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Adaptations to arid environments in Perognathus parvus (Peale) Iverson, Stuart Leroy 1967

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The  U n i v e r s i t y o f B r i t i s h Columbia  FACULTY OF GRADUATE STUDIES PROGRAMME OF THE .  FINAL ORAL.EXAMINATION . FOR THE DEGREE.OF DOCTOR OF PHILOSOPHY of STUART L. IVERSON  B . A . , St. Olaf. C o l l e g e , 1961 M„Ao,  U n i v e r s i t y o f North Dakota, 1963  MONDAY, MAY 8, 1967 AT 3:30 P.M. IN ROOM 3332, BIOLOGICAL SCIENCES BUILDING COMMITTEE IN CHARGE Chairman:  !,. McT. Cowan  V . C. B r i n k J . Mary T a y l o r D. M c P h a i l  P» A . Dehnel J o F„ B e h d e l l H.-'D. F i s h e r  E x t e r n a l Examiner: G. A . Bartholomew U n i v e r s i t y of C a l i f o r n i a Los A n g e l e s , C a l i f o r n i a Research S u p e r v i s o r :  H. D. F i s h e r  ADAPTATIONS TO ARID ENVIRONMENTS IN PEROGNATHUS PARVUS (PEALE) ABSTRACT  .  In the upper Sonoran and t r a n s i t i o n zone areas of southern B r i t i s h Columbia p o p u l a t i o n s of Perognathus parvus l i v i n g i n d i f f e r e n t h a b i t a t s e x i s t w i t h i n a few m i l e s of each o t h e r . The area was d e g l a c i a t e d about 10,000 y e a r s ago s e t t i n g a maximum time f o r occupancy by s m a l l mammals. T h i s study was i n i t i a t e d to compare the a d a p t a t i o n s of i n d i v i d u a l s of these p o p u l a t i o n s to the d i f f e r e n t h a b i t a t s and, i f p o s s i b l e , comment on t h e i r e v o l u t i o n and d i s t r i b u t i o n . Animals from an e n v i r o n m e n t a l g r a d i e n t were examined i n the f i e l d and laboratory. One end of the environmental continum (low area) was c h a r a c t e r i z e d by low r a i n f a l l , h i g h temperatures and a l o n g summer. The other (high area) by h i g h r a i n f a l l , low temperature's and a long w i n t e r . Specimens from k i l l t r a p p i n g i n d i c a t e d t h a t the s u b s p e c i e s under c o n s i d e r a t i o n was m o r p h o l o g i c a l l y v a r i a b l e , w i t h c h a r a c t e r i s t i c s d i s t r i b u t e d i n a-checkerboard p a t t e r n . A n a l y s i s of stomach c o n t e n t s i n d i c a t e d t h a t food d u r i n g the summer was about e q u a l l y d i v i d e d between seeds, green v e g e t a t i o n and animal m a t e r i a l . Seeds were the major i t e m s t o r e d f o r w i n t e r food. Low a r e a animals ate c o m p a r a t i v e l y more green v e g e t a t i o n , p o s s i b l y i n response to g r e a t e r water l o s s . Intensive l i v e t r a p p i n g and d i s s e c t i o n of specimens i n d i c a t e d t h a t h i g h a r e a females came i n t o r e p r o d u c t i v e c o n d i t i o n e a r l i e r i n the s p r i n g and ceased r e p r o d u c i n g e a r l i e r i n the summer, p r o d u c i n g fewer l i t t e r s than the low a r e a females, Young-of-year females i n the low area r e p r o duced w h i l e those i n the h i g h a r e a d i d not. Average l i t t e r s i z e s (4.85) were the same. There was no p o s t partum e s t r u s . Home ranges s i z e s of males (895 m^) i n the h i g h and low areas were the sameThe ranges of the females (656 m^) were s m a l l e r . Burrows and home range c e n t e r s were a p p a r e n t l y randomly d i s t r i b u t e d and ranges of both sexes overlapped. D e n s i t y was h i g h e s t i n the low a r e a and decreased w i t h a l t i t u d e . Long term surv i v a l r a t e s were h i g h i n a l l groups except low a r e a young animals. Short term s u r v i v a l r a t e s were h i g h e s t i n the w i n t e r , lowest i n the s p r i n g and i n t e r m e d i a t e i n the summer and f a l l . High a r e a animals e n t e r e d t o r p o r  e a r l i e r i n the f a l l than d i d low a r e a animals. Adults a p p a r e n t l y e n t e r e d t o r p o r b e f o r e young animals. In the l a b o r a t o r y animals tended to enter t o r p o r d u r i n g the dark p e r i o d and l e a v e t o r p o r d u r i n g the l i g h t p e r i o d a f t e r 3-168 (X = 46) hours i n t o r p o r . Percent of time spent i n t o r p o r i n c r e a s e d w i t h time at 5 C and l e v e l l e d o f f a t about 607». When m a i n t a i n e d a t low temperatures h i g h a r e a animals had s i g n i f i c a n t l y longer t o r p o r p e r i o d s and spent a g r e a t e r p r o p o r t i o n of time i n t o r p o r than d i d low a r e a animals. S u b j e c t i o n t o water s t r e s s i n d i c a t e d t h a t the low a r e a animals were b e t t e r a b l e to conserve water by r e a c t i n g more q u i c k l y to d e h y d r a t i o n . When dehydrated low area animals were a b l e to m a i n t a i n a low plasma osmotic c o n c e n t r a t i o n w h i l e h i g h a r e a animals were not. The p r o d u c t i o n of h i g h l y c o n c e n t r a t e d u r i n e appeared to be the main r e a c t i o n to d e h y d r a t i o n . F e c a l and e v a p o r a t i v e r a t e s of water l o s s were s i m i l a r to those found i n other s m a l l d e s e r t r o d e n t s and d i d not c o n s i s t e n t l y decrease w i t h d e h y d r a t i o n . Both h i g h and low a r e a animals m a i n t a i n e d t h e i r weight.on a dry d i e t at 767, h u m i d i t y at 20 C bu«- l o s t weight a t 42% humidity. It i s suggested t h a t the n o r t h e r n d i s t r i b u t i o n of P. parvus i s l i m i t e d by the s h o r t summer season a v a i l a b l e f o r b i r t h and e s t a b l i s h m e n t of the young. A n a l y s i s of morp h o l o g i c a l c h a r a c t e r s shows t h a t g e n e t i c d i f f e r e n c e s e x i s t between i n d i v i d u a l s of the two p o p u l a t i o n s . Conc r e t e evidence of g e n e t i c d i f f e r e n c e s i n p h y s i o l o g i c a l c h a r a c t e r i s t i c s i s l a c k i n g but a s t r o n g c i r c u m s t a n t i a l case f o r the e x i s t e n c e of such d i f f e r e n c e s can be b u i l t . I t i s suggested t h a t h i g h s e l e c t i o n p r e s s u r e s have been more r e s p o n s i b l e f o r the d i f f e r e n t i a t i o n of the p o p u l a t i o n s than has r e s t r i c t e d gene flow.  GRADUATE STUDIES I n v e r t e b r a t e Zoology  P. A. Dehnel  Vertebrate Physiology  N. Holmes  Ecology  D„ H.  Comparative  Physiology  Chitty  W„ S. Hoar  PUBLICATIONS I v e r s o n , S.L. and R. W. Seabloom. 1963. A r a p i d method f o r c l e a n i n g s m a l l mammal s k u l l s . Proc. N. Dak. Acad. S c i . 17: 101-103. H n a t i u k , J . and S.L. I v e r s o n . 1965. H a b i t a t d i s t r i b u t i o n and m o r p h o l o g i c a l v a r i a t i o n o f the deer mouse (Perdmyscus) . complex of Northwestern M i n n e s o t a and N o r t h e a s t e r n North Dakota. PrOc. N. Dak. Acad. S c i . 19:147-148. I v e r s o n , S.L., R.W. Seabloom and J . Hnatiuk. I n Press. S m a l l mammal d i s t r i b u t i o n s a c r o s s the p r a i r i e - f o r e s t t r a n s i t i o n of M i n n e s o t a and N o r t h Dakota. Amer. M i d i . Natur.  ADAPTATIONS TO ARID ENVIRONMENTS PEROGNATHUS  PARVUS  IN  (PEALE)  by  STUART LEROY IVERSON B.A;, S t M.A.,  0  Olaf College,  University  1961  o f North Dakota,  1963  A T H E S I S SUBMITTED I N P A R T I A L FULFILMENT O F THE  REQUIREMENTS  FOR T H E DEGREE O F  DOCTOR O F PHILOSOPHY  i n t h e Department of Zoology  We  accept t h i s  required  THE  thesis  as conforming t o t h e  standard  UNIVERSITY O F B R I T I S H April,  1967  COLUMBIA  In presenting  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements  f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y aval]able f o r reference and study,  I f u r t h e r agree that permission., f o r extensive copying of t h i s  t h e s i s f o r s c h o l a r l y purposes may be granted by the Head o f my Department or by h i s representatives.  I t i s understood that copying  or p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission.  Department of  ^?&o L O ^  The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Da't-e  JO /fly  /#7  i i  ABSTRACT  In t h e u p p e r Sonoran and Columbia populations within years was  a  few  ago  miles  setting  initiated  t o the  to  field  and  of  each o t h e r .  a maximum t i m e  h a b i t a t s and,  Animals  laboratory.  c h a r a c t e r i z e d by other  o f Perognathus parvus The  low  Specimens  from k i l l  environmental  low  trapping  in  pattern.  and  A n a l y s i s o f stomach c o n t e n t s  summer was  about  and  material.  Seeds were t h e major i t e m s t o r e d  area  animals  greater water l o s s . indicated that high the  s p r i n g and  litters  than  reproduced were the  e q u a l l y d i v i d e d between  ate comparatively  while  same.  Intensive l i v e area  ceased  the  low  females  area  (895  m  ) in the  (656  m  ) were s m a l l e r .  randomly d i s t r i b u t e d  females.  and  and  no low  i n the  area) the  winter.  subspecies  under  distributed  indicated  seeds,  was  green  that  food  vegetation  for winter  food.  Low  v e g e t a t i o n , p o s s i b l y i n response  t r a p p i n g and  earlier  i n the high  T h e r e was  a long  and  dissection  of  i n the  area  postpartum  d i d not. estrus.  areas were the  Burrows and  summer, p r o d u c i n g  Young-of-year females  same.  i n the  Average l i t t e r Home r a n g e s The  ranges o f both  low  sexes overlapped.  area  (4*85)  sizes  sizes  in  fewer  of  ranges o f the  home r a n g e c e n t e r s w e r e  to  specimens  came i n t o r e p r o d u c t i v e c o n d i t i o n e a r l i e r  reproducing  those  high  more g r e e n  (low  characteristics  during the animal  evolution  l o n g summer,  indicated that the  morphologically variable with  checkerboard  a  study  populations  examined  continum  and  temperatures  c o n s i d e r a t i o n was a  their  exist  10,000 This  of these  g r a d i e n t were  high temperatures  rainfall,  on  British  habitats  s m a l l mammals.  i f p o s s i b l e , comment  of the  high  in different  of individuals  One  o f southern  d e g l a c i a t e d about  f o r occupancy by  environmental  rainfall,  (high area) by  living  from an end  zone areas  a r e a was  compare t h e a d a p t a t i o n s  different  distribution.  transition  males females  apparently D e n s i t y was  highest  i i i  in  the  low  area  high  in  were  highest  summer  and  a l l groups  and  fall.  High  area .animals.  the  laboratory  of  during  time  spent  o  longer low  area  area  light  after  spent  and  evaporative  small  desert  Both high  high  appeared  rates  rodents  and  low  and d i d  humidity  at  northern  distribution  available characters  20  for  C but  birth  characteristics of  such differences  pressures lations  of  and  P  0  at  is  evidence a  can be built„  has  r e s t r i c t e d gene  maintain  noto  time  found  It the  It  is for 0  is  of  than  low  area  dehydration,.  osmotic highly  in  Fecal other  7&%  suggested that  the  diet  summer  Analysis  of  season morphological  individuals  differences  in  high  differentiation  of  the  physiological  circumstantial case for  the  about  at  short  suggested that  leave  dehydration,,  on a d r y  e x i s t between  genetic  strong  flow  t h e i r weight  o f t h e younge  of  at  the  dehydration,.  those  In  significantly  allow plasma  reaction to  did  Percent  in torpor  The p r o d u c t i o n  l i m i t e d by  differences  and  r e a c t i n g more q u i c k l y t o  humidity,,  1*2%  establishment  l a c k i n g but  of  the  animals.  period  had  rates  f a l l than  levelled off  animals  similar to  maintained  parvus  genetic  area  in  in torpor.  consistently decrease with  have been more r e s p o n s i b l e  than  main  l o s s were  not  animals  Concrete is  be t h e  lost weight  shows t h a t  two populations,.  to  dark  hours  5 C and  young  stress indicated that  able to  animals were  of water  area  at  the  were  survival  in the  before  = 46)  conserve water by  area  earlier  proportion  Subjection to water  area animals were  urine  (X  term  rates  intermediate  during  high  a greater  When d e h y d r a t e d  concentrated  torpor  3-168  able to  concentration while  and  entered torpor  enter  survival  Short  entered torpor  animals were b e t t e r low  spring  low temperatures  and  animals.  the  apparently to  Long t e r m  animals.  increased with time  at  periods  in  animals  period  in torpor  torpor  lowest  animals tended the  altitude.  low area young  Adults  When m a i n t a i n e d  60%  did  except  in the winter,  low  torpor  decreased with  the  existence  selection of  the  popu-  iv  TABLE OF CONTENTS page INTRODUCTION  1  . . . . . .  MATERIALS AND METHODS  . . . . . . . .  •  6  The Study A r e a «,<,<,.. . o o o o . o o o o . o . o e . o . GLACIAL GEOLOGY . . . . . . . . HISTORY CLIMATE o o o o o o o o o . o o o e o o o o o . o . o o PLANT ECOLOGY o . . » o o o . . o . o o o o o o o . . THE STUDY AREAS . o . . . . o o . . . . » ° » » » » . . O  6 6 7 8 8 12  o . o o o . . . . . . . . . . . . . » 0 0 . .  15 15 18 18  o . . . . .  20  MorphoXogy* o © o < 9 o o o o o o o o o o o * # « » » o o » © o METHODS C 0 0 0 0 0 0 0 9 0 0 0 0 0 0 t > 0 0 * 0 0 » 4 > * RESULTS AND DISCUSSION . . . . . o . . . . . . . . . . . CONCLUSIONS . . o o o o o o o o o o o o . 0 0 0 0 0 0 0  20 20 20 28  Food H a b i t s » o o o o o o o o o o o o o o o o o « o » . o o METHODS o o o o o o o o o o o o o o o o o . o o o o o o RESULTS"AND DISCUSSION . . . . . . . o .. . o . .. Animal M a t e r i a l 0 0 0 0 0 0 . 0 0 0 0 0 0 . 0 . o » Green V e g e t a t i o n o o o o o o . o o o o o o o o . o SeedS 0 . 0 0 0 0 0 0 0 0 0 0 0 . . . 0 0 0 . 0 0 0 CONCLUSIONS o o o o o o o o o o . o o o . o o o o o . o  28 29 30 30 31 36 38  Reproduction. 0 0 0 0 0 0 0 0 0 0 0 0 0 . . 0 . 0 . 0 0 0 0 0 METHODS o o o o o o o . o o o . o o o o o o o o . o o o RESULTS AND DISCUSSION . 0 0 0 0 0 0 0 0 0 . 0 0 . . . . Male 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Female 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 R e p r o d u c t i v e Season 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 CONCLUSIONS o o o o a o o o o o o o o o o o o o . o . o  38 39 41 4-1 41 43 47  Home Range Burrows o o o o METHODS 0 0 0 0 0 0 0 RESULTS AND DISCUSSION Home Range o o o  49 49 50 50  Methods o o o o o o o o o o o o o o o o o o o LITE-TRAPPING METHODS . . . . SNAP-TRAPPING METHODS . . . . . . . . . LABORATORY METHODS . . 0 . . . «• o « . o O  RESULTS AND DISCUSSION . . . o . . . o . . . o o o  o . . .  o . . .  0  o o . o o o . 0 0 0 0 0 0 0 . . » . o . . o o o o o o o  Burrows . o o . o o o . o o . . Territoriality o o o o o . . .  CONCLUSIONS  . 0 . o  . 0 . o  . . . o o o o o 0 0 0 . 0 0 0 0 . . . . . . . . . o . . o o o »  o o o o o . . . . » o o o o o o . . . .  o o o o o o o o o o o o o o o o o o o o o .  58 60  60  V  page Populat ions  0  RESULTS  0  0  0  0  0  0  0  0  0  0  0  0  0  0  O  O  O  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  O  0  0  0  0  0  „  »  9  0  0  0  0  0  9  0  0  0  0  0 c 0 0 'a 0 c * 0  0  9  0  0  0  0  0  0  0  0  0  0  72 73  AND D I S C U S S I O N  CONCLUSIONS  TOI*pOro  o  c  o  o  o  o  o  o  o  METHODS 0 0 0 0 0 0 R E S U L T S AND D I S C U S S I O N  .  .  .  o  o  o  o  0  0  0  O  O  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  O  O  0  0  0  0  0  0  .  0  0  0  0  O  0  0  0  0  0  0  0  0  e  0  0  0 0 0 0  O  O  0  0  0  0  0  0  .  .  .  0 0  0  Characteristics of  Torpor CONCLUSIONS Water  i n t h e Laboratory . „ 0 0' 0 0 c 0 0 »  Urinary Water Loss • • F e c a l Water Loss . <, Evaporative Water Loss F o o d I n t a k e <, o o o o o CONCLUSIONS. 0 0 0 0 0 0 0 0 0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  «  0  O  0  0  0  0  0  0  0  O  0  0  0  0  0  0  0  0  0  O  0  0  0 0 0  87  O  0  O  0  0  0  0  0  0  0  0  89 89  0  0  0  0  0  O  O  O  0  O  0  0  0  0  0  0  0  0  0  0  0 0 0  0 0  0  0  0  O  0  0  0  0  0  0  O  0  0  0  0  0  0  0  0  0  0  O  0  0  0  0  0  0  .0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  O  0  0  0  0  0  0  0 0  0  O  O  0  0  0 0  0  0  0  0  0  0  0 0  0  0  O  0  0 0  0  O  0  0  0  Adaptation 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 O O 0 0 A D A P T A T I O N "TO L A C K O F W A T E R 0 0 0 O 0 0 O O 0 0 Maximizing Water Intake 0 0 0 O O 0 O O 0 0 M i n i m i s i n g W a t e r L o s s 0 0 0 0 0 0 0 0 O 0 .0 Water and Reproduction 0 0 0 O '0 O 0 0 0 0 A D A P T A T I O N TO EXTREME AND V A R I A B L E TEMPERATURES 0  D i s t r i b u t ion© Evolut ion  0  0 0 0 0 0 0 0 0 0 0 0 0  0  CONCLUSIONS  0  LITERATURE CITED  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  109  112 112 .  112 133  0  0  0  134 118 118  0  0  0  0  0  0  0  118  0  O  0  0  0  0  0  O  0  0  0  0  0  0  O  0  O  0  0  0  0  0  119 119 120 121  0  0  0  0  0  0  O  0  O  0  O  0  0  O  0  O  0  0  0  0  0  0  0  122 122  0  0  0  0  0  0  0  0  O  O  O  O  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  O  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  «  O  0  O  O  O  0  0  0  0  0  0  123 125  0  P H Y S 3D X X X r l T MORPHOLOGY  104 104 107 109  0  0  0 0  91 91 102  0  0  0  H i g h Summer T e m p e r a t u r e 0 0 Low W i n t e r T e m p e r a t u r e „ 0 0 S h o r t Smtmer S e a s o n 0 0 0 0 0 Temperature and Reproduction  75 78 80 81  0  0  0  73 75  0  0  0  a  0  0  0  0 0 . 0 0  • o <> o 0  0 0 0 0  0 0 0 0  0  9  W e i g h t L o s s o o <, * « o Plasma Osmotic Pressures  9  0  Torpor  Balance * o o o e o » o o o METHODS 0 0 0 0 0 0 0 0 0 0 R E S U L T S AND D I S C U S S I O N . . ,  D ISCUSS3DN  61 61  o  Torpor i n t h e F i e l d „ o o The Y e a r l y Weight C y c l e The  61  0  METHODS  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  O  0  O  O  0  O  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  O  O  O  O  0  0  0  0  0  126  vi  LIST OF TABLES Table  page I  II  A summary of the characteristics of the study areas.  14  Periods of trapping in a l l areas. The X's represent two nights live trapping with 49 traps (98 trap nights) except in the home range areas where they represent continuous trapping with 48 traps The 0 s represent snap trapping of specimens for dissection.  17  Summary of measurements of adult males from different areas. Figures given are the mean, the standard error of the mean and the number in the sample.  24  Comparisons of adult males from different areas in the South Okanagan. The upper figure is the coefficient of difference. If joint nm-overlap is 90$ or greater figure is underline. Lower figure is t value. Significant (P - .05) values are indicated by . Numbers are the same as in Table III.  27  Percentage incidence of food materials in stomachs of animals in altitude, sex. and reproductive class"groups. indicates significant (P - .05) difference indicated by Chi^ teste indicates that Yates correction for continuity was used.  32  Percentage of total incidence contributed by each of the three classes ©f food materials. A l l sex and location classes are pooled.  33  Percentage incidence of materials in cheek pouches of a sample of mice. A l l sex and location classes are included. N = 99.  33  Nunbers of l i t t e r s per adult female per summer in high and low areas, 1964-1965°  45  Numbers of l i t t e r s per young-of-the-year female in high and low areas, 1964-1965°  45  Comparisons of embryo (Emb.) and placental scar (P.L.S.) counts between areas and comparisons between embryo and placental scar counts, 1965«  45  Summary of available reproduction data on P. parvus. Yes-no refers to whether author states that young are born that month. Question mark indicates conflicting evidence. Reported number per l i t t e r is also shown.  48  9  0  ITT  IV  s  V  3  c  VI  VII  VIII IX X  XI  v i i  XII  Distance between  original  capture  point  and  successive capture points., P r o p o r t i o n s shown f o r 20 m e t e r i n t e r v a l s o S i g n i f i c a n t ( P ^ ,05) Chi marked . 2  s  XIII  Home r a n g e  size  as determined  b y measurement  o f areas,,  2 XIV  Mean, v a r i a n c e a n d C h i of burrows t o a Poisson v a l u e s i s signifleant„ burrows a r e randomly di  2  XV  XVI  Numbers  Numbers  XX  XXI  o f animals  captured  o f animals  present  June,  Number 1964s  XTX  v  p e r day i n t h e c i r c l e  trap  0  from XVIII  0  Mean, v a r i a n c e and C h i v a l u e s f o r f i t t i n g d i s t r i b u t i o n o f home r a n g e c e n t e r s t o P©isson d i s t r i b u t i o n , , None o f the values i s significant. line  XVII  values f o r f i t t i n g distribution distribution Norte o f t h e C h i T h i s means t h a t t h e a n i m a l s stributed.  1964t o J u l y ,  i n t h e high  o f a n i m a l s known t o b e p r e s e n t , at different  and low areas  1965« middle  of  August,  altitudes.  Number o f y o u n g a n i m a l s p r o d u c e d p e r a r e a p e r y e a r i n high and low areas. The number, range a n d v a r i a n c e o f the reproductive data are given i n Tables VIII, IX, and X . Number o f a n i m a l s r e l e a s e d ( N ) a n d p r o p o r t i o n t o b e a l i v e one month l a t e r .  (P)  known  Long t e r m s u r v i v a l e x p r e s s e d a s t h e number known t o b e a l i v e / t h e number r e l e a s e d a n d t h e p r o p o r t i o n surviving each month ( p ) . C h i squares marked are significant, t h o s e marked were c a l c u l a t e d using Yates c o r r e c t i o n for continuity. 8  c  XXII  XXIII  T h e number o f new a d u l t s a n d t h e number permanently disappeared during t h e l a t e o f I964 i n t h e h i g h a n d l o w a r e a s . Length day  XXIV  of torpor  periods  periods,  f o r high  i n hours,  o f adults that summer a n d f a l l  during  and low animals.  s  different  10  indicates P -  .  E x p e r i m e n t a l g r o u p s , t r e a t m e n t s a n d numbers f o r b o t h s e t of experiments. The operations c a r r i e d out on days 1-10 apply only t o t h e second s e t o f experiments. Animals i n t h e f i r s t s e t were weighed d a i l y f o r 14 days.  v i i i  page XXV  Results  o f a 3-way a n a l y s i s  o r i g i n a l weight of animals  after  10  days  o f percentage o f  i n h i g h a n d low p o p u l a t i o n s  (A)5 d e p r i v e d o f and g i v e n water  76$  All  animals were f e d an excess o f p e a r l b a r l e y  relative  h u m i d i t y , (0)5  (B;j at  and  t o the humidity i n question XXVI  of variance  0  42$  a n d a t e r m p e r a t u r e o f 20  The b a s i c  N was  Co  equilibrated 12  94  0  C a l c u l a t e d F v a l u e s f o r a n a l y s e s o f v a r i a n c e c o n d u c t e d on r e s u l t s o f t h e second group o f experiments Degrees o f freedom i n t h e numerator e q u a l 1 except where n o t e d ( ) , D e g r e e s o f f r e e d o m i n t h e d e n o m i n a t o r e q u a l 36 i n t h e t w o w a y a n a l y s e s a n d 72 i n t h e t h r e e - w a y e x c e p t f o r p e r c e n t w e i g h t l o s s w h e r e t h e r e a r e 252 d e g r e e s o f f r e e d o m i n t h e denominator T h e number o f o b s e r v a t i o n s i n e a c h b a s i c g r o u p i s 10 (N = 10)o S i g n i f i c a n c e a t 05 i s shown b y 0  0  3  o  XXVII  Means a n d s t a n d a r d e r r o r the  second group  o f t h e means f o r t h e r e s u l t s  o f experimentso  0  100  of  N i n a l l c a s e s e q u a l s 10  o  101  ix  L I S T OF  FIGURES  Figure 1  page A  summary o f c l i m a t e a n d  the  2  A  5  extremes  of the  inside the  range are derived range  The  distribution  B.  The  location  from records  o f weather 10  parvus.  parvus  study  in British  Columbia. 13  areas.  C l i n e s o f m o r p h o l o g i c a l measurements a l o n g t h e bottoms o f t h e Thompson, a n d O k a n a g a n R i v e r V a l l e y s . '. T h e means a n d 95% c o n f i d e n c e i n t e r v a l s o f t h e means a r e shown. Distance along the abscissa i s p r o p o r t i o n a l t o the d i s t a n c e between t h e a r e a s where t h e samples were collected.  22  C l i n e s i n m e a s u r e m e n t s a c r o s s t h e s o u t h e r n end o f t h e Okanagan V a l l e y . Means a n d 95% c o n f i d e n c e i n t e r v a l s f o r t h e means a r e shown. Distance along the abscissa i s p r o p o r t i o n a l t o t h e east-west d i s t a n c e between t h e areas  Percent  free water areas  low  23  samples were c o l l e c t e d .  and  i n food materials c o l l e c t e d  i n August  are  1966.  Significant  i n d i c a t e d by  .  s  N  Percentages  1964  and  area  m a l e s , 1965.  A.  1965.  Percentages  Greatest  testis  high  .05)  i n a l l groups  o f l i v e - t r a p p e d males w i t h C.  i n the  (P ^  A. P e r c e n t a g e s o f m a l e s f r o m t h e h i g h and low sperm i n t h e d i s t a l p o r t i o n o f t h e e p i d i d y m i s ,  and  10.  o f P„  of the  10.  equals  areas  with  I965,  scrotal  length of high  34  testes, and  low 42  of high  w e r e p e r f o r a t e , (B).  9  o f P.  near  Climatic  11  A.  B.  8  Columbia.  August.  differences 7  p l a n t a s s o c i a t i o n s i n and  in British  D i u r n a l v a r i a t i o n i n mean t e m p e r a t u r e a n d p e r c e n t r e l a t i v e h u m i d i t y i n J u l y at Kamloops and C a r m i . Unconnected p o i n t s show means o f m e a s u r e m e n t s made i n t h e O k a n a g a n  where t h e 6  parvus  stations  in 3  r a n g e o f P.  and  low  pregnant,  1965.  l i y e - t r a p p e d females  and(CX  lactating,  that  1964  44  Home r a n g e s o f m a l e s a n d f e m a l e s i n h i g h a n d l o w a r e a s . T h e m i n i m u m n u m b e r o f c a p t u r e s u s e d t o d e t e r m i n e a home r a n g e was f i v e . The b l a c k d o t s r e p r e s e n t t r a p l o c a t i o n s . The  numbers o f a n i m a l s  low  areas  from June,  from data presented  present  I964  per  to July,  i n Table XVII.  area  I965.  i n the high  54  and  Smoothed b y  eye 62  X Figure 11  page Percent  o f a n i m a l s known t o b e a l i v e t h a t  1964  throughout 12  14  1965*  were  captured  o f l o w numbers.  79  Number o f 2 m i n u t e p e r i o d s p e r h o u r i n w h i c h a c t i v i t y t o o k place i n captive high and low area animals a f t e r different lengths o f exposure t o 5 C. T h e d a r k p e r i o d i s shown b y t h e horizontal bar.  16  17  A. Percentage o f time spent i n t o r p o r i n high and low area animals a f t e r different lengths o f time at 5 C. B. Mean length o f torpor period i n high and low area animals a f t e r d i f f e r e n t numbers o f t o r p o r p e r i o d s . The low area animals e n t e r e d t h e i r l o n g e s t p e r i o d o f t o r p o r o n d a y 1 8 . 6 (13-31) and t h e h i g h a r e a a n i m a l s entered t h e i r l o n g e s t p e r i o d o f t o r p o r o n d a y 1 8 . 4 (11-33)° Percentage o f o r i g i n a l weight a f t e r time i n animals from t h e h i g h and l o w a r e a s g i v e n d i f f e r e n t amounts o f w a t e r and exposed t o d i f f e r e n t h u m i d i t i e s .  84  86  93  Regression o f percent o f o r i g i n a l weight on time f o r high a n d l o w a r e a w a t e r - d e p r i v e d a n i m a l s a t 42 a n d 76$ humidity. C o n f i d e n c e i n t e r v a l s ( P - . 0 5 ) a r e s h o w n f o r t h e 76$ humidity slopes. Calculated t f o r t h e comparison o f high a n d l o w a r e a a n i m a l s a t l£% h u m i d i t y e q u a l s 0.0047 w i t h 71 degrees  18  82  T h e t o t a l number o f h i g h a n d l o w a r e a a n i m a l s t h a t entered and l e f t t o r p o r d u r i n g d i f f e r e n t hours o f t h e day d u r i n g a 40 d a y p e r i o d a t 5 C . T h e number o f a n i m a l s i n t h e n o r m a l p h o t o p e r i o d e x p e r i m e n t w a s 24. i n t h e delayed photoperiod e x p e r i m e n t i t w a s 12.  