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UBC Theses and Dissertations

Behavioral responses of lynx to declining snowshoe hare abundance Ward, Richard Miles Peary 1985

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BEHAVIORAL RESPONSES OF LYNX TO DECLINING SNOWSHOE HARE ABUNDANCE by RICHARD M.P.WARD B.Sc. A c a d i a U n i v . Nova S c o t i a 1978 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 ac c e p t t h i s t h e s i s as co n f o r m i n g t o the r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA January 1985 (?) R i c h a r d M.P.Ward, 1985 I n p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an advanced degree a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I agree t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by t h e head o f my department o r by h i s o r her r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 DE-6 (3/81) i i ABSTRACT The b e h a v i o r a l responses of l y n x (Lynx c a n a d e n s i s ) t o d e c l i n e s i n snowshoe hare (Lepus americanus) abundance were examined i n the southwestern Yukon. Between A p r i l 1982 and June 1984 11 l y n x were r a d i o - t a g g e d and m o n i t o r e d w i t h i n and near the Kluane Game S a n c t u a r y . Lynx mean home range s i z e i n c r e a s e d from 13.2 t o 39.2 km 2 c o n c u r r e n t w i t h a d e c l i n e i n snowshoe hare abundance from 14.7 t o 0.2 h a r e s / h a . Below about 0.5 ha r e s / h a s e v e r a l l y n x abandoned t h e i r home ranges and became nomadic, a l t h o u g h they remained w i t h i n the g e n e r a l study a r e a . Track t r a n s e c t s through a r e a s known t o have d i f f e r e n t snowshoe hare d e n s i t i e s i n d i c a t e d t h a t , l y n x c o n c e n t r a t e d t h e i r f o r a g i n g e f f o r t s i n a r e a s of r e l a t i v e l y h i g h snowshoe hare abundance. Lynx abandoned the s e a r e a s a f t e r hare abundance d e c l i n e d . Lynx f o r a g i n g e f f o r t i n terms of d i s t a n c e t r a v e l l e d per day showed a c u r v i l i n e a r r e l a t i o n s h i p t o snowhoe hare abundance. S t r a i g h t -l i n e d a i l y t r a v e l d i s t a n c e remained c o n s t a n t a t 2.2 t o 2.7' km/day above 1.0 hare/ha. Below 1.0 h a r e s / h a , s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e s i n c r e a s e d r a p i d l y , r e a c h i n g 5.5 km/day a t 0.2 h a r e s / h a . Three of 7 r a d i o - t a g g e d l y n x d i s p e r s e d 250 km or more from the study area d u r i n g the p e r i o d of r a p i d d e c l i n e i n hare abundance i n 1982. No s i m i l a r l o n g d i s t a n c e d i s p e r s a l was r e c o r d e d a f t e r hare d e n s i t i e s s t a b l i z e d a t l e s s than 1.0 ha r e s / h a . T r a p p i n g m o r t a l i t y was r e s p o n s i b l e f o r the l o s s of 7 of 9 r a d i o - t a g g e d l y n x t h a t t r a v e l l e d o u t s i d e the game s a n c t u a r y . One l y n x d i e d , and i s b e l i e v e d t o have s t a r v e d , d u r i n g the w i n t e r or s p r i n g of 1984. The h i g h r a t e of t r a p p i n g m o r t a l i t y o u t s i d e the game s a n c t u a r y s u g gests t h a t r e f u g i a i n w i l d e r n e s s a r e a s are im p o r t a n t i n m a i n t a i n i n g l y n x p o p u l a t i o n s d u r i n g p e r i o d s of low r e c r u i t m e n t . TABLE OF CONTENTS ABSTRACT i i LIST OF TABLES i v LIST OF FIGURES v ACKNOWLEDGEMENTS . . v i INTRODUCTION 1 METHODS and STUDY AREA 5 Study Area 5 Tim i n g and Emphasis of Study 5 E s t i m a t i o n of Snowshoe Hare Abundance 8 Lynx T r a p p i n g and Radio Tagging 9 Radio T e l e m e t r y and Home Range D e t e r m i n a t i o n 9 Track T r a n s e c t s 11 RESULTS 12 Snowshoe Hare Abundance 12 Lynx T r a p p i n g Success 15 E f f e c t of Snowshoe Hare Abundance on Lynx Home Range S i z e 21 E f f e c t of Snowshoe Hare Abundance on Lynx F o r a g i n g E f f o r t 35 E f f e c t of Snowshoe Hare D i s t r i b u t i o n on Lynx F o r a g i n g P a t t e r n s . 38 Lynx D i s p e r s a l and M o r t a l i t y d u r i n g a D e c l i n e i n Snowshoe Hare Abundance 44 DISCUSSION 49 Lynx Home Range S i z e 49 E f f e c t of Snowshoe Hare Abundance on Lynx F o r a g i n g E f f o r t 56 E f f e c t of Snowshoe Hare D i s t r i b u t i o n on Lynx F o r a g i n g P a t t e r n s 66 Lynx D i s p e r s a l and M o r t a l i t y 68 Lynx S o c i a l S t r u c t u r e 72 Management I m p l i c a t i o n s 76 I n t r o d u c t i o n 76 The Models 77 R e s u l t s and D i s c u s s i o n 82 REFERENCES CITED 95 APPENDIX 102 LIST OF TABLES T a b l e 1. Summary of the importance of snowshoe hare s i n the d i e t of l y n x 3 T a b l e 2. Summary of l y n x t r a p p i n g s u c c e s s 16 T a b l e 3. Lynx body w e i g h t s 18 T a b l e 4. Comparison of 100% and 90% home range a r e a s of l y n x 24 T a b l e 5. E f f e c t of r e l a t i v e snowshoe hare abundance on l y n x f o r a g i n g p a t t e r n s 42 T a b l e 6. Parameter e s t i m a t e s used i n l y n x p o p u l a t i o n s i m u l a t i o n models 78 V LIST OF FIGURES F i g u r e 1. Map of study a r e a 6 F i g u r e 2. Snowshoe hare abundance 13 F i g u r e 3. Examples of 100% and 90% l y n x home range s i z e e s t i m a t e s 22 F i g u r e 4. Mean home range s i z e f o r l y n x v e r s u s snowshoe hare abundance 26 F i g u r e 5. I n d i v i d u a l l y n x home range s i z e s v e r s u s snowshoe hare abundance 29 F i g u r e 6. Map of a r e a s d e l i n e a t e d by j o i n i n g outermost observed l o c a t i o n s of "nomadic" i n d i v i d u a l s 32 F i g u r e 7. Mean s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e s of l y n x v e r s u s snowshoe hare abundance 36 F i g u r e 8. Maximum ob s e r v e d s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e s of l y n x v e r s u s snowshoe hare abundance 39 F i g u r e 9. Map of l o n g d i s t a n c e d i s p e r s a l movements undertaken by l y n x 46 F i g u r e 10. Observed and ex p e c t e d t o t a l d a i l y t r a v e l d i s t a n c e s f o r l y n x v e r s u s snowshoe hare abundance 59 F i g u r e 11. R e p r o d u c t i o n of F i g u r e 2, Brand and K e i t h (1979) w i t h 2 a d d i t i o n a l r e g r e s s i o n l i n e s added 62 F i g u r e 12. Dynamics of s i m u l a t e d l y n x p o p u l a t i o n u s i n g model A w i t h o b s e r v e d m o r t a l i t y r a t e s 83 F i g u r e 13. Dynamics of s i m u l a t e d l y n x p o p u l a t i o n u s i n g model A w i t h t o t a l a n n u a l m o r t a l i t y r a t e s e t a t 0.30. .. 