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Population ecology of yellow-bellied marmots in British Columbia Donaldson, Judith Lee 1979

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POPULATION ECOLOGY OP YELLOW-BELLIED MARMOTS IN BRITISH .COLUMBIA by JUDITH LEE DONALDSON B.Sc., U n i v e r s i t y of V i c t o r i a , 1973 THESIS SUBMITTED IN PARTIAL FULFILLMENT THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Department of Zoology) We accept t h i s t h e s i s as conforming to the req u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA ' October, 1978 (c) J u d i t h Lee Donaldson, 1978 In p r e s e n t i n g 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 o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l m a k e i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r 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 g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f / > 0 d ( C j u The U n i v e r s i t y o f B r i t i s h C o l u m b i a 2075 Wesbrook Place Vancouver, Canada V6T 1W5 D a t e / i i ABSTRACT P o p u l a t i o n dynamics of y e l l o w - b e l l i e d marmots (Marmota f l a v i v e n t r i s ) were s t u d i e d a t Watch Lake, B r i t i s h Columbia. I attempted t o determine how p o p u l a t i o n s i z e was r e g u l a t e d and compared l i f e h i s t o r y t a c t i c s of the Watch Lake p o p u l a t i o n s w i t h t h o s e i n o t h e r a r e a s . N i n e t y - t h r e e p e r c e n t of a d u l t females and e i g h t p e r c e n t o f y e a r l i n g females had l i t t e r s . The mean l i t t e r s i z e was 6'. 1 ± . 3 8 . The s i z e and weight o f a female's l i t t e r were n e g a t i v e l y c o r -r e l a t e d w i t h her r e p r o d u c t i v e e f f o r t i n the p r e v i o u s y e a r . The a n n u a l m o r t a l i t y r a t e of j u v e n i l e s was 62%; m o r t a l i t y o f y e a r l i n g s and a d u l t s was 3 3 % . Most y e a r l i n g males and a few y e a r l i n g females e m i g r a t e d . . The p o p u l a t i o n s were expanding at a r a t e o f i n c r e a s e o f a p p r o x i m a t e l y . 2 7 . • The Watch Lake c o l o n i e s were g e n e r a l l y l a r g e r and denser than t h o s e r e p o r t e d from o t h e r a r e a s . A d u l t males were t e r r i t o r i a l t hroughout the a c t i v e season. A d u l t females defended t e r r i t o r i e s d u r i n g pregnancy and l a c t a t i o n . T h i s i s the f i r s t r e p o r t o f female t e r r i t o r i -a l i t y i n Marmota f l a v i v e n t r i s . E x p eriments i n d i c a t e d t h a t ' ( 1 ) a d u l t males caused y e a r l i n g males t o e.mmigrate and ( 2 ) a d u l t females i n h i b i t e d r e p r o d u c t i o n o f y e a r l i n g f e m a l e s . I p r e d i c t t h a t numbers w i l l s t a b i l i z e t h r o u g h the t e r r i t o r i a l b e h a v i o u r of b r e e d i n g females e i t h e r r e d u c i n g the b r e e d i n g success of females or i n c r e a s i n g the emigration r a t e of y e a r l i n g females. I describe an experiment to t e s t t h i s hypothesis. Marmot numbers near Watch Lake have been i n c r e a s i n g f o r s e v e r a l decades as new h a b i t a t becomes a v a i l a b l e . L i f e h i s t o r y t a c t i c s of these populations d i f f e r s from those i n -h a b i t i n g the s t a b l e environment of subalpine Colorado. Mar-mots at Watch Lake suffered greater m o r t a l i t y . They began breeding at a younger age than those i n other populations. They a l l o c a t e d r e l a t i v e l y more energy t o . r e p r o d u c t i o n , pro-duced l a r g e r l i t t e r s of smaller young, and grew to smaller adult s i z e . These d i f f e r e n c e s are c o n s i s t e n t with those p r e d i c t e d by the theory of r - and K- s e l e c t i o n f o r colon-i z i n g and s t a b l e populations. i v TABLE OF CONTENTS Page ABSTRACT.. i i LIST OF TABLES v i LIST OF FIGURES " "x ACKNOWLEDGEMENTS x i i INTRODUCTION ' 1 STUDY AREA 3 METHODS 10 RESULTS 12 PHENOLOGY 12 Vegetation and Snowmelt 12 Annual Cycle of A c t i v i t y 12 Reproduction 19 Moult 22 REPRODUCTION 24 Breeding Success 24 L i t t e r s 24 MORTALITY 55 M o r t a l i t y Rates 55 Sources of Loss 60 DISPERSAL 74 Emmigration 74 Immigration 82 POPULATION DENSITY AND RATE OF INCREASE 84 SOCIAL ORGANIZATION 91 A g o n i s t i c I n t e r a c t i o n s and'Scent Markings 91 Spacing 9 1 T e r r i t o r y A c q u i s i t i o n and E f f e c t s of Kin s h i p 119 V Page DISCUSSION 125 ANNUAL CYCLE OF ACTIVITY 125 Emergence from Hiberantion 125 Entrance i n t o Hibernation 127 REPRODUCTION 140 E f f e c t of Maternal Condition ori Reproductive Output 140 E f f e c t of L i t t e r Size on the Weights of J u v e n i l e s l 4 l Optimal L i t t e r Size of Marmots at Watch Lake l 4 l S i g n i f i c a n c e of Emergence Dates of L i t t e r s 1^ 5 Sex Ratio of L i t t e r s 146 COMPARISON OF SOCIAL ORGANIZATION WITH OTHER POPULATIONS 150 LIFE HISTORY TACTICS 155 Comparison of Demographic and Reproductive Parameters with Other Populations 155 L i f e . H i s t o r y S t r a t e g i e s of Marmots at Watch Lake, B r i t i s h Columbia and the East River V a l l e y , Colorado 167 POPULATION REGULATION 171 LITERATURE CITED 176 v i LIST OF TABLES l;TABLE . Page I I . D e s c r i p t i o n of c o l o n i e s 5 I I . Observed, and expected numbers of a d u l t s and y e a r l i n g s trapped i n A p r i l at the Home Colony i n 1974 and 1975 and at the Old Colony i n 1975 16".' I I I . Breeding success of females, 1974 and 1 9 7 5 . . 25 IV. Breeding success of y e a r l i n g s i n c o l o n i e s from which a l l or many adult females had been removed , and , i n . c o n t r o l . c o l o n i e s 26 V. Sizes of gravida and l i t t e r s at weaning 27 VI. Pre-weaning l o s s of young 29 V I I . C o r r e l a t i o n c o e f f i c i e n t s among reproductive v a r i a b l e s 31 V I I I . Stepwise. m u l t i p l e : r e g r e s s i 6 n s ; of .' reproductive v a r i a b l e s 34 IX... Comparison of reproductive v a r i a b l e s between females of d i f f e r e n t ages 35 X. J u v e n i l e sex r a t i o at weaning 44 XI. Comparison of reproductive v a r i a b l e s between years, excluding y e a r l i n g s 45 X I I . Seasonal and annual m o r t a l i t y of j u v e n i l e marmots 56 X I I I . The e f f e c t of the weight of j u v e n i l e s on t h e i r s u r v i v a l 58 XIV. Seasonal and annual m o r t a l i t y r a t e s of y e a r l i n g s and adu l t s 6 l XV. V a r i a t i o n i n seasonal and annual m o r t a l i t y r a t e s of y e a r l i n g s and adu l t s from J u l y 1 9 7 3 to May 1976 62 v i i TABLE Page XVI. Time and causes of deaths of j u v e n i l e marmots e x c l u d i n g t r a p p i n g 63 X V I I . Time and cause o f l o s s o f y e a r l i n g marmots.. 6 4 X V I I I . Time and cause o f dea t h o f a d u l t marmots.... 65 XIX. Frequency o f o b s e r v a t i o n s o f c o y o t e s at the Home Colony 67 XX. Response o f marmots t o r a p t o r s 69 XXI. P r o p o r t i o n of l o s s o f y e a r l i n g and a d u l t marmots t o d i f f e r e n t s o u r c e s 72 X X I I . D i s t a n c e moved by e m i g r a t i n g y e a r l i n g s 75 X X I I I . F a t e o f e m i g r a t i n g y e a r l i n g s 76 XXIV. E m i g r a t i o n o f y e a r l i n g males from the Home ( a d u l t male removal) Colony and Old ( a d u l t female removal) Colony 79 XXV. Number o f a d u l t s i n the e x p e r i m e n t a l c o l o n i e s , mid-May t o mid-June 1975 8 l XXVI. Numbers o f immigrants and t r a n s i e n t s 83 XXVII. C o m p o s i t i o n o f the Home Colony 1 9 7 3 t o 1 9 7 5 85 X X V I I I . Rate o f i n c r e a s e , r , o f the Home Colony based on numbers o f a d u l t and y e a r l i n g females 87 X X I X . . . S u r v i v o r s h i p t a b l e ( 1 ) and f e c u n d i t y t a b l e (in ) f o r Watch Cake marmot --cr -v.:. - . u d c : . 1 : p o p u l a t i o n s 89 XXX. Chases and f i g h t s / h o u r at t h e Home.Colony 1 9 7 3 t o 1976 92 XXXI. Chases and f i g h t s / a n i m a l - h o u r a t the Home Colony, 1 9 7 3 t o 1975 94 X X X I I . The average age-sex s t r u c t u r e o f t h e Home Colony June 1 9 7 3 t o J u l y 1 9 7 5 , e x c l u d i n g j u v e n i l e s 95 X X X I I I . The age-sex c l a s s e s i n v o l v e d i n a g o n i s t i c i n t e r a c t i o n s d u r i n g May, 1974 t o 1 9 7 6 , Home Colony 96 v i i i TABLE Page 1XXXIV. The age-sex c l a s s e s i n i t i a t i n g chases during . Xay and June.,.. .1973 t c , 1 9 7 6 , ?t at:";, the Home Colony 98 XXXV. The age-sex c l a s s e s i n i t i a t i n g chases d u r i n g June, 1 9 7 3 t o 1975 combined 99 XXXVI. The age-sex c l a s s e s i n i t i a t i n g chases d u r i n g J u l y 1 9 7 3 a t the Home Colony 100 XXXVII. The age and sex o f marmots chased d u r i n g May 1974 t o 1976 at the Home Colony 101 X X X V I I I . Rates o f sc e n t marking at the Home Colony i n 1975 from scan samples 104 XXXIX. Comparison o f f r e q u e n c y of sc e n t m a r k i n g by each age-sex c l a s s 105 XL. Frequency of s i g h t i n g s o f a d u l t males a t ':.'ru t h e i r home burrows 107 X L I . Frequency of s i g h t i n g s o f a d u l t females at t h e i r home burrows, Home Colony, A p r i l 18 t o August 1 , 1975 I l l XLI I . T e r r i t o r i a l f i d e l i t y o f a d u l t females between y e a r s 115 X L I I I . Y e a r l i n g s ' use o f burrows at the Home Colony, 1975 117 XLIV. Male y e a r l i n g s ' use of burrows at the Old Colony, 1975 118 XLV. The f i r s t time marmots used t h e i r t e r r i t o r i e s as t h e i r home burrows 120 XLVI. The time from which a marmot c o n t i n u o u s l y o c c u p i e d i t s t e r r i t o r y as i t s home burrow 121 X L V I I . Y e a r l i n g emergence from h i b e r n a t i o n , s e x u a l m a t u r i t y , and p r o p o r t i o n o f a d u l t weight i n f o s s o r i a l s c i u r i d s 128 X L V I I I . Comparison o f the l e n g t h o f a c t i v e season between Watch Lake, B. C. and E a s t R i v e r , C o l o r a d o 156 XLIX. Comparison o f p r o p o r t i o n o f females w i t h weaned l i t t e r s i n y e l l o w - b e l l i e d marmot p o p u l a t i o n s i n s i x a r e a s 158 i x .. T A B L E P a g e L . C o m p a r i s o n o f r e p r o d u c t i v e v a r i a b l e s o f W a t c h L a k e , B . C . p o p u l a t i o n s w i t h t h o s e i n t h e E a s t R i v e r V a l l e y , C o l o r a d o 159 L I . C o m p a r i s o n o f o v e r w i n t e r m o r t a l i t y o f j u v e n i l e s b e t w e e n W a t c h L a k e , B . C . a n d E a s t R i v e r V a l l e y , C o l o r a d o p o p u l a t i o n s 162 L I I . C o m p a r i s o n o f m a r m o t d e n s i t y a t W a t c h L a k e w i t h o t h e r a r e a s 166 X LIST OP FIGURES FIGURE Page 1. L o c a t i o n o f the study a r e a 7 2 . Map o f the Home Colony 9 3 . R e g r e s s i o n o f the time o f emergence from h i b e r n a t i o n on e l e v a t i o n 15 4 . Changes i n the age s t r u c t u r e o f marmots t r a p p e d between A p r i l 18 and May 8 a t the Home Colony 1974 and 1975 and Old Colony 18 5 . Frequency d i s t r i b u t i o n o f emergence d a t e s of l i t t e r s 21 6 . C o r r e l a t i o n s between the r e p r o d u c t i v e e f f o r t o f females i n 1974 and t h e i r l i t t e r s i z e , l i t t e r w e i g h t , and l i t t e r emergence date i n 1 9 7 5 . • 33 7 . R e g r e s s i o n o f weigh t s o f male j u v e n i l e s at emergence on l i t t e r s i z e 38 8 . R e g r e s s i o n of w e i g h t s o f female j u v e n i l e s at emergence on l i t t e r s i z e 40 9 . C o r r e l a t i o n between the t o t a l weight and s i z e o f l i t t e r s 42 1 0 . C o r r e l a t i o n between j u v e n i l e sex r a t i o and mean l i t t e r s i z e a t t h e Watch Lake C o l o n i e s 1 9 7 3 t o 1 9 7 5 and i n the East R i v e r V a l l e y C o l o n i e s 47 1 1 . C o r r e l a t i o n s between the r e p r o d u c t i v e e f f o r t o f females i n 1974 and t h e i r r e p r o d u c t i v e e f f o r t and A p r i l weight i n 1975 50 12. = Dependence o f the weight o f females i n A p r i l 1975 on t h e i r weight i n A p r i l 1974 and the weight o f t h e i r 1974 l i t t e r * . ' 53 1 3 a . G e n e r a l i z e d p a t t e r n o f growth i n marmots and ground s q u i r r e l s 133 x i ; FIGURE Page 13b. The h y p o t h e s i z e d dependence o f the p r o b a b i l i t y of s u r v i v i n g h i b e r n a t i o n on the weight upon e n t e r i n g h i b e r n a t i o n 133 14 . The h y p o t h e s i z e d dependence o f the p r o b a b i l i t y o f s u r v i v i n g h i b e r n a t i o n on the time at which h i b e r n a t i o n b e g i n s 135 15a. G e n e r a l i z e d s u r v i v o r s h i p curve o f marmots and ground s q u i r r e l s 137 15b. P r o b a b i l i t y o f s u r v i v i n g one y e a r as a f u n c t i o n o f the time h i b e r n a t i o n b e g i n s 137 16. The number of j u v e n i l e s s u r v i v i n g t o y e a r l i n g s as a f u n c t i o n o f l i t t e r s i z e 144 x i i ACKNOWLEDGEMENTS T h i s study would not have been p o s s i b l e without:.the h e l p o f many p e o p l e . I n 1973 Dr. A. T. Bergerud funded and s u p e r v i s e d the p r o j e c t . I n subsequent y e a r s Dr. I a n McTaggart Cowan p r o v i d e d f u n d i n g and s u p e r v i s i o n . Don and J a c k i e Eden k i n d l y a l l o w e d me to study c o l o n i e s on t h e i r r a n c h . R i c k D a v i e s , Susan L a t i m e r , and Bryan P o s t e r h e l p e d w i t h the f i e l d work. J u l i e t B u r n f o r d and E l i z a b e t h Orne ty p e d the t h e s i s and J e n n i f e r C l a r k p r e p a r e d the f i g u r e s . Mary T a i t t h e l p e d immeasurably. D i s c u s s i o n w i t h Douglas Heard and s t u d e n t s and f a c u l t y o f t h e I n s t i t u t e o f Ani m a l Resource E c o l o g y i n s p i r e d me throughout the s t u d y . Dr. C. J . K r e b s , Dr. J . M. T a y l o r , and Dr. C. J . W a l t e r s t o o k the time t o r e a d and c r i t i c i z e my t h e s i s . I r e c e i v e d f i n a n c i a l s upport from s c h o l a r s h i p s from the N a t i o n a l R e s e a r c h C o u n c i l of Canada and the U n i v e r s i t y o f B r i t i s h Columbia. I thank them a l l . I e s p e c i a l l y thank Dr. Cowan f o r h i s p a t i e n c e and Jack O l s e n f o r h i s encouragement. 1 INTRODUCTION A c e n t r a l q u e s t i o n i n p o p u l a t i o n e c o l o g y i s how pop-u l a t i o n s i z e I s r e g u l a t e d . I n p a r t i c u l a r , a r e any a n i m a l p o p u l a t i o n s r e g u l a t e d t h r o u g h b e h a v i o u r a l i n t e r a c t i o n s ? Y e l l o w - b e l l i e d marmots, Marmota f l a v i v e n t r i s , p r e s e n t fewer t e c h n i c a l problems t o a d d r e s s i n g t h i s q u e s t i o n t h a n many s p e c i e s . P o p u l a t i o n s l i v e i n i s l a n d s o f h a b i t a t and as such are e a s i l y d e f i n e d . B e h a v i o u r a l i n t e r a c t i o n s can be observed i n the f i e l d as marmots l i v e i n open h a b i t a t , a r e d i u r n a l , and a re l a r g e enough t o be seen from a d i s t a n c e . Indeed i n most p o p u l a t i o n s a l l i n d i v i d u a l s are v i s i b l e from a s i n g l e o b s e r v a t i o n s i t e . I n B r i t i s h Columbia t h e r e a re many l a r g e u n p r o t e c t e d p o p u l a t i o n s a l l o w i n g removal e x p e r i m e n t s and o t h e r m a n i p u l a t i o n s . I attem p t e d t o determine the s o c i a l o r g a n i z a t i o n o f the s e p o p u l a t i o n s , e s t i m a t e demographic p a r -ameters, and i s o l a t e t h o s e p r o c e s s e s t h a t might r e g u l a t e numbers. S i n c e MacArthur- and W i l s o n ( 1 9 6 7 ) i n t r o d u c e d the t h e o r y of r - and K- s e l e c t i o n , c o n s i d e r a b l e a t t e n t i o n has f o c u s s e d on t h e e v o l u t i o n o f l i f e h i s t o r i e s . They and o t h e r s p r e d i c t e d t h a t p a r t i c u l a r s e t s o f l i f e h i s t o r y t r a i t s s h o u l d be o p t i m a l under c e r t a i n e n v i r o n m e n t a l c o n d i t i o n s . I n s t a b l e p o p u l a t i o n s where c o m p e t i t i o n f o r r e s o u r c e s i s h i g h , i n d i v i d -u a l s s h o u l d produce o f f s p r i n g w i t h h i g h c o m p e t i t i v e a b i l i t y ; 2 i n u n s t a b l e and u n e x p l o i t e d e n v i r o n m e n t s , s e l e c t i o n s h o u l d f a v o u r h i g h p r o d u c t i o n ( P i a n k a 1 9 7 0 ) . The y e l l o w - b e l l i e d marmot p o p u l a t i o n s a t my study a r e a a t Watch Lake, B r i t i s h Columbia occupy a c o n s i d e r a b l y d i f f e r e n t environment from t h e i r s o u t h e r n a l p i n e and s u b - a l p i n e r e l a t i v e s . D u r i n g the l a s t 50 y e a r s y e l i o w - b e l l i e d marmots have e i t h e r expanded t h e i r range i n t o t h i s a r e a or g r e a t l y i n c r e a s e d t h e i r numbers t h e r e . They occupy e a r l y s u c c e s s i o n a l s t a g e s t h a t are c r e -a t e d by c l e a r i n g l a n d a t a r a t e f a s t e r t h a n they regrow t o f o r e s t . I can compare my o b s e r v a t i o n s w i t h t h o s e of the most i n t e n s e l y s t u d i e d Marmota f l a v i v e n t r i s p o p u l a t i o n s i n the s u b a l p i n e E a s t R i v e r V a l l e y of C o l o r a d o (Armitage 1 9 7 4 , Armitage and Downhower, 1 9 7 4 , Svendsen 1 9 7 4 ) . S e l e c t i o n i n t h i s h i g h s t a b l e environment s h o u l d d i f f e r from the low, d i s t u r b e d , and perhaps r e c e n t l y c o l o n i z e d Watch Lake a r e a . I compared the s o c i a l o r g a n i z a t i o n and s e v e r a l demographic parameters o f t h e s e p o p u l a t i o n s . Theory would p r e d i c t a g r e a t e r a l l o c a t i o n o f r e s o u r c e s toward r e p r o d u c t i o n i n the Watch Lake p o p u l a t i o n s , e x p r e s s e d as l a r g e r l i t t e r s , s m a l l e r young, e a r l i e r p u b e r t y , g r e a t e r r e p r o d u c t i v e e f f o r t and s m a l l e r a d u l t s i z e . 3 STUDY AREA The study a r e a near; the n o r t h e r n edge o f the range of Marmota f l a v l v e n t r i s , i s a t Watch Lake, 24 km s o u t h - e a s t of 100 M i l e House, B r i t i s h Columbia. T h i s i s on the F r a s e r P l a t e a u a t an e l e v a t i o n o f 1100 m. The a r e a i s r o l l i n g and e x t e n s i v e l y f o r e s t e d . I t l i e s near the edge o f the C a r i b o o Aspen-Lodgepole p i n e - D o u g l a s f i r b i o g e o c l i m a t i c zone ( K r a j i n a 1969). Lodgepole p i n e ( P i n u s c o n t o r t a ) i s the most abundant t r e e . Others are t r e m b l i n g aspen [ (Populus t r e m u l o i d e s ) , Douglas F i r (Pseudotsuga m e n z i e s i i ) , and White Spruce ( P i c e a g l a u c a ) . Openings i n the f o r e s t a re c r e a t e d by many l a k e s , ponds, marshes, n a t u r a l meadows and c l e a r e d f i e l d s . I n these c l e a r e d f i e l d s , I n r o c k - p i l e s by r o a d s l i d e s , and o c c a s i o n a l l y a t abandoned m i l l s i t e s , y e l l o w -b e l l i e d marmots are found. I n r e c e n t l y c l e a r e d f i e l d s o r abandoned homesteads, the s i t e s , o f the f i r s t burrows are under s t u m p - p i l e s o r b u i l d i n g s . I n the f o l l o w i n g y e a r s , burrows s l o w l y extend i n t o the f i e l d s . Because the c o l o n i e s d i s c r e t e u n i t s o f h a b i t a t , a pop-u l a t i o n can be e a s i l y d e f i n e d . There i s no e v i d e n c e o f move-ment of a d u l t marmots between c o l o n i e s . Nor i s t h e r e any s i g n o f marmots of any age c l a s s l e a v i n g and r e t u r n i n g t o the same c o l o n y . Most of the d a t a was c o l l e c t e d from t h r e e l a r g e 4 c o l o n i e s r e f e r r e d t o as Home, O l d , and F r a s e r (Table I , F i g . 1, 2 ) . I attempted to mark the e n t i r e p o p u l a t i o n a t the f i r two c o l o n i e s . At the F r a s e r C o l o n y , which was c o n s i d e r a b l y l a r g e r , o n l y p a r t of the p o p u l a t i o n was t r a p p e d . Two s m a l l c o l o n i e s , Community H a l l and Johnson's Pond, were a l s o s t u d -i e d . As w e l l , marmots were t r a p p e d , s h o t , i n t r o d u c e d , or observed at s e v e r a l o t h e r c o l o n i e s or burrow s i t e s . Table I. Description of colonies.. Name Approx. no. of adults Area of Area of opening F r a c t i o n oc-cupied by colony Years trapped Number burrows Home1 10 3.8 6.4 .60 73,74,75 27 Old 2 10 5.3 16.0 • 33 7^,75 31 F r a s e r J 20? 8.2 66.0 .12 73^74,75 -Community H a l l 4 0. or 1 - .15 - 74,75 1 Johnson Pond 5 's 1 or 2 i 1? 74,75 _ Unoccupied buildings and part of cleared f i e l d . Unused barn and part of cleared, f i e l d . Unoccupied buildings and part of cleared, f i e l d , c Infrequently used b u i l d i n g i n clearing,.,,-, g Old car chassis and rockpiles at abandoned m i l l s i t e . No l i v e - t r a p p i n g . 80 marmots shot. F i g u r e 1. L o c a t i o n o f the study a r e a near 100 M i l e House, B r i t i s h Columbia. Figure 2. Map of the Home Colony. The area i s grassland unless otherwise i n d i c a t e d . m a r s h 1 0 0 f e e t • B u r r o w x O b s e r v a t i o n T o w e r D H o u s e , B a r n , or S h e d s D r i v e w a y ^ E d g e of W o o d s = L o g 10 METHODS Marmot populations were, studied from June 1 9 7 3 to May 1 9 7 6 : June 12 - August 1 1 , 1 9 7 3 ; A p r i l 20 to August 3 1 , 1 9 7 4 ; A p r i l 15 to September 5 , 1 9 7 5 ; May 2 to 7 , 1 9 7 6 . Most marmots were captured with Tomahawk l i v e traps ','.(Box.. 3 2 3 , Tomahawk, Wise. 5 4 4 8 7 ) of one of three s i z e s , 30 x 25 x l8,:em, 23 x 23 x 66 cm and 16 x 16 x 4 8 cm. Traps set f o r a d u l t s and y e a r l i n g s were b a i t e d with l e t t u c e , dandelions, or c l o v e r . Those set f o r j u v e n i l e s were not b a i t e d . Marmots that would not enter the Tomahawk l i v e traps were captured w i t h l e g -hold traps or snares. In 1 9 7 3 I anaesthetized marmots with Nembutal f o r handling. In 1974 and 1975 I i n s t e a d used a can-was cone-shaped bag s i m i l a r to that used by FItzwater ( 1 9 4 3 ) . In a l l years marmots were tagged with s e l f - p i e r c i n g ; metal ear tags, weighed with Pesola scales (Basle, S w i t z e r l a n d ) , and sexed by perineum length. Females were examined f o r enlargement of mammae i n d i c a t i n g pregnancy or l a c t a t i o n . In 1 9 7 3 and 1974 I toe c l i p p e d a l l i n d i v i d u a l s as a permanent marker. Coloured p l a s t i c was i n s e r t e d on the ear tags to allow i d e n t i f i c a t i o n at a d i s t a n c e . This r e s u l t e d i n high tag l o s s . Consequently i n 1 9 7 5 I i n s t e a d a p p l i e d a l e t -t e r or number to the marmot's rump with Nyanzol f o r dye or Lady C l a i r o l Nice 'n,..Easy h a i r dye. I d i v i d e d marmots i n t o three age c l a s s e s : j u v e n i l e 11 ( f i r s t a c t i v e season), y e a r l i n g (second a c t i v e season), and adult ( 2 3 months cor o l d e r ) . J u v e n i l e s are separable from older c l a s s e s by weight and pelage d i f f e r e n c e s . Y e a r l i n g s •, can be d i s t i n g u i s h e d from adu l t s by weight u n t i l l a t e May. Two year o l d females are separable from older c l a s s e s u n t i l May 1 , two year males u n t i l mid-May. I c o l l e c t e d marmots f o r information on age s t r u c t u r e , breeding success, and gravidum s i z e ( l i t t e r s i z e during preg-nancy). In 1 9 7 3 , 120 were shot; i n 1974 and 1 9 7 5 , 12 breeding females were k i l l e d . I removed the reproductive t r a c t s of females and counted the p l a c e n t a l scars to determine gravidum s i z e . Marmots found dead of unknown causes were sent to the Animal Pathology Lab, Health of Animals Branch, A g r i c u l t u r e Department ( 3 8 0 2 West 4 t h Avenue, "Vancouver, B.C., Canada) f o r autopsies. At the Old Colony observations were made from a h i l l -side above the colony. At the Home and Fraser Colonies :. " marmots- were observed from towers 5 . 3 m high. Burlap sacks enclosed the space above a pl a t f o r m at 4 . 3 in . At the small colonies and fre q u e n t l y at the Fraser Colony I made observa-t i o n s from a v e h i c l e . I used 8X b i n o c u l a r s and e i t h e r a 15 to 6 0 X Bausch and Lomb s p o t t i n g scope or a 20 to 45X Bushnell scope. The number, i d e n t i t y , and behaviour of marmots were recorded by s e q u e n t i a l l y observing each burrow (scan sampling, Altmann 1 9 7 4 ) . As w e l l , a l l chases and f i g h t s were recorded. I determined the area of the co l o n i e s from a e r i a l photographs with a planimeter. 12 RESULTS PHENOLOGY V e g e t a t i o n and Snowmelt The snowpack t y p i c a l l y m e l t s i n A p r i l . I n 1974 o n l y p a t c h e s of snow remained on A p r i l 1 9 . I n 1975 snow c o m p l e t e l y covered the c o l o n i e s u n t i l l a t e A p r i l . I n 1976 p a t c h e s of ground were exposed i n e a r l y A p r i l . S n o w f a l l i s i n f r e q u e n t i n May. Temperatures r e a c h 0° C. a t n i g h t c o n s i s t e n t l y u n t i l June and o c c a s i o n a l l y throughout the summer. The f l o w e r s o f d a n d e l i o n s (Taraxacum o f f i c i n a l e ) a r e s e l e c t i v e l y e a t e n by marmots. They f i r s t bloom i n mid-May, are abundant May 22 t o June 3 , and go t o seed i n mid-June. C l o v e r ( T r i f o l i u m r e p e n s ) i s a l s o common i n t h e c o l o n i e s and blooms i n J u l y . The v e g e t a t i o n may dry up i n l a t e J u l y and August. Annual C y c l e of A c t i v i t y Marmots a t Watch Lake emerge from h i b e r n a t i o n i n A p r i l . I n 1974 the f i r s t marmot i n the a r e a was seen on A p r i l 8 ( J . Sheepbauer, p e r s o n a l communication). At the Home Colony marmots had been out f o r s e v e r a l days b e f o r e my a r r i v a l A p r i l 19 (P. L y t t o n , p e r s o n a l communication). I n 1 9 7 5 , a few marmots had emerged a t the Home Colony by A p r i l 1 5 . None emerged a t the Old Colony u n t i l A p r i l 18 t o 2 0 . I n 1 9 7 6 , the 13 f i r s t marmot emerged at the Home Colony A p r i l 1 ( E. B u r t , p e r s o n a l communication). A second had not appeared by A p r i l 6 . I n 1977 the f i r s t marmot emerged a t the Home Colony on A p r i l 6 (B. B u r t , p e r s o n a l communication). Woodchucks (Marmota monax), R i c h a r d s o n ' s ground s q u i r r e l s ( Spermophilus r i c h a r d s o n i i ) , and t h i r t e e n l i n e d ground s q u i r r e l s (Serpmophilus t r i d e c e m l i n e a t u s ) emerge from h i b e r n a t i o n l a t e r i n the n o r t h e r n p a r t o f t h e i r range t h a n the s o u t h e r n p a r t ( D a v i s 1 9 6 7 , Michener 1 9 7 3 , Rongstad 1 9 6 5 ) . T h i s t r e n d i s not apparent i n y e l l o w - b e l l i e d marmots / (r = - . 5 8 1 , n = 5 ) . I n s t e a d emergence date depends on e l e v a -t i o n ( F i g . 3 , r 2 = .9 1 6 ) . Y e a r l i n g s emerged l a t e r t h a n a d u l t s . D e s p i t e b e i n g more e a s i l y t r a p p e d t h a n a d u l t s , t hey were u n d e r r e p r e s e n t e d among marmots t r a p p e d i n A p r i l ( T a ble I I ) . Y e a r l i n g s grad-.• u a l l y i n c r e a s e d from 0% I n t h e A p r i l 18 t o 20 sample t o 48% i n the May 6 t o 8 sample ( F i g . 