15  77  Mean w e i g h t s o f d i f f e r e n t a g e a n d s e x grotips o f a n i m a l s t h r o u g h o u t I964-I965. The l i n e i s f i t t e d by eye t o t h e mean o f m e a n s . Boxes enclose data which a r e suspect because  13  and  A. high B. The the the  o f freedom.  96  Percent o f o r i g i n a l weight remaining a f t e r time i n and low area animals, given and deprived o f water. Regressions o f percent o f o r i g i n a l weight on time. slopes o f t h e w a t e r - d e p r i v e d groups a r e d i f f e r e n t at .05 l e v e l ( t = 2.20, 136 d e g r e e s o f f r e e d o m ) , a s a r e s l o p e s o f t h e g r o u p s g i v e n w a t e r a t t h e .02 level  ( t = 2.42).  19  A. Mean p l a s m a o s m o t i c p r e s s u r e s , a n d ( B ) u r i n e / p l a s m a r a t i o s o f osmotic pressures o f high and low area animals deprived of and given water.  20  Mean u r i n e loss  concentrations  i n h3gh and l o w area  water.  and (B) d a i l y animals  given  urinary  99  water  and deprived  of 105  xi  Figure 21  A.  Mean p e r c e n t  water loss deprived  water  i n high  and  i n f e c e s , and low a r e a  (B) d a i l y  animals given  fecal and  o f water.  22  A. Water l o s t p e r ml o f oxygen used, (B) w a t e r l o s t p e r hour, and (C) m e t a b o l i c r a t e i n h i g h l a n d low a r e a a n i m a l s d e p r i v e d o f and g i v e n w a t e r .  23  A.  Free water  area water  i n t a k e i n food p e r day  animals deprived  i n t a k e i n l e t t u c e p e r day  control  animals.  i n high  o f and g i v e n w a t e r . i n high  and  B.  and low  low  Free area  x i i  ACKNOWLEDG-MENTS  I w i s h t o t h a n k my support of  a n d e n c o u r a g e m e n t made t h i s  r e s e a r c h was  Met.  evolved  0  F i s h e r , whose c o n s i s t e n t  study p o s s i b l e .  i n discussions with Dr. J . F  0  The o r i g i n a l  plan  Eisenberg.  Dr. I  Cowan, D r . D. C h i t t y a n d D r . P. A . D e h n e l p r o v i d e d  criticism. I  s u p e r v i s o r , D r . H. D  G. M. M c K a y h e l p e d w i t h  am g r a t e f u l t o a l l o f t h e s e  stimulating  people,  of this  study.  helpful 1965.  w o r k d u r i n g t h e summer o f  a n d t o my  discussions, h e l p f u l suggestions  throughout t h e course Alice.  field  extremely  0  fellow students, f o r  and c r i t i c a l  comments  I am a l s o v e r y g r a t e f u l t o my  wife,  INTRODUCTION  Studies of adaptations to arid have been conducted which has  along several l i n e s ,  this  one  b e e n t h e w o r k on w a t e r b a l a n c e .  examined kangaroo r a t s , animals  environments  can  Dipodomysa  survive without  possibles  concentrated  They p o s s e s s  urine,  and  w h i c h makes p o s s i b l e  a proposed  low  The  and  found t h a t  Is capable o f producing a  n a s a l counter-current heat  p u l m o n a r y w a t e r loss<>  t o c o n t r o l body temperature  adaptations  are probably also present  although a complete that  Perognathus  greater  They produce  (1955)  baileyl  of temperature  lost  not be  eremieus  significantly  tomillo.  less  regulation  low t e m p e r a t u r e s .  were t h e  a  (1961)  present  i n t ermedius  more t h a n  Dtpodomys  Lindeborg  (1952)  could survive  on a d i e t  of a i r -  e v a p o r a t i v e w a t e r p e r day  (1964)  o f "dormancy** I n P e r o g n a t h u s  first  suggests  significant.  o f r e s e a r c h has  Cade  (1965a)  Perognathus  observed  ( I 9 5 7 ) p  sp ^ 0  been the  and t o r p o r i n Perognathus.  Bartholomew and  Perognathus„  Dammann  musculus b u t  Schmidt-Nielsen  productive line  a condition  longlmembrls,  and  h i g h u r i n e c o n c e n t r a t i o n s i n "Perognathus  Another  described  Perognathus  Many o f t h e s e  evaporative water t o  :  low  evaporation of  Tucker  Chew a n d  e v a p o r a t i v e w a t e r t h a n Mus  Peromyscus leucopus and  conserve  arid m i c e .  Perognathus' p e n i c i l l a t u s  f o o d and  water less  rats  feces with  resorto  n o t b e e n made.  a l t h o u g h t h e d i f f e r e n c e s may  showed t h a t dried  less  has  as a l a s t  highly  exchanger  i n members o f t h e g e n u s  does not  laboratory  indicate that  (pooled) lose merflamlfl  examination  ealifornicus  extent than  data which  except  these  S e v e r a l a d a p t a t i o n s make  w a t e r c o n t e n t , and u t i l i z e b e h a v i o r a l means, r a t h e r t h a n water,  (1951)  Schmidt-Nielsens  free water.  a kidney which  rodents  o f t h e most p r o d u c t i v e o f  i n great d e t a i l  access t o  i n heteromyid  low  evaporative  o  investigations  Scheffer  ( 1 9 3 8 )  p a r v u s when e x p o s e d  working  than  with  t o measure t h e body temperatures  to  Perognathus o f pocket  mice  -2i n torporo record warming and cooling curves o f t o r p i d animals and describe the behavior associated with torporo other species o f Perognathus.  They have also observed torpor i n several  They concluded that i n P. longimembris hibernation  and aestivation were the same p h y s i o l o g i c a l phenomenon and used the word torpor t o describe both  0  Tucker (1962) described a d a i l y cycle of torpor i n Perognathus  c a l i f o r n i c u s and l a t e r (Tucker, 1965a,b) examined oxygen consumption, thermal conduction and heat exchange i n P. c a l i f o r n i c u s . Scheffer (1938) investigated the ecology o f P. parvus i n Washington and Oregon i n r e l a t i o n t o a g r i c u l t u r e  0  He found that i n the dry areas o f the  above states the pocket mice f a r outnumbered other species and subsisted primarily on seeds and green vegetation, which they stored i n t h e i r deep burrows.  He  found that each burrow was occupied by a single animal, except for females with l i t t e r s during t h e summer breeding season.  He states that the average l i t t e r  s i z e was about 5 and that the gestation period was from 21 t o 28 days.  Other  major ecological investigations o f pocket mice include those of Reynolds and Haskell (1949) on Perognathus p e n i c i l l a t u s and Perognathus b a i l e y i i n Arizona, Hibbard and Beer (i960) on Perognathus flavescens i n Minnesota and Dixon (1958) on the home ranges of Perognathus nelsoni i n Texas.  Eisenberg (I963) describes  the behavior of many of the heteromyidae and outlines the evolution o f behavior within the family.  Benson (1933) examined the relationship between pelage and  substrate coloration i n several species o f Perognathus. Although these studies have illuminated much of the physiology and l i f e history of members of the genus Perognathus  fl  none o f them has integrated  laboratory and f i e l d approaches t o several aspects o f the adaptive repertory at once, nor have they compared populations o f animals l i v i n g i n d i f f e r e n t environments. to  An integrative, comparative approach, however, has been taken  investigate aspects o f adaptation i n several small mammals. Murie (1961) examined the metabolic c h a r a c t e r i s t i c s o f mountain,  coastal and desert populations o f Peromyscus maniculatus and Peromyscus eremicus. He found pelage insulation and deep body temperatures were the same i n a l l  -3-  groups, but that the lowland P manlculatus had a higher metabolic rate than 0  the animals from the high altitudes.  He attributed this higher metabolic rate  to a more nervous temperament, which he hypothesizes is adaptive in chaparral habitat.  P. eremicus had a consistently lower metabolic rate than P.  manlculatus and resorted less readily to saliva-spreading as a method of evaporative cooling at high temperatures. with the desert habitat of P  0  He correlates these characteristics  eremicus.  Nevo and Amir (1964) compared reproductive and hibernation patterns in forest dormice (Dryomys nitedula) at the extreme southern edge of their range, in Israel, with the patterns shown by Eurasian populations.  They found  that the dormice were active throughout the year and bore two to three l i t t e r s per year between May and August in Israel, but the dormice in the northern areas were only active half a year and bore one to two l i t t e r s per. year.  They  suggest, ©n the basis of .preliminary observations, that these differences might be genetically determined. Fisler (1965) examined aspects of morphology, physiology, and ecology in Reithrodont omys megalotis. Reithrodont omys raviventris ravlventris and R o r. halicoetes in and around the salt marshes of San Francisco Bay.  He  suggests that raviventris and halicoetes arose from Megalot ia through isolation in marshes on islands sometime during the last 25,000 years.  He  found many differences between the groups, some of which were correlated with environment.  The marsh forms, raviventris and halicoetes» have developed a  partly diurnal activity period and placid temperaments and so are limited to the heavy ground cover of the marshes.  They have also developed an a b i l i t y  to tolerate salty drinking solutions with raviventris. which lives in the marshes with high salinity, able to tolerate water containing more salt, R. r. raviventris and R  0  r. halicoetes are presently isolated from each other  by a series of high h i l l s and are apparently evolving toward specific status.  The  only  isolating  factor  o p e r a t i n g b e t w e e n t h e m now  i s incomplete  mate  preference* Perognathus parvus Columbia presents approach t o  an  Perognathuso is  at  species only a  feet  extension  P.  examination  into  habitat.  forest.  comparative  environments  The  10,000  d r i e r than  the  results  The  at t h i s  and  i n two  different  Parvus  of  are  this  located  been a v a i l a b l e f o r  areas.  10,000  o f a maximum o f  species l i v i n g  altitude  f l o o r has  altitude  which  surrounding  even though t h e  the valley  higher  floor,  p o p u l a t i o n o f P.  a r e a has  years  of time,  into the  by  furthest penetration  Populations  floors.  f o r about  of the  Individuals of a  barriers  desert  represents the  fluctuated during that period  permits  integrative,  S o n o r a n d e s e r t , and  from the v a l l e y  a l w a y s b e e n warmer and  on  of the  grassland grading  parvus  British  are d i s t r i b u t e d throughout the v a l l e y  a l t i t u d e probably  miles  h a b i t a t i o n by has  animals  i n t o a c o o l moist few  Okanagan V a l l e y o f  a unique opportunity t o apply the  The  which are  4,500  southern  investigation of adaptation t o  a northward  hills,  i n the  probably  This  years  climate  of  situation selection  environments w i t h  no  apparent  to interbreeding. 1 Two  w h i c h may specific this  p o s s i b l e explanations  occur  ares  the populations  environmental  range, or t h e  different.  f a c t o r and  in this  environment  d e s c r i p t i v e and  w h i c h may  The  l a b o r a t o r y w o r k was  the  two  the  ranges o f t o l e r a n c e o f the The  simply  to  designed  to test  respond t o  operating  the  only not  may  be  in a different  populations  shows t h e  effect  genetically of  part  the  of  different.  individuals  c o n d i t i o n s and  so  s t a t e d as  follows.  of  determine  populations. be  a  h a v e become  s p e c i e s , much o f  capabilities  environmental  two  working hypothesis  o r may  populations  same r a n g e o f t o l e r a n c e t o  l a c k o f knowledge of t h i s  s t u d y was  on p o p u l a t i o n s  populations  are  have t h e  r a n g e s o f t o l e r a n c e o f t h e two  Because o f the  f i e l d work  f o r d i f f e r e n c e s between t h e  Populations  of  geologically environments, to  important  to  test  history  r e c e n t and will  g e o g r a p h i c a l l y c l o s e , but  evolve d i f f e r e n t  ranges  environmental variables.  t h e above' h y p o t h e s i s a n d a n d p h y s i o l o g y o f P.  The  subjected to  o f t o l e r a n c e and  modes o f  purposes  study have been  of this  gain a better understanding  parvus.  different  of the  reaction  natural  -6-  MATERIALS  The  The  Okanagan  Valley  ranges. River, there  The v a l l e y which  forms  is  quite  several  are wide benches  highly  arid-adapted  GLACIAL  Cordilleran  Pleistocene. Pinedale  ice  sheet  The  recession of  i c e was  extended  absent  of  latter  as  (Lodgepole the  ice.  the  more  et  In  sandy  the  ice  the  a l .  most  Monashee  and  valley  along  which have  In  mountain  contains  locations  alluvium,  be  During the  In  ponderosa terms  of  the  the  Okanagan  the  valley  developed  Wisconsin  glaciation  during  B.P.)  present soon  the  (1965)  of  pine)  in  after,  6,500  a  to  Washington.  4,500  As t h e  this  dominant  means  that  of  of the  Washington.  £ 310  B.P.  the  After  reaching B.P.  analysis  s p e c i e s was  c l i m a t e became  became t h e  years  found  after  late  Washington.  ameliorate,  He  shortly  lobe  12,000 of  covered  stage  Chelan,  and by  and  climate this  middle  of  Plateau  was  in the  Okanagan  a palynological  species  study  the  location  Columbia  between  grasses.  present  B r i t i s h Columbia,  climate continued  dominant  (Yellow the  of  Spokane,  amelioration  drought-resistant  Pinus  started  Heusser  the  of  state that  as t h e  dryness  Lake near  rest  16,000 years  vicinity  and  the  (1965)  south sheet  shown b y  to  during  glacier the  Liberty  pine)  and the  (about  from t h e  f a c t was of  Sheet  far  maximum w a r m t h  sediments  again  Ice  glaciation  recession of  peak  steep-sided  lakes. of  Cascade and  trending  flora.  Valley,  Richmond  the  the  large  and  north-south  GEOLOGY The Okanagan  by the  a generally  narrow  and  Area  between t h e  composed  fauna  METHODS  Study  is  s o u t h - c e n t r a l B r i t i s h Columbia  AND  Pinus  This  of  the  contorta  recession replaced  cooler  a  and  of by  moister  species. probably  around  10,000  -7years for  B P 0  the  0  southern  Perognathus.  Pseudosuga herbs and  and  menziezi  suitable  for  that  time  warmest  and  and  at  the  its  that  to  P.  habitats  not  of  for  that  the or  even warmer  cooler  to  the  ponderosa,  while  grass  and  of  able  to  upward  the  or  B.P.  do  and  6,500 to  near  entire  and  animal  Since  marginal  the  associations  4,500 years  the  areas  associated  northward  mice were  range  become  bunch  6,500  habitat  contorta, and  expand  and  P.  (aspen)  or  drier.  and w e t t e r  a desert-adapted  pine  pocket  and  s p e c i e s have  P.  of  support  were w e l l w i t h i n  areas were  range  tremuloids  area between  now  became m a r g i n a l  consisted of  continued  greatest  w i l l  menziezi  favorable  species  Columbia  time  Populus  similar to  c l i m a t e has become  shifting  f i r ) ,  Perognathus  driest  altitudinal  less  vegetation  Habitat  areas  marginal  the  B r i t i s h  reaching  present  BoPo  of  (Douglas  grasses,,  altitudinally, At  The  Okanagan  so,  the  now  4,500  northern  submarginal,  area  has  become  animal.  HISTORY  The phases. in  Prior  l i t t l e  1811  history  and  had  l i t t l e  1860 s ?  the  1860*s  the  reduced in  the  grazed  areas  the  valley  area.  the  Land for  of  valley  toward  palatable  bottom  available  the  the  the  bunch  less the  Project  of  more  effect  of  ungrazed grasses  desirable valley  (SoO.L.Po)  Irrigating  most  that  of  and  100 y e a r s areas  in  Purshina  192?  soley by  divided  Indians  prospected large  herds  on  who,  for of  engaging  In  cattle  were  Indian  reserve.  the  been  of  the  project  on t h e west  side  the  comparing  Tn t h e  grazed  greatly  increased.  arrival This  seen by  have  greatly  trading  gold.  can be  tridentata  four  Between  fur  grazing  canal.  benchland  into  ecological balance.  have  with  irrigation the  of  on t h e  spp.  can be  passed through  period,  settled  Artemsia  ended  on t h e  explored,  and  Valley  occupied  effect  was  end  became  The  areas with  and  Okanagan  Okanagan  agriculture,  late  the  the  v a l l e y was  and,  in  in  the  expeditions  grazed  man  1811  the  to  of  Ranching  South made  of  the  water Okanagan  -8-  River south of Oliver.  This land is now planted to orchards, as Is much of  the land on the east side of the river.  The only extensive tract of land in  the southern Okanagan Valley that is s t i l l in i t s original state is the Indian reserve land on the east side of Lake Osoyoos. CLIMATE Kendrew and Kerr (1955) state that because of the dissected nature of the land, and the lack of weather stations, only a very general summary of the climate of the South Okanagan and surrounding h i l l s can be made. They describe the climate as being mild continental with low precipitation and humidity.  Winter Is cold with snow in at least December and January, spring  and f a l l are warm and dry, and June is the month with most rain and clouds. There are no high altitude meteorlogical stations in the area of interest; the only ones which would be in the least comparable are those at Carmi and Princeton.  The Princeton station is at the proper altitude  but  is on a valley floor and so is not as comparable as desired. Carmi is located at some distance from the area of interest and is at a rather high altitude.  Therefore the high altitude stations w i l l be used only to infer  the direction  of change in climatological parameters, and to a limited  extent their values.  Plant associations w i l l also be used as indicators of  environment a l e ond it ions. PLANT ECOLOGY If Merriam*s l i f e zone concept is applied, the extreme southern ends of the Okanagan and Similkameen are included in the upper Sonoran zone, while the surrounding grasslands are classified as transition zone.  The  biotic areas of Cowan and Guiguet (1956) make a division, in this case similar to Merriam s, by placing the southern valley bottoms in the Osoyoos v  arid, and the surrounding areas in the dry forest biotic area.  More valuable  -9-  for our purposes i s the b i o c l i m a t i c zone c l a s s i f i c a t i o n of Krajina (1959, 1963)<> According t o Krajina the most a r i d areas compose the Ponderosa pinebunchgrass zone of the C o r d i l l e r a n cold steppe and savanna forest region, which i s replaced by the i n t e r i o r Douglas f i r zone of the Canadian C o r d i l l e r a n forest i n colder and wetter areas.  Some of the c h a r a c t e r i s t i c s o f the zones  and t h e i r subzones are shown i n Figure 1,  as w e l l as the range of climatic  conditions within which P. parvus i s known t o occur.  Pocket mice are found  throughout the Ponderosa pine zone and into the Douglas f i r zone but climatic conditions i n the extreme part of t h e i r range cannot be given because of the lack of high a l t i t u d e weather stations. Figure 2 shows the d i u r n a l v a r i a t i o n i n mean temperature and r e l a t i v e humidity i n July, when mean temperature and humidity reach t h e i r maximum values, at Kamloops and Carmi.  The Kamloops s t a t i o n was selected because i t  was not located near a lake and so should give a better idea of v a r i a t i o n on the benches high above lakes where the study area i s located.  The Carmi  s t a t i o n i s used because i t is'the most comparable of the highland stations. The unconnected points show four day averages f o r temperature and humidity two inches above the surface of the ground i n August 1966 high and low areas.  i n the  These averages are included only t o support the  a p p l i c a b i l i t y o f the long-term data used.  The short-term data follow a  s i m i l a r cycle and maintain s i m i l a r relationships when compared t o the longterm curves. During the period when the animals are active neither the humidity nor temperature are extreme.  The minimum average humidity during a c t i v i t y  i s about 40$, which i s determined from instruments 4 feet above the ground and so i s higher than at mouse l e v e l . i s 80 F.  The highest temperature during a c t i v i t y  Both sets of data show higher average humidities and lower average  temperatures i n the high area during periods when the animals are a c t i v e .  8 12-^  OJ  'M  001  :::::::•  I  i  JO!  :::::  CN1  .<»  : • • • ••  :::::::  A  :::::::  CO.  1  5  :  : <ii •«  Cowan And Guiguet ZONES  I Ponderosa Figure  iii  D i;i  43  34 co-  46  rs  •  P L A N T INDICATORS! [ A R E A S l f  Zone  1  A summary o f c l i m a t e P. parvus i n B r i t i s h d e r i v e d from records parvuso  70  :::::  Krajina  Pine  P  10  I!  :"S rS •  i  221  . .  !S:S  -2  ^1  :5 1  • «J  ol  CL  •  . . . . 139 • * « 1. ' • * • 0% • • "  Merriam  H2?  • IS  • ea  era  16l •1*  Douglas  Fir  Zone  P r e c i p . In.  Mean Annual T e m p . °F.  Mean Jan. Temp.°F.  Mean July T e m p . °F.  CLIMATE of  P. P a r v u s i n B. C.  and p l a n t a s s o c i a t i o n s i n and n e a r t h e range o f Columbia. C l i m a t i c extremes o f t h e range a r e o f w e a t h e r s t a t i o n s i n s i d e t h e r a n g e o f Po  No. F r o s t Free Days  Altitude 1,000 Ft.  100-1  HOO  80-  -80  60-  -60 s>s i  40-  •40  :  *  *  t  Hum. Temp. Low • O  20-  High A 3_  06*00  1200  1800  2?00  Hour Figure  2.  Diurnal variation July  i n mean t e m p e r a t u r e  a t Kamloops and C a n n l .  m e n t s made i n t h e O k a n a g a n  and percent  Unconnected i n August.  points  relative  humidity i n  show means o f m e a s u r e -  A  -20  -12-  Th i s effect can be noticed during the summer but i s more apparent i n the spring and f a l l .  My records show both frost and snowfall occurred about  one  month e a r l i e r i n the high area than i n the low area i n the f a l l s of I964 and  1965.  THE STUDY AREAS Within the south Okanagan, areas were selected f o r intensive study. The locations and c h a r a c t e r i s t i c s of these areas are shown i n Figure 3 and Table I.  An attempt was made t o establish study areas at both ends of the  e c o l o g i c a l spectrum inhabited by P. parvus i n Bo Co and also between these extremes. Areas 1,  2 and 13,  established near Osoyoos i n what appears t o be  the best development of desert-like conditions, sample one end of the spectrum. From now on t h i s group o f areas w i l l c o l l e c t i v e l y be c a l l e d the "low area'*. Area 1 was set up i n the Indian reserve and had not been subject t o grazing f o r many years.  It had a very good stand of Purshina t r i d e n t a t a and bunch-  grasses.  Area 13 was  similar.  Area 2 was  established immediately adjacent t o area 1 and was immediately across the reserve fence from areas 1 and  13 and was s i m i l a r except that i t had been subjected t o heavy grazing and much of the P. t r i d e n t a t a had been destroyed. Areas 3«  5 and 7? c o l l e c t i v e l y c a l l e d "high area", were located  near the summit of the Richter Pass Road, B. Co highway #3°  Because of the  dissected nature of the land they were not adjacent t o each other  0  They  were, however, a l l within 200 s of the same a l t i t u d e and had s i m i l a r s o i l s , vegetation and land-use p r a c t i c e s . was  The major difference among these areas  exposure (Table I ) . These areas were a l l within 100-200* o f the l o c a l  t r e e l i n e , representing nearly the maximum a l t i t u d i n a l range of the pocket mouse i n the Okanagan V a l l e y .  Because animals were scarce at the higher  a l t i t u d e s the major comparison i n t h i s study i s between these areas and the  121"  120"  Figure 3«  A. B.  119"  The d i s t r i b u t i o n o f P. parvus i n B r i t i s h Columbia. The l o c a t i o n of the study areas.  TABLE I.  Name  Ident i f i c a t ion Number Low home 1-13 range  A Summary of the Characteristics of the Study Areas  Altitude  Location  Exposure  1,000*  Okanagan Valley NE Osoyoos  West-southwest 5 - 1 0 ° slope  Low Area  High  -  The Highest Area  Grass Type  Soil  Land Use  P. tridentata A t rident ata C nauseosus Opuntia sp.  Bunch grass  Azonal sandy alluvium no rocks l i t t l e humus  None  e  2  1,000'  Okanagan Valley NE Osoyoos  West-southwest 5 - 1 0 ° slope  P. t r i d e n t a t a A. trideritata C nauseosus Opuntia sp„  Bunch grass  Azonal sandy alluvium no rocks l i t t l e humus  heavily grazed  3  2,400*  Okanagan Valley" Richter Pass NW Osoyoos  North-northeast 1 0 - 2 0 ° slope  A. f r i g i d a C nauseosus  sod forming  brown forest clay t i l l few rocks moderate humus  heavily grazed  Okanagan Valley Richter Pass NW Osoyoos  0 exposure 0 slope  A» f f i g i d a Co nauseosus  sod forming  brown forest clay t i l l few rocks moderate humus  heavily grazed  Okanagan Valley Richter Pass NW Osoyoos  North-facing 1 0 - 1 5 ° slope  A. f r i g i d a Co nauseosus  sod forming  brown forest clay t i l l few rocks moderate humus  heavily grazed  West 5-10°  A. f r i g i d a  sod forming  brown forest clay t i l l few rocks moderate humus  lightly grazed  A. f r i g i d a  sod forming  brown forest clay t i l l many rocks moderate humus  very lightly grazed  5  2,300*  Area  High. Home Range  Plant Indicators - Present  7  2,200*  9-12  3,400*  8  4,300*  Similkameen Valley SE Cawstpn Similkameen Valley SE Cawston  c  Opuntia sp.  slope  West 5-20° slope  -15-  low area.  A l l o f these areas had been heavily grazed, grasses were scarce  and stands o f Artemesia spp. were very heavy. Areas 9 and 12, the "high home range area**, were located on a high west-facing slope of Mt. Kobau overlooking the Similkameen V a l l e y and Cawston. The high home range area was s i m i l a r t o the high area except that i t had not been grazed as heavily. Area 8, the "highest area", was located at a higher a l t i t u d e on the same slope as the high home range area.  It was located just below t r e e l i n e  on the highest area of, grassland that could be found.  Artemesia spp. were  present i n low abundance, there were several rock outcroppings and P. parvus was scarce.  Methods  The prime r e q u i s i t e i n the selection o f areas was t o represent the entire e c o l o g i c a l spectrum present i n B r i t i s h Columbia as discussed earlier.  Areas were selected which were representative, accessible and  undisturbed. LIVE-TRAPPING METHODS Once an area was selected i t was measured out and a g r i d of traps consisting of seven rows o f seven traps per row was established. The distance between the rows and between the traps i n the row was 10 meters. Each trap l o c a t i o n was marked with a permanent numbered stake. range  The home  areas l a t e r established consisted o f nine rows o f 16 traps per row.  In a home range area a regular area made up traps 1-7 i n rows 1-7 and a new regular s i z e area made up traps 10-16 i n rows 1-7. Trapping was conducted with standard Longworth l i v e - t r a p s .  A  handful o f oats was placed i n the nestbox o f each trap and a few grains were  sprinkled outside the tunnel. The traps were set during the day, checked the next day shortly a f t e r dawn, and then either c o l l e c t e d or reset f o r the next night.  Trap-caused mortality was very low.  An area was trapped three nights  the f i r s t time but the standard period of trapping was two nights. Tn home range trapping 48 traps were used t o cover the entire area. :  Traps were set at every t h i r d stake and moved forward one stake each time they were checked. etc.  Tn other words traps would be set at positions 1-1, 1-4, 1-7  on the f i r s t night, and 1-2, 1-5, 1-8 etc. on the second night.  fourth night the traps would be back i n t h e i r o r i g i n a l locations.  On the,  Home range  trapping was conducted for many nights i n a row, the exact dates are given i n the section ori home range.  The times o f trapping are shown i n Table I I .  The animals were marked on t h e i r f i r s t capture by c l i p p i n g no more than two toes per foot with a small, sharp s c i s s o r s . from medial t o l a t e r a l , was 1, 2, 4 and 7.  