85 F i g u r e 14. Dynamics of s i m u l a t e d l y n x p o p u l a t i o n u s i n g model A and m o r t a l i t y r a t e e s t i m a t e s from Brand and K e i t h 1979 87 v i ACKNOWLEDGEMENTS Many i n d i v i d u a l s made v a l u a b l e c o n t r i b u t i o n s t o my p r o g r e s s i n t h i s s t u d y . Foremost, I w i s h t o d e d i c a t e t h i s t h e s i s t o the 11 i n d i v i d u a l s w i t h o u t whose invol v e m e n t t h i s r e s e a r c h would not have been p o s s i b l e : To J o y , S c r u f f , S i d , C h a r l e y , C a r l o s , J e a n , S c o t t i e , Rene, J e n n i f e r , E n r i q u e and P a u l . Dr. C.J. Krebs was the p r i n c i p l e academic s u p e r v i s o r f o r t h i s s t u d y . Throughout the s t u d y , he p r o v i d e d support and encouragement i n v a r i o u s forms. He a l s o s e t an i n s p i r i n g , i f e x h a u s t i n g , example w i t h the amount of energy he devoted t o f i e l d r e s e a r c h and e c o l o g y i n g e n e r a l . Thanks a g a i n C h a r l e y . Dr. A.R.E. S i n c l a i r a l s o a c t e d as academic s u p e r v i s o r d u r i n g a p o r t i o n of t h i s s t u d y . He a l s o p r o v i d e d o f f i c e s u p p l i e s d u r i n g the w r i t e - u p phase of the s t u d y . Thanks Tony. I g r a t e f u l l y acknowledge the support and i n p u t of my r e s e a r c h committee. D r s . C.J. K r e b s , J.N.M. Smith and D.M. S h a c k l e t o n a l l made v a l u a b l e comments and u s e f u l s u g g e s t i o n s . I w i s h t o e x p r e s s my a p p r e c i a t i o n t o the s t a f f and o t h e r r e s e a r c h e r s a t the Kluane Lake Research S t a t i o n who made my s t a y t h e r e an e x t r e m e l y p l e a s a n t and r e w a r d i n g t i m e . I e s p e c i a l l y w i s h t o thank the 2 W i l l i a m s f a m i l i e s , S c o t t , J e a n , C a r l o s , J e n n i f e r , Joy and John. I t wouldn't have been the same w i t h o u t you. When not p l a y i n g w i t h g r i z z l y b ears d u r i n g the summer of 1983, H e n r i k A s f e l t a s s i s t e d i n d a t a c o l l e c t i o n . A l i s t a i r B l a c h f o r d and Tom Hurd a s s i s t e d w i t h the computer programming n e c e s s a r y f o r d a t a a n a l y s i s . Tom Hurd a l s o made v a l u a b l e comments on an i n i t i a l d r a f t . Marc L a b e l l e o f f e r e d a d v i c e on s t a t i s t i c a l a n a l y s i s . O t h e r s , t o o numerous t o name, a s s i s t e d i n v a r i o u s a s p e c t s of t h i s r e s e a r c h . To them I o f f e r my s i l e n t g r a t i t u d e . T h i s r e s e a r c h was funded by g r a n t s from B r i t i s h Columbia S c i e n c e C o u n c i l , N o r t h e r n S c i e n t i f i c T r a i n i n g Program, and g r a n t s t o Dr. C h a r l e s Krebs from the N a t u r a l S c i e n c e s and E n g i n e e r i n g Research C o u n c i l . 1 INTRODUCTION The c l o s e r e l a t i o n s h i p between the t e n year c y c l e s of l y n x (Lynx c a n a d e n s i s ) and the snowshoe hare (Lepus americanus) was f i r s t n oted i n the e c o l o g i c a l l i t e r a t u r e by E l t o n and N i c h o l s o n (1942). S i n c e then many a s p e c t s of l y n x n a t u r a l h i s t o r y and e c o l o g y have been s t u d i e d (see P a r k e r e t a l . 1983 f o r a r e v i e w ) . In view of the c l o s e r e l a t i o n s h i p between l y n x and snowshoe hare numbers, s u r p r i s i n g l y l i t t l e of the p r e v i o u s work has r e l a t e d l y n x e c o l o g y t o snowshoe hare abundance. S e v e r a l s t u d i e s , however, have r e l a t e d hare abundance t o l y n x r e p r o d u c t i o n and m o r t a l i t y (van Z y l l de Jong 1963, Stewart 1973, Nava 1970, N e l l i s e t a l . 1972, Brand e t a l . 1976, Brand and K e i t h 1979, P a r k e r e t a l . 1983). These s t u d i e s have shown an i n c r e a s e i n m o r t a l i t y and a d e c l i n e i n r e c r u i t m e n t of l y n x w i t h d e c l i n i n g snowshoe hare abundance. G e n e r a l body c o n d i t i o n of l y n x has a l s o been shown t o be p o s i t i v e l y c o r r e l a t e d w i t h hare abundance. S t u d i e s of the e f f e c t s of hare abundance on o t h e r a s p e c t s of l y n x e c o l o g y have been r e p o r t e d by N e l l i s and K e i t h 1968, N e l l i s e t a l . 1972, N e l l i s 1975, and Brand e t a l . 1976. These s t u d i e s were p a r t of a l o n g term s t u d y of snowshoe hare p o p u l a t i o n dynamics i n A l b e r t a ( K e i t h and Windberg 1978). P a r k e r e t a l . (1983) a l s o r e p o r t on a stu d y of prey abundance and l y n x e c o l o g y i n Nova S c o t i a . These s t u d i e s and o t h e r s have been unanimous i n f i n d i n g t h a t snowshoe hares a r e the s i n g l e most i m p o r t a n t food item i n the d i e t of the l y n x d u r i n g a l l phases of the 10 year c y c l e 2 (Table 1 ) . The f a c t t h a t l y n x r e c r u i t m e n t d e c l i n e s and m o r t a l i t y r a t e s i n c r e a s e w i t h d e c l i n i n g hare abundance c l e a r l y i n d i c a t e s t h a t l y n x a r e s e v e r e l y energy s t r e s s e d d u r i n g the d e c l i n e and low phases of the hare c y c l e . One would t h e r e f o r e expect t h a t l y n x would e x h i b i t major b e h a v i o r a l changes i n an e f f o r t t o c o n t i n u e t o f u l f i l l t h e i r e n e r g e t i c r e q u i r e m e n t s as hare abundance d e c l i n e s . The most o b v i o u s mechanisms l y n x might use a r e : 1) i n c r e a s e t h e i r home range s i z e ; 2) i n c r e a s e t h e i r f o r a g i n g e f f o r t and 3) seek out and c o n c e n t r a t e t h e i r f o r a g i n g e f f o r t i n p a t c h e s of r e l a t i v e l y h i g h prey abundance. In t h i s s t u d y I i n v e s t i g a t e d the degree t o which l y n x u t i l i z e each of t h e s e p o s s i b l e mechanisms t o maximize t h e i r energy i n t a k e . I p r e s e n t data on l y n x d i s p e r s a l and m o r t a l i t y d u r i n g a snowshoe hare d e c l i n e . F i n a l l y , the f a c t o r s s t r u c t u r i n g the l y n x s o c i a l system and the management i m p l i c a t i o n s of my f i n d i n g s are d i s c u s s e d . 3 T a b l e 1. A summary from p a s t s t u d i e s of the importance of snowshoe h a r e s i n the d i e t of l y n x . Study Hare c y c l e phase Season Most i m p o r t a n t i t e m i n l y n x d i e t Next most im p o r t a n t item i n l y n x d i e t N e l l i s et a l . 1 972 A l b e r t a d e c l i n e w i n t e r s 1964-67 h a r e s 7 6% of biomass 9.8% c a r r i o n low w i n t e r c a r r i o n 52% of biomass hares 43% of biomass Brand et a l . 