4 ) . Ten p e r c e n t of a d u l t s (n = 40) were c a p t u r e d on the f i r s t day of t r a p p i n g , A p r i l 1 8 . Ten p e r c e n t o f y e a r l i n g s (n = 5 0 ) were not c a p t u r e d u n t i l A p r i l 2 6 , i n d i c a t i n g at l e a s t an 8 day d i f f e r e n c e i n emer^ gence. The o b s e r v a t i o n s do not i n d i c a t e t h a t a d u l t males arid females emerge at d i f f e r e n t t i m e s . However t r a p p i n g may have begun t o o l a t e t o d e t e c t d i f f e r e n c e s . A l s o t h e g r e a t e r d i f -f i c u l t y i n t r a p p i n g males may have b i a s e d r e s u l t s . Marmots e n t e r h i b e r n a t i o n i n the same o r d e r : a d u l t males, t h e n a d u l t females and y e a r l i n g s , t h e n j u v e n i l e s . I n 1974 t h e l a s t a d u l t male at the Home Colony e n t e r e d hibernation between August 8 and 19• A d u l t females and most y e a r l i n g s F i g u r e 3- R e g r e s s i o n o f t i m e o f e m e r g e n c e f r o m h i b e r n a t i o n o n e l e v a t i o n . R e f e r e n c e s : W a s h i n g t o n (W. B e r n d s , p e r s o n a l c o m m u n i c a t i o n ) , C a l i f o r n i a (Nee 1 9 6 9 ) , W y o m i n g ( A r m i t a g e 1 9 6 5 ) , C o l o r a d o ( A r m i t a g e , p e r s o n a l c o m m u n i c a t i o n ) .' Ear l iest Emergence Date 51 Table I I . Observed and expected numbers of adults and yearlings trapped i n A p r i l at the Home Colony in 1 9 7 4 and 1 9 7 5 and at the Old Colony i n 1 9 7 5 -Trapped Expected 1 Adult males 5 5 . 3 9 Adult females 8 . 9 9 Yearlings 11 17 . 6 2 T o t a l 3 2 3 2 . 0 0 x 2 = 7 - 9 8 l 5 p < . 0 2 Expected values are based on sex and age structure of 9 0 known residents. F i g u r e 4 . C h a n g e s i n t h e a g e s t r u c t u r e o f m a r m o t s t r a p p e d b e t w e e n A p r i l 18 a n d May 8 a t t h e Home C o l o n y , 1974 a n d 1975 a n d O l d C o l o n y , 1 9 7 5 - E a c h p o i n t i s t h e p r o p o r t i o n a g i v e n a g e c l a s s r e p r e s e n t s o f t h e t o t a l s a m p l e t r a p p e d b y t h e g i v e n d a t e . 70 60 4-50 40 1 30 1 20 1 10 I S a m p l e S i z e 20 • 23 April 1 3 • 26 20 • 29 31 • A d u It M a l e s D Y e a r l i n g s A Adul t F e m a l e s A • A • D • 2 5 8 M a y June 41 51 56 89 ;9 disappeared by the end of August. A few j u v e n i l e s remain ac-t i v e i n e a r l y September. Reproduction Marmots at Watch Lake breed i n A p r i l . Mammae of preg-nant adult females become enlarged between A p r i l 28 and May 20. Breeding y e a r l i n g s d i d not show v i s i b l e signs of preg-nancy before May 12. The g e s t a t i o n period may be the same as that of woodchucks, 32 days (Hoyt 1952, G r i z z e l l 1955). Young are born i n May and emerge from t h e i r burrows i n June. Although I observed nursing o c c a s i o n a l l y up to 8 days a f t e r emergence, I use weaning synomomously with emergence. . \. r : l _ . During 1973 to 1976 the f i r s t date j u v e n i l e s appeared ranged from June 6 to 10. The mean emergence date of l i t t e r s (1973 to 1975) was June 14. The median date was June 11. Emergence dates of l i t t e r s of a d u l t s d i f f e r e d between 1974 (Y = June 9) and 1975 (T'= June 12) (t =-3-147, P < .01). The d i s t r i b u t i o n of emergence dates, grouped i n t o four day c l a s -ses, i s not normally d i s t r i b u t e d (p < " . 6 6 1 , Pig'.' 5). Regard-l e s s of the c l a s s s i z e used,-the modal c l a s s i s always the f i r s t c l a s s and a second small peak occurs about June 20. The d i s t r i b u t i o n can be viewed as e i t h e r truncated on the l e f t or, i f the l a t e r peak i s not considered an a r t i f a c t of sample s i z e , as bimodal. S e l e c t i o n against females emerg-ing e a r l y from h i b e r n a t i o n would cause t r u n c a t i o n of the l e f t t a i l . Also predation could s e l e c t b a g a i n s t e a r l y l i t t e r s . The s u r v i v a l of wildebeest (Connochaetes t a u r i n u s ) c a l v e s c i n -creases as the c a l v i n g season progresses and i n d i v i d u a l F i g u r e 5. Frequency d i s t r i b u t i o n of emergence dates of l i t t e r s . O b s e r v e d N u m b e r o f L i t t e r s 22 c a l v e s become l e s s c o n s p i c u o u s t o p r e d a t o r s ( E s t e s 1 9 7 6 ) . A l t e r n a t i v e l y , t h e r e may e x i s t an i n i t i a l l a r g e , h i g h l y synchronous peak at June 7 and 8 and a s m a l l peak 12 to 13 days l a t e r . A g a i n , the s t r o n g synchrony o f t h e f i r s t peak may be an a d a p t a t i o n t o p r e d a t i o n . The l a t e r peak may be l i t t e r s o f b r e e d i n g y e a r l i n g s and second o e s t r o u s a d u l t s . Y e a r l i n g s emerged from h i b e r n a t i o n l a t e r t h a n a d u l t s and be-gan showing v i s i b l e s i g n s o f pregnancy 14 days l a t e r t h a n a d u l t s . The mean emergence date o f l i t t e r s of y e a r l i n g s , June 24, was 13 days l a t e r t han t h a t o f a d u l t s , June 1 1 . A d u l t s f a i l i n g t o breed or c o n c e i v e d u r i n g a f i r s t o e s t r o u s , may have c o n c e i v e d d u r i n g a second o e s t r o u s . I n Columbian ground s . q u i r r e l s (Spermophilus c o l u m b i a n u s ) , a n o t h e r t y p i c a l -l y mono-oestrous s c i u r i d , h e a t s r e c u r at 14 t o 15 day i n t e r -v a l s i f a female i s not b r e d (Shaw 1 9 2 5 ) . I n c e r v i d s , the l e n g t h o f o e s t r o u s c y c l e v a r i e s between s p e c i e s , 8 days i n b l a c k t a i l deer ( O d o c o i l e u s hemionus) (Thomas 1 9 7 0 , 10 t o 12 days i n c a r i b o u ( R a n g i f e r t a r a n d u s ) (Bergerud 1 9 7 5 ) . Moult J u v e n i l e s moult on the rump, t h e n p r o g r e s s t o mid-back, head and, f i n a l l y , t o the back of t h e s h o u l d e r s and the f o r e l e g s . I n 1 9 7 5 , some completed the moult o f the rump by J u l y 5 ; o t h e r s had not moulted by August 5 . Weight i s a b e t -t e r i n d i c a t i o n of moult than d a t e . A l l j u v e n i l e males g r e a t e r than 1 . 2 3 kg had moulted on the rump, but none l e s s t h a n 1 . 1 6 kg had. Females began m o u l t i n g between . 9 4 and 1 . 0 3 kg. I n 1 9 7 5 , the f i r s t c o m p l e t e l y .moulted juvenile was trapped on July 26. 23 N o n l a c t a t i n g y e a r l i n g females moulted on the rump be-tween June 8 and J u l y 3 , y e a r l i n g males between June 17 and J u l y 7 , and a d u l t males between June 22 and J u l y 1 2 . A d u l t females and l a c t a t i n g y e a r l i n g females moult l a t e r . One had not begun m o u l t i n g on her rump on J u l y 2 1 . A d u l t s and l a c -t a t i n g y e a r l i n g s o c c a s i o n a l l y l o s e h a i r on the backs o f t h e i r s h o u l d e r s i n May. However l a c t a t i n g females do not grow new h a i r u n t i l J u l y . C o nsequently they may have bare p a t c h e s on t h e i r s h o u l d e r s throughout the s p r i n g . REPRODUCTION B r e e d i n g Success Pregnancy r a t e s are based on females examined between May 12 and June 6 . Ninety-one p e r c e n t o f a d u l t f e m a l e s , i n -c l u d i n g 71% o f two year o l d s , were pregnant (Table I I I ) . N i n e t y - t h r e e p e r c e n t o f a d u l t s , i n c l u d i n g 78% o f two y e a r o l d s , had l i t t e r s emerge. The p e r c e n t pregnant and. p e r c e n t weaning l i t t e r s were e s t i m a t e d from somewhat d i f f e r e n t samples; hence the a p p a r e n t l y h i g h e r p r o p o r t i o n w i t h l i t t e r s . There was no e v i d e n c e o f l o s s o f whole l i t t e r s between con-c e p t i o n and weaning. The two a d u l t females t h a t d i d not wean l i t t e r s showed no s i g n s o f pregnancy. B r e e d i n g s u c c e s s o f y e a r l i n g females was c o n s i d e r a b l y l o w e r . Only 19% were pr e g n a n t ; 8% weaned l i t t e r s ( Table I I I ) . I n c o n t r a s t t o a d u l t f e m a l e s , two o f f i v e pregnant y e a r l i n g s d i d not produce l i t t e r s . B r e e d i n g s u c c e s s o f y e a r l i n g females i s a p p a r e n t l y a f f e c t e d by the presence o f a d u l t f e m a l e s . I n 1 9 7 3 I removed 10 a d u l t and y e a r l i n g females from t h e F r a s e r Colony. I n 1974 I removed a l l a d u l t and y e a r l i n g females from the Old Colony. I n the y e a r i m m e d i a t e l y f o l l o w i n g the r e m o v a l , more y e a r l i n g s became pregnant and weaned l i t t e r s i n the removal c o l o n i e s t h a n i n the c o n t r o l c o l o n i e s ( T a b l e I V ) . L i t t e r s S i z e . ranged from 3 Gravidum s i z e ( l i t t e r s i z e d u r i n g pregnancy) t o 12 w i t h a mean of 7 - 1 (Table V ) . I t v a r i e d Table I I I . Breeding success of females, 1974 and 1975 Year Colony Pregnant - p Weaned l i t t e r s Yearling ;s Two year olds A l l adults Yearlings Two year olds A l l adults 1974 Home - 1/1 1/1 0/3 4/5 9/10 Old 1/6 - 7/7 0/5 - 4/4 Fraser l / l - 2/2 - - 3/3 Gratten's Community H a l l T o t a l 1/9 3/ 1 6 1/1 1/1 1/1 12/12 0/8 4/5 1/1 17/ 1 8 Percentage 18.75 100 100. 0 0.0 • 80.0 94.4 1975 Home 0/8 2/3 7/8 0/12 2/33 9/10 Old 3/9 2/3 2/3 2/11 1/1 1/1 Fraser 2/10 - - 1/7 - -T o t a l 5/27 4/6 9/11 3/30 3/4 10/11 Percentage 18.5 6 6 . 7 81.8 10. 0 75-0 9 0 . 9 Grand To t a l 8/43 5/7 21/23 3/38 7/9 2 7 / 2 9 Percentage 18 . 6 71.4 91.3 7-9 77.8 9 3 . 1 Number pregnant/sample si z e Number weaning litters/sample s i z e . The sample s i z e includes both pregnant females and those that were not. The one female that did not produce a l i t t e r had no p l a c e n t a l scars.: and l i k e l y . d i d not breed. Table IV. Breeding success of yearlings i n colonies from which many adult females had been removed and-i n control colonies. Sample siz e i n parentheses. Proportion Proportion pregnant weaning l i t t e r s .18(11) .04 ( 2 7 ) 2.00 <.10 Fraser 1 9 7 4 , Old 1 9 7 5 Home, Old 1 9 7 4 , Home, Fraser 1 9 7 5 'One-tailed test of independence Removal colonies .40(10) Control c o l o n i e s 2 . 1 2 5 ( 2 4 ) G 3 3 . 0 3 p < ' . 0 5 ) Table V. Sizes of gravida and l i t t e r s at weaning. Mean-standard error (sample s i z e ) 1973 1 9 7 4 1975 Tot a l Colony Gravida L i t t e r s - Gravida L i t t e i - 3 Gravida L i t t e r s Gravida L i t t e r s Home"'" 5-3(3) 7.0(1) 6.309) 5.3(3) 5.7(9) 5.75^.479(4) 5.90±.347(21) Old - 7.0(8) 8.0(2) 3.0(1) i 3 . 0 2 6.56^.556(9) 6.00^2.00(3) Fraser 8.1(7) - 7.5(2) - 5.0(1) 5.0(1) 7.70±.700(10)5.0(1) Other 8.3(3) 3 - 7.5(2) 4 8.5(2) 5 - 8.00±l.l4(5) 8.50±2.50(2) Gravida mean 8.20i.696(10) 7. 1 5 - .406(13) 4 . 8 0±.490(5) 7.1^.386(28)6. 07-. 379(27) L i t t e r mean 5.33-.333(3) 6 . 9 2 - . 5 6 0 ( 1 3 ) 5 . 2 7 ± . 5 3 6 ( 1 1 ) Overallg mean 7-54 ( 1 3 ) 7.04 ( 2 3 ) 5 . 2 7(11) 6.77(47) 2annual mean l i t t e r s i z e s are parameters. Only the f i r s t l i t t e r to emerge was completely counted. I t contained only 2 young. nThe 3 l a t e r l i t t e r s contained at least 10 young. jjGratten Colony ^Community H a l l and Jones Colonies. gCommunity H a l l and Johnson's Pond Colonies. I f both gravidum and l i t t e r s i z e knowi., only l i t t e r s i z e was included. -•ro 28 among years (p = . 0 0 5 ) , but not c o l o n i e s (p < . 2 5 ) . 1 The years 1 9 7 3 and. 1974 d i d not d i f f e r (Sheffe's a p o s t e r i o r i t e s t , p = . 3 6 6 ) . Gravidum s i z e i n 1 9 7 5 was smaller than i n both previous years ( 1 9 7 3 P = . 0 0 5 , 1975 P = . 0 5 0 ) . L i t t e r s i z e at. weaning ranged from 2 to 11 with a mean of 6 . 1 (Table V) and a mode of 5. I t may have v a r i e d among years (p = . 0 9 0 ) . There were s u f f i c i e n t data to compare the Home Colony l i t t e r s i z e s only with l i t t e r s from a l l other c o l o n i e s combined. The Home Colony d i d not d i f f e r from the other c o l o n i e s . When gravidum and l i t t e r s i z e s are compared using a t - t e s t , gra-.'. ^ v i d a are s i g n i f i c a n t l y l a r g e r ( o n e - t a i l e d , p < . 0 2 5 ) . How-ever, most of the gravidum s i z e s were determined i n the pro-ductive years, 1 9 7 3 and 1 9 7 4 , while many l i t t e r s i z e s were determined i n 1975 (see Table V). I f the variance among years i s taken i n t o account, scar counts do not exceed l i t t e r s i z e s ( o n e - t a i l e d t e s t , two-way a n a l y s i s of variance,.. p- << . 2 5 ) ) There was l i t t l e l o s s between i m p l a n t a t i o n and weaning Both gravidum and l i t t e r s i z e were known f o r seven females (Table V I ) . The only marmot l o s i n g more than one young was dying of c o c c i d i o s i s during l a c t a t i o n . The others l o s t a mean of . 5 y o u n g / l i t t e r . Large gravida were no more l i k e l y to lose young than smaller ones. However sample s i z e s are inadequate to detect d i f f e r e n c e s which might e x i s t . The s i z e of a female's l i t t e r appears to depend on Variance i n l i t t e r s i z e was t e s t e d with two one-way anovas as there was i n s u f f i c i e n t data f o r a two-way anova. Table.-VI. Pre-weaning l o s s of young. 29 Year Number of P l a c e n t a l s c a r s Number o f j u v e n i l e s weaned Loss 1975 6 5 1 5 5 0 5 4 1 3 2 1 1974 8 8 0 6 6 0 7 5 1 2 Mother d i e d <3f c o c c i d i o s i s June 9-her c o n d i t i o n at breeding. L i t t e r s i z e was not c o r r e l a t e d with the s i z e of her l i t t e r the previous year (r = - . l 8 l , n = 8 , see Table V I I I ) . I t was c o r r e l a t e d with the female;'is weight ori A p r i l 30 together with her weight gain from the previous A p r i l 30 (R = . 8 7 6 , n = 8 , p <'i'05). (Her weight alone was not c o r r e l a t e d with the s i z e of.her l i t t e r (Table V I I ) ) . The r a t i o of the weight of a l i t t e r at weaning to the mother's weight on A p r i l 3 0 , I r e f e r to as "reproductive e f f o r t " . L i t t e r s i z e was n e g a t i v e l y c o r r e l a t e d with both the weight of the female's l i t t e r i n the previous year and with her reproductive e f f o r t that year (Table V I I , P i g . 6 ) . The c o r r e l a t i o n of l i t t e r s i z e with the weight and the weight gain of the mother, with the weight of her previous year's l i t t e r , and with her reproductive e f f o r t that year i n d i c a t e that the s i z e of a l i t t e r i s l l i k e l y determined by the c o n d i t i o n of the female at breeding In A p r i l . Weight. The mean weight of j u v e n i l e s w i t h i n four days of emergence was .344 ± .099 kg (n = 104). Their weight de-2 pended p r i m a r i l y on the l i t t e r s i z e (r = . 5 7 ) and to a l e s -ser, -;.but s i g n i f i c a n t , extent of the sex of the j u v e n i l e and on the mother's weight. Within l i t t e r s , males weighed more than females (paired t - t e s t 1 6 . l i t t e r s , p < .01). For a given l i t t e r s i z e , heavier females produced heavier o f f s p r i n g (Table VIII). Females three years and older had heavier young than y e a r l i n g s and two year olds (Table IX) . This l i k e l y a func"•=•:". t i o n of d i f f e r e n c e s i n t h e i r mothers' weights (Table V I I I ) . As l i t t e r s i z e increased, i n d i v i d u a l weights decreased T a b l e V I I . C o r r e l a t i o n C o e f f i c i e n t among r e p r o d u c t i v e v a r i a b l e s . Sample s i z e i n p a r e n t h e s e s . p<.10:?, p<.05*, p<.01:**, p<.001***. L i t t e r L i t t e r J u v e n i l e Sex 2 Emerg, Females^ Repro.,- Weighty s i z e w e i g h t w e i g h t r a t i o d a t e Weight E f f o r t change L i t t e r w e i g h t . 6 2 7 ( 1 8 ) * * J u v e n i l e w e i g h t - . 7 5 5 ( 1 8 ) * * * - . 0 2 2 ( 1 9 ) Sex r a t i o - 5 2 4 ( 1 3 ) ? 7 . 6l6-( 1 3 ) * - . 0 0 9 ( 1 3 ) Emergence d a t e - . 5 5 3 ( 2 0 ) * - . 3 1 1 ( 1 8 ) .142(23)-.591(13) F e m a l e ' s w e i g h t . 3 4 7 ( 1 4 ) . 4 9 1 ( 1 3 ) ? . 1 5 6 ( 1 4 ) . 6 5 1 ( 1 0 ) * - . 7 7 7 ( 1 6 ) * * * R e p r o d u c t i v e e f f o r t .082(12) - . 0 7 3 ( 1 3 ) - . 1 1 2 ( 1 0 ) . 403(13) Weight change . 6 0 8 ( 6 ) .231(6) - . 9 2 0 ( 6 ) * * . 2 1 9 ( 6 ) - . 8 5 1 ( 6 ) * - . 3 1 0 ( 7 ) . 5 8 1 ( 6 ) L a s t y e a r ' s L-W.1 - . 9 2 7 ( 6 ) * * - . 8 9 0 ( 6 ) * .647(6) - . 6 3 3 ( 6 ) .472(6) - . 3 4 9 ( 5 ) - . 9 3 0 ( 5 ) * - . 9 6 2 ( 4 ) * L a s t y e a r ' s R.E.'° - . 9 5 2 ( 5 ) * - . 9 5 6 ( 5 ) * . 5 7 7 ( 5 ) - . 7 6 3 ( 5 ) . 933 ( 5 ) * - . 964 ( 4 ) * - . 955 (4 )* - . 9 3 5 ( 4 ) ? "'"Mean o f f s p r i n g w e i g h t a t emergence. I n c l u d e s o n l y t h o s e l i t t e r s o f w h i c h a t l e a s t h a l f 2 t h e young were w e i g h t e d w i t h i n 4 days o f weaning. P r o p o r t i o n o f male young. I n c l u d e s o n l y t h o s e l i t t e r s o f w h i c h a l l young were sexed. ^ T r a n s f o r m e d w i t h a n g u l a r t r a n s f o r m a t i o n . ^Emergence d a t e o f l i t t e r s . Log t r a n s f o r m e d . M o t h e r ' s w e i g h t on A p r i l 30. I f a f e m a l e was not c a p t u r e d b o t h s h o r t l y b e f o r e and a f t e r t h a t d a t e , h e r w e i g h t was e s t i m a t e d by assuming a w e i g h t g a i n o f .011 kg/day, c-the mean w e i g h t g a i n o f t h o s e c a p t u r e d t w i c e . g L i t t e r w e i g h t a t w e a n i n g / f e m a l e ' s w e i g h t A p r i l 30. -Female's w e i g h t A p r i l 30, 1 9 7 5 - Weight A p r i l 30, 1 9 7 4 . o E x c l u d e s a l i t t e r o f 2 w i t h a 1:1 sex r a t i o . O t h e r l i t t e r s had a t l e a s t 4 young. °1975 o n l y : r=.733(8)* The l i t t e r w e i g h t o f t h e same f e m a l e i n t h e p r e v i o u s y e a r . I n c l u d e s o n l y f e m a l e s ^ Q t h r e e y e a r s and o l d e r . The r e p r o d u c t i v e e f f o r t o f t h e same f e m a l e i n t h e p r e v i o u s y e a r . I n c l u d e s o n l y f e m a l e s 3 y e a r s and o l d e r . F i g u r e 6 . C o r r e l a t i o n s b e t w e e n t h e r e p r o d u c t i v e e f f o r t o f f e m a l e s i n 197^ a n d t h e i r l i t t e r s i z e , l i t t e r w e i g h t , a n d l i t t e r e m e r g e n c e d a t e i n 1 9 7 5 . 3 3 m N-CD 1Q T 8 6 44-co 4-_ 2 H—I 1—h r = " 9 5 2 p < . 0 5 X X -I—I—I 0 .2 .4 .6 .8 1 1.21.4 1.6 1.8 2 R e p r o d u c t i v e E f f o r t 1 9 7 4 254 IT) £ 204 5 1 15. r = - . 9 5 6 p < . 0 5 I I I 1 1 1 — l i l t 0 .2 .4 .6 .8 1 1.2 1.41.61.8 2 R e p r o d u c t i v e E f f o r t I974 ID N. CD I 2 Or-al o 164-S 134-c QJ cn | 104-UJ cu r= . 9 3 3 < . 0 5 - I — I — I — I — I — I — I — 1 — 4 -0 .2 .4 .6 .8 1 1.21.4 16 1.8 2 R e p r o d u c t i v e E f f o r t 19 74 • 3 4 Table VIII. Stepwise multiple regressions of reproductive v a r i a b l e s . 2 Dependent S i g n i f i c a n t Non-significant n p R var i a b l e independent variables variables L i t t e r size 2 3 Emergence date , Female's age Females weight, Year 1 3 Emergence elate, Female's age Year, Mean l i t t e r s i z e ^ 8 Female's age, Year, Emergence •' date, Last l i t t e r size-> 7 Juvenile weight L i t t e r weight L i t t e r s i z e , Emergence date, Year, Females Female 1s age weight L i t t e r s i z e , Female's weight Sex r a t i o L i t t e r s i z e , Sex r a t i o , Female's weight, Juvenile Female's age, Emergence date, weight, Year Year, L i t t e r Sex r a t i o , Emergence date, s i z e , Females Female's age weight-1 2 1 0 1 0 1 0 .004 . 7 0 6 . . 0 0 2 6 . 8 2 4 . 0 0 0 1 . 9 8 1 . 0 0 3 5 . 8 8 8 Sex r a t i o Emergence date Emergence date Female's weight' Female's weight Reproductive e f f o r t Female's weight Female's age, Year Female's weight, Female's age, L i t t e r s i z e , Reproduct-ive e f f o r t , Year Female's age, L i t t e r s i z e , Reproductive e f f o r t , Emergence date, Year Juvenile weight, Female's age, L i t t e r s i z e , L i t t e r weight, Reproductive e f f o r t , Year Female's age, Year 1 0 1 0 1 2 1 2 0 3 8 . 4 3 2 040 .424 , 0 2 7 . 3 9 8 1 7 « . 0 0 0 1 . 9 0 5 jOrdered from most to least significant-. 'For emergence date, female's weight, j u v e n i l e weight, sex r a t i o and ,reproductive e f f o r t see Table IX footnotes 3 , 4 , l , 2 , a n d 5 r e s p e c t i v e l y . JAge of the mother, y e a r l i n g ^ 2 year o l d , or 3 years and older. •Mean size of other l i t t e r s of the same female. Size of the same female's l i t t e r i n the preceeding year. Forward stepwise multiple regression. Backward stepwise multiple regression. 3 5 Table IX. Comparison of repr o d u c t i v e v a r i a b l e s between females of d i f f e r e n t ages. Meanistandard e r r o r ( n ) . Y e a r l i n g s and two year olds Three' years • and o l d e r Test s t a t i s t i c P L i t t e r s i z e 5 . 9 4 + - 3 8 3 ( 2 , 6 ) 1 6 : . 1 2 5 ± . 7 1 8 ( 8 ) t = . 5 9 6 45 2' L i t t e r weight (kg) 1 . 6 6 ± . 0 9 9 ( 1 , 3 ) 2 . 2 0 5 -.165 ( 8 ) t=2.l84 = . 2 0 2 7 J u v e n i l e weight (kg) .307-.014(8,20)3 •3655-.0 1 6(40) H P = 5 .02 049 • 5 Sex r a t i o •414(1 , 3 ) . 5 2 0 ( 7 ) t = . 8 3 2 <. 50 Emergence date 6 June 25(4)1 June 1 2 ( 5 ) June 1 0 ( 8 ) F = 6 . 9 6 = . 0062 Reproductive e f f o r t 1.4l±.122(l,4) 1 . 2 5 ^ . 1 0 7 ( 7 ) t=.'98l 40 Breeding female weight(kg) . 9 1 ^ . 0 2 6 ( 3 ) 1 1.49?.050 ( 6 ) ° 1 . 7 7 ^ . ^ 9 ( 8 ) F = 5 2 . 8 7 <. 00001 Weight change (kg) .64±.120(2)8 . l 4 ± . 1 0 9 ( 5 ) t = 2 . 6 6 05 p Y e a r l i n g sample s i z e , two year o l d sample s i z e . -One-tailed t e s t . jjMean of a l l j u v e n i l e s , not mean of l i t t e r means. A n a l y s i s of covariance: mean j u v e n i l e weight i n each l i t t e r as dependent v a r i a b l e , l i t t e r s i z e as c o v a r i a t e . Sample s i z e f o r r-yearlings and two year olds=5; f o r o l d e r females n = 8 . Back transformed means of data transformed by a r s i n where gP=proportion male. ^ Back transformed means of l o g trans formed data. Sheffe's a p o s t e r i o r i t e s t : l i t t e r s of y e a r l i n g s emerge l a t e r than 7 2 year o l d s , p=.046, and 3 year and o l d e r females, p=.007-, gYea r l i n g s . Two year o l d s . (Table V I I , F i g . 7 and 8 ) . L i t t e r s i z e accounted f o r more 2 of the v a r i a t i o n among male weights (r = . 6 6 ) than female p weights (r = .44). A male l o s t .049 kg f o r an increase of one i n l i t t e r s i z e . A female l o s t only . 0 2 5 kg. These r a t e s d i f f e r s i g n i f i c a n t l y ( a n a l y s i s of covariance, p = .049). The mean weight of l i t t e r s at emergence was 2 . 1 ± :. 12 kg. The weight was c o r r e l a t e d with l i t t e r s i z e (Table V I I , F i g . 9 ) . Because j u v e n i l e weight decreased w i t h l i t t e r , s i z e , l i t t e r weight v a r i e d much l e s s than l i t t e r s i z a (F = 1 8 . 2 9 0 , p << . 0 0 1 ) . L i k e the s i z e of the l i t t e r , l i t t e r weight was c o r r e l a t e d with s e v e r a l Indices of the mother's c o n d i t i o n . The greater the female's reproductive e f f o r t and the more her l i t t e r weighed one year, the l e s s her l i t t e r weighed the f o l -lowing year ( F i g . 6 ) . L i t t e r weight increased w i t h the weight of the mother (Tables VII and V I I I ) , and consequently with her age (Table I X ) . Together her weight and her weight gain from the previous year were c o r r e l a t e d w i t h the weight of the l i t t e r (R = . 8 8 6 , n = 8 , p < . 0 5 ) . The weight of the l i t t e r was a l s o c o r r e l a t e d with the l i t t e r ' s sex r a t i o , heavier l i t t e r s c o n t a i n i n g more males. The sex r a t i o was c o r r e l a t e d with.other, l i t t e r . w e i g h t c o r r e -l a t e s , l i t t e r s i z e and the female's weight (Table V I I ) . In a stepwise m u l t i p l e r e g r e s s i o n , the sex r a t i o does not s i g -n i f i c a n t l y reduce the variance i n l i t t e r weight unexplained by d i f f e r e n c e s i n l i t t e r s i z e , the year, and j u v e n i l e or the mother's weight (Table V I I I ) . F i g u r e 7 . R e g r e s s i o n o f w e i g h t s o f m a l e j u v e n i l e s a t e m e r g e n c e o n l i t t e r s i z e . Male Weani ng Weight ( kg) * * . • • • . • • » • • • . tO tO CO C O A ^ O l O l C D O ^ j 01 o Ol o Oi O- O1 O Oi O Ol. .  o 8 £ F i g u r e 8. R e g r e s s i o n o f w e i g h t s o f female j u v e n i l e s a t emergence on l i t t e r s i z e . F e m a l e W e a n i n g W e i g h t ( k g ) Figure 9 . C o r r e l a t i o n between the t o t a l weight and s i z e of l i t t e r s . 42 V a CM I D X CO X X > X X fN CO CN CN CN CM-CO CM CO -T -O + 0 ) CO •CO CD N - L . 1 0 CO <D + * -tr _ i •CO CM CM, q (6>|) 1L|6!8M J 9 U M 43 Sex R a t i o . The o v e r a l l j u v e n i l e sex r a t i o , 5 3 - 4 males: 4 6 . 6 females (n = 3 6 5 ) , d i d not d i f f e r s i g n i f i c a n t l y from 1 : 1 (Table X ) . Nor d i d i t d i f f e r from e q u a l i t y i n any s i n g l e c o l o n y , y e a r , or c o l o n y - y e a r . 1 I t d i d not v a r y among y e a r s (Table X I , r e p l i c a t e d t e s t o f goodness o f f i t , p < . 5 0 ) , among c o l o n i e s , (p > . 9 5 ) , or among c o l o n y - y e a r s (p > . 9 0 ) . The f r e q u e n c y o f males w i t h i n a l i t t e r i n c r e a s e d w i t h m a t e r n a l weight and decrea s e d the l a t e r a l i t t e r emerged (Table V I I ) . L i k e l i t t e r s i z e and w e i g h t , t h e l i t t e r ' s sex r a t i o can be p r e d i c t e d from the mother's weight and weight g a i n (R = . 8 0 8 , n = 8 , p < . 1 0 ) . The f r e q u e n c y o f males a l s o i n c r e a s e d w i t h l i t t e r s i z e . The i n d i v i d u a l l i t t e r s i z e s at weaning and sex r a t i o s from 1974 and 1975 are c o r r e l a t e d ( T a ble V I I ) . The p r o p o r t i o n o f males i n a l i t t e r ranged from . 2 0 ( l i t t e r o f 5) t o . 7 5 ( l i t t e r o f 8 ) . As w e l l , t h e mean l i t t e r and gravidum s i z e s from 1 9 7 3 to 1 9 7 5 are c o r r e l a t e d w i t h the f r e q u e n c y o f males c a p t u r e d i n the same year ( r = . 9 9 9 , P < - 0 5 , P i g . 1 0 ) . I f the mean l i t t e r s i z e and and juvenile sex r a t i o from populations i n the East River Valley, Colorado (Armitage and Downhower 1 9 7 4 ) are i n c l u d e d i n the l a t t e r c o r r e l a t i o n , i t remains s i g n i f i c a n t ( r = . 9 6 0 , p < . 0 5 ) . Stepwise m u l t i p l e r e g r e s s i o n s do not c l a r i f y the r e l a t i o n -s h i p s between sex r a t i o and female w e i g h t , emergence d a t e , and l i t t e r s i z e . The e f f e c t s o f emergence date and female c o l o n y - y e a r = one c o l o n y i n one y e a r , e.g., Home Colony 1 9 7 4 . Table X. J u v e n i l e sex r a t i o at weaning. Year M:F X p 1 9 7 3 53:41 1 . 5 3 2 < . 3 0 1974 1 0 3 : 8 5 1 . 7 2 3 <-20 1975 39:44 . 3 0 1 > . 5 0 T o t a l 3 . 5 5 6 < . 5 0 P o o l e d 1 9 5 : ! ' : 1 7 0 1 . 7 1 2 < . 2 0 H e t e r o g e n e i t y 1.844 > . 5 0 Table X I . Comparison of repr o d u c t i v e v a r i a b l e s between y e a r s , e x c l u d i n g y e a r l i n g s . Mean-standard e r r o r of untransformed data(n) 1974 1975 L i t t e r s i z e : Home -Colony 1 6.33(9) T o t a l 2 6.92±.560(13 L i t t e r weight(kg) 2.33-.177(8) J u v e n i l e weight(kg) .322^.013(5: Sex r a t i o 1 * .579(4) 5 Emergence date: Home Colony June 9(7) T o t a l June 9(12) Reproductive e f f o r t 1.19^.155(4); Breeding female weight 1.66^.054(8) 5.67(9) - -5.27±.536(11) 2. 10 < .10 1.97-.175(9) 1. 461 < •20 •372i.014(47) F= ;8.593 3 < .005** .492(8) 750 < • 50-June 13(8) 1. 189 < .40 June 13(9) 2. 038 = . 056 1.25-.072(7) 411 > .50 1.65^.029(8) 082 > • 90 ^Parametric means. ^Includes y e a r l i n g s . ijTwo-way a n a l y s i s of v a r i a n c e ; sex and years as independent v a r i a b l e s , Back-transformed means of data transformed by a r c s i n p, where cP=proportion males. Excludes a l i t t e r of 2. Back-transformed means of log-transformed data. F i g u r e 1 0 . C o r r e l a t i o n between j u v e n i l e sex r a t i o and mean l i t t e r s i z e at the Watch Lake c o l o n i e s 1 9 7 3 t o 1975 and i n the E a s t R i v e r V a l l e y c o l o n i e s . 6.0 « Y e a r ( s a m p l e s i z e f o r s e x r a t i o , s a m p l e s i z e f o r I i t t e r s i z e ) 5 5 1 • 5 0 1 CD CO o c CD CT CD . 45 X - E a s t R i v e r X 1 9 7 5 ( 8 3 >" > X 1973 (94,13) X I 974 (188, 23) r = .999 (B.C.) p < .0 5 r = . 9 6 0 (B.C. and Colorado ) p < . 0 5 8 Mean L i t ter S i z e / -tr weight are not s e p a r a b l e (Table V I I I ) . Both e x p l a i n about H3% o f the v a r i a n c e i n sex r a t i o . Emergence d a t e . The emergence dat e o f a l i t t e r was s i g n i f i c a n t l y c o r r e l a t e d w i t h s e v e r a l o t h e r r e p r o d u c t i v e v a r i a b l e s . I t v a r i e d w i t h the l i t t e r s i z e , the mother's w e i g h t , her age (Table I X ) , her weight g a i n from the year b e f o r e , and her r e p r o d u c t i v e e f f o r t t h a t y e ar ( F i g . 