The value of toes,  The l e f t hind foot indicated  u n i t s , t h e right hind foot 10»s, the l e f t front foot 100»s, and the right front foot 1000's. On each capture the number, l o c a t i o n , weight, age and reproductive condition o f the animal were recorded* nearest gram with a small spring scale.  The animals were weighed t o the Reproductive condition o f the males  was indicated by the l o c a t i o n of the t e s t e s .  Reproductively a c t i v e males  had s c r o t a l testes (TS) while non-reproductive animals had inguinal or abdominal testes (TA).  Non-reproductive females had no opening t o the vaginal  canal (Imp.) while reproductive females had an opening (P).  Middle t o l a t e  pregnancy (Pg.) i n females could be detected by v i s u a l observation and palpation.  Milk could be expressed from the nipples o f l a c t a t i n g (Lact.)  females. Age was recorded as either young-of-the-year (TOT) or adult (A). Because o f the seasonal nature of reproduction young animals were captured  TABLE I X ,  Week  Periods of trapping i n a l l areas. The X ' s r e p r e s e n t t w o n i g h t s l i v e t r a p p i n g w i t h 49 t r a p s (98 t r a p n i g h t s ) , . e x c e p t i n t h e home r a n g e a r e a s w h e r e t h e y r e p r e s e n t c o n t i n u o u s t r a p p i n g With 48 t r a p s . T h e 0«s r e p r e s e n t snap t r a p p i n g o f specimens f o r d i s s e c t i o n .  May  June  July  Aug.  Sept.  Oct.  Nov.  April  May  June  July]  1234  1234  1234  1234  1234  1234  1234  1234  1234  1234  1234  1234  X XX  X X  X X  X  X  X  X X  X X  X  X  XX  X X  X X  X  X  XX  X X X  X  X  1  X X  X  X X  X  X  X  2  X X  X  X X  X  X  X  X  Aug.  Low  13 Area  000  Specimens Low HR  3  XX  X  X  X  X  X  High  5  XX  X  X  X  X  X  Area  7  XX  X  X  X  X  X  Highest  Area  9  X  X  X  X  X  HR  8  X  X  X  X  X  X  X  X X  0  0  0  X  X  X X  X  X  X  X  X  X X  X  X  X  0  0  0  0  Specimens  High Home Range  X  0  XXX  X X  XXX  X  X  X  0 X  X  X  X  -18-  only from l a t e June t o November.  They were recognized by a number of  c h a r a c t e r i s t i c s including pelage c o l o r , weight, and c o l o r o f the i n c i s o r s . Young animals had greyish fine pelage, smaller size and l i g h t e r orange i n c i s o r s . It was easy t o recognize young animals u n t i l October, when many had molted i n t o adult pelage and reached adult s i z e . l a t e f a l l were undoubtedly made.  A few mistakes i n aging during the  The proportion would be low, however, because  by then most o f the animals had been marked.  SNAP-TRAPPING METHODS Animals were snap-trapped f o r specimens f o r both the morphological study and the study o f reproductive condition and stomach contents.  Standard  V i c t o r break-back mouse traps were used, baited with whole grain oats.. Traps were set about 20 meters apart i n a l i n e and l e f t f o r as many nights as necessary.  The number of traps per l i n e and the exact locations o f the l i n e s  were variable.  Specimens f o r d i s s e c t i o n were trapped near the high and low  areas (Figure 3)«  The locations and times of trapping specimens f o r study  skins are shown i n Figure 3 and Table I I . A c i r c l e o f snap traps (Table I I , Figure 3) s i m i l a r t o that used by Calhoun (1963) was established.  The basic configuration was two concentric  c i r c l e s cub by two diameters at r i g h t angles t o each other.  The diameter o f  the outer c i r c l e was 325 meters and the diameter o f the inner c i r c l e was 162 meters.  Traps were set 5 meters apart on the diameters and c i r c l e s and were  checked and rebaited each morning. ins  The traps, a t o t a l o f 270 were d i s t r i b u t e d  outer c i r c l e , 205, inner c i r c l e , 40, diameters, 26.  LABORATORY METHODS Animals used i n the laboratory were trapped near the high and low study areas (Figure 3) with t h e methods and traps described e a r l i e r .  In the  laboratory they were maintained i n d i v i d u a l l y i n glass-sided t e r r a r i a 40x25 cm  -19-  with walls 20 cm higho screen  0  The tops of the t e r r a r i a were covered with welded wire  The cages were bedded with coarse sawdust about 6 cm deep  c  A finger-  bowl f i l l e d with Okanagan s o i l was placed i n each terrarium t o allow the animal t o maintain i t s pelage  0  The animals were fed an abundance of sunflower seeds and m i l l e t weekly and lettuce twice weekly.  No water b o t t l e s were usedo  The animal room was a  windowless room used only t o maintain a colony of P. parvus.  The animals were  maintained on a 16 hour day with the l i g h t s coming on at 0900 and going o f f at 0100 PSTo  The temperature was maintained at 20 C i 2 C and the r e l a t i v e  humidity fluctuated between 50 and 80$. Under these conditions animals were maintained i n the laboratory f o r as much as two years i n very good condition.  The laboratory mortality rate  was low and the animals developed no gross abnormal behavior p a t t e r n s t o t a l number of animals used in the laboratory phase of the study was  0  The 154°  -20-  RESULTS AND DISCUSS3DN  Morphology  Morphological v a r i a t i o n o f P. parvus i n the Okanagan was  examined  because morphology i s one of the most e a s i l y quantified and often used indicators of differences between populations.  Many observed  morphological  changes are not of any obvious adaptive s i g n i f i c a n c e , but the amount of difference between populations, or the d i s t r i b u t i o n of differences among populations, provide an index t o possible evolutionary relationships between the populations.  METHODS As many specimens as possible were assembled f o r examination. Specimens examined from B r i t i s h Columbia were %  Osoyoos ( 8 9 ) , Keremeos (10),  Okanagan ( 2 8 ) , Midway ( l ) , Vaseaux F a l l s ( l ) , Richter Pass (16), Vaseaux Lake (15), Vernon (44)» Okanagan Landing (21), Ashcroft ( L 4 ) o Twelve specimens from O r o v i l l e , Washington were a l s o examined. Measurements used f o r analysis were the standard t o t a l , t a i l and foot lengths; the maximum width of the i n t e r p a r i e t a l , minimum inter-orbital width and the condylobasilar length.  The l a s t three measurements were taken with a  d i a l v e r n i e r c a l i p e r t© the nearest 0.1 nou  Only those measurements taken  from adult male animals were used i n the s t a t i s t i c a l a n a l y s i s . Animals were c l a s s i f i e d as adult or sub-adult  on the basis of pelage.  Those of  questionable age were not included.  RESULTS AND DISCUSSION The d i s t r i b u t i o n of P. parvus i n B r i t i s h Columbia (Figure 3 ) i s nearly l i m i t e d t o the Okanagan and Thompson r i v e r v a l l e y s .  The animals occur  -21-  in  v a l l e y bottoms and a r e d i s t r i b u t e d  data were analyzed t o permit south  i nthe valley  floor,  o f mice  Variations to Oroville length,  mice  i n t h e south.  of the variation  i n t h e south.  from n o r t h t o  no smooth c l i n e s  III).  With  from A s h c r o f t  the exception o f condylobasilar  o f characters are evident.  In four o f t h e five  from Osoyoos and O r o v i l l e were l a r g e s t .  These  are not significant  i n some c a s e s b u t i n d i c a t e  a t r e n d f o rsouthern  t o be l a r g e r .  the exception o f the cline  i n condylobasilar  the tendency be  valley  F i g u r e 3 shows t h e l o c a t i o n s  i n m o r p h o l o g i c a l c h a r a c t e r s measured  ( F i g u r e 4, T a b l e  With  The  analyzed. occur  measurements a n i m a l s  an examination  sides  and a l s o t o examine t h e d i f f e r e n c e between  bottom and h i g h e r a l t i t u d e o f t h e groups  up t h e v a l l e y  f o r Osoyoos and O r o v i l l e  animals t o be l a r g e s t ,  differences animals  l e n g t h and  no patterns can  seen. Figure  Valley  5 ( T a b l e I I I ) shows t h e v a r i a t i o n  i n t h e Osoyoos a r e a .  The Osoyoos animals  largest  i n a l l measurements except  animals  i n a l l cases, except  animals  i n t h e Vernon t h a n t h e Osoyoos Interparietal width  i n t h e A n a r c h i s t sample. calculated  f o ri n t e r p a r i e t a l width,  animals being  i s great  animals  i n Richter  a r e taken  i n t o account  that  t h e Osoyoos-Oroville animals  foot  and c o n d y l o b a s i l a r l e n g t h s .  area  and h i g h and v a r i a b l e  i n theRichter  and A n a r c h i s t animals  T h e same s i t u a t i o n  ratio i s  animals.  Most  are not s i g n i f i -  t r e n d s t o one group  of  a p p l i e s when t h e V e r n o n  a r e compared t o t h e R i c h t e r and A n a r c h i s t a n i m a l s .  comparisons  The high  When t h e i n t e r p a r i e t a l / c o n d y l o b a s i l a r  or smaller.  are the  a r e more s i m i l a r t o t h e  animals  o f F i g u r e 5 shows n o c o n s i s t e n t  larger  comparison  sample.  h i g h e s t v a l u e s a r e once a g a i n found  and i n s p e c t i o n  i n this  f o r i n t e r p a r i e t a l width.  o f t h e d i f f e r e n c e s between t h e R i c h t e r cant  a c r o s s t h e Okanagan  When a l l  the only generalization that have t h e c o n s i s t e n t l y  largest  appear i s total,  tail,  Figure  4«  Glines  o f m o r p h o l o g i c a l measurements a l o n g  Thompson fidence abscissa  and Okanagan R i v e r intervals  Valleys.  o f t h e means a r e shown.  i s proportional t o the distance  where t h e samples were  collected.  t h e bottoms o f t h e  T h e means a n d 95$ Distance  con-  along  the  between t h e a r e a s  -23-  Osoyoos  Richter  Anarchist  Vernon •  200  Osoyoos Vernon i  5.6  I.P.  Total 180  5.2  -  4.8  ~  -I  -  160  -i  4.4  140  -i  28  G.B.  100  80  25  26  -  24  -  -•  22  -  - i  23  -  IE.  Foot  G.B.  23  21  5°  21  -  19  _  -  -I  17  i Figure  1 *  r  J  r -1 50  i  T  shown. west  Means a n d 95$ Distance  confidence  1  Miles  C l i n e s i n measurements a c r o s s t h e s o u t h e r n Valley.  1  intervals  along the abscissa  r "I5 0  end o f t h e Okanagan f o r t h e means a r e  i s proportional t o the east-  d i s t a n c e between t h e a r e a s where t h e samples were collected„  TABLE IIXo  Summary given the  Total Kamloops  176.0 ±  3*6  Okanagan Landing  175*1 * 11  4*2  Osoyoos  184*4 30  1  4*0  184*1  1  Oroville  11.9  7 Anarchist  Richter Pass  23.1  172.0 ± 11  8.0  166.8  5*8  ± 7  90.0  94*5  92.3  *  0.86  7  7  173o3 ± 22  Vernon  Figures  e r r o r o f t h e mean a n d t h e n u m b e r i n  Interparietal  Foot  97*1 ± 10.1  7  males from d i f f e r e n t areas.  sample.  Tail  14*7  o f measurements o f a d u l t  a r e t h e mean, t h e s t a n d a r d  i 22  2.2  * 11  7*1  23.1  22.4  i 22  0.27  11  ± 1*01  30  24*1  23*6 i  8 7 * 7 ± 3*2 11  22.5 ±  88*4 * 7  23.1  5*3  0.53  7 0.45  11  i 7  0*33  5*9 * 0*15 7  24*3 *  0.04  24*2 ±  4*6 ±  5*9 ± 0.12 9  24*6 t  6*0 ± 0*02  25*4 ±  0.21  5.0 ± 28  0*03  23  27  0*94  20.3  * 0.98 22  0*90  18.7  ± 0.92 9  1*57  19*6  26  25*2 ±  5*2 ± 0.11  5*9 ± 0*06 10  24*7  0*07  2*3  19*9  6  0.93  ±  2.98  6 0*62  20*9  0.51  23*1  8  24*3 ±  t 25  6 ±  2.89  ±  7  9  6.0 ± 0*49 7  5*9 * 7  19*5  22  5*1 ± 0*57 7  5*6 ± 0*4 5  2*54  TP CB  7  5*9 *  9 0*84  Condylobasilar  4*9 ± 0.02 22  9  ± 0.28 30  9 6 . 1 ± 9.4 7  ±  7  1.4  ±  4*7  Interorbital  i 0*55 8  i 5  0.55  -25-  Bergman's r u l e , which states that, i n a species of homeothermic animal, subspecies which exist i n the cooler part of the species range tend to be larger than those l i v i n g i n the warmer part, appears t o be generally v a l i d f o r both a l t i t u d i n a l and l a t i t u d i n a l changes (summarized by Mayr, 1963)0 Burrowing mammals, however, almost consistently f a i l t o obey Bergman*s r u l e (Mayr, I963), but react t o the amount of food available i n winter (Davis, 1938 f o r Thomomys and Stein, 1951  f o r Talpa),  The observed body s i z e of  Po parvus i n the Okanagan runs counter t o Bergman's r u l e and may be a reaction t o the amount of food a v a i l a b l e as with the animals discussed aboveo Races i n c o o l , moist areas are usually darker than those l i v i n g i n warm dry climateSo  This i s known as Gloger's rule and holds t r u e i n the  populations of P „ parvus i n the Okanagan (Cowan and Guiguet, 1956)  c  Mayr  (1963) states that t h i s effect cannot be ascribed t o substrate-adapted cryptic coloration because i t i s shown i n nocturnal and arboreal animalso Benson (1933) however, examined the coloration of a v a r i e t y of rodents l i v i n g on the white gypsum sands and black lava flows of the Tularosa basin of New Mexico, and concluded that the colors observed were due t o s e l e c t i o n for  cryptic c o l o r a t i o n rather than an effect of climate.  He bases h i s con-  c l u s i o n on the fact that he could f i n d l i t t l e climatic difference between the areas but that, even at night, the differences i n v i s i b i l i t y of the d i f f e r e n t l y colored animals were apparent„ Dipodomys ordi  fl  Setzer (1949), i n examining the subspecies of  concluded that i n t h i s species the color was correlated with  the color of the s o i l rather than the amount of moistureo  It appears that i n  heteromyids, and possible desert rodents i n general, color may more often be determined by s o i l color than amount o f moisture.  The color observed i n Po  parvus i n the Okanagan cannot be ascribed t o either cause because the c o l o r of the s o i l and the amount of moisture are p o s i t i v e l y correlated. H a l f of the comparisons between areas are s t a t i s t i c a l l y s i g n i f i c a n t  -26at the .05 l e v e l (Table I V ) populations,  0  S i g n i f i c a n t differences are t o be expected between  but the finding that the differences were s i g n i f i c a n t i n h a l f o f  the comparisons made, p a r t i c u l a r l y when the compared areas are close together geographically,  implies a s u r p r i s i n g l y high amount o f v a r i a b i l i t y .  A better  idea of the magnitude o f the observed differences can be gained by comparing them t o the usual l e v e l of difference needed t o name a subspecies. The c r i t e r i o n selected f o r comparison was the 75$ r u l e put into numerical form by Mayr, Linsley and Usinger (1953)° t o mean 90$ j o i n t non-overlap.  This r u l e was defined  The point of i n t e r s e c t i o n between the two  curves can be calculated by d i v i d i n g the difference between the means by the sum o f the standard deviations. e f f i c i e n t of d i f f e r e n c e .  The resultant figure i s c a l l e d the co-  A c o e f f i c i e n t o f difference o f 1.28 equals j o i n t  non-overlap o f 90$ arid i s the conventional l e v e l o f subspecific difference. A figure below 1.28 means a j o i n t non-overlap o f l e s s than 90$ and i n s u f f i c i e n t difference f o r naming o f subspecies, while a figure above 1.28 indicates a d i f f e r e n c e great enough f o r subspecies t o be namedo Table IV shows the calculated c o e f f i c i e n t s o f difference and S t u d e n t ^ s t values f o r comparison between animals from Anarchist, Vernon and Osoyoos.  No differences large enough t o suggest the existence  of two subspecies were found among the Osoyoos, Anarchist lations.  Richter,  and Vernon popu-  The Richter animals have a high c o e f f i c i e n t o f difference when  compared t o a l l other populations on the basis o f interparietal/condylob a s i l a r r a t i o and from Osoyoos and Vernon when compared on the basis o f i n t e r p a r i e t a l width. Mayr (1963) points out that common and widespread species are more v a r i a b l e than r e s t r i c t e d or rare ones.  He goes on t o say that the greater  v a r i a b i l i t y permits these animals t o become widespread, thus allowing them t o store more v a r i a b i l i t y and so on i n a mutually r e i n f o r c i n g reaction.  Thus  -27-  TABLE TV.  Comparisons o f adult males from d i f f e r e n t areas i n the South Okanagan. The upper figure i s the c o e f f i c i e n t o f differenceo I f joint non-overlap i s 90% or greater figure i s underlined» Lower figure i s t value.. S i g n i f i c a n t (P - .05) values are indicated by . Numbers are the same as i n Table I I I . s  Anarchist X Osoyoos  Total  Tail  Foot  Interparietal  Ihterorbital  .54  .62  1.09  .19  1.06  .45  5.9  .751  5.5  2.17  s  Condylobasilar  IP CB  .72 4.20  3.1  12.3  Anarchist  .34  .07  .38  .70  0  .30  1.98  X Richter  14.9  .89  1.56  1.27  0  1.10  13.8  Anarchist  .06  o 22  .41  .51  0  .27  .33  X Vernon  o36  3.28  .74  2.38  0  1.20  1.44  Vernon  .57  .14  0  8*1  0  .06  I.76  X Richter  2.02  .66  0  2.71  0  .72  5.2  Vernon  .58  .28  .69  .83  1.01  .64  .31  X Osoyoos  35.5  1.94  4.8  .55  .46  5.18  .46  .60  2VL  .76  .85  .40  3.21  Richter X Osoyoos  s  1.26 10.1  3  s  s  2.73  s  S  3.0  s  s  s  s  s  3.08  s  s  s  s  £  £  s  1.60  2.19 s  6.52  !  -28-  the observed v a r i a b i l i t y may be part o f the reason that the animal has been able t o exist i n the v a r i a b l e habitat o f the south Okanagan  0  The presence of many large differences, i n one case large enough t o be subspecific, between populations  geographically close, indicates that  e i t h e r gene flow has been r e s t r i c t e d or s e l e c t i o n pressures have been  higho  Except f o r the Okanagan r i v e r , and now the i r r i g a t e d orchards, no b a r r i e r s are apparent.  The presence o f differences between areas on the same side o f  the r i v e r indicate that r e s t r i c t e d gene flow alone does not explain the observed v a r i a t i o n .  The s i t u a t i o n can possibly best be summarized by  stating that the observed differences exemplify the r e s u l t s o f high s e l e c t i v e pressure on the members o f a variable species. CONCLUSIONS 1. observed.  Bergman's r u l e i s not followed i n the v a r i a t i o n o f specimens  Gloger^s r u l e i s followed, although the v a r i a t i o n i n pelage  c o l o r a t i o n may be due t o the color o f the substrate rather than c l i m a t i c conditions per se. 2.  The populations were highly v a r i a b l e i n the characters  studied.  The v a r i a t i o n was found t o be d i s t r i b u t e d i n a checkerboard rather than c l i n a l pattern.  On the basis o f the observed v a r i a b i l i t y and the d i s t r i b u t i o n of  the v a r i a b i l i t y It i s suggested that population gene frequencies are changing r a p i d l y i n response t o high, l o c a l , s e l e c t i v e pressures.  Food Habits  The i n v e s t i g a t i o n o f food habits i s important not only because o f the basic ecological information i t y i e l d s but also because, i n t h i s species, water taken i n with food may represent the t o t a l water intake.  I f a popu-  -29-  lation  i s In an  proportion with  the  of  environment where w a t e r l o s s  food with  expenditure  high water content  of less  energy than  i s great,  might  intake of a  balance  greater  the water budget  r e s t r i c t i n g water  loss.  METHODS The  stomachs were e x c i s e d , p l a c e d  s c o p e , and  opened w i t h  upper h a l f  of the  the  f o o d mass.  The  f o o d mass was content  one  the  midline  be  then  of the  v e g e t a t i v e m a t e r i a l and  masticated in  along  stomach c o u l d t h e n  Possible seeds,  a cut  i n water under a d i s s e c t i n g of the  s t o m a c h s was  animal  of the  stomach.  material.  Vegetative  even though w e l l masticated,  The  i n small pieces  and  cated  o f t e n complete heads, l e g s o r antennae c o u l d be Two  particular  i t s green c o l o r .  i f present,  m a t e r i a l c o u l d be  i t occurred  separate  stomach.  whether a class  of  One food  of these,  a  score  given.  The  indication  present. given and  The  class  o f 3>  occupying  Scores  the  that  class  the  absent  was  the  occupying  o f which were?  For  mostly  and  the  least  contents  well  of  a of  I f the  under  class  absent  a  " i m p o r t a n c e " and  o f 1.  masti-  a reflection  classes of  food  Any  was  materials stomach  a rating class  of  was  of  2,  food  0.  summed a n d  example,  because,  recognized.  second g r e a t e s t  of  mass  retained i t s  g r e a t e s t volume o f t h e  a rating  seed,  normally  recognized  I f i t was  called  volume a r a t i n g  given  0  given.  different  i n each c l a s s were t h e n  greatest possible score  contents  of the  least  or absent.  r a t i n g was  food m a t e r i a l occupying  m a t e r i a l s w h i c h was  of the  o f one was  other  of the proportions  a rating  the  score  present  simply  categories;  formed a  m a t e r i a l was  "incidence",was  m a t e r i a l s was  present  an  animal  r a t i n g s were used t o d e s c r i b e t h e  c o n s i d e r a t i o n was o f z e r o was  The  noted.  seeds were  structure and  often  contents  The  disturbing  divided into three  i n t o a p a s t e - l i k e consistency, which,  part  greater curvature.  r e f l e c t e d back without examined and  micro-  converted  i f class x  to a  contained  some v e g e t a t i v e a n d  no  percentage one  animal  stomach, materials  -30-  the  incidence  animal  class would  data were  importance were they were  giving highly  examined  subjective  heads,  and leaves  and  determined.  and low areas.  The barley  RESULTS  sampled dried  Seheffer  incidence and  coefficient  .616,  =  p -  indicated  .001).  by using  and herbs,  On t h i s  only t h e  content.  g o f pearled  content  barley  a t 100  of  o f seeds was  wasplaced  a t a depth  seed  and low areas  The effect  on t h e  o f 1 meter  allowed t o equilibrate  f o r 24  ripe  from t h e high  on t h e moisture  determinations.  hours  r  grasses  of water  sample b u r i e d was  (  collected  f o r moisture  classical  (1938),  captured  i n California  f o r this  studies burrows,  found that contained  (1954)  i nthe  f o r eight  days  A l l samples were weighed  when  C and reweighed.  of the diet  food  t h e pouches  are "strictly  o f 14  i n opinion  habits  as based  that  vegetarian".  20  of  contained  i s illustrated by  specimens  animal  may l i e i n t h e f a c t on contents  on t h e contents  o f 9 o f t h e 20  material.  o f Perognathus  who reported  Jameson reported  animal  they  t h e stomachs  difference  reported while  view  who s t a t e s that  changed b y Jameson  reason  250  both  Material  The  1  and  66$  AND D I S C U S S I O N S  Animal  He  Approximately and another  then  were  and humidity  of the soil  collected,  was  100$,  incidence.  f o r t h e determination  1966,  that  and presentation  of representative  and grasshoppers  underground temperature  surface  analysis  of t h e predictors,  andbeetles  August  high  vegetative  A correlation  significantly correlated  least  Stems  and i t appeared  t h e same r e s u l t s .  i t was decided t o simplify  also  vegetative  100$,  s c o r e w o u l d b e s e e d 100$,  basis  in  b e seed  0$. The  that  for this  The importance  0$.  animal  score  animals  o f cheek  o f both  that  view  o f P.  material.  parvus The  the earlier  pouches and  pouches  contained  This  and stomachs.  seeds,  while  only  -31-  Table V stomachs  77$  and  shows t h a t  in a l l locations  The  a n i m a l s no type  and  that  o f animal food  7  insect  material  consisted  probably from beetles. larvae  areas.  make up  significant  Animal material  the  diet.  the  time they are  and  growth takes p l a c e  important  The been can  impact  investigated.  shows  12  states that  highly  concentrated  urine,  animal matter  and  states that of the found  and  a diet  Since  e a t e n may  diet  P.  o f P.  arthropod  2  and  of  the  beetles,  of animal  i n high constant  and  low  part  which  of most  reproduction  eaten appears t o provide  food  material  animals during  time during  Haines  an  6). on t h e w a t e r b a l a n c e h a s (1964)  state the  o f meat a l o n e w i t h o u t  t o p o s i t i v e water  not  Onychomys  producing  parvus produces a h i g h l y  contribute  a  concentrated  balance.  Vegetation Occurrence of vegetative  been reported  by  both  Scheffer  material  (1938)  and  VII)  hispidus.  amount  a relatively  (Figure  protein  Schmidt-Nielsen  urine.  grasshoppers,  i n the  i s the  water  In  appendages, which were  or between animals  This  VI  occurrences of u n i d e n t i f i a b l e  p r o b a b l y used by  high  on  My  scleritinized  animal material  of this  maintain water balance  Green  analysis  a p p e a r s t o make up  above ground.  (Table  only  of animals  source of p r o t e i n  i n cheek pouches  found  Many o f t h e  and  diet.  he  v a r i a t i o n was  and  of the  (1954)  (1937)  It i s a v a i l a b l e t o  Table  exclusively  a regular part  different classes  the  incidence  c l a s s groups.  proportion  found  an  in  e a t e n a p p e a r s t o be  of heavily  Blair  materials  of unidentifiable insect material  complete mole c r i c k e t s .  eaten by  significant  Jameson  nearly  No  a  food  reproductive  t h e s e were mostly c a t e r p i l l a r s .  occurrences of c a t e r p i l l a r s .  pupae and  and  of  A n i m a l m a t e r i a l has  a n i m a l m a t e r i a l was  probably p r i m a r i l y insecto  insects  incidence  o f animals.  a n i m a l m a t e r i a l makes up  s a m p l e o f 99  and  percentage  of different classes  b e t w e e n 33$  a  shows t h e  i n the  Hall  d i e t o f P.  (1946).  Their  parvus reports  has and  of  0  -32-  T A B L E Vo  Percentage animals 3  by  Indicates Chi  incidence  in altitude,  area  ( P - .05)  class  difference  indicates that Yates  of  groups.  Indicated  correction for  used.  All  All  males  females  TA  TS  males  males  64  64  51  s  77  83  86  79  85  s  88  44  48  50  48  47  53  10©  198  181  117  89  92  Lact. females  P females  Vegetation  45  Seeds  82  Animal  N  Low  c  In stomachs  s e x , arid r e p r o d u c t i v e  significant  test.  c o n t i n u i t y was  High area  o f food m a t e r i a l s  s  IMP females  P. females  PG females  P females  Vegetation  48  s  78  22°  78  79  78  Seeds  66  c  95  55  95  81  95  Animal  33  49  77  49  42  49  N-  39  41  9  41  28  41  c  -33-  T A B L E VI.  P e r c e n t a g e o f t o t a l i n c i d e n c e c o n t r i b u t e d b y each o f t h e t h r e e c l a s s e s o f food m a t e r i a l s . A l l sex and l o c a t i o n c l a s s e s a r e p o o l e d .  April  May  June  July  August  Sept.  Mean  Vegetation  41  38  28  26  28  27  31  Seeds  37  40  44  45  53  43  43  Animal  21  22  28  29  , 19  30  26  N  34  83  48  43  56  34  298  TABLE VII.  P e r c e n t a g e i n c i d e n c e o f m a t e r i a l s i n cheek pouches o f a sample o f m i c e . A l l s e x and l o c a t i o n c l a s s e s are included. N = 99°  Bait  Seeds  Green  Animal  Fecal  vegetation Absolute incidence  85  39  6  0  1  86  39  6  0  1  Percentage incidence  80  60-  Percent Free Water 40-  20-  o->  Herbs t=0.17  Figure 6.  Grass t=2.39  Seeds a  t=0.76  Insects t=0.63  Seeds On Surface t=1.49  Percent free water In food materials collected In the high and low areas In August 1966. S i g n i f i c a n t (P - .05) differences are indicated by „ N i n a l l groups equalss  10.  Seeds Buried t=3.12  S  Low • High •  -35-  the  results  of this  green succulent  study  v e g e t a t i o n such as  I have observed had  b e e n gnawed b y  were found traps.  i n one  The  stems cut  a significant  is  apparently  not  m a t e r i a l was  More m a l e s w i t h  -  40$)  i n 6$  i n one  stomachs t h a n  during  o f seeds.  April  and  May  high  The  most  obvious  months i n t h e  area.  