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Space use in a population of least chipmunks in the Southwest Yukon Glennie, Linda Cuffableness 1988

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SPACE USE IN A POPULATION OF LEAST CHIPMUNKS IN THE SOUTHWEST YUKON by Linda C u f f a b l e n e s s Glennle B . S c , M c G i l l U n i v e r s i t y , 1984 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF 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 r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA September 1988 © L i n d a Glennle, 1988 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Zoology  The University of British Columbia Vancouver, Canada D a t e 9/9/88 DE-6 (2/88) i i ABSTRACT Th i s t h e s i s d e s c r i b e s an i n v e s t i g a t i o n of space use i n l e a s t chipmunks at Kluane Lake, i n the southwest Yukon. I examined demography, home range and h a b i t a t use p a t t e r n s i n the p o p u l a t i o n . Based on l i v e - t r a p p i n g data from two g r i d s over two summers, mean number of animals on the study area was 2 2 . 6/grid, s i m i l a r to chipmunk numbers measured there over the pr e v i o u s four y e a r s . The p o p u l a t i o n was lower than i s g e n e r a l l y found i n the same s p e c i e s f u r t h e r south, although y e a r - t o - y e a r s t a b i l i t y was t y p i c a l . Chipmunks p r e f e r r e d open f o r e s t and shru b - l a n d to closed-canopy f o r e s t , which i s a l s o t y p i c a l of the genus. Home range s i z e s measured u s i n g t e l e m e t r y averaged 4 .86 ha, higher than i n any p r e v i o u s l y p u b l i s h e d study of the genus. I examined the r e l a t i o n s h i p between s o c i a l s p a c i n g and space use. Home range o v e r l a p averaged 9 3 . 4 % ; chipmunks do not appear to defend e x c l u s i v e core a r e a s . Provoked i n t e r a c t i o n s among neighbours suggested t h a t s o c i a l dominance was based on age, weight, and breed i n g c o n d i t i o n , r a t h e r than ownership of space. Although provoked i n t e r a c t i o n s were g e n e r a l l y a g g r e s s i v e , the t e l e m e t r y data suggest t h a t such behaviour was a r t i f a c t u a l . Comparing the encounter frequency of r a d i o - c o l l a r e d animals to t h a t generated by a random model showed t h a t chipmunks avoided encounters, except when h a r v e s t i n g s e a s o n a l l y abundant food. G r i d - t r a p p i n g d i d not i n c r e a s e food or cover a v a i l a b i l i t y enough to a f f e c t home range s i z e . There was evidence t h a t the r presence of t r a p s a f f e c t e d use i n v a l i d a t e trap-based home range and t e l e m e t r y based e s t i m a t e s s i g n i f i c a n t d i f f e r e n c e s . i l l d i s t r i b u t i o n / but not enough to e s t i m a t e s . Comparison of t r a p of home range s i z e y i e l d e d no i v Table of Contents ABSTRACT i i Table of Contents i v L i s t of Tables v i i L i s t of F i g u r e s v i i i ACKNOWLEDGEMENTS i x CHAPTER 1: GENERAL INTRODUCTION 1 CHAPTER 2: DEMOGRAPHY, HABITAT USE, AND HOME RANGE OF THE LEAST CHIPMUNK IN THE SOUTHWEST YUKON 3 INTRODUCTION . 3 METHODS . . 4 Study area 4 L i v e - t r a p p i n g 4 Ra d i o - t e l e m e t r y 8 Ha b i t a t c l a s s i f i c a t i o n 9 RESULTS .' . . . 12 Demography 12 Home Range 19 Ha b i t a t p r e f e r e n c e 20 DISCUSSION 28 Demography . 28 Ha b i t a t use 32 Home range 33 SUMMARY 36 V CHAPTER 3: SPACE USE AND SOCIAL STRUCTURE IN THE LEAST CHIPMUNK 37 INTRODUCTION 37 METHODS 39 B e h a v i o u r a l o b s e r v a t i o n 39 Encounter avo idance . . . . 41 RESULTS 45 Home range o v e r l a p 45 B e h a v i o u r a l o b s e r v a t i o n . . 51 Encounter avo idance 53 DISCUSSION 54 CHAPTER 4: THE INFLUENCE OF GRID-TRAPPING ON SPACE USE AND HOME RANGE IN THE LEAST CHIPMUNK 60 INTRODUCTION 60 P r e d i c t ions 61 METHODS . . . 62 E x p e r i m e n t a l d e s i g n . . . . . 62 Home range c a l c u l a t i o n s 63 E f f e c t of da ta source on home range e s t ima te . . . 64 RESULTS 65 E f f e c t s of g r i d - t r a p p i n g on home range 65 E f f e c t s of da ta source on home range 67 DISCUSSION 67 E f f e c t s of g r i d - t r a p p i n g on home range 67 v i E f f e c t s of da ta source on home range 69 LITERATURE CITED 71 APPENDIX: SOURCE CODE LISTING ( i n BASIC) OF RANDOM CHIPMUNK ENCOUNTER SIMULATION MODEL . . . . 76 vii L i s t o£ Tables Table 2.1—Summary of grid-trapping changes 8 Table 2.2—Habitat c l a s s i f i c a t i o n s . . 10 Table 2.3—Population means 15 Table 2.4—Mean Minimum Survival Rates 16 Table 2.5—Minimum over-winter s u r v i v a l 17 Table 2.6—Means (and ranges) of chipmunk weights (ln g) . . 18 Table 2.7—Summary of habitat preferences from trapping data 25 Table 2.8—Chipmunk home ranges from t h i s and previous studies 34 Table 3.1—Mean home range overlap 46 Table 3.2--Mean distances from in t e r a c t i o n to home . . . . . 52 Table 3.3—Mean encounter frequency on gr i d H vs. simulation 54 Table 4 . l--Telemetry-based home range estimates * 65 v i i i L i s t of F i g u r e s F i g . 2 . 1 — The study area . 6 F i g . 2 . 2 — J o l l y - S e b e r p o p u l a t i o n e s t i m a t e s f o r G r i d s X and H 1 3 F i g . 2 . 3 - - H a b i t a t maps: ( a ) G r i d X, ( b ) G r i d H 2 1 F i g . 2 . 4 — Observed and expected number of t e l e m e t r y l o c a t i o n s v s . v e g e t a t i o n type 2 6 F i g . 2 . 5 — H a b i t a t use index f o r a d u l t s and j u v e n i l e s v s . h a b i t a t type. 29 F i g . 3 . 1 — Flowchart of random-encounter s i m u l a t i o n model. 4 3 F i g . 3 . 2 — T e l e m e t r y - b a s e d home range map of G r i d H 47 F i g . 3 . 3 — T e l e m e t r y - b a s e d home range map of G r i d X 49 I x ACKNOWLEDGEMENTS I would l i k e t o thank my s u p e r v i s o r , C h a r l e s Krebs and my r e s e a r c h committee, Jamie Smith, Lee Gass and Tony S i n c l a i r f o r t h e i r advice and support. Jamie Smith's amazingly prompt and thorough comments on the rough d r a f t were g r e a t l y a p p r e c i a t e d . I n h a b i t a n t s of Kluane Research S t a t i o n a l l provided h e l p of v a r i o u s k i n d s . The f r i e n d s h i p and encouragement of Andy and C a r o l e W i l l i a m s made the f i e l d work p o s s i b l e . S i a n and Megan W i l l i a m s , Andrew Lawrence, S h i e l a Fox, Garth Mowat, S a l l y Wright, P a t t y H a r r i s , and L i s a M c l n t y r e p r o v i d e d f i e l d a s s i s t a n c e . During the w r l t i n g - u p stage, Peter Watts p r o v i d e d innumerable s u g g e s t i o n s , constant brow-beating, and i n v a l u a b l e h e l p with programming, f i g u r e s , p r o o f - r e a d i n g , f o r m a t t i n g , and i n w r i t i n g these acknowledgements. Without h i s help the chipmunk data would s t i l l be locked Inside the computer. I thank A l i s t a i r B l a c h f o r d and Susan E r t i s f o r programming a s s i s t a n c e , C h r i s Foote (who once saved my l i f e ) , Simon Courtenay, Gordon Haas, Rob Powell and Don Robinson f o r a d v i c e and f o r b o l s t e r i n g morale. I thank my mother f o r being e n d l e s s l y s u p p o r t i v e even while convinced of the u t t e r lunacy of t h i s endeavor. My f i e l d work was funded by Northern S t u d i e s T r a i n i n g Grants, and NSERC gr a n t s to Dr. Krebs. I was supported by t e a c h i n g a s s i s t a n t s h i p s while at U.B.C. T h i s t h e s i s i s d e d i c a t e d to Cygnus and Zombie. 1 CHAPTER 1: GENERAL INTRODUCTION T h i s study i n v e s t i g a t e s f a c t o r s a f f e c t i n g space use i n a p o p u l a t i o n of l e a s t chipmunks (Tamias minimus) a t Kluane Lake i n the southwest Yukon. Forbes ( 1 9 6 6 ) , Sheppard ( 1 9 6 9 ) , and Meredith ( 1 9 7 2 ) remarked on the p a u c i t y of data a v a i l a b l e on western s p e c i e s of chipmunk. Since t h a t time, a number of s t u d i e s have i n v e s t i g a t e d p a t t e r n s of space use, h a b i t a t p r e f e r e n c e and s o c i a l dominance i n the group of western chipmunks f o r m e r l y known as Eutamlas. F i v e of these have i n c l u d e d Tamias minimus among the s p e c i e s s t u d i e d ( H e l l e r , 1 971; Sheppard, 1971; Meredith, 1976; S t a t e s , 1 9 76; C h a p p e l l , 1 9 7 8 ) . These s t u d i e s a s s e s s e d the i n f l u e n c e of c o m p e t i t i o n with other chipmunk s p e c i e s and of d i f f e r e n c e s i n h a b i t a t p r e f e r e n c e on a l t i t u d i n a l z o n a t i o n i n the d i s t r i b u t i o n of the l e a s t chipmunk and i t s g e o g r a p h i c a l l y sympatric congeners. T h i s study p r e s e n t s the f i r s t data on space use, h a b i t a t p r e f e r e n c e and s o c i a l dominance f o r the l e a s t chipmunk i n i s o l a t i o n from i t s congeners. Chapter 2 p r o v i d e s an overview of demography and home range in the p o p u l a t i o n . I t d e s c r i b e s the h a b i t a t and i n v e s t i g a t e s the animals' h a b i t a t use p a t t e r n s . P o p u l a t i o n l e v e l s , home range and h a b i t a t use are then compared to those r e p o r t e d i n p r e v i o u s s t u d i e s of the genus. Chapter 3 examines the r e l a t i o n s h i p between s o c i a l s p a c i n g 2 and space use. To determine whether s o c i a l s p a c i n g o c c u r s , I ask whether chipmunks defend e x c l u s i v e a r e a s , whether s o c i a l dominance i s a f f e c t e d by ownership of space, and whether chipmunks a v o i d e n c o u n t e r i n g each o t h e r . Chapter 4 e v a l u a t e s whether the p r o v i s i o n of food and cover r e s u l t i n g from t r a p p i n g and p r e - b a i t i n g i n c r e a s e s the a v a i l a b i l i t y of these r e s o u r c e s enough to a f f e c t home range. I then compare t r a p and t e l e m e t r y based methods of e s t i m a t i n g home range. 3 CHAPTER 2: DEMOGRAPHY, HABITAT USE, AND HOME RANGE OF THE LEAST CHIPMUNK IN THE SOUTHWEST YUKON INTRODUCTION Th i s chapter p r e s e n t s data c o l l e c t e d d u r i n g the summers of 1985 and 1986 on the demography and home range movements of a p o p u l a t i o n of l e a s t chipmunks (Tamias minimus) near Kluane Lake i n the southwest Yukon. The home range data are used to as s e s s h a b i t a t p r e f e r e n c e s of chipmunks, and the home ranges, demographic p a t t e r n s and d e r i v e d h a b i t a t p r e f e r e n c e s are compared wit h those p r e v i o u s l y r e p o r t e d . P u b l i s h e d e s t i m a t e s of home range and h a b i t a t a s s o c i a t i o n s of the l e a s t chipmunk are r e l a t i v e l y common i n the l i t e r a t u r e , s i n c e s e v e r a l s t u d i e s have used such estimates i n a s s e s s i n g c o m p e t i t i v e i n t e r a c t i o n s with congeners ( H e l l e r , 197i; Sheppard, 1971; Meredith, 1976; S t a t e s , 1976; C h a p p e l l , 1978). T h i s p r o v i d e s ample o p p o r t u n i t y f o r comparison. The few s t u d i e s of the l e a s t chipmunk t h a t have not focu s s e d on c o m p e t i t i o n d e s c r i b e m o r p h o l o g i c a l t r a i t s and l i f e - h i s t o r y c h a r a c t e r i s t i c s r a t h e r than demography ( C r i d d l e , 1943; Sheppard, 1969; S k r y j a , 1974). However, s t u d i e s of the demography of other chipmunk p o p u l a t i o n s are more numerous (Gashwiler, 1970; Tryon and Snyder, 1973; S u l l i v a n et al, 1983). The chipmunk p o p u l a t i o n 4 near my study area a t Kluane has been monitored s i n c e 1980 l n demographic s t u d i e s of other s m a l l mammals ( G i l b e r t and Krebs, 1984; G i l b e r t , u npublished d a t a ) . Although my f i e l d work covered too s h o r t a p e r i o d t o permit robust c o n c l u s i o n s about demographic p a t t e r n s , d e n s i t i e s l n t h i s study can be compared to those r e p o r t e d i n p r e v i o u s s t u d i e s of chipmunks, and with those p r e v i o u s l y found near my study area a t Kluane. METHODS Study area The study area was l o c a t e d j u s t e a s t of Kluane Lake (61° N, 138° W). Two t r a p p i n g g r i d s were e s t a b l i s h e d a p p r o x i m a t e l y 2 and 3 km from the lake on an o l d a l l u v i a l f a n , bounded by S i l v e r Creek on the n o r t h - e a s t and p a r t i a l l y bounded by the Al a s k a Highway on the south. V e g e t a t i o n cover ranged from c l o s e d spruce f o r e s t ( P i c e a glauca), to open spruce - soapberry {Shepherdla canadensis) shrub-land, to open meadows dominated by Dryas dr ummondi 1. L i v e - t r a p p i n g P o p u l a t i o n s i z e and home ranges were monitored u s i n g l i v e t r a p p i n g . In 1985 I s e t up two r e c t a n g u l a r t r a p p i n g g r i d s , 6 ha 5 i n s i z e and 500 m a p a r t . Animals were c a p t u r e d i n Longworth t r a p s a t s t a t i o n s 21 m a p a r t . Traps were b a i t e d w i th a m ix tu re of oa t s and sun f lower seeds , and were l o cked open and l e f t p r e -b a l t e d between t r a p p i n g s e s s i o n s . I t r apped each g r i d e v e r y 2 to 3 weeks. Dur ing t r a p p i n g s e s s i o n s , I s e t t r a p s d u r i n g the morning of day 1 and l o c k e d them open on the morning of day 3. Traps were g e n e r a l l y checked i n the a f t e r n o o n and even ing of day 1, morn ing, a f t e r n o o n and even ing of day 2, and i n the morning of day 3 f o r a t o t a l of 6 checks per s e s s i o n . Captured chipmunks were permanent ly marked by t o e - c l i p p i n g and t h e i r pe lage was marked w i th Nyanzo l D f o r v i s u a l i d e n t i f i c a t i o n . I r e c o r d e d c a p t u r e l o c a t i o n , we i gh t , sex, age c l a s s ( a d u l t or j u v e n i l e ) and b r e e d i n g c o n d i t i o n of each chipmunk. I a s se s sed b r e e d i n g c o n d i t i o n of females a c c o r d i n g to n i p p l e s i z e ( s m a l l , medium or l a r g e ) and whether they were o b v i o u s l y p regnant . Males were c l a s s i f i e d as b r e e d i n g or non -b reed ing a c c o r d i n g to the p o s i t i o n of the t e s t e s ( s c r o t a l or abdominal ) r e s p e c t i v e l y . I t r apped g r i d s from e a r l y May to l a t e August , 1985, and from e a r l y May to mid-September, 1986. In m i d - J u l y , 1985, I expanded the western-most g r i d ( g r i d X) from 6 ha to 8 ha so t h a t i t would c o n t a i n most nes t s i t e s when j u v e n i l e s f i r s t e n t e r e d the t r a p s ( F i gu re 2 .1 ) . In May, 1986, I expanded both g r i d s to 18 ha i n o rder to c o m p l e t e l y encompass most l o c a l home ranges . I a l s o i n c r e a s e d the d i s t a n c e between g r i d s t o 1 km to e l i m i n a t e movement between g r i d s (Chapter 4 ) . I removed t r a p s from the e a s t e r n t h i r d of g r i d X and expanded i t westward. Home range 6 F i g . 