6 ) . L i t t e r s i z e and the age o f the mother do not e x p l a i n s i g n i f y i c a n t l y more o f the v a r i a n c e i n emergence dat e t h a n does the weight of the mother alone (Table V I I I ) . Together the mother's weight and her weight g a i n e x p l a i n 76% o f the v a r - . i a n c e i n emergence d a t e s o f 8 l i t t e r s (R = . 8 7 2 , p < . 0 5 ) , h e a v i e r females and t h o s e g a i n i n g the most weight i n the p r e -c e d i n g y ear weaning t h e i r l i t t e r s e a r l i e r . Mother's c o n d i t i o n . S e v e r a l f a c t o r s r e l a t i n g t o the c o n d i t i o n of the female (her w e i g h t , weight g a i n , and r e p r o -d u c t i v e e f f o r t ) , were c o r r e l a t e d w i t h the v a r i o u s r e p r o d u c -t i v e p a r a m e t e r s . What de t e r m i n e s each, o f the v a r i a b l e s ? The r e p r o d u c t i v e e f f o r t o f females v a r i e d l e s s t h a n the weight o f t h e i r l i t t e r s (F = 3 - 4 5 0 , p < . 0 2 5 ) . R e p r o d u c t i v e e f f o r t d i d not d i f f e r between y e a r s or between females of d i f f e r e n t ages (Table V I I I , I X , X I ) . I n s t e a d i t was nega-t i v e l y c o r r e l a t e d w i t h b o t h the r e p r o d u c t i v e e f f o r t o f the same female i n the p r e v i o u s year ( F i g . 11) and w i t h the weight o f t h a t y e a r ' s l i t t e r ( Table V I I ) . A female's weight a t emergence from h i b e r n a t i o n F i g u r e 1 1 . C o r r e l a t i o n between the r e p r o d u c t i v e e f f o r t o f females I n 1974 and t h e i r r e p r o d u c t i v e e f f o r t and A p r i l weight I n 1 9 7 5 -2 r=-.955 1.8.. 1 . 6 I P < .05 1.4. _ 1.2.. X X • 1.0., X •8-.6--.4 -.2 0 I 1 I — I I I I I I I ) 0.2 .4 .6 .8 1 1.2141.61.8 2 R e p r o d u c t i v e E f f o r t T974 I.95L-X 1.75. 1.55 r = -.964 p < .0 5 H 1 1 1 1 r-0 .2 .4 .6 .8 1 1.21.41.61.8 2 R e p r o d u c t i v e E f f o r t 51 ( A p r i l 3 0 ) depended on both her age and the year (Table V I I I ) . I t c o u l d not be p r e d i c t e d from her weight the p r e -v i o u s year e i t h e r i n c l u d i n g ( r = . 7 0 1 , n = 1) or e x c l u d i n g two year o l d s ( r = - . 5 3 2 , n = 5 ) 5 u n l e s s the weight o f her l i t t e r t h a t year was a l s o i n c l u d e d i n the r e g r e s s i o n (R = . 9 2 8 , n = 6 , p < . 0 6 , P i g . 1 2 ) . Indeed r e p r o d u c t i v e e f f o r t a l o n e the p r e v i o u s year was s u f f i c i e n t t o p r e d i c t the w e i g h t s of females t h r e e y e a r s and o l d e r ( F i g . 1 1 , Table V I I ) . Females g a i n e d more weight between ages one and two• than i n subsequent y e a r s (Table I X ) . The weight two y e a r and o l d e r females ( i n 1 9 7 4 ) g a i n e d between A p r i l 1974 and A p r i l 1975 depended on the weight o f t h e i r l i t t e r i n 1 9 7 4 . For every 1 . 0 kg t h e i r l i t t e r s weighed, t h e i r own weight g a i n d e c l i n e d by . 2 3 kg. One f e m a l e , n o n - b r e e d i n g as a two year o l d , g a i n e d . 6 2 kg by age t h r e e . T h i s i s l i k e the weight ga i n e d by two y e a r l i n g f e m a l e s , . 5 6 and 73 kg. The d i f f e r e n c e i n weight g a i n between y e a r l i n g s and o l d e r females may then be a d i r e c t e f f e c t o f r e p r o d u c t i o n . Energy can be u t i l i z e d f o r growth or f o r r e p r o d u c t i o n , most y e a r l i n g s p a r t i t i o n i n g i t i n t o growth, most a d u l t s i n t o r e p r o d u c -t i o n . D i f f e r e n c e between y e a r s . Some o f the r e p r o d u c t i v e parameters v a r i e d between 1974 and 1975 (Table X I ) . Gravidum and, p o s s i b l y , l i t t e r s i z e s were s m a l l e r i n 1 9 7 5 - L i t t e r s may have emerged l a t e r i n 1 9 7 5 . J u v e n i l e s were h e a v i e r t h a t y e a r . T h i s was s i m p l y a f u n c t i o n o f t h e s m a l l e r l i t t e r F i g u r e 1 2 . Dependence of the weight o f females i n A p r i l 1975 on t h e i r weight i n . A p r i l 1974 and t h e . weight o f t h e i r 1974 l i t t e r . Each p o i n t r e p -r e s e n t s the 1974 weight o f a female and her l i t t e r . B e s i d e i t i s her weight i n 1 9 7 5 . These p o i n t s d e s c r i b e a c o n t o u r s u r f a c e where the c o n t o u r l i n e s are the 1975 w e i g h t s pre-:* d i e t e d by d i f f e r e n t c o m b i n a t i o n s o f 1974 f e -male and l i t t e r w e i g h t s . Litter Weight (kg) 1974 s i z e s ( a n a l y s i s o f c o v a r i a n c e , ± p = . 6 5 9 ) . L i t t e r w e i g h t s and sex r a t i o s d i d not d i f f e r between y e a r s . Nor d i d t h e weight o f b r e e d i n g a d u l t females or t h e i r r e p r o d u c t i v e e f -f o r t v a r y . However the 1974 sample c o n t a i n e d more two year o l d s . I f t h i s d i f f e r e n c e i n age s t r u c t u r e i s c o n s i d e r e d ( a g e - s p e c i f i c ) w e i g h t s were lower i n 1975 than i n 1 9 7 4 . Mean j u v e n i l e weight i n a l i t t e r as dependent v a r i -a b l e , l i t t e r s i z e as c o v a r i a t e ; 1 9 7 4 , ri •= 71 1 9 7 5 , n = 9-55 MORTALITY M o r t a l i t y Rates J u v e n i l e s . I e s t i m a t e d a n n u a l m o r t a l i t y o f j u v e n i l e s from j u v e n i l e s c a p t u r e d and marked i n June 1 9 7 3 and June 1 9 7 4 . Only those c o l o n i e s w i t h a complete y e a r l i n g census i n 1974 and 1975 a r e i n c l u d e d (Home, O l d , and.Community H a l l ) . As I d e t e c t e d no e m i g r a t i o n o f j u v e n i l e s (see Sources o f Loss) I equate d i s a p p e a r a n c e w i t h d e a t h . Annual m o r t a l i t y of j u v e n i l e s was 6 2 . 1 $ . I t d i d not d i f f e r between y e a r s or c o l o n i e s (Table X I I ) . S e a s o n a l m o r t a l i t y r a t e s were d e t e r m i n e d f o r t h e 1974 c o h o r t o n l y . O v e r w i n t e r m o r t a l i t y was e s t i m a t e d from a sample o f j u v e n i l e s t r a p p e d or r e c o g n i z e d i n August and r e -c a p t u r e d the f o l l o w i n g s p r i n g . I t was 37•5%• O v e r w i n t e r m o r t a l i t y d i d not d i f f e r between c o l o n i e s (x = O . 6 7 , P > . 3 0 ) . M o r t a l i t y from June t o August c o u l d not be d e t e r m i n e d d i r e c t l y because not a l l j u v e n i l e s a l i v e i n August were r e -t r a p p e d and I d e n t i f i e d . A maximum e s t i m a t e of summer mor-t a l i t y can be c a l c u l a t e d from ( 1 ) the number of j u v e n i l e s t r a p p e d i n June and i d e n t i f i e d I n August p l u s (2):..the number o f j u v e n i l e s t h a t s u r v i v e d to the s p r i n g o f 1 9 7 5 but were not observed the p r e v i o u s August. T h i s o v e r e s t i m a t e s mor-t a l i t y because i t e x c l u d e s a t h i r d group, t h o s e a l i v e i n August but which d i e d b e f o r e s p r i n g . The maximum June t o August m o r t a l i t y was 4 7 . 4 % . Table X I I . Seasonal and annual m o r t a l i t y of j u v e n i l e marmots. Sample s i z e i n parentheses. Males Females T o t a l Year 1973 1974 .500(18) .647(85) = .24l Season June to August .435 August to s p r i n g .500(18) Colony Home Old P .708(24) 727(22) .80 . 312 .273(22) .500(20) .500(12) = 1.00 • 392 •375(40) .614(44) •629(35) 3 .80 T o t a l .735(49) •543(35) .621(103) 1 2 P r o b a b i l i t i e s r e f e r to X - t e s t s of independence on d i f f e r e n c e s 2between years or c o l o n i e s . Estimated by where S a = a n n u a l s u r v i v a l a n d s = A u g u s t t o S W w s p r i n g s u r v i v a l . Known maximum m o r t a l i t y was .565, .344, and .474 - f o r males, females, and both sexes r e s p e c t i v e l y . ^Includes one tagged but unsexed j u v e n i l e that s u r v i v e d . Includes Community H a l l Colony. 57 June to August m o r t a l i t y can be e s t i m a t e d from th e e s t i m a t e s o f o v e r w i n t e r and a n n u a l s u r v i v a l . M o r t a l i t y be-S tween June and August, M = 1 - W-^- where S = a n n u a l s u r v i v a l s o a w and S = o v e r w i n t e r s u r v i v a l . T h i s g i v e s a v a l u e o f 3 9 - 2 % w m o r t a l i t y between June and August, s i m i l a r t o the m o r t a l i t y o v e r w i n t e r . The d i f f e r e n c e s i n a n n u a l s u r v i v a l between males and 2 females approached s i g n i f i c a n c e (Table X I I , x = 3 - 3 2 4 , p < . 0 6 5 ) . The t r e n d i s apparent i n b o t h c o l o n i e s and b o t h seasons. A l t h o u g h the 1974 j u v e n i l e sex r a t i o d i d not d i f -f e r s i g n i f i c a n t l y from e q u a l i t y (see R e p r o d u c t i o n ) , the A p r i l - M a y 1975 sex r a t i o o f y e a r l i n g s , 2 1 : 1 6 o r . 5 8 : 1 , d i f -f e r e d s i g n i f i c a n t l y from b o t h 1 :1 (p < . 0 5 ) and the p r e v i o u s summer j u v e n i l e sex r a t i o (p < . 0 2 ) . The t r e n d was apparent i n a l l f o u r c o l o n i e s w i t h y e a r l i n g s p r e s e n t . The s i g n i f i c a n t change i n sex r a t i o a l s o s u g gests t h a t male j u v e n i l e s s u r v i v e l e s s w e l l t h a n f e m a l e s . I examined the r e l a t i o n s h i p s between the s u r v i v a l o f j u v e n i l e s and t h e i r weight at weaning, t h e i r growth from June u n t i l August, and t h e i r weight b e f o r e h i b e r n a t i o n . The weight of j u v e n i l e s at weaning d i d not s i g n i f i c a n t l y a f f e c t t h e i r p r o b a b i l i t y o f s u r v i v i n g t h e i r f i r s t y e a r (Table X I I I ) . The growth r a t e o f males t h a t s u r v i v e d t h e i r f i r s t y e a r , 1 9 . 8 g/day (n = 3 1 ) was g r e a t e r t h a n the growth r a t e of males t h a t d i e d , 1 6 . 9 g/day ( n = 8 3 ; a n a l y s i s o f c o v a r i a n c e , o n e - t a i l e d t e s t , p = . 0 1 8 ) . The growth r a t e o f females t h a t s u r v i v e d ( 1 5 . 2 g/day, n = 5 3 ) d i d not d i f f e r from t h o s e t h a t d i e d 58 Table XIII. The e f f e c t of the weight of j u v e n i l e s on t h e i r s u r v i v a l . Mean weight ±standard error(sample s i z e ) , Juveniles that. Juveniles that die survive 1 year before-1 year Weight at emergence (kg) Males Females F 1 . P 0.307-.022(8) 0.344±.027(10) 0. 743 ,.50 0.301-.023(23) 0.299-.029(14) Weight i n August (kg) Males Females F 1 P 1.58i.46(9) 1.28^.054(12) 3-599 .10 1.34-.155(6) I.l8±.118(5) Two-way analysis of variance. 59 ( 1 4 . 5 g/day, n = 5 1 , P = . 3 0 6 ) . O v e r w i n t e r s u r v i v a l o f j u v e -n i l e s may have depended on t h e i r weight i n August (Table X I I I ) . The number o f y e a r l i n g s s u r v i v i n g from a l i t t e r was not c o r r e l a t e d w i t h i t s s i z e ( r = . 5 0 9 , n = 8 ) , i t s weight (r = . 6 5 2 , n = 7) or i t s emergence date ( r = . 3 8 8 , n = 8 ) . Nor d i d the s u r v i v a l of. j u v e n i l e s depend on the s u r v i v a l of t h e i r mother. At the Old Colony, I removed a l l l a c t a t i n g females i n J u l y . The Home Colony females were u n d i s t u r b e d . Yet j u v e n i l e s u r v i v a l d i d not d i f f e r between c o l o n i e s (Table X I I ) . I n summary, j u v e n i l e males appear t o s u f f e r g r e a t e r m o r t a l i t y t h a n f e m a l e s . The growth r a t e between June land August and the weight i n August may a f f e c t o v e r w i n t e r s u r -v i v a l . The y e a r , c o l o n y , l i t t e r s i z e , emergence d a t e , and s u r v i v a l o f the mother had n e g l i g i b l e e f f e c t on j u v e n i l e s u r v i v a l . A d u l t s and y e a r l i n g s . A d u l t and y e a r l i n g m o r t a l i t y was e s t i m a t e d d u r i n g two p e r i o d s each y e a r . One extends from emergence from h i b e r n a t i o n t o J u l y 1 ( s p r i n g ) , the o t h e r from J u l y 1 u n t i l the subsequent s p r i n g (summer and w i n t e r ) . S p r i n g m o r t a l i t y was based on those i n d i v i d u a l s seen or cap-t u r e d by May 15 and not r e s i g h t e d o r r e c a p t u r e d on or a f t e r J u l y 1 . Summer and w i n t e r m o r t a l i t y was based on t h o s e seen between June 24 and J u l y 8 and not r e c a p t u r e d t h e subsequent s p r i n g . Annual m o r t a l i t y , M, was c a l c u l a t e d from the 60 e q u a t i o n (1-S )N + (1 - S )S N M = s w s N where N = t o t a l number seen by May 15 each y e a r , S = s p r i n g s s u r v i v a l and S = summer and w i n t e r s u r v i v a l . Annual mor-w t a l i t y was e s t i m a t e d a t 3 2 . 5 % - I t v a r i e d l i t t l e between y e a r l i n g s and a d u l t s (Table XIV) or between y e a r s (Table XV) . The e s t i m a t e s of the m o r t a l i t y r a t e s r e l y on two a s -sumptions. ( 1 ) The m o r t a l i t y o f marked i n d i v i d u a l s does not d i f f e r from t h a t of unmarked a n i m a l s . ( 2 ) Tag l o s s d i d not cause l i v e i n d i v i d u a l s to be assumed dead. B i a s from • the l a t t e r assumptions was m i n i m i z e d by t o e - c l i p p i n g most a n i m a l s . I f the assumptions are not v a l i d , t hey s h o u l d e r r i n t h e same d i r e c t i o n : m o r t a l i t y w i l l be o v e r e s t i m a t e d . Sources of Loss The f a t e o f some i n d i v i d u a l s t h a t d i s a p p e a r e d from the p o p u l a t i o n s was known (Table XVI to X V I I I ) . However the f a t e o f most, p a r t i c u l a r l y j u v e n i l e s , was unknown. The p o t -e n t i a l l y i m p o r t a n t s o u r ces o f l o s s were d i s e a s e , p r e d a t i o n and h u n t i n g , h i b e r n a t i o n , and e m i g r a t i o n . A l s o one marmot was a p p a r e n t l y s t r u c k by a c a r . S e v e r a l d i e d i n t r a p s , but were o m i t t e d from m o r t a l i t y e s t i m a t e s . Two o r t h r e e l i t t e r s d i e d a f t e r t h e i r mother d i e d or d e s e r t e d . There was no e v i -dence o f deaths from s t a r v a t i o n or p a r a s i t e s . 61 Table XIV. Seasonal and annual m o r t a l i t y r a t e s of y e a r l i n g s and a d u l t s . Sample s i z e i n parentheses. Females Males Y e a r l i n g s Y e a r l i n g s Adults and adults' Y e a r l i n g s A d u l t s T o t a l A p r i l to ; ? June .111(27) .105(19) .109(46) .182(11)" .333(6) .143(63.) J u l y to A p r i l .190(21) .200(15) .211(57) .263(19) •000(4) . .213(80) Annual .280 .284 .297 -3972 .333 -325 i n c l u d e s females whose age i s . uhknowr- • This r a t e i s based on 6 r e s i d e n t s and 5 known emigrants. I t assumed other l o s s was from emigration and that the m o r t a l i t y r a t e of those emigrants was the same. I f i n s t e a d one assumes the other 6 y e a r l i n g males d i e d , the s p r i n g m o r t a l i t y r a t e i s .471(n=17) and annual r a t e Is .610. 6 2 Table XV. V a r i a t i o n i n seasonal and annual m o r t a l i t y r a t e s of y e a r l i n g s and a d u l t s from J u l y 1973 to May 1976. Sample s i z e i n parentheses. April/May to June J u l y to April/May Annual 1973 - .214(14) 1974 .211(19) .087(23) .279 1975 .114(44) .227(22) .315 63 Table XVI. Time and causes of deaths of j u v e n i l e marmots, ex c l u d i n g t r a p p i n g . Year Approximate date of death Colony Sex Cause 1973 . J u l y 1 Johnson's Pond 2M,1F 1 shot 1974 June 21-22 Old M a v i a n predator? l a t e June Old 2M disease or shbt J u l y 12 Fraser M dog J u l y 12 Fraser M predator 1975 June 23 Home M unknown J u l y 1 Johnson's Pond F shot J u l y 9 Home ? dog August Home ? 3 shot 2 2 males and 1 female Chest c a v i t y was open. There were a few scr a t c h e s on the shoulders 6 4 Table XVII. Time and cause of l o s s of y e a r l i n g marmots. [ : ! : Date emigrants Sex Colony Year Date of l o s s Cause observed at new l o c a l i t y Female Male Home 1974 May 24 c o c c i c i o s i s ? — Home 1974 June 9 c o c c i d i o s i s -Old 1975 June 16-21^ emigration? -Home 1975 June 24 shot -Home 1973 a f t e r June 27 unknown -Home 1975 June 29-July 10 unknown(emigration?) -Bank' s cabin 1975 J u l y 8 shot -Home 1973 a f t e r J u l y 16 unknown(hibernation?) — Old 1975 May 22-28 emigration - June 10 Home 1975 May 25-28 emigration June 3 Home 1974 a f t e r May 27 unknown(emigration?) -Home 1975 May 29 e m i g r a t i o n May 29 Home 1975 May 28-30 e m i g r a t i o n May 30 Home 1975 May 28-June 2 emigration? -Old 1975 June 3-9 emigration? -Old 1975 June 4-9 emigration? ? Old 1975 June 5-9 emigr a t i o n June 12 Johnson' s Pond 1975 June 8 h i t by c a r 3 June 8 Old 1975 June 8-12 emigration? -Old 1975 June 10-16 emigr a t i o n June 18 Home 1974 June 10-20 emig r a t i o n J u l y 2 Home 1974 June 11-July 8 unknown(emigration?) -Old 1975 June 16-June 21 emigration August 31 Johnson' s Pond 1975 June 22 shgt -Home 1975 a f t e r J u l y 18 unknown -Home 1973 a f t e r August 8 unknown(hibernation?) -The f i r s t date i s the l a s t day the y e a r l i n g was seen i n the colony. For 1975 obs e r v a t i o n s , the second date i s the day by which 90$ of the._pther a d u l t s and y e a r l i n g s had been seen. For 1974, the second date i s 5-75 observation hours (the mean number of hours r e q u i r e d to 2 l o c a t e 90% of the p o p u l a t i o n i n 1975) a f t e r the f i r s t date. The y e a r l i n g was seen on a road on June 12 and i n a new colony on oJune 15. ^This y e a r l i n g had emigrated from h i s n a t a l colony between May 28 and June 6. 65 Table XVIII. Time and cause of death of a d u l t marmots. Sex Colony Year Date Cause Female Home 1973 a f t e r June 15 unknown Home 1974 June 9 c o c c i d i o s i s Community H a l l 1974 approx. June 11 c o c c i d i o s i s ? Home 1974 a f t e r June 11 unknown Fraser 1974 June 27 c o c c i d i o s i s Home 1974 a f t e r J u l y 19 unknown Male Community H a l l 1975 approx. May 25 shot Old 1975 June 23-July 9 unknown 6 6 From May 23 t o June 2 7 , 1974 f i v e marmots at t h r e e c o l o n i e s a p p a r e n t l y d i e d o f d i s e a s e . Three were a u t o p s i e d . The cause o f death was c o c c i d i o s i s . C o c c i d i o s i s i s caused by a p r o t o z o a n ( F a m i l y C o c c i d i a e ) which a t t a c k s the w a l l o f the d i g e s t i v e t r a c t and a f f e c t s a b s o r p t i o n o f f o o d . Symptoms were weight l o s s , d i a r r h e a , and, towards d e a t h , poor motor c o n t r o l . T h i s was t h e o n l y time d u r i n g the study t h a t s i c k a n i m a l s were seen. P r e d a t o r s i n c l u d e d man, c o y o t e s ( C a n i s l a t r a n s ) , dogs., and r a p t o r s . Red f o x e s (Vulpes f u l v a ) l i v e d i n the a r e a , . but were never seen at the c o l o n i e s . Hunters were asked not to shoot marmots d u r i n g the s t u d y . A l t h o u g h a t l e a s t a few were shot ( T a b l e s XVI to X V I I I ) , m o r t a l i t y from t h i s s ource would o r d i n a r i l y be g r e a t e r . M o r t a l i t y e s t i m a t e s d u r i n g the study may then u n d e r e s t i m a t e u s u a l m o r t a l i t y i n t h e s e pop-u l a t i o n s . I saw co y o t e s f r e q u e n t l y a t the c o l o n i e s . But o n l y once d i d I observe what was l i k e l y a s u c c e s s f u l a t t a c k . I t oc c u r e d on the wooded f r i n g e o f t h e Home Colony. The co y o t e q u i c k l y d i s a p p e a r e d I n the woods. An a t t a c k on a s i c k marmot would have been s u c c e s s f u l had not h o r s e s i n t e r v e n e d and chased away the c o y o t e . Two l o c a l r e s i d e n t s observed a coyote k i l l i n g an a d u l t o r y e a r l i n g a t t h e F r a s e r Colony. The f r e q u e n c y o f v i s i t s by coyo t e s v a r i e d c o n s i d e r a b l y be-tween y e a r s (Table X I X ) . I n 1974 they l i k e l y v i s i t e d t he Home Colony d a i l y . I n 1975 they were never seen. Dogs k i l l e d two j u v e n i l e marmots. A t h i r d dog was 6 7 Table XIX. • Frequency of observations of coyotes at the Home Colony. Sample s i z e (hours or days) i n parentheses. 2 Coyotes/observation coyotes/day hour May June J u l y Aug. T o t a l May June J u l y Aug T o t a l 1973 - .18(22).0(2l) 3 o(4) 4 .08(49) - -36(11) 0(8) 3 0(2) 4 .19(21) 1974 0(7) -35(17) .20(10).27(11)-24(45) 0(4).5(8) .4(5) .4(5 )• - 36(22) 1975 0(26) 0(21)'5 0 ( - ) 6 - 0(>49) 0(12)0(8) 7 0 ( - ) 6 0(>20) 20nly observation periods of more than 20 min. are i n c l u d e d . oOnly days w i t h more than 1 hour.of continuous o b s e r v a t i o n . jjAlso one coyote seen while I was not i n o b s e r v a t i o n tower. c-Also three s i g h t i n g s of coyotes while not i n o b s e r v a t i o n tower. ^Includes some estimates of observation times. -Time not u s u a l l y recorded. 12 days. An estimate, as observation time not always recorded. 6 8 seen c a r r y i n g a dead marmot. L o c a l r e s i d e n t s u s u a l l y t r i e d t o p r e v e n t t h e i r dogs from k i l l i n g marmots at t h e study c o l -o n i e s . P o t e n t i a l a v i a n p r e d a t o r s were b a l d e a g l e s ( H a l i a e e t u s l e u c o c e p h a l u s ) , g o l d e n e a g l e s ( A q u i l a c h r y s a e t o s ) , r e d - t a i l e d hawks (Buteo j a m a i c e n s i s ) , goshawks ( A c c i p i t e r g e n t i l i s ) , and marsh hawks ( C i r c u s c y a n e u s ) . One j u v e n i l e marmot appeared t o have been k i l l e d by an a v i a n p r e d a t o r (Table X V I ) . Otherwise t h e r e was l i t t l e e v i d e n c e o f p r e d a t i o n by r a p t o r s . At the Home Colony, t h e r e w e r e . s i x s i g h t i n g s o f r a p t o r s i n a p p r o x i m a t e l y 150 hours of o b s e r v a -t i o n . D u r i n g the same p e r i o d 15 c o y o t e s were seen. A l s o , marmots r e a c t e d l e s s s t r o n g l y t o a r a p t o r t h a n o t h e r p r e d -a t o r s . When a c o y o t e , dog, or man e n t e r e d the c o l o n y , one marmot would c h i r p ( a l a r m c a l l ) c o n t i n u o u s l y , and a l l would r e t u r n to and s t a n d by t h e i r burrows. The presence o f a r a p t o r d i d not always e l i c i t c h i r p i n g or even an i n t e r r u p t i o n o f a c t i v i t i e s (Table XX). J u v e n i l e s . An e x p l a n a t i o n o f j u v e n i l e l o s s s h o u l d account f o r the g r e a t e r l o s s o f male j u v e n i l e s . One would expect e q u a l m o r t a l i t y o f males and females d u r i n g h i b e r -n a t i o n . P o t e n t i a l s o u r c e s of j u v e n i l e l o s s d u r i n g the a c t i v e season are d i s e a s e , p r e d a t i o n , and e m i g r a t i o n . The y e a r on which the j u v e n i l e s m o r t a l i t y r a t e s are based, 1 9 7 4 , was a l s o the y e a r i n which c o c c i d i o s i s k i l l e d s e v e r a l a d u l t and y e a r l i n g marmots i n l a t e s p r i n g . A l t h o u g h Table XX% Response of marmots to raptors. Drops or lands Response of marmots A c t i v i t y of-b i r d 1 No c h i r p i n g C h i r p i n g and at l e a s t some continue a c t i v i t i e s C h i r p i n g and a l l r e t u r n to burrows Perched F l y i n g mainly eagles but 1 or 2 ospreys. 70 c o c c i d i o s i s may have c o n t r i b u t e d to the poor summer s u r v i v a l o f j u v e n i l e s , i t cannot count f o r t h e p o o r e r s u r v i v a l o f males. Coyote p r e d a t i o n i s a more p r o b a b l e s o u r c e of most j u v e n i l e m o r t a l i t y . 1974 was the year i n which c o y o t e s most f r e q u e n t l y v i s i t e d the c o l o n i e s ( T able X I X ) . Males may be more s u s c e p t i b l e to p r e d a t i o n i f they are l e s s wary t h a n f e m a l e s , move g r e a t e r d i s t a n c e s , o r h i b e r n a t e l a t e r . J u v e -n i l e male B e l d i n g ground s q u i r r e l s (Spermophilus b e l d i n g s ) have l a r g e r home ranges t h a n females and may e n t e r h i b e r n a -t i o n l a t e r (Morton, M a x w e l l , and Wade 1 9 7 4 ) . Swainson's hawks (Buteo s w a i n s o n i ) t a k e more j u v e n i l e male R i c h a r d s o n ' s ground s q u i r r e l s t h a n females (Schmutz 1 9 7 7 ) -P o s s i b l y some j u v e n i l e males emigrate b e f o r e h i b e r -n a t i o n . T h e i r w e i g h t s i n August (mean = 1 . 4 8 kg) o v e r l a p those o f y e a r l i n g s when they e m i g r a t e about June 1 (mean = 1 . 6 7 k g ) . Body s i z e and h i g h numbers of j u v e n i l e s may a c t as s t i m u l i f o r the e x p u l s i o n o f young males. A r m i t a g e and Downhower ( 1 9 7 4 ) and Armitage ( p e r s o n n a l communication) sug-gest t h a t j u v e n i l e y e l l o w - b e l l i e d marmots at s m a l l .. .• " s a t e l l i t e " c o l o n i e s (but not t y p i c a l c o l o n i e s ) may e m i g r a t e b e f o r e h i b e r n a t i o n . However none o f 187 t a g g e d . j u v e n i l e s i n t h i s s tudy were c a p t u r e d away from t h e i r n a t a l c o l o n y b e f o r e May 29 o f t h e i r second y e a r . One cannot c o n c l u s i v e l y d e t e r m i n e the major source o f j u v e n i l e l o s s d u r i n g the a c t i v e season. However coyote p r e d -a t i o n i s p r o b a b l y more i m p o r t a n t t h a n d i s e a s e or e m i g r a t i o n 71 because ( 1 ) some coyote p r e d a t i o n was observed and ( 2 ) p r e d -a t i o n can account f o r t h e d i f f e r e n t m o r t a l i t y r a t e s o f t h e sexes. N e i t h e r d i s e a s e nor e m i g r a t i o n s a t i s f y b o t h t h e s e c r i t e r i a . The former cannot account f o r the d i f f e r e n t i a l m o r t a l i t y and the l a t t e r was never o b s e r v e d . A d u l t s and y e a r l i n g s . The major source o f l o s s o f y e a r l i n g males was e m i g r a t i o n (Table X X I ) . F o r t y - s e v e n p e r -cent o f the 77% a n n u a l l o s s o f y e a r l i n g : males was a t t r i b u t e d t o e m i g r a t i o n . The r e s u l t i n g e s t i m a t e o f e m i g r a t i o n , 3 6 % , may be low. I f the c o n s t r a i n t s on the sample used t o e s t i -mate l o s s i n Ta b l e s XIV and XXI a r e r e l a x e d (see M o r t a l i t y R a t e s : a d u l t s and y e a r l i n g s ) , the e s t i m a t e i s h i g h e r . F o r t h i s . s a m p l e , ( 1 ) t h e l a t e s t i n i t i a l c a p t u r e date i s extended t o May 3 1 (which s h o u l d reduce l o s s ) . ( 2 ) C o l o n i e s t h a t were t r a p p e d i n t e n s e l y , but s t i l l i n c o m p l e t e l y , are i n c l u d e d (which s h o u l d i n c r e a s e l o s s ) . ( 3 ) A l l l o s s not known t o be a f t e r June 20:'.is c o n s i d e r e d e m i g r a t i o n (which s h o u l d I n c r e a s e l o s s ) . T h i s sample y i e l d s 67% e m i g r a t i o n (n = 2 7 ) . Loss from the e x p e r i m e n t a l c o l o n i e s (see D i s p e r s a l ) i n which the s o c i a l s t r u c t u r e was m a n i p u l a t e d i s i n c l u d e d i n b o t h t h e s e e s t i m a t e s . The m a n i p u l a t i o n s l i k e l y r educed y e a r l i n g male e m i g r a t i o n i n one c o l o n y . I f i t i s e x c l u d e d , t h e estimate;. i s 72% e m i g r a t i o n (n = 1 8 ) . I f o n l y c o n s t r a i n t ( 1 ) I s r e l a x e d , e m i g r a t i o n i s 6 4 % (n = 2 2 ) from a l l t h e c o l o n i e s and 77% (n = 1 3 ) from a l l except t h e e x p e r i m e n t a l c o l o n y . The major source o f l o s s o f y e a r l i n g females and a d u l t s o f b o t h sexes was not known. Few y e a r l i n g females 72 Table XXI. Pr o p o r t i o n of l o s s of y e a r l i n g and a d u l t marmots to d i f f e r e n t sources. Sample Emigration M o r t a l i t y Unknown s i z e ' Disease Hunting Females 17 0.00 0.24 0.06 0. 71 Adult males 2 0.00 0.00 0.50 0. 50 Y e a r l i n g malesl7 0.472 0.00 0.06 0. 47 T o t a l 36 0. 22 0.11 0.08 0. 58 Same sample on which m o r t a l i t y r a t e s based, Table X V I I I . 