Since these  stress  o f p r o v i d i n g energy f o r the  urine,  they  water  summer f o o d  by  loss.  any  Okanagan and  animals  of the  great  perforate  roots  live-  grass  i t makes  animals  but  extent. and  dried  females have  animals,  short  than  i n those  i n low  would be  low  area  appear t o have m i n i m i z e d t h e e a t i n g more s u c c u l e n t  reflect  i n the  captured as  from  and  May  of a highly  to  high  are the  at  of  June  compared  i s much d r i e r t h a n  amount  an  stomachs  correlate with  u n d e r some w a t e r s t r e s s , production  lactating  T h e s e same g r o u p s  animals  April  area  vegetative  diet.  environmental  the  and  T h e s e d i f f e r e n c e s may  of vegetative material i s aridity.  driest  necessary  of the  a change In  It i s a l s o higher  animals.  in  material i n that  p e r f o r a t e females.  t h r o u g h September.  incidence  mostly  incidence of vegetative material i s higher  captured  which  Macerated  i n c h e e k p o u c h e s was  o f t h e pouches sampled  incidences than  intake rather than  area  parvus.  found  non-reproductive  increase  animals  P.  leaves  o f rhizome have been  s c r o t a l t e s t e s and  Incidences  The  probably  spp.)  burrow.  a l s o have h i g h e r i n food  (Opuntia  In pouches o r s t o r e d t o  found  found  females have h i g h e r  stems.  m a t e r i a l i s s i m i l a r t o animal  carried  in their  or  length.  p r o p o r t i o n (25  o f grass were  material  lengths  v e g e t a t i v e m a t e r i a l found  up  leaves  fleshy p r i c k l y pear  stomach and  Vegetative  stems  grass  mouse-sized rodents,  t o a convenient  Vegetative  indicate that vegetative material i s primarily  two  the  least  high the  concentrated  o f p h y s i o l o g i c a l work  v e g e t a t i o n when i n s i t u a t i o n s  of  greater  -36-  Vegetative as  seeds  (Figure 6)  leaves, which contain  by  area  so p r o v i d e s  appear t o be  The  partially low  and  significantly  (Figure 6 ) . may  m a t e r i a l c o n t a i n s two  the  main  a good  source  source  o f green  more f r e e w a t e r  amount  account  o f water  for the  t o three times  i n the  available  o f water.  high  much f r e e Grass  vegetation  than  i n the  g r e a t e r amount  as  i n the  grasses  water  stems  and  eaten, low  i n the  area low  of vegetative material  area eaten  animals.  Seeds In agreement w i t h t h e seeds  are the  most  important  many s t o m a c h s a s  any  in  or  cheek pouches  the  only  available  No  a t t e m p t was  Blair  seeds  ( 1 9 3 8 ) and  Blair  amount from  contained  o f food present  25  greater  t o 300  cc.  The  i n 39$  percentage  T h i s may  or  show a c h a n g e  i t may  The  reflect  an  i n about t w i c e food  o f seeds  varied  l a r g e seeds the  species of  o f t h e pouch i n 83$  most  from  carried i t is  by  the  i n cheek the  mice  very  small  o f some o f t h e available  samples,  by  grasses.  seeds. P.  parvus,  o f a l l stomach  sexes than  in  in a l l 5 of  samples.  late is  July,  the  The 1964,  varied  significantly  non-reproductive  i n c r e a s e i n energy requirements  p r o p o r t i o n o f seeds  found  seeds u t i l i z e d  i n c i d e n c e o f seeds  of  as  Pj_ h i s p i d u s .  of both  i n amount  item  Because o f t h i s  i n e a c h b u r r o w when e x c a v a t e d ,  i n r e p r o d u c t i v e animals  animals.  to the  s p e c i e s used by  and  Perognathus,  abundance o f seeds c o l l e c t e d  (1946) l i s t  food,  only  of  feeding.  the types  hispidus utilizes  Seeds were p r e s e n t burrows which  are the  S i z e o f seeds u t i l i z e d  P.  diet  i n burrows.  identify  o f some h e r b s  Hall  (1937) l i s t s  extent  correlate  of the  Seeds are p r e s e n t  f o o d m a t e r i a l and  made t o  or t o  (1937) states that  Scheffer and  1 mm)  item.  f o r daytime or w i n t e r  abundance o f p l a n t s .  (less, than  food  s t o r e d t o any  food  pouches o r burrows with  other  c l a s s i c a l view  o f the  animals  activity.  i n the  diet  o f P.  parvus  increases toward  -37-  the  end  of the  availability  summer,,  of  s e e d s and  Naturally is  l e s s t h a n any  of  seeds  buried the  other  pearl barley surface  naturally w a t e r as  on  fecal material  in  4  of the  (1939), rat  trapping  gnawed  Schweigert Rabbits by  bacterial  (1948)  feces  provide  and  both  i n the  much  free  high  area  contained  (1949)  that the  fecal  report  pouch, to  he  dry  food  a  that of  the  examined.  floridanus examined.  season,  alacer Miller  found kangaroo  shortage  baileyi  It i s necessary  material.  of  salvage  vitamins  Glcese,  Pearson  rabbits  Is high  a d d i t i o n a l r i b o f l a v i n because o f the feces.  source of vitamins  feed  Dipodomys s p e c t a b i l i s  intestine.  of  i n one  c h e e k p o u c h e s o f 6$  of Sylvilagus  fecal material  reingestion a  as  Perognathus b a i l e y i they  reassimilate  on  for  these animals  Haskell  in the  of the  days  exposed  stomach, and  reassimilate fecal material to  grow w e l l w i t h o u t  may  occurred  content  area.  suggests that because of  action  eight  that  nearly  This  water  After  i n the  i n one  R e y n o l d s and  fecal pellets  showed t h a t  cecal absorption  low  Horn, Texas, d u r i n g  f o r these kangaroo r a t s t o  produced by  i n the  seeds  of Perognathus h i s p i d u s  He  The  same r e l a t i o n s h i p i s t r u e  Buried  i n pouches o f a l l four  A n i m a l s may  6).  i n a b u r r o w , show t h a t  none o f t h e  n e a r Van  which he,captured.  (Figure  contain  greater  free water.  much f r e e w a t e r a s  fecal material  o f unnamed o r i g i n  18 b u r r o w s  20$  i n burrows.  s e e d s may  material.  fecal material.  reports  droppings  stored  feces  Perognathus p r i c e i but  (1937)  t w i c e as I f the  appearance of  o f gnawed r a b b i t  Blair  6).  material  of  winter.  about  only  storage  more w a t e r t h a n t h o s e  The  extent  food  t o a combination  approaching  seeds c o n t a i n  contained  seeds,  due  for the  however, by  fresh vegetative  significantly  small  storage  class of  (Figure  occurring  i s probably  occuring  i s increased,  soil  and  This  and  In t h e an  pocket  emergency  and in  riboflavin.  amount  mouse food  gained  reingested supply.  -38-  CONCLUSIDNS lc area  animals  The p r o p o r t i o n o f d i f f e r e n t 1/4  were about  seeds.  2/5  v e g e t a t i v e m a t e r i a l a n d 2/5 2.  i n low a r e a  not c a r r i e d  b u r r o w s , b u t made up a s i g n i f i c a n t  stored and  Vegetative  i n burrows.  25  -  4. the  highest  i n burrows  55$  f o r night  and  may  at least  and w i n t e r  Grasses  exposed  and b u r i e d  i n t h e low  partially,  item  o f summer f o o d  material,  o f P. p a r v u s o  i n cheek pouches o r  p r o p o r t i o n o f t h e summer t o provide water.  i n the diet  feeding.  emergency  Buried  on t h e s o i l seeds  food  It  o f P. p a r v u s .  They had  item c a r r i e d  seeds contained  and s t o r e d twice  as  surface.  i n the high  area  contained  significantly  area.  Fecal material occurred  represent  animal  i n cheek pouches o r s t o r e d i n  i n stomachs and were t h e o n l y  much f r e e w a t e r a s t h o s e  6.  m a t e r i a l , and  free water.  incidences  more w a t e r t h a n  w e r e 1/5  a l s o not c a r r i e d  I t made up a s i g n i f i c a n t  Seeds were t h e main  5.  proportion  m a t e r i a l was  appeared t o be eaten,  contained  animals  animal  seed.  A n i m a l m a t e r i a l was  3.  i n t h e stomachs o f h i g h  v e g e t a t i v e m a t e r i a l , 1/4  1/2  The p r o p o r t i o n s  materials  food  o c c a s i o n a l l y i n stomachs and b u r r o w s  o r a supply  o f vitamins,  particularly  riboflavin.  Reproduct i o n  Reproduction an  animal's  inclement  life  c y c l e a n d may b e a l i m i t i n g  environments.  correlated with Nevo and Amir,  i s one o f t h e more c o m p l e x a n d s t r e s s f u l p h a s e s o f  The p e r i o d s  i n the colonization of  o f r e p r o d u c t i o n h a v e b e e n shown t o b e  t h e more " f a v o r a b l e " p e r i o d s  I964)  factor  a n d s o may p r o v i d e  o f the year  (Prakash,  i960  and  a key t o comparison o f t h e s e v e r i t y  -39-  of d i f f e r e n t stresses acting on the population. Data on the number of offspring produced per year are important for the analysis of populations and provide a measure of the p r o d u c t i v i t y of an area.  METHODS Data presented i n t h i s section were obtained from snap-trapped and live-trapped specimens.  The methods and locations of trapping were the  same as described e a r l i e r . Male snap-trapped specimens were opened with a mid-ventral i n c i s i o n from the abdomen t o the posterior end of the scrotum.  The positions of the  testes were noted, the length of the right t e s t i s was measured t o the nearest millimeter, and a small sample was taken from the most d i s t a l extension o f the epididymis.  Epididymal samples were placed i n water on microscope  s l i d e s , covered with cover s l i p s , macerated, and examined at 400 magnifications.  I f sperm were present they could be e a s i l y seen. Female reproductive t r a c t s were cleared and studied following the  method of O r s i n i (1962 a,b).  The exact procedure followed was t o remove the  entire uterus with ovaries, cervix and part of the vagina as a single u n i t . It was then attached t o a 1" x 3" microscope s l i d e with a thread through the c e r v i x and another around the t r a c t near the ovaries.  The t r a c t s were stored  i n neutralized 10$ formalin and then bleached, dehydrated and cleared i n an automatic t i s s u e processor.  The schedule followed was?  50$ alcohol + hydrogen  peroxide 2 hours, 70$ alcohol + hydrogen peroxide 2 hours, 80$ alcohol +• hydrogen peroxide 2 hours, 95$ alcohol 2 hours, absolute alcohol 2 hours, absolute alcohol 2 hours, 50$ absolute alcohol + 50$ x y l o l l£ hours, x y l o l 3| hours, and f i n a l l y benzyl benzoate f o r storage. A few female t r a c t s f a r advanced i n pregnancy, or i n which uterine blood vessels had been ruptured by trapping, were not s u f f i c i e n t l y bleached  -40-  by  the process  and  hydrogen  and  cleared  outlined  T h e s e t r a c t s w e r e r e h y d r a t e d t o B0%  above.  peroxide, bleached  f o r a further 6 hours,  and t h e n  alcohol  dehydrated  again.  The  p r e p a r a t i o n s were examined u n d e r a d i s s e c t i n g m i c r o s c o p e  oblique light  as  suggested by  partum, pregnant,  o r n u l l i p a r o u s ) was  s c a r s w e r e made, a n d p r e s e n c e For  the purposes  summers o f 1964 the analysis  (1962a).  Orsini  and  1965  noted,  Condition of the tracts counts  o f embryos a n d  of ovulatory f o l l i c l e s  of this  section  were p o o l e d .  with  was  live-trapping  Insufficient  o f r e p r o d u c t i o n on a w e e k l y b a s i s  (post-  placental  noted. data  f o r the  d a t a were p r e s e n t  for  s o o b s e r v a t i o n s made i n  each  2 two  week p e r i o d w e r e p o o l e d .  analysis  and  The  numbers were u s e d  then converted t o percentages  To  c a l c u l a t e t h e number o f l i t t e r s  used t r a p p i n g r e c o r d s o n l y f o r t h o s e once e v e r y 3 weeks  o f 3 w e e k s was  slightly  over  about  3  weeks  used because  (21-25  days  (Eisenberg,  was  evident, such  two  weeks o f l a c t a t i o n .  I963).  be  evident f o r at least The  of  as any t i m e  recognized i n the  animals  period  female p e r  summer  had been t r a p p e d at  P.  With  field  as  californicus  least  as  end.  the  is  lactation  l e a v e t h e burrow at  the trapping schedule described  captured at least  early  I  estimate o f gestation period  once when o u c h  d u r i n g t h e l a s t week o f p r e g n a n c y ,  11  o r 12  d a y s and  activity  or the  first  pregnancy  lactation  may  t h r e e weeks.  number o f l i t t e r s  and  understanding.  Some o f t h e t r a p p i n g r e c o r d s i n d i c a t e t h a t  captured both the  week o f J u l y  the best  3 weeks.  above a r e p r o d u c i n g a n i m a l would be  can be  females t h a t  of  adult  for Chi  d a y s ) ( E i s e n b e r g , P e r s . Comm.) a n d  i s a l s o p r o b a b l y around  22-25  per  ratios  from t h e b e g i n n i n g o f t h e r e p r o d u c t i v e season t o t h e  A period  period  f o r ease  as  p e r young  first  and  calculated  f o u r t h week o f A u g u s t  t h e t h i r d week o f A u g u s t .  a young animal would  f e m a l e was  To  e i t h e r have t o be  reproduce  and  from  or the  records fourth  avoid these  s e x u a l l y mature and  conceive  -41-  in the  t h i r d week o f J u n e o r n o t  September. these  No  evidence  possibilities  R E S U L T S AND  can  be  bear a l i t t e r  found  i n the  u n t i l the  trapping  s e c o n d week  records  that  of  either  of  occurs.  DISCUSSION  Male Figure i n m a l e P. the  parvus.  spring t o  o f F i g u r e 7b April.  7a,  By  c  i l l u s t r a t e s the  Unfortunately  determine the indicates that  the  showed t h a t  b,  end  most  males remained  o f May  reproductive  about two  weeks b y  In males i n t h e the  low  a r e a was  high  high  area  area  i n the  the  low  animals.  area  had  ceased  high  by  i n males  the  The  o f J u n e , when  the  area began t o d e c l i n e ,  E a r l y i n August  and  activity  early in  end  reproductive  o f August  followed activity  a l l activity  in  over.  High area t h a n low  scrotal testes  end  in  Extrapolation  reproductively capable.  condition u n t i l the  animals  e a r l y enough  activity.  some m a l e s h a d  p o p u l a t i o n was  reproduction  collected  a l l indicators of reproductive  percentage of reproductive in  of reproductive  least  or a l l o f the  In  cycle of  animals were not  onset at  general  m a l e s may  males but  the  h a v e come i n t o r e p r o d u c t i v e  d i f f e r e n c e was  m a l e s d i d , however, go  out  not  condition  significant  of reproductive  earlier  ( F i g u r e 7b).  condition  The  significantly  earlier. Young males o f next  spring.  disappeared, in  August.  i n young  I n one  area,  t h e young This  e i t h e r area  d i d not  become r e p r o d u c t i v e  however, where a l l a d u l t  immigrant  indicates that  animals  i n an  m a l e s came i n t o r e p r o d u c t i v e social  interaction  may  until  prevent  the  area  condition early sexual  maturation  males.  Female Reproduction  i n females d i d not  begin  until  l a t e May,  when a  large  -42-  F i g u r e 7<,  A  0  Percentages  sperm i n t h e Bo  Percentages  1964 Co  and  o f males  from t h e  high  d i s t a l portion of the  1965.  and  o f l i v e - t r a p p e d males w i t h  Greatest t e s t i s  length of high  low  epididymis,  and  low  areas  1965«  scrotal  with  testes,  area males,  1965.  -43-  p e r c e n t age ( F i g u r e 8) early  of the  perforate  Tn t h e  c  and  late  low  August  area  nificant  low  first  area  part  o f June t h e  at  a high  r e p r o d u c t i o n was were s t i l l  In l a t e The  shorter,, female per  taking place  reproduclngo  areas  In h i g h  area  in late  July  and  and  throughout  lactating  animals  were o n l y  sig-  season  l a t t e r fact  for high  area  f e m a l e s was  becomes a p p a r e n t when t h e Table  earlier  V I I I shows t h i s  comparisono  summer w h i l e  animals  produced  an  average o f only  13  litters  per  summero  similar  to that  duction  i n Po  found  by  animals  t o come I n t o  Reproductive  two  to  the  a l t i t u d i n a l survey  area  result of  is  repro-  XX  did not  of the  shorter reproductive  Some o f t h e  0  In  0  reproductive  only  one  low high  season  in  area young reproduced a r e a has  a young  the while  female  been  conditiono  Season  two  to  (Asdell,  evaluate  populations  react t o the  cause development  reproduction  effect  Table  is difficult  populations  photoperiod  i n an  Low  high  This  per  manieulatuso  i s shown b y  e x h i b i t e d by  (I960)  Dunmire  Another apparent  It  D  and  number o f l i t t e r s  per  observed  of  The  litters  area  the  August„  two  high  but  D i f f e r e n c e s between p r o p o r t i o n s  average o f over  the  July»  females,  an  area  animals  until late  had  high  of  until  August„  summer i s c a l c u l a t e d ; ,  animals  differences in ratios  l e v e l i n both  o f pregnant  reproductive  This  pregnant  significanto  continued  In p r o p o r t i o n s  some w e r e  f e m a l e s became p e r f o r a t e o r p r e g n a n t  females were s i g n i f i c a n t  differences  area  no  animals  perforate  f e m a l e s were p e r f o r a t e and  pregnant were  Breeding By  area  None o f t h e  0  June  high  I965) of the  is possibleo  the  differences i n reproductive  o f animals  because  same e n v i r o n m e n t a l  and  temperature  i t i s n o t known i f t h e  cues t h e  same w a y »  i960)  have been  (Parks,  seasons  gonads o f s e a s o n a l b r e e d e r s  to  Both reported  a state i n which  -44-  Month  Figure  80  Low O High A  A„ P e r c e n t a g e s o f h i g h that  were  (B) » P r e g n a n t ,  (C),  and low l i v e - t r a p p e d  perforate,  Lactating,  and  I964  and  I965.  females  -45-  TABLE V I I I .  Numbers adult in  of litters  per  TABLE D U  Numbers  f e m a l e p e r summer  h i g h and low a r e a s .  in  1964-1965o  High  of litters  young-of-the-year  h i g h and low a r e a s ,  1964-1965.  Low  High  N  20  20  N  10  X  lo30  2.06  X  0  0-2  Range S  1-3  0.27  2  Range  Low  28 Oo35  -  2  0.33  S  0-1  -  T  4.85  T A B L E X.  per female  Comparisons scar  o f embryo  (P0L.S0)  comparisons  (Embo) a n d  placental  counts between a r e a s , and  b e t w e e n embryo a n d  placental  s c a r c o u n t s , 1965o  High Area Embryos  PoLoS.  Low Embryos  Area PoL.So  Embryo - P.L.So  23  16  4-6  4-6  8  20  8  11  28  X  5.0  4o 62  4.90  4 088  4.73  4.89  Range  4-6  4-6  4-6  4-6  4-6  4-6  s  lo0  0.56  0.41  0o41  0.62  0.40  069  Low  Embryo  3  T  -  Low  N  2  High  High  .68  PoL.S.  -46In view  of the  reaction t o photoperiod came i n t o  of  ova  may  best  d i f f e r e n c e s between t h e  e x p l a i n why  r e p r o d u c t i v e c o n d i t i o n at t h e  development the high  environmental  i n the  females  area being  due  1965)0  (Asdell,  same t i m e s  t o a greater food The  differences  supply  i n times  the differences  that  the hypothesis  reproductive  do  not  support  the  end  duction  of the breeding  of the  show t h a t  o f gonadso  p r o b a b l y be as  and The  female  was  low  from lower  one  the  of the  t o be  trigger in  maturation  animals  go  o f young  out  females  of a photoperiod-controlled  onset  t h a t most b r e d  (Table X )  e a c h other» embryo  D  Peromyscus m a n l c u l a t u s  i n repro-  observations at  i t i s Impossible  of reproduction  the  female  and  the  19  per year,  to point to  Further study  factors  by  of breeding local  a  would  influences the  onset  develop-  will  factors  such  s p e c i e s o f mammals i n a n found  t h a t a l l were  area  cyclic  d u r i n g t h e p e r i o d o f maximum p r e c i p i t a t i o n o number o f e m b r y o s a n d  C o u n t s o f embryos and f i g u r e but  placental scars  placental  were not  P l a c e n t a l scar counts were lower, counts  observed  observations  0  working with  from t h i s  Post-partum  nicely with the  differences  above mentioned  o f 8-14"  o v e r a l l average  varied  fits  i n f l u e n c e d t o a l a r g e extent  (i960),  Prakash  4°85  areas  than  may  earlier  at which the  agree w i t h the  o f d a t a a t hand  a total precipitation  breeders  and  amount  season  Ovulation i n the  found  rainfall.  with  causing  areas  r a t e s i n June  i n percentages  factor  and w i t h  I t does not  f a c t o r t h a t causes  probably ment  season  reproductive  With the single  a controlling  i n young animalso  beginning  low  a  periodo  Termperature as at  and  Photoperiod  a l s o , w i t h t h e higher pregnancy  o f r e p r o d u c t i v e c o n d i t i o n and reproduce  males on h i g h  areas  s c a r s from  significantly but  not  per high  different  significantly  0  e s t r u s has (Svihla,  b e e n r e p o r t e d i n some s u b s p e c i e s 1932)  and  i n several other  rodents  of (Asdell,  -47-  I964) but t o my knowledge has not been reported i n heteromyids.  No ovulatory  f o l l i c l e s or pregnancies were found i n animals with placental scarso indicates that a post-partum estrus d i d not occuro  This  Overlap i s nearly 100$  between l a c t a t i n g animals and those with p l a c e n t a l scars*  This Indicates  that p l a c e n t a l scars i n these animals l a s t f o r about 3 weeks<> Reproductive data on Po parvus available from other areas are presented i n Table X I  a  The sample s i z e  p  particularly  i s small and the samples may not be comparableo  i n the study i n Utah,  There appears t o be a trend  f o r the reproductive season i n the southern areas t o begin and end  earliero  There may be a s l i g h t lengthening o f the reproductive season since young animals are born only i n a three month period i n B r i t i s h Columbia but i n a four month period i n the other areas  0  Scheffer (1938), working i n the State o f Washington, found an average of 5° 17 embryos per pregnant female.. different  This figure i s not s i g n i f i c a n t l y  from the average found i n t h i s study,,  The other studies do not  present enough data f o r a s t a t i s t i c a l comparison, but there appears t o be a trend t o l a r g e r l i t t e r s i n the southo  CONCLUSIONS 1  High and low area males came into reproductive condition at  0  the same time Zo  e  Young d i d not normally reproduce i n either area» High area females came into and went out of reproductive  condition s i g n i f i c a n t l y e a r l i e r than did low area femaleso 3o  Young females i n the low area may reproduce while those i n the  high area d i d noto 4«  Embryo and p l a c e n t a l scar counts from the high and low areas  did not vary s i g n i f i c a n t l y 5o  0  The average was 4«85<>  Low area females had s i g n i f i c a n t l y more l i t t e r s per summer than  TABLE XIo  Summary o f a v a i l a b l e r e p r b d u c t i b n d a t a o n Po p a r v u s Yes-no r e f e r s t o whether author s t a t e s that young a r e born t h a t montho Q u e s t i o n mark i n d i c a t e s c o n f l i c t i n g e v i d e n c e o R e p o r t e d number p e r l i t t e r i s a l s o s h o w n 0  0  ——• March  ~ April  May  —"  •—  June  July  '  1  Aug*  Septo  '—*-  1  N  Range  X  2 S  T  British Columbia  39  4-6  4<>85 <>45  2-8  5«17  no  no  no  yes  yes  yes  no  no  no  yes  yes  yes  yes  no  1946)  ?  yes  yes  yes  no  no  5»58  1957)  yes  yes  yes  no  no  5»38  Washington (Scheffer,  1938)  132  Nevada (Hall, Utah (Duke,  1°47  lo59  -49-  high  area 60  females No p o s t - p a r t urn  e s t r u s w a s observed,,  Home R a n g e a n d B u r r o w s  Information  o n home r a n g e  contributes t o t h e understanding o fpopulation  phenomena a n d movements o f a n i m a l s , g i v e s c l u e s a b o u t between animals  a n d may r e f l e c t  behavior o f t h e animal environment water  loss  t h e amount  of available  i s important because  t h e burrow  o f t h e animal during t h e daylight and temperature  the relationships  hours  food*  The burrowing  i sthe physical  and s o has an e f f e c t  on  regulation,,  METHODS T r a p p i n g was c o n d u c t e d  as described  a r e a w a s t r a p p e d f o r 15 n i g h t s f r o m May 12-23 range Th®  a r e a w a s t r a p p e d f r o m May 14-25  followed  f o u r o c c a s i o n s i n each  u n t i l they  entered a burrow  11  t h e h i g h home  and June 7-9°  a n d J u n e 3-6  c i r c l e o f s n a p - t r a p s was o p e r a t e d f o r On  earlier,,  T h e low,home  for a total  n i g h t s f r o m May  range  o f 16  nights,,  13-23°  area c a p t u r e d animals were r e l e a s e d and  0  The l o c a t i o n  o f t h e b u r r o w was n o t e d  on a map* Home r a n g e  a r e a o f a n i m a l s c a p t u r e d more t h a n  computed b y t h e boundary  strip  method*  f i v e t i m e s was  Capture p o i n t s were p l o t t e d ,  1/2 t h e  d i s t a n c e t o t h e n e x t t r a p was added, and o u t l y i n g p o i n t s were c o n n e c t e d t o form a polygon  o f t h e greatest  possible  t h e n b e computed b y t h e f o r m u l a s inside Hayne  - l)/4)  (1949)°  x 100*  Home r a n g e  area*  Area =((l/2  Area,  i n square meters,  # points  could  on b o r d e r ) + ( # p o i n t s  c e n t e r s w e r e d e t e r m i n e d b y t h e method o f  -50-  RESULTS AND DISC DBS 3DNS Home Range One i n d i c a t i o n o f home range size i s the distance i n animal t r a v e l s . This can be calculated using either distances between successive captures or between the o r i g i n a l l o c a t i o n o f capture and a l l others (Hayne,  1949).  Table  XII presents the r e s u l t s o f measuring the distance between o r i g i n a l capture points and a l l subsequent capture points,,  The home range s i z e , as indicated  by t r i p length, i s the same f o r high and low area males.  There i s , however,  a s i g n i f i c a n t difference i n home range size between low area males and females.  So few observations were made on high area females that a s t a t i s t i -  c a l treatment was not p o s s i b l e .  They appear t o have a home range s i z e  s i m i l a r t o that o f the low area females.  This suggests that high and low  area males have home ranges o f the same s i z e , that females have ranges o f the same s i z e , but that the differences between the sexes i s s i g n i f i c a n t .  The  difference between the sexes was expected and agrees with most reports i n the l i t e r a t u r e (Davis and Golley, Blair  (1943)  1963).  reports that i n Dipodomys merriami and D. o r d i i the  home range of the females i s smaller than that o f the males i n March, but by May the home ranges are the same s i z e .  He reports that i n Perognathus  p e n i c i l l a t u s i n the same area the home ranges o f the males were s i g n i f i c a n t l y larger than those of the females from March through May.  The p o s s i b i l i t y  of the difference i n home range size between males and females being an a r t i f a c t of season i s not ruled out but appears u n l i k e l y . The f a i l u r e t o f i n d differences within each sex between areas was s u r p r i s i n g and disagrees with the usual generalizations about home range size.  Davis and Golley  (1963) state  the points o f disagreements  1.  "numerous  studies o f small rodents give d i f f e r e n t values f o r d i f f e r e n t e c o l o g i c a l s i t u a t i o n s ...", 2.  "Mammals i n dense populations have smaller ranges than  those i n sparse populations".  TABLE X I I .  D i s t a n c e between points. (p.*  Meters between f i r s t and  High  _. .  I n c i d e n c e 0. % N  successive captures  .05)  o r i g i n a l capture p o i n t and s u c c e s s i v e  P r o p o r t i o n s shown f o r 20 Chi  2  marked  s  meter i n t e r v a l s .  .  Area  Chi  Low Incidence 0 % N  2 1  capture  Significant  Chi  I n c i d e n c e 0* % N  Area  Chi*  Incidence 0 % N  0-25  33.3  4  25.0  H  O.64  30.6  49  3.61  42.2  49  26-45  16.7  2  21.4  12  O.65  26.9  43  4.4  38.8  45  46-65  33.3  4  30.4  17  O.OOI4  30.6  49  0.75  25.9  30  66-85  0  0  10.7  6  0.22  7.5  12  7.4  0  0  86-105  0  0  3.6  2  0.005  1.9  3 0.0034  0.9  1  106-125  16.7  2  8.9  5  2.83  2.5  4 0.30  0.9  1  Total  12  No.  2 Homogeneity t e s t  Chi  s  s  116  160  56 6.35  103  s  -52-  T a b l e X I I I shows t h e r e s u l t s a r e a method,, independent ranges  T h e d a t a a r e t o o few f o r s t a t i s t i c a l method  o f males  have, b y t h i s high  o f home r a n g e comparison  s u p p o r t s t h e above evidence t h a t  I n t h e h i g h a n d l o w a r e a s a r e t h e same*  method a l s o ,  The fact  that  low population d e n s i t y  specific  o f t h e home  The low a r e a  a s m a l l e r home r a n g e t h a n t h e m a l e s .  