n colour than adults and -2.6-lack a pronounced darker dorsal s t r i p e . The feet and t a i l s of young animals are well-furred and there i s a d e f i n i t e p e n c i l of dark hairs on the end of the t a i l . In adults much or a l l of the hair on the t a i l and feet i s l o s t . In most adult males the t a i l i s naked; females tend to have sparse short hair on the t a i l . The prominent dark pencil of hairs on the t a i l t i p of juveniles i s always missing i n adults. Wo v a r i a t i o n i n pelage between sexes was noted, except for the difference i n hairiness of the t a i l i n adults already mentioned. If the two species of shrews reported to be present i n the Point Grey area are d i s t i n c t , they can not always be separated on the basis of pelage c h a r a c t e r i s t i c s . In a large series, a r b i t r a r i l y separated on the basis of body and s k u l l measurements, general differences can be detected. These d i f f -erences are most pronounced i n animals in winter pelage, and are somewhat less well marked i n summer adults. It i s usually im-possible to dis t i n g u i s h between the two species i n summer juv-enile pelage. There i s a certain amount of colour v a r i a t i o n between individuals of the same species i n the same pelage, and this v a r i a t i o n i s great enough to provide andoverlap i n pelage c h a r a c t e r i s t i c s between the two species. Summer Pelage i n Juveniles. In Sorex vagrans the upper parts are mummy brown to - 2 7 -b i s t e r , sometimes prout's brown, and occasionally nearly clove brown to fuscous. A dorsal s t r i p e i s usually absent * the colour of the back blending uniformly into scarcely paler sides and flanks. The underparts are from between smoke gray and drab gray to pale smoke gray. A l i g h t wash of vinaceous buff to avellaneous, more pronounced on the throat than on the b e l l y , i s present i n some in d i v i d u a l s . The t a i l i s well-furred, scarcely to d i s t i n c t l y bicolour. The colour difference i s more pronounced near the base but i n some individuals extends almost to the t i p . The upper side of the t a i l i s clove brown, the under side a v e l l -aneous to l i g h t buff. The well-developed pencil of hairs at the t i p of the t a i l i s usually black i n colour but i s white i n some ind i v i d u a l s . In Sorex obscurus the colour of the upper parts i s variable, being mummy brown, b i s t e r or clove brown and sometimes fuscous. The dorsal s t r i p e i s absent or i n d i s t i n c t , the sides and flanks becoming only s l i g h t l y and gradually paler than the back. The underparts are between drab gray and smoke gray, or sometimes s l i g h t l y paler. An avellaneous wash on the underparts i s usually more or less pronounced. The t a i l i s sharply bicoloar almost to the t i p , vinaceous b u f f to avellaneous below, clove Drown above deepening to fuscous black at the tt'.p. The p e n c i l of hairs at the t i p of the t a i l i s well-developed, and i s near-l y black or occasionally white. The differences between summer juvenile g. obscurus and - 2 8 -S. vagrans may be l i s t e d as follows: 1. The colour d i s t i n c t i o n between species i s less pronounced than i n any other pelage. I t i s almost impossible to d i s t i n -guish the species of any i n d i v i d u a l on the basis of juvenile summer pelage. 2. In series S. obscurus tends to be s l i g h t l y grayer, S. vag-rans s l i g h t l y browner. 3. The avellaneous wash on the underparts i s usually more pro-nounced i n S. obscurus than in S. vagrans. 4. The t a i l i s usually more d i s t i n c t l y bicolour i n S. obscuraas. F a l l molt i n Juveniles. The juveniles lose t h e i r summer pelage i n a regular molt i n the f a l l . Molt was i n progress when trapping was started, on October 2, 1949, but at this time most animals were in summer pelage or the very early stages of molting. No molt was observed i n August, and no trapping was c a r r i e d out i n Sept-ember. Females i n molt were taken from October 4 to November 12, 1949; males from October 4 to November 16, 1949. The l a s t female in f u l l summer pelage was taken on November 5 ; the l a s t male on November 14. The f i r s t female i n complete winter pelage was taken on October 28, the f i r s t male on November 12. From these dates i t appears that females tend to molt s l i g h t l y e a r l i e r than do males, but the average difference i n time i s less than two weeks. This i s contrary to the findings of Hamilton ( 1940 ), who states that i n Sorex fumeus " males tend to molt e a r l i e r in -29-spring and f a l l than females. " Molt starts in the centre of the back and gradually spreads forward over the head, backward toward the t a i l , and down over the sides. The pattern progresses more r a p i d l y on the body than on the appendages. The l a s t areas to molt are the u underside of the throat and the extremities of the forelimbs. Fi g . V shows the general progress of the molt pattern. The black areas on.the diagram represent areas of black pigmentation on the inner side of the skin. This dark pigmentation i s formed in the skin as the new hair grows i n , and a more precise idea of where the new fur i s coming in may be gained from i t than from examination of the furred side of the p e l t . In t h i s point also, Sorex vagrans and S. obscurus d i f f e r from S. fumeus. Hamilton ( 1940 ) states that i n the l a t t e r species n molt appears to commence on the b e l l y , and extends over the shoulders and middle of the back, the old fur p e r s i s t i n g longest about the ears and rump. " The f a l l molt i n the species under discussion approaches much more c l o s e l y the pattern de-scribed by Dalquest (1944 ) for Sorex vagrans collected i n Washington.. The only difference is that i n the shrews examined by Dalquest, molt i s i n i t i a t e d in two areas, one posterior on the back ( as found in the Point Grey population ) and a second, s t a r t i n g s l i g h t l y l a t e r , on the head. He states that the area around the ear i s the l a s t to molt. The animals described by him as " medium-aged adults " are i n a l l l i k e l i h o o d young of the year. Fig. V. Sequence of f a l l molt in juveniles - 3 0 -Since no captive animals were observed i n the process of molt, no precise estimate of the length of time required to complete molt were obtained, but i t seems l i k e l y that the entire process l a s t s ove* a period of two to three weeks.. Winter Pelage. In Sorex vagrans the upper parts are fuscous to fuscous-black, or sometimes clove brown. The colour on the back usually forms a dark saddle, d i s t i n c t from the paler sides and flanks which are snuff brown to b i s t e r . The underparts are pale smoke gray and lack a d i s t i n c t colour wash. The base of the fur through-out i s blackish mouse gray. The sides and back are flecked z throughout with white-tipped hairs, more numerous in some indiv-iduals than i n others. The t a i l i s similar i n colour to summer pelage but i s not so well furred. In'Sorex obscurus the upperparts are chaetura drab to chaetura black, sometimes almost blackish mouse gray, and usually somewhat darker p o s t e r i o r l y than on the head. The saddle i s absent or i n d i s t i n c t , the colour of the back blending evenly through drab on the sides and flanks to the paler colour of the underparts. There i s often a crescent of drab-coloured fur above the side glands sharply demarcated from the darker colour of the sides and back, and this colour occasionally extends forward to the forelimbs to form a narrow side s t r i p e . The underparts are smoke gray to pale smoke gray, l i g h t l y washed i n most individuals.with avellaneous. White-tipped hairs - 3 1 -s c a t t e r e d t h r o u g h t h e p e l a g e o n t h e s i d e s a n d h a c k a r e n u m e r o u s e n o u g h i n s o m e i n d i v i d u a l s t o g i v e a f r o s t e d a p p e a r a n c e . T h e m a i n d i f f e r e n c e s b e t w e e n S . o b s c u r u s a n d S . v a g r a n s i n w i n t e r p e l a g e m a y b e s u m m a r i z e d a s f o l l o w s : 1. T h e t w o s p e c i e s a r e m o r e n e a r l y d i s t i n c t o n p e l a g e c h a r a c -t e r i s t i c s i n w i n t e r t h a n a t a n y o t h e r t i m e o f t h e y e a r . M o s t s p e c i m e n s i n w i n t e r p e l a g e c a n r e a d i l y b e a s s i g n e d t o o n e s p e c i e s o r t h e o t h e r , a l t h o u g h s o m e a r e i n t e r m e d i a t e . 2 . T h e u p p e r p a r t s i n S . o b s c u r u s a r e g r a y e r o r s m o k i e r t h a n t h e r i c h d a r k b r o w n u p p e r p a r t s o f S . v a g r a n s . 3 . T h e s a d d l e f o r m e d b y d i s t i n c t l y d i f f e r e n t c o l o u r o f t h e b a c k a n d s i d e s i s m o r e p r o n o u n c e d i n S . v a g r a n s t h a n i n S . o b s c u r u s . 4. T h e u n d e r p a r t s o f S . v a g r a n s a r e m o r e s i l v e r y t h a n t h o s e o f 5. o b s c u r u s , a n d l a c k t h e a v e l l a n e o u s w a s h u s u a l l y p r e s e n t i n t h e l a t t e r . 