5 became e s t a b l i s h e d at new c o l o n i e s or p e r i p h e r a l s i t e s of which 1 was l a t e r k i l l e d by a car. One was seen f o r a few days-at a new colony. Two were assumed emigrants as they disappeared between l a t e May and l a t e June. 73 e m i g r a t e d . Of 38 y e a r l i n g females t r a p p e d or seen a f t e r June 5 , o n l y 5% were not i n t h e i r n a t a l c o l o n y . D u r i n g the same p e r i o d , 50% o f 20 y e a r l i n g males were seen away from t h e i r n a t a l c o l o n y . There was no e v i d e n c e o f e m i g r a t i o n of a d u l t s . Y e a r l i n g and a d u l t m o r t a l i t y was h i g h d u r i n g May and June (Table XV). H u n t i n g e f f o r t was n e g l i g i b l e a t the c o l -o n i e s on which the m o r t a l i t y e s t i m a t e s were based. I n the s p r i n g o f 1974 coyote p r e d a t i o n and d i s e a s e may have caused most d e a t h s . I n 1975 t h e r e was no evi d e n c e of d i s e a s e . Coyotes may have been the major source of m o r t a l i t y . 74 DISPERSAL E m i g r a t i o n Y e a r l i n g males e m i g r a t e d from a p p r o x i m a t e l y May 25 t o June 19 (Table X V I I ) . E i g h t y - f i v e p e r c e n t o f 13 e m i g r a n t s had d i s p e r s e d by a p p r o x i m a t e l y June 1 3 . The mean date o f e m i g r a t i o n was June 5 3 and median date June 6 . S i g h t e d e m i g r a n t s moved a mean d i s t a n c e o f 2 . 4 5 ± . 5 5 7 km (Table X X I I ) . T h i s f i g u r e s h o u l d u n d e r e s t i m a t e a c t u a l d i s t a n c e t r a v e l l e d f o r t h r e e r e a s o n s . ( 1 ) Marmots l i k e l y f o l l o w open r o u t e s , o r at l e a s t a more c i r c u i t o u s r o u t e t h a n a s t r a i g h t l i n e . ( 2 ) The p r o b a b i l i t y o f s e e i n g an emigrant l i k e l y d e c r e a s e s w i t h the d i s t a n c e moved. ( 3 ) At l e a s t t h r e e d i s p e r s i n g y e a r l i n g s c o n t i n u e d moving (or d i e d ) a f t e r b e i n g s i g h t e d . One i n d i v i d u a l t r a v e l l e d 3 - 3 7 km i n at most 3 days ( 1 . 1 2 km/day). Another moved . 9 7 km d u r i n g one day. At l e a s t 27% o f e m i g r a t i n g y e a r l i n g s r e e s t a b l i s h e d themselves i n new c o l o n i e s (Table X X I I I ) . Another 23% o f p o s s i b l e e m i g r a n t s (Table X X I I I ) were seen at p e r i p h e r a l s i t e s . These s i t e s d i f f e r e d form c o l o n i e s I n t h a t no young, and p o s s i b l y no a d u l t s , were p r e s e n t . They were a l s o s m a l l e r i n a r e a . Four were on r o a d s i d e s . A l l burrows were I n s t u m p - p i l e s , r o c k p i l e s or a bank. A f i f t h s i t e was under two abandoned b u i l d i n g s . Y e a r l i n g males t h a t e m i g r a t e d weighed l e s s t h a n t h o s e r e m a i n i n g i n t h e i r n a t a l c o l o n y . The we i g h t s o f y e a r l i n g s T a b l e - X X I I . D i s t a n c e moved by e m i g r a t i n g y e a r l i n g s . 75 Year N a t a l Colony Sex D i s t a n c e (km) 1974 Home M .74 Home M • 75 Home or Old ? >1.01 or>1.54 1 Home or Old 9 >6.2 or>6.7 1 Home M 70 Home M > . 78 Home M 1 .97 Old M 2. • 49 Old M 2. .67 Old M 3. .64 Old M . 60 + F r a s e r F 1. .7 Johnson's Pond M 6. . 2 Mean - St a n d a r d e r r o r 2.45-.557 S h o r t e r d i s t a n c e used i n c a l c u l a t i o n - . o f mean. Marmot seen t w i c e . S t r a i g h t - l i n e d i s t a n c e moved was 3-64 km. Table X X I I I . P a t e o f e m i g r a t i n g y e a r l i n g s F a t e L o c a t i o n 1974 1 9 7 5 T o t a l S u r v i v e d D i e d Unknown new c o l o n i e s p e r i p h e r a l s i t e s p e r i p h e r a l s i t e s no known burrows Never' r e s i g h t e d aft'.er May 3 0 t o June 24 •' Never r e s i g h t e d a f t e r May 3 t o 2 7 ' ' I2 0 1 5" 2 2' 0 4 3 7 3 2 1 5 4 T o t a l 17 22 pOne d i s a p p e a r e d a f t e r 2 t o 7 days. ^Disappeared a f t e r a p p r o x i m a t e l y one week. ^ I n c l u d e s one female y e a r l i n g c-Likely e m i g r a t e d . P o s s i b l y emigrated.. .-77 c a p t u r e d i n b oth May and June 1975 were l i n e a r l y i n t e r p o l a t e d t o e s t i m a t e t h e i r June 1 w e i g h t s . The mean time between w e i g h i n g s was 21 days. The mean r a t e o f g a i n d u r i n g t h a t p e r i o d was . 0 2 5 ± . 0 0 2 9 kg/day (n = . 1 1 ) . An a d d i t i o n a l 9 y e a r l i n g s were weighed o n l y once between May 15 and June 1 8 . T h e i r June 1 w e i g h t s were e s t i m a t e d u s i n g t h e mean r a t e o f g a i n o f the f i r s t group. The mean weight o f seven male y e a r l i n g s which remained r e s i d e n t s was 1 . 9 2 ± . 0 8 9 5 kg. The mean weight o f t h i r t e e n d i s p e r s i n g y e a r l i n g s was 1 . 6 7 ± . 0 4 8 1 kg. These w e i g h t s are s i g n i f i c a n t l y d i f f e r e n t (t = 5 . 7 7 7 ; P < . 0 0 1 ) . . What causes y e a r l i n g y e l l o w - b e l l i e d marmots t o emi^ g r a t e ? The l i g h t e r weight o f d i s p e r s i n g y e a r l i n g s s u g gests t h a t the cause may be b e h a v i o u r a l . S m a l l e r y e a r l i n g s c o u l d be more e a s i l y e x c l u d e d by l a r g e r i n d i v i d u a l s . Downhower ( 1 9 6 8 ) suggests t h a t a d u l t females w i t h l i t t e r s may e x p e l y e a r l i n g s . Armitage ( 1 9 7 4 ) contends t h a t the presence of a d u l t males i s n e c e s s a r y f o r male e m i g r a t i o n . To t e s t be-tween the s e hypotheses I compared d i s p e r s a l between c o l o n i e s from which e i t h e r the a d u l t females or a d u l t males had been removed. The Home and Old C o l o n i e s were chosen f o r the ex-periment because they d i f f e r e d l i t t l e i n o t h e r v a r i a b l e s ; w h i c h m i g h t s - a f f e c t e m i g r a t i o n . . They were s i m i l a r i n number, age s t r u c t u r e , and sex r a t i o . Both were i n l a r g e f i e l d s o f e s t a b l i s h e d v e g e t a t i o n w i t h one or t h r e e b u i l d i n g s p r e s e n t . T h e i r c e n t r e s were . 7 6 km a p a r t . I n 1 9 7 4 , 91 young were tagged at t h e s e c o l o n i e s . 78 A d u l t and y e a r l i n g females were removed from the Old Colony d u r i n g J u l y and August. I removed y e a r l i n g males from t h e Home Colony the same summer, and a d u l t males t h e next s p r i n g a f t e r b r e e d i n g . I n 1975 e m i g r a t i o n o f y e a r l i n g s was com-pared between the two c o l o n i e s . Female y e a r l i n g e m i g r a t i o n was m i n i m a l , i f e x i s t a n t , u n l e s s i t o c c u r r e d a f t e r J u l y 1 . I t d i d not d i f f e r between c o l o n i e s . Of 12 y e a r l i n g females at t h e Home Colony, a l l remained u n t i l a t l e a s t June 30 w i t h the e x c e p t i o n o f one which was s h o t . Another d i s a p p e a r e d i n e a r l y J u l y . At the Old Colony, 10 o f 11 females remained a t June 3 0 . One d i s -appeared between June 16 and June 2 1 . She was one o f two y e a r l i n g females untagged when i n i t i a l l y c a p t u r e d . As she was not c a p t u r e d u n t i l May 2 6 , t h e r e i s some p o s s i b i l i t y she was an immigrant. The F r a s e r Colony was r e g u l a r l y t r a p p e d , but l i k e l y not c o m p l e t e l y censured because o f i t s s i z e . At l e a s e 7 o f 11 females t r a p p e d t h e r e i n May were p r e s e n t a f t e r June 3 0 . E m i g r a t i o n o f male y e a r l i n g s d i f f e r e d between the Home and Old C o l o n i e s (Table X X I V ) . A l l males e m i g r a t e d from t h e Old Colony. A l s o one t a g g e d , but unsexed, y e a r l i n g e m i g r a t e d . I t too was l i k e l y a male. Less t h a n h a l f t h e males e m i g r a t e d from the Home Colony. The number o f emi-g r a n t s may have been a f f e c t e d by t h e f a i l u r e t o remove a l l the a d u l t males from the Home Colony. One remained t h r o u g h -out the p e r i o d o f e m i g r a t i o n u n t i l J u l y 9- Another was shot June 6 a f t e r he was observed h a r a s s i n g a y e a r l i n g male. T a b l e ' - X X r v . E m i g r a t i o n of y e a r l i n g males from the Home ( a d u l t male r e m o v a l ) C o l o n y and 0 1 d ( a d u l t female r e m o v a l ) C o l o n y . Number o f y e a r l i n g males R e s i d e n t s E m i g r a n t s T o t a l Home Colony 5 4 9 Old Colony 0 7 7 T o t a l 5 11 16 Test o f independence w i t h Y a t e s ' c o r r e c t i o n , G= 3 - 7 9 4 , p< . 0 6 80 There was no f u r t h e r e m i g r a t i o n a f t e r t h a t d a t e . B e f o r e c o n s i d e r i n g the outcome of the experiment i n terms of the o r i g i n a l h y p o t h e s e s , one s h o u l d c o n s i d e r two a u x i l a r y hypotheses a l s o t e s t e d . F i r s t , d e n s i t y o f a d u l t s was a l s o m a n i p u l a t e d . The number o f a d u l t s was reduced i n both c o l o n i e s , but more so i n the female removal c o l o n y ( O l d , T able XXV). I f a d u l t numbers a f f e c t y e a r l i n g e m i g ra- i: t i o n , one would expect g r e a t e r e m i g r a t i o n from the Home Colony. However, I observed the o p p o s i t e . S e c o n d l y , the a d u l t sex r a t i o was m a n i p u l a t e d . I f a d u l t males e x c l u d e y e a r l i n g males as a d i r e c t r e s u l t o f c o m p e t i t i o n f o r females d u r i n g b r e e d i n g , t h e n the a d u l t sex r a t i o , r a t h e r t h a n the a b s o l u t e number o f a d u l t males may be the c r i t i c a l c o n d i t i o n . An excess of a d u l t males over f e -males s h o u l d t h e n i n c r e a s e male e m i g r a t i o n . T h i s i s c o n s i s -t e n t w i t h the outcome of the e x p e r i m e n t . However, b r e e d i n g o c c u r s i n A p r i l (see P h e n o l o g y ) . Y e a r l i n g s do not b e g i n e m i g r a t i n g b e f o r e May 25. The a d u l t sex r a t i o t h e n s h o u l d not a f f e c t y e a r l i n g e m i g r a t i o n . N e i t h e r a u x i l a r y h y p o t h e s i s s h o u l d a f f e c t the i n t e r p r e t a t i o n o f the r e s u l t s i n terms of the o r i g i n a l h y p o t h e s i s . The r e s u l t s r e f u t e the c o n t e n t i o n t h a t a d u l t f e males e x p e l y e a r l i n g s from the p o p u l a t i o n . They are c o n s i s t e n t w i t h the h y p o t h e s i s t h a t a d u l t males cause y e a r l i n g males t o e m i g r a t e . Table XXV. Number of adults i n the experimental col o n i e s , mid-May to mid-June 1975 Adult males Adult females T o t a l Home Colony 2,.then 1 10 12 or 13 Old Colony 7 1 8 I m m i g r a t i o n O v e r a l l , e m i g r a t i o n exceeded i m m i g r a t i o n . I n 1974 a t the Home Colony i m m i g r a t i o n e q u a l l e d o r exceeded e m i g r a t i o n . I n 1975, e m i g r a t i o n was g r e a t e r t h a n i m m i g r a t i o n at bo t h the Home and Old C o l o n i e s ( c f . T a b l e s XXIV and XXVI). L i k e emi-g r a t i o n , the sex r a t i o f a v o u r e d males. The e a r l i e s t known immigrant was on May 29- The r a t e o f i m m i g r a t i o n was too low t o t e s t any hypotheses r e g a r d i n g the c o n t r o l o f immi-g r a t i o n . 83 Table XXVI. Numbers of Immigrants and t r a n s i e n t s 1974 1975 Immigrants immigrants Transients Immigrants Transients t r a n s i e n t s H o m e 3 X or 4 1 T Old no observations Community H a l l 1 ? 1 2 0 0 1 0 0 1 0 includes one female 8 4 POPULATION DENSITY AND RATE OP INCREASE The d e n s i t y of a d u l t s and y e a r l i n g s a t the Home Colony ranged from 3 . 9 5/ha i n August 1 9 7 3 t o 9 - 2 1/ha i n A p r i l 1 9 7 5 . T h i s r e p r e s e n t e d up t o 1 . 3 0 a d u l t s and y e a r -l i n g s per burrow. The r a t e o f i n c r e a s e , r , can be c a l c u l a t e d d i r e c t l y i f a p o p u l a t i o n has been enumerated d u r i n g more t h a n one yea r . Where No = number i n i n i t i a l c e n sus, N^ = number i n l a t e r census, and t = number o f y e a r s between censuses. I n o n l y the Home Colony were most o r a l l o f the marmots marked each year (Table X X V I I ) . I n 1974 and 1975 the r e s i d e n t s were marked i n l a t e A p r i l and e a r l y May. These f i g u r e s i n d i c a t e an r o f . 4 2 0 . However, i n 1974 two r e s i d e n t s and two immi-g r a n t s were removed (Table X X V I I ) . One can compensate f o r the removals by i n c r e a s i n g the 1975 numbers by the p r o b a b i l -i t y o f s u r v i v a l o f the f o u r removed marmots (see Table XIV) to 3 8 . 0 . T h i s adjustment g i v e s r o f . 5 0 2 . The 1973 census i s not comparable t o the o t h e r y e a r s . I t was conducted i n l a t e June a f t e r m o r t a l i t y , y e a r l i n g male e m i g r a t i o n , and i m m i g r a t i o n may have a f f e c t e d numbers. As w e l l , one a d u l t male d i e d d u r i n g h a n d l i n g . However, t h e female segment o f the p o p u l a t i o n might p r o v i d e a r e l i a b l e Table XXVII. C o m p o s i t i o n o f the Home Colony 1 9 7 3 t o 1 9 7 5 85 1 9 7 3 1 1 9 7 4 2 1 9 7 5 2 A d u l t males 3 3 4 4 Y e a r l i n g males 2 4 4 9 A d u l t females 1 l l 5 10 Y e a r l i n g females 6 4 12 A d u l t o r y e a r l i n g females 5 T o t a l a d u l t s and y e a r l i n g s 17 23 35 J u v e n i l e s weaned,.. 16 51 2E/ate June. oLate A p r i l and e a r l y May. ^ I n c l u d e s one male t h a t d i e d d u r i n g h a n d l i n g i n e a r l y J u l y . I n c l u d e s one y e a r l i n g removed i n August. As w e l l , two Immigrants ,-wece removed i n August. ^ I n c l u d e s one female removed i n e a r l y May. I n c l u d e s a l i t t e r of f i v e whose mother d i e d at or b e f o r e weaning. None s u r v i v e d . measure o f r a t e o f i n c r e a s e . Prom 1 9 7 3 t o 1 9 7 5 the number o f a d u l t and y e a r l i n g females i n c r e a s e d at a r a t e , r , of . 3 0 3 (Table X X V I I I ) . . I f numbers are a d j u s t e d f o r m o r t a l i t y and i m m i g r a t i o n i n the s p r i n g o f 1 9 7 3 and the a d u l t female's removal i n 197-4, t h e n r becomes . 2 8 8 (Table X X V I I I ) . Between 1 9 7 3 and 1974 numbers appeared t o change l i t t l e ( T a b l e s XXVII and X X V I I I ) . From 1974 t o 1 9 7 5 they i n c r e a s e d markedly due t o the i n c r e a s e i n the y e a r l i n g seg-ment of the p o p u l a t i o n (Table X X V I I ) . T h i s r e f l e c t s the g r e a t e r p r o d u c t i v i t y of 1974 compared to 1 9 7 3 - I f m o r t a l i t y p a t t e r n s remained unchanged, t h i s i n c r e a s e l i k e l y would have c o n t i n u e d t o 1976 as p r o d u c t i o n was a g a i n h i g h i n 1 9 7 5 -The c a l c u l a t e d r a t e s o f i n c r e a s e a r e based on an un-s t a b l e age d i s t r i b u t i o n and o b s e r v a t i o n s from o n l y one c o l -ony. A r a t e o f i n c r e a s e r ., based on o b s e r v a t i o n s over s t h r e e y e a r s , i n c o r p o r a t i n g o b s e r v a t i o n s from s e v e r a l c o l o n -i e s , and assuming a s t a b l e age d i s t r i b u t i o n can be c a l c u -l a t e d from observed a g e - s p e c i f i c s u r v i v a l r a t e s , age-s p e c i f i c f e c u n d i t y , and sex r a t i o s . T h i s r a t e o f i n c r e a s e i s u s u a l l y approximated by InR o r ~ r S C C where Re = E l 111 o X X (Table X X I X ) , the net r e p r o d u c t i v e r a t e or the average number of o f f s p r i n g produced by an i n d i v i d u a l , and Table XXVIII. Rate of increase, r , of the Home Colony based on numbers of adult and y e a r l i n g females r based on r based on observed numbers adjusted numbers 1973 to 1974 1974 to 1975 1973 to 1975 .223 .383 .303 . I 6 l x 1.4l4 2 .288 1' 2 1973 numbers increased to (12/.905)-. 5 = 12. 77 where 12=observed number i n lat e June, .905=survival A p r i l 30 to June 22(mean capture date), and .5=mean number of female immigrants to Home' 2Colony, 1974 and 1975. 1975 numbers increased to 22+.70=22.70 where 22=observed number and .70=probability of s u r v i v a l of adult female removed i n May, 1974. 88 m x l m T x x c R o the c o h o r t g e n e r a t i o n time (Caughley and B i r c h 1 9 7 1 , May 1 9 7 6 ) . T h i s a p p r o x i m a t i o n i s v a l i d o n l y i f R ~ 1 or i f the c o e f f i c i e n t o f v a r i a t i o n (CV) o f T c i s s m a l l (May 1 9 7 6 ) . For these marmot p o p u l a t i o n s , n e i t h e r c o n d i t i o n i s met. R Q i s 2.684 (Table X X I X ) . The c o e f f i c i e n t o f v a r i a t i o n CV = - 2 . T c depends on the v a r i a n c e o f the 1 m d i s t r i b u t i o n , X X 0 x 1 m „ o2 = x x _ T 2 R o 2 7 3 5 ^ = 4 ' 3 4 1 = - 6 3 0 . The a p p r o x i m a t i o n r c u n d e r e s t i m a t e s r £ The r e l a t i v e e r r o r I n e s t i m a t i n g r by r i s s c 2 r - r • I n R CV , , n „ c N  s c ~ o (May 1 9 7 6 ) . r 2 c I n t h i s c a s e , VQ - . 2 2 7 ; the e r r o r i n u s i n g t h i s as an e s t -imate o f r would be 1 9 . 6 % and r s h o u l d be c l o s e t o . 2 7 2 . s s The e x a c t r a t e o f i n c r e a s e , r , i s the r o o t o f the e q u a t i o n Z e " r x l m = 1 . x x I f . 2 7 2 i s s u b s t i t u t e d i n t o the e q u a t i o n , S e ~ r x l m = 1 . 0 0 0 7 -x x 89 Table XXIX. S u r v i v o r s h i p t a b l e d ) and f e c u n d i t y table(m ) f o r Watch Lake marmot populations x x 1 m 1 m x x x x 0 1.000 0. 000 0. 000 1 0.406 0.193 0.078 2 0.297 2. 240 0.665 3 0. 207 2.850 0.590 4 0.144 2. 850 0. 410 5 • 0.100 ' 2.850 0.285 6 0. 070 2.850 0.199 7 0. 049 2.850 0.140 8 0. 034 2.850 0.097 9 0. 024 2.850 0. 068 10 0.016 2.850 0. 046 11 0. 011 2. 850 0.031 12 0.008 2.850 0.023 13 0. 006 2.850 0.017 1.4 0. 004 2.850 0. 011 15 0. 003 2.850 0.009 16 0. 002 2.850 0. 006 17 0. 001 2.850 0.003 18 0. 001 2.850 0.003 19 0. 001 2. 850 0.003 20 0. 000 2.850 0.000 r 1 m =2.684 x x ;Age i n June. P r o b a b i l i t y of reaching age x. C a l c u l a t e d from r a t e s t i l l June 30, .Tables 2 and 6 i n S u r v i v a l . 'Mean no. young/female produced at age x. % producing l i t t e r s : Table I I I ; l i t t e r s i z e s : yearlings-5.25, 2 year olds-6.167, 3 years and o l d e r -Table IV; frequency female o f f s p r i n g : .466 f o r a l l ages. 90 T h i s i s the best s o l u t i o n t o the n e a r e s t . 0 0 1 . The observed r a t e o f i n c r e a s e , r = . 2 9 , o f t h e Home Colony 1 9 7 3 t o 1 9 7 5 and t h e r a t e i m p l i e d by t h e l i f e and f e c u n d i t y t a b l e s f o r the Watch Lake p o p u l a t i o n s , r = . 2 7 , s b o t h i n d i c a t e the p o p u l a t i o n s are r a p i d l y e x panding. 91 SOCIAL ORGANIZATION A g o n i s t i c " I n t e r a c t i o n s and Scent M a r k i n g I s h a l l c o n s i d e r o n l y t h o s e o v e r t l y a g g r e s s i v e a c t s , c h a s i n g and f i g h t i n g , t h a t might be r e l a t e d t o t e r r i t o r i a l d e f e n s e . An a c t was not c o n s i d e r e d a chase i f t h e t h r e a t e n e d marmot i g n o r e d the r u s h o f the a t t a c k e r . U s u a l l y t h r e e c h a r a c t e r i s t i c s d i s t i n g u i s h e d f i g h t s from p l a y - f i g h t s . (For a d e s c r i p t i o n o f p l a y - f i g h t s , see Armitage 1 9 7 4 ) . F i g h t s were accompanied by l o u d v o c a l i z a t i o n s I r e f e r r e d t o as s n a r l i n g . These may be the sounds Waring ( 1 9 6 6 ) c a l l e d screams. F i g h t s u s u a l l y ended w i t h one marmot l e a v i n g the v i c i n i t y o f the f i g h t . Marmots p l a y - f i g h t i n g u s u a l l y r e - • mained i n c l o s e p r o x i m i t y b o t h b e f o r e and a f t e r p l a y i n g . I n a f i g h t , the c o n t e s t a n t s r a r e l y , i f e v e r , used a c h a r a c t e r -i s t i c p o s t u r e o f p l a y - f i g h t s , each s t a n d i n g on h i s h i n d l e g s and p u s h i n g w i t h h i s f o r e l e g s . The number o f chases and f i g h t s per hour was g r e a t e s t i n A p r i l and d e c l i n e d t h r o u g h o u t the a c t i v e season ( T a b l e XXX). The p a t t e r n i s s i m i l a r i n each y e a r w i t h two excep-t i o n s . The r a t e i n J u l y and p o s s i b l y August 1 9 7 3 i s h i g h r e l a t i v e t o 1974 and 1 9 7 5 - The June 1975 r a t e i s c o n s i d e r -a b l y g r e a t e r t h a n the p r e c e d i n g y e a r s . The f r e q u e n c y o f a g o n i s t i c i n t e r a c t i o n s s h o u l d depend on t h e number o f marmots i n the c o l o n y and, I f any age-sex c l a s s I s more prone to . chase o r be chased, on the age s t r u c t u r e as w e l l . The p a t -t e r n remains e s s e n t i a l l y the same when the r a t e I s m o d i f i e d by the number o f marmots i n t h e c o l o n y each month . ; ' 92 Table XXX. A p r i l Chases and fights/hour at the Home Colony, 1973 to 1976. Hours of observation i n parentheses. May June July August Weighted Mean " 1973 - - . . .• 1974 1.22(7.4)1.18(37.3) 1975 - 1.12(26.8) 1976 - 0.78 0.27(22.2) 0T00T 217 5"5 0T5 oTHTQ) 0.52(47.7) 0.21(19.3) 0.00(10.0) 0.00(8.5) 0.69(82.4) 0.90(21.2) 0.12(8.7) - 0.88(56.7) 0.-78(5.2) Unweighted mean Weighted mean 1.22 1.03 0.46 . 0.30 0.25 1.22(7.4)1.13(69.2) 0.46(62.7) 0.42(40.2) 0.16(12.5) 0.69(192) 93 (Table X X X I ) . June 1975 and J u l y - A u g u s t 1 9 7 3 appear h i g h . I n 1 9 7 3 the s o c i a l s t r u c t u r e may have been d i s r u p t e d by man-i p u l a t i o n s i n l a t e June and e a r l y J u l y . An a d u l t male and y e a r l i n g male were removed. A y e a r l i n g male was i n t r o d u c e d t o the c o l o n y . Some marmots were removed f o r a day; some were r e l e a s e d at burrows o t h e r than t h e i r c a p t u r e s i t e a f t e r t a g g i n g . However, t h e r e were no s i m i l a r d i s r u p t i o n s i n June 1 9 7 5 . The f i r s t q u e s t i o n I c o n s i d e r e d i n t r y i n g t o e x p l a i n the observed d e c l i n e i n a g o n i s t i c b e h a v i o u r from s p r i n g t o summer was "who i s i n v o l v e d i n the i n t e r a c t i o n s ? " The 1 9 7 3 and 1974 o b s e r v a t i o n s are o f l i t t l e use i n a d d r e s s i n g t h i s q u e s t i o n as the age and sex o f o n l y 22 t o 68% o f the i n d i -v i d u a l s were i d e n t i f i e d i n months w i t h more than two i n t e r -a c t i o n s . I n 1 9 7 5 , 88% o f the i n t e r a c t i n g marmots were i d e n -t i f i e d i n May and 95% i n June. E x p e c t e d numbers o f a g o n i s -t i c i n t e r a c t i o n s were c a l c u l a t e d from the average age s t r u c -t u r e each month (Table X X X I I ) . I n May 1975 a d u l t females were i n v o l v e d i n more chases and f i g h t s than e xpected (Table X X X I I I ) . The same t r e n d appeared i n May 1 9 7 6 . How-e v e r , the sample s i z e was i n a d e q u a t e t o a c h e i v e s i g n i f i c a n c e . The p a t t e r n was not e v i d e n t i n May 1974 where the i d e n t i t i e s o f 32% o f the i n d i v i d u a l s • w e r e unknown. I n June 1975 the age-sex c l a s s e s p a r t i c i p a t e d randomly i n chases and f i g h t s . The next q u e s t i o n t o :address i s "what r o l e s do the d i f f e r e n t age-sex c l a s s e s t a k e i n t h e c h a s e s ? " or "who chases whom?" D u r i n g May i n b oth 1974 and 1 9 7 5 a d u l t females 94 Table XXXI. Chases and fights/animal-hour at the Home Colony 1973 to 1975. Animal-hours i n parentheses. A p r i l May June J u l y August Weighted mean 1973 : - .014(422) .049(344).033(601 .030(8261 1974' .051(177) .051(857) .011(367) .00(190) .000(136) .033(1727) 1975 - .033(911) .031(614) .005(208) - .029(1733) Unweighted mean .051 .042 .019 .018. .017 Weighted mean .051(177) .042(1768).021(1403).024(742).010(196) .031(4286) Table XXXII. The average age-sex structure of the Home Colony-June 1973 to July 1975/ excluding j u v e n i l e s 1973 1974 1975 June July Aug. A p r i l May June July Aug. A p r i l May June July Adult -males 3 3 2 4 4 4 4 4 4 3 1 0 Adult females 1 1 1 11 10 9 8 7 10 10 10 8 Y e a r l i n g males 2 2 2 5 5 3 4 2 9 9 6 6 Yearling females 7 6 5 4 4 3 3 3 12 12 12 10 Females, age unknown 6 5 5 / T o t a l 19 16 15 24 23 19 19 16 35 34 29 24 Table XXXIII. The age-sex c l a s s e s Involved i n a g o n i s t i c i n t e r a c t i o n s d u r i n g May, 1974 to 1976, Home Colony. 1974 1975 1976 Observed Expected Observed Expected Observed Expected Adult males 4 10.43 ' 2 4:68 0 1.6 Adult females 27 26.08 25 15.59 8 6.4 Y e a r l i n g males Y e a r l i n g females Unknown y e a r l i n g s 11) ) ) . 4)29 23.48 ) ) 14) 7) ) ) 11)26 32.73 ) ) 8) O 1 0 0 I d e n t i t y Unknown 28 - 0 T o t a l 88 59.?9 60 53.00 8 8.0 x 2 5.299 8.601 P <.10 .02 .1682 •1 Y e a r l i n g - y e a r l i n g i n t e r a c t i o n s were not recorded. As the expected' values assume n e i t h e r y e a r l i n g - y e a r l i n g nor a d u l t - y e a r l i n g i n t e r -a c t i o n s are p o s s i b l e , the t e s t i s co n s e r v a t i v e . 1 8 Exact p r o b a b i l i t y based on bin o m i a l d i s t r i b u t i o n , .8 =.168. .97 i n i t i a t e d more th a n t h e i r share o f chases (Table XXXIV). (Note however t h e l a r g e number o f u n i d e n t i f i e d marmots i n 1 9 7 4 . The f o r e g o i n g c o n c l u s i o n i s ; i n v a l i d i f a d u l t f e males were u n d e r r e p r e s e n t e d i n the unknowns). The 1976 o b s e r v a -t i o n s a r e c o n s i s t e n t w i t h t h i s p a t t e r n as a d u l t females i n -i t i a t e d a l l f o u r chases observed. Comparisons between June o f d i f f e r e n t y e a r s were d i f f i c u l t . Not o n l y were sample s i z e s s m a l l e r , but I n 1975 a d u l t males were removed from the Home c o l o n y . I n 1 9 7 3 a d u l t males chased more t h a n e x p e c t e d (Table XXXIV). I n 1 9 7 4 , o n l y two marmots i n i t i a t i n g chases were i d e n t i f i e d . I n 1 9 7 5 , w i t h o n l y one a d u l t male p r e s e n t , t h e chases by o t h e r age-sex c l a s s e s d i d not d i f f e r from ex-p e c t e d . I f o b s e r v a t i o n s from a l l t h r e e y e a r s are combined, a d u l t s of bo t h sexes tend t o chase more th a n e x p e c t e d , y e a r -l i n g males chase l e s s (Table XXXV). D u r i n g J u l y and August c h a s i n g was r a r e except i n 1 9 7 3 - D u r i n g J u l y 1 9 7 3 a d u l t males chased -more th a n expected and non - b r e e d i n g females l e s s t h a n e x p e c t e d among i d e n t i f i e d marmots (Table XXXVI). How-ever the r e l i a b i l i t y o f t h i s t e s t depends s t r o n g l y on the c l a s s e s the u n i d e n t i f i e d r e p r e s e n t e d . I f non - b r e e d i n g females were much l e s s l i k e l y t o be i d e n t i f i e d t h a n a d u l t males, the t e s t i s u n r e l i a b l e . A y e a r l i n g ' s p r o b a b i l i t y o f b e i n g chased was g r e a t e r t h a n t h a t o f a d u l t s o f e i t h e r sex. D u r i n g May o f 1974 and 1975 y e a r l i n g s were chased more t h a n e x p e c t e d , a d u l t s l e s s (Table X X X V I I ) . D u r i n g June o f 1 9 7 5 y e a r l i n g s a g a i n r e c e i v e d more th a n t h e i r share o f chases (p = . 0 2 3 ) . I n June o f 1 9 7 3 Table XXXIV. The age-sex c l a s s e s I n i t i a t i n g chases during May and June, 1973 to 1976, at the Home Colony 1973 197-4 1975 1976 Observed Expected Observed Expected Observed Expected Observed Expected May Adult males 2 4.55 1 2.12 0 .80 Adult females 20 11.36 19 7.06 4 3.20 Y e a r l i n g males 2 4.55 .0 6.35 O 1 Y e a r l i n g females no data 1 4.55 4 8.47 O 1 Unknown y e a r l i n g s 1 0 O 1 Unknowns 13 1 0 T o t a l 39" "25-01 25 24.00 4 4.00 X 2 ' 12.189 29 .494 -P . .01 . 