home r a n g e s  a r e t h e same s i z e  suggests that  a g g r e s s i o n do not determine  i n P. p a r v u s  home r a n g e  size  size by the  but this  the sizes  a r e a f e m a l e s w e r e c a p t u r e d t o a l l o w a n y r e a l home r a n g e  t o b e made. and  o f analysis  females  T o o few  determinations  i n areas o f high  c o m p e t i t i o n and i n t r a o r space  out t h e  animals o Four t y p e s overlap  o f d a t a a r e a t hand t o b e a r  o f home r a n g e s ,  burrows and removal home r a n g e  trappingo  animals  o f home r a n g e  It Few  extent and animals w i l l  that  r e p r e s e n t about t h e amount  a Poisson distribution.  greater than unity  will when  i f s p a c i n g mechanisms were  (Andrewartha  clumping,  and B i r c h ,  1954)°  area a r e randomly  and u n i t y  indicates  The c h i squared  significantly  i n a l l groups.  show g r e a t e r  functioning.  the distribution  A variance o f less than unity  indicates  t h a t t h e burrows o f males,  of fitting  c a p t u r e d more  resident population.  o f mutual overlap i s very great  none o f t h e s i x v a r i a n c e s d i f f e r  low  o f animals  h a l f o f t h e adult  T a b l e X I V shows t h e r e s u l t s  bution  home r a n g e s  n o t e x p a n d t h e i r home r a n g e s  animals were t r a p p e d on t h e h i g h a r e a b u t t h o s e t r a p p e d  overlap than would be expected  to  out animals  a r e removed,,  5 times, which  i s apparent  centers, distribution o f  be randomly d i s t r i b u t e d ,  F i g u r e 9 shows t h e home r a n g e b o u n d a r i e s than  hypothesis; mutual  I f c o m p e t i t i o n does not space  c e n t e r s and burrows w i l l  overlap t o a large adjacent  distribution  on t h i s  indicates a random  figure  from u n i t y .  spacing, distri-  indicates  This  females, and t o t a l p o p u l a t i o n s i n t h e  distributed.  o f burrows  that  indicates  h'Igh a n d  -53-  TABLE X I I I o  Home r a n g e s i z e a s d e t e r m i n e d bymeasurement o f a r e a s .  Noo times captured  N Low  d  1  Range  X  N £  Range  meters^  0*  6  425-1250  350-1500  9-10  4 800-1325  11-12  2  overall  22  950-975  330XL5OO  893  73 5  983  1116  962  10  2  4  1  250-1250  550-700  500-1050  575  664  400-1688  Range  x  10  6  N High  7-8  2  meters  Low  5-6  625  675  1  1  575  17 250-1250 656  8  1250  1400  -  1250  1400  -  400-1688  0  meters^  756  898  -54-  Figure 9o  Home r a n g e s o f m a l e s a n d f e m a l e s i n h i g h a n d l o w a r e a s . T h e minimum n u m b e r o f c a p t u r e s u s e d t o d e t e r m i n e a home r a n g e was f i v e o The black dots represent t r a p l o c a t i o n s .  -55-  TABLE XIV. Mean, variance and C h i values f o r f i t t i n g d i s t r i b u t i o n o f burrows t o a Poisson d i s t r i b u t i o n . None o f the C h i values i s s i g n i f i c a n t . This means that the animals* burrows are randomly d i s t r i b u t e d .  N Low  6"  X  S  2  X  2  28  0.200  1.07  128.0  Low (j)  39  0.283  0.84  100.2  Low t o t a l  67  0.475  0.67  79.8  High t?  16  0.117  1.03  122.7  High 0_  11  0.100  1.08  128.0  High t o t a l  27  0.225  1.08  128.8  .05 l e v e l o f s i g n i f i c a n c e - 130.  TABLE XV.  2 Mean, variance and C h i values for f i t t i n g d i s t r i b u t i o n o f None o f the home range centers t o Poisson d i s t r i b u t i o n . values i s s i g n i f i c a n t .  N  X  S  2  x  2  6"  22  0.230  1.01  119.7  Low 0_  17  0.192  0.81  96.9  Low t o t a l  39  0.45  1.004  119.5  Low  High (?  8  0.108  0.915  108.9  High t o t a l  8  0.133  0.90  106.5  -56-  T a b l e X V shows t h e r e s u l t s distribution for  both  o f home r a n g e  or configuration  (1963)  Calhoun when r e s i d e n t  animals  are  not affected by s o c i a l  not  occur.  the  short period  home r a n g e s .  after the first  101  circle  p l u s 1/2  that  i s  tured  than  this  f o r 11 d a y s b e f o r e  o f r a i d s b y magpies.  Because o f  may n o t b e c o n c l u s i v e , b u t  captured p e r day drops as  There  a r e two l i n e s  c a p t u r e d on o f evidence f o r t h e number  i n t h e area covered by t h e c i r c l e ,  a n d t h e t r a p p e d a r e a was t h e d i a m e t e r d i a m e t e r , w a s 0.001  mice p e r square  higher proportion than  parvus  should  t o test  need n o t b e h y p o t h e s i z e d t o account  The d e n s i t y  I f t h e animals  the circle  o f P.  o f home r a n g e  o f an experiment  i n t h e same w a y f o r r e s i d e n t  0,0032  that  expand t o occupy  t h e l a r g e number o f a n i m a l s  t h e mean home r a n g e  calculated  area  interaction  few d a y s .  Immigration  captured.  site or  on t h e edge o f t h e t r a p p e d a r e a d o n o t  Number o f a n i m a l s  mice were r e s i d e n t s  figure  range  of  animals  c o u l d be argued  this.  animals  of social  expansion  involved the results  4 r e p r e s e n t s a wave o f i m m i g r a t i o n .  against  A  o f time  seem t o i n d i c a t e t h a t  It  all  had t o be terminated because  that  o f another.  Snap t r a p s s e t i n a c i r c l e were o p e r a t e d  experiment  of  interaction this  T a b l e X V I summarizes t h e r e s u l t s  expand t h e i r  imply  I f , a s t h e e v i d e n c e a b o v e i n d i c a t e s , home r a n g e s  the  day  on t h e b a s i s  t ot h e  distribution  on t h e c h o i c e o f a burrow  a r e r e m o v e d a d j a c e n t home r a n g e s w i l l  open a r e a .  prediction.  show a r a n d o m  o f t h e home r a n g e  predicts  the  expected  also  T h e s e random d i s t r i b u t i o n s  o f one a n i m a l has n o e f f e c t  on t h e l o c a t i o n  they  centers, which  areas and a l l s e x groups.  the presence  o f a p p l y i n g t h e same s t a t i s t i c  of the  mice p e r square  animals  on t h e nearby  meter. home  meter.  c a p t u r e d on t h e f o u r t h d a y w e r e m o s t l y  on t h e f i r s t  assuming  immigrants*  a  d a y s h o u l d have b e e n c a p t u r e d on t h e r i m  inside the circle.  On t h e f i r s t  d a y 22  animals were  o n t h e r i m a n d 7 o n t h e i n s i d e , w h i l e o n t h e f o u r t h d a y 21  animals  capwere  -57-  TABLE XVI.  P. parvus  Numbers of animals captured per day In the c i r c l e trap l i n e .  Peromyscus maniculatus  Total  Days  0*  0.  sex  0  G  E* E-  £• 2-  1  17  1G  2  2  3  29  55  2  7  5  3  2  12  5  3  7  4  0  1  11  1  4  18  7  2  2  28  4  5  9  5  0  0  14  0  6  1  1  2  0  2  2  0  3  1  2  2  0  1  1  0  101  16  7 1  .8 9 10  -  3  2  1  11  -58-  captured of  on t h e r i m a n d 7 On t h e i n s i d e .  e v i d e n c e we c a n r e j e c t  that,  at least  territory  use to  up t o 10 d a y s ,  similar  1943) a n d p o s s i b l y Home r a n g e s  n e l s o n i ( D i x o n , 1958  lap  i n females,  i n home r a n g e s  aredifficult  i n size t o that P. m e r r i a m i  t o compare b e c a u s e o f t h e Most  o f t h e s p e c i e s appear  reported here.  (York,  a n d i n P. m e r r i a m i  o f females.  1949).  with  (Blair,  Blair  o v e r l a p and York  Individuals  P. p e n i c i l l a t u s  1949) h a v e l a r g e r home  (York,  reports l i t t l e  a p p e a r t o h a v e o v e r l a p p i n g home r a n g e s active  b o r d e r i n g o n empty  o f m a l e s o v e r l a p i n P. p e n i c i l l a t u s  Dixon  occurs and can s t a t e  ranges.  methods a n d amounts o f t r a p p i n g .  h a v e home r a n g e s  overlap  immigration  m i c e w i t h home r a n g e s  s t u d i e s o n home r a n g e  of different  (Blair,  t h e hypothesis that  d o n o t e x p a n d t h e i r home The  On t h e b a s i s o f t h e a b o v e t w o l i n e s  ranges.  1943),  reports seasonal  reports great  o f Perognathus  P.  over-  spp. g e n e r a l l y  some e x c e p t i o n s  i n reproductively  females.  Burrows The to and  a large  type  extent  P. m e r r i a m i  o f burrow  system  crust  i n t h e s o i l was p r e s e n t ,  hole.  tunnels  under limestone  with  P. p e n i c H i a t u s  t h e animals b u i l t  c o n s t r u c t e d a more  below.  i n an a r e a where a s u b - s u r f a c e m i n e r a l i z e d  found t h a t  P. p a r v u s  excavated  several  Most  ina  tunnels single  as a r o o f f o r t h e t u n n e l s , t h e system  (1937) f o u n d  slabs.  simple  constructed a  joined t o penetrate t h e mineralized layer  Blair  a  complex  t h e c r u s t b u t a complex system  Then, w i t h t h e m i n e r a l i z e d l a y e r  became complex a g a i n .  i n sand  m i c e seems t o d e p e n d  was f o r m e d o n t h e l o a m t h e a n i m a l s  (1938), w o r k i n g  from t h e s u r f a c e , which  that  In loam t h e animals  o n l y one e n t r a n c e t h r o u g h  Scheffer layer  D e n y e s (1954) w o r k i n g  i n t h e l a b o r a t o r y found  When a h a r d with  constructed b y pocket  on t h e s u b s t r a t e .  system w i t h two entrances. system.  system  P. h i s p i d u s c o n s t r u c t i n g c o m p l e x  o f these t u n n e l s had s e v e r a l  entrances.  -59-  He states that the burrow systems of immature animals were l e s s complex than those of adults. It appears that, given a choice, Perognathus  spp. excavate burrows  with several entrances under a structure such as a rock or mineralized layer i n the s o i l .  There i s often a single nest chamber below the l o c a l frost l i n e  (Hlbbard and Beer, i960) and a storage chamber which may be located near the entrance (Scheffer, 1938). during the day.  Tunnel entrances may be, but are often not plugged  A mound of s o i l i n front of the burrow entrance i s often at  least a temporary feature of pocket mouse burrows. The burrows excavated In t h i s study were In sandy s o i l without fragments or mineralization.  Two basic types of burrows were 'found.  most numerous type, the "escape" burrow, was  The  found t o be simple and shallow,  20-30 cm deep, without a nest chamber or food cache but with at least two entrances.  The "permanent" burrows had nest chambers, food caches, several  entrances, and several tunnels penetrating t o maximum depth which was more than 1 m.  usually  The presence o f the two types o f burrows helps explain why  animals were observed t o enter d i f f e r e n t burrows when released i n d i f f e r e n t parts o f t h e i r home range. It i s probable that each animal constructs or occupies a single permanent burrow system and excavates or explores several escape burrows In d i f f e r e n t parts of i t s home range. underground  An animal would, therefore, have an  refuge available near a l l parts of i t s home range.  states that only one adult animal l i v e s i n each burrow system.  Scheffer (1938) This was  determined by trapping under cages set over burrow entrances and by excavating burrows i n the winter.  Other species o f Perognathus (P. hlspidus, B l a i r ,  1937? P. p e n i c i l l a t u s . B l a i r , 1943. adults.  P« merriami. B l a i r , 1953)  l i v e singly as  On t h i s basis permanent burrow systems must be considered as defended  territory.  It i s not known i f escape burrows are defended and used by only  -60-  one  animal or i f they are u t i l i z e d  by several  animals.  Territoriality Scheffer of  Perognathus  spp. w i l l  (1938)  when two a n i m a l s  not r e a d i l y t o l e r a t e  b e h a v i o r a l mechanisms for in  (1963)  and Eiseriberg  are confined. conspecific  f o rminimizing such  minimizing contact tend t o minimize s i t u a t i o n s where r e t r e a t  immediately  Eisenberg states that  p h y s i c a l contact and have contact.  fighting  i s possible.  surrounding an animal that  d e s c r i b e extreme a g g r e s s i v e n e s s Perognathus evolved  T h e s e b e h a v i o r a l mechanisms  and p o s s i b l e p h y s i c a l  injury  They a c t t o form an i n v i o l a t e  i s recognized by both  zone  members o f a n  encounter. It  appears  genus, t h e permanent of  that  i n P. p a r v u s ,  t h e home r a n g e t h a t  the influence  o t h e r members o f t h e  burrow and p o s s i b l y t h e escape burrows a r e t h e o n l y p a r t s a r e defended  c o n f i g u r a t i o n and l o c a t i o n of  a n d p r o b a b l y most  and c a n b e c a l l e d  o f the rest  o f other animals  a territory.  o f t h e home r a n g e  and independent  seem t o b e  o f at least  some  The  size,  independent ecological  factors.  CONCLUSIONS  ranges  1.  M a l e s h a d l a r g e r home r a n g e s  than d i d females.  2  Males,  o f h i g h a n d l o w a r e a s h a d home  0  o f t h e same 3.  males,  4. adjacent  Adult animals  Each  home  range.  a n d home r a n g e  c e n t e r s were d i s t r i b u t e d  d i d not appear  h i g h and low a r e a  randomly f o r  animals.  t o e x p a n d t h e i r home r a n g e s  when  removed.  adult  was o c c u p i e d s i n g l y , its  sites  and t o t a l p o p u l a t i o n s I n b o t h  animals were 5.  females,  size.  Burrow  females,  and probably  a n i m a l had a complex, permanent burrow  and defended,  and s e v e r a l  escape burrows  system,  scattered  which around  -61-  Populat ions  The  date  on p o p u l a t i o n s p r o v i d e a y e a r l y  measures o f l o n g , and s h o r t , t e r m parison  o f d e n s i t y and s u r v i v a l  identification  survival  rates.  and p e r i o d s o f h i g h m o r t a l i t y w i t h factors  o f numbers  limiting  factors  the distribution  may  a com-  and  The c o r r e l a t i o n  environmental  and  These data permit  r a t e s i n t h e h i g h and low a r e a s  o f periods with high mortality.  f o r m a t i o n about  cycle  of densities  provide i n -  of the species.  METHODS Areas were t r a p p e d as d e s c r i b e d e a r l i e r . trap-affected trapping areas  area  area.  i s unknown,  Since the sizes  density figures o f home r a n g e s  a r e a p p a r e n t l y t h e same t h i s  purposes.  Data  on t h e numbers  figure  o f animals  Because t h e s i z e  are expressed o f animals  necessary  These counts  are at equal r i s k  o f capture.  a r e minima because animals rates, rates  calculated expressed  RESULTS  AND  numbers, t h a t  The f i g u r e s  f o r comparative captured  cannot  make t h e  marked and unmarked  given, based  and Phipps  plus  b e f o r e and a f t e r t h e  on d i r e c t  may b e p r e s e n t b u t n o t c a p t u r e d .  b y t h e method o f C h i t t y  The  assumption, animals enumeration,  survival  (1966), a r e a l s o  minimum  a s s u r v i v a l p e r month.  DISCUSSION  Throughout  most  o f t h e y e a r t h e smoothed l i n e ,  of animals  per trapping area  continuous  sampling,  observed  a r e u s e d b e c a u s e we  f o r estimation of t o t a l  i n t h e h i g h and low  o f those  t h o s e known t o b e a l i v e b e c a u s e t h e y w e r e c a p t u r e d b o t h trapping period.  i n animals p e r  should be s u f f i c i e n t are counts  of the  number  ( F i g u r e 10),  but i n t h e f a l l  o f animals  averages  fluctuations  and s p r i n g t h e l i n e  (Table XVII).  indicating  departs  due t o  dis-  from t h e  I n September and October  b e g i n t o go i n t o t o r p o r and a r e no l o n g e r t r a p p e d ,  numbers  animals  s o t h e low numbers  of  I  o I  Month Figure  10.  T h e numbers low  areas  o f animals  from June,  present per area  1964  t o July,  smoothed b y eye f r o m d a t a p r e s e n t e d  1965«  i n t h e h i g h and "The l i n e s  i n Table  XVII.  were  TABLE  X V I X o  June Low Adult Adult Young Young Young Young  <?cf 9 G €T GT 99 No, 2 C? (f No. 2 0_ 0_  Total N o o per area  Numbers o f animals present i n t h e high and lew areas from June 1964 t o J u l y 1965°  July  Aug.  Sept.  0ct  o  17 18 41 37  16 19 44 36  Nov.  13 13 19 Ik 15 13 1U 11 2 2 16 13 7 7 16 13  Ik 18 15 15 11 17 16 16  1  15 16 14 13 17 17 15 15 1 0 0 1 1 1 1  13 33 23 23 13 34 24 24  15 16 23 24  14 16 30 20  16 16 17 14 30 30 37 31 20 20 24 21  38 34 42 33 19 17 21 16  33 35 30 29 16 18 15 14  37 35 65 51 18 18 32 26  51 102 78 78 26 51 39 39  78 113115 80 39 56 58 40  80 80 93 80 40 40 56 40  1 18 18 17 1 6 11 10  17 17 21 20 11 11 14 13 3 3  20 19 19 1U 12 12 13 12 12 8 6 6  19 10 16 13  18 17 17 11 9 9 14 9 9 19 13 13  17 17 17 17 9 9 9 9 9 9 9 9 13 13 14 13  2 24 29 27 8 10 9  28 28 38 36 9 9 13 12  56 49 49 69 19 16 16 23  57 62 48 48 19 21 16 16  48 48 49 48 16 16 16 16  21 19 23 15 16 14 18 17 1  1  1  Ik 14 15 14  High  Adult Adult Young Young Young Young  O^Cf $ $ rtf $ 0_ No. 2 G^cf No. 2 9 9  Total No. p e r area  23 11 18 17  19 18 18 11 9 9 17 13 13 18 ,17 17  48 65 57 57 16 22 19 19  18 9 13 17  TABLE XVII (cont'd)  April  May  Low Adult Adult Young Young Young Young  CfcT 9 § <T 0* Q <•> No, 2 No. 2  June  July  14 14 14 13 14 14 14 14  13 14 36 26  10 11 33 23  9 6 6 6 11 10 9 9 35 29 24 22 30 30 23 22  6 5 5 3 9 8 8 6 27 22 23 13 23 19 19 16 2 0 3 2 9 4  80 88 87 8? 85  31 38 36 36 21 22 23 22  11 11 31 24  11 11 30 24  ( f (f 5 g  No. p e r a r e a  40 44 44 42  76 77 77 84 77 76 42 38 38 38  85 85 75 62 62 59 42 38 31 30  67 54 67 67 44 34 27 34 22  Adult  Cftf  Adult  0  Young  O^Cf  17 17 17 17 17 14 14 14 9 9 9 9 9 9 9 9 . 10. 12 10 11 9 9 9 9 13 13 13 13 15 15 15 16  14 12 10 10 9 9 8 8 11 9 8 7 15 17 16 16 2  8 5 7 7 7 4 18 18 17 14 1 0 2 1 1 1 3 3  49 47 42 43 16 16 14 14  44 40 44 34 15 14 15 11  Total  $  Y o u n g 0. $ Y o u n g No.  2 <f ( f  Y o u n g No. 2 0_ 0_ Total No. p e r a r e a  48 48 48 48 16 16 16 16  51 50 48 50 17 17 16 17  9 8 7  8 7 6  ' t  -65-  animals  known t o b e  has  taken  The  low  in  alive  p l a c e and  i n O c t o b e r and  mortality that w i l l  numbers o f a n i m a l s  some a n i m a l s .  lumping  trapped  Showing w i n t e r  i t a l l into the  late  November r e f l e c t take  In the  place  early  m o r t a l i t y as  fall  months, but  both  some t i m e  mortality that  during the  spring reflect  constant  winter.  continued  i s more a c c u r a t e  torpor than  i s u n d o u b t e d l y an o v e r - s i m p l i -  fication. 10  Figure low  area  i s higher than  similar t o that  found  areas were h i g h e r The may  out  that  decreased  As  f a r as  by pocket south-west snap-trap  three points.  i n the high  In other  i n the  1965  floor  population size with  c o u l d be  mice i n t h i s facing  or  area.  slope.  nights.  some f a c t o r  No  Density factors  The  and  of the  a r e a , p r o d u c e d an animals  have been at t h e  but  and  local  slow because  few  at the higher extinction.  surplus animals  P.  low  areas  The  trend  XVIII.  maximum a l t i t u d e  area  4,700  reached  f t . on  altitude  appear t o be  a  in  100  limited  which v a r i e d with  altitude,  i n the high area,  1,500  litters  litters  f t . above t h e  parvus  must b e  If this  occurred,  summer a s  summer.  high  The  f t .  opposed highest  sample a r e a and  o f one  i s able t o  altitudes  per  per  for the production  i s also possible that  the treeline,  Animals  w h i c h p r o d u c e d 2.06  maximum a l t i t u d e  I964. and  at t h i s  both  altitude.  a v e r a g e o f 1.3  2,000  numbers i n  i s shown i n T a b l e  In t h i s  r e p r o d u c t i v e season,  a l t i t u d e p o p u l a t i o n s were about  high  grasslands were at  covariant with  low  area  altitude  distribution  above t h e  liable to  spring of  Perognathus were t r a p p e d  altitudinal distribution.  It  1965);  more f a v o r a b l e h a b i t a t .  highest  the  low  i n the  f t . i s about t h e  limit  the  than  higher  4,500  determined,  the  a r e a ; t h e y e a r l y c y c l e I n numbers i s  i s the  length  to  population density i n  d i f f e r e n c e i n average d e n s i t y between t h e  The may  The  s m a l l mammals ( S a d l e i r ,  spring of  indicate that the v a l l e y  to  by  brings  litter  per  summer.  occupy g r a s s l a n d s  present  i n very  low  ( T a b l e XTX).  to  density  r e p o p u l a t i o n would be  are produced per y e a r  may  very  Conversely,  -66-  TABLE X V I I I .  Number o f a n i m a l s known t o b e p r e s e n t , middle o f August, 1964, at d i f f e r e n t altitudes.  Low  High -  Home R a n g e  Area  1 - 2  Altitude  1,000  2,500  3,500  No./area  22.1  17.2  13.1  TABLE X I X .  3-5  High 7  Highest  9  8  4,500 2.0  Number o f y o u n g a n i m a l s p r o d u c e d p e r a r e a p e r y e a r i n h i g h and low a r e a s . The number, range and v a r i a n c e o f t h e r e p r o d u c t i v e d a t a a r e g i v e n i n Tables V I I I , IX, and X .  No. 2 $ / area  No. l i t t e r s / summer  N o . / l i t t e r  T o t a l No. young born  Adult  7.5  2.06  4.89  75.55  Y0Y  5.0  .35  4.89  8.56  Adult  3.7  1.30  4.73  22.75  Y0Y  3.0  0  0  Low  Grand Total  8 4 . U  High  22.75 0  -67-  i f  populations  i n the  t h e i r numbers t h e i r  v a l l e y p r o d u c e more y o u n g t h a n a r e  average l o s s e s  must b e  greater  needed t o  maintain  than t h o s e at the  higher  altitudes. Survival  rates  did  Chi  and  females have t h e r e f o r e  area  square a n a l y s i s  o f m a l e s and  adults  had  (Table  significant  XXI)  and  was  October  In view  of the  logical  s i g n i f i c a n c e even though a  of adult  insensitivity  s u r v i v a l In t h e  assume so t o  explain the  The  high  area  basis,  than did the  on  long  the  area  the  term,  survival rate  the  r a t e and  low  None o f t h e XX)  w e r e d e r i v e d was  determined  young  as w e l l  survive  low  losses take place  a r e a s may  area  area  area but  one  better,  (Tables as  XX  did the as  the  on b o t h and  area  adults  in total  numbers.  i n the young  animals.  from which  significantly  short  ( S t e e l e and  other  some I n s t a n c e s Because t h e  shown.  The  i t i s not  rates  i n the  c a l c u l a t e d are  biorates  between t h e  The  so.  necessary  high  two  a d u l t s , but XXI).  to  areas.  yearly  area on The higher  young, the  low  lower rethat  (Table  i n t e r v a l s were  Torrie,  I960).  better than  S u r v i v a l r a t e s w e r e c o n s i s t e n t l y low  o f low  rates  have  term s u r v i v a l rates  any  June, w i t h  for  T h e s e d a t a m e r e l y show  g r o u p s , h o w e v e r , s u r v i v a l f r o m O c t o b e r t o A p r i l was year.  adults,  significantly  d a t a may  (Table  all  time of the  not  d i f f e r e n t when c o n f i d e n c e  Pearson chart  High  area  a m o n t h l y and  XXI).  high  low  nor  Males  survival rate  i s not  d i f f e r e n t but  areas.  i s necessarily associated with the  proportions  f r o m a C l o p p e r and  high  yearly  square t e s t , the  be  consistently  and  difference in density  as w e l l  increase  mainly  classes  The  statistical  maintained  survived  i n the  Chi  young s u r v i v e d  low  young d i d not  productive  two  XX).  i n the  of the  age  s u r v i v a l rates than did  (Table  also higher  differ  d i f f e r e n c e s between them.  been pooled w i t h i n  consistently higher  except between August adults  show a n y  females d i d not  In  I t was  in April  at to  fall.  minima any  u n t r a p p a b l e (because o f a change i n b e h a v i o r or  animals that  emigration  from the  become trapping  TABLE XX.  June-July  P  ' N  July-Aug  0  Number o f a n i m a l s " r e l e a s e d (N) and p r o p o r t i o n ( P ) known t o be a l i v e one month l a t e r e  Aug -Sept e  P ' N P N ' . '  Low  0  Sept -0et o  P  o  N  Oct.-April  P  N  April-May  P  May-June  N  June-July  P  N  P  N  4 . 533  15  . 705  17  .727  44  .750  16  . 600  25  . 804  1.000  1  .000  1  .843  32  . 745  65  . 872  77  . 516  .875  32  . 859  29  . 422  20  .625  8  . 914  7  . 000  1 .583  12  .722  1 8  1.000  3  . 660  32  . 807  26  . 849  16  1.000  4 .666  15  .720  25  21  .902  13  . 563  Adults  Low  32 .-648 37  .677  59  Young  High  Adults  High  TABLE  X X I c  Long-term number Ghi  squares  calculated  Period  June Low A d u l t s  .895  P  June High  survival  released  e x p r e s s e d a s t h e number known t o b e  and t h e proportion  marked  3  . 934  are significant.  those  alive/the  each month ( P ) . marked  c  were  .  using Yates correction f o r continuity,.  Sept. Adults  surviving  Low Y o u n g  -  July High  Sept. Young  . 829  . 912  10/65  12/30  -  July  Sept. Adults  July  Low A d u l t s  Low Y o u n g  924  . 829  . 884  .912  9/20  10/65  7/24  L2/30  .  High  -  High  Young  Proport ion alive  X  2  14/32  12/44 2.24  6.99  s  7.73  s  6.13°  .69  -70-  area) w i l l be rates but  included  downwards.  The  i n numbers possibility  t h e r o u t i n e t r a p p i n g o f most  suggests  i t d i d not  population. died  I f an  occur. animal  o f a change i n b e h a v i o r cannot of the resident  T o r p o r , however, removes an a n i m a l  animals would be This  effect  may  August influx  t o the  o f new  leaving  evaluated by  animals  of the  low  survival  and  comparing  same a g e  animals end  group.  an apparent  The t h e two  low  factors  survival  and w a t e r  would be and  time  i n the  available.  i n good  rate  i n the  of year.  animals  The  time  The  low  a n i m a l s may  spring  of this  be  captured i n the  i n t e r a c t i o n may  have l i m i t e d  area, by  movement i s  of the  i n the  fall  explained by  spring,  leaves, insects appeared  survival during the  the  onset  of  at  months. either  f o o d o r w a t e r may  spring  of  the  i n the high  combine t o e x p l a i n  Even d u r i n g t h e d r i e s t stems, O p u n t i a  with  o f t h e m a l e s and  animals  cannot  lost  of  limit  however, and  seeds  t o be w e l l  condition.  Social  October.  are nearly balanced  combination  It i s possible that  form o f grass The  animals  s u r v i v a l of adult  d i s c u s s e d above.  survival during this food  movement o f a d u l t low  erroneously  i n July  r e p r o d u c t i v e season  torpor  indicated  to  s t u d y a r e a , t h e amount  Starting  of adult  o f l a r g e numbers o f y o u n g a n i m a l s .  of the  an  i n August  t h e number o f a n i m a l s  appearance  part  cause  entering the  (Table XXII).  of the  rates  torpid.  movements o f a n i m a l s w e r e g e n e r a l  area, high losses  adult  and  in torpid  correlated both with the  least  period  o f a c t i v e a n i m a l s , s e v e r a l months o f m o r t a l i t y  I f i t i s assumed t h a t  i n t h e low  and  sampling  in torpor  phenomena, w i t h a n i m a l s b o t h  n u m b e r o f new  month  from the t r a p p a b l e  c o n c e n t r a t e d i n t o t h e month when t h e a n i m a l s became  e m i g r a t i o n can be  out,  a s s i g n e d t o t h e month i n  monthly s u r v i v a l r a t e s  amounts o f e m i g r a t i o n c o u l d a l s o  rate.  ruled  o f animals  have c o n t r i b u t e d  Large survival  Although  be  survival  p o p u l a t i o n month a f t e r  entered t o r p o r before the October  i t entered torpor.  are higher than those  an  dead and w i l l b i a s  sometime d u r i n g t h e w i n t e r , i t s d e a t h w o u l d be  which  and  e s t i m a t e d t o be  early  fed  -71-  TABLE XXII.  The number of new adults and the number o f adults that permanently disappeared during the l a t e summer and f a l l o f 19°4 i n the high and low areas.  Low area new  High area lost  new  lost  July  1  6  8  5  August  7  6  6  6  12  10  1  5  October  6  4  2  2  November  2  7  28  33  September  Totals  No captures  17  18  -72-  reproductive season.  