5 . A s i n s u m m e r , t h e t a i l i s m o r e d i s t i n c t l y b i e o l o u r i n S . o b s c u r u s t h a n i n S . v a g r a n s . S p r i n g a n d S u m m e r M o l t s . T h e m o l t i n s p r i n g f r o m w i n t e r t o s u m m e r p e l a g e i s m u c h l e s s r e g u l a r t h a n t h e f a l l m o l t a n d t h e r e i s m a r k e d s e x u a l d i f f e r e n c e i n t h e t i m e a n d m a n n e r o f m o l t i n g , a p p a r e n t l y a s s o c -i a t e d w i t h r e p r o d u c t i v e a c t i v i t y . F o r t h i s r e a s o n t h e s e x e s a r e t r e a t e d s e p a r a t e l y . L o s s o f w i n t e r p e l a g e i n m a l e s i s v e r y s l o w a n d i r -- 3 2 -r e g u l a r , a n d s o m e i n d i v i d u a l s m a y " b e f o u n d w e l l i n t o t h e s u m m e r w i . t h p a r t s o f t h e w o r n w i n t e r c o a t s t i l l p e r s i s t i n g . T h e f i r s t i n d i c a t i o n o f m o l t w a s i n a n i n d i v i d u a l t a k e n o n J a n u a r y 22, 1931. I n t h i s a n i m a l t h e c e n t r a l r e g i o n o f t h e s i d e g l a n d , a n o v a l a r e a 8 x 3 m m . ,w4,s m o l t i n g . T h e n o r m a l w i n t e r f u r s t i l l c o v e r e d t h i s g l a n d s o t h a t i t u i » s n o t e v i d e n t e x t e r n a l l y . T h i s i n d i v i d u a l w a s n o t s e x u a l l y m a t u r e , t h e t e s t e s b e i n g i n t e r m e d i a t e i n s i z e b e t w e e n t h o s e o f n o n - b r e e d i n g j u v e n i l e s a n d m a t u r e a d u l t s t a k e n d u r i n g t h e h e i g h t o f t h e b r e e d i n g s e a s o n . I n a n o t h e r m a l e t a k e n o n t h e s a m e d a t e t h e s i d e g l a n d s a r e w e l l - d e v e l o p e d . T h e c e n t r a l a r e a i s n o t p i g m e n t e d i n t e r n a l l y , a n d t h e s h o r t , s t i f f b r i s t l e -l i k e h a i r s c h a r a c t e r i s t i c o f s e x u a l l y m a t u r e m a l e s a r e p r e s e n t , m a k i n g t h e g l a n d e x t e r n a l l y n o t i c e a b l e . T h e t e s t e s w e r e e n l a r g e d t o t h e s i z e o f t h o s e i n r e p r o d u c t i v e l y a c t i v e m a l e s . T h e a r e a i m m e d i a t e l y a r o u n d t h e s i d e g l a n d s h o w e d n o e v i d e n c e o f m o l t . A l l s h r e w s t r a p p e d a f t e r t h i s d a t e h a v e w e l l - d e v e l o p e d s i d e g l a n d s a n d e n l a r g e d t e s t e s . T h e n e x t a r e a t o m o l t i s a b a n d 2 t o 3 m m . w i d e a r o u n d t h e p e r i p h e r y o f t h e s i d e g l a n d . A n i m a l s i n t h i s c o n d i t i o n w e r e t a k e n f r o m F e b r u a r y 18 t o 2 4 , 1950. T h e c e n t r a l p a r t o f t h e s i d e g l a n d s i n t h e s e a n i m a l s h a d a l r e a d y m o l t e d , a n d t h e f u r w a s d i f f e r e n t i a t e d f r o m t h a t o v e r t h e r e s t o f t h e b o d y . N o m o l t o f t h e r e s t o f t h e b o d y a r e a w a s n o t e d u n t i l s o m e t i m e l a t e r . M a l e s i n w h i c h t h e g e n e r a l b o d y a r e a w a s m o l t i n g w e r e t a k e n f r o m A p r i l 2 2 t o 2 4 , 1950, a n d f r o m A p r i l 10 t o M a y 4 , 1951. T h e m o l t i s a l m o s t s i m u l t a n e o u s o v e r t h e e n t i r e b o d y , - 3 3 -alt&ough there i s a tendency for new summer pelage to appear f i r s t on the hack and l a s t on the head and throat. The f i r s t animals i n complete summer pelage showing no sign of molt were taken on A p r i l 23 , 1951 and A p r i l 30, 1950. This molt appears to he f a i r l y rapid and i s probably complete i n les s than a week. The central part of the side glands does not molt at t h i s time, although the fair of the peripheral r i n g i s usually replaced. Most of the animals taken after the beginning of May are i n summer pelage. A few, however do not molt with the majority i n the l a t t e r h a l f of A p r i l , but r e t a i n some or a l l of thei r worn winter pelage on int o the summer months. The follow-ing table shows the frequency with which males retaining some or a l l of the worn winter pelage are taken during the summer months. Table 3-* Percentage of Adult Males taken i n summer in p a r t i a l or Complete Winter Pelage.* May June July and August Percentage with winter pelage 32% 15% 9% Sample size 22 15 11 These late-molting individuals molt very slowly and follow no regular pattern. The black pigment areas on the under-side of the skin are usually very small and are often i n the form of a narrow band o u t l i n i n g the border of the external l i n e of d i v i s i o n between summer and winter pelage. There i s l i t t l e -34-r e g u l a r i t y i n molt pattern, but new fur seems to appear f i r s t on the back, often i n small patches. Worn wmnter fur tends to p e r s i s t longest on the head and at the base of the hind limbs. Thus there i s f i r s t a molt of the central region of the side glands as they develop i n January, then a molt of a periph-era l ring around the side glands i n the l a t t e r h a l f of February, a rapid molt of the body fur in the l a t t e r half of A p r i l in most animals, and a slow irr e g u l a r molt of body fur throughout the summer i n some in d i v i d u a l s . Only one animal was obtained which did not f i t into t h i s general pattern. This animal, taken on January 27, 1951, was molting the body f u r . Fresh pelage replaced worn winter pelage on the underparts and the anterior half of the upper parts, the posterior dorsal region retaining worn winter pelage. The side glands are well developed. The fresh pelage resembles that of summer in colour, but the fur i s longer and more dense than normal summer pelage. The spring molt i n females i s more regular than i n males, and i s complete i n a l l individuals. None were found i n winter pelage during the summer months. Molting animals were taken from February 20 to March 2, 1950, and from February 4 to March 9, 1951. The f i r s t animals i n complete summer pelage were taken on March 2, 1951 and March 15, 1950. The l a s t animals i n f u l l winter pelage were taken on February 14, 1951 and Feb-ruary 24, 195 0. Thus molt i s probably nearly or quite complete before mating takes place about the middle of March. Molt i s - 3 5 -probably rapid and i s almost simultaneous over the whole body. The f i r s t new fur appears on top of the head and shoulders, and rap i d l y spreads from t h i s point down over the back and sides. A second molt i n which fresh summer pelage replaces worn summer pelage occurs i n some and perhaps a l l adult females during the summer months. No great difference i n colour can be detected between the fresh and worn pelage except that i n most cases the worn pelage is s l i g h t l y paler, possibly due to wear and exposure. In some individuals the molt i s rapid, regular and simultaneous over the entire body, i n others i t i s slow and i r -regular, with small patcltes of new fur appearing almost anywhere on the body. This summer molt has been described by Dalquest ( 194-4 ) f o r Sorex vagrans i n Washington, although he does not mention the sex of the animals involved. In the Point Grey population, animals i n the process of summer molt were taken in June, July and August. The following table gives their f r e -quency of occurrence. Table4.Percentage of Females undergoing Summer Molt. May June July and August Percentage i n molt 0% 44% 45% Sample size 11 16 9 . One in d i v i d u a l i n which fresh summer pelage was replacing worn summer pelage was taken much e a r l i e r i n the year, on A p r i l 1, 1951. .This animalwks in^ the process of a very slow i r r e g u l a r molt. Some of these animals were obviously breeding, containing well-developed embryos i n the uterus. Others may or may not be breeding. The mammary glands are present but somewhat shrunken, indicating that the animal had been l a c t a t i n g but was not when caught, and the u t e r i , though somewhat swollen, do not contain macroscopically evident embryos. Summer Pelage i n Adults. In Sorex vagrans the upper parts are mummy brown or s l i g h t l y darker. The colour of the sides and flanks i s more or less sharply d i f f e r e n t i a t e d from that on the back, forming a more or Jess d i s t i n c t saddle. The sides and flanks are from verona brown to between wood brown and army brown. The underparts are pale smoke gray to pale o l i v e gray, with a s l i g h t wash of v i n -aceous buff to avellaneous present i n some in d i v i d u a l s . The t a i l i s as i n winter but is sparsely covered with short fur i n females and almost or completely naked in males. In Sorex obscurus the upper parts are clove brown and form an i n d i s t i n c t saddle or blend gradually into the o l i v e brown sides and flanks. The underparts are pale smoke gray to smoke gray, d i s t i n c t l y washed with between l i g h t pinkish cinnamon and vfenaceous buff. The t a i l i s as i n winter but, as i n S. vagrans, i s less heavily furred. The differences between S. obscurus and S. vagrans i n summer adult pelage may be summarized as follows: -37-1. The pelage differences between the tv/o species are less d i s -t i n c t than i n winter, but more d i s t i n c t than i n summer juveniles. 