001 .410 2 June Adult males 5 .95 0 0 -3 . . . . Adult females 0) 2 8 5.36 0) 0 3.21 no data Y e a r l i n g males 0 Y e a r l i n g females o) 5 - 0 5 0 7 6.43 Unknowns 1) 2 : 0 T o t a l 6 6.00 4 l b 15.00 X 2 - - .569 P .000502 > .10 • Y e a r l i n g - y e a r l i n g i n t e r a c t i o n s were not recorded. The t e s t i s conservative as the expected values assume n e i t h e r y e a r l i n g - y e a r l i n g nor a d u l t - y e a r l i n g 2 i n t e r a c t i o n s c o u l d have occurred. ,exact p r o b a b i l i t y based on b i n o m i a l d i s t r i b u t i o n . Because the expected value 1/29 x 15=.52, i s l e s s than one, t h i s c l a s s was excluded from the t e s t . I f i n s t e a d a d u l t males and y e a r l i n g males are lumped, X = 5.269 and p < .10. Table XXXV. The age-sex classes i n i t i a t i n g chases during June 1973 to 1975 combined Observed chases Expected chases 1 Adult males 5 2.59 Adult females 10 7.44 Y e a r l i n g males 0 3.60 Y e a r l i n g females 7 8.37 Unknowns 3 -T o t a l 25 22.00 £=6.957 p<.10 ^Expected values are based on the average number i n each class weighted by the number of observation hours i n June of each year 100 Table XXXVI.The age-sex classes i n i t i a t i n g chases during J u l y , 1973 at the Home Colony Observed chases Expected chases Adult males 4 1.250 Breeding females 1 1.875 Y e a r l i n g males 2 1.250 Non-breeding females 3 5.625 Unknowns 6 T o t a l 16 10.000 X2=8.133 P<. 05 101 Table XXXVII. The age and sex o f marmots chased d u r i n g May 1974 t o 1976 a t the Home Colony 1974 1 9 7 5 1976 Observed E x p e c t e d Observed E x p e c t e d Observed Expected A d u l t males 1 4 . 52 0 2 . 03 0 . 8 0 A d u l t females 3 1 1 1 . 30 3 2 6 . 7 6 4 3 . 2 0 Y e a r l i n g males ) O3 Y e a r l i n g females "f 22 1 0 . 1 7 I f 20 14.21 0 3 Unknown y e a r l i n g s 12j 0 3 Unknowns 13 - 2 - 0 T o t a l 39 2 5 - 9 9 25 2 3 . 0 0 4 2 2 . 5 9 0 6 . 487 .410 4 p « • 005 < - 05 1Two o f the 3 chases were d i r e c t e d toward t h e o n l y non b r e e d i n g female. Only the s i n g l e non b r e e d i n g a d u l t female was chased. O b s e r v a t i o n s o f y e a r l i n g s c h a s i n g y e a r l i n g s were not r e c o r d e d . E x a c t p r o b a b i l i t y based on b i n o m i a l d i s t r i b u t i o n . 102 and. 1974 I r e c o g n i z e d o n l y f o u r marmots t h a t were chased. Three were y e a r l i n g f e m a l e s . D u r i n g J u l y 1 9 7 3 the p r o b a b i l -2 i t y o f b e i n g chased d i d not v a r y among c l a s s e s (X = 1 . 9 2 7 ) -To summarize, c h a s i n g and f i g h t i n g were most common i n A p r i l and May. T h e i r f r e q u e n c y d e c l i n e d t h r o u g h the sum-mer w i t h J u l y 1 9 7 3 and June 1975 b e i n g somewhat h i g h e r than o t h e r y e a r s . I n May a d u l t females d i d most o f the c h a s i n g . I n June, a d u l t s o f both sexes may have chased more than y e a r l i n g s . D u r i n g both t h e s e months y e a r l i n g s were chased more th a n e i t h e r a d u l t c l a s s . I n J u l y 1 9 7 3 a d u l t males ap-peared t o chase more th a n y e a r l i n g males and y e a r l i n g and a d u l t f e m a l e s . A d u l t females I n i t i a t e d most o f the chases d u r i n g the p e r i o d when the a g o n i s t i c b e h a v i o u r was a t i t s peak. T h i s p e r i o d a l s o c o i n c i d e s w i t h the time o f pregnancy and l a c t a -t i o n . The d e c l i n e i n a g g r e s s i v e b e h a v i o u r from s p r i n g t o summer may r e s u l t from changes i n the r e p r o d u c t i v e s t a t e o f the a d u l t f e m a l e s . One would expect c h a s i n g t o be most f r e -quent when d e n s i t i e s o f both b r e e d i n g females and y e a r l i n g s were h i g h e s t . I n 1975 the r a t e o f a g o n i s t i c i n t e r a c t i o n s d e c l i n e d l i t t l e from May t o June. I n t h a t y e a r , y e a r l i n g numbers were t r i p l e t h a t o f 1974 (Table X X X I I ) , w h i l e the number o f b r e e d i n g females remained the same at 9- Y e a r l i n g s were i n t e r m e d i a t e i n number i n 1 9 7 3 when t h e r e were but 3 b r e e d i n g f e m a l e s . The p e r s i s t e n c e o f a g o n i s t i c b e h a v i o u r i n 1975 may r e f l e c t the h i g h d e n s i t i e s of both b r e e d i n g females and y e a r l i n g s t h a t y e a r . 103 Marmots scent mark by r u b b i n g t h e i r cheeks a g a i n s t wood, r o c k , o r o c c a s i o n a l l y t h e ground, presumably d e p o s i t i n g s e c r e t i o n s from t h e i r f a c e g l a n d s (Gray 1 9 6 7 , Rausch and Rausch 1 9 7 1 , Barash 1 9 7 3 , Armitage 1 9 7 6 , Heard 1 9 7 7 ) . Scent marking was r e c o r d e d d u r i n g scan samples (Altmann 1 9 7 4 ) of the Home Colony i n 1 9 7 5 . The observed r a t e s h o u l d under-e s t i m a t e the a c t u a l r a t e ( u n l i k e c h a s i n g and f i g h t i n g o f which l i k e l y a l l o c c u r r e n c e s were r e c o r d e d ) . T h i s r a t e v a r -i e d l i t t l e from May t o J u l y ( T a ble X X X V I I I ) . A d u l t s and y e a r l i n g s of both sexes scent marked. However a d u l t males marked more than e x p e c t e d , females of a l l ages marked l e s s (Table XXXIX) . S p a c i n g I w i l l examine the use o f space by each age-sex c l a s s , n o t i n g i n p a r t i c u l a r any e v i d e n c e o f t e r r i t o r i a l i t y . Brown and O r i a n s ( 1 9 7 0 ) suggest t h r e e e s s e n t i a l c h a r a c t e r i s t i c s o f a t e r r i t o r y . I t i s a f i x e d a r e a ; i t i s e x c l u s i v e w i t h r e s -p ect t o r i v a l s ; and i t i s m a i n t a i n e d t h r o u g h a c t s o f d e f e n s e . Defense may i n v o l v e a c t u a l a g g r e s s i o n such as c h a s i n g and f i g h t i n g or a d v e r t i s e m e n t i n c l u d i n g d i s p l a y s and scent mark-i n g . D u r i n g o b s e r v a t i o n s , an i n d i v i d u a l s ' s l o c a t i o n was r e c o r d e d as the burrow t o which i t was c l o s e s t . I f the marmot was seen a t the same burrow s e v e r a l times i n a s i n g l e day, i t s presence was r e c o r d e d t h e r e o n l y once. A d u l t males. I n 1975 I observed a d u l t males from Table XXXVIII. Rates o f scent marking at the Home Colony i n 1 9 7 5 from scan samples 104 Number/hour Number/animal-hour May .224 . 0 0 7 June .331 .011 J u l y .230 .010 Table XXXIX. Comparison o f f r e q u e n c y o f scent m a r k i n by each age-sex c l a s s Observed E x p e c t e d A d u l t males 6 1 . 5 5 A d u l t females 3 5 - 6 9 Y e a r l i n g males 4 3 - 7 4 Y e a r l i n g females 3 5 - 0 1 T o t a l 16 1 5 - 9 9 X 2 = l 4 . 8 8 2 p - « t ' . 0 1 106 l a t e A p r i l t o m i d - J u l y . At the Old Colony seven a d u l t males were marked. At the Home Colony t h r e e o f f o u r males were marked o f which two were removed i n mid-May and the t h i r d i n e a r l y June. I n 1976 I observed t h r e e a d u l t males at the Home Colony i n e a r l y May. Each a d u l t male tended t o c e n t r e h i s a c t i v i t y around one burrow, h i s "home burrow", from at l e a s t mid-May to e a r l y o r m i d - J u l y (Table X L ) . I t i s u n c l e a r whether move-ments were g e n e r a l l y l i m i t e d t o t h i s same a r e a b e f o r e mid-May. Only 6 males were observed i n both l a t e A p r i l or e a r l y May and i n mid-May. Three c o n t i n u e d t o use the same burrow. Two, A and 1 6 , moved t o d i f f e r e n t burrows i n mid- and l a t e -May. One two ye a r o l d a t the Home Co l o n y , P, had not' l o c a l -i z e d h i s movements from h i s c a p t u r e A p r i l 25 by h i s removal May 1 2 . The Old Colony males tended t o remain at t h e same burrow more t h a n those a t the Home Colony. T h i s may r e f l e c t the l o w e r r a t i o o f burrows per male. There were 4 . 4 3 b u r r o w s / a d u l t male a t the Old Colony, 6 . 7 5 burrows/male a t the Home Colony i n 1 9 7 5 and 9 . 0 i n 1 9 7 6 . At no time d i d two a d u l t males share a burrow. At the Home Colony i n 1976 the home ranges of t h e a d u l t males d i d not o v e r l a p . I n 1975 the home ranges o f t h e two marked males, aged at l e a s t t h r e e and f o u r y e a r s , did not o v e r l a p . The home range o f the wandering two year o l d , P, o v e r l a p p e d p a r t s o f bo t h o f the o t h e r s . At t h e Old Colony, 105 s i g h t i n g s were made o f the 7 a d u l t males. On 8 o c c a s i o n s a male was seen near the home burrow o f a n o t h e r a d u l t male. 107 Table XL-. Frequency of s i g h t i n g s of t h e i r home burrows adu l t males at Colony-year Adult male Number of. s i g h t i n g s P r o p o r t i o n at home burrows O l d - 1 9 7 5 1 x. 24 . 7 0 8 1 6 9 4 . 3 3 3 3 5 24 . 7 9 1 5 0 1 0 . 7 0 0 5 4 2 0 . 7 0 0 5 5 1 9 . 8 9 5 7 1 3 C 3 3 3 ) 5 Mean . 6 8 8 Home - 1 9 7 5 2 A 7 . 5 7 1 K 8 . 5 0 0 6 P 8 . 2 5 0 Home - 1 9 7 6 3 7 0 5 . 6 0 0 7 4 4 . 7 5 0 7 9 2 1 . 0 0 0 Mean . 6 1 2 2~May 1 to August 5 . o A p r i l 1 8 to June 6 . JMay 2 to 7 . This male was observed e q u a l l y at two burrows, each r e p r e s e n t i n g ^ o n e - t h i r d of the t o t a l s i g h t i n g s . This male's home burrow was not v i s i b l e from the o b s e r v a t i o n p o i n t gThe f i g u r e was excluded from c a l c u l a t i o n of the mean. These are the s i g h t i n g s before the removal of A and P. 108 However, 4 o f t h e s e s i g h t i n g s o c c u r r e d e i t h e r b e f o r e the o t h e r a d u l t was f i r s t seen a t t h a t burrow o r a f t e r he was no l o n g e r seen i n the c o l o n y . Of the 4 r e m a i n i n g t i m e s a male o c c u r r e d a t a n o t h e r ' s home burrow, 2 were c a p t u r e s . I observed two t r e s p a s s e r s . Once a male, X, approached the burrow o f h i s c l o s e s t n e i g h b o u r , 3 5 , w i t h apparent h e s i t a -t i o n . The r e s i d e n t , 3 5 , was not:'.in s i g h t . X r a n a few st e p s toward 35's burrow, t h e n stopped, r a n , and stopped s e v e r a l t i m e s . Another t i m e 35 appeared a t X's burrow. He put h i s head i n , r a p i d l y p u l l e d i t o u t , and r a n t o h i s own burrow. The e x c l u s i v e n e s s of an a d u l t male's home range w i t h r e s p e c t t o o t h e r a d u l t males d i d not extend t o a l l o t h e r age-sex c l a s s e s . Y e a r l i n g females were c o n s i s t e n t l y t o l e r -a t e d a t the core o f t h e i r home ra n g e , the home burrow. A d u l t females were o c c a s i o n a l l y seen w i t h a d u l t males at t h e i r home burrows. Y e a r l i n g males were r a r e l y seen e i t h e r near an a d u l t male o r a t the home burrow o f an a d u l t male when i t s owner was absent. I n 1975 a t the Home Colony o n l y once d i d I see an a d u l t male and y e a r l i n g male at the same burrow system. At the Old Colony one immigrant y e a r l i n g f r e q u e n t l y used t h e burrow o f an a d u l t male. However, o n l y once was he near the a d u l t . At the same c o l o n y f i v e y e a r l i n g males o c c u p i e d the a r e a around an unused b a r n , burrow B, from June 2 t o 5• One June 6 an a d u l t male was c a p t u r e d t h e r e and c o n t i n u o u s l y o c c u p i e d the burrow t h e r e a f t e r . 109 Prom t h a t same date u n t i l o b s e r v a t i o n s ended, a y e a r l i n g male was seen t h e r e o n l y t w i c e . A c t s o f o v e r t defense o f a d u l t males' home ranges were almost t o t a l l y l a c k i n g . I never saw a d u l t males i n t e r -a c t i n g among th e m s e l v e s . Only o c c a s i o n a l l y d i d they i n t e r -a c t w i t h y e a r l i n g )-males. An a d u l t male, K, t w i c e i n t e r a c t e d w i t h a y e a r l i n g male, Q, on-the p e r i p h e r y o f K's home range. The f i r s t time he chased Q f o r 100 m. The second time Q was In a l i v e t r a p . K c i r c l e d and c l i m b e d over t h e t r a p , t a i l -f l a g g i n g (see b e l o w ) . He c o n t i n u e d t h i s b e h a v i o u r f o r about f i v e m i n u t e s , e v e n t u a l l y k n o c k i n g over the l a r g e t r a p . K was k i l l e d f o u r days l a t e r . From t h a t day on, Q, who had never been seen at e i t h e r o f K's most f r e q u e n t l y used bur-orws, moved i n t o a l l o f K's burrows. While a g g r e s s i o n may have been r a r e , a d v e r t i s e m e n t , both v i s u a l and c h e m i c a l , was l e s s so. When a d u l t males walk they o f t e n c o n s p i c u o u s l y s w i r l o r " f l a g " (Armitage 1 9 6 2 , 1 9 7 4 ) t h e i r t a i l . T h i s b e h a v i o u r o f t e n caused even t h o s e i n d i v i d u a l s t o l e r a t e d by the a d u l t male t o move away. As w e l l , a d u l t males scent marked more t h a n any o t h e r age-sex c l a s s ( p r e v i o u s s e c t i o n ) . The o b s e r v a t i o n s suggest a d u l t males are t e r r i t o r i a l t o o t h e r a d u l t males and l i k e l y t o y e a r l i n g males. The a d u l t males occupy f i x e d a r e a s t h a t do not o v e r l a p t h o s e o f o t h e r a d u l t , males and r a r e l y t h o s e o f y e a r l i n g males. They a d v e r t i s e t h e i r p r escence v i s u a l l y and w i t h scent marks. A l t h o u g h o v e r t defense may be a n e c e s s a r y c o n d i t i o n f o r 110 t e r r i t o r i a l i t y , i t s absence i s not s u f f i c i e n t f o r non-t e r r i t o r i a l i t y . The i n t e n s i t y o f t e r r i t o r i a l d efense may be such t h a t r a r e a c t s a r e e f f e c t i v e i n m a i n t a i n i n g b o u n d a r i e s . A l t e r n a t i v e l y , t e r r i t o r i e s may be e s t a b l i s h e d d u r i n g A p r i l b e f o r e o b s e r v a t i o n s began. I f the a d u l t males a re t e r r i t o r i a l , t h e i r t e r r i t o r i e s appear t o conform most c l o s e l y t o Type A ( W i l s o n 1975) o r a l l - p u r p o s e (Brown and O r i a n s 1970) t e r r i t o r i e s i n which the t e r r i t o r y and home range are t h e same. An i n d i c a t i o n of the maximum s i z e o f the t e r r i t o r i e s can be c a l c u l a t e d by d i v i d -i n g t h e c o l o n y a r e a by the number o f a d u l t males. I n 1975 at the Old Colony the e s t i m a t e d mean t e r r i t o r y s i z e i s .76 ha. At the Home Colony i t i s .95 ha. However t h e s e f i g u r e s w i l l o v e r e s t i m a t e t e r r i t o r y s i z e i f the t e r r i t o r i e s are not c o n t i g u o u s . B e f o r e d i s p e r s a l y e a r l i n g males may w e l l o c-cupy gaps between a d u l t male t e r r i t o r i e s . What i s the a d a p t i v e v a l u e o f t e r r i t o r i a l b e h a v i o u r i n a d u l t males? I f t e r r i t o r i a l i t y has the e f f e c t o f e x c l u d -i n g y e a r l i n g males from a l l o r p a r t o f t h e c o l o n y , i t s h o u l d reduce c o m p e t i t i o n f o r b r e e d i n g females t h e f o l l o w i n g y e a r and t h e r e b y enhance t h e r e p r o d u c t i v e success o f th o s e males h o l d i n g t e r r i t o r i e s . A d u l t f e m a l e s . D i s c u s s i o n of a d u l t females i s l i m i t e d to t he Home Colony as I removed females from the O ld Colony . B r e e d i n g females d i s p l a y e d as much or more s i t e t e n a c i t y as a d u l t males (Table X L I ) . D u r i n g t h e e n t i r e a c t i v e season, I saw each b r e e d i n g female at a mean o f o n l y 3-1 ± -^ 8 burrows-. / Table XLI. Frequency of s i g h t i n g s of a d u l t females at t h e i r home burrows. Home Colony, A p r i l 18 to August 1,1975 Adult female Number of s i g h t i n g s P r o p o r t i o n at home burrows B 28 .857 C 10 1.000 D 22 .727 E 10 .800 G 25 .720 L 31 .742 0 23 .957 T 15 .600 1 17 11 \i .545 2 • Mean .793 T d i d not breed. This f i g u r e was excluded from c a l c u l a t i o n of ,the mean.' The f i r s t 4 s i g h t i n g s were at the burrow system occupied by Adult Female C. About May 27, 17 moved to another burrow where she remained u n t i l her removal i n J u l y . 112 I n 1974 and 1 9 7 5 , 18 females had l i t t e r s . A l l used s e p a r a t e burrows except one p a i r , G and L, who shared the same burrow system i n both y e a r s . However they each c o n s i s t e n t l y used d i f f e r e n t e n t r a n c e s 6 . 4 meters a p a r t and d i d not v e n t u r e w i t h i n 3 meters o f the o t h e r ' s e n t r a n c e . Another p a i r t e m p o r a r i l y o c c u p i e d t h e same burrow system under a bar n . I n May 1 9 7 5 A d u l t Female 17 appeared at the barn and fought w i t h the r e s i d e n t o f t h a t burrow. 17 remained t h e r e 17 t o 19 days, moving t o a n o t h e r burrow 19 t o 21 days b e f o r e her l i t t e r emerged. B r e e d i n g females would defend t h e i r burrows a g a i n s t o t h e r a d u l t f e m a l e s . I n 1 9 7 5 I observed o n l y one o t h e r I n -sta n c e o f an a d u l t female by a n o t h e r ' s home burrow. When I f i r s t saw D a t L's burrow, they were f i g h t i n g . D t h e n l a y on her back w i t h f e e t and head up, t a i l on her b e l l y . L walked around, t a i l - f l a g g i n g , t h e n e n t e r e d her burrow. She reemerged and b i t at D who responded by s n a r l i n g (a v o c a l -i z a t i o n g i v e n o n l y by a s u b o r d i n a t e t o a dominant or heard i n f i g h t s ) . D e v e n t u a l l y got up. A g a i n they w r e s t l e d . When D l e f t , L f o l l o w e d her about 10 meters, t h e n t r o t t e d back t o her burrow e n t r a n c e . I n e a r l y May 1976 a d u l t f e males 4 t i m e s chased o t h e r a d u l t females from t h e i r burrows. On one o c -c a s i o n A d u l t Female W v e n t u r e d too c l o s e t o Burrow 2 . I t s r e s i d e n t f e m a l e , L, chased W back t o her home burrow, 5 , where upon W t u r n e d and chased L p a r t way back t o Burrow 2 . I n 1 9 7 3 a female w i t h a l i t t e r d i s p l a c e d an untagged a d u l t from i t s burrow. When female B and her l i t t e r moved i n t o 113 Burrow 6 , the r e s i d e n t t e m p o r a r i l y used a s e p a r a t e e n t r a n c e . A f t e r two f i g h t s w i t h B she v a c a t e d the burrow. A d u l t females were u s u a l l y i n t o l e r a n t o f o t h e r age-sex c l a s s e s as w e l l . D u r i n g 1974 t o 1 9 7 6 , a b r e e d i n g female shared a burrow w i t h an a d u l t male at most f o u r t i m e s . I n at l e a s t two c a s e s , the male and f e m a l e , l i k e females G and L, used s e p a r a t e e n t r a n c e s , a v o i d i n g the e n t r a n c e o f the o t h e r . A d u l t females, o c c a s i o n a l l y b i t or r u s h e d a t a d u l t males, but t h e males n e i t h e r fought nor r a n from them. I n 1 9 7 5 the o n l y female t o share her burrow w i t h a y e a r l i n g d i d so w i t h her two d a u g h t e r s . However y e a r l i n g s f r e q u e n t l y ap-proached the burrows of a d u l t females and were r e p e a t e d l y chased away. B r e e d i n g females s a t i s f y t h e c o n d i t i o n s o f t e r r i t o r i -a l i t y . They occupy a s i n g l e burrow system from which they a c t i v e l y e x c l u d e o t h e r s by c h a s i n g o r f i g h t i n g . W ith t h e e x c e p t i o n o f the a d u l t female and her y e a r l i n g d a u g h t e r s , they t o l e r a t e d no o t h e r y e a r l i n g s o r a d u l t s o f e i t h e r sex near p a r t or a l l o f a burrow system. To h e l p determine the s i z e o f t h e i r t e r r i t o r i e s , I marked c i r c l e s o f l i m e around the burrows w i t h a r a d i u s o f 3 meters. The females chased a l l t h a t touched or c r o s s e d the l i n e . The t e r r i t o r i e s must have d i a m e t e r s o f at l e a s t 6 meters. T h e i r a c t u a l d i a m e t e r s are l i k e l y not more t h a n 2 or 3 t i m e s t h a t . B r e e d i n g females e x h i b i t e d t e r r i t o r i a l b e h a v i o u r from t h e f i r s t o b s e r v a t i o n s i n . e a r l y May b u t , u n l i k e a d u l t males, the females stopped d e f e n d i n g t h e i r t e r r i t o r i e s i n June. I n 114 1975 the l i t t e r s emerged between June 8 and 2 0 . An a d u l t female i n i t i a t e d chase o n l y once a f t e r June 1 2 . On June 1 7 , L a l l o w e d G t o s i t b e s i d e her and her burrow e n t r a n c e . Three days l a t e r when D v i s i t e d , L d i d not a l l o w her the same, freedom. T e r r i t o r i a l d e f e nse appears t o break down g r a d u a l l y a f t e r the l i t t e r s emerge. Females e x h i b i t q u i t e a d i f f e r e n t t ype o f t e r r i t o r y . i t o r i a l i t y from a d u l t males. T h e i r t e r r i t o r i e s a r e more e x c l u s i v e , s m a l l e r , and more r e s t r i c t e d i n t i m e . They con-form most c l o s e l y t o a Type C t e r r i t o r y ( W i l s o n 1 9 7 5 ) , a s m a l l defended a r e a around a n e s t . Type C t e r r i t o r i e s a re more t y p i c a l o f b i r d s t h a n mammals. T h e i r a d a p t i v e v a l u e t o female marmots l i k e l y l i e s i n p r o t e c t i n g t h e i r o f f s p r i n g b e f o r e weaning. A d u l t s and y e a r l i n g s o f s e v e r a l s p e c i e s o f ground s q u i r r e l s w i l l k i l l j u v e n i l e s (Quanstrom 1 9 7 1 , ., S t e i n e r 1 9 7 2 , Sherman 1 9 7 6 ) . A d u l t females d i s p l a y e d some degree of t e r r i t o r i a l f i d e l i t y between y e a r s . Of e i g h t females b r e e d i n g more t h a n once, 6 or 7 used the same t e r r i t o r y i n at l e a s t two y e a r s (Table X L I I ) ; 4 used the same t e r r i t o r y i n a l l . y e a r s i n which they c o n s e c u t i v e l y b r e d . Of 12 o b s e r v a t i o n s of a female i n two c o n s e c u t i v e y e a r s , 7 t i m e s she r e t a i n e d t h e same t e r -r i t o r y and 5 t i m e s she a c q u i r e d a new one. When females changed t e r r i t o r i e s between y e a r s , t h e i r p r e v i o u s t e r r i t o r -i e s t w i c e remained v a c a n t . Thus a c q u i s i t i o n o f a new t e r -r i t o r y does not n e c e s s a r i l y i m p l y e x p u l s i o n from the o l d one. Nonbreeding a d u l t females d i d not appear t o be 115 Table • X L I I . T e r r i t o r i a l f i d e l i t y o f a d u l t females between y e a r s A d u l t female 1 9 7 3 1974 1975 1976 C 1 6 1 16 16 -UT 9 o r l 3 •> 3 ? 9 21 10 B 9 o r l 3 •+ 6 2 _3 11 11 G - 5 5 -L - , 5 5 2 ,17' - 13 20 -D - 11 9 9 E - - 1 1 pBurrow i d e n t i f i c a t i o n number One o f UT and B used Burrow 9 , the o t h e r Burrow 1 3 , b e f o r e UT -moved her l i t t e r t o Burrow 1 and B moved hers t o Burrow 6 . J B d i d not b r e ed i n 1 9 7 4 . I l 6 t e r r i t o r i a l . Only one a d u l t d i d not breed i n 1 9 7 5 . She shared her home burrow w i t h f o u r y e a r l i n g f e m a l e s . As w e l l , she t o l e r a t e d the v i s i t s o f two a d u l t males. Y e a r l i n g s . I found no evi d e n c e o f t e r r i t o r i a l i t y i n y e a r l i n g s . At the Home Colony y e a r l i n g s d i d not c e n t r e t h e i r a c t i v i t y around one burrow t o t h e e x t e n t a d u l t s d i d (Table X L I I I ) . However female y e a r l i n g s g r a d u a l l y i n c r e a s e d the time they spent at a p a r t i c u l a r burrow. By J u l y t h e i r move-ments were as l o c a l i z e d as a d u l t f e m a l e s ' . Male y e a r l i n g s d i d not change t h e i r use o f space w i t h t i m e . P o s s i b l y I t ' was d i s r u p t e d by the removal o f the a d u l t males. I f so, the Old Colony s h o u l d p r o v i d e more r e l i a b l e o b s e r v a t i o n s o f y e a r -l i n g male movements. However the p a t t e r n was the same t h e r e (Table X L I V ) . Male y e a r l i n g s c o n t i n u e d t o spend l i t t l e time at one burrow i n "June and p o s s i b l y J u l y . Combining males from b o t h c o l o n i e s the mean p r o p o r t i o n o f s i g h t i n g s a t t h e i r most f r e q u e n t l y used burrow was . 4 6 i n May, . 4 3 i n June, and . 4 4 i n J u l y . These are c o n s i d e r a b l y l o w e r t h a n means o f a d u l t males and females f o r the e n t i r e p e r i o d and s i g n i f i -c a n t l y lower t h a n y e a r l i n g females i n J u l y (t.,=- 5 . - 2 5 8 , . p < . 0 1 ) . A g a i n u n l i k e a d u l t s , y e a r l i n g s d i d not have e x c l u s i v e use of t h e i r home burrows. Most shared t h e i r burrow w i t h o t h e r y e a r l i n g s , o f t e n s i b l i n g s . Of 17 Home Colony year-, l i n g s who had s i b l i n g s and whose movements were known, 4 shared the burrow w i t h one s i b l i n g w h i l e a n o t h e r 3 s i b l i n g s shared one burrow. An e i g h t h y e a r l i n g l i v e d i n a burrow Table X L I I I . Yearlings' use of burrows at the Home Colony, 1975 May June J u l y Number Number Proportion Number Number Proportion Number Number Prop. of of at of of at of of at Sex I d e n t i t y sightings burrows home burrow sightings •burrows. home burrow sightings burr. home . Females M 14 4 .43 13 6 .38 5 2 .80 N 14 4 .43 11 6 .55 - - -W 14 5 .•50,"- 13 3 .62 1 - -Z 21 9 • 33 20 9 .30 5 2 .80 7 19 10 .21 21 10 .29 7 2 .86 . • 8 12 5 .42 2 2 - 2 1 -9 15 10 . 20 10 5 .60 1 - -10 7 5 .43 8 5 .38 1 -• -18 12 6 • 33 6 4 .50 2 2 -24 10 7 .20 11 3 .73 1 -31 6 3 .67 12 3 .58 3 1 1.00 . 43 13 6 • 31 19 4 • 58 i - -Mean 13.1 6.2 12. d 4.U 1.7 • . 8t55' Males RYG . 