2.1 — The study a r e a , showing l o c a t i o n of t r a p p i n g g r i d s H and X. Shading i n d i c a t e s extent of g r i d s a t d i f f e r e n t times (see t e x t f o r d e t a i l s ) . 7 e s t i m a t e s from 1985 were h i gh enough t o warrant a c o a r s e r l e v e l of s amp l i ng , so t r a p - s p a c i n g was i n c r e a s e d to 42 m. In 1986 the two g r i d s were t r apped f o r on l y h a l f the season (see Chapter 4 ) . Both g r i d s were t r apped l n e a r l y May and m i d -September, the eas ternmost g r i d ( g r i d H) a l one was t r apped from May to m i d - J u l y , and g r i d X a l one was t rapped from m i d - J u l y to September. The s i z e s , l o c a t i o n s , t r a p - s p a c i n g , and t r a p p i n g p e r i o d s of the two g r i d s a re summarized i n Tab le 2 .1 . Tab le 2.1—Summary of g r i d - t r a p p i n g changes YEAR SPACING TRAPS GRIDS 1985 21 m .5 km 1986 42 m 1 km GRID SIZE H 6 ha X 6 ha to J u l y 17, then 8 ha H 18 ha X 18 ha PERIOD OF OPERATION H May t h r u Aug. X May t h r u Aug. H May t h r u J u l y 16 and m i d - S e p t . X e a r l y May and J u l y 16 t h r u Sep t . R a d i o - t e l e m e t r y R a d i o - t e l e m e t r y was used to l o c a t e n e s t - s i t e s of most a d u l t r e s i d e n t s i n both y e a r s . In 1986 I used t e l e m e t r y to p r o v i d e c o n t i n u o u s e s t i m a t e s of home range. R a d i o - t r a n s m i t t e r s were c o l l a r - m o u n t e d ; each package weighed 2 - 2.5 g, l e s s than 5% o f 9 mean 1986 a d u l t body weight (51 g ) . S i g n a l s t r e n g t h was too low to permit t r i a n g u l a t i o n of animal l o c a t i o n s , so home range data were c o l l e c t e d u s i n g scan sampling. I walked a r e g u l a r census ro u t e on each g r i d , l e a v i n g the route t o t r a c k each s i g n a l t o I t s source and r e c o r d i t s l o c a t i o n . Chipmunks r e a d i l y grew accustomed to my presence and remained a p p a r e n t l y u n d i s t u r b e d as long as I d i d not approach w i t h i n 5 m. Upon l o c a t i n g an u n d i s t u r b e d animal, I recorded the l o c a t i o n , s u b s t r a t e , behaviour over a 1 minute p e r i o d and food type of those animals which were e a t i n g . L o c a t i o n o n l y was recorded i f the animal was d i s t u r b e d , i f an a s s i s t a n t was doing the t r a c k i n g , or i f more than one person was p r e s e n t . H a b i t a t c l a s s i f i c a t i o n In order to e v a l u a t e the a s s o c i a t i o n between the home range movements of chipmunks and t h e i r h a b i t a t , I c l a s s i f i e d each 30 m by 30 m g r i d quadrat a c c o r d i n g to the dominant cover type and s u b s t r a t e . Open and c l o s e d f o r e s t communities were d i s t i n g u i s h e d from each other a c c o r d i n g to percent cover of the dominant t r e e s p e c i e s . Percent cover was recorded as the mean of v i s u a l e s t i m a t e s by two d i f f e r e n t o b s e r v e r s , taken over a c i r c l e of r a d i u s 10 m measured from the g r i d stake a t the c e n t r e of each quadrat. Where e s t i m a t e s d i f f e r e d by more than 20 percentage p o i n t s , percent cover was r e a s s e s s e d by d i f f e r e n t o b s e r v e r s . Quadrats with mean per c e n t cover l e s s than 25% were c l a s s e d as 10 open forest; those with cover of over 25%, and In which tree canopies overlapped, were classed as closed f o r e s t . I recognized eight d i f f e r e n t habitat types (Table 2.2). Table 2.2--Habitat c l a s s i f i c a t i o n s HABITAT TYPE SPECIES SUBSTRATE 1. Closed spruce Picea glauca, Shepherdia Fine t i l l -soapberry 2. Closed spruce -moss 3. Ecotone between open and closed habitats 4. Open poplar, soapberry, spruce 5. Open dryas 6. Open spruce -soapberry 7. Dead spruce 8. Coarse t i l l , soapberry canadensis, Hedysarum boreale, Arctostaphylos uva-ursl Plcea glauca, Shepherdia canadensis, Hedysarum boreale, Azctostaphylos rubra, A. uva-ursi, Lupinus arcticus Shepherdia canadensis, Salix spp. Eleagnus commutata, Arctostaphylos uva-ursl, Hedysarum boreale Populus balsamlfera, Shepherdia canadensis, Picea glauca, Dryas drummondii, Arctostaphylos rubra, A. uva-ursi, Oxytropis campestris Dryas drummondi1 Picea glauca, Shepherd la canadensis, Dryas drummondi1, Arctostaphylos rubra, A. uva-ursl, Oxytropis campestrIs Picea glauca Shepherdia canadensis S o l i , moss Fine t i l l Coarser t i l l Coarser t i l l Coarser t i l l Very coarse t i l l Very coarse t i l l 11 F i v e of these conformed to the h a b i t a t c l a s s i f i c a t i o n s of Krebs and Wingate (1976). These were: two c l o s e d f o r e s t communities, spruce ( P i c e a glauca) -moss and spr u c e - s o a p b e r r y (Shepherdla canadensis); two open f o r e s t communities, spr u c e - s o a p b e r r y and balsam poplar (Populus b a l s a m i f e r a ) - soapberry; and Dryas drummondii f l a t s . The spruce-moss community has a sparse herb l a y e r of l i c o r i c e r o o t (Hedysarum boreale) and b e a r b e r r y (Arctostaphylos r u b r a and A. u v a - u r s i ) , some sparse s o a p b e r r y shrub, and almost complete moss co v e r . The c l o s e d s p r u c e -soapberry community has a s p a r s e r herb l a y e r , a denser l a y e r of soapberry shrub, and a stony s u b s t r a t e with l i t t l e moss. The open sp r u c e - s o a p b e r r y has a s u b s t r a t e of c o a r s e r t i l l , and a herb l a y e r dominated by be a r b e r r y , Dryas, and locoweed ( O x y t r o p i s c a m p e s t r i s ) , t h a t i s s i m i l a r to the herb l a y e r of the open p o p l a r - s o a p b e r r y community. Three a d d i t i o n a l h a b i t a t types were: bare a l l u v i a l t i l l w i t h sparse soapberry, bare a l l u v i a l t i l l w i th dead (drowned) spruce, and an ecotone between the c l o s e d and open f o r e s t communities c h a r a c t e r i s e d by soapberry, w i l l o w ( S a l i x g l a u c a ) , and sometimes s i l v e r b e r r y (Bleagnus commutata). 12 RESULTS Demography J o l l y - S e b e r e s t i m a t i o n was used to c a l c u l a t e p o p u l a t i o n s i z e s from the c a p t u r e - r e c a p t u r e data (Seber, 1982). These r e s u l t s are p l o t t e d i n F i g u r e 2.2. In 1985, the mean number of animals d i d not d i f f e r s i g n i f i c a n t l y between g r i d H and g r i d X (t=2.00, p=.10). On pooled data from both g r i d s , a t - t e s t r e v e a l e d no s i g n i f i c a n t d i f f e r e n c e l n the number of animals between years (t=1.91, p=.07). There was an average of 22.6 chipmunks per g r i d p r e s e n t on both g r i d s over both y e a r s . The number of a d u l t s on each g r i d remained s t a b l e through the s p r i n g and summer season on both g r i d s , a l t h o u g h i n 1985 the number of males dropped s l i g h t l y a f t e r May, c o i n c i d e n t with the end of the mating season. There were more a d u l t s on g r i d H i n 1986 (23 .4 ) than i n 1985 (13.7) or on g r i d X l n e i t h e r year (17.2 i n 1985, 16.2 i n 1986). Since there was a t h r e e - f o l d i n c r e a s e * l n the s i z e of the g r i d s from one year to the next, numbers of a d u l t s should have been higher on both g r i d s i n 1986. The asymmetry l n the number of new animals occupying the expanded g r i d s c o u l d be due to the f a c t t h a t the expansion of g r i d H Included more f a v o u r a b l e h a b i t a t types than the expansion of g r i d X. The mid-summer p o p u l a t i o n peak e v i d e n t l n F i g u r e 2.2 i s the r e s u l t of j u v e n i l e emergence. No p o p u l a t i o n peak i s shown f o r g r i d H i n 1986 s i n c e t r a p p i n g stopped before j u v e n i l e s were o l d 13 F i g . 2.2 -- Jolly-Seber population estimates for Grids X and H s 14 May June July Aug May June July Aug Sept 1985 1986 20 Grid H O — O females 15+ m a l e s O \ //° 5+ . J — 1 1 1 \ \ 1 1 h May June July Aug May June July 1985 1986 15 enough to enter traps. The appearance of juveniles in July was consistent from year to year. Chipmunks, including Tamias minimus, breed only once a year in Canada (Criddle, 1943; Forbes, 1966; Sheppard, 1969) . Mating tends to occur a l l at once in late A p r i l - e a r l y May, '• b i r t h in late May-early June, and juvenile emergence in Ju l y . That there is some v a r i a t i o n in this is ind i c a t e d by the f a c t that weights of juveniles captured in the same session have a range of approximately 10 g. From Table 2.3 i t appears that more juveniles emerged on grid X than on grid H in 1985, but t h i s d i f f e r e n c e is not s i g n i f i c a n t (t=1.03, p>.50). Table 2 . 3--Populatlon means GRID YEAR NUMBER OF ADULTS NUMBER OF JUVENILES FEMALES HALES FEMALES MALES X 19 8 5 MEAN = 6-2 11.1 ' 7.8 4.1 S.D. = 2.0 1.8 1.1 1.6 1986 MEAN = 7 . 8 8 . 4 •9 . 3 3.6 S-. D . = 2.7 1.5 3.2 1.7 h 19 8 5 MEAN = 5 . 5 8.2 5.8 3 . 7 S.D. = 0 . 8 1.2 1 . 7 1 . 0 19 8 6 MEAN = 12.1 11. 4 1.7* 0* S.D. = 0 . 8 0.9 0 * 0* •sample size too low to accurately calculate N (trapping discontinued a f t e r juvenile emergence). Among adults, the sex ratio vas consistently biase'd toward males (1.57 males/female) on grid X. On grid H i t was biased toward males in 1985 (1.50 males/female) but wa3 nearly even in 16 1986 (0.95 males/female). Among j u v e n i l e s , more females than males were captured on both g r i d s . Mean minimum s u r v i v a l r a t e s between-sesslons (three-weeks) are presented i n Table 2.4. J o l l y - S e b e r s u r v i v a l e s t i m a t e s c o n s i s t e n t l y exceeded u n i t y and are t h e r e f o r e not b i o l o g i c a l l y meaningful (Boonstra, 1985). Table 2.4- -Mean Minimum S u r v i v a l Rates GRID YEAR AGE SEX SURVIVAL X 1985 1986 a d u l t a d u l t male male 0.88 0.82 1985 1986 a d u l t a d u l t female female 0.94 0.86 h 1985 1986 a d u l t a d u l t male male 0.89 0.93 1985 1986 a d u l t a d u l t female female 0.95 0.86 X 1985 1986 j u v e n i l e j u v e n i l e male male 0.34 0.38 1985 1986 j u v e n l l e j u v e n i l e female female 0.60 0.87 h 1985 1985 j u v e n i l e j u v e n i l e male female 0.67 1.00 Ad u l t s u r v i v a l remained high over the summer, a v e r a g i n g 0.89 . There were no d i f f e r e n c e s i n a d u l t s u r v i v a l between g r i d s or between the sexes. J u v e n i l e s u r v i v a l averaged 0.6, but was g e n e r a l l y lower f o r males (0.44) than f o r females (0.84). For 17 1985, the year with the most da t a , j u v e n i l e s u r v i v a l was much lower on g r i d X than on g r i d H. N e a r l y twice as many j u v e n i l e s were captured on g r i d X i n 1985 as on g r i d H (22 v s . 