2. As i n winter, S. obscurus tends to be more.gray or smoky, S. vagrans more brown. 3 . The saddle effect i s usually more pronounced i n S. vagrans than i n S. obscurus. 4. In S. vagrans the buffy wash on the underparts i s absent or l i g h t , i n S. obscurus i t i s usually pronounced. Colour Abnormalities. > Jackson ( 1928 ) states that ,r shrews seldom exhibit abnormal colour phases such as melanism and albinism. " During the course of t h i s study six shrews showing d i s t i n c t colour ab-normalities were taken. Three of these ware summer juveniles, two ware i n winter pelage and one v»s an adult i n summer pelage. Of the juveniles, two females, both probably s . vagrans, taken on June 13 and June 23, 1950, are p r a c t i c a l l y i d e n t i c a l . They are much paler than normal. The paleness i s in part due to general l i g h t e r colour of the i n d i v i d u a l h a i r s , the colour of the base of the fur being l i g h t neutral gray instead of blackish mouse gray, and i n part to a l i b e r a l s p r i n k l i n g of white hairs throughout. As a r e s u l t the upperparts are between drab and hair brown, and the underparts are pale smoke gray. The other juvenile, a male S. obscurus, taken on July 10, 1950, i s apparently melanistic. The upperparts are somewhat -38-darker than usual - between clove brown and fuscous, and the underparts are scarcely paler - between hair brown and fuscous. The throat region i s s l i g h t l y paler than the b e l l y . The t a i l i s uniformly dark above and below, about fuscous in colour, and there i s no paling even toward the base on the underside. Of the mutants i n winter pelage, one appears to be similar to the pale juveniles described above. This animal, a male S. obscurus taken on'February 2 , ' 1 9 5 1 / i s generally paler throughout, the colour r e s u l t i n g from deep mouse gray instead of blackish mouse gray of the base of the f u r . Frosting with scattered white-tipped hairs i s more pronounced than usual. The drab colouration on the sides, i s lacking i n t h i s i n d i v i d u a l , the colour of the underparts blending evenly and gradually i n t o the colour of the upperparts. The t a i l i s spotted with white. A second male S. obscurus, taken on A p r i l 17, 1951, i s melanistic. The upperparts are between fuscous and black, the tip s of the i n d i v i d u a l hairs being only s l i g h t l y browner than their bases. The underparts are scarcely paler, chaetura drab to chaetura black. The t a i l is uniformly dark i n colour above and below - between clove brown and black. The only adult i n summer pelage showing abnormality i n colour i s a male S. vagrans taken on Hay 16, 1950. In this animal the l i g h t smoke gray colour of the underparts is extended dor s a l l y to form a crescent about 5 mm. wide above the side gland. - 3 9 -S o m e o f t h e h a i r s i n t h i s r e g i o n a r e w h i t e o r v e r y p a l e g r a y r i g h t t o t h e b a s e . T h e r e i s a p a l e b u f f m a s k f o r m e d b y a c o n c e n t r a t i o n o f w h i t e h a i r s b e t w e e n a n d s l i g h t l y b e h i n d t h e e y e s . T h e e y e s w e r e b l a c k i n c o l o u r . T h e c o l o u r a b n o r m a l i t i e s d i s c u s s e d a b o v e m a y b e , a n d p r o b a b l y a r e o f g e n e t i c r a t h e r t h a n e n v i r o n m e n t a l o r i g i n . A m a l e S o r e x o b s c u r u s . i n w i n t e r p e l a g e t a k e n o n F e b r u a r y 4, 1951 h a s a b n o r m a l p e l a g e , p r o b a b l y i n r e s p o n s e t o a w o u n d o r s e v e r e p a r a s i t i c i n f e c t i o n o f t h e s k i n . T h e r e i s a b a l d s p o t w i t h s c a r t i s s u e o n t h e r u m p a b o u t 7 m m . i n d i a m e t e r s u r r o u n d e d b y p u r e w h i t e h a i r s . S m a l l g r o u p s o f t h e s e w h i t e h a i r s a l s o o c c u r i n t h e a r e a s i n f r o n t o f a n d t o e a c h s i d e o f t h i s s p o t , g i v i n g t h e e n t i r e p o s t e r i o r d o r s a l r e g i o n a w h i t e s p o t t e d a p p e a r a n c e . Q u a n t i t a t i v e M o r p h o l o g i c a l V a r i a t i o n W h e n i t b e c a m e e v i d e n t t h a t t h e t w o s p e c i e s o f S o r e x r e p o r t e d b y C o w a n ( 1930 ) t o b e p r e s e n t a t P o i n t G r e y c o u l d n o t r e a d i l y b e d i s t i n g u i s h e d f r o m o n e a n o t h e r , i t w a s a l s o c l e a r t h a t i f a n y s e p a r a t i o n w a s e t o b e a c h i e v e d i t w o u l d h a v e t o b e o n t h e b a s i s o f a c a r e f u l a n a l y s i s o f q u a n t i t a t i v e m o r p h o l o g i c a l c h a r a c t e r i s t i c s . B u t m o r p h o l o g i c a l d i f f e r e n c e i n s i z e v a r i e s i n m a n y m a m m a l s , n o t o n l y w i t h s p e c i e s o r s u b s p e c i e s , b u t a l s o w i t h t h e a g e a n d s e x o f t h e a n i m a l . J a c k s o n ( 1928 ) s t a t e s t h a t " s o f a r a s i s k n o w n t h e r e i s n o s e x u a l v a r i a t i o n i n c o l o u r , s i z e , o r p r o p o r t i o n s i n a n y o f t h e A m e r i c a n l o n g - t a i l e d s h r e w s " a n d t h a t » e x t e r n a l l y s h r e w s - 4 0 -display l i t t l e v a r i a t i o n with age. " He l i s t s c e r t a i n c r a n i a l and dental features which change with advancing age, but these are related not so much to size as to o s s i f i c a t i o n of the s k u l l and tooth wear. However Brambell ( 1935' ) and Hamilton ( 1940 ) have shown that in at least two species of Sorex ( araneus and fumeus ) there i s one quantitative character that varies considerably with age and sex. They found that adult males are heavier than adult females, and that adults are heavier than immature animals. In order to obtain as high a degree of precision as possible i n the analysis of difference between species, a de-t a i l e d analysis of sex and age va r i a t i o n was ca r r i e d out. Aver-age differences, although small, were found to exist, and i n some cases were s i g n i f i c a n t . Sexual Variation. In determining morphological differences between sexes, the two species and two age groups were treated separately. The species were divided on the a r b i t r a r y basis outlined i n the section dealing with quantitative v a r i a t i o n between species. The two age groups were separated on the basis of sexual matur-i t y , pelage c h a r a c t e r i s t i c s and tooth wear. Treatment was s p l i t i n t h i s manner since there was known to he v a r i a t i o n due to both age and species. Jackson ( 1928 ) states that " there i s no sexual v a r i a t i o n i n colour, size or proportions i n any of the American long-tailed shrews." Brambell ( 1935 ) and Brambell and H a l l -41-( 1936 ) state that there are average differences i n weight be-tween sexes i n adult Sorex araneus and S. minutus, with males decidedly heavier than females. Hamilton ( 1940 ) gives aver-age external measurements for adult male, adult female, immature male and immature female S. fumeus. His samples vary i n size from 14 to 26 individuals." His data show a s l i g h t l y greater t o t a l length i n males than females, but the difference i s prob-ably not s i g n i f i c a n t . He does indicate that adult males are probably s i g n i f i c a n t l y heavier than adult females. In view of the fact that some s l i g h t sexual v a r i a t i o n i n size e x i s t s , at least i n some species, the Point Grey popul-ation was analysed to determine what average differences, i f any, existed between the sexes. In both Sorex vagrans and S.  obscurus and i n both age groups there was found to be a trend toward larger size i n males. This trend i s more pronounced i n adults than i n juveniles, and i s more pronounced i n my sample of S. vagrans than i n S. obscurus, probably because of larger sample size i n the former. Average values, ranges, standard deviations, standard errors and c o e f f i c i e n t s of v a r i a b i l i t y f o r the ten features measured are given i n the appendix. In adult S. obscurus males are s i g n i f i c a n t l y greater than females ( at P« .01 ) only i n weight and i n t e r o r b i t a l breadth. The difference i n condylobasal length i s s i g n i f i c a n t at P =.05, but not at P •= .01. In a l l other features the males average s l i g h t l y but not s i g n i f i c a n t l y larger than females. The difference -42-in weight i s well marked in spite of the fact that females during the breeding season were pregnant or l a c t a t i n g , and the weight of the embryos and mammary tissue was not deducted from the t o t a l weight of the females. In adult S. vagrans males were found to be s i g n i f i c -antly greater ( P c .01 ) than females i n length of the hind foot, weight, condylobasal length, cr a n i a l breadth, length of the maxillary tooth row and pa l a t a l length. The males are larger than females, though not s i g n i f i c a n t l y so, i n t o t a l length, i n -t e r o r b i t a l breadth and maxillary breadth. In females