12 1 — — — — - — I 7 .43 - - - - - -Q 15 5 .47 13 5 .38 11 5 .45 4 14 7 .29 13 3 .38 5 4 .40 21 6 6 ' .17 13 5 .69 3 3 .33 44 4 ' 2 • 75 - - - - -70 - - - 4 4 .25 - - -74 - - 1 - - 1 - -79 - - - - - - 2 1 -Mean 9-7 5.2 • 393 10.7 1 4.2 .425 5.21 3.2 .393 Single s i g h t i n g s excluded from the mean Table XLIV. Male y e a r l i n g s ' use of burrows at the Old Colony, 1975 May June J u l y I d e n t i t y Number of s i g h t i n g s Number of burrows Prop.at home burrows Number of s i g h t i n g s Number of burrows Prop.at home burrows Number of s i g h t i n g s Number of burrows Prop.at home burrows O v e r a l l Prop.at home burrows 11 7 4 • 43 6 3 • 50 _ .38 27 4 1 1. oo . ••" 5 2 .60 - — _ .67 33 3 2 .67 - - - - — .67 42 5 4 .40 17 6 .41 - - — .41 44 2 2 - 23 4 .48 3 3 .33 .43 45 2 2 - 2 1 - - - — .50 46 2 1 - 6 3 • 33 - - - .25 51 1 - - 7 .4 .43 - - - • 50 59 1 - - 21 8 .24 3 2 .67 .20 72 • — - - 9 6 .44 - - - .44 Mean 3.61 2.3 .625 10.7 4.1 .429 3.0 2.5 .50 .445 Mean excludes s i n g l e s i g h t i n g s M co 119 a d j a c e n t t h a t o f two s i s t e r s . T e r r i t o r y A c q u i s i t i o n and E f f e c t s o f K i n s h i p I l o o k e d a t the movements o f t h o s e marmots who were born i n the Home Colony and who s u r v i v e d t o a c q u i r e a t e r -r i t o r y t h e r e . Two females born i n 1 9 7 3 s u r v i v e d t o breed i n 1 9 7 5 . E i g h t females and two males o f the 1974 c o h o r t were a l i v e i n 1 9 7 6 . One of t h e s e females d i d not occupy a f i x e d a r e a i n e a r l y May; I e x c l u d e d her from the a n a l y s i s . Over h a l f o f the females o c c u p i e d t h e i r b r e e d i n g t e r -r i t o r y as a j u v e n i l e w i t h t h e i r mother (Table XLV). A l l but one female had used I t as a home burrow by June as y e a r l i n g s . By c o n t r a s t , t h e two males were never seen on t h e i r t e r r i -t o r i e s u n t i l J u l y as a y e a r l i n g i n one case and May as a two year o l d i n the o t h e r . A t h i r d male t e r r i t o r y h o l d e r i n 1976 had immigrated as a y e a r l i n g . He t o o was never seen on h i s t e r r i t o r y , o c c u p i e d by an a d u l t male i n 1 9 7 5 , u n t i l May as a two ye a r o l d . Of the n i n e females born i n the Home Colony t h a t a c -q u i r e d t e r r i t o r i e s t h e r e , two o c c u p i e d t h e i r t e r r i t o r y - t o -be c o n t i n u o u s l y from b i r t h , f o u r used t h e i r t e r r i t o r y con-t i n u o u s l y from May or June as y e a r l i n g s , and t h r e e d i d not c o n t i n u o u s l y occupy t h e i r t e r r i t o r y u n t i l t h e i r t h i r d y e a r (Table X L V I ) . The two t h a t remained i n t h e i r n a t a l burrow u n t i l m a t u r i t y were s i s t e r s t h a t l i v e d w i t h t h e i r mother. She was removed i n J u l y of t h e i r y e a r l i n g summer. A t h i r d s i s t e r o c c u p i e d p a r t o f the same t e r r i t o r y from June as a y e a r l i n g . Another two s i s t e r s t h a t o c c u p i e d t h e i r 120 Table XLV. The f i r s t time marmots used t h e i r t e r r i t o r i e s as t h e i r home burrows Juvenile Age Yearling Two year T o t a l old June July August A p r i l May June July May Females 5 0 0 0 2 1 0 1 9 Males 0 0 .0 0 0 0 1 1 2 J 121 Table XLVI. The time from which a marmot continuously occupied i t s t e r r i t o r y as i t s home burrow ^ f f T o t a l Juvenile Yearling Two year old June July August A p r i l May June J u l y May Females 2 0 0 0 2 2 0 3 9 Males 0 0 0 0 0 0 1 1 2 122 t e r r i t o r i e s as y e a r l i n g s used a vacant burrow system. The f o u r t h female o c c u p y i n g her t e r r i t o r i a l burrow as a y e a r l i n g , 0, shared i t w i t h her s i s t e r , an a d u l t male and, f o r f i v e weeks, w i t h an a d u l t female and l i t t e r . The a d u l t female moved i n t o O's burrow i n June about 5 days a f t e r her l i t t e r emerged. She d i s a p p e a r e d a f t e r J u l y 19. The 3 females t h a t d i d not c o n t i n u o u s l y occupy t h e i r t e r r i t o r y - t o - b e p r i o r t o t h e i r t h i r d year a l l used burrows t h a t had been the t e r r i t -o r i e s o f b r e e d i n g females the y e a r b e f o r e . Two o f the p r e -v i o u s owners had d i e d . The t h i r d burrow had been shared by two f e m a l e s , G and L. G was removed i n 1975- L v a c a t e d the burrow l a t e r t h a t summer and defended a new burrow the next s p r i n g . Females appear t o a c q u i r e t e r r i t o r i e s i n a t l e a s t two, p o s s i b l y t h r e e , ' ways. (1) They may spend most o f t h e i r y e a r -l i n g summer at a burrow u n o c c u p i e d by a b r e e d i n g female and the n defend t h a t burrow as a t e r r i t o r y t he f o l l o w i n g y e a r . (2) I n t h e s p r i n g o f t h e i r t h i r d y e a r , they may a c q u i r e a t e r r i t o r y made vacant by the death o r movement o f i t s p r e -v i o u s h o l d e r . (3) P o s s i b l y f e males t h a t a l l o w t h e i r daugh-t e r s on t h e i r t e r r i t o r i e s as y e a r l i n g s a l s o a l l o w them t o remain as b r e e d i n g two y e a r o l d s . The a d u l t f e m a l e , C, who t o l e r a t e d her da u g h t e r s a s y e a r l i n g s , was removed t h e same summer. The next year h er t h r e e d a u g h t e r s a c q u i r e d her ^.ter-r i t o r y . I t i s p o s s i b l e the t h r e e would have o c c u p i e d the t e r r i t o r y d e s p i t e the mother's p r e s e n c e . The p h y s i c a l s t r u c t u r e of the burrow and a d j o i n i n g 123 a r e a may a l l o w b r e e d i n g females t o t o l e r a t e o t h e r s a t the same burrow system. A d u l t female C's t e r r i t o r y mentioned above i n c l u d e d the burrows under a b a r n and near a w o o d p i l e about 3 meters away. There were s e v e r a l burrow e n t r a n c e s t h a t were b l o c k e d from s i g h t o f one a n o t h e r by the b a r n w a l l s , a f e n c e , and lumber. Some females produced l i t t e r s i n burrows w i t h o n l y two e n t r a n c e s . That t h e i r y e a r l i n g o f f s p r i n g r e s i d e d elsewhere may s i m p l y r e f l e c t the p h y s i c a l l i m i t a t i o n s o f a s m a l l burrow. A second f a c t o r a l l o w i n g females t o share or sub- . d i v i d e t e r r i t o r i e s a r e bonds of k i n s h i p . I n 1975 I saw o n l y one p a i r of females wean l i t t e r s at the same burrow system; each used s e p a r a t e e n t r a n c e s . I n May 1 9 7 6 , 7 o f the 12 t e r -r i t o r i a l females l i v e d a l o n e . The o t h e r 5 s u b d i v i d e d a t e r -r i t o r y w i t h t h e i r s i s t e r s . Two k i n groups shared what I c o n s i d e r e d the two "double burrow systems" i n the c o l o n y . I s u s p e c t e d each burrow was s e p a r a t e from t h e o t h e r under-ground, but they were so c l o s e t h a t females w i t h l i t t e r s had p r e v i o u s l y o c c u p i e d b o t h . I n one c a s e , two s i s t e r s each used one of t h e s e i m m e d i a t e l y a d j a c e n t burrows. I n the o t h e r , the t h r e e s i s t e r s d e s c r i b e d above d i v i d e d the t e r -r i t o r y so t h a t two used the b a r n and the t h i r d the burrow system j u s t b e h i n d i t . Both k i n groups s u b d i v i d i n g t e r r i t -o r i e s as two year o l d s had shared them as y e a r l i n g s . Pos-i. s i b l y the b r e e d i n g f e m a l e s , G. and L, s u b d i v i d i n g Burrow 5 i n both 1974 and 1975 were s i s t e r s . To summarize, females a c q u i r e d t e r r i t o r i e s by 124 o c c u p y i n g them as y e a r l i n g s or by l o c a t i n g vacant burrows as two year o l d s . I f a burrow system i s e x t e n s i v e enough, b r e e d i n g females may t o l e r a t e t h e i r y e a r l i n g d a u g h t e r s w i t h -i n t h e i r t e r r i t o r i e s and s i s t e r s may s u b d i v i d e t e r r i t o r i e s . The l i m i t e d i n f o r m a t i o n on males s u g g e s t s o n l y t h a t t hey a c -q u i r e t e r r i t o r i e s i n the s p r i n g of t h e i r t h i r d y e a r . 125 DISCUSSION ANNUAL CYCLE OF ACTIVITY Emergence From H i b e r n a t i o n The o r d e r o f emergence from h i b e r n a t i o n o f y e l l o w -b e l l i e d marmots i s t y p i c a l of o t h e r f o s s o r i a l s c i u r i d s . A d u l t s emerge b e f o r e y e a r l i n g s i n Marmot a monax (de Vo.s and G i l l e s p i e I 9 6 0 , Snyder, D a v i s and C h r i s t i a n 1 9 6 1 , D a v i s 1 9 6 7 ) , M. olympus (Barash 1 9 7 3 b ) , Spermophilus b e l d i n g i (Morton and G a l l u p 1 9 7 5 ) , and S. armatus ( S l a d e and B a l p h 1 9 7 4 ) . I n many s p e c i e s a d u l t males emerge b e f o r e a d u l t f e m a l e s : M. monax (Snyder and C h r i s t i a n I960, D a v i s 1 9 6 7 ) S. u n d u l a t u s (Hock I960, C a r l 1 9 7 1 ) , S. b e l d i n g i (Morton and G a l l u p 1 9 7 5 ) , S. b e e c h e y i ( L i n s d a l e 1 9 4 6 ) , S. f r a n k l i n i i ( I v e r s o n and Turner 1 9 7 2 ) , S_. l a t e r a l i s (McKeever 1 9 6 3 , S k r y j a and C l a r k 1 9 7 0 ) , S. columbianus (Shaw 1 9 2 5 b ) , S. r i c h a r d s o n i i ( C l a r k 1 9 7 0 , Yeaton 1 9 7 2 , Michener 1 9 7 4 ) , S. t e r e t i c a u d u s (Neal 1 9 6 5 b ) , S. t r i d e c e m l i n e a t u s ( W i s t r a n d 1 9 7 4 ) , S. armatus (Slade and B a l p h 1 9 7 4 ) , Cynomys l e u c u r u s (Bakko and Brown 1 9 6 7 ) . I f i n d i v i d u a l s emerge a t the time t h a t w i l l maximize t h e i r f i t n e s s , the d i f f e r e n t t i m e s o f emergence s h o u l d r e -f l e c t d i f f e r e n t s e l e c t i v e p r e s s u r e s . Among non - b r e e d i n g i n d i v i d u a l s s e l e c t i o n s h o u l d f a v o u r those t h a t emerge a t the time t h a t w i l l maximize t h e i r weight g a i n . Emergence s h o u l d 126 c o i n c i d e w i t h the i n i t i a t i o n o f v e g e t a t i v e growth. The o p t i m a l emergence date o f a b r e e d i n g female s h o u l d be a f -f e c t e d by o p p o s i n g s e l e c t i v e f o r c e s . She can maximize the p e r i o d o f growth f o r her o f f s p r i n g by emerging so e a r l y t h a t t h e i r b i r t h c o i n c i d e s w i t h the s t a r t o f v e g e t a t i v e growth. Or, she can maximize her own weight g a i n . S e l e c t i o n s h o u l d f a v o u r the female that,-emerges at l e a s t somewhat e a r l i e r t h a n optimum f o r her own growth and t h u s i n c r e a s e s the growing p e r i o d f o r her young. Hock ( I 9 6 0 ) suggested t h a t male a r c t i c ground s q u i r r e l s emerge b e f o r e females t o a l l o w t ime f o r the t e s t e s t o mature. However, i n s p e c i e s i n which males emerge i n b r e e d i n g c o n d i t i o n they s t i l l emerge b e f o r e females ( e . g . , Marmota monax. ( C h r i s t i a n , S t e i n b e r g e r and McKinney 1 9 7 2 ) , Spermophilus l a t e r e l i s , ( S k r y j a and C l a r k 1 9 7 0 , McKeever 1 9 6 3 ) and S. b e l d i n g i (Morton and G a l l u p 1 9 7 5 ) ) -As b r e e d i n g o c c u r s s h o r t l y a f t e r emergence, the o p t i m a l time f o r a male t o emerge i s j u s t b e f o r e the f i r s t f e m ale. S e l e c t i o n s h o u l d f a v o u r t h o s e who e r r e a r l i e r t h a n t h i s date r a t h e r than l a t e r . The c o s t o f emerging t o o e a r l y ( h i g h weight l o s s ) i s l e s s than i '-the c o s t o f emerging t o o l a t e (low r e p r o d u c t i v e s u c c e s s ) . Two t e s t i m p l i c a t i o n s a r i s e from t h i s h y p o t h e s i s o f emergence t i m e . F i r s t , a d u l t s s h o u l d l o s e weight a f t e r emergence. T h i s has been r e c o r d e d i n Marmota f l a v i v e n t r i s ( t h i s s t u d y ) , M. monax ( G r i z z e l l 1 9 5 5 5 Snyder et a l . 1 9 6 1 ) , Spermophilus u n d u l a t u s (Mayer and Roche 1 9 5 4 , Hock i 9 6 0 ) , 127 S. b e l d i n g i (Morton 1 9 7 5 ) , S. f r a n k l l n i i ( I v e r s o n and Turner 1 9 7 2 ) , S. l a t e r a l i s ( S k r y j a and C l a r k 1 9 7 0 ) and S_. t e r e t i c a u d u s (Neal 1 9 6 5 a ) . Second, y e a r l i n g s s h o u l d emerge l a t e r t h a n a d u l t s i n s p e c i e s where few y e a r l i n g s breed and o n l y i n t h o s e s p e c i e s . T h i s i m p l i c a t i o n i s s u p p o r t e d by n e a r l y a l l s t u d i e s o f s c i u r i d s (Table X L V I I ) . However y e a r l i n g female S. b e l d i n g i and p o s s i b l e male S_. t r i d e c e m l i n e a t u s b r e e d , but s t i l l emerge l a t e r t h a n a d u l t s . Y e a r l i n g S_. b e l d i n g i r e a c h the s m a l l e s t p r o p o r t i o n o f a d u l t weight compared t o t h o s e s p e c i e s i n which y e a r l i n g s t y p i c a l l y breed (Table X L V I I ) . P o s s i b l y the t r a d e - o f f a b r e e d i n g female makes between i n c r e a s i n g her own growth and t h a t o f . h e r o f f s p r i n g s h i f t s toward m a i n t a i n i n g her own w e i g h t . A s m a l l y e a r l i n g cannot " a f f o r d " t o emerge as e a r l y as a l a r g e r a d u l t . T h i s argument may s i m i l a r l y h o l d f o r S. t r i d e c e m l i n e a t u s . E n t r a n c e I n t o H i b e r n a t i o n Among both marmots and ground s q u i r r e l s , a d u l t males t y p i c a l l y h i b e r n a t e b e f o r e a d u l t females and a d u l t females b e f o r e j u v e n i l e s . P a r t o r a l l o f t h i s p a t t e r n has been ob-se r v e d i n Marmota f l a v i v e n t r i s ( t h i s s t u d y ) , M. Monax ( G r i z z e l l 1 9 5 5 ) , M. c a l i g a t a (Barash 1 9 7 6 ) , M. olympus (Barash 1 9 7 3 ) , S p e r m o p h i l i s u n d u l a t u s (Mayer and Roche 1 9 5 4 , Hock I 9 6 0 ) , S. b e l d i n g i (Morton et a l . 1 9 7 4 , Morton and Parmer 1 9 7 5 ) , S. b e e c h e y i (Evans and H o l d e n r e i d 1 9 4 3 , Tomich 1 9 6 2 ) , S. f r a n k l i n i i (Sowls 1 9 4 8 , Murie 1 9 7 3 ) , . S. l a t e r a l i s ( T e v i s 1 9 5 5 , S k r y j a and C l a r k 1 9 7 0 ) , Table XLVII. Y e a r l i n g emergence from hibernation, sexual maturity, and proportion of adult weight i n f o s s o r i a l s c i u r i d s Species Males Females Reference Time between Percent Proportion Time between Percent Proportion adult and sexually of adult adult and sexually of adult y e a r l i n g mature weight y e a r l i n g mature weight emergence (n) emergence (n) Marmota  olympus M. monax 1 month 2 Id 19cT 20d' M . f l a v i v e n t r i s ^ 1 0 d : Spermophilus 2 columbianus 21d S. armatus l a t e r than adults S. b e l d i n g i Cynomys leucurus l6d ' some 058(19) 13*(136) 37 53: .61 46 • 75J most 64 64" 1 month 0% .42 Barash 1973b . 5/5(19) .53 1 - G r i z z e l l 1955 26%(43) - Hamilton 1934' 53%(15) .66 Snyder et a l . 1961. Snyder and C h r i s t i a n i960 C h r i s t i a n et a l . 1972 Davis 1967 de Vos and G i l l e s p i e i960 t h i s study Armitage and Downhower 1974 9d->4d3,13d4 3d l a t e r than adults 3d 21%(34) .52 Shaw 1924,1925a,1925b Betts 1973 Moore 1937 Smith I947.in Betts 1973 Slade and Balph. 1974 ,71 Morton and Gallup 1975 Morton and Palmer 1975 - Sherman 1976 100$ .725 Bakko and Brown 1967 almost a l l . 7 5 0J<(16) 25?(28) 56^(68) 99% Table XLVTI. Y e a r l i n g emergence from h i b e r n a t i o n , sexual m a t u r i t y and p r o p o r t i o n of adu l t weight i n f o s s o r i a l s c i u r i d s (continued) Species Males Females Reference Time between Percent P r o p o r t i o n Time between Percent P r o p o r t i o n a d u l t and s e x u a l l y of adul t a d u l t and s e x u a l l y of adul t y e a r l i n g mature weight y e a r l i n g mature weight emergence (n) emergence (n) S;_ f r a n k l i n i i S. r i c h a r d s o n i ! -S. beecheyi S. undulatus S. t r i d e c e m l i n e a t u s lw S. t e r e t i c a u d u s -1 0 0 $ 1 0 0 5 5 1 0 0 5 5 yes 1 0 0 5 ? 1 0 0 5 5 .86 ,89-1005? - Iverson and Turner 1972 10055 - Shepherd 1972 955? .79 Mlchener 1974 almost a l l .88 Evans and Holdenried 1943 yes Tomich 1962 almost a l l .99 Mayer and Roche 1954 yes McCarley 1966 Clark 1971 Neal 1965b -.Males and females combined. oDif f e r e n c e between e a r l i e s t emergence dates. ^ D i f f e r e n c e between dates at which 10% of each ,-Difference i n conception dates. g P r e - h i b e r n a t i o n weights. A d u l t s and y e a r l i n g s combined. age c l a s s had emerged. i—1 (V) vo 130 S. r l c h a r d s o n l i (Yeaton 1 9 7 2 , Michener 1 9 7 4 ) , S. t r i d e c e m l i n e a t u s (McCarley 1 9 6 6 , C l a r k 1 9 7 1 ) , S. armatus (Sl a d e and B a l p h 1 9 7 4 ) , Cynomys g u n n i s o n i ( F i t z g e r a l d and L e c h l e i t n e r 1 9 7 4 ) and C_. l e u c u r u s (Bakko and Brown 1 9 6 7 ) . W i t h i n age c l a s s e s , h e a v i e r i n d i v i d u a l s h i b e r n a t e b e f o r e l i g h t e r ones i n S. b e l d i n g i (Morton et a l . 1 9 7 4 ) and pos-s i b l y S. r i c h a r d s o n i i (Michener 1 9 7 4 ) . I n marmot s p e c i e s j u v e n i l e s e n t e r h i b e r n a t i o n l e s s t h a n one month a f t e r a d u l t males. The d i f f e r e n c e i s g r e a t e r i n many ground s q u i r r e l ; s p e c i e s . J u v e n i l e R i c h a r d s o n ' s ground s q u i r r e l s may e n t e r h i b e r n a t i o n over t h r e e months a f t e r a d u l t males (Yeaton 1 9 7 2 , Michener 1 9 7 4 ) . The o p t i m a l time t o e n t e r h i b e r n a t i o n i n o r d e r t o maximize f i t n e s s may be determined by two o p p o s i n g s e l e c t i v e f o r c e s . ( 1 ) High body weight and f a t s t o r e s s h o u l d i n c r e a s e s u r v i v a l d u r i n g h i b e r n a t i o n (as i t d i d f o r j u v e n i l e s i n t h i s s t u d y ) and d u r i n g the s p r i n g b r e e d i n g season when f o o d i s u n a v a i l a b l e . A s q u i r r e l w i l l maximize h i s weight g a i n by r e m a i n i n g a c t i v e as l o n g as food i s a v a i l a b l e . However ( 2 ) the p r o b a b i l i t y of d y i n g d u r i n g h i b e r n a t i o n might, as t h i s study f o u n d , be lower t h a n the p r o b a b i l i t y o f d y i n g ( i n the same u n i t o f t i m e ) d u r i n g the a c t i v e season. I n t h i s c a s e , the s q u i r r e l w i l l maximize h i s p r o b a b i l i t y o f s u r v i v i n g the summer by h i b e r n a t i n g as e a r l y as p o s s i b l e . The o p t i m a l s t r a t e g y w i l l b a l a n c e the b e n e f i t o f s t a y i n g a c t i v e ( t o g a i n weight and i n c r e a s e the p r o b a b i l i t y o f s u r v i v i n g d u r i n g h i b e r n a t i o n and e a r l y s p r i n g ) a g a i n s t the c o s t ( i n c r e a s e d p r o b a b i l i t y o f d y i n g b e f o r e h i b e r n a t i o n ) . T h i s h y p o t h e s i s i s shown g r a p h i c a l l y i n P i g . 13 t o F i g . 1 5 . The o p t i m a l t i m e t o e n t e r h i b e r n a t i o n depends on f o u r f a c t o r s : ( 1 ) growth r a t e and time a t which growth b e g i n s ( F i g . 1 3 a ) , ( 2 ) the r e l a t i o n s h i p between p r e -h i b e r n a t i o n weight and o v e r w i n t e r s u r v i v a l ( F i g . 1 3 b ) , ( 3 ) w e i g h t - i n d e p e n d e n t m o r t a l i t y d u r i n g h i b e r n a t i o n , and ( 4 ) a c t i v e season m o r t a l i t y ( F i g . 1 5 a ) . F i g . 1 3 a d e s c r i b e s weight change d u r i n g the a c t i v e season. The r e l a t i o n s h i p i s l i n e a r i n the youngest age c l a s s (Snyder et a l . 1 9 6 1 , I v e r s o n and Turner 1 9 7 2 , Barash 1 9 7 3 , Murie 1 9 7 3 , Michener 1 9 7 4 , '< Morton e t a l . 1 9 7 4 ) . The same i s t r u e o f a d u l t s i n some s p e c i e s ( I v e r s o n and Turn e r 1 9 7 2 , B a r a s h 1 9 7 3 , Michener 1 9 7 4 ) . I n o t h e r s , t h e r e i s a p e r i o d of weight l o s s o r c o n s t a n t weight- a f t e r emergence, t h e n r a p i d growth u n t i l h i b e r n a t i o n (Snyder et a l . 1 9 6 1 , Murie 1 9 7 3 , Morton 1 9 7 5 , M o r r i s o n and G a l s t e r 1 9 7 6 ). I n t h i s study the phase o f r a p i d growth was f o l l o w e d by a p r o l o n g e d p e r i o d o f c o n s t a n t w e i g h t . I n the g e n e r a l i z e d c u r v e , weight e v e n t u a l l y d e c l i n e s from l a c k o f food i n the f a l l . O v e r w i n t e r s u r v i v a l i s assumed t o have a v e r y low p r o b a b i l i t y below a c e r t a i n weight and t o r e a c h a t h r e s h o l d at some h i g h e r weight ( F i g . 1 3 b ) . At a g i v e n weight j u v e -n i l e s u r v i v a l i s assumed g r e a t e r t h a n a d u l t because a g r e a t e r p r o p o r t i o n o f t h e body weight may be f a t . Weight-independent m o r t a l i t y d u r i n g h i b e r n a t i o n ( e . g . , f l o o d i n g , p r e d a t i o n ) i s i g n o r e d as i t i s assumed independent o f age F i g u r e 13a. G e n e r a l i z e d p a t t e r n o f growth i n marmots and ground s q u i r r e l s . Month 1 i s when a d u l t s emerge from h i b e r n a t i o n . 13b. The h y p o t h e s i s dependence of the p r o b a -b i l i t y o f s u r v i v i n g h i b e r n a t i o n on the weight upon e n t e r i n g h i b e r n a t i o n . F i g u r e 14 . The h y p o t h e s i z e d dependence o f the p r o b a b i l i t y o f s u r v i v i n g h i b e r n a t i o n on the time at which h i b e r n a t i o n b e g i n s . Month 1 i s s p r i n g emergence from h i b e r n -a t i o n . The c u r v e s are d e r i v e d from t h o s e i n F i g . 13a and b. 135 F i g u r e 15a. G e n e r a l i z e d s u r v i v o r s h i p curve o f marmots and ground s q u i r r e l s . Month 1 i s emerg-ence from h i b e r n a t i o n i n the s p r i n g . F i g u r e 15b. P r o b a b i l i t y of s u r v i v i n g one year as a f u n c t i o n o f the time h i b e r n a t i o n b e g i n s . The cur v e s are d e r i v e d from t h o s e i n F i g . 14 and 15a. T i m e at W h i c h H i b e r n a t i o n B e g i n s ( M o n t h s ) 13 and sex. (High m o r t a l i t y t h a t i s independent o f weight or f a t r e s e r v e s s h o u l d s e l e c t f o r l a t e h i b e r n a t i o n . ) The p r o b a b i l i t y o f s u r v i v i n g h i b e r n a t i o n as a f u n c -t i o n o f the time h i b e r n a t i o n b e g i n s ( F i g . 14) depends on the growth p a t t e r n ( F i g . 1 3 a ) and the r e l a t i o n s h i p between o v e r w i n t e r s u r v i v a l and p r e h i b e r n a t i o n weight ( F i g . 1 3 b ) . That i s , the c u r v e s i n F i g . 14 are d e r i v e d d i r e c t l y from those i n F i g . 1 3 a and b. M o r t a l i t y o f a d u l t s i s assumed t o be c o n s t a n t t h r o u g h the observed a c t i v e season and t o i n c r e a s e l a t e r i n the f a l l from weather and l a c k o f f o o d ( F i g . 15a). J u v e n i l e s f o l l o w a s i m i l a r p a t t e r n a s i d e from an i n i t i a l p e r i o d o f h i g h mort-a l i t y (see C a r l 1971). Annual s u r v i v a l , S A, ( F i g . 15b) i s a f u n c t i o n o f a c t i v e season s u r v i v a l Sg, ( F i g . 1 5 a ) and s u r v i v a l d u r i n g h i b e r n a t i o n , ST. , , ' W such t h a t S A = S S X SW The date h i b e r n a t i o n b e g i n s d e t e r m i n e s Sg x S^. The o p t i m a l date i s the p o i n t a t which the s l o p e o f F i g . 1 5 a exceeds t h a t of F i g . 14 above t h e i n f l e c t i o n p o i n t . T r a i t s s e l e c t i n g f o r e a r l y h i b e r n a t i o n are r a p i d growth, low maximum body w e i g h t , r a p i d i n c r e a s e i n o v e r w i n t e r s u r v i v a l w i t h i n c r e a s e d weight ( i . e . , s t e e p s l o p e i n F i g . 1 3 b ) , h i g h a c t i v e season m o r t a l -i t y , and low w e i g h t - i n d e p e n d e n t m o r t a l i t y d u r i n g h i b e r n a t i o n . I n the example, the o p t i m a l time f o r j u v e n i l e s t o 139 h i b e r n a t e i s two months a f t e r a d u l t s . The s m a l l e r s i z e of j u v e n i l e s has more e f f e c t on t h e i r time o f h i b e r n a t i o n t h a n t h e i r h i g h e r m o r t a l i t y r a t e i n the a c t i v e season. The model a l s o p r e d i c t s t h a t the o p t i m a l time o f h i b e r n a t i o n o f a d u l t males sh o u l d be e a r l i e r t h a n t h a t o f a d u l t females as males b e g i n g a i n i n g weight b e f o r e pregnant and l a c t a t i n g females do. S i m i l a r l y , w i t h i n an age-sex c l a s s , h e a v i e r i n d i v i d u a l s s h o u l d h i b e r n a t e b e f o r e l i g h t e r ones. The h y p o t h e s i s assumes t h a t those i n d i v i d u a l s t h a t h i b e r n a t e e a r l y c o u l d c o n t i n u e t o g a i n weight i f they remained a c t i v e . T h i s a ssumption i s c o n s i s t e n t w i t h observed p l a n t p r o d u c t i v i t y a t t h e time o f h i b e r n a t i o n (Morton 1 9 7 5 , D. Heard, p e r s o n n a l communication). 140 REPRODUCTION E f f e c t o f M a t e r n a l C o n d i t i o n on R e p r o d u c t i v e Output Most of the v a r i a b i l i t y i n the r e p r o d u c t i v e p a r a -meters o f the Watch Lake marmots i s d i r e c t l y l i n k e d t o meas-ure s of the mother's c o n d i t i o n . Her weight a f t e r emergence from h i b e r n a t i o n and her weight g a i n from the p r e c e d i n g year appear t o determine the s i z e , w e i g h t , emergence d a t e , and sex r a t i o of her l i t t e r , r e g a r d l e s s o f her age. The weight of i n d i v i d u a l j u v e n i l e s at weaning i s d e t e r m i n e d • m a i n l y by the s i z e o f the l i t t e r and s e c o n d a r i l y by the weight o f t h e mother. A female's c o n d i t i o n at b r e e d i n g depended on her r e p r o d u c t i v e e f f o r t the p r e c e d i n g y e a r . Females t h a t p r o -duced heavy l i t t e r s one year were i n p o o r e r c o n d i t i o n the f o l l o w i n g y e a r and c o n s e q u e n t l y produced l i g h t l i t t e r s t h a t y e a r . B i e n n i a l b r e e d i n g c h a r a c t e r i s t i c o f some n e a r t i c .. : marmots (Marmota olympus, Barash 1 9 7 3 b , M. c a l i g a t a , B a r a s h 1 9 7 4 a , M. V a n c o u v e r e n s i s , Heard 1 9 7 7 ) may r e p r e s e n t an ex-treme form o f t h i s p a t t e r n . Females i n these s p e c i e s may take more th a n one a c t i v e season t o r e g a i n s u f f i c i e n t weight to b r e e d . One would p r e d i c t t h e i r w e i g h t s at emergence from h i b e r n a t i o n a r e a l t e r n a t e l y h i g h ( I n b r e e d i n g y e a r s ) and low ( I n n o n - b r e e d i n g y e a r s ) . R e p r o d u c t i o n i n v o l v e s two e n e r g e t i c t r a d e - o f f s . F i r s t , a v a i l a b l e energy may be c h a n n e l l e d i n t o e i t h e r r e p r o -d u c t i o n or growth. Second, the energy f o r r e p r o d u c t i o n may be p a r t i t i o n e d i n t o many s m a l l o f f s p r i n g o r a few l a r g e ones. 1 4 1 The former t r a d e - o f f appears t o determine the p a r t i t i o n i n g o f the l a t t e r . H i g h r e p r o d u c t i v e e f f o r t one y e ar i s f o l l o w e d by s m a l l l i t t e r s of c o n s e q u e n t l y l a r g e young the next y e a r . The amount of energy c h a n n e l l e d i n t o r e p r o d u c t i o n i s approx-i m a t e l y t h a t which a l l o w s an a n n u a l weight change of 0. V a r i a b i l i t y i n the amount of energy a s s i m i l a t e d a f t e r wean-i n g and weight l o s s o v e r w i n t e r and " e r r o r " i n e s t i m a t i o n o f the a p p r o p r i a t e e x p e n d i t u r e on r e p r o d u c t i o n may cause the s m a l l net weight g a i n s and l o s s e s o b s e r v e d . E f f e c t o f L i t t e r S i z e on the Weights o f J u v e n i l e s The observed d e c l i n e o f j u v e n i l e w e i g h t s w i t h l i t t e r s i z e i s c h a r a c t e r i s t i c of a n o t h e r w i l d s c i u r i d , S. b e l d i n g i (Sherman 1 9 7 6 ) and many c a p t i v e r o d e n t s (Shaw 1 9 2 5 a , Lack 1 9 4 8 , H a m i l t o n 1 9 6 2 , Cameron 1 9 7 3 , M i l l a r 1 9 7 5 , Lac:key 1 9 7 6 , T u r n e r , I v e r s o n and Severson 1 9 7 6 , Randolph, M a t t i n g l y and F o s t e r 1 9 7 7 )• A l t h o u g h l a c t a t i n g f e m ales i n c r e a s e t h e i r f o o d i n t a k e ( i n c a p t i v i t y ) i n response t o l i t t e r s i z e ( M i g u l a 1969, ' M i l l a r 1 9 7 5 , Randolph 1 9 7 7 ) , the i n c r e a s e i s not s u f f i c i e n t t o compensate f o r the i n c r e a s e i n l i t t e r s i z e . O p t i m a l L i t t e r S i z e o f Marmots at Watch Lake The o p t i m a l l i t t e r s i z e i s t h a t p r o d u c i n g the g r e a t -e s t number of b r e e d i n g a d u l t s . The optimum depends on the r e l a t i o n s h i p j b e t w e e n o f f s p r i n g f i t n e s s and l i t t e r s i z e . I w i l l d i s c u s s t h r e e p o s s i b l e r e l a t i o n s h i p s . ( 1 ) O f f s p r i n g f i t n e s s may be u n a f f e c t e d by l i t t e r s i z e . The o p t i m a l s i z e would t h e n be the l a r g e s t p o s s i b l e . That i s , p a r e n t a l f i t n e s s would be a l i n e a r f u n c t i o n o f l i t t e r s i z e , f = n f P o where f = p a r e n t a l f i t n e s s , n = l i t t e r s i z e , and f Q = o f f s p r i n g f i t n e s s . However, the weight of j u v e n i l e marmots dec r e a s e s w i t h l i t t e r s i z e . S i n c e weight may a f f e c t f i t n e s s , o f f s p r i n g f i t n e s s may d e c l i n e w i t h l i t t e r s i z e . .(2) I f o f f -s p r i n g f i t n e s s d e c l i n e s e x p o n e n t i a l l y ( o f f s p r i n g f i t n e s s = 1 / l i t t e r s i z e ) , t h e n p a r e n t a l f i t n e s s s h o u l d not v a r y w i t h l i t t e r s i z e , F = n(-) = 1 p n No l i t t e r s i z e i s o p t i m a l . ( 3 ) O f f s p r i n g f i t n e s s may d e c l i n e a t a r a t e t h a t d e c r e a s e s w i t h l i t t e r s i z e . P r o p o r t i o n a t e l y the g r e a t e s t change I n f i t n e s s would o c c u r at s m a l l l i t t e r s i z e s . Under t h i s a s s u m p t i o n , p a r e n t a l f i t n e s s would i n i t i -a l l y i n c r e a s e w i t h l i t t e r s i z e , peak at an o p t i m a l l i t t e r . i s i z e , and d e c l i n e w i t h l a r g e r l i t t e r s . P i a n k a ( 1 9 7 6 ) p r e -s e n t s a g r a p h i c a l r e p r e s e n t a t i o n o f assumptions ( 2 ) and ( 3 ) -An i n d e x o f p a r e n t a l f i t n e s s i s the number of y e a r -l i n g s a l i t t e r p roduces; an i n d e x o f j u v e n i l e f i t n e s s i s the p r o b a b i l i t y o f s u r v i v i n g one y e a r . W ith t h e s e measures of f i t n e s s , F i g . 16 g r a p h i c a l l y d e p i c t s the t h r e e p o s s i b l e r e l a t i o n s h i p s o f p a r e n t a l f i t n e s s t o l i t t e r s i z e . The number of y e a r l i n g s a g i v e n l i t t e r s i z e produced at Watch Lake bears no r e l a t i o n t o t h e p a r e n t a l f i t n e s s p r e d i c t e d under assumptions ( 1 ) and ( 2 ) ( c u r v e s a and b ) . P a r e n t a l f i t n e s s , F i g u r e 16. The number o f j u v e n i l e s s u r v i v i n g t o y e a r -l i n g s , as a f u n c t i o n o f . l i t t e r s i z e . Curve a: p r e d i c t e d number o f y e a r l i n g s i f j u v e n i l e s u r v i v a l i s independent of l i t t e r s i z e . y = . 