1976 A l b e r t a h i g h h i g h w i n t e r summer hares 100% of biomass hares 91% of biomass 2% mice and v o l e s More 1 976 s o u t h -western N.W.T. low w i n t e r hares 79-100% f r e q . of occurance i n s c a t s 25-64% r e d s q u i r r e l van Z y l l De Jong 1 963 A l b e r t a s t a r t of d e c l i n e w i n t e r h a r e s 79% f r e q . of o c c u r , i n gut c o n t e n t s 10% m i c r o t i n e summer hares 52% f r e q . of o c c u r , i n gut c o n t e n t s 31% m i c r o t i n e Saunders 1 963 N f l d . w i n t e r h a r e s 85% of b i oma s s 1 3% moose summer hares 60% of biomass 30% m i c r o t i n e 5 METHODS AND STUDY AREA Study Area The study was c e n t e r e d i n the southwestern Yukon, n o r t h of Kluane N a t i o n a l Park w i t h i n and a d j a c e n t t o Yukon Game Management Zone 6-10 ( F i g u r e 1 ) . T h i s i s c l a s s i f i e d as a game s a n c t u a r y w i t h no h u n t i n g or t r a p p i n g p e r m i t t e d . The a r e a i s p a r t of the n o r t h e r n b o r e a l f o r e s t zone as d e s c r i b e d by Douglas (1974). White spruce ( P i c e a g l a u c a ) i s the dominant t r e e s p e c i e s , w i t h a v a r i e t y of w i l l o w s ( S a l i x spp. ) and o t h e r l e s s abundant shrubs s p e c i e s making up the u n d e r s t o r y . The study a r e a i s d i s s e c t e d by a number of o l d m i n i n g and e x p l o r a t i o n roads which f a c i l i t a t e d t r a v e l . W i n t e r t r a v e l was ac c o m p l i s h e d by snowmobile, snowshoeing and s k i i n g . Summer t r a v e l was by f o u r wheel d r i v e t r u c k , t r a i l b i k e and w a l k i n g . Timing and Emphasis of Study I conducted the study between F e b r u a r y 1982 and June 1984. Between F e b r u a r y and May 1982 I foc u s e d my e f f o r t s around g r i d s A (Microwave) and B (Beaver Pond) ( F i g u r e 1 ) . I expended e q u a l t r a p p i n g e f f o r t f o r bo t h l y n x and snowshoe hares on each g r i d d u r i n g t h i s p e r i o d . W i n t e r s n o w - t r a c k i n g e f f o r t was a l s o equal on each g r i d . A f t e r May 1982, g r i d B was abandoned f o r l y n x t r a p p i n g and s n o w - t r a c k i n g due t o i t s r e l a t i v e i n a c c e s s i b i l i t y 6 F i g u r e 1. Map of s t u d y a r e a i n southwestern Yukon. A, B, C and D i n d i c a t e l o c a t i o n s of snowshoe hare l i v e - t r a p p i n g g r i d s . See t e x t f o r a d e s c r i p t i o n of the g r i d s . 8 a l t h o u g h I c o n t i n u e d t o m o n i t o r hare abundance on the g r i d . Lynx and snowshoe hare m o n i t o r i n g c o n t i n u e d t o be most i n t e n s i v e w i t h i n the Kluane Game S a n c t u a r y t o take advantage of the road system i n t h i s a r e a . C a r e f u l r e c o r d s of the number and d i s t r i b u t i o n of l y n x t r a c k s i n the s a n c t u a r y were kept so t h a t an e s t i m a t e c o u l d be made of the p r o p o r t i o n of l y n x i n the area t h a t were r a d i o - t a g g e d . The t o t a l s tudy a r e a was expanded as n e c e s s a r y to m a i n t a i n c o n t a c t w i t h the r a d i o - t a g g e d l y n x ( F i g u r e 1 ) . E s t i m a t i o n of Snowshoe Hare Abundance Snowshoe hare abundance was m o n i t o r e d on f o u r l i v e - t r a p p i n g g r i d s i n the study a r e a as p a r t of a c o n c u r r e n t study of t h e i r t e n y e a r c y c l e . G r i d A (Microwave) was a food a d d i t i o n g r i d t o d e t e r m i n e the e f f e c t of s u p p l e m e n t a l food on hare abundance. G r i d s B (Beaver Pond), C ( G r i z z l y ) and D (1050) were c o n t r o l s f o r A ( F i g u r e 1). L i v e - t r a p p i n g t e c h n i q u e s on these g r i d s are d e s c r i b e d by B o u t i n (1980). Hare abundance was d e t e r m i n e d u s i n g the minimum number a l i v e (MNA) method (Krebs 1966). Hare d e n s i t i e s on the g r i d s were c a l c u l a t e d w i t h o u t the a d d i t i o n of a boundry s t r i p (MNA/area of g r i d ) . B o n d r u p - N i e l s e n (1983) d i s c u s s e d the b i a s i n t r o d u c e d i n t o d e n s i t y e s t i m a t e s r e s u l t i n g from the use of r e l a t i v e l y s m a l l g r i d s i z e i n l i v e - t r a p p i n g programs. H i s model s u g g e s t s t h a t my d e n s i t y e s t i m a t e s may be 2 t o 3 t i m e s too h i g h . 9 Lynx T r a p p i n g and R a d i o Tagging T r a p p i n g e f f o r t s t o c a p t u r e and r a d i o - t a g l y n x c o n t i n u e d from F e b r u a r y through December 1982 and from A p r i l t o September 1983. I n i t i a l l y , an attempt was made t o c a p t u r e l y n x u s i n g box t r a p s but t h i s proved i n e f f e c t i v e . L a t e r t r a p p i n g e f f o r t s were s i m i l a r t o those employed by p r o f e s s i o n a l t r a p p e r s . S t e e l l e g -h o l d t r a p s , r a n g i n g i n s i z e from #2 t o #4, w i t h the jaws padded w i t h e i t h e r c l o t h tape or rubber were used i n "cubby" type s e t s (see Anonymous,1982). S e t s were p l a c e d a l o n g t r a i l s and roads w i t h i n the study a r e a and checked a t l e a s t once every 24 h o u r s . A v a r i e t y of b a i t s r a n g i n g from commercial l u r e s t o perfume and s i l v e r r i b b o n s were used. Once a l y n x was t r a p p e d , i t was immoblized w i t h k e t a s e t ( c o n c e n t r a t i o n I00mg/ml: rogar/STB, d i v i s i o n of BTI P r o d u c t s I n c . , London, O n t a r i o ) a t a dosage of a p p r o x i m a t e l y 0.2 ml p e r kg of body w e i g h t . The l y n x was then weighed, sexed, e a r - t a g g e d and f i t t e d w i t h a r a d i o t r a n s m i t t e r p r i o r t o r e l e a s e . R a d i o T e l e m e t r y and Home Range D e t e r m i n a t i o n R a d i o t e l e m e t r y equipment was produced by W i l d l i f e M a t e r i a l s I n c . , C a r b o n d a l e , I l l i n o i s . Lynx were l o c a t e d u s i n g s t a n d a r d r a d i o - t e l e m e t r y t e c h n i q u e s (Cochran 1980) w i t h a c o m b i n a t i o n of handheld and f i x e d tower antennas. Accuracy checks on t r a n s m i t t e r s i n known l o c a t i o n s i n d i c a t e d t h a t compass b e a r i n g s u s i n g t h i s system were a c c u r a t e t o + 5 degrees 95% of 10 the t i m e . Compass b e a r i n g s were l e s s a c c u r a t e i f the r a d i o -tagged a n i m a l was a c t i v e when the b e a r i n g was b e i n g t a k e n . I f i t was f e l t t h a t the e r r o r i n t r o d u c e d by a c t i v i t y was e x c e s s i v e , no compass b e a r i n g s was r e c o r d e d . A minimum of 2 compass b e a r i n g s were r e q u i r e d t o produce each l o c a t i o n . I f a l y n x d i s a p p e a r e d from the study a r e a , an e f f o r t was made t o l o c a t e i t u s i n g r a d i o - t e l e m e t r y from an a i r c r a f t . The l y n x were l o c a t e d a t v a r i o u s times throughout the day and n i g h t from A p r i l and December, 1982 and between May and Oc t o b e r , 1983 and d u r i n g May and June 1984. Once f i t t e d w i t h a r a d i o t r a n s m i t t e r , each l y n x was f o l l o w e d u n t i l i t d i s p e r s e d from the a r e a , i t was t r a p p e d by p r o f e s s i o n a l t r a p p e r s , or the t r a n s m i t t e r stopped w o r k i n g . I d e f i n e d home range as the c o n s i s t e n t use of an ar e a over a 3 month p e r i o d . I t h e r e f o r e s u b d i v i d e d the study i n t o the f o l l o w i n g 3 month p e r i o d s f o r subsequent a n a l y s i s : PERIOD MONTHS A p r i