the t a i l aveaaged s l i g h t l y longer than i n males, but not s i g n i f i c a n t l y so. As i n adult S. obscurus the difference in weight i s more marked than are other differences, i n spite of breeding females included i n the sample. There are no s i g n i f i c a n t morphological differences between sexes i n juvenile S. obscurus at P=.01, but the max-i l l a r y tooth row i s s i g n i f i c a n t l y longer i n males at P-.0.5. The trend toward larger size i n males i s consistent throughout thi s group i n a l l features except weight. In juvenile S. vagrans males are s i g n i f i c a n t l y larger than females i n t o t a l length, length of the hind foot, c r a n i a l breadth, i n t e r o r b i t a l breadth and length of the maxillary tooth row. The females are,slightly but s i g n i f i c a n t l y larger ( than males i n maxillary breadth, and p a l a t a l length. This i s i n -consistent with r e s u l t s i n other groups and may possibly be due -43-to error i n measurement. In general, then, differences between sexes are not well marked. But males tend to be larger and to have broader sk u l l s than do females. The marked difference i n weight i n adults i s not evident i n juveniles and i s probably correlated with sex-ual maturity. Age Variation. Variation with age i s continuous and any separation into age groups must be ar b i t r a r y . Any shrews taken p r i o r to December 31 of the year i n which they were born were classed as juveniles; a f t e r t h i s time they were classed as adults. Since no trapping was carried out u n t i l l ate January, and the breeding season starts i n males i n mid-February and i n females by early March, a l l animals classed as adults are sexually mature or near-l y so. During the summer, when both adults and juveniles were • taken, they were r e a d i l y separable on the basis of pelage and dental c h a r a c t e r i s t i c s , as well as by" the condition of the re-productive organs. The age groups defined i n th i s manner are not s t r i c t l y mutually exclusive, since breeding is continuous throughout the summer. Thus animals classed as juveniles may vary i n age from one to 8 months, and adults from fcS to 17 months.. In spite of thi s overlap i n age the basis for separation i s probably v a l i d . Increase i n weight at least has been shown by Brambell •( 1935 ) -44-and Hamilton ( 1940 ) to be correlated not so much with age as with the attainment of sexual maturity. Shrews a l l reach sexual maturity at the same time in the spring regardless of whether they were born in the spring or late summer of the previous year. An attempt to age shrews more precisely was made on the basis of quantitative measurements of tooth wear. But v a r i a t i o n i n o r i g i n a l tooth size, possibly due to intergradation between species?was so great that c l a s s i f i c a t i o n on t h i s basis was subject to too much error to be practicable. The growth rate i n shrews must be extremely high in the f i r s t three weeks of l i f e before the young are weaned. At the time youmg shrews are f i r s t taken i n traps they have very nearly reached f u l l adult size, although they are considerably l i g h t e r than adults. The following table compares t o t a l length and weight in juvenile shrews taken between A p r i l 29 and May 2.0 with aver-age value of adults. At this time the juveniles are from three to s i x weeks old. Table.7. Comparative size of young juvenile and adult. Adults Juveniles (3-6 weeks old] Mean length 108.74 mm. 108.06 mm. 102.63 mm. 101.67 mm. f. of Adult length 94% 94^ Mean weight 6.77 gm. 6.06 gm. 4.14 gm. 4.07 gm. % of adult weight 61% • 67% - 4 5 -T h u s 94- p e r c e n t o f g r o w t h i n l e n g t h i s a c c o m p l i s h e d by t h e t i m e t h e s h r e w s a r e a m o n t h o l d . T h e i n c r e a s e i n w e i g h t f r o m w e a n i n g t o a d u l t h o o d i s m o r e p r o n o u n c e d t h a n i n c r e a s e i n l e n g t h , b u t m o s t o f t h i s i n c r e a s e t a k e s p l a c e i n e a r l y s p r i n g a n d i s c o r r e l a t e d w i t h t h e a t t a i n m e n t o f s e x u a l m a t u r i t y . T h e a n a l y s i s o f v a r i a t i o n w i t h a g e w a s c a r r i e d o u t s e p a r a t e l y f o r e a c h s e x a n d e a c h s p e c i e s . V a l u e s f o r m e a n , s t a n -d a r d d e v i a t i o n , r a n g e , s t a n d a r d e r r o r o f t h e m e a n , a n d c o e f f i c i e n t o f v a r i a b i l i t y f o r t h e t e n f e a t u r e s e x a m i n e d a r e i n c l u d e d i n t h e s t a t i s t i c a l t a b l e s i n t h e a p p e n d i x . D i f f e r e n c e s b e t w e e n a g e g r o u p s a r e n o t m a r k e d b u t i n g e n e r a l a r e m o r e e v i d e n t t h a n a r e d i f f e r e n c e s b e t w e e n s e x e s . B o d y s i z e a n d w e i g h t a r e c o n s i s t e n t l y g r e a t e r i n a d u l t s , a l t h o u g h t h e t a i l d o e s n o t i n c r e a s e i n l e n g t h . I n a d u l t s t h e s k u l l b e -c o m e s b r o a d e r a n d m o r e h e a v i l y o s s i f i e d . T h e m i d - d o r s a l s u t u r e i s s c a r c e l y c l o s e d i n j u v e n i l e s ; i n a d u l t s i t i s c o m p l e t e l y c l o s e d , t h e s a g i t t a l c r e s t i s w e l l d e v e l o p e d , a n d t h e l a m b d o i d a l c r e s t i s s l i g h t l y t o w e l l d e v e l o p e d . I n m a l e S . o b s c u r u s t h e a d u l t s a r e s i g n i f i c a n t l y l a r g e r t h a n j u v e n i l e s i n t o t a l l e n g t h , w e i g h t a n d i n t e r o r b i t a l b r e a d t h ( P =.01 ) ; t h e y a r e l a r g e r , b u t n o t s i g n i f i c a n t l y s o i n l e n g t h o f t h e h i n d f o o t , m a x i l l a r y b r e a d t h a n d p a l a t a l l e n g t h . J u v e n i l e s a r e s i g n i f i c a n t l y l a r g e r t h a n a d u l t s i n l e n g t h o f t h e m a x i l l a r y t o o t h r o w ( P- .01 ) a n d c o n d y l o b a s a l l e n g t h ( .05 ) . -46-In male S. vagrans, adults are significantly greater than juveniles in total length, length of the hind foot, weight, cranial breadth, interorbital breadth and maxillary breadth ( P - .01 ) , and in palatal length ( P - ..05 ). The juveniles have a significantly longer maxillary tooth row ( P - .01 ) and t a i l ( P =. 05 ) . Significant differences in female S. obscurus are noticeable in greater weight and maxillary breadth ( P •= .01 ) , and total length ( P = .05 ) in adults, and in longer maxillary tooth row ( P - .01 ) and greater cranial breadth ( P =.05 ) in juveniles. Adults are slightly but not significantly greater than juveniles in length of the hind foot and interorbital breadth. In female S. vagrans adults show significantly greater total length, length of the hind foot, weight and interorbital breadth, juveniles have significantly greater condylobasal length, length of the mamillary tooth row and palatal length. Cranial breadth and t a i l length are slightly but not significantly greater in adults. The most consistent differences throughout the four separate groups are in total length, weight, interorbital breadth, and length of the maxillary tooth row. Differences in weight are marked and in many cases may be used to differentiate be-tween adults and juveniles. Cranial differences are neither as marked nor as consistent as the increase in body size, which - 4 7 -i s r e f l e c t e d i n g r e a t e r w e i g h t a n d t o t a l l e n g t h o f a d u l t s . T h e r e i s l i t t l e i n d i c a t i o n t h a t t h e s k u l l i n c r e a s e s i n l e n g t h o r b r e a d t h t h r o u g h t h e c r a n i u m . T h e i n c r e a s e s n o t e d i n i n t e r o r b i t a l a n d m a x i l l a r y b r e a d t h a r e p r o b a b l y d u e t o h e a v i e r o s s i f i c a t i o n i n a d u l t s . J u v e n i l e s h a v e a c o n s i s t e n t l y g r e a t e r m a x i l l a r y t o o t h r o ? / b e c a u s e t h e t e e t h a r e f u l l y d e v e l o p e d b u t u n w o r n . V a r i a t i o n i n n u m b e r o f t a i l v e r t e b r a e . S o r e x v a g r a n s c a n n o t b e d i f f e r e n t i a t e d f r o m S . o b s c u r u s o n t h e n u m b e r o f t a i l v e r t e b r a e . T h e n u m b e r w a s f o u n d t o b e v a r i a b l e i n b o t h s p e c i e s , r a n g i n g f r o m 15 t o 18 i n S . v a g r a n s a n d f r o m 17 t o 19 i n S . o b s c u r u s ( s e e F i g . V I ) . S . v a g r a n s u s u a l l y h a s 16 o r 17 c a u d a l v e r t e b r a e , a n d S . o b s c u r u s u s u a l l y 18. N o p u b l i s h e d r e c o r d s o f c a u d a l v e r t e b r a e c o u n t s f o r S o r e x e x i s t t o t h e w r i t e r ' s k n o w l e d g e . C o m p a r i s o n w i t h o t h e r p o p u l a t i o n s o f S . . o b s c u r u s a n d S . v a g r a n s , a n d w i t h o t h e r s p e c i e s o f S o r e x a r e t h e r e f o r e i m p o s s i b l e . T h e n u m b e r o f t a i l v e r t e b r a e i s c o r r e l a t e d w i t h t a i l l e n g t h . A n i m a l s h a v i n g m o r e v e r t e b r a e t e n d t o h a v e l o n g e r t a i l s i n b o t h s p e c i e s . B u t f o r a g i v e n n u m b e r o f v e r t e b r a e t h e t a i l s o f S . o b s c u r u s h a v e a g r e a t e r a v e r a g e l e n g t h t h a n t h o s e o f S . v a g r a n s . ( s e e F i g . V I I ) . T h u s t h e g r e a t e r t a i l l e n g t h i n S . o b s c u r u s i s d u e i n p a r t t o a n i n c r e a s e i n t h e a v e r a g e n u m b e r o f v e r t e b r a e a n d i n p a r t t o a n i n c r e a s e i n a v e r a g e v e r t e b r a l l e n g t h . F i g . VI. Number of t a i l vertebrae i n Sorex vagrans and Sorex obscurus. 