S a d l e i r (1965) has shown a c o r r e l a t i o n between onset of  the reproductive season, increased aggressiveness i n males and sudden decrease i n population density.  Healey (1966) has v e r i f i e d the c o r r e l a t i o n between  reproductive condition In males and Increased aggressiveness and has shown a negative c o r r e l a t i o n between aggressiveness and s u r v i v a l of juveniles.  Although  a large drop i n t o t a l numbers was not found In the spring In t h i s study both populations decreased  In density more r a p i d l y In the spring than over the  winter. the increase i n numbers of animals i n both areas from the spring of I964 t o the spring of 1965 may have been the result of study procedures.  Since  the system of trapping Included the use of bait i n a groove In front of the trap some food could have been c o l l e c t e d and stored by the animal before i t was  captured.  Bendell (1959) observed that an Increased food supply may have  increased numbers i n an island population of Peromyscus.  Since both popu-  l a t i o n s increased i n about the same proportion the cause would appear t o be either food provided by trapping or a general environmental or population phenomenon. Von Bloeker (1928 and 1932) noted high numbers of Perognathus longlmembrisg P. spinatus and P. b a i l e y i while trapping for specimens.  It  i s not known i f pocket mouse populations show c y c l i c fluctuations or occasional very high d e n s i t i e s as are observed  i n some mammals.  The evidence contributed  by Von Bloeker suggests, however that Perognathus populations may be l o c a l l y very dense, p o s s i b l y i n response t o r a i n f a l l . CONCLUSIONS 1.  Population density was negatively correlated with a l t i t u d e .  2.  High area adults and young and low area adults had  similar  s u r v i v a l rates, while low area young animals had s i g n i f i c a n t l y lower s u r v i v a l rates.  -73-  3.  O v e r w i n t e r s u r v i v a l i n a l l groups was b e t t e r t h a n s u r v i v a l a t  any o t h e r t i m e o f 4. groups  year.  C o n s i s t e n t l y low s u r v i v a l r a t e s were  a n d some i n s t a n c e s  of low r a t e s were a l s o  i n d i c a t e d low s u r v i v a l r a t e s or t h e onset 5. due t o  of  i n the  found i n t h e  found i n t h e  f a l l may b e a r t i f a c t s  spring in a l l  fall.  The  caused by  emigration  torpor.  The o b s e r v e d  increase  i n density  i n b o t h a r e a s may h a v e  e x p e r i m e n t a l methods o r a g e n e r a l c l i m a t i c o r p o p u l a t i o n  been  factor.  Torpor  The e x a m i n a t i o n o f t o r p o r i s  important because t h e a b i l i t y  to  reduce m e t a b o l i c r a t e and conserve b o t h food and w a t e r appears t o be a adaptation to  existence  the high areas i n t h i s toward longer periods  i n cold or dry habitats.  The c o l d e r environments  s t u d y may b e e x p e c t e d t o a c t of  major  as a s e l e c t i v e  of  pressure  torpor.  METHODS Observations 18 c u b i c  foot  on a c t i v i t y and t o r p o r were conducted i n a m o d i f i e d  refrigerator.  r e f r i g e r a t o r by replacing the differential  A constant stock  s e n s o r and s w i t c h .  t e m p e r a t u r e was m a i n t a i n e d i n t h e  c o n t r o l u n i t w i t h a Ranco 3 F f i x e d  Temperature and r e l a t i v e h u m i d i t y i n  the  r e f r i g e r a t o r w e r e r e c o r d e d w i t h a spring-^wound S e r d e x t h e r m o h u m o g r a p h . was c i r c u l a t e d p a s t  the c o o l i n g p l a t e , temperature  a n i m a l chambers w i t h a s m a l l f a n .  sensor,  recorder,  The n o r m a l i n t e r i o r l i g h t  of the  a t o r was r e p l a c e d w i t h two t w e n t y - f i v e w a t t b u l b s c o n t r o l l e d b y a n matic time switch.  The s h e l v e s  and refrigerIhter-  o f t h e r e f r i g e r a t o r were r e p l a c e d w i t h  c o n t a i n i n g t h e a c t i v i t y cages d e s c r i b e d below.  Polyetbyelene  Air  racks  f i l m w i t h an  -74-  armhole cold  was  taped  a i r during feeding The  5  cm  deep.  activity  A cage  of the dish. The  over t h e opening  The  and  o f the r e f r i g e r a t o r t o minimize  cages  o f g l a s s d i s h e s 16  consisted  cages were hung  supporting racks consisted  s c r e e n 10  from p i v o t s  each p i n t o d e t e c t  t h e cages balanced  cm  movement, a n d  so t h a t  1  o f sawdust  o f t h e cage  cm  adjustments,  d i d not  The  circuit  recorder.  The  t o be  animals  In t h e c o l o n y .  randomly hours  used  t o cages. and  i n the  The  observed  a t about  used  as t h e c r i t e r i o n  rate  o f g r e a t e r t h a n one  had  respiration  few  grains  rates  The  a  possible  The  nearly cages  of  microswitches  o f t h e cage  sensitivity volt  AC  of the  circuit  was  movement. a l l locomotory contained a side  system.  connected t o  adjusted t o run at 6  of the refrigerator  and  In t h e  experiments were s e l e c t e d  an inches  lighting  from g  animals were p l a c e d In t h e apparatus  at  started  renewed  1200, 1700  for torpor.  randomly  T h e y w e r e w e i g h e d t o t h e n e a r e s t 0.1  t h e r e c o r d e r was  were g i v e n a s u r p l u s o f m i l l e t , were a l s o  dish.  to the recorder.  Animals  0900  the  r e c o r d e r was  M i c r o s w i t c h e s on t h e d o o r  available  about  effect  of the  Movement o f t h e s a w d u s t t o o n e  m i c r o s w i t c h e s s w i t c h e d a 110  were a l s o connected  assigned  switch t o t r i p .  f o r bedding.  materially  E s t e r l i n e Angus e v e n t per hour.  deep  top  t h e bottom  indicated that  layer  high covered the  o f m o r e t h a n 1 cm.  Observations,  m o v e m e n t s b y t h e mouse c a u s e d t h e  and  stops at the sides  at the least  final  i n diameter  t h e cages p i v o t e d ,  h o r i z o n t a l and t h e m i c r o s w i t c h t r i p p e d after  cm  1 cm b e l o w t h e t o p  o f t h e p i n s on w h i c h  t h e c a g e s t o p r e v e n t v e r t i c a l movement were a d j u s t e d , and  of  observing animals.  made o f g a l v a n i z e d w i r e  microswitch next t o  loss  24  each day and  2000  hours at  later.  0900  hours.  The  hours.  inspiration per  o f l e s s t h a n one  second w h i l e t o r p i d  o r two  o f sawdust w e r e p l a c e d on t h e b a c k  The  a  animals  rate  was  respiration  animals at  inspirations per o f each  animals  Respiration  Thermoregulating animals had  and  5 C  5 seconds.  a n i m a l when i t was  A first  -75-  found t o be t o r p i d .  It was assumed that arousal had not taken place i f the  sawdust was s t i l l i n place when the animal was next observed.  At each  observation the state of each animal was recorded on the a c t i v i t y record. The a c t i v i t y records were analyzed by counting the number of twominute periods per hour i n which the animal was a c t i v e .  Periods o f torpor  were timed t o the nearest hour from the beginning of the f i r s t hour i n which the animal was not a c t i v e u n t i l the end o f the l a s t hour i n which the animal was not a c t i v e .  This period of i n a c t i v i t y was analyzed as torpor only i f  the animal was v i s u a l l y observed t o have a low r e s p i r a t i o n rate during the period. During the experiment the temperature was controlled at 5 ^ 1.5 The humidity varied between 40$ and 60$ and averaged about 55$.  C.  The l i g h t s  were on the same cycle as that i n the animal room, coming on at 0900 PST and going o f f at 0100  PST.  The experiment was run twice f o r 40 days, with the  animals weighed before and a f t e r , and the body temperatures o f the animals at the end of the experiment measured with an YSI telethermometer.  In each  experiment 6 high and 6 low animals were used. 3h the experiment t o determine the effect of a change i n photoperiod on the times of onset and end of torpor 12 low area animals were placed i n the r e f r i g e r a t o r under the same conditions as above except the dark period was s h i f t e d t o 0700 t o 1500  hours and the experiment was terminated  a f t e r 30 days.  RESULTS AND DISCUSSION Torpor i n the F i e l d Torpor, used here t o include hibernation, e s t i v a t i o n , and d a i l y torpor, can be investigated only t o a very l i m i t e d extent with trapping studies.  In t h i s study trap success (number animals captured/number animals  present) was calculated.  Low trap success during a  p a r t i c u l a r time of year  -76-  or  i n a p a r t i c u l a r class o f animal i s taken t o indicate lack o f surface  activity.,  It could be argued that trap success r e f l e c t s t r a p a b i l i t y rather  than surface a c t i v i t y  0  This p o s s i b i l i t y cannot be ruled out, but the high  t r a p success during summer, when food i s p l e n t i f u l , and low trap success i n spring and f a l l , when food i s less common, argue against i t .  The fact that  Scheffer (1938)$ working i n a d i f f e r e n t area with a d i f f e r e n t type o f trap and b a i t , found s i m i l a r low trap success i n the early spring and l a t e  fall  a l s o supports the idea that low trap success r e f l e c t s l i t t l e surface a c t i v i t y . Low surface a c t i v i t y may not be correlated with torpor, but torpor i n periods of low temperature and food supply appears t o be adaptive, while underground a c t i v i t y does not have such an obvious advantage.  Low trap success, however,  must be used as an i n d i c a t o r of torpor since no other f i e l d indication was available. Figure 11 shows trap success i n both high and low areas throughout the year.  The l a s t animals were captured i n the high area i n the l a s t week  of October, while the low area animals were active u n t i l the end of November. The a c t u a l end o f above-ground a c t i v i t y seems t o come only when the ground Is covered with snow.  The low area was trapped weekly with a few traps and  animals were captured each week u n t i l the second week o f December when snow fell.  Snow f e l l on the high area some time between the end o f October and  the t h i r d week o f November, when the area was trapped.  At that time the  snow was only about 10 cm deep but no animals were captured and no signs o f a c t i v i t y could be seen.  Scheffer (1938) states that between l a t e December  and early March a few animals may be captured i n sheltered s i t u a t i o n s . t h i s study the e a r l i e s t spring trapping was conducted i n l a t e A p r i l .  In At that  time both high and low area animals were active i n low numbers. Scheffer (1938), working i n southern Washington, found animals appearing by t h e middle o f March.  Scheffer*s data and extrapolation o f  -77-  100-,  50  o-  o-  H  f O/^  0.  Percent Trap Success  o  T  1  1  o  r  1  T  iow Y0Y« Adult o  1  1  100-,  o 50-J  o-2'  Y0Y# Adult O  T  T  r  r-^  r  T  1  1  1  1  1  lOO-i Total  50H  o  1 J  1 J  T A  1 S " 0  o  Ho  •  Female  O  ~i—-i—r~—i—i—i—i—i D  J  F  M  A  M  Months Figure  Male  P e r c e n t o f a n i m a l s known t o b e a l i v e t h a t w e r e c a p t u r e d t h r o u g h o u t I964 a n d 1965*  J  -78-  curves i n Figure 11  suggest that time of emergence i n the southern Okanagan  would be l a t e March of early A p r i l . Figure 11c  shows that i n both high and low areas young animals were  a c t i v e i n greater proportions i n the l a t e f a l l than were the adults.  This  probably once again r e f l e c t s the fact that t o survive the winter the young animals must excavate a burrow and store a large amount of food. Figure 11  suggests that males may  stay a c t i v e longer i n the  and become active e a r l i e r i n the spring than the females. not s i g n i f i c a n t . 1921,  fall  The difference i s  Scheffer's (1938) data show a very large d i f f e r e n c e ( A p r i l  67 males - 28 females, A p r i l 1924,  40 males - 4 females).  76 males- - 4 females, March  1924,  Hoffmeister (1964), i n analyzing records o f museum  specimens o f s i x species of Perognathus from the Southwest U.S., from January through May  found that  a l l s i x species shewed sex r a t i o s i n favor of males.  The percentages found varied from 100$  males t o 59.4$ males.  He suggests  that females may be i n torpor, rearing young, or trap-shy at t h i s time of year.  Results from t h i s study and from Scheffer's (1938) on reproduction i n  P. parvus suggest that, at least i n the north, the females are not yet reproductiveo  Consistent results i n s p i t e of the d i v e r s i t y of trapping  methods used i n these three studies make the theory of trap-shyness likely.  less  The early emergence of male Perognathus may be a s i m i l a r phenomenon  t o the e a r l i e r reproductive a c t i v i t y i n many male mammals ( A s d e l l , 1965). The Yearly Weight Cycle Figure 12 parvus.  shows the y e a r l y weight cycle i n d i f f e r e n t groups of P.  Because of small and v a r i a b l e sample size and trapping of d i f f e r e n t  individuals each month, i t was not considered possible t o analyze the data statistically.  Several trends are suggested by the d i s t r i b u t i o n of the means  of d i f f e r e n t groups.  There i s a general Increase i n weight i n a l l groups  30-i  Month Figure 12»  Mean weights of d i f f e r e n t age and sex groups of animals throughout 1964-1965* The l i n e i s f i t t e d by eye t o the mean o f means Boxes enclose data which are suspect because of low numbers. 0  -80-  f r o m May this  o f the animals  weights  of the small  averages  larger out  and  that  heavier  were born  earlier  entry  October,  The  first  out  of torpor  an  the  out  heavier  somewhere b e t w e e n  survival  o v e r w i n t e r comes  The  Characteristics The word  vation.  T o r p o r does  estivation.  5 and  metabolic minimal  rate,  levels",  had  falls and  valid  The  may  be  due  average  indicated  more t i m e t o s t o r e  a month. at about  figures place  from s t o r e d  Lyman  food delay hibernation. early  f o r t h e group.  indication  thin  that  food.  have o c c u r r e d as  In  as  April  o f t h e average  These  weight.  have been  objections  mean  5$, s h o u l d be c o n s i d e r e d  g a i n between August  which  to the  Wade ( 1 9 3 0 ) p o i n t e d  w h e n some o f t h e a n i m a l s may  for nearly  26%.  and  October  the percent weight  means t h a t  most  of the  observed i n gain  for  energy f o r  food rather than f a t .  of Torpor i s used throughout (Bartholomew  discussions not  any  f o r May,  These  i s defined  t o a low  and  p a r t l y because  level  other physiologic  t h e words become  i t has  Cade, 1 9 5 7 ) and  of the definitions  imply a d i f f e r e n t  I f hibernation  body temperature  had  This  prevented from s t o r i n g  loss,  "torpor"  avoids f r u i t l e s s  maximum  t e n d t o be t h e animals  h e a v i e r a n i m a l s may  a p p l i e d b e f o r e t o Perognathus it  animals would  maximum w e i g h t 26%.  The  of  tended t o h i b e r n a t e before  d e c r e a s i n g t h e average weight  a n i m a l was  reasons.  earlier.  squirrels  s e a s o n and  are  magnitude  have been determined.  from October.  ground  gaining weight  The  not  into torpor  that, hamsters  weights  and  for several  The  o f a n i m a l s c a p t u r e d i n N o v e m b e r a r e much b e l o w  samples  overwinter weight  adult  may  are too small t o give  valid  minimum.  torpor  and  i n the  therefore  samples  the  samples  into t o r p o r by  the  fall  animals going  larger  (1954) pointed Early  i n the  fat Thirteen-lined The  a decrease over w i n t e r .  t o determine  of the larger  animals.  that  followed by  decrease i s d i f f i c u l t  weight  the  t o October  been  partly  of hibernation  and  because esti-  phenomenon f r o m h i b e r n a t i o n  as " a p e r i o d i c  phenomenon  a p p r o x i m a t i n g ambient, functions  synonomous.  fall  to  and  and  i n which heart  correspondingly  rate,  -81-  The general c h a r a c t e r i s t i c s of torpor i n P. parvus are s i m i l a r t o those summarized by Cade (1964) f o r other species of Perognathus.  P. parvus  captured i n l i v e - t r a p s have occasionally been observed t o enter torpor during a l l months from A p r i l t o November.  It enters torpor spontaneously i n  the laboratory with food a v a i l a b l e at temperatures from 20 C t o below 5 C. The lowest r e c t a l temperature observed i n a t o r p i d animal was 2 C at an environmental temperature of 0 C, the highest, 21 C at an environmental temperature of 20 C.  The normal body temperature varies between 34 arid 37 C  and can be maintained at t h i s l e v e l i n d e f i n i t e l y at 5 C i f food i s a v a i l a b l e . At  5 C the shortest period of torpor observed was 3 hours, the longest was  168 hours and the average length of 241 periods of torpor was 46 hours. Warming rates and behavior during arousal from torpor were s i m i l a r t o those observed i n P. longimembris by Bartholomew and Cade (1957). Torpor i n the Laboratory Figure 13 shows the a c t i v i t y cycle i n high and low animals at 5 C. The peak i n a c t i v i t y occurred shortly a f t e r the dark period started. A c t i v i t y then decreased during the night and reached a minimum a f t e r the s t a r t of the l i g h t period.  These data f i t Scheffer*s observations (1938)  that P. parvus i n the f i e l d are more active i n the early night than toward dawn.  Scheffer states that he very occasionally observed a pocket mouse  above ground during the day, but I have never seen one.  It appears that P.  parvus i s s t r i c t l y a nocturnal animal with most o f i t s a c t i v i t y occurring i n the early  part of the night. At  groups.  5 C amount of a c t i v i t y decreased with time i n both high and low  This was seen i n both a shortening of the a c t i v i t y period and a  decrease i n the peak a c t i v i t y .  This i s p a r t i a l l y due t o the fact that with  food available P. parvus does not have a d i u r n a l cycle of t o r p i d i t y as observed (Tucker, 1962) i n P. c a l i f o r n i c u s with decreased rations.  During  -82-  1200  1800  2400  Number  o f 2 minute p e r i o d s p e r hour i n which  took p l a c e different is  i n captive high lengths  and low a r e a  o f e x p o s u r e t o 5 C.  shown b y t h e h o r i z o n t a l  bar  1200  w^mm—^mm  HOUR F i g u r e 13o  0600  0  activity  animals  after  The dark  period  -83-  the  later part  dark p e r i o d .  o f t h e e x p e r i m e n t many o f t h e a n i m a l s w e r e t o r p i d t h r o u g h t h e T h o s e t h a t w e r e a c t i v e showed  when t h e l i g h t s went low  temperature, Figure  the  animals  the  dark phase  off.  since 14  This  may  activity  represent  u s e s more  shows t h e t i m e s  observed.  Both high  (1962)  period  o f t h e c y c l e and were aroused  phase.  h i s animals  T h e same t e n d e n c y  remain  entrance forward  i n t o and e x i t 14)°  (Figure  This  i n timing  noise,  i n the laboratory.  is  can a t least The  greater  i n t h e high  The  percent  the  experiment  be modified  average length  from t h e beginning  phase.  during  area  o f t i m e spent  animals  6 hours  the following  and i s g r e a t e r  ( F i g u r e 15a) area  and t h e i n c r e a s e The  i n length  hypothesized  t o occur  stimulus,  such  advantage o f w i n t e r  torpidity  as  i n timing  torpor  f o r the timing  of  photoperiod. Table  XXIII,  It i s also  increases  significantly  twenty days o f t h e experiment. also increases  animals.  Figure  o f torpor periods  of torpor periods  as an a d a p t a t i o n  of  a b o u t t h e same amount  o f torpor period with  difference i n length  may  forward t h e peak t i m e s  o f photoperiod  t o t h e end.  i n high  light  animals are r e a c t i n g t o photo-  forthe first  i n torpor  t h e dark  except t h e animals  of the torpor period,  o f t h e experiment  during  phases.  b y a change i n  a n o t h e r method t h e d i f f e r e n c e i n l e n g t h  areas  was  the light  r a t h e r t h a n t o some o t h e r effect  from t o r p o r i n torpor  during  are also shifted  A direct  quietly.  t o enter  not n e c e s s a r i l y i n d i c a t e d b u t t h e mechanism r e s p o n s i b l e  torpor  by  light  demonstrates t h a t  torpor periods  sitting  torpor  i n P. p a r v u s  i s shifted  from t o r p o r  period  from t o r p o r  one o r more  When t h e d a r k p e r i o d  entered  of activity  acclimation t o  i n t o and e x i t  active during  also  i s apparent  i n torpor throughout  energy t h a n  and low a n i m a l s t e n d  Tucker  burst  a behavioral  o f entrance  o f t h e c y c l e and become found t h a t  a short-lived  Illustrates  between t h e two  increasing time at 5  C.  i s the difference that  t o the different  i s usually considered  15b  throughout  environments.  t o be an a d a p t a t i o n  to  The  -84-  25 -,  1200  Figure  14<.  Thet o t a l left  1800  number  torpor  period  of high  during  a t 5 Co  12o  0600  and lowarea animals that  different  T h e number  e x p e r i m e n t was 24, was  2400  hours  entered and  o f t h e day during  o f animals  i n t h e normal  i n t h e delayed photoperiod  a 40 d a y photoperiod  experiment  i t  -85-  TABLE X X I I I o  Length o f torpor periods, In hours, during different 10 day periods f o r high and low animals. indicates P'S .05. 3  Day  Low Area Number Mean  High Area Mean Number  T  1-9  34  31.6  4.46  10-19  25  44.3  10.2  20-29  33  51.9  30-39  25  Total  117  36.5  34  59.8  32  0.14  52.1  28  47.0  1.61  49.3  30  43.3  1.59  49.1  114  s  s  -36-  1  1  1-2  1  u -j  1  2  1  9-10  1  3  1  |  4  1  5  # Figure 15<>  19-20  6  Times  1  7  1  8  1  1  29-30  39-40  1  9  1  10  1  11  1  12-  In T o r p o r  A Percentage of time spend i n torpor i n high and low area animals a f t e r d i f f e r e n t lengths o f time at 5 C o B o Mean length of torpor period i n high and low area animals a f t e r d i f f e r e n t numbers o f torpor p e r i o d s The low area animals entered t h e i r longest period of torpor on day 18„6 (13-31) and the high area animals entered t h e i r longest period of torpor on day lBok (11-33)° 0  0  -87-  conserve  energy d u r i n g  of longer a  torpor  period  torpor periods c y c l e i s spent  a t 15  arouses  periods  arises mum  C, a t o t a l  torpor  from t h i s  length  i n 20 t o 30 temperature. periods  Kayser  i n ground  decrease with  periods  o f energy w i l l  iss  squirrels  at least  result  has noted  i n P.  even i f t h e animal From t h i s  i s t h e factor that  limits  that t h e maxi-  a few days? o f t o r p o r p e r i o d t o a maximum o f t h e a n i m a l t o t h e low  i n early winter,  i n the length  followed  The v a r i a t i o n  a f t e r t h e maximum i s r e a c h e d may r e p r e s e n t  o f torpor  by a steady  s t a t e and  i n lengths  of torpor  a steady  state  with  i n d i v i d u a l d i f f e r e n c e s b e c o m i n g m o r e a p p a r e n t , o r t h e y may r e p r e s e n t actual decrease  i n t h e length  the  length  the  percentage o f time  represent  o f torpor periods  a second phase  of the torpor period the  spent  amount  f o r a l l animals.  has ceased t o increase, continues  and p o s s i b l y  t o increase.  o f a c c l i m a t i o n t o low temperature  and so conserve  energy  an  Even  after  decreased,  This  may  i n which t h e length  i s a t i t s maximum a n d t h e o n l y m e t h o d l e f t  o f time i n torpor  of the periods  o f torpor periods  i n torpor  i t can  energy, and t h a t question  an increase  t h e approach o f s p r i n g .  torpor  The i n t e r e s t i n g  represents a c c l i m a t i o n  (1965)  a longer  i n t h e sense o f saving  what  The advantage  o f energy spent i n  i t s minimum t e m p e r a t u r e .  i n t h e average length  days p r o b a b l y  1965b),  T u c k e r a l s o showed t h a t saving  supply.  proportion  (Tucker,  o f torpor t o only  increase  i s i n short  since a high  s a v e more e n e r g y .  relationship  o f periods  food  arousal  i s adaptive  of torpor  The  a  during  immediately upon r e a c h i n g  stated that  long  i nwhich  i sthat,  c o n s e r v e s more e n e r g y .  ealifornicus  be  a time  t o increase  i s t o decrease t h e length  of activity.  CONCLUSIONS 1. low  area  High area  animals.  a n i m a l s went  into torpor  earlier  i nthe fall  than  -88-  2.  Adults i n both high and low areas appeared t o go into torpor  e a r l i e r i n the f a l l than young-of-the-year animals. 3.  Males may have gone into torpor l a t e r and come out e a r l i e r than  4.  Animals tended t o gain weight from May t o October.  females. The average  weight loss over winter appears t o be about 5$. 5.  Under laboratory conditions P. parvus was a s t r i c t l y nocturnal  animal with a peak i n a c t i v i t y occurring s h o r t l y a f t e r dark.  Activity  patterns of both groups of animals were s i m i l a r . 6.  With continued exposure t o a temperature of 5 C there was a  trend t o lower average a c t i v i t y and a shorter period of peak a c t i v i t y i n both groups. 7.  Both groups of animals tended t o enter torpor during the dark  period and arouse from torpor during the l i g h t period. 8.  High area animals had s i g n i f i c a n t l y longer torpor periods  during time periods day 1-9 and 10-19 than low area animals.  There was no  s i g n i f i c a n t difference during time periods 20-29 and 30-39. 9.  Percent of time i n torpor increased during the course of the  experiments and apparently l e v e l l e d o f f at about 60$.  High area animals  consistently spent a higher percent of time i n torpor. 10  o  The mean length of torpor periods increased from torpor  periods 1-6 and then showed a decreasing trend. period was reached on day 18. periods than low area animals.  The maximum length of torpor  High area animals showed longer average torpor  -89-  Water  Balance  A d a p t a t i o n s t o c o n s e r v e w a t e r a r e one in  the  Heteromyidae.  species t o inhabit  They p l a y an  t h e drier' areas  important o f North  the different  populations  h a b i t a t s may  importance  and  moist  role  specializations  i n the a b i l i t y  America.  t o minimize water l o s s through f r o m d r y and  o f t h e major  A  channels  of these  comparison  of  ability  in individuals  give indications  of the  of relative  s u s c e p t i b i l i t y t o change, o f t h e u n d e r l y i n g mechanisms.  METHODS A h u m i d i t y chamber o f p o l y e t h y l e n e f i l m 0.6  m w i d e was  for the for  lower  c o n s t r u c t e d i n t h e a n i m a l room. front which  c o u l d be  access t o the animals.  A  flow  enough t o p e r m i t  The a  A  maintained  c h a m b e r was  not  coarse  sawdust.  Temperature and  The  of fresh  airtight  jars  laid  seal or  seams a n d when  the  did restrict  air  Shallow  metal  covered the bottom o f  on t h e i r  The  animals  sides  the  were  and bedded  j a r c o v e r s were r e p l a c e d w i t h welded w i r e  r e l a t i v e humidity  opened the  but  and  except  a i r leaked into  maintained.  solutions  m high  seams w e r e w e l d e d  a i r over t h e pans.  wide-mouth g a l l o n  l o n g , 0.6  f o r an a i r t i g h t  constant humidity t o be  small fan circulated I n 24  The  m  f a n , I n some o f t h e  pans c o n t a i n i n g t h e humidity c o n t r o l l i n g chamber.  up  s m a l l amount  chamber t h r o u g h h o l e s b e h i n d t h e animals were weighed.  rolled  1.2  with  mesh.  i n t h e chamber were r e c o r d e d w i t h  a  Serdex  t h ermohumograph. The (Winston saturated  saturated salt  and B a t e s ,  solutions, with  constant  relative  NaCl  Zn(NCg).  and  I960).  