13), c o n s i s t e n t with the d i f f e r e n t number of bree d i n g females. Seven bree d i n g females were r e s i d e n t on g r i d X, while 4 were r e s i d e n t on g r i d H i n 1985. Minimum overwinter s u r v i v a l i s l i s t e d i n Table 2.5. Females s u r v i v e d b e t t e r than males on both g r i d s , both f o r a d u l t s and f o r j u v e n i l e s . On g r i d H, a d u l t s s u r v i v e d b e t t e r than j u v e n i l e s , while on g r i d X the r e v e r s e was t r u e . Table 2.5—Minimum over-winter s u r v i v a l GRID AGE SEX SURVIVAL (N) h a d u l t male 0.75 (8) h a d u l t female 1.00 (5) h j u v e n i l e male 0.60 (5) h j u v e n i l e female 1.00 (7) X a d u l t male 0.56 (9) X a d u l t female . 0.75 (4 ) X j u v e n i l e male 0.67 (3) X j u v e n i l e female 1.00 (6) Ad u l t weight averaged 50.4 g over both g r i d s and both years (Table 2.6) and d i d not d i f f e r s i g n i f i c a n t l y between y e a r s . Weights were low when animals were f i r s t t rapped i n May (mean = 44.9 g ) , and Increased to an average of over 50 g by e a r l y June. From t h i s p o i n t , male weight remained r e l a t i v e l y s t a b l e over the summer, while female weight i n c r e a s e d . Females were h e a v i e r by 5 g on average while l a c t a t i n g than d u r i n g pregnancy. The s m a l l e s t 18 j u v e n i l e s to enter t r a p s weighed 29 g, but r a p i d l y grew to a d u l t weight. By September, mean j u v e n i l e weight (49.7 g) d i d not d i f f e r from mean a d u l t weight (50.4 g ) . Weights used to c a l c u l a t e means i n Table 2.6 were o b t a i n e d by weighing each c a p t u r e d animal once per t r a p - s e s s i o n . There are up to seven repeated weighings per animal per year, so the means are not d e r i v e d from e n t i r e l y independent measurements. Table 2.6—Means (and ranges) of chipmunk weights ( i n g) YEAR ADULT MALES ADULT FEMALES JUVENILES 1985 47.2 53.1 44.3 (37 - 57) (40 - 65) (31 - 52) 1986 47.8 52.6 48.0 (39 - 57) (39 - 64) (29 - 53) When l i v e - t r a p p i n g began i n May, males were a l r e a d y i n bre e d i n g c o n d i t i o n and remained so u n t i l the end of May. In 1986, breeding was underway by l a t e A p r i l . I observed s e v e r a l mating chases a t the end of A p r i l when the t r a p s were s t i l l b u r i e d In snow. In both y e a r s , a l l males captured i n May were i n br e e d i n g c o n d i t i o n . Females began l a c t a t i n g i n l a t e May i n 1985 and i n e a r l y June In 1986. They had f i n i s h e d l a c t a t i n g by the be g i n n i n g of August. T h i s agrees with C r l d d l e ' s (1943) e s t i m a t e of a 30-day g e s t a t i o n p e r i o d f o r Tamlas minimus bozealis. In 1985, each g r i d had one r e s i d e n t female t h a t d i d not breed. In 1986, the same r e s i d e n t female on g r i d H was the o n l y female t h a t d i d not breed. For both sexes, a l l of the y e a r l i n g s captured on 19 the g r i d s bred d u r i n g t h e i r f i r s t b r e e d i n g season. T h i s c o n t r a s t s with Sheppard (1969) who found t h a t Tamlas minimus oreocetes i n western A l b e r t a d i d not breed i n the s p r i n g f o l l o w i n g t h e i r b i r t h . J u v e n i l e s were f i r s t observed on the study area on June 29, 1985 and on June 30, 1986. J u v e n i l e s f i r s t e n tered t r a p s on J u l y 10 i n both y e a r s . T h i s supports H i r s h f e l d and Br a d l e y ' s (1977) estimate of j u v e n i l e emergence a t 5 weeks of age f o r Tamlas panamintinus and T. palmer!. No e s t i m a t e s of r e c r u i t m e n t are presented here because the expansion of g r i d s and low t r a p p a b i l i t y of young j u v e n i l e s p r e c l u d e d t h a t a n a l y s i s . Home Range Home range was est i m a t e d from the t e l e m e t r y data f o r 23 animals l n 1986. Twenty-five chipmunks were f i t t e d with r a d i o -c o l l a r s , but two (both females from g r i d H) were excluded from home range c a l c u l a t i o n s . Female 60 was excluded because n e a r l y h a l f of her t e l e m e t r y l o c a t i o n s were a c r o s s S i l v e r Creek from the g r i d . Female 108 was excluded from a l l a n a l y s i s because she developed a severe eye i n f e c t i o n t h a t might have been caused by an i n f e c t i o n on her neck due to the t i g h t n e s s of her c o l l a r . She became t r a p - s h y u n t i l the end of the summer, when I was f i n a l l y a b l e to remove the c o l l a r . Except i n e a r l y May when some of the other c o l l a r s were too t i g h t and caused c h a f i n g around the neck (and f o r which the data were a l s o e x c l u d e d ) , the other chipmunks 20 d i d not appear to s u f f e r adverse e f f e c t s from wearing r a d i o -c o l l a r s . A t o t a l of 1238 t e l e m e t r y l o c a t i o n s , c o l l e c t e d from May through September, were used to estimate home ranges. Home range s i z e s were c a l c u l a t e d by the minimum convex polygon method, based on a minimum of 20 l o c a t i o n s , with an average of 54 p o i n t s per home range. Mares e t a l (1980) found t h a t 20 cap t u r e s was the minimum number n e c e s s a r y to a c c u r a t e l y e s t i m a t e home range of the e a s t e r n chipmunk. Home range areas range from 0.97 ha to 9.65 ha with a mean area of 4.86 ha (S.D.=2.35). Home ranges of males (mean=6.13 ha, S.D.=1.96) were s i g n i f i c a n t l y l a r g e r than those of females (mean=2.89 ha, S.D.=1.331), t=4.34, p<.001). A n a l y s i s of other a s p e c t s of chipmunk home range i n appear i n Chapters 3 and 4. H a b i t a t p r e f e r e n c e To assess h a b i t a t p r e f e r e n c e , I used the h a b i t a t c l a s s i f i c a t i o n data to c o n s t r u c t a h a b i t a t map f o r each g r i d ( P i g 2.3). H a b i t a t types are l i s t e d i n Table 2.2. On g r i d X, a l l 8 h a b i t a t types are r e p r e s e n t e d , while on g r i d H o n l y 4 of them occur: c l o s e d spruce-soapberry, ecotone, open p o p l a r - s o a p b e r r y and Dryas f l a t s . Both the l i v e - t r a p p i n g and the t e l e m e t r y l o c a t i o n data were p l o t t e d on t h i s map to t e s t f o r a s s o c i a t i o n s between h a b i t a t type and frequency of use. For the l i v e - t r a p p i n g d a t a , I used a G t e s t t o compare the frequency 21 F i g . 2.3 H a b i t a t maps: ( a ) G r i d X, ( b ) G r i d H 1. Closed spruce soapberry 2. Cl o s e d spruce moss 3. Ecotone 4. Open po p l a r soapberry 5. Dryas f l a t s 6. Open spruce soapberry 7. Dead spruce 8. Open t i l l s o a pberry 22 23 of capture In each v e g e t a t i v e community with t h a t expected from the p r o p o r t i o n of t r a p s s e t i n that community. T e s t s were performed s e p a r a t e l y f o r the two g r i d s and f o r each s i z e of each g r i d , s i n c e the d i s t r i b u t i o n of t r a p s i n the h a b i t a t d i f f e r e d a f t e r each expansion. For g r i d H, use d i f f e r e d s i g n i f i c a n t l y from t r a p d i s t r i b u t i o n i n both y e a r s : G=23.578 f o r 1985; f o r 1986 0=22.945, p<.001 i n both y e a r s . In both y e a r s , chipmunks were c a p t u r e d l e s s f r e q u e n t l y i n c l o s e d s p r u c e - s h e p h e r d i a h a b i t a t and more f r e q u e n t l y i n open p o p l a r - s h e p h e r d i a h a b i t a t than expected from t r a p d i s t r i b u t i o n . Observed and expected f r e q u e n c i e s were equal f o r the ecotone, but chipmunks were captured l e s s o f t e n than expected on Dryas meadow i n 1985, but more o f t e n than expected i n 1986. Dzyas meadow was the o n l y h a b i t a t type not r e p r e s e n t e d i n the expansion of g r i d H. Changes between years were t h e r e f o r e due to changes In the sampling d i s t r i b u t i o n . For g r i d X, G t e s t s comparing frequency of capture i n each h a b i t a t type with r e l a t i v e number of t r a p s s e t there were s i g n i f i c a n t on a l l three g r i d s i z e s . For the s m a l l e r 1985 g r i d from which the p o p l a r - s o a p b e r r y and dead spruce h a b i t a t s were absent, G=12.107, df=5 and .025<p<.05. For the expanded 1985 g r i d on which a l l e i g h t h a b i t a t types o c c u r r e d , G=22.107, df=7 and .001<p<.005. For the 1986 g r i d from which c l o s e d s p r u c e -s o a p b e r r y h a b i t a t was absent, G=198.2, df=6 and p<.001. When c l o s e d s p r u c e - s h e p h e r d i a h a b i t a t o c c u r r e d on g r i d X fewer c a p t u r e s were l o c a t e d there than expected. For the c l o s e d spruce-moss h a b i t a t , observed number of c a p t u r e s was n e a r l y e q u a l to the number expected on the s m a l l e s t g r i d X. A f t e r the g r i d was expanded, more of i t was l n spruce-moss h a b i t a t , and f a r fewer ca p t u r e s than expected o c c u r r e d t h e r e . For a l l three s i z e s of the g r i d , the number of capt u r e s i n open s p r u c e - s o a p b e r r y and i n Dryas h a b i t a t was g r e a t e r than expected. The number of c a p t u r e s i n ecotone was l e s s than expected i n the s m a l l and medium v e r s i o n s of the g r i d , but g r e a t e r than expected i n the l a r g e v e r s i o n of the g r i d . The t i l l - s o a p b e r r y h a b i t a t had a g r e a t e r than expected number of c a p t u r e s , while the t i l l - d e a d spruce had fewer c a p t u r e s than expected f o r the medium g r i d and more than expected f o r the l a r g e g r i d . These r e s u l t s a re summarized i n Table 2.7. A H + M i n d i c a t e s t h a t number of c a p t u r e s observed i s g r e a t e r than expected, a "-" i n d i c a t e s t h a t observed number of capt u r e s i s l e s s than expected, "0" means t h a t observed number of c a p t u r e s e q u a l l e d expected number, and the absence of data i s i n d i c a t e d by a ".". Trapping r e s u l t s show t h a t chipmunks p r e f e r open h a b i t a t types (4,5,6, and 8) over c l o s e d spruce f o r e s t ( h a b i t a t s 1 and 2). R e s u l t s are I n c o n c l u s i v e f o r the ecotone and dead spruce h a b i t a t s (3 and 7 ) . I 2 5 Table 2.7—Summary of h a b i t a t p r e f e r e n c e s from t r a p p i n g d a t a . HABITAT TYPE 1 2 > 3 4 5 6 7 8 H 85 • 0 + • • * H 86 - 0 + + • • X 85, 6ha 0 - + + X 85, 8ha - : - + + + 0 X 86 • + + + + The same t e s t s were performed on t e l e m e t r y l o c a t i o n s i n s i d e t r a p p i n g g r i d s . H a b i t a t types were used non-randomly on both g r i d s (p<.001). Observed and expected numbers of l o c a t i o n s are p l o t t e d i n F i g u r e 2.4. For g r i d H the t e l e m e t r y r e s u l t s were s i m i l a r to the t r a p p i n g r e s u l t s f o r 1986. The t e l e m e t r y r e s u l t s f o r g r i d X were l e s s c o n s i s t e n t with the t r a p p i n g r e s u l t s . G r i d X t r a p p i n g and t e l e m e t r y r e s u l t s both show a p o s i t i v e a s s o c i a t i o n w i t h open s p r u c e - s o a p b e r r y and open t i l l - s o a p b e r r y (types 6 and 8) and a n e g a t i v e a s s o c i a t i o n with c l o s e d spruce-moss (type 2). However, t e l e m e t r y data were p o s i t i v e l y a s s o c i a t e d with ecotone (type 3), while t r a p p i n g r e s u l t s were i n c o n c l u s i v e . There i s a s t r o n g p o s i t i v e a s s o c i a t i o n with Dryas f l a t s and open p o p l a r -soapberry (types 4 and 5) i n the t r a p p i n g d a t a , but f o r t e l e m e t r y data observed l o c a t i o n s do not d i f f e r from the number expected. 26 F i g . 2.4 — Observed and expected number of t e l e m e t r y l o c a t i o n s vs. v e g e t a t i o n type. 1. Closed spruce soapberry 2. C l o s e d spruce moss 3. Ecotone 4. Open p o p l a r soapberry 5. Dryas f l a t s 6. Open spruce soapberry 7. Dead spruce 8. Open t i l l s o apberry 27 Grid H (ZD observed E53 expected Habitat Type Grid X I I observed ESS expected n f l n l DM. 2 3 4 5 6 7 8 9 Habitat Type 28 I compared the habitat preferences of adults and juveniles using the recapture data for 1985, when juvenile recapture data were most numerous (Figure 2.5). The habitat use index was calculated by d i v i d i n g the percent of captures observed in a given habitat by the percent of captures expected in that habitat. Juveniles had a greater proportion of captures In habitat types such as dead spruce, soapberry and t i l l , spruce-moss and closed spruce-soapberry than adults. DISCUSSION Demography I found no evidence of pronounced year-to-year f l u c t u a t i o n in numbers of least chipmunks at Kluane contrary to Callahan (1950) who asserts that wide population fluctuations are t y p i c a l of western chipmunks. This contrasts with Tryon" and Snyder (1973) who reported a 3-4 year population cycle in eastern chipmunks. Their data did not support th e i r claim, however, since peak populations were only 2-3 times the size of the lowest populations. Two demographic studies of Tamias townsendl1 found evidence only of 2- to 3-fold annual fluctuations (Gashwiler,1970; S u l l i v a n et a l , 1983). 29 F i g . 2.5 — H a b i t a t use index f o r a d u l t s and j u v e n i l e s v s . h a b i t a t type. Value of index f o r each h a b i t a t type = % c a p t u r e s observed / % c a p t u r e s expected. 