2 4 20 i 16 ; o. V «• • ! o1 I CD i m 8 ! 4 I | | S. VAGRANS S. OBSCURUS 15 16 17 18 19 Number of t a i l vertebrae F i g . VII. Relation between t a i l length and number of t a i l vertebrae. 55 L | I , , • ' L 15 16 17 18 19 Number of t a i l vertebrae - 4 8 -Variatlon between species. Quantitative and qualitative morphological character-istics are generally accepted as the only practical basis for the recognition of species among mammals. Other theoretical criteria such as reproductive isolation and genetic difference are be-coming more and more important but are as yet too laborious to be practical in most cases. The basis of mammalian taxonomy re-mains largely morphological. Blair ( 1 9 4 3 ) states that until such time as conventional system of classification is revised to use the criteria furnished by the experimental method, the teann species must be restricted to museum species, that is those species units based on morphological and geographical criteria alone. n Present descriptions of mammalian species and subspecies are based on certain standard skull and body measurements, on dental characteristics, and on pattern and colour in pelage. Of the practical criteria, quantitative data can be more precisely defined than qualitative variation in pelage colour. The latter is subject in a large degree to personal judgement and error, and is difficult to define satisfactorily. Cowan ( 1930 ) reports two species of shrews from Point Grey, Sorex vagrans vagrans Baird and Sorex obscurus setosus Elliot. The material collected during the present study cer-tainly contains some animals which closely fl.t published des-criptions of S.v. vagrans, and others fitting descriptions of S.o. setosus. But there is no single morphological character--49-i s t i . c , either quantitative or q u a l i t a t i v e , or simple r a t i o of any two which w i l l separate the two species i n the population complex studied. Jackson ( 1928 ) has the following to say regarding the r e l a t i o n s h i p between S. vagrans and S. obscurus. " The members of the vagrans-obscurus group constitute several forms the exact relationships of which i n seme cases are complicated and d i f f i c u l t to solve. The relationship between S.v. monticola and S.o. obscurus, both of which occur i n the Hocky Mountains, i s paarticularly perplexing. Actual intergradation between these two apparently does not exist, although cer t a i n specimens are d i f f i c u l t to i d e n t i f y . As one passes eastward from the coast region of Washington there is noticeable an increase in size , i n length of t a i l , and i n size of s k u l l and teeth of S. vagrans, TRfoich becomes recognizable i n the subspecies monticola. Exactly the reverse occurs i n the representative ( S.o. setosus ) of the species obscurus.from the coast region to i t s intergrading form, the subspecies obscurus. Intergradation of S.o. obscurus with setosus, and of S.v. vagrans with monticola i s c l e a r l y demonst-rated. The re s u l t i s , that i n the coast region of Washington and B r i t i s h Columbia, where representatives of the species vagrans and obscurus occur, they are contrastedly d i f f e r e n t , whereas throughout the Hocky Mountains, wherever the two species occur, they can be separated only by the most careful study. " Diagnostic c h a r a c t e r i s t i c s by which g. vagrans i s -.50-distinguished from S. obscurus by Jackson ( 1928 ) are e n t i r e l y a matter of s i z e . The d u l l coloured pelage of shrews lacks variety, and the teeth are very simple and s i m i l a r i n a l l res-pects, except s i z e . Tooth size i s not a good character since the teeth show pronounced wear with age. I f S. obscurus i s to be distinguished from S. vagrans in the Point Grey population on a morphological basis, the sep-aration must be a r b i t r a r y . None of the eleven morphological characters analysed ( t h r e e external measurements, s i x cr a n i a l measurements, weight and number of t a i l vertebrae ) w i l l com-p l e t e l y separate the two species. Frequency-distribution curves { see Appendix ) for these c r i t e r i a may be bimodal or skewed, but a l l show intergradation. i n no case are there two separate curves. Arbitrary separation was attained by consideration of the two characters showing greatest divergence, t a i l length and length of the maxillary tooth row. Ninety-five percent of the material at hand could be separated i n t h i s manner, i n the remaining f i v e percent the characters were eithe r contradictory or both close to the d i v i d i n g l i n e between species. This f i v e percent of the material was disregarded i n the analysis of s p e c i f i c v a r i a t i o n . Frequency d i s t r i b u t i o n histograms for each sex and age class, and s t a t i s t i c a l tables showing mean values, ranges, stan-dard deviations, standard errors of the means, c o e f f i c i e n t s of v a r i a b i l i t y and sample s i z e are included i n the appendix. If the two species are separated on the basis of these - 5 1 -c r i t e r i a , and the data are analysed s t a t i s t i c a l l y i n separate sex and age groups, S. obscurus i s found to be s i g n i f i c a n t l y larger than S. vagrans on a l l c r i t e r i a examined, and i n a l l sex and age groups except i n weight of adults. Here there i s an aver-age difference of f i v e percent between the two species, but the high degree of v a r i a b i l i t y i n adults with respect to weight, and the small sample s i z e , e s p e c i a l l y i n females, renders the d i f f -erence i n s i g n i f i c a n t . Thus a trend toward larger size i n the two characters selected as an arbitrary basis f o r separation i s consistent i n the other eight characters analysed. Long-tailed indiv i d u a l s have larger bodies and are heavier, and have longer and broader Skulls than do s h o r t - t a i l e d i n d i v i d u a l s . Of the s k u l l measurements, the difference i n c r a n i a l breadth is less thaniin other dimen-sions, but even here the difference between the two species i s highly s l g n i f icant. Differences i n size are i n general consistent with pelage differences, although v a r i a t i o n in the l a t t e r is d i f f i -c u l t to define p r e c i s e l y . • DISCUSSION. Taxonomio pos i t i o n of the Point Grey population. Most mammalian taxonomists agree that the chief c r i t e r -ion f o r species is the absence of interbreeding. Absence of morphological intergradation i s accepted as factual evidence for the absence of interbreeding. H a l l ( 1 9 4 3 ) states that ,T the c r i t e r i o n . . . . for species i s lack of intergradation. Ir This i s the c r i t e r i o n which has been used in the present system of mammalian taxonomy. B l a i r ( 1943 ) suggests tha t the present conventional taxonomic system does not allow d i s t i n g t i o n between evolutionary levels i n s p o l i a t i o n . He recognizes two categories of species populations. The f i r s t of these, which he terms i n c i p i e n t species, he defines as " a natural population that i s at least p a r t i a l l y f e r t i l e with some other population but i s i n h i b i t e d from breeding with i t by some i s o l a t i n g mechanism or mechanisms. The second category, which he terms a cenospecies, he describes as a" a natural population that i s i n f e r t i l e ( can produce only s t e r i l e hybrids or none at a l l ) with every other population. " He states that i n c i p i e n t species are diverging populations that have not yet attained complete i n t e r s t e r i l i t y . I s o l a t i n g mechanisms i n i n c i p i e n t species are usually geographical or ecological, but may be sexual where the two i n c i p i e n t species occur together i n nature yet f a i l to interbreed. Psychological incompatability and mechanical d i f f i c u l t y in mating are classed as sexual i s o l a t i n g mechanisms. B l a i r c i t e s instances where - 5 3 -i n c i p i e n t species of. Peromyscus are f u l l y i n t e r f er t i l e under laboratory conditions, yet there i s no evidence for hybridization in the m i d . Dice ( 1943 ) gives further instances of t h i s phenomenon. He states that in the laboratory E'er omy sous leu co pus and P. gossypinus are completely i n t e r f er t i l e . The ranges of these two species overlap i n several areas i n the southeastern United States, and where they do overlap, both species occupy the same habitat. '» Yet there i s no evidence for their interbreeding in nature except for two presumed hybrids from Alabama. " ( Dice, 1943 ) . • Hybridization between mammalian species in nature appears to be extremely rare. H a l l ( l$43a ) makes the follow-ing statement i n t h i s connection. " My guess i s , therefore, that among wild mammals of North America hybrids do not occur more often than once i n 15,000 ind i v i d u a l s . '» He describes three ground s q u i r r e l s which he believes to be hybrids between species of C i t e l l u s . Two apparent hybrids or intergrades between C i t e l l u s  armatus and C.. r i c h a r d s o n i i are the only Specimens examined by him from a l o c a l i t y where the two species* ranges overlap. Only more extensive c o l l e c t i o n i n this, region would determine these specimens are hybrids or intergrades. I f there are only a few indivi d u a l s showing c h a r a c t e r i s t i c s d i s t i n c t l y intermediate be-tween the two species ( hybrids )-, then C. armatus and C. r i c h -i — — — — — ardsonii would remain as species i n good standing. If,' on the other hand, the morphological features used to distinguish the two species show continuous v a r i a t i o n between the values -34-c h a r a c t e r i s t i c of the two parent populations ( intermediate individuals intergrades ) , the two are comspecific. The t h i r d i n d i v i d u a l , an apparent hybrid between C i t e l l u s armatus and C. Beldingi, was o r i g i n a l l y described by Davis? ( 1939 ) , who states that t h i s animal was the only animal showing intermediate c h a r a c t e r i s t i c s i n 39 ground s q u i r r e l s collected from the same meadow. H a l l also r e f e r s to three apparent hybrids between species of Microdipodops described by him i n an e a r l i e r paper. Undoubtedly there are further references to natural hybrids among American mammals, but these examples serve to dem-onstrate their r a r i t y . In a l l cases where hybridization has been shown to occur, the number of hybrid individuals was very small, and the parent stocks remained d i s t i n c t . B l a i r ( 1943 ) c i t e s reports of hybridization i n toads, sunfish and juncos, occurring under unusual b i o t i c or environmental conditions, but no reports of mass hybridization i n mammals exist to the writer's knowledge. Even i n f i s h , vh.ere hybrids are more common th a ^ t h e y are i n mammals, intergradation i s taken as an indication of incomplete seeciation. " I f under appropriate circumstances the two dis.tinet 1 forms come together and interbreed regularly, I would take t h i s as evidence that they have reverted from the s p e c i f i c to the subspecific category of d i f f e r e n t i a t L o n . " ( Hubbs, 1943 ). With these points i n mind, l e t us now examine the population found at Point Grey. Here two species of shrews, Sorex vagrans and S. obscurus are reported to occur ( Cowan, -55-1950 ). Their geographic ranges overlap broadly over much of the western United States and southwestern Canada. Some habit-at selection may be shown, but the two species coinhabit other areas i n addition to Point Grey. Yet no evidence of intergrad-ation has been reported from these areas. The material c o l l e c t e d i n the present study included some specimens t y p i c a l o f both species. But a l l morphological c h a r a c t e r i s t i c s examined show intergradation ( see Appendix ). The number of individuals which could be classed as intergrades i s smallest when t a i l length and length of the maxillary tooth row are considered as the basis of separation. On the basis of these two characters, the population was s p l i t into two a r b i t r a r y units corresponding to the species S. vagrans and S. obscurus, and s t a t i s t i c a l analysis of a l l quantitative features was c a r r i e d out. S i g n i f i c a n t morphological differences between species were found, but while such differences may characterize evolution at the subspecific l e v e l , they are not i n themselves adequate as c r i t e r i a for species. I f intergradation i s accepted as a c h a r a c t e r i s t i c of subspecies rather than species, then the shrews of Point Grey must be classed as a single species. I f t h i s population i s considered as a single species, i t must have had a diphyletic o r i g i n both i n Sorex vagrans and. i n Sorex obscurus. These two might well be i n c i p i e n t species according to B l a i r ' s d e f i n i t i o n , although i n t e r f e r t i l i t y or lack of i t has not been demonstrated - 5 6 -between the two. The geographic ranges of the two species over-lap over most of the western United States and i n southern B r i t -ish Columbia. Hence i s o l a t i n g mechanisms must be either ecologic or sexual. At Point Grey there is no apparent ecological i s o l -ation. Although some small degree of difference i n habitat preference was shown to exist between the two species, they were frequently taken i n the same habitat at the same time. Hence $here was opportunity f o r sexually mature adults of d i f f e r e n t sex and species to meet. The existence of sexual or genetic b a r r i e r s could not be demonstrated, but their absence may be inferred, since evidence for intergradation through crossbreed-ing i s good. There i s evidence that breakdown of i s o l a t i n g mechan-isms between S. vagrans and S. obscurus at Point Grey has not been complete. Frequency-distribution histograms for quantit-ative morphological features are not normal i n d i s t r i b u t i o n but tend to be skewed or bimodal ( See Appendix ). The influence of the two parent populations.:: i s quite evident. I f there were no b a r r i e r s to crossbreeding and hybrid individuals comprised a large part of the population, the curves might be expected to be normal or nearly so, provided the features examined show blending inheritance, and not simple Mendelian segregation. Hubbs ( 1940 j states that at least i n f i s h hybrids, blending inheritance of systematic characters i s a very general r u l e . It might also be expected i n mammals. When Sorex vagrans and S. obscurus from Point Grey are separated on the arbitrary basis outlined previously, and aver-age external and cran i a l measurements are compared with t y p i c a l measurements given by Jackson ( 1928 ) , i t is found that the arb i t r a r y species d i f f e r considerably from the t y p i c a l . Sorex  vagrans from Point Grey i s generally s l i g h t l y larger than t y p i c a l S. vagrans, and S. obscurus from Point Grey i s considerably smaller than is t y p i c a l . This i s probably due to the influence of hybrid-i z a t i o n , leading to the inclu s i o n of some hybrids i n both a r b i t -rary species populations considered. Additional evidence of p a r t i a l but not complete break-down of i s o l a t i o n mechanisms was found i n the study of reprod-uction. The average l i t t e r s i z e i n the Point Grey population, based on counts of healthy embryos, was only 5.14, as compared with Jackson's ( 1928 ) values of 5.4 f o r S. obscurus and 5*8 for S. vagrans. Also, embryonic mortality is high i n compar-ison with Sorex araneus ( Brambell 1935 ). These facts may be evidence of lower f e r t i l i t y and some hybrid i n v i a b i l i t y i n the interbreeding population. Additional evidence for hybrid o r i g i n of the popul-ation i s i t s high v a r i a b i l i t y . In Table the' c o e f f i c i e n t s of v a r i a b i l i t y of nine measurements are compared with those for a B r i t i s h Columbia coastal mainland population of adult Sorex  obscurus longicauda obtained by Cowan ( 1941 ) . The Point Grey population i s consistently more va r i a b l e . It might^be TABLE 8. Comparative V a r i a b i l i t y of the Point Grey population and a B.C. coastal population of S.o. longicauda. Characteristic C o e f f i c i e n t of v a r i a b i l i t y Point Grey <^ ad. JS.o. longicauda Total length 5.19 5.04 T a i l length 11.22 8.20 Hind foot 4.10 5 .08 Condylobasal length 1.94 1.16 P a l a t a l length 4.12 3.28 C r a n i a l breadth 2.55 2.15 I n t e r o r b i t a l width 5.29 4.20 Mamillary width 4.96 3.3 Tooth row 4.26 . 