39x where •39 = j u v e n i l e s u r v i v a l . Curve b: p r e d i c t e d number o f y e a r l i n g s i f j u v e n i l e s u r v i v a l d e c l i n e s exponen-t i a l l y w i t h l i t t e r s i z e . Curve c: p r e d i c t e d number o f y e a r l i n g s i f j u v e n i l e s u r v i v a l d e c r e a s e s more w i t h s m a l l l i t t e r s i z e s t h a n l a r g e l i t t e r s . N umber of Y e a r I i ng s May 1975 ro W j> on O D" CO t7t7T and hence o f f s p r i n g f i t n e s s meet assumption ( 3 ) ( c u r v e c) most c l o s e l y . O f f s p r i n g f i t n e s s ( i n terms o f p r o b a b i l i t y o f s u r v i v a l t o one yea r ) must then, d e c l i n e w i t h l i t t e r s i z e , but d e c l i n e p r o p o r t i o n a t e l y l e s s at l a r g e l i t t e r s i z e s . The o p t i m a l l i t t e r s i z e appears t o be 6 which, not u n e x p e c t e d l y , i s t he same as the mean l i t t e r s i z e . S i g n i f i c a n c e o f Emergence Date o f L i t t e r s The l a t e r j u v e n i l e s emerge, the lower t h e i r f i t n e s s s h o u l d be. The emergence da t e a f f e c t s the time j u v e n i l e s have t o grow b e f o r e h i b e r n a t i o n and hence t h e i r weight a t h i b e r n a t i o n . O v e r w i n t e r s u r v i v a l o f heavy j u v e n i l e s I s g r e a t e r t h a n l i g h t ones (Table X I I I ) . I n t h i s s t u d y , the h e a v i e r a female was, the e a r l i e r her l i t t e r emerged. As w e l l , the l a r g e r a l i t t e r was, the e a r l i e r i t emerged. The same r e l a t i o n s h i p between l i t t e r s i z e and emergence da t e i s found i n Marmota f l a v l v e n t r l s p o p u l a t i o n s i n C o l o r a d o . The s i z e o f 65 l i t t e r s grouped i n t o f i v e p e r i o d s o f emergence d e c l i n e d from l a t e June to e a r l y August ( r = - . 9 9 , p < . 0 1 , d a t a from Armitage e t a l . 1 9 7 6 , T a b l e 6 ) . De Vos' and G i l l e s p i e ' s (I960) o b s e r v a t i o n s o f M. monax r e v e a l the same t r e n d ( r = - . ' 6 2 6 , n = 8 , p < . 1 0 , d a t a from Table 1 ) . T h i s phenomenon I s a l s o t y p i c a l of many b i r d s . The s i z e o f f i r s t c l u t c h e s d e c l i n e s as t h e i n i t i a l l a y i n g date becomes l a t e r i n some l a r i d s (Coulson and White I960, Ryder 1 9 7 5 , Table 1 , r = - . 8 6 9 , n = 1 8 , p < . 0 0 1 , Parsons 1 9 7 6 , Table 6 , r = - . 8 9 5 , n = 6 , p <. .05) t e t r o n i d s (Bergerud 1 9 7 0 , Robel and B a l l a r d 1 9 7 4 ) , and o t h e r b i r d s 146 H u s s e l l 1 9 7 2 , Lack 1 9 6 6 ) . D i f f e r e n c e s i n emergence dates of l i t t e r s can r e p r e -sent d i f f e r e n c e s i n time of c o n c e p t i o n , l e n g t h of g e s t a t i o n , or l e n g t h o f l a c t a t i o n . V a r i a t i o n i n g e s t a t i o n p e r i o d i s l i k e l y i n s u f f i c i e n t t o e x p l a i n the v a r i a b i l i t y i n d a t e s of emergence observed i n t h i s s t u d y . I n Spermophilus b e l d i n g i , the c o n c e p t i o n date i s c o r r e l a t e d w i t h the emergence da t e (Sherman 1 9 7 6 ) . However, l e n g t h of l a c t a t i o n a l s o v a r i e s . I n S. t e r e t i c a u d u s , a h i b e r n a t i n g ground s q u i r r e l i n A r i z o n a , b o t h the i n c e p t i o n o f b r e e d i n g and the a n n u a l mean l i t t e r s i z e are c o r r e l a t e d w i t h the r a i n f a l l d u r i n g the p r e -v i o u s w i n t e r (Reynolds and T u r k o w s k i 1 9 7 2 ) . R a i n f a l l l i k e l y a f f e c t s the p r o d u c t i o n o f s p r i n g a n n u a l s , the s q u i r r e l s ' " ' J f o o d s o u r c e . Perhaps the v a r i a n c e i n emergence d a t e s of y e l l o w - b e l l i e d marmot.: l i t t e r s a l s o r e f l e c t s d i f f e r e n c e s i n c o n c e p t i o n d a t e s determined by the mother's c o n d i t i o n , t h o s e females i n good c o n d i t i o n b r e e d i n g e a r l y and c o n c e i v i n g l a r g e l i t t e r s . Sex R a t i o o f L i t t e r s The p r o p o r t i o n o f males i n a l i t t e r i n c r e a s e d w i t h the mother's w e i g h t , i n c r e a s e d w i t h t h e l i t t e r ' s s i z e , and d e c r e a s e d as l i t t e r s emerged l a t e r . An e x p l a n a t i o n of the observed c o r r e l a t i o n s c o u l d assume t h a t the sex r a t i o at weaning r e f l e c t e d the sex r a t i o at c o n c e p t i o n or t h a t i t r e s u l t e d from d i f f e r e n t i a l m o r t a l i t y d u r i n g g e s t a t i o n and l a c t a t i o n . I f one f i r s t assumes t h a t males s u f f e r g r e a t e r m o r t a l i t y b e f o r e weaning, t h e n one would expect females i n 147 good c o n d i t i o n t o l o s e fewer young, hence fewer males, t h a n females i n poor c o n d i t i o n . Heavy females s h o u l d t h e n wean l a r g e r l i t t e r s w i t h a g r e a t e r p r o p o r t i o n o f males t h a n l i g h t f e m a l e s . (The c o r r e l a t i o n between a l i t t e r ' s sex r a t i o and i t s emergence date may be caused by the dependence o f b o t h v a r i a b l e s on t h e mother's c o n d i t i o n . ) T h i s e x p l a n a t i o n assumes t h e r e i s c o n s i d e r a b l e m o r t a l -i t y between c o n c e p t i o n and weaning. However, the o b s e r v a r i . . . t i o n s i n d i c a t e t h a t l i t t e r s i z e s at weaning were c l o s e t o those at i m p l a n t a t i o n . Perhaps i f t h e l o s s were r e s t r i c t e d t o males, a s m a l l l o s s would a l t e r the sex r a t i o more t h a n the l i t t e r s i z e . The f r e q u e n c y o f males i n seven l i t t e r s o f 4 and 5 was .424 (n = 33). I n f i v e l i t t e r s of 8 and 9 i t \ was .595 (n = 42). For the s m a l l l i t t e r s t o have c o n c e i v e d the same p r o p o r t i o n of males as the l a r g e l i t t e r s (.595), t h e y would have t o have l o s t 2.0 males (and 0 f e m a l e s ) per l i t t e r . I f any females were l o s t , t he number o f males would have t o be even g r e a t e r t o m a i n t a i n the same r a t i o . Known l o s s from f o u r l i t t e r s o f 5 o r l e s s was o n l y .75 y o u n g / l i t t e r . None had l o s t 2 young. Thus g r e a t e r m o r t a l i t y of males b e f o r e weaning may not be s u f f i c i e n t t o e x p l a i n t h e c o r r e l a t i o n between l i t t e r s i z e and sex r a t i o a t weaning. I f d i f f e r e n t i a l m o r t a l i t y b e f o r e weaning i s m i n i m a l , t h e n the sex r a t i o at weaning s h o u l d r e f l e c t n a t u r a l s e l e c -t i o n a c t i n g on the p r i m a r y sex r a t i o . F i s h e r (1958) con-c l u d e d t h a t the sex r a t i o s h o u l d e q u a l i z e p a r e n t a l e x p e n d i -t u r e on each sex. I n t h i s s t u d y , s i z e dimorphism d e c r e a s e d w i t h l i t t e r s i z e , w h i l e the p r o p o r t i o n o f males i n c r e a s e d . Perhaps the l a t t e r phenomenon i s a c o r e q u i s i t e o f t h e former a l l o w i n g e x p e n d i t u r e on each sex t o remain c o n s t a n t . Eovi-~ e v e r the c o r r e l a t i o n between the p r o p o r t i o n o f l i t t e r weight i n v e s t e d i n males and l i t t e r s i z e ( r = . 4 7 6 , n = 1 3 , p = . 1 0 5 ) i s almost as s t r o n g as t h a t between p r o p o r t i o n t h a t are males (sex r a t i o ) and l i t t e r s i z e . Thus the in-:/_-c r e a s e i n males w i t h l i t t e r s i z e does not s i m p l y compensate f o r changes i n s i z e dimorphism. T r i v e r s and W i l l a r d ( 1 9 7 3 ) proposed t h a t i n p o l y -gamous s p e c i e s females i n good c o n d i t i o n s h o u l d produce a h i g h e r p r o p o r t i o n o f male o f f s p r i n g t h a n those i n poor con-d i t i o n . T h e i r h y p o t h e s i s assumed t h a t t h e f i t n e s s o f male o f f s p r i n g was more a d v e r s e l y a f f e c t e d by a d e c l i n e i n mater-n a l c o n d i t i o n , and hence o f f s p r i n g s i z e , t h a n the f i t n e s s o f f e m a l e s . The p o s i t i v e c o r r e l a t i o n between the f r e q u e n c y o f males and the c o n d i t i o n o f the mother i n t h i s s tudy i s con-s i s t e n t w i t h the T r i v e r - W i l l a r d h y p o t h e s i s . However the c o n c o m i t a n t i n c r e a s e I n l i t t e r s i z e w i t h the m a t e r n a l con-d i t i o n causes a d e c l i n e i n the w e i g h t s of i n d i v i d u a l j u v e -n i l e s . Hence no s i m p l e c o r r e l a t i o n e x i s t s between j u v e n i l e weight and e i t h e r the sex r a t i o ( r = -.040) o r t h e weight of the mother ( r = . 1 6 3 ) . S i n c e females i n good c o n d i t i o n do not tend t o produce l a r g e o f f s p r i n g , t h e r e s h o u l d be no s e l e c t i v e advantage i n p r o d u c i n g a h i g h p r o p o r t i o n o f males. T h i s c o n t r a d i c t i o n i s i m p l i c i t i n T r i v e r s ' and W i l l a r d T s own argument. . F i r s t t hey contend t h a t females i n 149 good c o n d i t i o n s h o u l d produce more males. Next they acknow-ledge the i n v e r s e r e l a t i o n s h i p between l i t t e r s i z e and o f f -s p r i n g s i z e . Large l i t t e r s , because of d e c r e a s e d i n v e s t m e n t per o f f s p r i n g , s h o u l d c o n t a i n more f e m a l e s . However the con-d i t i o n o f t h e mother i s l i k e l y r e f l e c t e d more i n the number t h a n t h e s i z e o f the o f f s p r i n g . That i s , females i n good c o n d i t i o n s h o u l d t e n d t o produce l a r g e r l i t t e r s r a t h e r t h a n l a r g e r young. T h i s T r i v e r s and W i l l a r d i g n o r e . T h e i r h y p o t h e s i s may s t i l l be v a l u a b l e when r e s t r i c t e d t o s p e c i e s t h a t t y p i c a l l y bear one young p e r r e p r o d u c t i v e e f f o r t . The o r i g i n o f the observed c o r r e l a t i o n s between l i t t e r sex r a t i o and l i t t e r s i z e and l i t t e r sex r a t i o and m a t e r n a l weight remains u n c l e a r . I t i s p o s s i b l e females a r e maximiz-i n g t h e i r f i t n e s s by p r o d u c i n g more male o f f s p r i n g i n l a r g e l i t t e r s . However, the p a r t i c u l a r s e l e c t i o n p r e s s u r e s i n v o l v o l v e d a re not ap p a r e n t . The c o r r e l a t i o n s may be s p u r i o u s . 150 COMPARISON OF SOCIAL ORGANIZATION WITH OTHER POPULATIONS The s p a c i n g b e h a v i o u r o f a d u l t males i s s i m i l a r t o those i n p o p u l a t i o n s i n C o l o r a d o . Barash ( 1 9 7 3 a ) and Armitage ( 1 9 7 4 ) observed t e r r i t o r i a l i t y among a d u l t males. Males i n both t h e s e p o p u l a t i o n s o c c u p i e d f i x e d and e x c l u s i v e home ranges. T r e s p a s s i n g and c o n s e q u e n t l y defense were r a r e . B a r a s h r e c o r d e d 3 chases between a d u l t males i n 327 hours o f o b s e r v a t i o n ( 1 chase / 1 0 9 h r s . ) . Armitage observed 9 i n 1714 hours ( 1 chase / 1 9 0 h r s . ) . The absence o f a g o n i s t i c en-c o u n t e r s among males at the Watch Lake c o l o n i e s may be an e f f e c t of t h e time I spent o b s e r v i n g , o n l y 192 hours at t h e Home Colony. I n n e i t h e r C o l o r a d o p o p u l a t i o n were t e r r i t o r i e s near c o n t i g u o u s . T h i s a l l o w e d y e a r l i n g " males t o occupy home ranges t h a t d i d not o v e r l a p the a d u l t s ' t e r r i t o r i e s . The mean t e r r i t o r y s i z e i n A r m i t a g e ' s p o p u l a t i o n was 0 . 7 9 ha. I t ranged from 0 . 3 5 to 1 . 4 8 ha (n = 7 ) . As the number o f ha/males ( . 7 6 i n the Old Colony, .:95 i n the Home C o l o n y ) ' s h o u l d o v e r e s t i m a t e t e r r i t o r y s i z e , t e r r i t o r i e s i n the Watch Lake p o p u l a t i o n s are l i k e l y s m a l l e r t h a n t h o s e i n the E a s t R i v e r V a l l e y , C o l o r a d o . T h i s i s s u p p o r t e d by t h e d e n s i t y o f males i n another Colorado p o p u l a t i o n . Andersen e t a l . ( 1 9 7 6 ) had 3 a d u l t males i n a study a r e a o f about 7 ha, or 2 . 3 ha/male, a d e n s i t y o n e - t h i r d t h a t o f the Old Colony. Y e a r l i n g s i n o t h e r p o p u l a t i o n s behave s i m i l a r l y t o t h o s e at; Watch .Lake. They share: t h e i r home: ranges . w i t h .other 151 y e a r l i n g s ( B a r a s h 1 9 7 3 a ) , Armitage 1974), were chased by a d u l t s (Barash 1 9 7 3 a ) , e s p e c i a l l y a d u l t females (Armitage 1 9 7 5 ) , and males a v o i d e d a d u l t males (Armitage 1 9 7 4 ) . Armitage ( 1 9 7 4 ) s t a t e s t h a t y e a r l i n g females a v o i d e d a d u l t males. I t i s u n c l e a r whether t h i s d i f f e r s from y e a r l i n g f e m a l e - a d u l t male r e l a t i o n s a t Watch Lake. A l t h o u g h y e a r - , l i n g females used the burrows o f a d u l t males, they may have r e s p e c t e d an i n d i v i d u a l d i s t a n c e o f a d u l t males when i n c l o s e p r o x i m i t y . The s p a c i n g and a g o n i s t i c b e h a v i o u r o f a d u l t females i n o t h e r p o p u l a t i o n s bore some s i m i l a r i t y t o t h a t o f females at Watch Lake. A d u l t females i n a Wyoming p o p u l a t i o n engaged i n h i g h l e v e l s of a g o n i s t i c b e h a v i o u r d u r i n g the f i r s t f i v e weeks a f t e r emergence (Armitage 1 9 6 5 ) . The r a t e s peaked d u r i n g the week p r e c e d i n g p a r t u r i t i o n . A d u l t females use f i x e d home burrows i n o t h e r p o p u l a t i o n s (Armitage 1 9 6 5 , Barash 1 9 7 3 a , Svendsen 1 9 7 4 ) . They t e n d toward e x c l u s i v e use o f t h e s e burrows. I n the Y e l l o w s t o n e Park p o p u l a t i o n of 19 females w i t h l i t t e r s , o n l y two p a i r s shared a burrow (Armitage 1 9 6 2 ) . Two o t h e r b r e e d i n g females each t o l e r a t e d a n o t h e r a d u l t i n t h e i r burrow. I n a t l e a s t one o f t h e s e c a s e s , the b r e e d i n g female and the no n - b r e e d i n g female used s e p a r a t e s e t s o f e n t r a n c e s . I n a c o l o n y c o n t a i n i n g two ..: . b r e e d i n g females out o f 8 a d u l t s and y e a r l i n g s . B a r a s h ( 1 9 7 3 ) never observed an a d u l t or y e a r l i n g e n t e r i n g the fe m a l e s ' burrows. I n t h a t c o l o n y a l l i n d i v i d u a l s were dom-i n a n t a t t h e i r home burrows. Svendsen ( 1 9 7 6 ) r e p o r t s an 152 a d u l t female w i t h a l i t t e r moving i n t o the burrow o f another female w i t h l i t t e r and d i s p l a c i n g them. However, two major d i f f e r e n c e s i n female s p a c i n g be-h a v i o u r e x i s t . F i r s t , b r e e d i n g females a t Watch Lake a r e t e r r i t o r i a l . T h i s i s the f i r s t r e p o r t o f female t e r r i t o r y i a l i t y i n Marmota f l a v i v e n t r i s . Armitage ( 1 9 6 2 ) s t a t e d t h a t f e m ales i n o t h e r p o p u l a t i o n s appear t o have a r e a s o f domin-ance o r "dominions" (Brown 1 9 7 5 ) around t h e i r burrows. Sec-ond, Armitage ( 1 9 7 4 ) d e s c r i b e s the b a s i c s o c i a l u n i t i n marmot s o c i e t y as an a d u l t male and h i s harem. He ( 1 9 6 5 ) observed a dominance h i e r a r c h y w i t h i n the harem. Svendsen ( 1 9 7 4 ) r e p o r t s the females o f a harem p a r t i t i o n a male-defended t e r r i t o r i a l . At Watch Lake i n t e r a c t i o n s away from home burrows ( t e r r i t o r i e s ) were so r a r e t h e r e was no-evidence of a dominance h i e r a r c h y . Nor d i d the home ranges of t h e a d u l t females bear any apparent r e l a t i o n t o t e r r i t o r i e s o f the males. A s h i f t from t e r r i t o r i a l i t y t o a dominance h i e r a r c h y i s o f t e n a response t o changes i n d e n s i t y ( W i l s o n 1 9 7 5 ) . The Watch Lake c o l o n i e s s u p p o r t e d a h i g h e r d e n s i t y t h a n most o t h e r a r e a s , but the change i n s o c i a l o r g a n i z a t i o n i s not i n the p r e d i c t e d d i r e c t i o n : audominance h i e r a r c h y i s the t y p i - r c a l r esponse t o h i g h d e n s i t y , not t e r r i t o r i a l i t y . S o c i a l o r g a n i z a t i o n d i f f e r s among marmot s p e c i e s (Barash 1 9 4 7 b ) . The s p a c i n g system o f y e l l o w - b e l l i e d marmots i n Y e l l o w s t o n e Park and Col o r a d o i n d i c a t e s a g r e a t e r s o c i a l t o l e r a n c e t h a n t h a t at Watch Lake. I t i s c l o s e r t o the group 153 t e r r i t o r i a l i t y and harem m a t i n g system o f the a l p i n e and s u b a l p i n e s p e c i e s , Marmota olympus (Barash 1 9 7 3 b ) , and M. V a n c o u v e r e n s i s (Heard 1 9 7 7 ) . The t e r r i t o r i a l b e h a v i o u r o f the Watch Lake marmots i s more l i k e the s p a c i n g behav-i o u r o f woodchucks. Woodchucks have o v e r l a p p i n g home ra n g e s , but t h e y defend t h e i r burrows a g a i n s t a l l i n t r u d e r s ( H a m i l t o n 1 9 3 4 , G r i z z e l l 1 9 5 5 ) . D i f f e r e n c e s i n h a b i t a t and c o l o n y s i z e p a r a l l e l the d i f f e r e n c e s i n s p a c i n g systems. The Co l o r a d o marmots l i v e i n the a l p i n e and s u b a l p i n e l i k e the more s o c i a l s p e c i e s . The Watch Lake marmots, l i k e woodchucks, occupy low-e l e v a t i o n a g r i c u l t u r a l l a n d . C o l o n i e s o f t h e s u b a l p i n e a r e t y p i c a l l y s m a l l . P o p u l a t i o n s o f the Watch Lake marmots and woodchucks ( D a v i d , C h r i s t i a n and Bronson 1 9 6 4 ) may number w e l l over 1 0 0 . P o p u l a t i o n s i z e i s l i k e l y a f u n c t i o n o f ( 1 ) the a r e a o f the o p e n i n g the c o l o n y o c c u p i e s and ( 2 ) the p l a n t p r o d u c t i v i t y w i t h i n t h a t opening. C l e a r i n g l a n d f o r a g r i c u l t u r e may i n c r e a s e b o t h v a r i a b l e s . T e r r i t o r i a l i t y o f female woodchucks and y e l l o w - b e l l i e d marmots at Watch Lake may be an a d a p t a t i o n t o l a r g e p o p u l a -t i o n s i z e where i n d i v i d u a l s are not c l o s e l y r e l a t e d . T e r -r i t o r i a l b e h a v i o u r o f females may p r o t e c t o f f s p r i n g from a t -t a c k s by o t h e r a d u l t s . I n the s m a l l c o l o n i e s o f more c l o s e l y r e l a t e d i n d i v i d u a l s t y p i c a l o f :high e l e v a t i o n marmots o f a l l n e a r c t i c s p e c i e s , k i n s e l e c t i o n s h o u l d i n h i b i t k i l l i n g j u v e -n i l e s . C o n s e q u e n t l y t e r r i t o r i a l b e h a v i o u r o f a d u l t females s h o u l d have l e s s s e l e c t i v e v a l u e . 154 The h y p o t h e s i s t h a t female t e r r i t o r i a l i t y i s an adap-t a t i o n t o l a r g e p o p u l a t i o n s i z e has two t e s t i m p l i c a t i o n s . F i r s t , a d u l t s s h o u l d o c c a s i o n a l l y a t t a c k or k i l l j u v e n i l e s i n t h e Watch Lake p o p u l a t i o n s . S e c o n d l y , females s h o u l d t o l e r a t e c l o s e l y r e l a t e d i n d i v i d u a l s on t h e i r t e r r i t o r i e s more th a n o t h e r c o n s p e c i f i c s . I found no e v i d e n c e t o sup-p o r t the f i r s t a s s u m p t i o n . A l t h o u g h a d u l t s chased j u v e n i l e s , I saw none a t t a c k or k i l l them. Sherman ( 1 9 7 6 ) found t h a t those ground s q u i r r e l s most l i k e l y t o k i l l young were a d u l t females who had not. borne young or who had l o s t t h e i r l i t t e r . These i n d i v i d u a l s were r a r e i n the c o l o n i e s I o b s e r v e d . The second p r e d i c t i o n i s s u p p o r t e d by o b s e r v a t i o n s a t Watch Lake. One b r e e d i n g female t o l e r a t e d her d a u g h t e r s on her t e r r i t o r y , a l t h o u g h she was c l e a r l y dominant t o them. At l e a s t two groups of s i s t e r s shared t e r r i t o r i e s . The use of space of t h e s e k i n groups resembled t h a t of female y e l l o w -b e l l i e d marmots i n C o l o r a d o and Wyoming. 155 LIFE HISTORY TACTICS Comparison o f Demographic and R e p r o d u c t i v e " Parameters With Other Y e l l o w - b e l l i e d Marmot P o p u l a t i o n s Annual C y c l e . The most e x t e n s i v e l y s t u d i e d y e l l o w -b e l l i e d marmot p o p u l a t i o n s a r e those i n t h e s u b a l p i n e E a s t R i v e r V a l l e y , near G o t h i c , C o l o r a d o . The a c t i v e season of marmots at Watch Lake i s o f s i m i l a r l e n g t h but e a r l i e r i n the year t h a n t h a t i n the E a s t R i v e r V a l l e y . Annual events a t Watch Lake o c c u r 24 t o 27 days e a r l i e r w i t h the e x c e p t i o n o f the d a t e s o f the f i r s t emergence from.:.hibernation and the f i r s t weaned l i t t e r ( Table X L V I I I ) . Marmots i n t h e E a s t R i v e r V a l l e y l i k e l y emerge e a r l i e r from h i b e r n a t i o n t h a n t h e i r f i r s t r e c o r d e d s i g h t i n g May 8 . The time between May 8 and the emergence of the f i r s t l i t t e r does not a l l o w s u f f i -c i e n t time f o r a 32 days g e s t a t i o n and a 19 t o 23 day l a c t a -t i o n (Armitage p e r s o n a l communication). Mean and modal d a t e s of l i t t e r emergence may be the most r e l i a b l e i n d i c e s o f the a n n u a l c y c l e . Both are 26 days e a r l i e r at Watch Lake. L i t t e r s o f a d u l t s a t Watch Lake emerge more s y n c h r o n -o u s l y t h a n t h o s e from p o p u l a t i o n s i n the E a s t R i v e r V a l l e y (where o n l y a d u l t s b r e e d ) . At Watch Lake 12 l i t t e r s emerged over 18 days i n 1 9 7 4 ; 9 emerged over 13 days i n 1 9 7 5 - I n C o l o r a d o , a s i m i l a r number of l i t t e r s can emerge over a t h r e e to f i v e week p e r i o d (Armitage et a l . 1 9 7 6 ) . I est^:.. imated the v a r i a n c e o f emergence d a t e s i n the C o l o r a d o pop-u l a t i o n from grouped d a t a p r e s e n t e d by A r m i t a g e e t a l . ( 1 9 7 6 , Table 6 ) . I t i s s i g n i f i c a n t l y l a r g e r t h a n the Watch 1 5 6 Table XLVIli. Comparison of a c t i v e season between Watch Lake, B.C. and East R i v e r , Colorado. Event e a r l i e s t , emergence from h i b e r n a t i o n peak of emergence from h i b e r n a t i o n e a r l i e s t emergence of a l i t t e r modal emergence date of l i t t e r s median emergence date of l i t t e r s mean emergence date of l i t t e r s l a s t a c t i v e marmot Watch East Approx. Lake R i v e r d i f f . Source (days) A p r i l 1 May 8 37 1 A p r i l 16 May 10 24 1 June 6 mid-June 11 2 June 6-9 J u l y 1-7' 26 2 June 9 J u l y 1-7 24. 5 2 June l l 3 J u l y 7 26 c a l c u l a t e d from 2 Sept. 5 e a r l y 27 2 Op't. ;Armitage, pers. comm. Armitage et a l . 1976 'excludes l i t t e r s of y e a r l i n g s . Y e a r l i n g s do not breed i n the East R i v e r p o p u l a t i o n . 157 Lake v a r i a n c e of l i t t e r s of a d u l t s (P = 2 . 7 1 4 , p < .02). T h i s i s a c o n s e r v a t i v e t e s t as t h e C o l o r a d o s t a t i s t i c under-e s t i m a t e s the p a r a m e t r i c v a r i a n c e . r~j r. " i c R e p r o d u c t i o n . B r e e d i n g s u c c e s s i n the Watch Lake pop-u l a t i o n s i s c o n s i d e r a b l y g r e a t e r t h a n i n o t h e r a r e a s . (Table X L I X ) . Armitage and h i s s t u d e n t s r e c o r d e d no b r e e d i n g y e a r -l i n g s d u r i n g 17 y e a r s of s t u d y . At Watch Lake more t h a n t h r e e t i m e s as many two year o l d s and almost t w i c e as many a d u l t s o f a l l ages had l i t t e r s compared t o o t h e r p o p u l a t i o n s . The E a s t R i v e r V a l l e y p o p u l a t i o n s d i f f e r e d from th o s e a t Watch Lake both i n the amount o f energy a l l o c a t e d t o r e -p r o d u c t i o n and i n the p a r t i t i o n i n g of t h a t energy. The E a s t R i v e r l i t t e r s were much s m a l l e r (Table L) and l e s s v a r i a b l e i n s i z e (P = 1 . 6 9 3 , p = .049). The sex r a t i o o f weaned j u v e -n i l e s d i d not d i f f e r between the p o p u l a t i o n s . I n t h e E a s t R i v e r V a l l e y , both weaned young and t h e i r mothers were heav-i e r . The g r e a t e r weight of the j u v e n i l e s cannot be accounted f o r by the s m a l l e r l i t t e r s i z e . I n the r e g r e s s i o n s o f j u v e -n i l e weight on l i t t e r s i z e i n the Watch Lake p o p u l a t i o n s ( F i g . 7 and 8), the upper 99% p r e d i c t i o n l i m i t s f o r a l i t t e r o f 4.20 ( C o l o r a d o mean) and an assumed sample s i z e of 59(247/4.20) a r e .562 k g , f o r males and .444 kg f o r f e m a l e s . The East R i v e r j u v e n i l e s exceed t h e s e w e i g h t s . The females a l s o exceed the 99-9% p r e d i c t i o n l i m i t , .465 kg. The r a t i o o f t h e weight of a j u v e n i l e t o i t s mother's weight i s t h e same i n both a r e a s . The r e p r o d u c t i v e e f f o r t o f a l l the Watch Lake females 158 Table XLIX. Comparison of p r o p o r t i o n of females w i t h weaned l i t t e r s i n y e l l o w - b e l l i e d marmot populations i n s i x areas. Sample s i z e i n parentheses. Study area Length Y e a r l i n g s Two year Three 'of olds years study and (yr) o l d e r A l l Study a d u l t s Yellowstone Park, Wyo. 4 East R i v e r V a l l e y , C o l a 11 Rocky Mt. N a t l . Park, Colorado 1 North Pole B a s i n , Colo. 1 .0(8) 0.0(4) 1 0.75(4) 2 0.43(44) Armitage 1962, 1965* 0.0(~73) 0.26(23) 0.0(3) 0.0 0.42(185)Armitage and ^ Downhower 1974 0.60(5) Barash 1973a 0.33(3) 0.70(10) 0.62(13) Andersen^et a l . 1976° Sagehen Creek, C a l i f . 2 Watch Lake, B.C. 2 0.32(25) 6' 7 0.92Q3) 7 - Nee 1969 0.08(38) 0.78(9) 1.00(7) 0.92(26) t h i s study Two and three year o l d females. p Females four years and o l d e r . 3Armitage 1962, Table 1, f o r 1955 to 1957 and Armitage 1965 f o r 1961. Vdult r a t e c a l c u l a t e d from Armitage and Downhower 1974 Table 3-^ C a l c u l a t e d from Table 2. ^One and two year o l d females. ^ P r o p o r t i o n of females pregnant, not p r o p o r t i o n w i t h weaned l i t t e r s . 159 Table L. Comparison of rep r o d u c t i v e v a r i a b l e B.C. p o p u l a t i o n ! w i t h those i n the East R i v e r V a l l e y , Colorado. Mean-standard error(sample s i z e ) . Watch Lake East R i v e r Source L i t t e r s i z e J u v e n i l e M w e i g h t s ( k g ) p L i t t e r weight(kg) 19 i . i f 2 1 ( 2 4 ) 1 . 07^.379(27)2 357-.015(52) 332^.012(49) 2.20±.117 ( l 6 ) 1 2 . 1 0 i . l 2 7 ( l 8 ) 2 Sex r a t i o (M:F) Breeding female weight(kg) 53:4:46.6(365) 1.66±.044 ( l 6 ) 1 1.54i.074(19) 2 J u v e n i l e weight/adult Femaler weight M . 2 2 F . 2 0 T o t a l . 2 2 5 i . 0 l 6 ( 1 2 ) ] R e p r o d u c t i v e ! . 2 6 ± . 0 7 ^ ( 1 2 ) 1 e f f o r t i . 3 0 i . 0 7 6 ( 1 3 ) 2 4.15i.l9(65) 3 5.06 < . 001 5.056<.001 .59 2.06l<.05 .50 2.141<.05 2.28 .217>.50 • 3'82>.50 :53.0(247) G=2.46 <.20 2v52 4.724<. 001 ,24 ,20 927 1.356=.202 1.453=.172 Armitage and Downhower 1974 Armitage pers.comm. Armitage and Downhower 1974 Armitage Downhower and Svendsen 1976 5 2Known a d u l t s ( a t l e a s t two years o l d ) o n l y -,A11 breeding females ^Excludes s t a t e l i t e c o l o n i e s . Mean i n c l u d i n g s a t e l l i t e s i s 4 . 2 0 ( 7 8 ) ^ 2 . 2 8 k g = 4 . 2 0 ( . 4 7 x . 5 9 k g + . 5 3 x . 5 0 k g ) ^ 2 . 5 2 k g = ( . 1 8 6 x 2 . 2 8 kg + . 8 l 4 x 2 . 8 k g ) - ( . 0 1 2 k g / d a y x 2 0 d a y s ) where 2 . 2 8=weight of 2 year o l d s i n June, 2 . 8=weight of a d u l t s over 2 years i n June, . l 8 6 = p r o p o r t i o n of breeding females t h a t are 2 years o l d , . 