1. Closed spruce soapberry 2. Closed spruce moss 3. Ecotone 4. Open p o p l a r soapberry 5. Dryas f l a t s 6. Open spruce soapberry 7. Dead spruce 8. Open t i l l s o a pberry Habitat Use Index Habitat Use Index 3 1 present study i t i s impossible to t e l l whether chipmunks s e l e c t ecotone, avoid ecotone or are I n d i f f e r e n t to i t . Thi s probably r e f l e c t s a problem with my h a b i t a t c l a s s i f i c a t i o n scheme, r a t h e r than i n d e c i s i o n on the part of chipmunks. R e s u l t s may have been more c o n s i s t e n t l f I had d i v i d e d ecotone f u r t h e r Into c a t e g o r i e s a c c o r d i n g to the h a b i t a t types t h a t bordered i t . Home range The home range s i z e s of l e a s t chipmunks i n the Yukon were 4 to 120 times s i z e of l e a s t chipmunk home ranges i n other areas (Table 2.8). D i f f e r e n t methods used complicate these comparisons, s i n c e the minimum area method and g r i d squares square area method g e n e r a l l y y i e l d s m a l l e r home range estimates than does the minimum convex polygon method used In the present study. In most of these s t u d i e s , capture p o i n t s were s u f f i c i e n t l y clumped that use of the convex polygon method would have added only a f r a c t i o n of the estimated area to the f i g u r e l i s t e d here, so t h i s does not preclude comparison. Sample s i z e p resents more of a problem, s i n c e the methods used here are a l l dependent on sample s i z e . Feldhamer (1979) was the onl y study i n which sample s i z e s were low enough to s e v e r e l y u n d e r e s t i m a l t e home range. In most cases, home range areas l i s t e d are the means f o r a d u l t s only, as i n the present study. For s t u d i e s i n which home range areas were r e p o r t e d d u r i n g the course of an experimental man i p u l a t i o n , home ranges l i s t e d here are f o r the c o n t r o l a r e a . 32 Table 2.8—Chipmunk home ranges from t h i s and previous s t u d i e s STUDY, SPECIES METHOD HOME RANGE LOCATION (ha) B l a i r 1942 Michigan Tamias s t r i a t u s Trapping. Minimum convex polygon (MCP). 0. 90 Broadbrooks 1970 Washington T. amoenus Trapping. No. t r a p s used * t r a p - u n i t a r e a . 1. ,20 Burt 1940 Michigan T. striatus Trapping. MCP. 0. 62 Chappell 1978 C a l i f o r n i a T. T. T. minimus amoenus speciosus Trapping. No. t r a p s used * t r a p - u n i t area. 1. 1. 1. 05 31 39 E l l i o t t 1978 New York T. s t r i a t u s O b s e r vation. No. quad, used * area. 0. 17 Feldhamer 1979 Oregon T. minimus Trapping. Standard diameter. 0. 04 F o r s y t h and Smith 1973, Ont. T. s t r i a t u s T rapping. Minimum area. 0. 18 G l e n n i e , 1988 Yukon T. minimus Telemetry. MCP. 4. 86 Mares et a l 1976, Penn. T. s t r i a t u s T rapping. MCP. 0. 11 Mares et a l 1982, Penn. T. s t r i a t u s Trapping. Minimum area. 0. 09 Martinsen 1968 Montana T. T. minimus amoenus Trapping. MCP. 1. 0. 14 86 Sheppard 1972 A l b e r t a T. T. minimus amoenus Trapping. Minimum area. 0. 0. 85 99 States 1976 Oregon T. amoenus Trapping. Boundary s t r i p . 0. 75 Verger 1953 New York T. striatus Observation and Trapping. MCP. 0. 07 3 3 There have been s e v e r a l attempts to p r e d i c t l i f e - h i s t o r y parameters on the b a s i s of body s i z e (Blueweiss et a l , 1978; Eisenberg, 1981; P e t e r s , 1983; Western, 1979). Much of t h i s work was i n s p i r e d by an e a r l y paper by McNab (1963) i n which he rep o r t e d that home range was r e l a t e d to body mass: A=2.70M0.63 (where area i s expressed i n hec t a r e s , mass i n k i l o g r a m s ) . Mace and Harvey (1983) have d e r i v e d a l l o m e t r i c equations f o r the r e l a t i o n of home range to body s i z e f o r rodents. They separated taxa i n t o three t r o p h i c groups: h e r b i v o r e s , g r a n i v o r e s , and omnivores. Yukon chipmunks are l a r g e l y granivorous so t h e i r p r e d i c t e d home range s i z e ( i n ha) s c a l e s as 0.007M1.12 (where mass i s i n grams). The home range s i z e of Tamlas minimus a t Kluane i s 4.86 ha, 12 times that p r e d i c t e d by McNab's equation f o r a 50 g animal, 0.409 ha, and i t i s 8.8 times that p r e d i c t e d by Mace and Harvey's equation f o r g r a n i v o r e s , 0.56 ha. Examining Table 2.6 r e v e a l s that Tamias does not f o l l o w the a l l o m e t r i c p r i n c i p l e t h at l a r g e r animals should have l a r g e r home ranges. Of a l l the chipmunk s p e c i e s l i s t e d , the e a s t e r n chipmunk, Tamlas strlatus, has the s m a l l e s t home range, but i t i s a l s o the h e a v i e s t (about 100 g ) . Home range s i z e p r e d i c t i o n s from the a l l o m e t r i c equations, 0.63 ha from McNab, 1.23 ha from Mace and Harvey f o r g r a n i v o r e s , g e n e r a l l y exceed the home range s i z e s l i s t e d here. Western chipmunks l i s t e d here have l a r g e r home ranges than t h e i r e a s t e r n congeners, u s u a l l y over 1 ha, but only weigh about 50 g, so that the a l l o m e t r i c equations provide underestimates of home range. These d i s c r e p a n c i e s i n d i c a t e t h a t 34 factors such as l a t i t u d e , food a v a i l a b i l i t y , and population densi ty outweigh the influence of body s i z e . For th i s genus the McNab approach has l i t t l e predic t ive value, and th i s i s l i k e l y to be general ly true at the taxonomic l e v e l of the genus where more de ta i l ed information is needed to account for di f ferences in l i f e - h i s t o r y c h a r a c t e r i s t i c s . SUMMARY I compared demography, habitat choice and home range of a population of least chipmunks at Kluane Lake with previous studies of chipmunks. Population s ize is lower than in most previous studies of th i s and other chipmunk species , but the year-to-year s t a b i l i t y of the population is s imi lar to that found in other chipmunk species . Home range s izes are at least 4 times greater than any reported for the genus. Habitat use comparison with previous studies i s l imited by the fact that they were conducted in d i f f e r e n t habitat at d i s tant locat ions (S ierra Nevada, C a l i f o r n i a ; the centra l Rocky Mountains in A l b e r t a ; and the mountains of Oregon). I found that Yukon chipmunks prefer shrub-land and open forest to closed canopy fores t , which is general ly consistent with the f indings of previous s tudies . 35 There have been s e v e r a l attempts to p r e d i c t l i f e - h i s t o r y parameters on the b a s i s of body s i z e (Blueweiss e t al, 1978; E l s e n b e r g , 1981; P e t e r s , 1983; Western, 1979). Much of t h i s work was i n s p i r e d by an e a r l y paper by McNab (1963) i n which he r e p o r t e d t h a t home range was r e l a t e d to body mass: A = 2 . 7 0 M ° - * a (where area i s expressed i n h e c t a r e s , mass i n k i l o g r a m s ) . Mace and Harvey (1983) have d e r i v e d a l l o m e t r i c e q uations f o r the r e l a t i o n of home range t o body s i z e f o r r o d e n t s . They s e p a r a t e d taxa i n t o three t r o p h i c groups: h e r b i v o r e s , g r a n l v o r e s , and omnivores. Yukon chipmunks are l a r g e l y g r a n l v o r o u s so t h e i r p r e d i c t e d home range s i z e ( i n ha) s c a l e s as 0.007M 1- 1* (where mass i s i n grams). The home range s i z e of Tamias minimus a t Kluane i s 4.86 ha, 12 times t h a t p r e d i c t e d by McNab's e q u a t i o n f o r a 50 g animal, 0.409 ha, and I t i s 8.8 times t h a t p r e d i c t e d by Mace and Harvey's equation f o r g r a n l v o r e s , 0.56 ha. Examining Table 2.6 r e v e a l s t h a t Tamias does not f o l l o w the a l l o m e t r i c p r i n c i p l e t h a t l a r g e r animals should have l a r g e r home ranges. Of a l l the chipmunk s p e c i e s l i s t e d , the e a s t e r n chipmunk, Tamias strlatus, has the s m a l l e s t home range, but i t i s a l s o the h e a v i e s t (about 100 g ) . Home range s i z e p r e d i c t i o n s from the a l l o m e t r i c e q u a t i o n s , 0.63 ha from McNab, 1.23 ha from Mace and Harvey f o r g r a n l v o r e s , g e n e r a l l y exceed the home range s i z e s l i s t e d here. western chipmunks l i s t e d here have larger home ranges than t h e i r e a s t e r n congeners, u s u a l l y over 1 ha, but o n l y weigh about 50 g, so t h a t the a l l o m e t r i c equations p r o v i d e underestimates of home range. These d i s c r e p a n c i e s i n d i c a t e t h a t 36 f a c t o r s such as l a t i t u d e , food a v a i l a b i l i t y , and p o p u l a t i o n d e n s i t y outweigh the Inf l u e n c e of body s i z e . For t h i s genus the McNab approach has l i t t l e p r e d i c t i v e v a l u e , and t h i s i s l i k e l y t o be g e n e r a l l y t r u e a t the taxonomlc l e v e l of the genus where more d e t a i l e d i n f o r m a t i o n i s needed to account f o r d i f f e r e n c e s i n l i f e - h i s t o r y c h a r a c t e r i s t i c s . SUMMARY I compared demography, h a b i t a t c h o i c e and home range o£ a p o p u l a t i o n of l e a s t chipmunks a t Kluane Lake with p r e v i o u s s t u d i e s of chipmunks. P o p u l a t i o n s i z e i s lower than i n most p r e v i o u s s t u d i e s of t h i s and other chipmunk s p e c i e s , but the yea r - t o - y e a r s t a b i l i t y of the p o p u l a t i o n i s s i m i l a r to t h a t found i n other chipmunk s p e c i e s . Home range s i z e s are a t l e a s t 4 times g r e a t e r than any r e p o r t e d f o r the genus. H a b i t a t use comparison wi t h p r e v i o u s s t u d i e s i s l i m i t e d by the f a c t t h a t they were conducted i n d i f f e r e n t h a b i t a t a t d i s t a n t l o c a t i o n s ( S i e r r a Nevada, C a l i f o r n i a ; the c e n t r a l Rocky Mountains l n A l b e r t a ; and the mountains of Oregon). I found t h a t Yukon chipmunks p r e f e r s h r u b - l a n d and open f o r e s t to c l o s e d canopy f o r e s t , which i s g e n e r a l l y c o n s i s t e n t with the f i n d i n g s of pr e v i o u s s t u d i e s . 37 CHAPTER 3: SPACE USE AND SOCIAL STRUCTURE IN THE LEAST CHIPMUNK INTRODUCTION T h i s chapter d i s c u s s e s the e f f e c t s of s o c i a l s t r u c t u r e on the use of space i n a p o p u l a t i o n of l e a s t chipmunks (Tamlas minimus) i n the southwest Yukon. chipmunk p o p u l a t i o n s e x h i b i t s t a b i l i t y (Chapter 2) compared to p o p u l a t i o n s of other s m a l l rodents which e x p e r i e n c e marked m u l t i - a n n u a l f l u c t u a t i o n s ( T a l t t and Krebs, 1985). For example, l n my s t u d y a r e a , Clethzlonomys r u t i l u s and M l c r o t u s pennsylvanlcus f l u c t u a t e w i d e l y i n numbers (Krebs and Wingate, 1985). S o c i a l s p a c i n g has long been a s s o c i a t e d with the r e g u l a t i o n of p o p u l a t i o n d e n s i t y (Calhoun, 1949; Wynne-Edwards, 1962; Watson and Moss, 1970). S o c i a l I n t e r a c t i o n s a f f e c t i n g space use can l i m i t an animal's a c c e s s to food, s h e l t e r , mates, t r a v e l r o u t e s , or bar i t c o m p l e t e l y from c e r t a i n a r e a s . E x p l a n a t i o n s based on s p a c i n g behaviour have been used to e x p l a i n both c y c l i c ( C h r i s -t i a n , 1950; C h i t t y , 1967) and s t a b l e p o p u l a t i o n s (Healy, 1967). T h i 3 study s e t out to e s t a b l i s h i f , and i n what form s o c i a l s p a c i n g occurs i n the l e a s t chipmunk a t Kluane Lake. Three types of s o c i a l s p a c i n g were c o n s i d e r e d : t e r r i t o r i a l i t y , s p a c e - r e l a t e d dominance and encounter avoidance. These types of s o c i a l s t r u c t u r e have each been p r e v i o u s l y documented f o r Tamlas. Of these t h r e e t y p e s , t e r r i t o r i a l i t y Is the most r e s t r i c -t i v e . In a t e r r i t o r i a l system, animals have f i x e d , defended core areas from which o t h e r s are excluded. D e f i n i t i o n s of t e r -38 r i t o r i a l i t y vary, emphasizing e i t h e r e x c l u s i v e occupancy (e.g. P i t e l k a , 1959; Schoener, 1968) or defense (Noble, 1939). In s t u d i e s of Tamias s t r i a t u s , Burt (1940), Yerger (1953), and Yahner (1978) claim e d t h a t these chipmunks were t e r r i t o r i a l . Broadbrooks (1970) found evidence of t e r r i t o r i a l behaviour i n Tamias amoenus, and Brand(1976) suggested t e r r i t o r i a l i t y was t y p i c a l f o r western chipmunks. S p a c e - r e l a t e d dominance i s s i m i l a r to t e r r i t o r i a l i t y , but an e x c l u s i v e l y defended core area i s l a c k i n g . I n d i v i d u a l s do not p a t r o l t e r r i t o r i e s and exclude a l l i n t r u d e r s , but are dominant i n a g o n i s t i c i n t e r a c t i o n s w i t h i n t h e i r core areas and have p r i o r a c