2.45 Figures quoted from Cowan, 1941. -58-e x p e c t e d t h a t i f t h e P o i n t G r e y p o p u l a t i o n w e r e m o n o p h y l e t i c i t w o u l d s h o w l e s s v a r i a t i o n , s i n c e o n l y a d u l t m a l e s , i n s t e a d o f t h e e n t i r e a d u l t p o p u l a t i o n i s c o n c e r n e d , a n d t h e s a m p l e s i z e i s l a r g e r . H o w e v e r i t i s n o t v e r y m u c h m o r e v a r i a b l e t h a n t h e p o p u l a t i o n o f S . o . l o n g i c a u d a . I t i s r e a s o n a b l e t o e x p e c t t h a t a d i p h y l e t i c p o p u l a t i o n s h o u l d s h o w g r e a t e r v a r i a b i l i t y t h a n o n e o f m o n o p h y l e t i c o r i g i n . W h e t h e r t h e p o i n t G r e y p o p u l a t i o n i s t e r m e d a s p e c i e s o r a h y b r i d p o p u l a t i o n o f t w o s p e c i e s i s a m a t t e r o f p e r s o n a l j u d g e m e n t , i f e x i s t i n g c o n v e n t i o n s w i t h r e g a r d t o m a m m a l i a n t a x o n o m y a r e t a k e n i n t o c o n s i d e r a t i o n , i t m i g h t b e s t b e c a l l e d a s p e c i e s . B u t i t i s a s p e c i e s f o r m e d b y t h e l o c a l h y b r i d i z -a t i o n o f t w o i n c i p i e n t s p e c i e s , S o r e x v a g r a n s a n d S o r e x o b s c u r u s . B r e a k d o w n o f s e x u a l a n d g e n e t i c i s o l a t i n g m e c h a n i s m s h a s p r o b -a b l y n o t b e e n c o m p l e t e , a l t h o u g h c r o s s b r e e d i n g m u s t b e n o t a t a l l i n f r e q u e n t . I t w o u l d b e i n t e r e s t i n g t o k n o w w h e t h e r h y b r i d i z a t i o n o c c u r s w h e r e t h e t w o s p e c i e s o c c u r i n t h e s a m e h a b i t a t i n o t h e r a r e a s w h e r e t h e i r g e o g r a p h i c r a n g e s o v e r l a p . A n a l y s i s o f l a r g e s e r i e s o f b o t h s p e c i e s w o u l d b e i n t e r e s t i n g a n d m i g h t p e r h a p s t h r o w m o r e l i g h t o n t h e p r e s e n t s i t u a t i o n . O n l y a f t e r s u c h a s t u d y h a d d e t e r m i n e d w h e t h e r t h e p h e n o m e n a e x h i b i t e d b y t h e P o i n t G r e y p o p u l a t i o n a r e c o n f i n e d t o i t o r o c c u r m o r e o r l e s s f r e q u e n t l y w h e r e v e r t h e t w o f o r m s a r e c o i n h a b i t i n g c a n t h e s p e c i f i c s t a t u s o f S . v a g r a n s a n d S . o b s c u r u s b e s e t t l e d . - 5 9 -S U M M A R Y . 1. A s t u d y o f s h r e w s o f t h e g e n u s S o r e x w a s u n d e r t a k e n o n t h e c a m p u s o f t h e u n i v e r s i t y o f B r i t i s h C o l u m b i a a t p o i n t G r e y , V a n c o u v e r . S h r e w s w e r e o b t a i n e d b y s n a p - t r a p p i n g f r o m O c t o b e r 1949 t o M a y 1951. 2;. S o r e x . g a g r a n s a n d S o r e x o b s c u r u s o u t n u m b e r e d a l l o t h e r s p e c i e s o f m a m m a l s p r e s e n t i n t h e s t u d y a r e a , c o m p r i s i n g f r o m 50.9 t o 56.5 p e r c e n t o f t h e t o t a l s m a l l m a m m a l p o p u l a t i o n i n d i f f e r e n t h a b i t a t t y p e s . 3 . A s s o c i a t e d s m a l l m a m m a l s , i n o r d e r o f a b u n d a n c e , w e r e B e r o -m y s c u s , H e u r o t r i c h u s , , a a p u s , S o r e x b e n d i r i i , M 1 c r o t u s ctownsendj i ,  M i c r o t u s s e r p e n s a n d S c a p a n u s . 4. T h e a v e r a g e l i f e s p a n o f s h r e w s i s l e s s t h a n a y e a r , n o a n i m a l s s u r v i v i n g t o t h e a g e o f t w o y e a r s . S e a s o n a l v a r i a t i o n i n n u m b e r s i s g r e a t , w i t h t h e p o p u l a t i o n a t t h e p e a k i n J u l y a b o u t t w i c e t h a t i n A p r i l , b e f o r e t h e f i r s t y o u n g a r e r u n n i n g . 5. S e x r a t i o s w e r e f o u n d t o b e s i g n i f i c a n t l y d i f f e r e n t f r o m n o r m a l o n l y i n a d u l t s d u r i n g M a y a n d J u n e , a t w h i c h t i m e t h e p o p u l a t i o n i s 70 p e r c e n t m a l e s . 6 . M a l e s h r e w s d i d n o t m a t u r e u n t i l F e b r u a r y o f t h e y e a r f o l l o w -i n g t h e o n e i n w h i c h t h e y w e r e b o r n . A l m o s t a l l f a r e d e a d b y t h e e n d o f A u g u s t , a l t h o u g h a d u l t m a l e s w e r e t a k e n i n O c t o b e r 1949 a n d J a n u a r y 1951. I n t h e s e t h e t e s t e s s h o w e d n o s i g n o n r e g r e s s i o n - 6 0 -7. F e m a l e s " b e c a m e s e x u a l l y m a t u r e i n M a r c h o f t h e y e a r f o l l o w -i n g t h e o n e i n w h i c h t h e y w e r e b o r n . T h e f i r s t l i t t e r s a r e b o r n e a r l y i n A p r i l . S u b s e q u e n t m a t i n g s p r o b a b l y t a k e p l a c e a t a p o s t - p a r t u m o e s t r u s , a r i d u p t o f i v e l i t t e r s m a y b e b o r n b e f o r e m o s t o f t h e a d u l t s d i e i n J u l y a n d A u g u s t . T h e b r e e d i n g s e a s o n i s t e r m i n a t e d b y d e a t h o f t h e a d u l t s . T h e a v e r a g e l i t t e r s i z e b a s e d o n c o u n t s o f h e a l t h y e m b r y o s w a s 5.14, T w e n t y - t h r e e p e r -c e n t o f p r e g n a n t s h r e w s h a d o n e o r . m o r e e m b r y o s b e i n g r e s o r b e d . A v e r a g e l i t t e r s i z e d e c r e a s e s f r o m a p e a k o f 6 . 0 i n M a r c h t o 4 . 0 i n J u l y a n d A u g u s t . 8. T h e r e a r e t h r e e d i f f e r e n t p e l a g e s , a n d t w o r e g u l a r m o l t s . T h e s u m m e r j u v e n i l e p e l a g e i s l o s t i n a r e g u l a r m o l t i n O c t o b e r a n d N o v e m b e r , , a n d i s r e p l a c e d b y w i n t e r f u r . T h e s p r i n g m o l t d i f f e r s b o t h i n t i m e a n d i n m a n n e r b e t w e e n s e x e s . T h e f e m a l e s h a v e a t t a i n e d f u l l s u m m e r p e l a g e b y m i d - M a r c h b e f o r e t h e f i r s t y o u n g a r e b o r n . A n i r r e g u l a r m o l t i n m i d s u m m e r , i n w h i c h w o r n s u m m e r p e l a g e i s r e p l a c e d b y f r e s h s u m m e r p e l a g e , i s n o t i c e a b l e i n s o m e f e m a l e s . M o s t o f t h e m a l e s m o l t l a t e i n A p r i l , a l t h o u g h s o m e r e t a i n w i n t e r f u r w e l l o n i n t o t h e s u m m e r . T h e t w o s p e c i e s c a n n o t b e s e p a r a t e d o n t h e b a s i s o f p e l a g e . 9 . Q u a n t i t a t i v e m o r p h o l o g i c a l d i f f e r e n c e s b e t w e e n s e x e s a r e s l i g h t , a l t h o u g h t h e r e i s a t e n d e n c y f o r m a l e s t o b e l a r g e r t h a n f e m a l e s . T h e m o s t p r o n o u n c e d d i f f e r e n c e i s i n w e i g h t o f a d u l t s . - 6 1 -10. Adults are consistently larger than juveniles except i n length of the maxillary tooth row. The most marked differences are i n "body size and weight. The t a i l s do not increase i n length with age. 11. The number of t a i l vertebrae varies from 15 to 19. The two species can not be separated on this basis. 12. There i s no single morphological c h a r a c t e r i s t i c , or simple r a t i o of any two, which w i l l separate Sorex obscurus from S. vagrans i n the Point Grey population. An ar b i t r a r y separat-ion of 95 percent of the material was made on the basis of t a i l length and length of the maxillary tooth row.- When, the species were separated in this manner, S. obscurus was found to be s i g -n i f i c a n t l y larger than S. vagrans on the basis of a l l ten quant-i t a t i v e measurements made. 1 J . The two species of shrews i n Point Grey are probably hybridizing to a considerable extent. Breakdown of sexual and genetic bar r i e r s to interbreeding appears to be only p a r t i a l , as indicated by non-uniformity of the population and lower f e r t i l i t y and embryonic v i a b i l i t y . .14. Hybridization i n the l o c a l Point Grey population does not warrant changing the s p e c i f i c status of S. vagrans and S. obs-curus u n t i l further study determines whether or not i t occurs in other areas where the two species occur together. - 6 2 -LITERATURE CITED. B l a i r , W.F. C r i t e r i a for species and t h e i r subdivisions from the point of view of Genetics. Ann. N.Y. Acad. S c i . 44: 17 9-188. 1943. Brambell, F.W.R. Reproduction i n the common shrew. ( Sorex araneus Linnaeus ) . I. . The oestrus cycle of the female, I I . Seasonal changes i n the reproductive organs of the male. P h i l . Trans. Roy. Soc. London, Series B . 223: 1-62. 1935-Brambell, F.W.R. and H a l l , K. Reproduction i n the common shrew ( Sorex minutus Linnaeus ). Proc. Zool. Soc. London. II. 957-969. 1936. Cowan, I. McT. Mammals of Point Grey. Can. F i e l d - Nat. 44: 133-134. 1930. Cowan, I . McT. Insularity i n the genus So rex on the north coast of B r i t i s h Columbia. Proc. B i o l . Soc. Washington 34: 95-108. 1941. Dalquest, W.W. The molting of the wandering shrew. Journ. Mammal. _2_5: 146-151. 1944. Davis, W.B. The recent mammals of Idahol Caxton Pr i n t e r s , Caldwell, Idaho. 1939. Ha l l , E.R. C r i t e r i a f o r vertebrate species, subspecies and genera; the mammals. Ann. N.Y. Acad. S c i . 4£: 141-144. 1943. Ha l l , E.R. Intergradation versus hybridization i n ground sq u i r r e l s of the western United States. Amer. Mid-land Nat. 29: 375-378. 1943a. Hamilton, W.J. J r . The biology of the smoky shrew ( Sorex fumeus fumeus M i l l e r ). Zoologica 25: 473-492. 1940. Hubbs, C.L. Speciation of fi s h e s . Amer. Nat. 7_4: 198-211. 1940. Hubbs, CO. C r i t e r a f o r subspecies, species and genera, as determined by researches on fis h e s . Ann. N.Y. Acad. S c i . 44: 109-12.1. 1943. Jackson, H.H.T. A taxonomic review of the American lo n g - t a i l e d shrews. North Amer. Fauna No. 51: 1-238. 1928. - 6 3 -Johnsen, Sigurd. Utoer die seitendrusen der Soriciden. v a r l . Mitt., Anat. Anz. 46: 139-141. 1914. Pearson, O.P, Reproduction i n the shrew ( Blari n a brevicauda Say ) Amer. Journ. Anat. 73: 39-7JT 1944. r ~ Pearson, O.P. Longevity i n the sh o r t - t a i l e d shrew. Amer. Mid<-land Nat. 34: 531-546. 