20  m e t h o d o f h u m i d i t y c o n t r o l was  T h i s method t a k e s advantage extra  humidity At  solution  salts,  of certain  salts w i l l  In a c o n f i n e d volume o f a i r .  C these  salts  of the  The  fact  used that  maintain salts  m a i n t a i n h u m i d i t i e s o f 76$  a  used and  were 42$  -90-  r e s p e c t i v e l y (Winston and Bates, i 9 6 0 ) .  Throughout the course of the experi-  ment r e l a t i v e humidity varied l e s s than i k% from the desired l e v e l and temperature varied l e s s than i 2 C. In the second set of experiments animals were maintained i n 15 cm diameter cages with wire mesh bottoms t o determine f e c a l and urinary water loss and water intake.  These cages were exposed t o room conditions which  were 60 * 6% r e l a t i v e humidity and 20 ± 2 C„ Urine samples were c o l l e c t e d f o r the determination of osmotic concentration by p l a c i n g a glass dish containing p a r a f f i n o i l below each cage.  After 24 hours uncontaminated samples of urine were c o l l e c t e d i n  c a p i l l a r y tubes and frozen on dry i c e . Osmotic concentrations were determined with a Ramsey-Brown freezing point apparatus (Ramsey and Brown, 1955). D a i l y food intake, and dry weight of urine and feces were determined. A weighed quantity of food was presented t o each animal and a preweighed funnel-shaped f i l t e r paper was placed below each cage.  Dropped food and  feces r o l l e d down the f i l t e r paper, through a small hole i n i t s center and i n t o a c o l l e c t i n g dish below. and weighed.  Food and f e c a l material were then separated  Urine was absorbed by the f i l t e r paper.  papers were dried at 100 C f o r 24 hours and weighed.  Feces and f i l t e r Dry weight was then  calculated. Water content of feces was determined by c o l l e c t i n g f e c a l p e l l e t s immediately a f t e r defecation, weighing, drying f o r 24 hours at 100 C and reweighing them.  Water content of p e a r l barley and l e t t u c e was determined.  T a i l blood was c o l l e c t e d i n a heparinized c a p i l l a r y tube, and centrifuged.  The plasma was then c o l l e c t e d and osmotic pressures were  determined as f o r urine. Evaporative water loss was determined i n a constant pressure closed  -91-  system  r e s p i r o m e t e r a t 20  t h e a n i m a l chamber was  ± 0.1  C and a r e l a t i v e h u m i d i t y  c i r c u l a t e d through  a U tube  o f 0$.  Immersed  A i r from  i n alcohol  c o o l e d b y d r y i c e , a l i t h i u m h y d r o x i d e CO2 a b s o r p t i o n c o l u m n , a n o t h e r tube  i n cold  alcohol,  t h e a n i m a l chamber. and  t h e s y s t e m was  for  one-half hour.  it  was  Animals  applicable  c h a n g e was  Weight  of pearl barley  The  calculated.  equilibrated  C o n t r o l a n i m a l s w e r e g i v e n a s m a l l amount  f o r both  experiments.  as a percent  to the  of lettuce  Animals  t r e a t m e n t s , and numbers  were a s s i g n e d randomly t o  of original  0.1  g.  Weight  weight.  DISCUSSION Loss results  o f t h e weight  f o r percent  loss  experiment  o f o r i g i n a l weight  a three-way a n a l y s i s  of variance.  a r e shown i n F i g u r e  on t h e t e n t h d a y w e r e  The r e s u l t s  of this test  16.  submitted a r e shown i n  XXV. Throughout  gained  f e d an excess  A l l animals were weighed d a i l y t o t h e n e a r e s t  The values  c c o f oxygen.  and m e t a b o l i c r a t e were  shows t h e e x p e r i m e n t a l g r o u p s ,  calculated  R E S U L T S AND  50  and  water.  T a b l e XXIV  treatments.  into  equilibrate  U tubes were then p l a c e d i n t h e system  and water l o s s  conditions.  i n t h e groups  and f i n a l l y back  w e r e p l a c e d i n t h e chamber o v e r p a r a f f i n o i l  Pre-weighed  animals were  daily t o provide  Table  coil  allowed t o operate u n t i l t h e animal had used  All  to  equilibration  c l o s e d , p l a c e d i n o p e r a t i o n and a l l o w e d t o  U t u b e s were weighed  The  a temperature  U  t h e course o f t h e experiment  a s m a l l amount  amounts o f w e i g h t . controls  o f weight  a l l of the control  while a l l o f t h e experimentals lost  groups varying  The g r o s s d i f f e r e n c e between t h e e x p e r i m e n t a l s and t h e  i s significant  at a high  level  ( T a b l e XXV).  The gross  between t h e h i g h and low p o p u l a t i o n s i s a l s o s i g n i f i c a n t  difference  ( T a b l e XXV)  while  TABLE XXI?.  Experimental  groups,  experiments. to  the  weighed  Day..  .  •  1  The  second set daily  2  3  for  treatments  operations  aridnumbers  carried  of  experiments.  14  days.  4  but  Animals  5  for  both  on days  6  in the  1-10  sets  of  apply  first  set  7  only were  8  9  10  Experimental groups High area animals experimental (no water)  N =  12  Equilibration  early  _ late  period High  area  control water)  animals  Urine  Food  Wet  Urine  Food  Wet  collec-  feces  feces  collec-  feces  feces  collec-  ted  urine  ted  paraffin  collec-  water  ted  content  (given N =  12 .  A l l  ted  and  in  and  collec-  animals in  Low a r e a a n i m a l s experimental (no water)  N =  12  given  paraffin oil  control water)  animals (given N =  12  o i l  urine  ted.  collecBlood  on  ted  on collec-  water Low a r e a  for  f i l t e r  of  f i l t e r ted.  paper  feces  paper  Evaporative water loss determined  looPercent Of Original Weight  90'"•A.  -76%  -A  -42%  80-  , None Low o  Water •  High A  A  T  T"  T  4  2  6  Figure  16.  Percentage o f o r i g i n a l weight high  and  exposed  low  areas given  to different  Days  a f t e r time  different  humidities.  —-A-  10  8 In animals  amounts o f w a t e r  - A--  from and  the  A--  12  ~A-.  14  -94-  T A B L E XX7.  Comparison  F value  Significant A  R e s u l t s o f a 3-way a n a l y s i s o f v a r i a n c e o f p e r c e n t a g e o f o r i g i n a l w e i g h t a f t e r 10 d a y s I n h i g h a n d l o w p o p u l a t i o n s o f a n i m a l s ( A ) ; d e p r i v e d o f w a t e r and g i v e n w a t e r , ( B ) j a t 42$ a n d 76$ r e l a t i v e h u m i d i t y , ( C ) ; and a t e m p e r a t u r e o f 20 C. A l l animals were f e d an excess of p e a r l barley equilibrated t o the humidity i n question. T h e b a s i c N was 12.  High-low  Water no.  42-76  A  B  C  6.17  3 5.55  1.86  £.05  £.001  ^.20  AB  BC  . 48  5.63  ^.05  AC  .97  ABC  . 65  -95-  the effect of humidity f a l l s short of the usual l e v e l o f s i g n i f i c a n c e . The only s i g n i f i c a n t i n t e r a c t i o n i s between animals given water and those not and between high and low humidity.  This indicates that the  combination of low water Intake with low humidity produced a s i g n i f i c a n t l y d i f f e r e n t response i n animals than high water intake and high humidity.  This  i s the effect that would be expected since weight loss i s dependent on the balance between water intake and water l o s s . The difference between high and low populations seen i n Figure 16 i s i n the d i r e c t i o n expected on the basis of the environment. humidity Is apparent and i s In the d i r e c t i o n expected.  The effect o f  Examination o f the  curves f o r animals deprived of water show that the curves could be considered t o be made up o f two parts.  The f i r s t part of the curve shows a steep decline  followed by a slower decline, a l e v e l l i n g o f f or an increase.  This i s seen  most c l e a r l y i n the curves f o r the high area animals, where the i n f l e c t i o n point i s near the fourth day.  In the low area animals the i n f l e c t i o n point,  i f present, i s i n the f i r s t or second day.  The i n f l e c t i o n point could be  considered the time at which the animal a c t i v e l y begins t o conserve water. Evidence presented t o t h i s point indicates that by the tenth day high area animals had l o s t more weight than low area animals, animals deprived of water had l o s t more weight than animals given water and animals at a low humidity deprived of water l o s t more weight than would be predicted from humidity or water deprivation curves alone.  The weight loss curves, a f t e r  the i n i t i a l period of steep decline, can be examined t o determine i f the animals deprived of water and exposed t o a r e l a t i v e humidity of 76$ were l o s i n g weight and i f the high and low area animals at 42$ were l o s i n g weight at d i f f e r e n t rates. Figure 17 presents the regression analysis o f the weight loss  100  Figure 17.  Regression of percent of o r i g i n a l weight on time f o r high and low area water-deprived animals at 42 and 76$ humidity. Confidence intervals ( P - .05) are shewn f o r the 76$ humidity slopes. Calculated t for the comparison of high and low area animals at 42$ humidity equals 0.0047 with 71 degrees of freedom.  -97-  curves from day 4 t o day 14«  The low area animals at 76$ humidity show a  rate of change In weight that 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 zero. They were not gaining or losing weight.  The high area animals at 76$ show  a rate of change i n weight that i s s i g n i f i c a n t l y greater than zero. were gaining weight.  They  Both groups of animals at 42$ humidity were l o s i n g  weight but the difference between them i s not s i g n i f i c a n t . It appears that the animals at 76$ humidity were i n neutral or p o s i t i v e water balance and could be expected t o remain so I n d e f i n i t e l y . The animals at 42$ humidity were i n negative water balance and show no signs of decreasing t h e i r rate of water l o s s .  There i s no reason t o believe  that at 42$ r e l a t i v e humidity the animals would be able t o avoid eventual death.  On t h i s basis i t appears that the humidity below which p o s i t i v e  water balance cannot be maintained l i e s somewhere between 42 and  76$.  The difference i n amount of weight lost between high and low area animals was due t o a more rapid response on the part o f the low area animals.  As discussed before, the i n f l e c t i o n point i n the weight loss  curves f o r the high area animals i s near the fourth day.  In the low area  animals i t i s on the f i r s t or second day. Schmidt-Nielsen (1964) summarizes extensive work on water balance i n the kangaroo rat (Dipodomys).  He found, under conditions comparable t o  t h i s study, that kangaroo rats from Arizona could maintain p o s i t i v e water balance down t o a r e l a t i v e humidity of about 10$ brated p e a r l barley.  at 25 C when fed e q u i l i -  The higher temperature In Schmidt-Nielsen's study would  mean that the absolute humidity, which i s the parameter which influences pulmonary water l o s s , would be higher than i t would at 10$ at 20 G.  r e l a t i v e humidity  This means that the difference between r e s u l t s of the studies are  not as great as indicated.  -98-  Th e second phase of t h i s experiment was designed t o measure and compare water intake and loss through the d i f f e r e n t routes. design i s shown i n Table XXIV.  The experimental  The basic comparisons made were between high  and low area animals deprived of and given water.  Time since water depri-  vation was also included as a factor wherever possible. Percent weight loss was measured i n t h i s experiment as an i n d i cator of water balance.  The weight loss curves (Figure 18a) are complicated  by the fact that the controls d i d not maintain t h e i r weight.  This weight  loss was probably due t o experimental conditions such as confinement t o a small cage or lack o f comfort when placed on a screen mesh f l o o r .  The  effect of these conditions was greater on high area animals judged by the greater weight loss before water deprivation and the higher rate of weight loss i n high area controls (Figure 18b). High area water-deprived animals i n t h i s experiment l o s t cantly more weight than the low area animals (Tables XXVI, XXVH).  signifiThis  result i s s i m i l a r t o the r e s u l t of the p r i o r experiment and was due t o the same more rapid response t o water deprivation i n the low area animals.  In  t h i s case lower response t o other experimental conditions i n the low area animals may have contributed t o the e f f e c t s .  A f t e r water deprivation,  however, the high area animals l o s t water at a lower r a t e (Figure 18b) than the low area animals. This finding may be comparable t o the results from the p r i o r experiment where at 76$ humidity the high area animals, t o increase t h e i r weight, must have been l o s i n g l e s s water than the low area animals, which were merely maintaining t h e i r weight.  This would imply that In these two  situations the high area animals were expending a greater e f f o r t t o r e t a i n water than were the low area animals.  The fact that weight loss rates at  80 —'  T  3  F i g u r e 18.  T  5  7  A. Percent o f o r i g i n a l weight remaining a f t e r time i n h i g h and low a r e a animals, g i v e n and d e p r i v e d o f water. B. R e g r e s s i o n s o f percent o f o r i g i n a l weight on t i m e . The s l o p e s o f t h e w a t e r d e p r i v e d groups a r e d i f f e r e n t at t h e .05 l e v e l ( t = 2.20, 136 degrees o f freedom), as a r e t h e s l o p e s o f t h e groups g i v e n w a t e r  at t h e .02 l e v e l ( t = 2.^2).  -100-  TABLE XXVI.  Calculated F values f o r analyses of variance conducted on results o f the second group o f experiments. Degrees o f freedom i n the numerator equal 1 except where noted ( ) . Degrees o f freedom i n the denominator equal 36 i n the twoway analyses and 7 2 i n the three-way except f o r percent weight loss where there are 252 degrees o f freedom i n the denominator. The number o f observations i n each basic group i s 10 (N = 10). Significance at .05 i s shown by . s  A High-Low Pop.  B Water or not  C Time  5.17  0.15  10.14  8.38s  7.89s  2.54  0.80  38.08  0.09  34.03s  0.33  0.82  0.72  26.40  7.47s  1.13  0.00  1.38  0.00  2.00  2.44  2.85  2.34  2.48  6.07s  0.79  2.45  1.24  A-B Inter.  B-C Inter.  A-C Inter.  A-B-C Inter.  0.24 (6)  23.19s (6)  30.04s (6)  15.25s  0.87  1.95  15.10s  0.31  0.77  11.60 3  0.24  O.34  0.21  0.27  0.27  0.14  0.00  Starting weight  0.1L  Percent o f  o r i g i n a l wt.  8.50s (6)  42.53  Plasma Osmotic Pressure  0.90  Urine-Plasma Ratio  0.14  s  Urine Osmotic Pressure Urinary water l o s s per day  s  Fecal percent water Fecal water l o s s per day Evaporative water loss Metabolic Rate Water intake i n lettuce per day Water day i n foodintake per  0.02  15.32s  0,08  O.56  11.90s  0.23  9.39s  3.08  7.47s  1.30  -101-  TABLE XXVII.  Means and standard error o f the means f o r the results o f the second group o f experiments. N i n a l l cases equals 10.  High Area Given Water  High Area No Water  Low Area Given Water  Low Area No Water  18.09*0.49  17.34* *80  19.90*0*98  19.90±1.34  95.31*1.66 87.38*3.32  95.66*1.30 84.60*1.90  97.16*1.34 91.06*2.59  97.25*1.39 84.76*2.28  297.6*10.7  319.5*14.4  281.5*12.4  275.2*16.3  Urine-Plasma Ratio  6.16*1.22  12.46*0.92  6.72*1.21  13.81*2.78  Urine Osmotic ' E Pressure (Osmol) L  2.77*0.39 1.71*0.31  2.69*0.32 3.90*0.28  2.54*0.28 1.68*0.26  3.45*0.31 3.67*0.24  Starting weight (g) Percent o f o r i g i n a l wt.  E L  Plasma Osmotic pressure (Osmol)  Urinary Water E Loss per Day (mg) L  259.9*26 556.7*118  198.8*28 151.4*29  287.5*48 748.5*119  205.0*21 120.5*14  Fecal Percent Water  53.40*1.80 52.01i2.87  41.82*2.76 44.06*2.97  45.32*2.24 45.61*4.06  49.83*3.86 50.62*1.67  108.6*19.3 76.2*20.8  76.0*16.1 57.2*10.7  114.8*15.0 92.2*22.4  95.6*18.6 85.7*12.0  E L  Fecal Water E Loss per Day (mg) L Evaporative Water Loss (mg H20/ml Q2) Evaporative Water Loss per Hour (mg) Metabolic Rate (ml C^/gm/hour)  0.68*0.003  58.25*3.48  5.61*0.31  Water intake i n E Lettuce per Day (mg) L  186.0*111.0 254.0*93.3  Water intake i n E Food per Day (mg) L  761.7*48.1 589.7*149.0  0.58*0,003  47.40*3.13  5.42*0.51  0.66*0.002  0.68*0.002  56.01*3.81  65.24*1.30  6.63*1.60  4.86*0.39  242.0*69.3 226.0*67.7 981.7*70.5 968.3*122.0  2165.8*465.0 991.0*135.7  1297.2*235.4 872.6*195.8  -102-  42$ humidity were not d i f f e r e n t Indicates that, at least In t h i s s i t u a t i o n , low area animals were as capable of maintaining t h e i r weight as high area animals.  I f t h i s i n t e r p r e t a t i o n of lack o f maximum response on the part of  low area animals i s correct i t indicates that these animals are not as s e n s i t i v e t o weight, or water, loss as are high area animals. Plasma Osmotic Pressures Evidence f o r greater s e n s i t i v i t y of high area animals t o water deprivation i s found i n the increased osmotic pressure of the plasma o f these animals (Figure 19). group.  This i s t r u e p a r t i c u l a r l y i n the water-deprived  S i m i l a r l y high osmotic pressures have been found i n plasma from  severely water-deprived grasshopper mice (Schmidt-Nielsen and Haines, I964) and Pack rats (Neotoma albigula) (B. Schmidt-Nielsen et a l . , 1948).  In these  cases the elevated osmotic pressures were due t o higher plasma urea.  Water-  deprived kangaroo rats d i d not show elevated plasma urea or osmotic pressure l e v e l s (K. Shmidt-Nielsen, I964).  The references c i t e d above indicate that  only i n very greatly dehydrated animals do the plasma osmotic pressures increase.  The high area animals, therefore, even though they had lost  little  more weight at the time blood was c o l l e c t e d , were showing signs of severe dehydration. The urine.plasma r a t i o s (Figure 19) were the same i n the two populations, but a highly s i g n i f i c a n t difference was  found between water-  deprived animals and those given water (Tables XXVI, XXVII).  Both experi-  mental groups were apparently reacting t o dehydration very strongly by forming a much more concentrated urine than the c o n t r o l groups.  The urine:  plasma r a t i o s f o r water-deprived animals are s i m i l a r t o those summarized by Schmidt-Nielsen (I964) f o r kangaroo r a t s and other desert animals.  -103-  0.320 - ,  Osmotic  ©  Pressure  14-,  ©  OSMOLES  0.300 H  12-^  URINE PLASMA RATIO  10  H  8H  0.280 H  A I  LATE  F i g u r e 19.  LATE  A . Mean p l a s m a o s m o t i c plasma area  ratios  animals  pressures,  o f osmotic deprived  pressures  o f and given  a n d (B).  Water •  None  High  A  A  urine/  o f high water.  Low  and low  o  -10.4-  Urinary Water Loss  *  Urinary osmotic pressures (Figure 20) shewed a s i g n i f i c a n t d i f f e r e n c e between animals deprived of water and those given water (Tables XXVI, XXVIl)o  The d i f f e r e n c e became greater with time through an increase  i n concentration of urine i n water-deprived animals and a decrease i n controls.  The increase i n high area water-deprived animals was greater  than i n the low area water-deprived animals, p r i m a r i l y due t o a lower early value.  This may be the cause o f the e a r l i e r i n f l e c t i o n point i n the weight  loss curves o f low area animals as was observed e a r l i e r . T o t a l urinary water loss per day (Figure 20) showed the same pattern of response.  As i n urine osmolarity t h e only s i g n i f i c a n t difference  was between water-deprived animals and c o n t r o l s .  The difference becomes  s i g n i f i c a n t l y greater with time (Tables XXVI, XXVII). Fecal Water Loss The only s i g n i f i c a n t finding i n water content o f feces (Figure 21) i s the interaction between population o r i g i n and water deprivation (Tables XXVI, XXVII).  High area water-deprived animals had a much lower percent  water i n feces than the high area controls while the low area water-deprived animals had a s l i g h t l y higher percent water i n feces than did the low area controls.  The high area water-deprived animals were apparently reacting  t o dehydration by concentrating t h e i r feces while low area animals were not. Data summarized by Chew (1965) indicates that regardless of the percent water i n the feces o f hydrated animals (from 61.2$ t o 46.8$) dehydrated Jaculus, Dipodomys. Peromyscus and Rattus a l l showed f e c a l water percentages o f 41 t o 45$.  The r e s u l t s f o r the c o n t r o l groups and the water-  deprived low area animals f a l l i n t o the range given by Chew f o r hydrated animals, while the result f o r the high area water-deprived animals f a l l s  F i g u r e 21»  A  0  Mean p e r c e n t  water loss deprived  water  i n f e c e s , and(B)»  daily  i n h i g h and low a r e a a n i m a l s g i v e n  of water  0  fecal and  -107-  near  the  another  lower part  of  indication of  the the  range  for  greater  dehydrated  animals.  effective dehydration  This of  may  the  be  high  area  animals. Fecal water differences  (Tables  XXVI.  both water-deprived than were the  loss per  Evaporative  XXVII).  groups  control  were  groups  Water  is  XXVII) The  shown  response  of  from c l e a r  of  present  this  high  in  very  angle  in  control  or water  great  Dipodomys  and  was  factor  of  significant  c l e a r and  to water  experiment, in  however,  feces per  day  it  s k i n and pulmonary  water  difference  (Tables  XXVI,  other  groups.  animals  and t h e  fits with the  deprivation.  (Quay,  more  general  The mechanism i s  at  the  is. t o  (Chew  evaporative the  up  1961).  evaporated  is  significant  sweat  fur  at  glands  such as t h e do not  significant  far  soles  appear  role  in  are  to  the  be  temperature  cooling utilized  high  of  by  temperatures.  This  evaporation  water  temperatures. concluded that  indicate that  s k i n makes  any  a  They  s k i n was n e g l i g i b l e  a n d Dammonn,  i s where  (1950)  data which  the water  lick  experimental  through the  general,  1965).  of  The method  in  l o c a l i z e d areas  loss.  loss  then,  l i p  in  play  presents  of  and  enough numbers t o  water  This,  only  and heteromyids  the  loss through the  most  is  Schmidt-Nielsens  diffused (1965)  of  water  that  the  significant  s l i g h t l y less water  a combination  The  animals  Perognathus  The  Chew  of  area water-deprived  low numbers  present  a  loss,  response  Perognathus.  and t h e  not  losing  end  showed no  0  22.  high  area  By the  21)  however. In  which  Figure  i s between the  function  feet  in  (Figure  Loss  Evaporative water loss,  day  about  16$  There lost  is  i n Dipodomys this of  may n o t the  general  from the  total  and be  of  Perognathus.  true  and  that  evaporative  agreement,  respiratory  c o n s e r v a t i o n o f w a t e r must  however,  surfaces. occur.  © 65-|  .66-1 mg Water Loss Per ml Used  Metabolic  mg Water  H  Rate  L o s s Per _  Oxygen M  65-1  ml 0  Hour  A  Per g  Per Hour 55 H  .62H  2  5.5  A  .60-  .58-1  45-1  Early  Water Low •  Early  High A Figure  22.  A. W a t e r hour,  lost  p e r m l o f o x y g e n u s e d , (B)t w a t e r  and(C)> m e t a b o l i c  animals deprived  r a t e I n h i g h and low  o f and g i v e n water.  lost  area  per  None O A  4.5-J  -109-  Respiratory water l o s s varies d i r e c t l y with metabolic rate i n many animals (summarized by Chew, 1965)0  In t h i s case the metabolic rate o f the  water-deprived animals was l i t t l e lower than that of the controls.  The  other p o s s i b i l i t i e s are that the temperature o f the expired a i r was lower i n t h i s group o f animals and/or that the volume of inspired a i r was l e s s . These two p o s s i b i l i t i e s are related i n that Chew (1965) summarizes data which show that i n a pattern of rapid shallow breathing the temperature o f the expired a i r i s higher and the respiratory volume, and therefore the percent of inspired a i r i n a l v e o l i , i s l e s s .  E i t h e r or both o f these effects could  account f o r the observed difference. Food Intake Most mammals other than Mus and the heteromyids v o l u n t a r i l y reduce food intake when deprived o f water (summarized by Chew, 1965).  The value  of t h i s response i s a reduction of urine volume and consequently a more favorable water balance.  In agreement with the findings c i t e d above, P.  parvus from the high and low areas d i d not decrease food intake i n comparison with control groups (Tables XXVI, XXVII, Figure 23 )»  The reason  f o r the f a i l u r e t o stop eating when deprived o f water may be due t o the a b i l i t y t o r e t a i n p o s i t i v e water balance on an a i r - d r y d i e t .  At humidities  above 2 0 % kangaroo rats can maintain p o s i t i v e water balance on a i r - d r i e d foods (Schmidt-Nielsen, 1964) as can P. parvus above 76$ humidity.  No  difference was found between the water intakes i n the form o f l e t t u c e i n the high and low area control groups (Tables XXVI, XXVII, Figure 2 3 ) . CONCLUSIONS 1.  At 76$ humidity water-deprived animals, when fed p e a r l barley  equilibrated t o that humidity,were  able t o maintain t h e i r weight; but water-  deprived animals at !£% humidity l o s t weight.  F i g u r e 23.  A,  Free w a t e r i n t a k e i n food p e r day  area water  animals  deprived  o f and  intake i n lettuce per  control  animals.  i n high  given water. day  i n high  and  and  B.  low  Free  low  area  -111-  2, period to  Low  area  o f r a p i d weight  animals  area  l e s s weight  l o s s when d e p r i v e d  b e due t o t h e f o r m a t i o n  shortly  lost  o f water.  d i d not produce a comparably  showed a  shorter  T h i s d i f f e r e n c e appears  o f n e a r maximum o b s e r v e d  a f t e r w a t e r d e p r i v a t i o n b y t h e low a r e a  animals  because they  concentrations  animals,  concentrated  of urine  while the high  urine u n t i l  several  days a f t e r water d e p r i v a t i o n , 3, area  animals  A f t e r the i n i t i a l period o f rapid water loss gained weight  change d i f f e r e n t animals  lost 4,  concentrated 5, pressure, than  w e r e more  Both groups  humidity  animals both  the high  d i d n o t show a r a t e o f  groups o f  water-deprived  rate.  o f water-deprived  animals  produced a h i g h l y  urine, High area water-deprived percent water  animals.  This  found  higher.  animals  showed a h i g h e r p l a s m a  i n f e c e s and a l o w e r  evaporative water  i s i n t e r p r e t e d t o mean t h a t h i g h  area  osmotic loss  animals  dehydration,  Osmotic pressures  s i m i l a r t o those have been  A t 42$  a t t h e same  sensitive to 6,  may  from z e r o .  weight  lower  low a r e a  b u t t h e low a r e a  a t J6%  o f u r i n e and p e r c e n t  i n other desert  rodents, while  water  i n f e c e s were  evaporative water  loss  -112-  DISGUSSIDN  Mammals t h a t basic  categories,  which  evade  i t .  evader o f desert  o f low  distribution cannot  avoids  i n harsh  those which The  pocket  environments can  cope d i r e c t l y w i t h t h e  I t has  evolved  extreme t e m p e r a t u r e s ,  rainfall,  in British the  be  and  high  a variable  be  presence of trees  food  the  short  two  supply,  two  northern  those  adapted  coping  Its northern  l i m i t e d o n l y by  and  Into  is a highly  mechanisms f o r  evaporation.  C o l u m b i a may  divided  environment, and  mouse, P e r o g n a t h u s p a r v u s ,  conditions.  successfully with results  live  and  and  the  altitudinal  conditions  it  summer.  Adaptation  Deserts on  are  characterized  by  organismss  low  and  temperatures.  The  climatic conditions  mediate between a  semi-arid,  were the The  a l t i t u d e the  cold  along  s u c h , was  o f m o i s t u r e , and  i n the  steppe and  o f animals  e f f e c t o f a l t i t u d e , as  interest  i n t e r r e l a t e d stresses they  independable supplies  environment p o p u l a t i o n s The  two  not  arid,  hot  amount  area of  i s the  rainfall  minimum t e m p e r a t u r e s d e c r e a s e ,  most and  and  desert.  In  o f a l t i t u d e were  examined.  