c e s s t o r e s o u r c e s t h e r e . Numerous s t u d i e s on chipmunks (e.g. Dunford, 1970; E l l i o t t , 1978) have r e p o r t e d the e x i s t e n c e of t h i s s o c i a l system. Encounter avoidance was f i r s t documented i n chipmunks by Get t y (1981). Space i s p a r t i t i o n e d In time, e i t h e r by s p a c i n g a t r e g u l a r i n t e r v a l s a t a g i v e n time, or by maintenance of a minimum d i s t a n c e between neighbours. Spacing i s not a c t i v e l y maintained by a g g r e s s i v e behaviour, but by a v o i d i n g i n t e r a c t i o n s . I t e s t e d to see which of these 3 systems of space use a p p l i e d to the l e a s t chipmunk at Kluane Lake. T e r r i t o r i a l animals w i l l have home ranges with minimal o v e r l a p and m a i n t a i n n o n - o v e r l a p p i n g core a r e a s . A s y s t e m a t i c m o n i t o r i n g of home ranges would be s u f f i c i e n t to d e t e c t t h i s . S p a c e - r e l a t e d dominance does not p r e d i c t e x c l u s i v e core a r e a s , but p r e d i c t s a g g r e s s i v e defense of core a r e a s . Encounters 39 should r e s u l t i n a g o n i s t i c i n t e r a c t i o n s i n which dominance i s determined by the l o c a t i o n of the encounter. T h i s p r e d i c t i o n can be t e s t e d by o b s e r v i n g and comparing outcomes of i n t e r a c t i o n s a t d i f f e r e n t l o c a t i o n s on the study s i t e . Encounter avoidance p r e d i c t s t h a t encounters w i l l be l e s s f r e q u e n t than would be expected based on the degree of home range o v e r l a p and random movement w i t h i n home ranges. T h i s can be t e s t e d by comparing the frequency of encounters measured by t e l e m e t r y with encounter frequency from a s i m u l a t i o n model c o n s t r u c t e d u s i n g r e a l home range parameters and random movement p a t t e r n s . I d e f i n e an encounter as an event i n which two chipmunks are c l o s e enough to each other t h a t each Is aware of the presence of the o t h e r . In my a n a l y s i s I used an encounter r a d i u s of 30 m. An encounter does not n e c e s s a r i l y i n v o l v e a s o c i a l I n t e r a c t i o n . METHODS The study a r e a , t r a p p i n g and t e l e m e t r y techniques were d e s c r i b e d l n Chapter 2. From the t e l e m e t r y and r e c a p t u r e data I c a l c u l a t e d the home range area and o v e r l a p f o r each animal u s i n g the minimum convex polygon method (Southwood, 1966, p.262). T h i s method i s simple to use, s t a t i s t i c a l l y s t a b l e ( J e n n r i c h and Turner, 1969) and f a c i l i t a t e s comparison w i t h p r e v i o u s s t u d i e s . 40 Behavioural observation During the summer of 1985 I investigated the occurrence and rates of behavioural inte r a c t i o n s . Population density and a c t i v i t y l e v e l s of chipmunks were too low for natural i n t e r a c t i o n rates to provide s u f f i c i e n t data to assess spacing behaviour. I therefore provoked interactions by placing p i l e s of sunflower seeds at s i t e s spaced systematically over the grids in open areas where chipmunk a c t i v i t y was highest. From a distance of 5 m I observed interactions among pelage-marked chipmunks which were attracted to the seed p i l e s . Observations were divided into bouts. A bout began when two or more chipmunks began an i n t e r a c t i o n , and ended when one or more of them was displaced, or when a new animal appeared. For each bout the i d e n t i t i e s of the p a r t i c i p a n t s were recorded and the bout was scored as either a win-loss, a draw, or tolerance. A win-loss was defined as an i n t e r a c t i o n in which the winner displaced the loser from the seed p i l e by means of aggressive behaviours such as threats, lunges, chases and f i g h t s . Similar behaviours have been described by Aniskowicz and Vaillancourt (1979) for the eastern chipmunk. A draw occurred when animals behaved aggressively but neither displaced the other. Tolerance occurred when animals showed no aggressive behaviour, but behaved amicably or ignored each other. 41 Encounter avoidance In 1986 t e l e m e t r y was used to determine whether animals were a v o i d i n g encounters. A c t u a l encounter f r e q u e n c i e s were compared with encounter f r e q u e n c i e s generated by a s i m u l a t i o n model of random movement w i t h i n home ranges (program l i s t i n g i n Appendix 1 ) . I obtained e s t i m a t e s of encounter frequency from the telem-e t r y data u s i n g sampling windows 90 minutes l n l e n g t h . In each sampling window d i s t a n c e s among p o s i t i o n s of a l l animals are c a l c u l a t e d and compared a g a i n s t an encounter r a d i u s of 30 m. A l l in t e r - n e i g h b o u r d i s t a n c e s up t o 30 m are c l a s s i f i e d as en-c o u n t e r s . The t e l e m e t r y data do not p r o v i d e t r u l y simultaneous p o s i t i o n a l e s t i m a t e s f o r a l l animals. Since the average e l a p s e d time between l o c a t i o n s of animals l n encounters i s 15 minutes, I do not c o n s i d e r t h i s problem to be s e r i o u s . The number of animals wearing r a d i o - c o l l a r s a t the same time on the same g r i d v a r i e d from 0 to 9. In t h i s a n a l y s i s I used o n l y sampling windows l n which four or more animals c a r r i e d t r a n s m i t t e r s . For t h i s reason I used o n l y the g r i d H t e l e m e t r y d a t a . Due to the shortage of f u n c t i o n i n g r a d i o - c o l l a r s , t h e r e were r a r e l y more than 4 chipmunks on g r i d X equipped w i t h t r a n s m i t t e r s a t the same time. The random model (which generates encounter data t o compare with a c t u a l encounter r a t e s ) u t i l i z e s the f o l l o w i n g home range a t t r i b u t e s from the a c t u a l d a t a . For each chipmunk whose movement i s s i m u l a t e d , p o s i t i o n s of nest s i t e and c e n t r e of 4 2 a c t i v i t y were obtained from the t r a p p i n g and t e l e m e t r y d a t a . The model a l s o uses v a l u e s f o r maximum d i s t a n c e from c e n t r e of a c t i v i t y , time a c t i v e above ground, and p r o b a b i l i t y of changing l o c a t i o n t h a t were d e r i v e d from the d a t a . Computer generated l o c a t i o n data were mapped on the same c o o r d i n a t e system as the stu d y g r i d s t o f a c i l i t a t e comparison. The a l g o r i t h m used i n the model i s I l l u s t r a t e d i n f i g u r e 3.1. I n i t i a l input i n c l u d e s the number and i d e n t i t y of chipmunks sampled and the month. When the run begins, each animal d e c i d e s whether or not to move ( p r o b a b i l i t y i s 50%). i f i t moves i t le a v e s i t s nest s i t e and moves 1 g r i d c o o r d i n a t e (15 m) In a randomly chosen d i r e c t i o n : any of 360 degrees. Simulated chipmunks remain w i t h i n the s p e c i f i e d maximum d i s t a n c e from c e n t r e of a c t i v i t y (180 m f o r males, 90 m f o r f e m a l e s ) ; movements beyond t h i s boundary are preempted, and a new d i r e c t i o n randomly chosen t h a t keeps the animal w i t h i n i t s maximum d i s t a n c e . T h i s process repeats u n t i l the end of each time i n t e r v a l , when the d i s t a n c e s among a l l chipmunk p o s i t i o n s i n the model are c a l c u -l a t e d . These d i s t a n c e s are compared with the s p e c i f i e d encounter r a d i u s to determine the number of s i m u l a t e d encounters. Each run s i m u l a t e s one day's a c t i v i t y . The number of encounters generated f o r the p e r i o d t h a t corresponds to the sampling window can then be compared with number of encounters recorded i n the f i e l d . 43 Flowchart of random-encounter simulation model. # of chipmunks chipmunk identities Define: -naat alt«« -aotlvlty centra -max. rang* month i length of active day t snapshot interval set time start day c h o o s e d i rect ion calc. new location start from nest sites relocate — 1 encounter radius number of encounters encounter statistics stop 45 RESULTS Home range overlap Home range overlap between neighbours was determined by measuring the percentage of s p a t i a l overlap of convex polygons. I calculated overlap separately using the trapping and telemetry data. For the trapping data, a l l chipmunks with more than 5 non-li n e a r recaptures were Included in c a l c u l a t i o n of home range overlap. Five captures is seldom s u f f i c i e n t to y i e l d accurate estimates of home range area, but including these home ranges in the overlap analysis gives a better i n d i c a t i o n of the degree of crowding than could be obtained by excluding them. According to trap-based estimates of home range, mean home range overlap was 94.3% for a l l animals combined. Each home range was overlapped by an average of 14.9 others (Table 3.1). Overlap on female home ranges by other females averaged 75.1%; th i s does not d i f f e r s i g n i f i c a n t l y from male-male home range overlap, 70.4 %. Male home ranges were overlapped by more male neighbours than female home ranges are overlapped by female neighbours (6.5 vs.4.0). This i s consistent with the male-biased sex r a t i o . The telemetry-based estimate of home range overlap was 86.8% 46 f o r a l l I n d i v i d u a l s combined, lower than the trap-based e s t i m a t e , s i n c e not a l l animals were r a d i o e d . In terms of i n t e n s i t y of use, the amount of home range o v e r l a p r e v e a l e d by t e l e m e t r y was s u b s t a n t i a l l y higher than 86.8%. W i t h i n a chipmunk home range, the area which does not o v e r l a p with any neighbouring home range c o n t a i n s an average of o n l y 8% of the "owner's" r a d i o - l o c a t i o n s . These e x c l u s i v e areas do not, t h e r e f o r e , correspond t o core a r e a s , as a core a r e a Is g e n e r a l l y understood to be the p a r t of i t s range which the animal f r e q u e n t s the most. Telemetry-based home range maps are presented i n F i g u r e s 3.2 and 3.3. Table 3.1—Mean home range o v e r l a p SOURCE PERIOD PERCENT OVERLAP NO. NEIGHBOURS OVERLAPPED ALL F M ALL F M Trap 2.5 mo. 94.3 75.1 70.4 14.9 4.0 6.5 Telem 4.5 mo. 86.8 65.2 82.0 6* 3* 5.2* Telem 12 May-10 June 80.1 60.0 73.6 5* 2.5* 4.7* Telem 11 Jun-20 J u l y 76.2 52.0 76.0 5* 2.5* 5* Telem 21 J u l -12 Sept 83.0 62.6 78.8 6* 3* 5* Home range s h i f t s o c c u r r e d between May and the end of September, e s p e c i a l l y among females t h a t had j u s t f i n i s h e d weaning t h e i r young. I t h e r e f o r e d i v i d e d a l l of the t e l e m e t r y data i n t o three p e r i o d s based on female b r e e d i n g c o n d i t i o n : p r e -47 F i g . 3.2 — T e l e m e t r y - b a s e d home range map of G r i d H.. C o o r d i n a t e s from 1 to 37 on the y - a x l s and from 1-29 on the x - a x i s are w i t h i n the g r i d boundaries. One g r i d coordlnate=15 m. 49 F i g . 3.3 --Telemetry-based home range map of G r i d X. C o o r d i n a t e s from 1 to 29 on both axes are w i t h i n g r i d boundaries. One g r i d coordlnate=15 m. X 51 l a c t a t i n g (May 12 to June 10), l a c t a t i n g (June 11 to J u l y 20) and p o s t - l a c t a t i n g ( J u l y 21 to September 12). Home range o v e r l a p i s l e s s d u r i n g these d i s c r e t e p e r i o d s than when c a l c u l a t e d over the e n t i r e f i e l d season, but even f o r l a c t a t i n g females, who were most o f t e n l o c a t e d near t h e i r n e st s i t e s , o v e r l a p i s always g r e a t e r than 50%. B e h a v i o u r a l o b s e r v a t i o n B e h a v i o u r a l o b s e r v a t i o n s d u r i n g the summer of 1985 began a f t e r the mating season and p r o v i d e d i n t e r a c t i o n data on 35 chipmunks, 14 of them on g r i d H, the other 21 on g r i d X. During 240 hours of o b s e r v a t i o n , 353 bouts were r e c o r d e d , of which 315 (89%) were a g g r e s s i v e . Each bout i n v o l v e d two animals, so t h a t an average of twenty bouts were reco r d e d f o r each a n i m a l . Bach animal i n t e r a c t e d with an average of 6 neighbours. Thus, even i f i n t e r a c t i o n s were d i v i d e d e v e n l y among neighbours, the t o t a l of 353 bouts r e c o r d e d would y i e l d o n l y 3.3 bouts per p a i r of neighbours. The da t a o b t a i n e d a re t h e r e f o r e too sp a r s e t o document dominance r e v e r s a l s f o r each i n d i v i d u a l with i t s neighbours. However, the r e l a t i o n s h i p between dominance and l o c a t i o n can be e x p l a i n e d by l o o k i n g a t the data on a bout-by-bout b a s i s . For a l l w i n - l o s s bouts, t h e r e was no s i g n i f i c a n t d i f f e r e n c e between winners and l o s e r s l n the mean d i s t a n c e from the l o c a t i o n a t which the i n t e r a c t i o n o c c u r r e d t o the c e n t r e of the p a r t i c i p a n t ' s home range on e i t h e r g r i d ( g r i d X, p a i r e d samples t = 1.32, p = .19, df = 109; g r i d H, p a i r e d samples t = .41, p = .68, df = 162). Nor was t h e r e any s i g n i f i c a n t d i f f e r e n c e when the same a n a l y s i s was repeated f o r d i s t a n c e from i n t e r a c t i o n l o c a t i o n t o nest s i t e (nest s i t e s were known f o r 19 chipmunks). Using data from both g r i d s , p a i r e d samples t = .67, p =.51, df = 220 (Table 3.2). Table 3.2—Mean d i s t a n c e s from I n t e r a c t i o n to home GRID CATEGORY MEAN DISTANCE IN METERS (SD) WINNERS LOSERS X home=centre 87.6(83.75) 79.2(49.61) home=nest 91.1(57.32) 95.1(44.72) H home=centre 72.7(53.18) 75.8(51.00) home=nest 85.1(55.71) 89.3(48.11) Only bouts between animals r e s i d e n t on the g r i d where the encounter occ u r r e d were i n c l u d e d i n the p r e v i o u s a n a l y s i s , s i n c e e s t i m a t e s of burrow s i t e s and home range c e n t r e s were u n a v a i l a b l e f o r n o n - r e s i d e n t s . Twenty-eight bouts (8% of the t o t a l ) o c c u r r e d between r e s i d e n t s and no n - r e s i d e n t i n t r u d e r s . Twenty-four of these r e s u l t e d from unprovoked i n t e r a c t i o n s and i n c l u d e d the o n l y i n s t a n c e s of f i g h t i n g t h a t I witnessed over the e n t i r e season. The i n t r u d e r s won o n l y 7 of the 28 encounters. T h i s frequency d i f f e r s s i g n i f i c a n t l y from the frequency expected i f i n t r u d e r s were as l i k e l y to dominate i n i n t e r a c t i o n s as r e s i d e n t s (Xs* = 7.0, p < 0.01, df = 1). Bouts with I n t r u d e r s were u s u a l l y 53 i n i t i a t e d by r e s i d e n t s t h a t were s u b o r d i n a t e to other r e s i d e n t s on the g r i d . Of the bouts l o s t by i n t r u d e r s , 71% were l o s t t o non-breeding animals which were l i g h t e r than the I n t r u d e r s . For a l l w i n - l o s s bouts, the mean weight of winners (50.9 g) was s l i g h t l y but s i g n i f i c a n t l y h igher than the mean weight of l o s e r s (49.3 g, t = 3.43, p = .001, df = 314). Chi-square t e s t s were used to determine whether sex, age, and bre e d i n g c o n d i t i o n were r e l a t e d t o dominance. The sex of the p a r t i c i p a n t s d i d not a f f e c t the outcome of i n t e r a c t i o n s ( X a = .72, p = .40, df = 1 ) . A d u l t s won i n a l l a g g r e s s i v e i n t e r a c t i o n s with j u v e n i l e s ( X a = 19.37, p < .001, df = 1) which tended to be more a g g r e s s i v e than i n t e r a c t i o n s with other a d u l t r e s i d e n t s . The e f f e c t s of b r e e d i n g c o n d i t i o n were a n a l y z e d o n l y f o r females, s i n c e most b e h a v i o u r a l o b s e r v a t i o n took p l a c e a f t e r May 20, a t which p o i n t males were not i n bre e d i n g c o n d i t i o n . Breeding females won s i g n i f i c a n t l y more i n t e r a c t i o n s than females which never bred ( X a = 15.51, p < .001, df = 2). Bouts i n v o l v i n g b r e e d i n g females were d i v i d e d i n t o 3 c a t e g o r i e s a c c o r d i n g to whether they were pregnant,' l a c t a t i n g , or p o s t - l a c t a t i n g . L a c t a t i n g females won i n t e r a c t i o n s more o f t e n than pregnant and p o s t - l a c t a t i n g females (X a=5.12, p<.025, d f = l ) . Encounter avoidance I f encounter avoidance o c c u r s , i t s h o u l d be most apparent while females are l a c t a t i n g , s i n c e t h e i r movements are more 54 r e s t r i c t e d and they win a greater proportion of interactions at that time. Therefore, encounter frequencies during p r e - l a c t a t -ing, l a c t a t i n g , and post - l a c t a t i n g periods were compared separat-e l y with the model's output. The r e s u l t s are presented in Table 3.3. For the pre - l a c t a t i n g and l a c t a t i n g periods, encounter frequency was s i g n i f i c a n t l y less than that generated by the random model, so the samples were pooled (t=2.41, p = .02, df=45). For the post - l a c t a t i n g period, encounter frequency did not d i f f e r s i g n i f i c a n t l y from the model (t=1.30, p=0.20, df=42). Table 3.3—Mean encounter frequency on g r i d H vs. simulation PERIOD MEAN ENCOUNTERS MEAN ENCOUNTERS GENERATED Pre - l a c t a t i n g 0.48 1.16 Lactating 0.86 1.19 Po s t - l a c t a t i n g 1.37 1.23 DISCUSSION From the home range data presented here, the hypothesis that least chipmunks at Kluane Lake are t e r r i t o r i a l can be conclusive-l y rejected. Both trap and telemetry-based estimates of home range overlap demonstrate that exclusive core areas do not e x i s t . 55 T e r r i t o r i a l i t y can also be rejected using Noble's (1939) d e f i n i -t i o n of t e r r i t o r y , which emphasizes defense rather than ex-c l u s i v i t y as diagnostic of t e r r i t o r i a l i t y . Home ranges are too large to be pa t r o l l e d and defended. Intensive use i s centred on the same grid areas for a l l animals whose home ranges overlap these areas; they cannot be defending core areas. The absence t e r r i t o r i a l i t y ln Tamlas minimus at Kluane Lake does not s p e c i f i c a l l y contradict previous studies. T e r r i t o r i a l -i t y ln chipmunks has been reported for dense populations of Tamlas s t r l a t u s and Tamlas amoenus. The s o c i a l system of the least chipmunk has never been s p e c i f i c a l l y examined, previous studies have considered agonistic behaviour in least chipmunks only ln order to evaluate the importance of competition among species of western chipmunks (Heller, 1971; Sheppard, 1971; States, 1976; Chappell, 1978). L i t t l e evidence was found for space-related dominance. Soc i a l dominance appears to be based on Individual c h a r a c t e r i s -t i c s such as size and age rather than ownership of space. Size, age and breeding condition are t y p i c a l l y related to dominance ln studies of s o c i a l dominance that lack any s p a t i a l component. An exception to the apparently space-independent pattern of s o c i a l dominance was evident in the Interactions between residents and non-residents. Non-residents were generally heavier than the residents which defeated them, which i s contrary to the trend reported above. Three of the intruders were resident on another g r i d where each of them was s o c i a l l y dominant. These three 57 t o t a l . There i s another f a c t o r which c a s t s doubt on the a p p a r e n t l y a g o n i s t i c s o c i a l s t r u c t u r e r e v e a l e d here. S i x of the l o c a t e d n e s t s were w i t h i n 15 m of another chipmunk n e s t . In a d d i t i o n , a group of three males were r e p e a t e d l y observed s h a r i n g a nest, as were a male and female p a i r a f t e r j u v e n i l e s were weaned a t the end of August. These animals behaved amicably while s h a r i n g n e s t s , y e t i n t e r a c t e d a g g r e s s i v e l y a t seed p i l e s on the g r i d s . Brown (1964) suggested t h a t t e r r i t o r i a l behaviour i s o n l y a d a p t i v e where the c o n t e s t e d r e s o u r c e i s d i s t r i b u t e d so t h a t i t i s e c o n o m i c a l l y d e f e n d a b l e . My sunflower seed p i l e s c o n s t i t u t e d a r i c h , d i s c r e t e , defendable r e s o u r c e , and t h e i r presence r e s u l t e d i n behaviours which were not t y p i c a l of the normal behaviours of chipmunks a t Kluane. In August 1986, chipmunks were f r e q u e n t l y observed f e e d i n g on s e a s o n a l l y abundant Shepher-d i a b e r r i e s a t i n t e r - i n d i v i d u a l d i s t a n c e s of l e s s than t h r e e meters without any s i g n of a g g r e s s i v e behaviour. In 1985, i n t e r -i n d i v i d u a l d i s t a n c e s of 7 m a t seed p i l e s were o f t e n s u f f i c i e n t to provoke a g g r e s s i v e i n t e r a c t i o n s . P r e v i o u s s t u d i e s of chipmunk s o c i a l behaviour t h a t have r e p o r t e d a g g r e s s i v e l y maintained s p a c i n g mechanisms, e s p e c i a l l y s t u d i e s of western chipmunks, have r e l i e d e i t h e r on l a b t r i a l s or provoked i n t e r a c t i o n s . I b e l i e v e t h a t a g g r e s s i v e l y maintained s o c i a l s p a c i n g was absent a t Kluane f o r the reasons g i v e n above. However, the r e l a t i o n s h i p between the frequency of a r t i f i c i a l l y provoked i n t e r a c t i o n s and n a t u r a l l y o c c u r r i n g i n t e r a c t i o n s needs 5 8 to be s t u d i e d b e f o r e t h i s c o n c l u s i o n s can be confirmed. On the b a s i s of the d i f f e r e n c e between encounter r a t e s i n the data and the random model, I conclude t h a t encounter a v o i d a -nce o c c u r r e d . The comparison i s l i m i t e d by the f a c t t h a t the data were not gathered s i m u l t a n e o u s l y , and by the l e n g t h of the d e f i n e d encounter r a d i u s . Automatic scan sampling would have p r o v i d e d simultaneous d a t a , but f o r an area as l a r g e as an average chipmunk home range, and with the f o r e s t e d h a b i t a t c a u s i n g s i g n a l bounce, t h i s was not f e a s i b l e . These r e s u l t s suggest t h a t the s o c i a l s t r u c t u r e of low-d e n s i t y p o p u l a t i o n s of Tamlas minimus i s determined by e c o l o g i c a l c o n s t r a i n t s such as the r e s t r i c t i o n of movements d u r i n g l a c t a -t i o n , and the n e c e s s i t y of h a r v e s t i n g seasonally-abundant food r e s o u r c e s , r a t h e r than by s p a c e - r e l a t e d I n t e r a c t i o n s . The f a c t t h a t s p a c i n g i n the p o s t - l a c t a t i n g p e r i o d d i d not d i f f e r from random may have r e s u l t e d from chipmunks h a r v e s t i n g Shephezdla b e r r i e s i n the month of August. Mutual t o l e r a n c e while f e e d i n g and the s h a r i n g of nests among a d u l t s i n d i c a t e t h a t n a t u r a l l y o c c u r r i n g a g g r e s s i o n was r e l a t i v e l y r a r e among l e a s t chipmunks a t Kluane. T h i s suggests t h a t encounter avoidance i s maintained p a s s i v e l y . I t i s a l s o p o s s i b l e t h a t observed i n s t a n c e s of amicable behaviour o c c u r r e d among chipmunks which were r e l a t e d to each o t h e r . R e l a t i v e l y h i g h s u r v i v a l r a t e s (Chapter 2) and the l o n g e v i t y of the s p e c i e s (up to 6 years a c c o r d i n g to C r i d d l e , 1943) c o u l d r e s u l t i n a high degree of r e l a t e d n e s s among n e i g h -59 bours. H e l l e r (1971) and S t a t e s (1976) found t h a t l e a s t chipmunks were l e s s a g g r e s s i v e than congeners l i v i n g i n a d j a c e n t h a b i t a t , a l t h o u g h t h i s c o n t r a d i c t e d other s t u d i e s of the same congeners (Sheppard, 1971; C h a p p e l l , 1978). H e l l e r invokes the concept of economic d e f e n d a b i l i t y (Brown, 1964) and suggests t h a t a g g r e s s i v e behaviour i s m e t a b o l I c a l l y i n f e a s l b l e i n the l e a s t chipmunk due t o the p h y s i o l o g i c a l s t r e s s t h a t would ensue i n the sage-brush d e s e r t h a b i t a t the s p e c i e s o c c u p i e s . A g g r e s s i v e behaviour may a l s o have been i n h i b i t e d by c o e x i s t e n c e with l a r g e r and a g g r e s -s i v e l y dominant congeners. I s o l a t e d from c o n g e n e r i c s p e c i e s , l e a s t chipmunks i n the Yukon are near the n o r t h e r n l i m i t of t h e i r range where d i f f e r e n t m e t a b o l i c c o n s t r a i n t s a p p l y . They may have l i t t l e need f o r a g g r e s s i v e l y maintained s p a c i n g behaviour because of t h e i r c o n s t a n t , low, p o p u l a t i o n d e n s i t y , and v e r y l a r g e home ranges. A g g r e s s i v e defense of r e s o u r c e s may i n f a c t be p r o h i b i -ted by the requirement of hoarding s u f f i c i e n t food f o r winter d u r i n g the s h o r t snow-free season. 60 CHAPTER 4: THE INFLUENCE OF GRID-TRAPPING ON SPACE USE AND HOME RANGE IN THE LEAST CHIPMUNK INTRODUCTION T h i s chapter I n v e s t i g a t e s two p o s s i b l e e f f e c t s of g r i d -t r a p p i n g on home range. F i r s t l y , i t asks whether the presence of a t r a p p i n g g r i d changes the a c t u a l home ranges of the animals t h a t l i v e t h e r e . The presence of t r a p s c o u l d i n c r e a s e the a v a i l a b i l i t y of two r e s o u r c e s : food and c o v e r . Are these changes s u f f i c i e n t t o d i s t o r t home range? Secondly, i t asks how t r a p p i n g a f f e c t s the measurement of home range. Does i t p r o v i d e an a c c u r a t e measure of home range compared t o t h a t a f f o r d e d by te l e m e t r y ? C r i t i c i s m s of g r i d - t r a p p i n g as a method f o r home range e s t i m a t i o n a re common (Hayne, 1950; Sanderson and Sanderson, 1964; Banks et a l , 1975; C r a n f o r d , 1977), but p o i n t s of c r i t i c i s m are c o n f i n e d to p r o p e r t i e s of g r i d - t r a p p i n g such as low numbers of r e c a p t u r e s , the amount of time r e q u i r e d t o accumulate s u f f i -c i e n t c a p t u r e s , assumptions about t r a v e l d i s t a n c e between t r a p s and l a c k of continuous d a t a . Home range i s o f t e n underestimated by g r i d - t r a p p i n g because g r i d s are not s u f f i c i e n t l y l a r g e to c o n t a i n the movements of animals t h a t i n h a b i t them (Broome and McMahon, 1986). These a s p e c t s of g r i d - t r a p p i n g a f f e c t the measurement of home range r a t h e r than the home range i t s e l f . 