l - J u n e 1982 2 July-September 1982 3 October-December 1982 4 A p r i l - J u n e 1983 5 July-September 1983 6 A p r i l - J u n e 1984 I used a minimum of 30 p o i n t l o c a t i o n s w i t h i n . each p e r i o d t o d e t e r m i n e home range. Home range s i z e was e s t i m a t e d by the 11 convex polygon method (Mohr 1947) w i t h the f o l l o w i n g m o d i f i c a t i o n . I e l i m i n a t e d the outermost 10% of l o c a t i o n s i n c a l c u l a t i n g home range s i z e a f t e r the method of B o u t i n (1980). T h i s reduced the i n c l u s i o n of o c c a s i o n a l wanderings by l y n x i n the assessment of i t s home range. Track T r a n s e c t s To determine the e f f e c t s of r e l a t i v e snowshoe hare abundance on p a t t e r n s of h a b i t a t use by l y n x , w i n t e r snow t r a c k t r a n s e c t s were run through a r e a s known t o have d i f f e r e n t hare abundances. The number of s e t s of f r e s h l y n x t r a c k s c r o s s i n g e v e r y 600 meters of t r a n s e c t was r e c o r d e d . T r a n s e c t s were conducted each morning when weather and snow c o n d i t i o n s p e r m i t t e d throughout A p r i l and from l a t e October t o e a r l y December 1982. 12 RESULTS Snowshoe Hare Abundance Hare abundance on g r i d s A ( s u p p l e m e n t a l f o o d g r i d ) , C and D peaked i n the f a l l of 1980. G r i d B reached i t s maximum d e n s i t y i n the f a l l of 1981. Maximum f a l l snowshoe hare d e n s i t i e s i n 1981 on g r i d A were 22.6 h a r e s / h a , w h i l e on g r i d s B, C and D they were r e s p e c t i v e l y 10.3, 8.0 and 10.7 (mean 9.7 ±1.2) hares/ha ( F i g u r e 2 ) . D e n s i t i e s began t o d e c l i n e r a p i d l y on g r i d s B, C and D i n January 1982 w h i l e r e m a i n i n g r e l a t i v e l y h i g h on g r i d A throughout the s p r i n g of 1982. In A p r i l 1982 when I began m o n i t o r i n g l y n x a c t i v i t i e s , hare abundance on g r i d s B, C, and D r e s p e c t i v e l y was 2.6, 2.4 and 1.4 (mean 2.1 ±0.5) hares/ha w h i l e on g r i d A hare d e n s i t y was 14.7 h a r e s / h a . By J u l y hare d e n s i t y had dropped t o a p p r o x i m a t e l y 1.0 ±0.4 hares/ h a on the c o n t r o l g r i d s and t o 3.3 on the s u p p l e m e n t a l food g r i d . P o p u l a t i o n d e n s i t e s l e v e l l e d o f f or i n c r e a s e d s l i g h t l y on a l l g r i d s d u r i n g the summer months as young of the year were born. D u r i n g O c t o b e r , however, d e n s i t i e s began t o d e c l i n e a g a i n on a l l g r i d s . S p r i n g d e n s i t i e s i n 1983 were e q u i v a l e n t on a l l g r i d s a t 0.2 ±0.1 h a r e s / h a . By J u l y d e n s i t i e s on a l l g r i d s had i n c r e a s e d s l i g h t l y , a v e r a g i n g 0.5 ±0.2 h a r e s / h a . Snowshoe hare d e n s i t i e s remained r e l a t i v e l y c o n s t a n t a t between 0.2 and 0.5 hares/ha on a l l g r i d s t h r o u g h June 1984. 13 F i g u r e 2. Snowshoe hare d e n s i t y on s u p p l e m e n t a l food g r i d A ( s o l i d l i n e ) and c o n t r o l g r i d s B, C and D (dashed l i n e ) . D e n s i t i e s a r e based on t o t a l enumeration t e c h n i q u e s (Krebs 1966).. V e r t i c a l b a r s on dashed l i n e i n d i c a t e ±1 s t a n d a r d d e v i a t i o n . 3 0 i January 1981 January 1982 January 1983 January 1984 DATE 15 Lynx T r a p p i n g Success E l e v e n l y n x (5 females and 6 males) were t r a p p e d and r a d i o -tagged i n a p p r o x i m a t e l y 4700 t r a p - n i g h t s between A p r i l 1982 and September 1983 (Table 2 ) . In a d d i t i o n , one female (Jean) was r e c a p t u r e d and r e l e a s e d a p p r o x i m a t e l y 9 months a f t e r her i n i t i a l c a p t u r e . I t was not p o s s i b l e t o determine the p r e c i s e age of the i n d i v i d u a l s but from the c o n d i t i o n of the n i p p l e s and g e n i t a l i a i t was e v i d e n t t h a t two of the females (Joy and J e n n i f e r ) had bred p r e v i o u s l y and were t h e r e f o r e a t l e a s t 2 y e a r s o l d . Jea n , showed no s i g n s of p r e v i o u s b r e e d i n g but her weight (10.7 kg) and the f a c t t h a t she was t r a v e l l i n g a l o n e , s u g g e s t s t h a t she was a l s o a t l e a s t one and a h a l f y e a r s o l d a t the time of her i n i t i a l c a p t u r e . S c r u f f and Rene showed no s i g n s of p r e v i o u s b r e e d i n g and may have been y e a r l i n g s when I r a d i o - t a g g e d them. Wi t h the e x c e p t i o n of S c o t t i e , a l l males had a d u l t body w e i g h t s , f u l l y d e v e l o p e d p e n i s e s , s c r o t a l t e s t e s and were t r a v e l l i n g a l o n e , i n d i c a t i n g t h a t they were a t l e a s t 1 year o l d . S c o t t i e had a d u l t body w e i g h t , but an i n c o m p l e t e l y d e v e l o p e d p e n i s , non-s c r o t a l t e s t e s and was t r a v e l l i n g w i t h a n o t h e r l y n x , presumably h i s mother, s u g g e s t i n g t h a t he was a young of the year 1982. From the l i m i t e d d a t a o b t a i n e d , females would seem t o l o s e body c o n d i t o n more r a p i d l y than males as hare abundance d e c l i n e s (Table 3 ) . A l l males c a p t u r e d and r a d i o - t a g g e d i n t h i s study appeared t o be e x c e l l e n t body c o n d i t i o n . In f a c t body w e i g h t s of 2 males c a p t u r e d l a t e i n the study were e q u i v a l e n t t o or h i g h e r than those c a p t u r e d e a r l y i n the s t u d y . Females c a p t u r e d 16 T a b l e 2. Summary of l y n x t r a p p i n g s u c c e s s , minimum r e s i d e n c y time on study a r e a and f a t e of r a d i o - t a g g e d l y n x . 17 Lynx Capture d a t e (D/M/YR) Age Sex Minimum r e s i d e n c y on study a r e a F a t e Joy 4/4/82 a d u l t =>2 y r s . F 35 Days d i s p e r s e d 8/5/82. k i l l e d 700 km N of t a g g i n g s i t e , December 1982. S i d 17/4/82 a d u l t =>1 y r . M 9 Months k i l l e d w i t h i n 10 km of t a g g i n g s i t e , J a n u a r y 1983. S c r u f f 21/4/82 a d u l t =>1 y r . F 7 Months d i s p e r s e d 16/10/82. k i l l e d 250 km N of t a g g i n g s i t e , Nov. 1982. C h a r l i e 25/5/82 a d u l t =>1 y r . M 40 Days d i s p e r s e d 5/7/82. k i l l e d 250 km N of t a g g i n g s i t e , Dec. 1982. C a r l o s 1/8/82 a d u l t =>1 y r . M 13 Months r e s i d i n g i n study a r e a September 1 983. S c o t t i e 20/10/82 k i t t e n < 1 y r . M 2 Months k i l l e d w i t h i n 10 km of t a g g i n g s i t e , December 1982. Jean 25/10/82 a d u l t =>1 y r . F 10 Months k i l l e d w i t h i n 10 km of t a g g i n g s i t e , w i n t e r 1983-84. Rene 15/7/83 a d u l t =>1 y r . F 6 Months found dead 35 km e a s t of t a g g i n g s i t e , June 1984. J e n n i f e r 19/7/83 a d u l t =>2 y r s . F 11 Months r e s i d i n g i n study a r e a , June 1984. E n r i q u e 29/7/83 a d u l t =>1 y r . M 11 Months r e s i d i n g i n study a r e a , June 1984: P a u l 1/8/83 a d u l t =>1 y r . M 4 Months k i l l e d w i t h i n 10 km of t a g g i n g s i t e , J a n u a r y 1984. 