1945. Ridgway, R. Color standards and color nomenclature. Washington, D.C. Published by the author. i-9»*. APPENDIX I S t a t i s t i c a l tables for quantitative morphological features. STATISTICAL TABLES. S t a t i s t i c 1. Total Length Mean Range Standard Deviation Standard Error of Mean Coef f i c i e n t of V a r i a b i l i t y Number Adultjjm8Jb.es ' S. obscurus S. vagrans 119.55 114-128 1 3 . 6 1 * 0.571 3.01 40 108.74 102-116 *2.14 ^0.298 2.89 111 2. T a i l Length Mean Range S.D. S-E'm C.V. Number 50.54 45-56 ± 2.88 ±0.450 5.70 41 42.50 39-47 4- 2.17 ±0.202 5.H 115 Adult females Total S. obscurus S. vagrans Total Population Population 111.61 119.14 108.06 110.42 102-3128 110-12 8 99-116 99-128 ±5 - 7 9 ±4 . 1 9 ±3 . 19 ±5 . 6 9 it 0.471 t 0.988 ±0 .382 ±0 . 6 1 7 5.19 3.52 . 2 .90 5.15 151 18 67 85 44.55 50.26 42 .81 44.44 39-56 48-53 36-49 36-53 ±5.00 - * 1 . 8 6 * 2.22 ^3 . 7 6 * 0.400 * 0.427 ±.0.269 ±0.403 11.22 3.70 5.19 8.64 156 19 68 87 S t a t i s t i c Juvenile males Juvenile females S. obscurus S. vagrans Total S. obscurus S. vagrang Total To£al Length Population Population Mean 117.34 105.16 108.44 116.72 104 .54 106.52 Range 110-127 94-114 94-127 110-126 94-112 94-126 Standard Deviation + 3.36 ± 3 . 5 6 ± 6 . 4 9 ± 3 . 6 3 ±3.85 ± 5.91 Standard Error of Mean ± 0 . 4 7 5 ± 0.305 + 0.477 ± 0 . 6 7 3 ± 0 . 3 1 5 t0.444 C o e f f i c i e n t of V a r i a b i l i t y 2.86 3.39 5.98 3.11 3.68 5.55 Number 50 13(6 186 29 149 178 T a i l Length Mean • 50.52 43.18 ' 45.19 50.48 42 .72 43.97 Range 46-56 35-47 35-56 . 45-54 35-46 35-54 . s .§>, ± 2.51 * 2 . 14 * 3.97 ± 2 . 0 3 ± 2.02 ± 3 . 4 9 S.E. m + 0 .348 ±0.182 ±0.288 ±0.377 ± 0 . 1 6 4 ±0.259 C.V. 4.97 4 .96 8179 4.02 4.73 7.94 Number 52 13 8 190 29 152 181 Adult Males Adult females S. obscurus S. vagrans Total S. obscuruan S. vagrans Total Population Population 1-2.96 1 2 . 2 8 1 2 . 4 6 1 2 . 8 7 1 2 . 2 3 1 2 . 3 7 1 2 . 0 - 1 4 . 0 1 1 . 5 - 1 3 . 0 1 1 . 5 - W O 1 2 . 5 - 1 3 . 0 1 1 . 5 - 1 3 . 0 I I . 5 - I 3.O ± 0 . 4 7 + 0 . 3 9 + 0 . 5 1 + 0 . 2 3 ± 0 . 3 7 ± 0 . 4 3 + 0 . 0 7 3 ±0.036 ± 0 . 0 4 1 ± 0 . 0 5 3 ± 0 . 0 4 5 ± 0 . 0 4 6 3.60 3 . 1 8 4 . 1 0 1 . 7 5 3 . 0 4 3 . 5 1 4 1 116 157 1 9 6 8 87 t <|M 7 . 0 4 6.77 6 . 8 4 6 . 4 9 6.06 . 6 . 1 6 6 . 0 - 8 . 3 5 . 1 - 8 . 1 5 . 1 - 8 . 3 4 . 9 - 8 . 6 3 . 8 - 8 . 3 3 . 8 - 8 . 6 • 0 . 4 6 ± 0 . 5 8 ± 0 . 5 6 ± 1 . 1 9 * 1 . 0 9 A1 . 1 2 0 . 0 7 9 ± 0 . 0 5 7 S0 . Q 4 8 ± 0 . 2 8 1 ± 0 . 1 4 0 ± 0 . 1 2 6 6 . 4 9 8 . 5 1 8 . 2 0 1 8 . 3 3 1 7 . 9 9 1 8 . 1 8 34 1 0 4 1 3 8 18 61 79 S t a t i s t i c 3 . Hind Foot Juvenile males S. obscururs^ S. vagrans To t a l Popula t i o n Juvenile females S. obscurugs S. vagrans Total Population Mean 12.89 12.18 12.37 12.83 12.05 12.17 Range 12 .0-14 .0 11 .0-13.0 11.0-14.0 12 .0-13 .5 11.0-13. 5 11.0-13.5 Standard Deviation ± 0.42 ±0.40 i 0.52- + 0.38 ± 0.34 ± 0145 S.E. m ±0.059 t 0.034 ± 0.038 +• 0.070 ± 0.028 ±0 . 0 3 4 C.V, 3.29 3.33 4.20 . 3.00 2.84 3.71 Number 52 138 190 29 152 181 4. Weight 1 Mean 5.00 4.46 4.61 5.02 4.3$ 4.46 Range 4 . 2 - 5 . 8 3 .5-5 .7 3 . 5 - 5 . 8 4 . 4 - 5 . 8 3.1-5.7 3.1-5.8 S.D. ± 0.36 ±0.46 ± 0.50 ± 0 . 3 1 0.44 i 0.49 S.E. m + 0.053 ± 0.041 ^ 0 . 0 3 7 ±0.058 ±0.034 0 .038 C.V. 7.30 10.36 10.80 6.24 10.21 11.08 Number 48 128 176 29 137 166 S t a t i s t i c Adult males S. obscurus S. vagrans Total Populat ion Adult females S. obscurus S . vagrans To t a l Populat ion 5 . Condylobasal Length Mean 17.11 16 .64 16.75 17.09 16.32 16 .50 Range 16.5-17.7 16.0-17.1 T 6 . 0 - 1 7 . 7 16.7-17.7 15.6-16. 9 15.6-17.7 S.D. ±0.29 ± 0.25 ± 0.32 ± 0.25 ± 0 . 3 1 ± 0 . 4 4 S.E. m ± 0.056 ± 0.027 ± 0.037 ±-0.065 ± 0 . 0 4 3 ±0.054 c . v . 1 .68 1 . 4 8 1 . 9 4 1 .48 1 . 8 9 2.65 Number 27 86 113 15 51 66 6. Cranial Breadth Mean 8.77 8 . 5 9 ' 8.64 8.64 8 .30 8 . 3 9 Range 8 . 4 - 9 . 1 7 . 9 - 9 . 0 7 . 9 - 9 . 1 8 . 4 - 9 . 1 7 . 9 - 8 . 7 7 . 9 - 9 . 1 S.D. ± 0,19 ± 0.21 ± 0.22 ± 0.19 i 0,18 ± 0 . 2 4 S.E. m ± 0.035 +-0.023 ± 0.020 ± 0 . 0 4 5 1 0 . 0 2 5 ±0.029 C.V. 2.17 2.46 2.55 2.15 2.20 2 .SO Number 30 17 117 18 53 71 S t a t i s t i c 5. Condylobasal Length Mean Range S.D. S.E . • «m ? • Number 6 . Cranial Breadth Mean Range S.D. S, E , m Number luveni l e males Juvenile females S. obscurus S. vagrans Total S. obscurus S. vagrans Total Population Population 17.26 16.9-17 .6 + 0.21 ±0.036 1 .24 35 16.59 15.7-17.2. ± 0 . 2 8 ± 0.026 1.67 111 16 .75 15 .7 - 1 7 . 6 ± 0.39 ±0.032 2.#2 146 17.25 I 6 . 5 - I 7 . 7 ± 0.27 ±0.055 1.54 21 16.53 15 .8-17 .0 ± 0 . 2 4 1 0.022 1 .46 122 16 .64 15.8-17.7 ± 0 .34 + 0 .028 2 . 04 1*3 8 .79 8.51 8.59 8.77 8.34 8 .41 8 . 4 - 9 . 1 8 . 0 - 9 . 0 8 . 0 - 9 . 1 8 . 5 - 9 . 1 7 . 8 - 8 . 7 7 . 8 - 9 . 1 + 0 .20 ± 0 . 1 8 ± 0 . 2 2 t o . 1 6 ± 0 . 1 7 ± 0 .24 ± 0 .032 + 0 .018 £ 0 . 0 1 8 ± 0 . 0 3 3 ± 0 .016 ± 0 . 0 2 0 2.25 2.16 2.62 1.88 2 .01 2 .79 39 109 148 25 117 142 S t a t i s t i c Adult males Adult females S. obscurus S. vagrans Total S. obscurus S. vagrans Total Population Population 7. I n t e r o r b i t a l Breadth Mean 3.89 3.54 3.63 3.78 3.50 3.56 Range 3 . 6 - 4 . 1 3 . 3 - 3 . 8 3 , 3 - 4 . 1 3 . 6 - 4 . 0 3 . 3 - 3 . 8 3 . 3 - 4 . 0 S.D. ± 0 . 1 0 ± 0 . 1 2 * 0.19 ± 0 . 1 2 ± 0 . 1 1 + 0.16 S.E. m ±0.017 + 0.012 + 0.017 t 0.028 ±0.014 ± 0 . 0 1 8 c , v , 2.37 3.50 5.2.9 3-04 3.20 4.55 Number 34 99 .133 19 65 84 Maxillary breadth Mean 5.20 4.76 4.88 5.15 4.71 4.82 Range 4.9-5.4 4 . 4 - 5 . 0 4 . 4 - 5 . 4 4 . 9 - 5 . 4 4 . 3 - 5 . 0 4 . 3 - 5 . S.D • ± 0.14 ± 0.14 * 0.24 ± 0.17 ± 0.12 ± 0.23 S.E. m ± 0.024 i 0.014 t 0 . 0 2 1 ±0.039 + 0.016 ± 0 . 0 2 6 c . v . 2.77 2.88 4.96 3.20 2.51 4.69 Number 35 94 129 19 59 78 ,.fc-o S t a t i s t i c Juvenile males S. obscurus S. vagrans Total Population Juvenile females S. obscurus S. vagrans Total Population 7. I n t e r o r b i t a l Breadth Mean 3.78 3.46 3.54 3.72 3.40 3.45 Range 3 . 5 - 4 . 1 3 . 2 - 3 . 8 3.2-4 .1 3 . 5 - 3 . 9 3 .1-3 .7 3 . 1 - 3 . 9 S.D, + 0.13 + 0.10 ± 0.18 ± 0 , 1 0 ± 0.10 ± 0.16 S.E, m t 0 .020 ±0.009 ±0.014- ± 0.019 ±0.008 ± 0.012 cv. 3.49 2.86 5.03 2.63 2.92 4.49 Number 43 125 168 27 142 169 8. Maxillary Breadth Mean 5.06 4.67 4.77 5.01 4.71 4.76 Range 4 . 8 - 5 . 4 4 . 3 - 5 . 2 4 . 3 - 5 . 4 4 . 8 - 5 . 2 4 . 4 - 5 - 0 4 . 4 - 5 . 2 S.D, ±.0.13 ± 0 . 1 2 ±0.22 t 0.10 ± 0.10 ± 0 . 1 6 S.E. m t 0.020 ±0.010 + 0.017 ±.0.020 ± 0.009 ± 0.013 c.v. 2.61 2.66 4.51 2.08 2 .23 3.26 Number 43 i i 7 16 0 26 126 152 S t a t i s t i c Adult males Adult females S, obscurus S. vagrans Total S, obscurus S. vagrans Total Population Population 9. Maxillary Tooth Row Mean. 6.47 5.97 6.10 6.42 5.80 3.93 Range 6.1-6.7 5 . 6 - 6 . 2 5 .6-6 .7 6 .2-6 .7 5.5-6.1 5 .5-6-7 S.D, ± 0 . 1 6 ± 0 . 1 2 ± 0 . 2 6 ± 0 . 1 3 ± 0 . 1 4 ± 0 . 3 2 S.E. m ± 0.026 ± 0 . 0 1 2 ± 0.022 ± 0.030 • ± 0 . 0 1 7 + 0 . 0 3 4 C.V. 2.47 2.08 4.26 1.98 2.41 5.33 Number 37 103 140 19 65 84 i< -o ro I 10. P a l a t a l Length Mean 7.09 6.56 6.70 7.00 6.43 6.56 Range 6 . 6 - 7 . 4 6 . 2 - 6 . 9 6 . 3 - 7 . 4 6 . 8 - 7 . 4 6 .1 -6 .7 6 .1-7 .4 S.D. + 0 . 1 9 ± 0 . 1 3 i - 0 . 2 8 t 0 . 1 7 ± 0.14 4 0.28 . S.E i m ± 0.032 ± 0 . 0 1 3 ±0.024 ± 0.039 ± 0 . 0 1 7 ± 0.030 . C.V, 2.68 2.03 4.12 2.47 2.12 4.25 Number 36 101 137 1.9.. 65 84 S t a t i s t i c Juvenile mal.es Juvenile females S. obscurus S, vagrans Total S. obscurus S. vagrans Total Population Population 9, MaxLTlary Tooth Row 10 Mean 6.61 6.09 6.22 6.53 5.98 6.07 Range 6 . 4 - 6 . 9 5 .8-6 . 3 5 . 8 - 6 . 9 6 . 3 - 6 . 8 5.7-6 .2 5 .7-6.8 S.D, * 0.12 ± 0.12 ± 0.26 ±- 0.12 ± 0.12 ± 0.23 S.E. m ± 0 . 0 1 9 • ± 0.010 ± 0.020 ± 0.022 -t 0.010 vO .018 c . v , 1.54 1.92 4.10 1.76 1.92 3.86 Number 43 127 170 28 143 171 P a l a t a l Length. Mean 7.02 6.52 6..65 6.99 6.62 6.68 Range 6.8 -7 .3 6 . 2 - 6 . 8 6 .2-7 .3 6 .7-7 .2 6 . 3 -6 . 9 6 .3-7 . : S.D, ± 0.12 ± 0.11 ± 0 . 2 5 ±. 0.11 ± 0 . 1 3 4 0.18 S.E. m ± 0 . 0 1 9 ± 0.010 ± .0 .019 ± 0.021 + 0.011 ± 0 . 0 1 4 C.Vi 1.77 1.73 3.70 1.53 1.95 2.77 Number 43 125 168 27 143 170 APPENDIX II. Frequency d i s t r i b u t i o n histograms f o r quantitative morphological features. Plate I. Frequency d i s t r i b u t i o n of t o t a l length. • Sorex vagrans • Sorex obscurus Plate II.Frequency d i s t r i b u t i o n curves f o r t a i l length. • Sorex vagrans Sorex obscurus 1 40 male adults 45 SO n female adults XL male juveniles 35- 4 0 female juveniles •q-O AS Plate IV. Frequency d i s t r i b u t i o n of condylobasal length • Sorex vagrans • Sorex obscurus T I i . Plate V. Frequency d i s t r i b u t i o n of c r a n i a l breadth. O Sorex vagrans • Sorex obscurus Plate VI >, Frequency d i s t r i b u t i o n of i n t e r o r b i t a l breadth. • Sorex vagrans Sorex obscurus adults female f~| adults 3-S 4 . 0 male juveniles -3-0 •3-sr A.O female juveniles Plate VII, Frequency d i s t r i b u t i o n of maxillary breadth. • Sorex vagrans JQ Sorex obscurus Plate "VIII Frequency d i s t r i b u t i o n of length of the maxillary tooth row,. Q Sorex vagrans Sorex obscurus J 1 male adults female adults Ln s.s 60 «•«• J l male L-. juveniles^ £ 6.0 6s: 70 X female juveniles Plate IX. Frequency d i s t r i b u t i o n of p a l a t a l length. • Sorex vagrans Sorex obscurus male ' adults 6.5- 7.0 75" female adults 6 0 6-S 70 7.S-male juveniles female juveniles (>s 7.0 

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