61 P r e v i o u s s t u d i e s o£ chipmunk home range, e s p e c i a l l y exper-imental s t u d i e s (Mares e t a l . , 1 9 7 6 ; Mares et a l . , 1982; S u l l i v a n e t a l , 1983; Lack! e t a l , 1984; Trombulak, 1 9 8 5 ) , have g e n e r a l l y employed t r a p p i n g to estimate home range. The value of such s t u d i e s would be s e v e r e l y compromised i f t h e i r methodologies a f f e c t the v e r y parameter they are intended to measure. My own o b s e r v a t i o n s from the summer of 1985 suggest t h a t t r a p p i n g and l e a v i n g t r a p s p r e - b a l t e d between s e s s i o n s added enough food or cover to the chipmunks' environment t o a f f e c t movement p a t t e r n s . I r e p e a t e d l y observed animals " t r a p - l i n i n g " ( v i s i t i n g one t r a p a f t e r another a l o n g a g r i d row, f i l l i n g cheek pouches with b a i t and bedding, and pausing o n l y to s c a t t e r - h o a r d as t h e i r pouches f i l l e d ) both d u r i n g and between . t r a p p i n g s e s s i o n s , and found t h a t i t was g e n e r a l l y e a s i e r to a t t r a c t chipmunks t o food p i l e s p l a c e d at t r a p - s t a t i o n s than elsewhere. P r e d i c t i o n s P r o v i d i n g supplemental food to s m a l l mammal home ranges i s g e n e r a l l y thought to decrease home range a r e a . Numerous c o r r e l a -t i v e s t u d i e s have shown a neg a t i v e r e l a t i o n s h i p between food a v a i l a b i l i t y and home range s i z e ( B l a i r , 1 943; O ' F a r r e l l e t a l . , 1 9 7 5 ) , and food a d d i t i o n experiments have r e s u l t e d i n home range r e d u c t i o n s (Mares e t a l . , 1976; T a i t t e t a l . , 1 9 8 1 ) . I f g r i d -t r a p p i n g i s e q u i v a l e n t t o s m a l l s c a l e food a d d i t i o n , t e l e m e t r y -r e v e a l e d home range areas should decrease a f t e r g r i d - t r a p p i n g i s 62 I n s t i t u t e d on an ar e a , and i n c r e a s e a f t e r g r i d - t r a p p i n g c e a s e s . Another p o s s i b l e response t o g r i d - t r a p p i n g i s a s h i f t or expansion of home ranges to i n c l u d e areas s u p p l i e d with t r a p s t h a t were not p r e v i o u s l y w i t h i n those home ranges. T h i s p r e d i c t s immigration onto t r a p p i n g g r i d s and home range s h i f t s inward from the edge of the g r i d w h ile the g r i d i s o p e r a t i n g . Animals t h a t l i v e on the g r i d area should respond to g r i d -t r a p p i n g with a change i n use d i s t r i b u t i o n . Once t r a p p i n g has begun, animals on the g r i d p e r i p h e r y should use the f o o d - e n r i c h e d p a r t of t h e i r home range, the p a r t which o v e r l a p s the g r i d , more I n t e n s i v e l y than the p a r t which does not. I f t r a p - l i n i n g i s o c c u r r i n g , then animals i n s i d e the g r i d s h o u l d be l o c a t e d near t r a p s t a t i o n s more f r e q u e n t l y than would be expected by chance. METHODS Procedures used i n the c o l l e c t i o n of t r a p p i n g and t e l e m e t r y data have been d e s c r i b e d e x t e n s i v e l y i n pr e v i o u s c h a p t e r s and w i l l not be repeated here. E x p e r i m e n t a l d e s i g n In A p r i l 1986 two 18 ha g r i d s , a p p r o x i m a t e l y 1 km a p a r t , were surveyed i n s i m i l a r h a b i t a t . From e a r l y May to mid-July, g r i d H (the southernmost g r i d ) was operated as a t r a p p i n g g r i d . On J u l y 16, I removed a l l t r a p s from g r i d H and t r a n s f e r r e d them 63 to g r i d X (the northern g r i d ) . From mid-July to late September, g r i d X alone was treated as a trapping g r i d (Figure 2.1, Table 2.1). I used radio-telemetry to monitor home ranges of resident adults throughout the summer. On each g r i d , trapping was used as a treatment, and home range sizes during the non-trapping period were taken as control values for that g r i d . The sequence of treatment and control were reversed on gr i d X with respect to g r i d H ln order to account for seasonal e f f e c t s . Chipmunk home ranges are known to vary according to season, e s p e c i a l l y for females, whose movements are r e s t r i c t e d during l a t e pregnancy and e a r l y l a c t a t i o n (Martinsen, 1968; Broadbrooks, 1970). If grid-trapping e f f e c t s on food a v a i l a b i l i t y determine home range s i z e , g r i d H residents should have smaller home ranges in e a r l y summer than in late summer, while for g r i d X residents the reverse should be true. If seasonal e f f e c t s determine home range si z e then seasonal changes in home range si z e should be consistent for both grids. R e s t r i c -t i o n of movements during l a c t a t i o n would r e s u l t in larger home ranges in late than in early summer on both gri d s . Home range c a l c u l a t i o n s Home range s i z e was calculated using the minimum convex polygon method (Southwood, 1966). It is well-known that the minimum convex polygon (MCP) increases with sample size u n t i l i t reaches an asymptote at the actual home range si z e (Stlckel,1954; 64 J e n n r i c h and Turner, 1 9 6 9 ) . Mares et a l . ( 1 9 8 0 ) showed t h a t f o r the e a s t e r n chipmunk, home range area l e v e l l e d o f f a f t e r 20 c a p t u r e s . T h e r e f o r e , In order to s t a n d a r d i z e home range measure-ments to sample s i z e , I used MCP c a l c u l a t e d a t 20 r a d i o l o c a t i o n s f o r a l l comparisons. For a l l r a d i o - c o l l a r e d chipmunks i n t h i s s t u d y an average of 8 7 . 1 8 % (SD=13.96) of home range i s r e v e a l e d a f t e r 20 l o c a t i o n s . In the m a j o r i t y of s t u d i e s f o r which such e s t i m a t e s are c a l c u l a t e d , 9 0 % or 9 5 % home range i s used. I c a l c u l a t e MCP a f t e r 20 ca p t u r e s i n s t e a d of a t 9 0 % home range because I used Mares e t a l . ( 1 9 8 0 ) e s t i m a t e f o r the home range l i m i t as a f i e l d t a r g e t f o r minimum number of l o c a t i o n s . For most animals I c o l l e c t e d more than 20 l o c a t i o n p o i n t s i n each p a r t of the summer, but due to l o g i s t i c problems I c o u l d o n l y c o l l e c t the minimum number of l o c a t i o n s i n some ca s e s . I chose not to exclude these from the a n a l y s i s . E f f e c t of data source on home range e s t i m a t e In order t o compare trap-based home range e s t i m a t e s with telemetry-based e s t i m a t e s , MCP c a l c u l a t e d u s i n g the f i r s t 20 l o c a t i o n p o i n t s i s used as above. S i n c e , f o r each chipmunk, t r a p p i n g data o n l y e x i s t f o r h a l f of the summer, trap-based e s t i m a t e s are compared with t e l e m e t r y data c o l l e c t e d d u r i n g the same p e r i o d ( e a r l y or l a t e summer). RESULTS Ef f e c t s of grid-trapping on home range Table 4.1 presents the mean telemetry-based home range si z e for e a r l y and late summer on grid H and gr i d X. The mean home range sizes l i s t e d in Table 4.1 suggest a trend in home range opposite to that predicted for a grid-trapping food addition e f f e c t , but th i s trend i s not s t a t i s t i c a l l y s i g n i f i c a n t : g r i d H paired samples t=.37, p=.72; grid X paired samples t=.41, p=.69. Table 4 .1—Telemetry-based home range estimates. GRID EARLY SUMMER LATE SUMMER MEAN(N) S.D. MEAN(N) S • D. H 2.8 ha (11) 1.9 2.7 ha (11) 1 .6 X 2.2 ha (8) 0.9 2.4 ha (8) 1 .0 There i s no detectable food addition e f f e c t due to g r i d -trapping on the amount of immigration occurring on the two gri d s . Three adult chipmunks immigrated onto each grid during e a r l y summer while I was trapping on grid H. In late summer, while I was trapping on grid X, 2 adults immigrated onto grid X and 1 adult immigrated onto g r i d H. Measurement of immigration was not 66 as r e l i a b l e f o r the non-trapping g r i d a 3 It was f o r the t r a p p i n g g r i d , s i n c e i t was not monitored s y s t e m a t i c a l l y . The number of s i g h t i n g s of unmarked a d u l t s c o r r o b o r a t e s the absence of a c a u s a l r e l a t i o n s h i p between t r a p p i n g and immigration. In e a r l y summer I recor d e d 5 s i g h t i n g s of unmarked a d u l t s on g r i d H and 3 s i g h t i n g s on g r i d X. In l a t e summer there were 2 s i g h t i n g s on each g r i d . For 9 of the 24 chipmunks equipped with r a d i o - c o l l a r s , 10% to 50% of l o c a t i o n s were o u t s i d e the g r i d s . On g r i d H, the number of o f f - g r i d l o c a t i o n s i s l e s s than the expected number i n e a r l y summer, while i n l a t e summer, o f f - g r i d l o c a t i o n s exceed the expected number (X a=7.0, d f = l , p<.01). On g r i d X, the t r e n d i s r e v e r s e d , which i s c o n s i s t e n t with a g r i d - t r a p p i n g e f f e c t s i n c e the treatment i s r e v e r s e d , but i t i s not s t a t i s t i c a l l y s i g -n i f i c a n t (X a=2.5, d f = l , p>.10). For t e l e m e t r y l o c a t i o n s i n s i d e the g r i d s I c l a s s i f i e d a l l l o c a t i o n s w i t h i n 7.5 m of a t r a p s t a t i o n as " t r a p - a s s o c i a t e d " , and a l l l o c a t i o n s g r e a t e r than 7.5 m from a t r a p s t a t i o n as "not t r a p - a s s o c i a t e d " . I chose a d i s t a n c e of 7.5 m because i t i s the s m a l l e s t d i s t a n c e I c o u l d d i s c e r n based on the g r i d system. L o c a t i o n s c l a s s i f i e d as " t r a p - a s s o c i a t e d " must be c l o s e enough to a t r a p - s t a t i o n t h a t I can assume t h a t a chipmunk i s a t l e a s t aware of the presence of the t r a p . For g r i d X, l o c a t i o n s are a s s o c i a t e d with t r a p s t a t i o n s l e s s f r e q u e n t l y than expected i n e a r l y summer and more f r e q u e n t l y than expected i n l a t e summer (X2=16.7, d f = l , p<.001). T h i s c o i n c i d e s with the t r a p p i n g regime. On g r i d H, the t r e n d Is the same, although i t i s not 67 s i g n i f i c a n t (X2=2.95, df = l , p>.10). T h i s does not c o i n c i d e with the t r a p p i n g regime, which was the r e v e r s e of t h a t on g r i d X. E f f e c t s of data source on home range For the 19 animals f o r which both t r a p p i n g and t e l e m e t r y data are a v a i l a b l e f o r the same p a r t of the summer, the r e i s no s i g n i f i c a n t d i f f e r e n c e between mean home range s i z e ( a t n=20) d e r i v e d from t r a p p i n g and t h a t d e r i v e d by t e l e m e t r y . Mean t r a p -r e v e a l e d home range i s 2 . 