18 T a b l e 3. Body w e i g h t s f o r i n d i v i d u a l l y n x a t time of c a p t u r e . Means a r e not s i g n i f i c a n t l y d i f f e r e n t ( T - t e s t P> 0.05). * i n d i c a t e s r e c a p t u r e . Date Male c a p t u r e w e i g h t s (Kg) Female c a p t u r e w e i g h t s (Kg) A p r i l t o December 1 982 S i d 8.8 C h a r l i e 8.6 C a r l o s 8.3 S c o t t i e 9.7 mean = 8.9 95% c . i . = 8.0-9.7 Joy 9.5 S c r u f f 8.3 Jean l b . 6 mean = 9.5 95% c . i . = 7.3-11.6 A p r i l t o September 1 983 E n r i q u e 10.4 P a u l 9.5 mean =10.0 95% c . i . = 8.0-11 .9 Jean * 9.9 Rene 7.7 J e n n i f e r 7.5 mean = 8.4 95% c . i . = 5.9-10.8 20 e a r l y i n the study had body w e i g h t s s i m i l a r t o those of males and appeared t o be i n good c o n d i t i o n . Those c a p t u r e d l a t e r i n the s t u d y (Rene and J e n n i f e r ) however, were emaciated and had lower body w e i g h t s . Jean a l s o l o s t 0.8 kg (7.5% of her i n i t i a l body w e i g h t ) between her i n i t i a l c a p t u r e i n October 1982 and her r e c a p t u r e i n J u l y 1983. A l t h o u g h i t i s d i f f i c u l t t o a s s e s s a c c u r a t e l y what p r o p o r t i o n of the p o p u l a t i o n I had r a d i o - t a g g e d , an e s t i m a t e can be o b t a i n e d , f o r the w i n t e r s a t l e a s t , from r e p e a t e d t r a c k t r a n s e c t s t h r o u g h the a r e a . I b e l i e v e t h a t I had r a d i o - t a g g e d 4 of 5 l y n x u s i n g g r i d A i n A p r i l and May 1982. As p r e v i o u s l y mentioned, I expanded t o study a r e a d u r i n g the summer of 1982 ( F i g u r e 1 ) . By November I was m o n i t o r i n g 5 l y n x and I susp e c t t h a t 5 more l y n x were r e s i d i n g i n . the a r e a . F u r t h e r e v i d e n c e t h a t a l a r g e p r o p o r t i o n of the l y n x p o p u l a t i o n was r a d i o - t a g g e d i s t h a t o n l y 1 of 10 l y n x s i g h t e d d u r i n g the study was untagged. D u r i n g the 26 months of the s t u d y , over 1300 t e l e m e t r y l o c a t i o n s and v i s u a l s i g h t i n g s were made on the 11 l y n x . Minimum r e s i d e n c y t i m e s f o r these l y n x ranged from 35 days t o 13 months. 21 E f f e c t of Snowshoe Hare Abundance on Lynx Home Range S i z e As d e s c r i b e d i n the methods, I e l i m i n a t e d the outermost 10% of l o c a t i o n s when c a l c u l a t i n g l y n x home range s i z e . The l o s s of thes e outermost p o i n t s r e s u l t s i n a r e d u c t i o n of home range s i z e of from 3 t o 70 p e r c e n t ( F i g u r e 3a, b, c and d ) . For comparison w i t h o t h e r s t u d i e s I p r e s e n t my r e s u l t s as both 100% and 90% home ranges (Table 4) and I use 90% range i n my a n a l y s i s and d i s c u s s i o n . A l t h o u g h t h e r e was a s l i g h t t r e n d f o r females t o have s m a l l e r home ranges than males w i t h i n a g i v e n range of snowshoe hare d e n s i t i e s , i t was not c o n s i s t e n t or s t a t i s t i c a l l y s i g n i f i c a n t ( t - t e s t , P>0.05). The data a re t h e r e f o r e combined f o r the a n a l y s i s of the e f f e c t of snowshoe hare abundance on l y n x home range s i z e . D u r i n g the summer of 1983 Rene d i d not use any ar e a c o n s i s t e n t l y . J e n n i f e r and E n r i q u e a l s o d i d not use a r e a s c o n s i s t e n t l y d u r i n g the s p r i n g of 1984. These movements do not f i t my d e f i n i t i o n of home range and a r e t h e r e f o r e o m i t t e d from the f o l l o w i n g a n a l y s i s of the e f f e c t of hare abundance on l y n x home range s i z e . I n c l u d i n g t h e s e movements i n the f o l l o w i n g a n a l y s i s would s t r e n g t h e n the ob s e r v e d t r e n d . As p r e v i o u s l y d i s c u s s e d ( F i g u r e 2 ) , hare d e n s i t i e s d e c l i n e d ' r a p i d l y t h r o u g h the e a r l y phases of the study and a t a l e s s e r r a t e l a t e r i n the s t u d y . Throughout t h i s d e c l i n e , l y n x showed a steady i n c r e a s e i n the s i z e of t h e i r home ranges. Both mean home range s i z e f o r a l l i n d i v i d u a l s a t d i f f e r e n t hare abundances ( F i g u r e 4) and home ranges of i n d i v i d u a l s m o n i t o r e d t h r o u g h time 22 F i g u r e 3. Examples of 100% ( s o l i d l i n e ) and 90% (dashed l i n e ) home range e s t i m a t e s . F i g u r e 3a,b and c r e p r e s e n t the home range of S i d a t hare d e n s i t i e s of 14.7, 3.3 and 2.2 hares/ha r e s p e c t i v e l y . F i g u r e 3d r e p r e s e n t s the home range of C a r l o s a t 0.5 h a r e s / h a . 24 T a b l e 4. Comparison of 100% and 90% home range a r e a s of l y n x . Snowshoe hare d e n s i t i e s a r e i n i t i a l d e n s i t i e s a t the s t a r t of each 3 month p e r i o d f o r which i n d i v i d u a l l y n x home ranges were c a l c u l a t e d . Lynx home ranges a r e i n square k i l o m e t e r s . * i n d i c a t e s t h a t a r e a not d e f i n e d as a home range. See t e x t f o r e x p l a n a t i o n . Number of l o c a t i o n s used t o dete r m i n e each home range i s i n p a r e n t h e s e s . 25 Lynx Hare d e n s i t y (hares/Ha) 100% home range s i z e (km 2) 90% home range s i z e (km 2) P e r c e n t d i f f e r e n c e Joy 14.7 12.0 (30) 7.3 (27) 39 S i d 14.7 3.3 2.2 33.4 (95) 104.3 (78) 41.7 (53) 13.3 (85) 31.0 (70) 27.9 (47) 60 70 33 S c r u f f 14.7 i .3 46.4 (61) 44.9 (63) 17.7 (54) 43.4 (56) 62 3 C h a r l i e 14.7 29.7 (54) 14.6 (48) 51 C a r l o s 1 .3 1 .0 0.5 0.2 28.8 (45) 22.4 (46) 113.9 (69) 76.8 (85) 15.8 (40) 16.1 (41) 58.1 (62) 52.4 (76) 45 28 49 32 Jean 1 .0 0.5 0.2 17.1 (31) 68.5 (65) 34.0 (97) 13.7 (28) 30.3 (58) 28.1 (87) 20 56 17 S c o t t i e 1 .0 55.4 (34) 27.6 (31 ) 50 J e n n i f e r 0.5 0.2 61.8 (50) 200.6* (7) 33.5 (45) 46 Rene 0.5 524.8 (31) 254.7* (28) 51 E n r i q u e 0.5 0.2 49.2 (55) 69.6* (12) 17.8 (49) 64 P a u l 0.5 86.7 (61) 53.9 (54) 38 26 F i g u r e 4. Mean home range s i z e f o r l y n x r e s i d i n g i n a r e a s w i t h i n d i c a t e d snowshoe hare d e n s i t i e s . Hare d e n s i t y i s t h e i n i t i a l d e n s i t y a t the s t a r t of each 3 month p e r i o d f o r which home ranges of i n d i v i d u a l l y n x were c a l c u l a t e d . V e r t i c a l b a r s i n d i c a t e 95% c o n f i d e n c e l i m i t s of mean. 60-1 0.0 1.0, ^ 5Ac ^ -0.9 -4.9 -15.0 INITIAL HARE DENSITY MNA/Ha 28 ( F i g u r e 5) showed t h i s t r e n d . T h i s t r e n d was s i m i l a r when p l o t t e d a g a i n s t e i t h e r i n i t i a l hare d e n s i t i e s or mean d e n s i t i e s f o r each t h r e e month p e r i o d . U s i n g i n i t i a l d e n s i t i e s reduced the v a r i a n c e and gave c l e a r e r t r e n d s . These r e s u l t s a r e t h e r e f o r e p r e s e n t e d as a f u n c t i o n of i n i t i a l hare d e n s i t i e s i n each 3 month p e r i o d . Between A p r i l and June 1982, the 4 r a d i o - t a g g e d l y n x u t i l i z i n g g r i d A ( e a r l y A p r i l hare d e n s i t y 14.7 hares/ha) had a mean home range s i z e of 13.2 (95% c . i . 