8 l 4 = p r o p o r t i o n of breeding females over 2 y e a r s , .0 1 2=weight ggain per day, 20=days to May 2 6 , comparable to A p r i l 3 0 at Watch Lake. R a t i o of mean male and female j u v e n i l e weights to mean a d u l t -female weight. Reproductive e f f o r t i n Colorado 160 exceeded t h a t of the East R i v e r mean. I f t h e East R i v e r mean r e p r o d u c t i v e e f f o r t i s t r e a t e d as a sample o f one, i t does not d i f f e r from t h e Watch Lake mean (p = . 1 7 ) . However i t may be more a p p r o p r i a t e t o t r e a t i t as a parameter as the East R i v e r sample s i z e s a re l a r g e r e l a t i v e t o tho s e at Watch Lake. I f t h i s i s done, p < . 0 0 1 . To summarize, females a t Watch Lake b e g i n b r e e d i n g a t a younger age t h a n i n o t h e r p o p u l a t i o n s . A h i g h e r p r o p o r -t i o n produce l i t t e r s . Weights o f l i t t e r s do not v a r y be-tween Watch Lake and the East R i v e r V a l l e y . Females at Watch Lake produce l a r g e l i t t e r s o f s m a l l young; t h o s e i n the East R i v e r V a l l e y produce s m a l l l i t t e r s of l a r g e young. Because Watch Lake females weigh l e s s , t h e i r r e p r o d u c t i v e e f f o r t i s g r e a t e r . M o r t a l i t y Rates. Annual j u v e n i l e m o r t a l i t y i n the East R i v e r V a l l e y can be c a l c u l a t e d from two s o u r c e s . ( 1 ) From Armitage and Downhowerv( 1 9 7 4), Table 1 ) , a n n u a l : m o r t a l i t y over s e v e r a l y e a r s i s 53-^% (n = 247). T h i s does not d i f f e r s i g n i f i c a n t l y from j u v e n i l e m o r t a l i t y a t Watch Lake ( x 2 = 2 . 2 3 0 , p.= . 1 3 1 ) . ( 2 ) A m o r t a l i t y r a t e f o r 1 9 6 2 t o 1 9 7 2 c o h o r t s can be c a l c u l a t e d from d a t a g i v e n by Armitage et a l . ( 1 9 7 6 , Table 6 ) . O b s e r v a t i o n s are d i v i d e d i n t o 5 p e r i o d s . Annual m o r t a l i t y , 5 E IS. i = l 1 161 where, = number o f j u v e n i l e s r e c a p t u r e d as y e a r l i n g s , 1. = number o f l i t t e r s and s. = mean l i t t e r s i z e . T h i s 1 l g i v e s 5 2 . 1 % m o r t a l i t y (n = 2 5 9 ) . T h i s r a t e may d i f f e r from j u v e n i l e m o r t a l i t y a t Watch Lake (G = 3 . 0 1 2 , p = . 0 7 9 ) . Annual m o r t a l i t y of j u v e n i l e f e m a l e s , . 5 3 1 (Armitage and Downhower 1 9 7 4 ) , was l i k e t h a t o f Watch Lake females (Table XII'). However, j u v e n i l e males i n t h e E a s t R i v e r V a l l e y s u r v i v e d as w e l l as t h e i r s i s t e r s and b e t t e r t h a n the Watch Lake males. Of 116 young males t r a p p e d i n c c o l o n i e s , Armitage and Downhower r e c a p t u r e d 5.4 as y e a r l i n g s ( 5 3 - 4 % m o r t a l i t y ) . T h i s r a t e i s s i g n i f i c a n t l y l o wer t h a n t h a t o f 4 6 j u v e n i l e males marked at the Home and Old C o l o n i e s ( 7 1 . 7 % m o r t a l i t y , X 2 = 4 . 5 4 4 , p < " , : 0 5 ) . Armitage et a l . ( 1 9 7 6 , Table 6) r e p o r t e d o v e r w i n t e r m o r t a l i t y o f j u v e n i l e s f o r t h e E a s t R i v e r p o p u l a t i o n s , 1 9 6 2 t o 1 9 7 2 . The r a t e s can be compared w i t h the Watch Lake r a t e i n two ways. ( 1 ) The number of young t h a t s u r v i v e and the number t h a t d i e can be summed over a l l y e a r s and compared to 2 the Watch Lake numbers i n a t e s t o f independence (X - or G - t e s t ) . ( 2 ) Each y e a r ' s m o r t a l i t y r a t e can be t r e a t e d as a s i n g l e o b s e r v a t i o n , t h e d a t a t r a n s f o r m e d w i t h an a r c s i n t r a n s f o r m a t i o n , and the mean compared t o the Watch Lake v a l u e i n a t - t e s t . The l a t t e r method, u n l i k e the f o r m e r , a c c o u n t s f o r v a r i a n c e among y e a r s , but t r e a t s each y e a r ' s mean the same r e g a r d l e s s o f the sample s i z e on which i t was based. N e i t h e r method r e v e a l s s i g n i f i c a n t d i f f e r e n c e s (Table L I ) . Summer m o r t a l i t y , M Q f o r the C o l o r a d o p o p u l a t i o n s can 162 Table L I , Comparison of overwinter m o r t a l i t y of j u v e n i l e s between Watch Lake, B.C. and East R i v e r V a l l e y , Colo, p o p u l a t i o n s . Sample s i z e s i n parentheses. Watch Lake East R i v e r Test s t a t i s t i c p O v e r a l l m o r t a l i t y r a t e 1 .375(40) .508(252) G=2.468 =.112 Mean m o r t a l i t y r a t e 2 .375(1) . .475(7) t 3 = l . l l 6 >'.20 Rate based on observations from a l l years combined. See t e x t . 2Sample s i z e s are numbers of j u v e n i l e s . Mean m o r t a l i t y r a t e from years where number of j u v e n i l e s exceeded ,20. See t e x t . Sample s i z e s are numbers of years. Comparison of a s i n g l e observation w i t h a sample (Sokal and Rohlf-1969, p.224) 163 be c a l c u l a t e d from Armitage et a l . (1976, Table 6) by M-s = 1 -(' E l . s . where j j . = number a l i v e b e f o r e h i b e r n a t i o n , 1^ = number o f l i t t e r s , and s^ = mean l i t t e r s i z e . Summer m o r t a l i t y i s 2.7%. T h i s i s c o n s i d e r a b l y lower than the e s t i m a t e d 39-2% m o r t a l i t y a t Watch Lake. The d i f f e r e n c e may be g r e a t e r as Watch Lake f i g u r e may u n d e r e s t i m a t e summer l o s s . A j u v e n i l e i s c o n s i d e r e d a l i v e a t h i b e r n a t i o n i f i t was seen August 1 or l a t e r . However h i b e r n a t i o n does not l i k e l y b e g i n u n t i l l a t e August o r e a r l y September. Armitage and Bowr.hcwer "O 974) p r e s e n t e d m o r t a l i t y r a t e s o f o n l y female y e a r l i n g s : a n d a d u l t s I n the E a s t R i v e r V a l l e y p o p u l a t i o n s . , Y e a r l i n g female m o r t a l i t y , 5^ .2%, i s t w i c e the Watch Lake r a t e . . A d u l t female' m o r t a l i t y , 25%, i s the same or lower than a t Watch l a k e , . I n summary, j u v e n i l e m o r t a l i t y d u r i n g the a c t i v e season was g r e a t e r at Watch Lake than i n the E a s t R i v e r V a l l e y . J u v e n i l e males s u f f e r e d g r e a t e r m o r t a l i t y than t h e i r C o l o r a d o c o u n t e r p a r t s . M o r t a l i t y o f j u v e n i l e and, p o s s i b l y , a d u l t f e -males d i d not d i f f e r between the p o p u l a t i o n s . M o r t a l i t y o f y e a r l i n g females was g r e a t e r i n C o l o r a d o . Sources o f m o r t a l i t y . The s o u r c e s o f m o r t a l i t y d i f f e r e d c o n s i d e r a b l y between the Watch Lake and E a s t R i v e r V a l l e y p o p u l a t i o n s . Most m o r t a l i t y i n the E a s t R i v e r p o p u l a t i o n s o c c u r r e d d u r i n g h i b e r n a t i o n . N i n e t y - f i v e p e r c e n t o f j u v e n i l e 164 m o r t a l i t y o c c u r r e d o v e r w i n t e r . " V i r t u a l l y a l l l o s s e s of a d u l t s " o c c u r r e d between l a t e August o r September and l a t e May or e a r l y June (Armitage and Downhower 1974). O v e r w i n t e r m o r t a l i t y was r e l a t i v e l y l e s s i m p o r t a n t a t Watch Lake. •.; There a t l e a s t 62% o f j u v e n i l e m o r t a l i t y o c c u r r e d by August. Only 56% o f a d u l t and y e a r l i n g m o r t a l i t y o c c u r r e d between J u l y 1 ( w e l l b e f o r e h i b e r n a t i o n ) and e a r l y May. The major sources o f m o r t a l i t y at Watch Lake, d i s e a s e , h u n t i n g , and coyote p r e d a t i o n , were not e v i d e n t i n the. E a s t R i v e r V a l l e y . Armitage and Downhower (1974) found no s i c k a n i m a l s d u r i n g t h e i r 11 year s t u d y . Hunters k i l l e d o n l y 8 marmots d u r i n g the same p e r i o d . They saw co y o t e s o n l y 3 -•-ti m e s i n 11 years..'.and l o s t no c o l o n i a l marmots t o p r e d a t o r s . Golden e a g l e s t o o k d i s p e r s i n g . y e a r l i n g s (G1. Svendsen, p e r s o n -n e l communication). By c o n t r a s t , at l e a s t 14% o f a d u l t and y e a r l i n g m o r t a l i t y at Watch Lake was caused by d i s e a s e , a t l e a s t 10% by h u n t i n g (Table X X I ) . As h u n t i n g at the c o l o n i e s on which the m o r t a l i t y e s t i m a t e s a re based was almost e l i m i n -a t e d d u r i n g the s t u d y , the u s u a i r . m o r t a l i t y from t h i s . - s o u r c e was u n d e r e s t i m a t e d . Coyotes hunted the Watch Lake c o l o n i e s and were o c c a s i o n a l l y seen k i l l i n g marmots. T h e i r impact i s unknown but p o t e n t i a l y g r e a t . Coyote p r e d a t i o n may e x p l a i n t h r e e d i f f e r e n c e s between the E a s t R i v e r V a l l e y and Watch Lake p o p u l a t i o n s . F i r s t , the h i g h a c t i v e season m o r t a l i t y o f a l l age c l a s s e s a t Watch Lake may r e s u l t from coyote p r e d a t i o n . Second, i f the behav-i o u r o f males makes them more s u s c e p t i b l e t o p r e d a t i o n (see 165' R e s u l t s : Sources of L o s s ) , c oyote p r e d a t i o n can account f o r the s i g n i f i c a n t l y h i g h e r : " m o r t a l i t y o f j u v e n i l e males a t Watch Lake t h a n j u v e n i l e s i n t h e E a s t R i v e r V a l l e y . T h i r d , c o yote p r e d a t i o n may s e l e c t f o r the h i g h synchrony of l i t t e r emergence d a t e s compared t o the C o l o r a d o p o p u l a t i o n s . These d i f f e r e n c e s suggest t h a t coyote p r e d a t i o n has a major e f f e c t on the Watch Lake p o p u l a t i o n s . D e n s i t y and r a t e o f i n c r e a s e . The d e n s i t y o f a d u l t s and y e a r l i n g s at Watch Lake was h i g h r e l a t i v e t o most o t h e r pop-u l a t i o n s b o t h i n terms of numbers per h e c t a r e and numbers per burrow (Table L I I ) . The r a t e o f i n c r e a s e a t Watch Lake, r g = . 2 7 , was h i g h e r t h a n i n the E a s t R i v e r V a l l e y . There, R Q = 0 . 8 0 8 (Armitage adn Downhower 1 9 7 4 ) . T h i s i s e q u i v a l e n t t o an r o f - . 0 5 3 -( C a l c u l a t i o n s a r e as g i v e n i n R e s u l t s : P o p u l a t i o n D e n s i t y and Rate o f I n c r e a s e . ) .: ..•> D i f f e r e n c e s i n s u r v i v o r s h i p are not s u f f i c i e n t to ex-p l a i n the d i f f e r e n c e i n r a t e s o f i n c r e a s e . The B. C. pop-u l a t i o n s have somewhat h i g h e r s u r v i v o r s h i p t o ages 2 t o 4 (Armitage and Downhower 1 9 7 4 , Table 4 ) . But the d i f f e r e n c e s a r e m i n i m a l at the ages o f h i g h e s t f e c u n d i t y i n C o l o r a d o , 5 and 4 . I t i s i n the f e c u n d i t y t a b l e t h a t t h e g r e a t e s t d i f -f e r e n c e s o c c u r . At every age f e c u n d i t y i s g r e a t e r i n the Watch Lake p o p u l a t i o n s . The E a s t R i v e r marmots do not p r o -duce young u n t i l . a g e two. Fewer a d u l t s b r e e d . Those t h a t do produce s m a l l e r l i t t e r s . 166 Table i l l . Comparison of marmot d e n s i t y at Watch Lake w i t h other areas Number/ Number/area Number/ Lo c a t i o n Number of adu l t s colony of burrow Source and y e a r l i n g s area(ha) opening Home Colony 35 9.21 5.47 1. 30 t h i s study Yellowstone N a t ' l Park 19 2.76 - • 0. 311- Armitage 1962 East R i v e r V a l l e y , C o l o . 3.161 - 0.131 0. 266 2 Svendsen 1974 North Pole B a s i n , Colo. 20 3 2.863 - - Andersen et a l . 1976 Rocky Mt. Natl P a r k , Colo 8 16.00 - - Barash 1973a ^Mean.resident p o p u l a t i o n of 7 c o l o n i e s . iMean number of residents/mean number of burrows at 7 c o l o n i e s . ^Number of ad u l t s only. The number of a d u l t s / c o l o n y area at the Home Colony was 4.47/ha i n May 1976 167 L i f e H i s t o r y S t r a t e g i e s o f Marmots at Watch Lake, B r i t i s h Columbia and the East R i v e r V a l l e y , C o l o r a d o The r e p r o d u c t i v e t r a i t s of the Watch Lake p o p u l a t i o n s d i f f e r e d from most o t h e r p o p u l a t i o n s . Females began b r e e d -i n g younger, bred more o f t e n , bore l a r g e r l i t t e r s of s m a l l e r young, weighed l e s s as a d u l t s , and p a r t i t i o n e d r e l a t i v e l y more energy i n t o r e p r o d u c t i o n . Not a l l o f t h e s e a t t r i b u t e s need r e f l e c t a d i f f e r e n t l i f e h i s t o r y s t r a t e g y . The Watch Lake c o l o n i e s had a h i g h e r d e n s i t y and a h i g h e r r a t e of i n -c r e a s e t h a n most p o p u l a t i o n s . The f r e q u e n c y o f b r e e d i n g and p o s s i b l y age o f f i r s t r e p r o d u c t i o n are l i k e l y a r t i f a c t s of .a h i g h r a t e o f i n c r e a s e r a t h e r t h a n a r e s u l t of d i f f e r e n t s e l -e c t i v e p r e s s u r e s . One s h o u l d f i r s t c o n s i d e r o t h e r p r o x i m a t e f a c t o r s t h a t might cause the observed d i f f e r e n c e s . Perhaps f o o d a v a i l -a b i l i t y d i f f e r s at Watch Lake. High p l a n t p r o d u c t i v i t y might lower the age o f s e x u a l m a t u r i t y and i n c r e a s e l i t t e r s i z e , the weight o f young, a d u l t w e i g h t , and r e p r o d u c t i v e e f f o r t . However t h e r e i s no c o n s i s t e n t d i r e c t i o n i n the d i f f e r e n c e s between p o p u l a t i o n s . The age o f s e x u a l m a t u r i t y , l i t t e r s i z e , and r e p r o d u c t i v e e f f o r t suggest Watch Lake has a t y p i -c a l l y h i g h food a v a i l a b i l i t y . Whereas the w e i g h t s of b o t h young and a d u l t suggest p l a n t p r o d u c t i v i t y i s low. I f the s e t of r e p r o d u c t i v e t r a i t s at Watch Lake do r e f l e c t a d i f f e r e n t l i f e h i s t o r y s t r a t e g y , what are the s e l -e c t i v e f o r c e s d e t e r m i n i n g them? Two f a c t o r s seem i m p o r t a n t . F i r s t , y e l l o w - b e l l i e d marmot numbers have I n c r e a s e d g r e a t l y d u r i n g t h e l a s t few decades. T h e i r h i s t o r y has been one of 168 c o l o n i z a t i o n . New h a b i t a t has been and c o n t i n u e s t o be c r e a t e d by c l e a r i n g l a n d and by v a c a t i n g s m a l l r a n c h e s . The t h r e e l a r g e c o l o n i e s I s t u d i e d were a l l p a r t of one r a n c h . Each c o l o n y o c c u p i e d o n l y a f r a c t i o n of the a r e a a v a i l a b l e t o i t . The e n t i r e r a n c h i n c l u d e d about 15 such o l d home-,... ste a d s t h a t had been v a c a t e d by s m a l l l a n d h o l d e r s and c o l o n -i z e d my marmots and/or Columbian ground s q u i r r e l s . Competi-t i o n f o r r e s o u r c e s has been r e l a t i v e l y low. C o n t r a s t t h i s w i t h the s t a b l e a l p i n e and s u b a l p i n e environment o f C o l o r a d o . L i k e l y a l l a v a i l a b l e h a b i t a t i s o c c u p i e d and no new h a b i t a t i s c r e a t e d . S e l e c t i o n i n Co l o r a d o s h o u l d f a v o u r c o m p e t i t i v e a b i l i t y t h a t a l l o w s an i n d i v i d u a l t o become a r e s i d e n t i n an e s t a b l i s h e d and s t a b l e c o l o n y . An i m p o r t a n t d e t e r m i n a n t o f c o m p e t i t i v e a b i l i t y i s body s i z e . At Watch Lake, male y e a r -l i n g s t h a t e s t a b l i s h e d themselves as r e s i d e n t s i n t h e i r n a t a l c o l o n y were h e a v i e r t h a n e m i g r a n t s . I n Y e l l o w s t o n e Park, the o l d e s t , and l i k e l y the l a r g e s t , females topped the dominance h i e r a r c h y and r a i s e d l i t t e r s (Armitage 1965). Both weight and l e n g t h are s i g n i f i c a n t f a c t o r s i n d e t e r m i n i n g the outcome o f p a i r e d e n c o u n t e r s o f woodchucks (Bronson 1964). I n C o l o r a d o s e l e c t i o n s h o u l d f a v o u r l a r g e , body s i z e . The most f i t females i n C o l o r a d o s h o u l d produce l a r g e heavy young a t the c o s t o f l i t t e r s i z e . I f r e p r o d u c t i v e s u c -cess depends on s o c i a l s t a t u s and body s i z e , t h e n females s h o u l d a l l o c a t e l e s s energy t o r e p r o d u c t i o n and more t o t h e i r own growth t h a n females at Watch Lake. S i m i l a r l y the age o f 169 s e x u a l m a t u r a t i o n s h o u l d be d e l a y e d to i n c r e a s e growth. A second major d i f f e r e n c e a t Watch Lake i s the source and r a t e o f m o r t a l i t y . The m o r t a l i t y r a t e s observed i n t h i s s t udy s h o u l d u n d e r e s t i m a t e a c t u a l m o r t a l i t y because of r e -duced h u n t e r k i l l . As a consequence, a n n u a l m o r t a l i t y o f a l l age c l a s s e s i s l i k e l y g r e a t e r at Watch Lake t h a n i n the E a s t R i v e r V a l l e y . C e r t a i n l y a c t i v e season m o r t a l i t y was g r e a t e r at Watch Lake as v i r t u a l l y a l l l o s s i n C o l o r a d o was d u r i n g h i b e r n a t i o n . T h i s a l o n e s h o u l d s e l e c t f o r l a r g e r body s i z e i n C o l o r a d o . As o v e r w i n t e r s u r v i v a l o f j u v e n i l e s , a t l e a s t , i s a f f e c t e d by t h e i r p r e h i b e r n a t i o n w e i g h t s (Table XVI) the c o s t o f p r o d u c i n g l a r g e l i t t e r s o f c o n s e q u e n t l y s m a l l young i s g r e a t e r i n C o l o r a d o . I f t h e Watch Lake p o p u l a t i o n s do s u f f e r g r e a t e r a n n u a l m o r t a l i t y , s e l e c t i o n s h o u l d a c t i n a d i r e c t i o n s i m i l a r t o t h a t i n c o l o n i z i n g p o p u l a t i o n s . H i g h e r m o r t a l i t y r educes the number of c o n s p e c i f i c s competing f o r r e s o u r c e s . Reduced c o m p e t i t i o n s h o u l d f a v o u r l a r g e l i t t e r s , r a t h e r t h a n l a r g e young. I f r e p r o d u c t i o n reduces a female's p r o b a b i l i t y o f s u r v i v a l , t h e n g r e a t e r w e i g h t - i n d e p e n d e n t m o r t a l i t y s h o u l d f a v o u r a lower age of f i r s t r e p r o d u c t i o n and h i g h e r r e p r o -d u c t i v e e f f o r t . The c o s t o f r e d u c i n g one's p r o b a b i l i t y o f s u r v i v a l t h r o u g h h i g h r e p r o d u c t i v e output i s l e s s i f one has a r e l a t i v e l y low p r o b a b i l i t y o f s u r v i v i n g a n o t h e r y e a r i n d e p e n -dent of whether one r e p r o d u c e s or n o t . The observed d i f f e r e n c e s between the p o p u l a t i o n s a t Watch Lake and i n o t h e r a r e a s , p a r t i c u l a r l y t h e East R i v e r 170 V a l l e y , C o l o r a d o , seem c l a s s i c examples o f s i m p l e r - and K-s e l e c t i o n . The Watch Lake p o p u l a t i o n s a r e and have been c o l o n i z i n g and expanding and may be s u b j e c t t o g r e a t e r mor-t a l i t y . These f a c t o r s reduce c o m p e t i t i o n f o r r e s o u r c e s . S e l e c t i o n s h o u l d f a v o u r the observed t r a i t s at Watch Lake: a lower age o f f i r s t r e p r o d u c t i o n , l a r g e r l i t t e r s o f s m a l l e r young, r e l a t i v e l y more energy expended on r e p r o d u c t i o n , and a s m a l l e r a d u l t s i z e . 171 POPULATION REGULATION The marmot c o l o n i e s at Watch Lake were not s u i t a b l e f o r t e s t i n g hypotheses of p o p u l a t i o n r e g u l a t i o n as a l l had h i g h r a t e s o f i n c r e a s e . N e v e r t h e l e s s from an u n d e r s t a n d i n g o f t h e s o c i a l o r g a n i z a t i o n and knowledge of the magnitude and cause o f some or a l l o f t h e demographic p r o c e s s e s , one can i s o l a t e t h o s e v a r i a b l e s t h a t s h o u l d be most s e n s i t i v e t o i n c r e a s e d d e n s i t y . Prom the s e one can g e n e r a t e t e s t a b l e hypotheses f o r mechanisms of p o p u l a t i o n c o n t r o l The r a t e o f i n c r e a s e i s d e t e r m i n e d by t h e r a t e s o f f e c u n d i t y and s u r v i v a l w i t h i n the p o p u l a t i o n . I c o n s i d e r t h e s e r a t e s as s i x v a r i a b l e s : (1) age o f f i r s t r e p r o d u c t i o n , ( 2 ) p r o p o r t i o n o f females t h a t r e p r o d u c e , ( 3 ) l i t t e r s i z e : and sex r a t i o , ( 4 ) j u v e n i l e m o r t a l i t y , ( 5 ) y e a r l i n g and a d u l t m o r t a l i t y , and ( 6 ) e m i g r a t i o n . I i g n o r e i m m i g r a t i o n as r e d u c i n g the observed r a t e s of i m m i g r a t i o n would be i n -s u f f i c i e n t t o reduce r to 0 . M o r t a l i t y and e m i g r a t i o n would have t o i n c r e a s e • g r e a t l y t o s t a b i l i z e numbers. Female m o r t a l i t y from weaning u n t i l June of the second a c t i v e season must i n c r e a s e from th e e s t i m a t e d 60% to 85% i n o r d e r t o reduce r t o 0 (see Table X X I X ) . A d u l t and y e a r l i n g female l o s s would have t o i n c r e a s e from 30% a n n u a l l y t o 55%. I f o n l y y e a r l i n g female l o s s changed, i t would have to i n c r e a s e to 72% a n n u a l l y . H u n t e r : . k i l l would c e r t a i n l y have i n c r e a s e d a f t e r the study ended. I f e f f o r t was h i g h i n A p r i l and May, i t i s n?: p o s s i b l e h u n t e r s c o u l d k i l l t he 25% o f the a d u l t s and "... 172' y e a r l i n g s needed t o s t a b i l i z e numbers. I t seems u n l i k e l y t h a t m o r t a l i t y from o t h e r s o u r c e s would i n c r e a s e by the n e c e s s a r y p r o p o r t i o n s . V a r i a t i o n o f a d u l t and y e a r l i n g m o r t a l i t y between y e a r s was m i n i m a l (Table XV). I f the major source o f j u v e n i l e m o r t a l i t y was coyote p r e d a t i o n , t h e n m o r t a l i t y may have d e c r e a s e d when numbers i n c r e a s e d i n 1975, r a t h e r .'then i n c r e a s e d . Coyotes had been f r e q u e n t v i s i -t o r s t o a l l c o l o n i e s i n 1973 and 1974, but were not seen i n 1975. Changes i n the r a t e s o f r e p r o d u c t i o n or e m i g r a t i o n as numbers i n c r e a s e seem more l i k e l y . While m o r t a l i t y r a t e s o f females of a l l ages were s i m i l a r t o t h o s e o f females i n the E a s t R i v e r , C o l o r a d o p o p u l a t i o n s , r e p r o d u c t i o n and e m i g r a t i o n r a t e s a t Watch Lake d i f f e r e d from a l l o t h e r p o p u l a t i o n s . Two f a c t o r s t h a t might l i m i t r e p r o d u c t i o n are f o o d a v a i l a b i l i t y and s o c i a l i n t e r a c t i o n s . The o b s e r v a t i o n s a t Watch Lake sug-gest t h a t t h e remale's c o n d i t i o n i n A p r i l i s o f c r i t i c a l im-p o r t a n c e i n d e t e r m i n i n g the s i z e o f her l i t t e r . Presumably i f h er c o n d i t i o n i s poor enough she w i l l not breed a t a l l . However, i n a l l t h r e e l a r g e c o l o n i e s marmots used o n l y 12% t o 60% o f the a v a i l a b l e a r e a f o r f e e d i n g and o t h e r a c t i v i ^ : ' . t i e s ( T a ble I ) . P o p u l a t i o n s c o u l d e a s i l y double b e f o r e f o o d should:, l i m i t ' r e p r o d u c t i o n . A r e s o u r c e e q u a l i n importance t o f o o d f o r a b r e e d i n g female i s a burrow. As marmots dug new burrows at a r a t e much s l o w e r t h a n p o p u l a t i o n growth, burrows s h o u l d become l i m i t i n g b e f o r e food does. T e r r i t o r i a l d efense o f burrow 173 systems can p o t e n t i a l l y a l t e r t h r e e o f the v a r i a b l e s d e t e r -m i n i n g the r a t e o f i n c r e a s e : ,~.age,df:. f i r s t r e p r o d u c t i o n , the number o f b r e e d i n g f e m a l e s , and e m i g r a t i o n r a t e s . The p r e -sence o f a d u l t females a p p a r e n t l y a f f e c t s the r e p r o d u c t i v e s u ccess o f y e a r l i n g f e m a l e s . More y e a r l i n g s bred in'J t h e c o l o n i e s from which a d u l t females had been removed t h a n i n the c o n t r o l s (Table I V ) . As the r a t i o o f females/burrow i n c r e a s e s , some females may be f o r c e d i n t o s u b o p t i m a l burrows, i n t o s h a r i n g burrows w i t h o t h e r y e a r l i n g s and a d u l t s , o r i n t o c l o s e p r o x i m i t y w i t h o t h e r b r e e d i n g f e m a l e s . Armitage ( 1 9 6 5 ) d e s c r i b e d t h e e f f e c t o f a dominance h i e r a r c h y on b r e e d i n g s u c c e s s . I n t h e c o l o n y he o b s e r v e d , age, s o c i a l s t a t u s , and r e p r o d u c t i v e s u c c e s s were almost synonymous. Only t h e three^ most dominant f e m a l e s , those a t l e a s t f o u r y e a r s o l d , produced l i t t e r s . None o f t h e f o u r females whose home ranges o v e r l a p p e d t h a t o f t h e 5 year o l d female at the top o f the h i e r a r c h y f o r t h e f i r s t t h r e e weeks a f t e r emergence produced l i t t e r s . At l e a s t t h r e e o f the s u b o r d i n a t e s had c o p u l a t e d ; two appeared pregnant and gave b i r t h . They appeared r e l u c t a n t t o e n t e r t h e i r home b u r -rows when the dominant female was nearby. Armitage a t t r i -b utes t h e i r f a i l u r e t o produce weaned l i t t e r s t o t h e i r i n -a b i l i t y t o car e f o r t h e i r young p r o p e r l y . At Watch Lake t e r r i t o r i a l i t y o f a d u l t males appear t o cuase y e a r l i n g males t o e m i g r a t e . However, t h i s has l i t t l e e f f e c t on p o p u l a t i o n growth. The presence o f a d u l t females was not s u f f i c i e n t cause f o r y e a r l i n g female e m i g r a t i o n . 174 P o s s i b l y t h e d e n s i t y was too low. As t h e t e r r i t o r i e s o f .: a d u l t females encompass o n l y a s m a l l a r e a around t h e i r burr-row, y e a r l i n g females were a b l e t o occupy vacant burrows, or o c c a s i o n a l l y t o share one w i t h an a d u l t male. As d e n s i t y Increases and-, vacant burrows become more s c a r c e , t h e t e r r i -t o r i a l b e h a v i o u r o f a d u l t females may e x p e l y e a r l i n g females from the c o l o n y . Loss o f y e a r l i n g females at t h e r a t e o f 72% a n n u a l l y from both m o r t a l i t y and e m i g r a t i o n i s s i m i l a r t o y e a r l i n g male l o s s ( m o r t a l i t y p l u s e m i g r a t i o n ) a t Watch Lake and y e a r l i n g female l o s s i n C o l o r a d o (Armitage and Downhower 1 9 7 4 , Armitage 1 9 7 5 ) . An i n c r e a s e i n y e a r l i n g f e -male e m i g r a t i o n t o a l e v e l t h a t would reduce r to 0 i s en-t i r e l y c o n s i s t e n t w i t h the observed system of s o c i a l o r g a n -i z a t i o n and r a t e s o f l o s s . The r a t e of growth o f the Watch Lake p o p u l a t i o n s would have d e c r e a s e d somewhat from i n c r e a s e d h u n t i n g p r e s s u r e a f t e r the s t udy ended. Hunter k i l l would l i k e l y be i n s u f f i c i e n t t o reduce r t o 0 . I n s t e a d I p r e d i c t t h a t one or b o t h o f two i n t e r n a l p r o c e s s e s would r e g u l a t e numbers. T e r r i t o r i a l be-h a v i o u r of b r e e d i n g females s h o u l d e i t h e r reduce t h e number of b r e e d i n g f e m a l e s , e s p e c i a l l y among younger age c l a s s e s , or i n c r e a s e the number o f y e a r l i n g females t h a t e m i g r a t e . T h i s h y p o t h e s i s can be t e s t e d . - i f t h e growth r a t e i n at l e a s t one c o l o n y d e c l i n e s s u b s t a n t i a l l y . The numbers i n a second c o l o n y s h o u l d be reduced by removing a d u l t s . The s t a b l e c o l o n y w i l l a c t as a c o n t r o l i n both space and t i m e . I f t e r -r i t o r i a l b e h a v i o u r o f females c o n t r o l s numbers, the c o n t r o l c o l o n y w i l l have a lower p r o p o r t i o n o f b r e e d i n g females and/ or a h i g h e m i g r a t i o n r a t e o f female y e a r l i n g s t h a n e i t h e r the removal c o l o n y or the c o l o n i e s d e s c r i b e d i n t h i s s t u d y . 1 LITERATURE CITED Altmann, J . 1 9 7 4 . O b s e r v a t i o n a l study o f b e h a v i o r : sam-p l i n g methods . B e h a v i o u r 4 9 : 2 7 7 - 2 6 7 ' . -Andersen, D. C , Ar m i t a g e , D. B. and Hoffmann, R. S. 1 9 7 6 . 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