4 ha, mean t e l e m e t r y r e v e a l e d home range i s 3.0 ha ( p a i r e d samples t=1.63, p=.121). DISCUSSION E f f e c t s of g r i d - t r a p p i n g on home range G r i d - t r a p p i n g does not measurably change the s i z e of chipmunk home ranges. Chipmunks c o n t i n u e d t o t r a p - l i n e d u r i n g t r a p - s e s 3 i o n s as they d i d i n 1985, and cont i n u e d to empty p r e -b a i t e d t r a p s of b a i t and c o t t o n between t r a p - s e s s i o n s . G r i d -t r a p p i n g c e r t a i n l y i n c r e a s e d the a v a i l a b i l i t y of food, bedding m a t e r i a l , and cover, but not enough to a f f e c t t e lemetry-based e s t i m a t e s of home range t h a t were independent of t r a p p i n g . T h i s i n d i c a t e s t h a t f o r exp e r i m e n t a l s t u d i e s of chipmunk home range, g r i d - t r a p p i n g p r o v i d e s an adequate es t i m a t e of home range. There 68 Is no evidence t h a t g r i d - t r a p p i n g d i s t o r t s home range i n a way t h a t would i n v a l i d a t e c o n c l u s i o n s about home range response t o food and d e n s i t y m a n i p u l a t i o n s . Another t y p i c a l response to experiments which i n c r e a s e the a v a i l a b i l i t y of food i s a d e n s i t y i n c r e a s e caused by immigration onto the g r i d (Mares e t a l . , 1976; G i l b e r t and Krebs, 1981). Immigration o c c u r r e d a t ap p r o x i m a t e l y the same r a t e on both g r i d s over the season. Immigration of a d u l t s was higher i n e a r l y than In l a t e summer, and there was an i n c r e a s e i n the d e n s i t y of j u v e n i l e s on both g r i d s a t j u v e n i l e emergence In which immigra-t i o n was I n d i s t i n g u i s h a b l e from r e c r u i t m e n t . G r i d - t r a p p i n g had no e f f e c t on the amount of immigration. T e s t s f o r changes i n use d i s t r i b u t i o n as a r e s u l t of g r i d -t r a p p i n g were i n c o n c l u s i v e . I t i s p o s s i b l e t h a t chipmunks whose home ranges l i e p a r t i a l l y o u t s i d e the g r i d s change t h e i r movement p a t t e r n s so t h a t they frequent g r i d s t h a t are being trapped more than g r i d s t h a t are not being trapped. The tr e n d i s s i g n i f i c a n t on one g r i d o n l y . T h i s i n c o n s i s t e n c y suggests t h a t f a c t o r s other than the presence or absence of g r i d - t r a p p i n g , such as home range s h i f t s of females a f t e r j u v e n i l e emergence or a v a i l a b i l i t y of s e a s o n a l l y abundant patches of food, may e x p l a i n d i s t r i b u t i o n of use. For r a d i o - l o c a t i o n s i n s i d e the g r i d s , o n l y the i n h a b i t a n t s of g r i d X show a change i n use c o n c e n t r a t i o n i n response to t r a p p i n g . T h i s suggests t h a t t r a p - l i n i n g behaviour o c c u r r e d on g r i d X but not on g r i d H. Since g r i d X c o n t a i n e d a g r e a t e r 69 p r o p o r t i o n of poor h a b i t a t than g r i d H (Chapter 2 ), It i s p o s s i b l e t h a t the food provided by t r a p s on g r i d X was a more s i g n i f i c a n t r e s o u r c e than on g r i d H. The mean home range s i z e s l i s t e d l n Table 4.1 are s l i g h t l y g r e a t e r than h a l f the mean home range s i z e of 4.86 ha f o r both g r i d s over the e n t i r e season which I r e p o r t e d i n Chapter 2. T h i s d i s c r e p a n c y i s the r e s u l t of two f a c t o r s . F i r s t l y , 3 of the male chipmunks with the l a r g e s t home ranges d i e d or d i s p e r s e d b e f o r e the g r i d - t r a p p i n g treatment was switched and are t h e r e f o r e excluded from t h i s a n a l y s i s . Secondly, most l a c t a t i n g females s h i f t e d t h e i r home ranges a f t e r t h e i r young had emerged. S i n c e the data used i n chapter 2 to c a l c u l a t e mean home range f o r the e n t i r e summer Include both pre- and post-emergence p e r i o d s , they y i e l d higher e s t i m a t e s of home range than the data f o r e i t h e r p e r i o d a l o n e . E f f e c t s of data source on home range Trapping and t e l e m e t r y p r o v i d e s t a t i s t i c a l l y i n d i s t i n g u i s h -a b l e e s t i m a t e s of home range s i z e u s i n g the minimum convex polygon method of home range c a l c u l a t i o n , p r o v i d e d the sample s i z e s are e q u a l . T h i s i s c o n s i s t e n t with the f i n d i n g s of Jones and Sherman (1983) who compared e i g h t d i f f e r e n t methods of home range c a l c u l a t i o n and showed t h a t t r a p - and t e l e m e t r y - r e v e a l e d home range estimates were most comparable to one another with the minimum convex polygon method. 70 At very low sample s i z e s , trap- and telemetry-revealed home range estimates would d i f f e r , because as numerous authors have observed (Hayne, 1949; S t i c k e l , 1954; Jones and Sherman, 1983), captures often occur in a stra i g h t l i n e due to the placement of traps, y i e l d i n g MCP home range estimates of zero. Since very low sample sizes y i e l d inaccurate MCP home range estimates regardless of the data source, t h i s does not argue against the use of trapping for estimating home range. However, accumulating s u f f i c i e n t data to provide accurate home range estimates Is more rapid and less labour-intensive using telemetry than using trapping. Another d i f f i c u l t y that i s frequently encountered in g r i d -trapping studies of home range Is that grids are too small to contain the majority of home ranges of animals that inhabit them, so that home range estimation is impossible (Broome and McMahon, 1986). When these problems can be avoided, grid-trapping i s an adequate means of home range estimation i f the researcher is only interested in the size of home ranges. When other aspects of home range, such as use d i s t r i b u t i o n are of Interest, telemetry i s the superior method. 71 LITERATURE CITED A n i s k o w i t z , B.T. and J . V a i l l a n c o u r t . 1979. 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A p u l s e d -removal experiment on the v o l e M i c r o t u s townsendll. Can. J . Z o o l . 56:2253-2262. Krebs, C.J. and I. Wingate. 1976. Small mammal communities of the Kluane Region, Yukon T e r r i t o r y . Can. F i e l d Nat. 90:379-389. Krebs, C.J. and I. Wingate. 1985. P o p u l a t i o n f l u c t u a t i o n s i n the s m a l l mammals of the Kluane Region, Yukon T e r r i t o r y . Can. F i e l d Nat. 99:51-61. L a c k i , M.J., M.J. Gregory, and P.K. W i l l i a m s . 1984. S p a t i a l response of an e a s t e r n chipmunk to supplemented food. Amer. Midland Nat. 111:414-416. McNab, B.K. 1963. B i o e n e r g e t i c s and the d e t e r m i n a t i o n of home range s i z e . Amer. Nat. 97:133-141. Mace, G.M. and P.H. Harvey. 1983. E n e r g e t i c c o n s t r a i n t s on home range s i z e . Amer. Nat. 121:120-132. Mares, M.A., M.D. Watson, and T.E. Lacher J r . 1976. Home range p e r t u r b a t i o n s i n Tamias s t r i a t u s . O e c o l . 25:1-12. Mares, M.A., M.R. W i l l i g , and N.A. B i t a r . 1980. Home range s i z e i n e a s t e r n chipmunks, Tamias striatus, as a f u n c t i o n of number of ca p t u r e s , s t a t i s t i c a l b i a s e s of inadequate sampling. J . Mamm. 61:661-669. Mares, M.A., T.E. Lacher, M.R. W i l l i g , N.A. B i t a r , R. Adams, A. K l l n g e r and D. T a z l k . 1982. An experimental a n a l y s i s of s o c i a l s p a c i n g i n Tamias striatus. Ecology 63:267-273. 74 Mar t i n s e n , D.L. 1968. Temporal changes i n the home ranges of chipmunks (Eutamias). J . Mamm. 49:83-91. Me r e d i t h , D.H. 1976. H a b i t a t s e l e c t i o n by two p a r a p a t r i c s p e c i e s of chipmunks (Eutamias). Can. J . Z o o l . 54:536-543. Noble, G.K. 1939. The r o l e of dominance i n the s o c i a l l i f e of b i r d s . Auk 56:263-273. O ' F a r r e l l , T.P., R.J. Olson, R.O. G i l b e r t , and J.D. Hedlund. 1975. A p o p u l a t i o n of Great Basin pocket mice, Perognathus parvus, i n the shrub-steppe of s o u t h - c e n t r a l Washington. E c o l . Monogr. 45:1-28. Parmenter, R.R. and J.A. MacMahon. 1983. F a c t o r s d e t e r m i n i n g the abundance and d i s t r i b u t i o n of rodents i n a shrub-steppe ecosystem: the r o l e of shrubs. O e c o l o g i a 59:145-156. P e t e r s , R. 1983. The e c o l o g i c a l i m p l i c a t i o n s of body s i z e . Cambridge U n i v e r s i t y P r e s s , New York, New York, USA. P i t e l k a , F.A. 1959. Numbers, bree d i n g schedule and t e r r i t o r i a l i t y i n p e c t o r a l sand p i p e r s of nor t h e r n A l a s k a . Condor 61:233-261. R e l c h e l , J.D. 1986. H a b i t a t use by a l p i n e mammals i n the P a c i f i c Northwest, U.S.A. A r c t i c and A l p i n e Research 18:111-119. Sanderson, G.C. and B.G. Sanderson. 1964. Radio t r a c k i n g i n M a l a y a — a p r e l i m i n a r y study. J . W i l d l i f e Mgmt. 28:752-768. Seber, G.A.F. 1982. The e s t i m a t i o n of animal abundance and r e l a t e d parameters. Second e d i t i o n . C h a r l e s G r i f f i n and Company L t d . London. Sheppard, D.H. 1969. A comparison of r e p r o d u c t i o n i n two chipmunk s p e c i e s (Eutamias). Can. J . Z o o l . 47:603-608. Sheppard, D.H. 1972. Home ranges of chipmunks (Eutamias) In A l b e r t a . J . Mamm. 53:379-380. S k r y j a , D.D. 1974. Reproductive b i o l o g y of the l e a s t chipmunk (Eutamias minimus o p e r a r i u s ) i n sou t h - e a s t Wyoming. J . Mamm. 55:221-224. S t a t e s , J.B. 1976. L o c a l a d a p t a t i o n s i n chipmunks (Eutamias amoenus) p o p u l a t i o n s and e v o l u t i o n a r y p o t e n t i a l a t s p e c i e s b o r d e r s . E c o l . Monogr. 46:221-256. Southwood, T.R.E. 1966. E c o l o g i c a l methods with p a r t i c u l a r r e f e r e n c e to the study of i n s e c t p o p u l a t i o n s . Methuen & Co., L t d . London, U.K. 75 S t l c k e l , L.F. 1954. A comparison of c e r t a i n methods of measuring ranges of sm a l l mammals. J . Mamm. 35:1-15. S u l l i v a n , T.P., D.S. S u l l i v a n , and C.J. Krebs. 1983. Demographic responses of a chipmunk (Eutamias townsendii) p o p u l a t i o n with supplemental food. J . Anlm. E c o l . 52:743-755. T a i t t , M.J., J.H.W. Glpp, C.J. Krebs, and Z. D u n d j e r s k i . 1981. The e f f e c t of e x t r a food and cover on d e c l i n i n g p o p u l a t i o n s of Ml c r o t u s t o w n s e n d i i . 59:1593-1599. T a l t t , M.J. and C.J. Krebs. 1985. P o p u l a t i o n dynamics and c y c l e s . B i o l o g y of new world Mlcrotus. (R.H. Tamarln, ed.) S p e c i a l P u b l i c a t i o n of the American S o c i e t y of Mammalogists 8:567-620. Trombulak, S.C. 1985. The i n f l u e n c e of i n t e r s p e c i f i c c o m p e t i t i o n on home range s i z e i n chipmunks (Eutamias). J . Mamm. 66:329-337. Tryon, C A . and D.P. Snyder. 1973. B i o l o g y of the e a s t e r n chipmunk (Tamlas striatus): l i f e t a b l e s , age d i s t r i b u t i o n s and tre n d s i n p o p u l a t i o n numbers. J . Mamm. 54:145-168. Watson, A. and R. Moss. 1970. Dominance, s p a c i n g behaviour and ag g r e s s i o n i n r e l a t i o n to p o p u l a t i o n l i m i t a t i o n i n v e r t e b r a t e s , pp. 167-218 i n A. Watson, ed. Animal p o p u l a t i o n s i n r e l a t i o n to t h e i r food r e s o u r c e s . B l a c k w e l l S c i e n t i f i c P u b l i c a t i o n s . Oxford. Western, D. 1979. S i z e , l i f e h i s t o r y and eco l o g y i n mammals. A f r i c a n J o u r n a l of Ec o l o g y 17:185-204. Wynne-Edwards, V.C. 1962. Animal d i s p e r s i o n l n r e l a t i o n to s o c i a l b e h aviour. O l i v e r and Boyd. Edinburgh. Yahner, R.H. 1978. The ad a p t i v e nature of the s o c i a l system and behaviour i n the e a s t e r n chipmunk Tamlas s t r i a t u s . Behav. E c o l . S o c i o b i o l . 3:397-427. Yerger, R.W. 1953. Home range, t e r r i t o r y , and p o p u l a t i o n of the chipmunk i n c e n t r a l New York. J . Mamm. 34:448-458. 76 APPENDIX: SOURCE CODE LISTING (in BASIC) OF RANDOM CHIPMUNK ENCOUNTER SIMULATION MODEL T M DII IA(13,1),B0(13,4),SC|),2) FOl A»5 TO ):F0t l-i TO 2:II1D J C ( A , B ) : H X T : I I I T D H 1 10,1),10,9,20,17,0,21.5,21,),21,21,).5,20.5,20.5 FOl A * l TO 13:F0I 1>0 TO 1:IEAD I A ( A , l ) : I B I T : F O I l < l TO 4:IEA0 BO(A,l):BBXT:l T DAT! 102,1,12,44,13,33: DATA 12,1,11.5,27.5,14,21 DATA ) l , l , 3 , 3 0 . 5 , 0 , 3 0 : DATA H , l , 15.5,31.5,15,32 DATA 00,1,27,25,20,25: DATA 13,1,13,45,15,40 DATA 52,1,1,22.5,1,15: DATA 7,1,2).5,10.5,21,11 DATA (7,1,4.5,25,5,26: DATA 60,1,15.5,51.5,15,50 DATA 10,0,0,30,7,32: DATA 101,0,0,1).5,5,20 DATA 2,0,10,41,13,41 0 C U : IIPUT 'Vbick nontk? *,HO:Iir0T ' l o v B a i y c k l p n n k s ? ",IC 0 DIM t l ( I C , 4 ) , S O ( I C , l ) , I ( I C ) , T ( I C ) , T G 0 ( I C ) 0 FOl 1=1 TO I C : P i l a r i s * c h i p m k I'»STIMA);:IIP«T I I 0 FOl l«l TO 13:IF I D O I A ( B , 0 ) Till 110 0 IF IA ( I , 1 ) = 1 TIED SS(A,0)=SC{IO,0):SS(A,1)=SC(IIO,1):SI(A,0)=12 0 i r I A ( B , 1 N TIKI SS(A,0)>SC(NO,l}:SS(A,l)*SC(MO,2):SH(A rl)=( 0 FOR C=l TO 4 : S I ( l , C ) i I 0 ( l , C ) : I I I T 0 I I I T : I E I T 2 IIPUT ' O i t p t t fr«q«ency? \ n 1 IIPUT 'Output f i l e i a i e ? *,F0 4 OPEI F t FOl OUTPUT IS 11 5 BI=2:IIP0T ' E o c o i o t e r tadl«? (2 ) I ,RI:P8IIT 0 III aov l i l t l a l parameters have beet d i s t i l l e d I n t o : 0 I EM sk: 0 = u i l i a i r a d i o s , l=«est * , 2 * i e s t y,3*centre i , 4 * c e i t r e y 0 I E I s s : l = a c t l v e M a e , 1 - r e t l r e . A l l s e l e c t i o n s a c c oost f o r sex. 0 B 8 = S I ( l , l ) : P O I A=2 TO I C : I F 5S(A,1)>II TREI l l = S S ( A , l | 0 H I T 0 FOl T=SS(1,0) TO I I STEP .00 0 IF T ' S i ( l , 0 ) Till FOl 1=1 TO IC:I(A ) » 5 l(A,l|:I(A)=SI(A,2):IEIT 1 FOl CB*1 TO BC:TG$(CH)=" • 0 I EH V I I I I MTe? 5 I S ' I I D ( 1 ) : I F I5<=.25 T i l l 370 0 lS=tlD(l):DI'«.2l4«IS:TG$(Cl)>' M* 1 I I I t e s t f o r raaqe c o i s t i a l n t s 0 II=COS(DI):rt=SII|DI) 0 IF SQR(|I(CH)«I-Sl(CB ,3ir24(I(CIMTI-SI(CI,4|)"2)>Sa(CI,0) Till PL=FUl:GO 310 0 I ( C H ) = I | C I ) U I : I ( C i ) = T ( C I | t I I 0 I8IT 5 I C M T - S I ( 1 , 0 ) ) / F I 0 IF AK(HC-IIT(1IC))».000001E-02 TBEI 500 0 E h O i P B I I T ' T l M i s " ; : P I I I T T:F0I CH=1 TO IC 0 P I I I T 1|CH),T|CI); ISO p im ' s i coonn 1 ; U l KIT'.PtllT ?C$(CH):IHT:gl*H/2:TE*TMI 4(0 PllIT ll,BI:PRIIT 500 KIT 595 PHI? 'Total eicoiBteis= * ; : P R I I T TE $10 ClOSI 

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