8.8 t o 17.6) km 2. These i n d i v i d u a l s e i t h e r d i s p e r s e d or expanded t h e i r home ranges as hare d e n s i t y on the g r i d d e c l i n e d . Because hare d e n s i t i e s on g r i d A d e c l i n e d a t a d i f f e r e n t r a t e than s u r r o u n d i n g a r e a s , home range d a t a f o r i n d i v i d u a l s r e s i d i n g i n the 2 a r e a s i n d i f f e r e n t time p e r i o d s a r e lumped based on hare d e n s i t y . Lynx r e s i d i n g i n ar e a s w i t h hare d e n s i t i e s between 1.0 and 4.9 hares/ha had a mean home range s i z e of 25.1 (95% c . i . 14.5 t o 35.7) km 2. T h i s i s not a s i g n i f i c a n t i n c r e a s e i n home range s i z e over l y n x r e s i d i n g i n the a r e a w i t h an i n i t i a l hare d e n s i t y of 14.7 h a r e s / h a . D u r i n g the low p a r t of the hare c y c l e when d e n s i t i e s were l e s s than 1.0 hares/ha mean l y n x home range s i z e was s t i l l h i g h e r a t 39.2 (95% c . i . 23.7 t o 54.7) km 2. A l t h o u g h t h i s i s not a s i g n i f i c a n t i n c r e a s e over l y n x r e s i d i n g i n a r e a s w i t h hare d e n s i t i e s between 1.0 and 4.9 h a r e s / h a , i t i s s i g n i f i c a n t l y l a r g e r than the mean home range s i z e of l y n x r e s i d i n g i n a r e a s w i t h hare d e n s i t e s g r e a t e r than 4.9 hares/ha ( t - t e s t , P<0.05) In a d d i t i o n t o the o v e r a l l t r e n d towards l a r g e r home ranges as hare abundance d e c l i n e d , i n d i v i d u a l l y n x m o n i t o r e d t h r o u g h 29 F i g u r e 5. 90% home range s i z e s of i n d i v i d u a l l y n x a t i n d i c a t e d snowshoe hare d e n s i t y . Hare d e n s i t y i s the i n i t i a l d e n s i t y a t the s t a r t of each 3 month p e r i o d f o r which home range were c a l c u l a t e d . • JOY • SID A SCRUFF o CHARLIE • CARLOS • JEAN v SCOTTIE + JENNIFER A ENRIQUE x PAUL D 0 5 10 15 SNOWSHOE HARE DENSITY HARES/Ha 31 more than one 3 month time p e r i o d i n c r e a s e d t h e i r home range s i z e as hare abundance d e c l i n e d ( F i g u r e 5 ) . The o n l y e x c e p t i o n t o t h i s t r e n d was a s l i g h t d e c r e a s e i n the home range s i z e of S i d , c o n c u r r e n t w i t h a d e c l i n e i n hare abundance from 3.3 t o 2.2 h a r e s / h a i n the f a l l of 1982. W i t h the e x c e p t i o n of the s l i g h t d e c l i n e i n the home range s i z e of S i d a f t e r a p r e v i o u s i n c r e a s e , no t r e n d towards changes i n home range s i z e w i t h season was o b s e r v e d e i t h e r f o r i n d i v i d u a l s or i n g e n e r a l . At d e n s i t i e s below about 0.5 hares/ha t h e r e appears t o be a tendency f o r some i n d i v i d u a l s t o abandon t h e i r home ranges and become nomadic. A female (Rene), t h a t I r a d i o - t a g g e d and m o n i t o r e d , d u r i n g the summer of 1983, t r a v e l l e d e x t e n s i v e l y i n the g e n e r a l study area but used no a r e a c o n s i s t e n t l y enough t o be i d e n t i f i e d as her home range ( F i g u r e 6 ) . A f t e r b e i n g r a d i o -tagged i n l a t e J u l y 1983, she remained i n the a r e a f o r s e v e r a l days b e f o r e t r a v e l l i n g a p p r o x i m a t e l y 35 km S d u r i n g the next week. She c r o s s e d s e v e r a l l a r g e streams and a f a s t f l o w i n g r i v e r on t h i s t r e k . W i t h i n a month she had r e t u r n e d t o the i n i t i a l t a g g i n g a r e a . She remained i n the a r e a f o r a week b e f o r e d i s a p p e a r i n g f o r 4 days. On her r e t u r n , she t r a v e l l e d w i d e l y w i t h i n the g e n e r a l study a r e a u n t i l l a t e September. D u r i n g t h i s p e r i o d she t r a v e l l e d as much as 25 km t o the SE on s e v e r a l o c c a s i o n s . A l t h o u g h she d i d not use any area c o n s i s t e n t l y enough t o be i d e n t i f i e d as her home range, a summation of the innermost 90% of my l o c a t i o n s f o r her between J u l y and O c t o b e r , amounts t o an a r e a of 255 km 2. In mid December 1983, she was l o c a t e d a p p r o x i m a t e l y 35 km E of the 32 F i g u r e 6. Map of a r e a s d e l i n e a t e d by j o i n i n g outermost o b s e r v e d l o c a t i o n s of "nomadic" i n d i v i d u a l s . 34 i n i t i a l r a d i o - t a g g i n g s i t e and I b e l i e v e she s t a r v e d d u r i n g the p r e v i o u s w i n t e r . She was found dead i n t h i s a r e a i n June 1984. In a d d i t i o n , J e n n i f e r and E n r i q u e who, d u r i n g the summer of 1983, had m a i n t a i n e d d i s t i n c t home rang e s , were t r a v e l l i n g so w i d e l y d u r i n g May and June 1984 t h a t i t was i m p o s s i b l e t o m a i n t a i n c o n t i n u o u s c o n t a c t w i t h them. Based on 7 l o c a t i o n s , J e n n i f e r c o v e r e d a t o t a l a r e a of a t l e a s t 200 km 2 d u r i n g t h i s p e r i o d ( F i g u r e 6 ) . Based on 12 l o c a t i o n s , E n r i q u e wandered over a minimum ar e a of 60 km 2 d u r i n g the same p e r i o d . These a r e a s would undoubtedly have been l a r g e r i f i t had been p o s s i b l e t o mon i t o r t h e i r movements more f u l l y . N i n e t y p e r c e n t home ranges of l y n x o v e r l a p p e d c o n s i d e r a b l y w i t h i n and between sexes throughout the st u d y . Over the c o u r s e of the s t u d y , home range o v e r l a p averaged 10.5 (95% c . i . 0.6 t o 20.5), 24.5 (95% c . i . -21.7 t o 74.6), and 22.0 (95% c . i . 15.7 to 28.3) p e r c e n t f o r male-male, female-female and male-female i n t e r a c t i o n s r e s p e c t i v e l y . Male-male o v e r l a p was s i g n i f i c a n t l y l e s s than male-female o v e r l a p ( t - t e s t on a r c s i n t r a n s f o r m e d d a t a , P=0.04). No s i g n i f i c a n t d i f f e r e n c e was found between male-male and female-female home range o v e r l a p ( t - t e s t P=0.18). There was a l s o no s i g n i f i c a n t d i f f e r e n c e between female-female and female-male home range o v e r l a p ( t - t e s t P=0.70). Lynx home range o v e r l a p remained h i g h throughout the study and was not a f f e c t e d s i g n i f i c a n t l y by a b s o l u t e hare d e n s i t y i n an a r e a . O v e r l a p f o r the 4 i n d i v i d u a l s o c c u p y i n g the area of r e l a t i v e l y h i g h hare abundance (14.7 hares/ha) averaged 24.8 (95% c . i . 