The  desert-like.  a v a i l a b l e water  the  inter-  a gradient  c l i m a t o l o g i c a l parameters co-variant  lowest  extreme  Okanagan V a l l e y a r e an  length  of the  impose  this studied.  e f f e c t s t h a t were with altitude.  W i t h an  increase  increases,  in  maximum  and  frost-free period  decreases,  ADAPTATION TO  LACK O F  WATER  Water i s b a s i c uses o f water that  to  life  i n a l l animals, but  remove i t f r o m t h e  body are  i n mammals t h e  cooling,  elimination  main of  of  -113-  wastes  and  maintenance o f t h e  advantageous loss with  for the  the  expenditure  Maximizing The water  green it  Water  the  food with  eliminate the  certain  f o r the pocket  high water content.  source  of water  green  available  f o r low  area  or because  Two  such  vegetation.  I t has  Although material  I t may  a lower  both  food  animal  animals.  i s disadvantageous  urea  has  animals  fat or carbohydrate,  be  used  content  because  of  more  live  in arid  areas.  maintain  diets The  a highly concentrated  1964)0  Pack r a t s  (Neotoma) s u r v i v e i n t h e  concentrated The amount  humidity  a high water content,  urine (Schmidt-Nielsen,  i n t h e b u r r o w may The  doubled  amount  food.  an  used  of free water  important  on  mouse  a diet  (Onychomys).  o f meat  urine (Schmidt-Nielsen d e s e r t by  and  are unable  allow  alone  and  f e e d i n g on  Haines,  Opuntia.  T h i s may  t o produce a h i g h l y  be  food  i n t h e burrow  expected,  since the  (Cloudsley-Thompson and  increases relative Chadwick,  i n a sample o f seeds b u r i e d at burrow  that  a  I964).  a p p r o a c h 100$  i n comparison w i t h  This would be  grasshopper  b e h a v i o r a l mechanism o f s t o r i n g  of water i n the  o f high water content  i t s weight  producing  c a c t u s w h i c h has  b e c a u s e m o r e w a t e r must b e  produced.  been demonstrated t h a t to  and  without  was  mouse t o m a x i m i z e I t s  o n l y h a l f a s much f r e e w a t e r a s  a r i d - l a n d c a r n i v o r e , can  1964)0  minimize water  i s u s e d t o p r o d u c e a gram o f w a t e r when m e t a b o l i z i n g p r o t e i n t h a n  It  the  i n t a k e and  It i s  energy as p o s s i b l e .  m a t e r i a l and  A high p r o t e i n content  when m e t a b o l i z i n g  an  select  i t i s more r e a d i l y  protein.  to  little  are availableg animal  appears t o be  oxygen  o f as  lungs.  Intake  vegetation contains  because  t o maximize w a t e r  main method a v a i l a b l e  intake i s to  materials  animal  absorptive surface of the  i n the  s a m p l e on t h e  gain of water during the time  surface of the the  animals  depth soil.  feed  on  -114-  stored food, but i t s importance during the summer i s unknown.  The animals  apparently carry quantities of seeds t o t h e i r burrows but i t i s not known i f they feed on the seeds immediately or eat them a f t e r storage. Minimizing Water Loss Evaporative, or insensible, water loss occurs through three main pathways?  the production of sweat, d i f f u s i o n through the skin, and evapo-  r a t i o n from the lungs.  The f i r s t of these i s r e l a t i v e l y unimportant since  Quay (1965) has shown that heteromyids have very few sweat glands and Schmidt-Nielsen (1964) found that kangaroo rats u t i l i z e evaporative cooling only as a l a s t resort.  Evaporative cooling, by saliva spreading, has only  been observed i n Perognathus accidentally exposed t o high temperatures i n traps. The rate of evaporation of water that has diffused through the skin has not been measured i n Perognathus.  In Dipodomys merriami,, however,  only about 16$ of the t o t a l water evaporated i s through the skin i n resting animals (Chew and Dammann, 1961).  It appears that the main pathway of  evaporative water loss i n heteromyids i s from the surface of the lungs. rate of loss depends on four factors%  The  humidity and temperature of expired  a i r , humidity and temperature of inspired a i r , amount of oxygen used, and the e f f i c i e n c y with which oxygen can be extracted from a i r i n the lungs. The humidity and temperature of inspired a i r are under the c o n t r o l of the animal only i f i t selects the best microhabitat.  Deep burrows and  nocturnal a c t i v i t y may provide environments which allow near maximal savings o f evaporative water. The white rat exhales a i r that i s at i t s body temperature, but the kangaroo rat exhales a i r that i s at a lower temperature than i t s body. lower  The  temperature r e s u l t s i n a lower absolute humidity i n expired a i r and a  -115-  saving of water by the kangaroo rat (Schmidt-Nielsen, 1 9 6 4 ) .  A counter-  current heat exchanger i n the nasalmucosa has been suggested as the mechanism which produces t h i s r e s u l t .  The temperature of expired a i r i n  Perognathus has not been measured but interpolated respiratory water loss at 28 G i n P. c a l i f o r n i c u s i s no lower than i n the white rat (Tucker, 1 9 6 5 a ) . The rate o f respiratory water loss i n P. parvus shown i n t h i s study i s s i m i l a r t o that found by Tucker f o r P. c a l i f o r n i c u s at 20 C ( 0 . 6 5 mg H2O loss/ml O2 used i n P. c a l i f o r n i c u s as compared t o O.67  i n P. parvus).  These data suggest  that a s p e c i a l mechanism t o decrease respiratory water loss i s not present i n P. parvus. Another method o f reducing evaporative water loss i s t o reduce the body temperature t o near environmental temperature.  P. parvus can enter  torpor at room temperature as do other species o f Perognathus and Cade, 1957)<>  (Bartholomew  Poor trap success i n the low area during a hot, dry period  i n August I 9 6 5 suggests that the animals may enter torpor i n response to extreme summer conditions.  It i s not known, however, i f Perognathus enters  torpor i n response t o water deprivation.  The incidence of torpor i n the  water deprivation experiments was too low t o allow s t a t i s t i c a l comparison but there appeared t o be no difference between water-deprived animals.  and c o n t r o l  The water-deprived animals d i d not v o l u n t a r i l y starve and enter  torpor as a r e s u l t , because food consumption d i d not decrease i n the waterdeprived groups.  MacMillan ( I 9 6 4 ) showed that cactus mice  (Peromyscus  eremicus). t o r p i d at 15 and 20 C, evaporated only 35*5% and 3 8 . 7 $ as much water, respectively, as those active at the same temperatures.  He suggests  that water loss would be much l e s s i n a humid burrow. Since water loss i s , at least t o a c e r t a i n extent, proportional t o oxygen uptake (Tucker, 1 9 6 5 a ) any reduction i n the amount of oxygen used would reduce the amount of water l o s t .  The amount of oxygen used i s under  -116-  the  c o n t r o l o f t h e animal t o t h e extent  activity  periods, entrance  oxygen-energy ratios,, rats  could extract  could  other  Schmidt-Nielsen  importance  20  C and  in  the field  of  Chew a n d Dammann's  0$  situation  o f 79$  I t becomes  second  ratio Little  percentages  these  water  in  suggests that of  fecal  kangaroo r a t s .  at  64$  Is lost  found  animals  animals.  only!  Animals  This ratio i s  A truer  relationship  When t h e s e  humidity,  o f time  or  figures  7:13:1,  P. p a r v u s  At  38% a n d 54$,  humidity  relative respectively,  are applied t othe  at  spends  79$  humidity.  i n i t s humid  burrow  realistic.  i n t h e p r o d u c t i o n o f f e c e s a n d i t was n o t g i v e n water and t h o s e d e p r i v e d o f water.  i n f e c e s were s i m i l a r t o t h o s e and a l s o  ( s u m m a r i z e d b y Chew,  I t was n o t o b s e r v e d t o o c c u r  found b y  1965).  The  Schmidt-  similar t o those  r e i n g e s t i o n may p l a n a n i m p o r t a n t  f e c a l m a t e r i a l was o b s e r v e d caught  i s shown i n  o f t h e r e l a t i o n s h i p between  i n dehydrated kangaroo rats  other dehydrated  27:13:1.  i nthe field.  species lost  may b e t h e m o s t  o f water  (1964)  encounter  a t 0$ h u m i d i t y .  14§13sl,  of  i n P. b a i l e y i a n d P. i n t e r m e d i u s .  found t o v a r y between animals  Nielsen  a i r than  o f e v a p o r a t i v e water l o s s under any  examination  Because o f t h e h i g h percentage the  inspired  kangaroo  be found b y m o d i f y i n g t h e r a t i o w i t h t h e r e s u l t s  (I96I)  a n d 64$  t h e i r water l o s s  ratio  o f oxygen from  h u m i d i t y have a r a t i o  might  evaporative water loss  humidities  high  found no evidence t h a t  o f evaporative t o u r i n a r y t o f e c a l water l o s s p e r day.  c i r c u m s t a n c e s t h e a n i m a l might  of  (1964)  o f foods w i t h  o f t h e routes o f water loss  gross overestimate o f t h e importance  and  and s e l e c t i o n  a greater percentage  relative  given water at a  Into torpor,  animals„  The the ratio  o f determination o f the length o f  found  Schmidt-Nielsen  role  i nwater  i n c a p t i v e pocket  balance  mice b u t  i n t h e stomachs and cheek pouches o f w i l d -  -117-  Th e p r o d u c t i o n o f h i g h l y  concentrated u r i n e appears  s h o r t - t e r m p h y s i o l o g i c a l adjustment deprived  o f w a t e r b o t h h i g h and low a r e a animals produce  twice as concentrated as they found between t h e groups t o m a i n t a i n low osmotic The in  and  animals  animals  at  f o r dehydrated  high protein  79$ h u m i d i t y .  ability prime  i s7*2.7si,  on d i e t  appear  t o produce  content.  t o be food  and t h e h a b i t  of relatively  and f e c a l water l o s s p e r day calculated  above f o r  f o r hydrated animals  for a total  s a v i n g o f about  methods  fail  selection,  animal t o maintain  microhabitat selection  Features o f food s e l e c t i o n  o f foods w i t h high water content  and making  evaporative cooling  balance cannot  Increases t h e i r  50$.  In  i n about  into torpor decreases t h e rate response  I t simportance be evaluated.  t o the levels  i nthe field  positive and an ares  as green free  water  In situations  t h e r e b y d e c r e a s i n g evapounnecessary.  When t h e s e  i n p o s i t i v e water balance a highly  w h i c h may r e s u l t  found t o b e an important laboratory.  seeds, which  and low temperature,  t o keep t h e animal  Entrance  7*13*1  and low  such  o f m i c r o h a b i t a t a l l o w s t h e animal t o remain  u r i n e c a n be produced  is  eaten.  o f storing  high humidity  rative water loss  unable  and would b e h i g h e r i f s a l t ^ l o a d e d v e g e t a t i o n o r  concentrated urine.  Selection  difference  o n c o n c e n t r a t i o n , t h e amount o f w a t e r l o s t i n  content, u t i l i z a t i o n  vegetation,  the  The o n l y  dependence on seeds w h i c h have a h i g h oxygen-energy r a t i o  protein  loss.  The r a t i o  main mechanisms w h i c h a l l o w t h i s  water balance  When  u r i n e more t h a n  h i g h a r e a animals were  evaporative, urinary  a n i m a l m a t e r i a l was  The  dehydrated  c a n b e compared t o t h e r a t i o  animals  i s dependent  hydrated.  i n P. p a r v u s .  c o n c e n t r a t i o n s i n t h e plasma.  a d d i t i o n t o b e i n g dependent urine  d o when f u l l y  was t h a t  r a t i o between  dehydrated  hydrated  t o water deprivation  t o be t h e major  a 50$  concentrated  reduction i n water  o f w a t e r l o s s b u t i t was n o t o f desiccation  observed i n  as a response t o negative water  -118-  Water and Reproduction The high need for water during l a c t a t i o n may explain why reproduction was delayed u n t i l the end o f the comparatively dry months o f A p r i l and May,,  Comparative water balance may also explain why high area females,  l i v i n g i n a moist er environment, came into reproductive condition before the low area females  c  The months o f June, July and August produce growth o f  grasses i n both areas, which provide a good supply of water t o l a c t a t l n g females.  ADAPTATION TO EXTREME AND VARIABLE TEMPERATURES The Okanagan Valley provides three temperature-related factors which are unfavorable t o the s u r v i v a l o f small mammals i high summer temperatures,  low winter temperatures  and the short summer season.  These  place d i f f e r e n t stresses on the animals and, i n most cases, require d i f f e r e n t types o f adaptations. High Summer Temperatures High summer temperatures water balance o f the animals.  pose t h e i r main threat i n d i r e c t l y t o the  Heteromyids have no s p e c i a l p h y s i o l o g i c a l  adaptations t o high temperature and can endure body temperatures than most other animals.  I f exposed t o high temperatures  u t i l i z e evaporative cooling, which i s a l a s t resort.  no higher  the animals must  Schmidt-Nielsen (196L)  summarizes information on s o i l temperatures, which shows that even In the hottest desert sampled the burrow temperature at a meter depth r a r e l y  reaches  30 C. The d i u r n a l change In temperature (Figure 2) means that by the time the animals emerge the temperature has f a l l e n at least below 35 C. P. parvus avoids high temperatures,  as do many other desert rodents, by the  simple expedients o f constructing a deep burrow and being nocturnal.  -119-  Lcw  W i n t e r Temperatures The  adaptations  o f t h e s e animals t o low temperatures a r e much t h e  same as t o h i g h temperatures.  The animals  a r e n o t a c t i v e above ground d u r i n g  c o l d weather and t h e depth o f t h e burrow p r o t e c t s t h e s o i l around t h e n e s t chamber  from f r e e z i n g .  Even i f t h e s o i l f r o z e , t h e n e s t would p r o v i d e a  c e r t a i n amount o f p r o t e c t i o n a g a i n s t c o l d .  The f a c t t h a t t h e animals can  arouse from a temperature as low as 2 C means t h a t i f t h e temperature i n t h e nest  f a l l s t o t h a t p o i n t t h e a n i m a l need not expend energy m a i n t a i n i n g  i t s body temperature above ambient.  The e f f e c t i v e n e s s o f t h e s e mechanisms  i s r e f l e c t e d i n t h e low w i n t e r m o r t a l i t y o f a d u l t a n i m a l s .  The s t r e s s low  w i n t e r temperature p l a c e s on t h e p o p u l a t i o n i s t h a t young animals  must  excavate burrows t o a c e r t a i n minimum depth b e f o r e t h e a r r i v a l o f w i n t e r . I f t h e minimum depth i s not reached w i l l not b e g r e a t  the insulating qualities of the s o i l  enough and energy w i l l have t o be expended t o m a i n t a i n a  temperature above 0 C.  T h i s s t r e s s would be expected  t o be g r e a t e r i n t h e  h i g h a r e a , where t h e f r o s t l i n e i s deeper and may be r e f l e c t e d e a r l i e r end o f r e p r o d u c t i o n i n t h e h i g h  i n the  area.  Short Summer Season The winter,  s t r e s s o f t h e s h o r t summer season, o r c o n v e r s e l y t h e l o n g  expresses  I t s e l f p r i m a r i l y i n terms o f energy.  The animals  must  s t o r e enough energy i n t h e form o f body weight o r s t o r e d food t o s u r v i v e the winter.  To o p e r a t e  i n t h e use o f t h i s  e f f i c i e n t l y t h e y must make every s a v i n g p o s s i b l e  s t o r e d energy.  W i n t e r i n t h e h i g h a r e a I s l o n g e r , as  shown by t h e mean annual t e m p e r a t u r e , t h e t i m e o f f i r s t  s n o w f a l l , and t h e  t i m e a t w h i c h t h e p o p u l a t i o n s cease b e i n g a c t i v e above ground.  A greater  s t r e s s would t h e r e f o r e b e p l a c e d on i n d i v i d u a l s o f t h e h i g h p o p u l a t i o n . Adaptations duct i o n .  t o meet t h a t s t r e s s a r e seen p r i m a r i l y i n t o r p o r and r e p r o -  -120-  Perognathus avoids tures  o f winter  much a s 60$ the  by entering torpor.  animals t o s t o r e  difficult  the  of torpor  northern  some s e l e c t i v e p r e s s u r e  part  o f t h e south,  (Eisenberg, periods  and s u f f i c i e n t  I963)  These a r e both longer winter  found  i n this  average length  energy saving  e n d e d much  the  t i m e o f onset  earlier  than  short periods, i t i s so short. may m a i n t a i n  It i s short  one t h a t w o u l d o p e r a t e i n  T h e most  likely  i n a new  species  The high  o f t o r p o r when  possibility  i n the hot desert environment f o r  show s h o r t e r area  animals  torpor show a n  exposed t o low t e m p e r a t u r e s .  greater percentage  o f time  spent  i n torpor.  d e v i c e s w h i c h h a v e b e e n d e v e l o p e d t o meet t h e  season  area  started  i t d i d i n t h e low a r e a .  o f the reproductive  length  i n t h e high  and end o f t h e r e p r o d u c t i v e  o f a b e t t e r supply  greater  saves  Perognathus o r i g i n a t e d i n t h e south  study.  season  season  slightly  The cues that  s e a s o n s a r e unknown.  i n the high  area  supplies o f water.  i n t h e high  area  o f t h e winter.  earlier, determine The  may h a v e b e e n a  o f green vegetation, but t h e e a r l i e r  appear t o be c o r r e l a t e d w i t h  and  I f torpor  Reproduction  reproductive  and  reproductive  i tpossible f o r  period.  The  result  o f spending as  t o meet t h e s t r e s s e s  a n d many o f t h e s o u t h e r n  Temperature and  start  to identify  time has not passed  T h e y a l s o show a c o n s i s t e n t l y  earlier  evolved  t o b e c o m e much l o n g e r .  longer  i n t h e environment  o f t h e r a n g e o f P. p a r v u s .  than these  initially  adaptation  s a v e more e n e r g y t h a n  o f torpor but i t i s d i f f i c u l t  periods  and low tempera-  enough e n e r g y t o s u r v i v e t h e w i n t e r .  a p p e a r s t o b e t h a t t o r p o r was  the  The b a s i c  o f food  t o u n d e r s t a n d why t h e a v e r a g e t o r p o r p e r i o d  possible that periods  shortage  o f t h e t i m e a t e n v i r o n m e n t a l t e m p e r a t u r e makes  energy, and l o n g p e r i o d s is  predators,  The e a r l i e r  end d i d n o t  end o f t h e  may h a v e b e e n d u e t o t h e e a r l i e r  To survive t h e winter  the last  onset,  litter  of  -121-  the of  s e a s o n must b e food.  Not  born  enough t o d i g a b u r r o w and  o n l y does t h e w i n t e r  longer,  requiring  ability  of the high  start  more s t o r e d f o o d  combined w i t h t h e summer p e r  early  area  earlier  female can be  animals end  and  to  earlier  i n the high  a deeper burrow.  reproduce  t o the  accumulate a  season,  The  much e a r l i e r means t h a t  store  area but  i t is  apparent  in-  i n the  spring,  fewer l i t t e r s  per  produced.  Distribution  P. desert. pine  parvus  stands,  even though t h e  dry v a l l e y s  areas. and  the h a b i t a t appears parvus  are  Ashcroft,  found. and  the  April-May  dry  This  suitable, such  very high areas  s e a s o n and  d u c t i o n t o t a k e p l a c e and numbers t o m a i n t a i n increase this  colder, stored what  food.  higher  l i m i t e d t o dry grassland  southern  and  There are  are the  altitude  limits  in  irrigated  the  the  o f c o l d weather  have access, but  slopes.  no  P.  of  be  enough t i m e  between t h e  i n the  fall  Three  environmental  end  f a c t o r s work  and  the winter  together is  i s longer, requiring  h y p o t h e s i s would be  t o determine  parvus ascends  the  enough  summer i s s h o r t e r , t h e w e a t h e r  c o n d i t i o n s , P.  of  for repro-  The  of this  to  a r e a s , however, where  t h e y o u n g t o become e s t a b l i s h e d i n l a r g e  environmental  animals  s o u t h - f a c i n g s l o p e above Cawston.  not  effect.  Ponderosa  Fraser River Valley north  t h e r e may onset  or  edge o f  same, o r  habitat selection  stocking populations  deeper burrows,  mountain  inside the  a p p e a r much t h e  hillsides.  areas  A possible test  altitude,  strict  the population.  general  requiring  grasses  unforested  Two  In these  to  strictly  Burrows o r t r a c k s have never been found  o r n a t u r a l l y wet the  appears t o be  some o f  more to the  -122-  Evolut ion  A discussion based in  on t h e assumptions  situ  that  and a r e g e n e t i c .  t h e Okanagan, a t l e a s t type animals,  these areas  I f the differences  observed  Highland type  on t h e h i g h l a n d s , b e c a u s e  t h e two t y p e s maintain t h e i r  animals.  o f animals  possibility  animals  appears  nature o f  The a l t e r n a t i v e would be glaciers  T h i s does n o t appear t o be p o s s i b l e  i f they  occurred  t o be that  differences  have developed  since  Many o f t h e d i f f e r e n c e s  a n d was because  and so could not  i n t h e same a r e a .  T h e most  t h e O k a n a g a n was c o l o n i z e d b y a  o f a n i m a l , p r o b a b l y more l i k e  t h e low a r e a  form,  and t h e  colonization. found  might  reactions within the limits  be g e n e t i c b u t might of reaction  both  populations.  The r e s u l t s  weak  evidence that  the populations are genetically  analysis  c o u l d not have  following the retreating  single type  w e l l be d i f f e r e n t  and one o f h i g h l a n d  are not r e p r o d u c t i v e l y i s o l a t e d  differences  developed  d i d not develop i n  of the dissected  a n d t h e many i n t e r v e n i n g v a l l e y s .  followed by lowland  differences  two i n v a s i o n s , one o f lowland  a h i g h l a n d t y p e moved n o r t h  likely  o f t h e t w o p o p u l a t i o n s must b e  some o f t h e o b s e r v e d  must h a v e o c c u r r e d .  moved n o r t h s o l e l y  that  of the evolution  of the physiological  equally  available t o  experiments  provide  different, while the  o f morphological variation provides stronger  evidence.  PHYSIOLOGY Several differences,  o f apparent  adaptive v a l u e , were  b e t w e e n t h e p o p u l a t i o n s when t o r p o r a n d w a t e r b a l a n c e w e r e subject but  of physiological  I have  ecophenotypes  environment.  examined.  The  I n mammals h a s b e e n p o o r l y e x p l o r e d ,  seen no evidence t o i n d i c a t e t h a t  vary non-reversably with  found  basic  physiological  It i s possible that  values  the early  -123-  experience to  o f animals  i n the field  m a i n t a i n low plasma  osmotic  may h a v e h a d a n e f f e c t  p r e s s u r e when d e h y d r a t e d ,  on t h e i r  ability  or the length o f  t h e i r t o r p o r p e r i o d s , t h a t was n o t e r a d i c a t e d b y t h e h o l d i n g e x p e r i e n c e i n the  laboratory.  differences  This possibility  may b e a c c e p t e d  appears  a s weak  t o be extremely  evidence  o f genetic  unlikely  and thes  differentiation.  MORPHOLOGY The lations  at  evidence  f o rg e n e t i c d i f f e r e n c e between t h e popu-  i s t h e morphological difference.  generation than  strongest  l a b o r a t o r y mice r a i s e d  other animals  selection  only  d i f f e r e n c e was n o l o n g e r s i g n i f i c a n t . temperature-caused to not  a field adapted  selected after  f o rreproductive success.  Little  observed  indicative  observed  This  After  experiment  18  first tails  generations  shows t h a t  but i s o f doubtful t h e experiment  but a f t e r  a  application  was s t a r t e d  18 g e n e r a t i o n s  In the field  have been t a k e n  i nthis  that  animals  were  had been  are not  observed  e n v i r o n m e n t b u t h a v e h a d many g e n e r a t i o n s t o  f o r several generations  differences  a t 21 C  change i n morphology, p a r t i c u l a r l y  when a n i m a l s  laboratory  i n a new  found  f o rreproductive success, t h e  The mice withwhich  f o r t h e low temperature,  one g e n e r a t i o n  adapt.  raised  ecophenotype can e x i s t  situation.  (1965)  a t -3 C h a d p r o p o r t i o n a t e l y s h o r t e r  o f t h e same s t r a i n  -3 C, h o w e v e r , w i t h  Barnett  study  o f genetic differences  o f hard  from t h e f i e l d  (Dice,  1949).  p a r t s , has been  and r a i s e d  The morphological  can t h e r e f o r e be accepted i n accordance  In t h e  with  as being  standard  taxonomic  practice. In  many i n s t a n c e s o f a d a p t i v e d i f f e r e n t i a t i o n  (Nevo a n d Amir, graphic  1964?  isolation  McNab a n d M o r r i s o n ,  (Fisler,  1965  1963; a n d  a n d B e n s o n , 1933)  flow between t h e p o p u l a t i o n s under examination.  either  Murie,  long distanc  196l)  have r e s t r i c t e d Although  o r geogene  sometimes t h e  -124-  d l f f e r e n c e s have become l a r g e the time In t h i s  factor study.  Important Most  (Fisler,  i s unknown a n d t h e d i f f e r e n c e s Blair  factor that  (1950)  o f Peromyscus t h a t In t h e  suggests that  has caused  o f h i s e v i d e n c e was  sharply than  In a short time  live  geographic  however,  i n r e g i o n s where  Okanagan  are In degree,  differentiation  collected,  1965)  a s was  found  Peromyscus.  environmental conditions vary  speciation could  occur  geographic  h i g h s e l e c t i v e p r e s s u r e s have p l a y e d  a greater role  i n d i f f e r e n t i a t i o n t h a n has r e s t r i c t e d  p h e n o m e n o n may  a p p l y o n l y t o t h e p o p u l a t i o n s e x a m i n e d o r i t may  mental gradients.  less  0  suggests that  more g e n e r a l a p p l i c a b i l i t y  i s t h e most  f r o m t h e b e t t e r known r a c e s  i n t h e populations under examination by anything l e s s than the evidence  cases  isolation  I n t h e genus  Although t h e r e i s no reason t o b e l i e v e t h a t  isolation,  i n most  i n areas o f harsh habitats  gene  flow. be  This of  and s t e e p e n v i r o n -  -125-  CONCLUSIONS  In n e a r l y the  high  and  apparently the  low  of adaptive  environments.  female, had  aspect  altitude  environment w i t h per  every  animals.  The  low  a longer  with  area  animals,  high  area  high  animals,  area  were present  i n the  tures.  It i s suggested  regions  is partially  genetic  lacking,  but  differences  that the  has  i n a warmer and  a low  drier summer  l i m i t e d by t h e of the  of morphological  vegetation,  plasma osmotic  less time  con-  i n t o r p o r at  i n a c o o l e r and  moister  i n l o w e r n u m b e r s , came i n t o  spent  more t i m e  distribution  low  reproductive  plasma  i n t o r p o r at  of the  length o f the  low  environment  animals  osmotic  low  into  a can  season a v a i l a b l e f o r  youngo characters  strong c i r c u m s t a n t i a l case be  built.  I t Is  restricted  gene  flow.  tempera-  colder  shows t h e Concrete  existence  evidence  of  of genetic  i n p h y s i o l o g i c a l c h a r a c t e r i s t i c s between t h e p o p u l a t i o n s  suggested  h a v e b e e n more r e s p o n s i b l e f o r t h e than  d i f f e r e n c e between  animals.  d i f f e r e n c e s between t h e p o p u l a t i o n s .  differences  d i f f e r e n c e s were  s p r i n g , were unable t o m a i n t a i n  establishment  Analysis  and  spent  living  c o n c e n t r a t i o n s when d e h y d r a t e d , and  and  living  t h e i r weight  o f w a t e r , and  d i d the  earlier  production  these  summer s e a s o n , p r o d u c e d m o r e y o u n g p e r  than  a longer winter,  condition  cases  between  a h i g h e r m o r t a l i t y r a t e i n y o u n g , a t e more g r e e n  c e n t r a t i o n when d e p r i v e d  The  I n most  s i g n i f i c a n c e when r e l a t e d t o t h e  were b e t t e r a b l e t o maintain  temperatures,  examined d i f f e r e n c e s were found  for the  existence of  that high  differentiation  selection  of the  is  such pressures  populations  -126-  LITERATURE CITED  Andrewartha, H . 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