16.0 t o 33.5) p e r c e n t . Between J u l y and September 35 1983 hare d e n s i t y on my f o u r g r i d s was about 0.5 ha r e s / h a . Home range o v e r l a p f o r 5 l y n x r e s i d i n g i n an a d j a c e n t area d u r i n g t h i s p e r i o d was 20.5 (95% c . i . 13.9 t o 27.1) p e r c e n t . T h i s i s not a s i g n i f i c a n t d i f f e r e n c e ( t - t e s t on a r c s i n t r a n s f o r m e d d a t a , P=0.67). Based on snow t r a c k i n g I am c o n f i d e n t t h a t I had the m a j o r i t y of l y n x i n t h e s e two a r e a s r a d i o - t a g g e d i n these two time p e r i o d s . Home range o v e r l a p f o r r a d i o - t a g g e d i n d i v i d u a l s m o n i t o r e d a t hare d e n s i t i e s between th e s e extreme h i g h and low d e n s i t i e s ranged from 0.0 t o 36.9 p e r c e n t (mean 15.3, 95% c . i . -1.0 t o 26.4). T h i s i n d i c a t e s a h i g h degree of home range s h a r i n g a t a l l hare d e n s i t i e s , a l t h o u g h v a r i a t i o n i n degree of o v e r l a p between i n d i v i d u a l s was h i g h . E f f e c t of Snowshoe Hare Abundance on Lynx F o r a g i n g E f f o r t I assumed t h a t l y n x a r e f o r a g i n g whenever they a r e t r a v e l l i n g as d i d Brand et a l . (1976). Lynx f o r a g i n g e f f o r t was e s t i m a t e d by the s t r a i g h t - l i n e d i s t a n c e t r a v e l l e d per day (DTD). I c a l c u l a t e d t h i s by measuring the d i s t a n c e between t h e p o i n t s where an i n d i v i d u a l was l o c a t e d on c o n s e c u t i v e days. Lynx showed no s i g n i f i c a n t change i n t h e i r f o r a g i n g e f f o r t at snowshoe hare d e n s i t i e s above about 1.0 hares/ha ( F i g u r e 7 ) . At 14.7 hares/ha l y n x mean DTD was 2.7 km (95% c . i . 1.8 t o 3.7 km). At .1.0 hares/ha l y n x had a mean DTD of 2.4 km (95% c.. i . 2.0 t o 2.9 km). Below about 1.0 h a r e s / h a , however, l y n x i n c r e a s e t h e i r mean DTD r a p i d l y w i t h d e c l i n i n g hare d e n s i t y . At hare d e n s i t i e s of 36 F i g u r e 7. Mean s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e of l y n x v e r s u s snowshoe hare abundance. T r a v e l d i s t a n c e s a r e the mean f o r a l l i n d i v i d u a l s a t the i n d i c a t e d hare d e n s i t y . V e r t i c a l b a r s i n d i c a t e 95% c o n f i d e n c e l i m i t s of mean. DAILY TRAVEL DISTANCE km/day > m 03 0> 05 z o :> 0) I o m > m > 00 c z o > z o m o o J^" 01 CO cn 05 -^ i oo I • 1 LZ 38 0.5 h a r e s / h a , mean DTD was 3.3 km (95% c . i . 2.8 t o 3.7 km). As hare d e n s i t y d e c l i n e d s t i l l f u r t h e r t o 0.2 hares/ha mean l y n x DTD i n c r e a s e d s h a r p l y t o 5.3 km (95% c . i . 3.9 t o 7.2 km). T h i s i s a s i g n i f i c a n t l y l a r g e r d i s t a n c e than t h a t t r a v l l e d at 1.0 hares/ha ( t - t e s t P< 0.05). A d d i t i o n a l e v i d e n c e s u p p o r t i n g the i d e a t h a t l y n x i n c r e a s e f o r a g i n g e f f o r t w i t h d e c l i n i n g hare abundance i s the maximum d a i l y t r a v e l d i s t a n c e r e c o r d e d a t h i g h and low hare d e n s i t y ( F i g u r e 8 ) . These d a t a show the same g e n e r a l t r e n d a s do mean DTD. At 14.7 h a r e s / h a t h e maximum DTD I r e c o r d e d was 5.8 km. T h i s s t a y e d r e l a t i v e l y c o n s t a n t t o 1.0 hares/ha when maximum r e c o r d e d DTD was s t i l l 6.3 km. As hare d e n s i t i e s d e c l i n e d t o 0.5 and then t o 0.2 hares/ha maximum DTD i n c r e a s e d t o 17.5 and 14.6 km r e s p e c t i v e l y , showing a d e c r e a s e a t e x t r e m e l y low hare d e n s i t y . E f f e c t of Snowshoe Hare P i s t r i b u t i o n on Lynx F o r a g i n g P a t t e r n s W h i l e t r y i n g t o c a p t u r e l y n x f o r r a d i o - t a g g i n g , I o b t a i n e d d a t a t o show how they were c o n c e n t r a t i n g i n a r e a s of h i g h prey d e n s i t y . Between A p r i l 1 and May 10 1982, hare d e n s i t y on g r i d A d e c l i n e d from 14.7 t o 8.4 hares/ha w h i l e hare d e n s i t y on g r i d B d e c l i n e d from 2.6 t o 0.4 hares/h a ( F i g u r e 2 ) . D u r i n g t h i s p e r i o d , 3 l y n x ( J o y , S c r u f f and S i d ) were c a p t u r e d i n 234 t r a p -n i g h t s w i t h i n a 1 km r a d i u s of g r i d A (T a b l e 1 ) . From t r a c k s and the c a p t u r e of an o t h e r l y n x ( C h a r l e y ) i n the same ar e a on 39 F i g u r e 8. Maximum observed s t r a i g h t - l i n e t r a v e l d i s t a n c e a l l l y n x i n each 3 month p e r i o d f o r which home ranges were c a l c u l a t e d . MAXIMUM OBSERVED DAILY TRAVEL DISTANCE KM ro oi o 01 o 41 May . 25, i t i s b e l i e v e d t h a t two o t h e r l y n x were a l s o u t i l i z i n g the a r e a a t the same t i m e . Subsequent r a d i o - t r a c k i n g of the s e f o u r l y n x i n d i c a t e d a minimum d e n s i t y of 1 l y n x per 7.3 km 2 i n the a r e a of g r i d A. An e q u a l number of t r a p - n i g h t s on g r i d B d u r i n g the same p e r i o d r e s u l t e d i n no c a p t u r e s . Two hundred and f o r t y s i x t r a p - n i g h t s i n the a r e a of g r i d A i n October and November 1982, a f t e r hare d e n s i t y on the g r i d had d e c l i n e d t o a p p r o x i m a t e l y 1.8 h a r e s / h a , r e s u l t e d i n no c a p t u r e s . Track t r a n s e c t s t h r o u g h both g r i d s A and B i n the s p r i n g and t h r o u g h g r i d A d u r i n g the e a r l y w i n t e r of 1982, a f t e r hare d e n s i t e s had d e c l i n e d , a l s o i n d i c a t e d t h a t l y n x sought out and c o n c e n t r a t e d t h e i r f o r a g i n g e f f o r t s i n a r e a s of r e l a t i v e l y h i g h hare abundance (Table 5 ) . In A p r i l 1982 when hare d e n s i t y dropped from 14.7 t o 9.5 hares/h a on g r i d A, the mean number of s e t s of l y n x t r a c k s c r o s s i n g a 600 m t r a n s e c t was 5.0 (95% c . i . 0.7 t o 9.3). At the same t i m e , when hare d e n s i t y on g r i d B was d e c l i n i n g from 2.7 t o 1.2 h a r e s / h a , the mean number of s e t s of l y n x t r a c k s c r o s s i n g each 600 m t r a n s e c t was 0.8 (95% c . i . -0.1 t o 1.6). Thus, l y n x used the a r e a of h i g h e r hare abundance s i g n i f i c a n t l y more ( G a d j . t e s t P= 0.005). Lynx abandoned the a r e a s of r e l a t i v e l y h i g h hare abundance when they were d e p l e t e d . As hare d e n s i t y on g r i d A d e c l i n e d from 14.7 t o 2.2 h a r e s / h a , 3 of the 4 l y n x I had r a d i o - t a g g e d i n the a r e a d i s p e r s e d . Hare d e n s i t y i n the s u r r o u n d i n g a r e a s was d e c l i n i n g from 1.9 t o 1.4 hares/ha d u r i n g t h i s p e r i o d . In November 1982 when hare d e n s i t y on g r i d A had d e c l i n e d t o 1.8 h a r e s / h a , the mean number of s e t s of l y n x t r a c k s per 600 42 T a b l e 5. E f f e c t of r e l a t i v e snowshoe hare abundance on l y n x f o r a g i n g p a t t e r n s . *' and * 2 i n d i c a t e a s i g n i f i c a n t d i f f e r e n c e (Gadj. T e s t P= 0.005). TN i n d i c a t e s the t o t a l number of t r a p - n i g h t s of e f f o r t . 43 G r i d Hare d e n s i t y (hares/Ha) Number of l y n x caught/1 00 t r a p - n i g h t s S e t s of l y n x t r a c k s / 6 0 0 meter t r a n s e c t (mean & 95% c.i.) A A p r i l / 8 2 14.7 1 .3 (234 TN) 5.0 (0.7 t o 9.3) * 1 * 2 B A p r i l / 8 2 2.6 0.0 (234 TN) 0.8 (-0.1 t o 1.6 * i A Nov./82 1 .8 0.0 (246 TN) 1.2 (0.0 t o 2.3) * 2 44 m t r a n s e c t d e c l i n e d t o 1.1 (95% c . i . 0.0 t o 2.3). T h i s i s a s i g n i f i c a n t r e d u c t i o n i n u t i l i z a t i o n of the a r e a f o l l o w i n g the d e c l i n e i n hare abundance (Gadj. t e s t , P = 0.005). There was no s i g n i f i c a n t d i f f e r e n c e i n the i n t e n s i t y of l y n x use of g r i d B i n A p r i l and g r i d A i n November when hare d e n s i t i e s were s i m i l a r ( Gadj. t e s t P>0.05). A second area of l y n x c o n c e n t r a t i o n was noted between. J u l y and September 1983 a p p r o x i m a t e l y 15 km SE of g r i d A a l o n g the o l d A l a s k a Highway. F i v e l y n x r e s i d e d w i t h i n a t o t a l a r e a of 99 km 2 f o r a d e n s i t y of 1 l y n x per 19.8 km 2. T h i s d e n s i t y i s lower than t h a t noted on g r i d A. As p r e v i o u s l y mentioned, the degree of home range o v e r l a p f o r i n d i v i d u a l s r e s i d i n g on g r i d A and t h i s second area of c o n c e n t r a t i o n was not s i g n i f i c a n t l y d i f f e r e n t . The degree of home range o v e r l a p i n t h e s e 2 a r e a s was g e n e r a l l y h i g h e r than noted elsewhere i n the s t u d y . U n f o r t u n a t e l y , I do not have d a t a on hare d i s t r i b u t i o n i n t h i s second a r e a . Lynx P i s p e r s a l and M o r t a l i t y d u r i n g a P e c l i n e i n Snowshoe Hare Abundance P u r i n g the s t u d y o n l y 3 of the 11 r a d i o - t a g g e d l y n x s u r v i v e d f o r 1 year or more and remained w i t h i n the study a r e a . D i s p e r s a l or human r e l a t e d m o r t a l i t y were r e s p o n s i b l e f o r the l o s s of 7 l y n x . One l y n x d i e d of n a t u r a l causes i n the s p r i n g of 1984 (Table 2 ) . Between A p r i l and November 1982, I r a d i o - t a g g e d 7 l y n x . By 45 A p r i l , 1983, o n l y 2 were s t i l l a l i v e and r e s i d i n g w i t h i n the study a r e a . Three of the 7 ( J o y , C h a r l e y and S c r u f f ) d i s p e r s e d 250-700 km b e f o r e b e i n g t r a p p e d and k i l l e d by p r o f e s s i o n a l t r a p p e r s ( F i g u r e 9 ) . A l l 3 of t h e s e l y n x were r a d i o - t a g g e d on g r i d A between A p r i l 4 and May 25 1982. These i n d i v i d u a l s had minimum r e s i d e n c y t i m e s i n the a r e a of 35 days, 40 days and 7 months r e s p e c t i v e l y . One of the fe m a l e s (Joy) was a t l e a s t 2 y e a r s o l d and the o t h e r 2 i n d i v i d u a l s were a t l e a s t 1 year o l d . D u r i n g the p e r i o d when Joy and C h a r l e y d i s p e r s e d , g r i d A had s i g n i f i c a n t l y h i g h e r d e n s i t i e s than s u r r o u n d i n g a r e a s but hare d e n s i t y on the g r i d was d e c l i n i n g r a p i d l y ( F i g u r e 2 ) . Joy t r a v e l l e d a t l e a s t 700 km i n the next 8 months b e f o r e being, c a p t u r e d and k i l l e d i n mid-December i n NE A l a s k a . C h a r l e y was t r a p p e d and k i l l e d a p p r o x i m a t e l y 250 km N of the study a r e a i n mid-December 1982. S c r u f f moved her home range t o a p p r o x i m a t e l y 5 km SE of g r i d A i n J u l y 1982 'and d i s p e r s e d from the study a r e a i n Oc t o b e r . She was t r a p p e d and k i l l e d i n mid-November w i t h i n 50 km of the a r e a where C h a r l e y was k i l l e d near P e l l y C r o s s i n g , Yukon. J o y , C h a r l e y and S c r u f f had minimum d i s p e r s a l r a t e s of 3.8, 1.7 and 8.3 km/day r e s p e c t i v e l y t o t r a v e l the d i s t a n c e s c o v e r e d by the s e l y n x i n the time t a k e n , i f I assume s t r a i g h t -l i n e t r a v e l . A l l d i s p e r s a l s from the s t u d y a r e a o c c u r r e d d u r i n g the snow-free p e r i o d from May t o O c t o b e r . Two a d d i t i o n a l l y n x ( S i d and S c o t t i e ) were a l s o t r a p p e d and k i l l e d w i t h i n 10 km of t h e i r o r i g i n a l r a d i o - t a g g i n g s i t e d u r i n g the w i n t e r of 1982-83. A l l 5 l y n x were t r a p p e d w i t h i n 2.5 46 F i g u r e 9. Map of lon g d i s t a n c e d i s p e r s a l s undertaken by l y n x . S t a r i n d i c a t e s i n i t i a l r a d i o - t a g g i n g s i t e f o r a l l i n d i v i d u a l s . X,,^and X j i n d i c a t e s i t e s where C h a r l i e and S c r u f f and Joy r e s p e c t i v e l y were t r a p p e d and k i l l e d . See Table 2 and t e x t f o r d a t e of i n i t i a l r a d i o - t a g g i n g , date k i l l e d and d i s p e r s a l r a t e s . 48 months of the s t a r t of t r a p p i n g season. T h i s r e p r e s e n t s 71% of my r a d i o - tagged p o p u l a t i o n and 100% of the a n i m a l s t h a t l e f t the game s a n c t u a r y . The 2 l y n x (Jean and C a r l o s ) t h a t remained i n the Kluane Game San c t u a r y i n l a t e f a l l 1982 were s t i l l p r e s e n t the f o l l o w i n g s p r i n g . Between J u l y and September 1983, 4 a d d i t i o n a l l y n x were r a d i o - t a g g e d w i t h i n the game s a n c t u a r y . I obser v e d no l o n g d i s t a n c e d i s p e r s a l , of the type o b s e r v e d the p r e c e d i n g year d u r i n g r a p i d d e c l i n e i n snowshoe hare abundance. D u r i n g the w i n t e r of 1983-84, 2 of my 6 r a d i o - t a g g e d l y n x were t r a p p e d and k i l l e d w i t h i n 10 km of t h e i r i n i t i a l c a p t u r e s i t e . T h i s r e p r e s e n t s 33% of my r a d i o - t a g g e d p o p u l a t i o n and 50% of the l y n x known t o have t r a v e l l e d o u t s i d e the game s a n c t u a r y . One l y n x (Rene) s t a r v e d and was found dead i n June 1984 n o r t h of Haines J u n c t i o n , 35 km e a s t of her i n i t i a l c a p t u r e s i t e . The c a r c a s s was e x t r e m e l y e m a c i a t e d , and I b e l i e v e she s t a r v e d d u r i n g the w i n t e r . T r a p p i n g was r e s p o n s i b l e f o r 7 of 8 deaths of l y n x observed i n t h i s s t u d y . F u r t h e r m o r e , o n l y 2 of the 9 i n d i v i d u a l s known t o t r a v e l o u t s i d e the game s a n c t u a r y d u r i n g the t r a p p i n g season were not t r a p p e d . 49 DISCUSSION The r e s u l t s of t h i s study i n d i c a t e - t h a t l y n x respond b e h a v i o r a l l y t o d e c l i n i n g snowshoe hare abundance. In the f o l l o w i n g s e c t i o n s I w i l l d i s c u s s the e f f e c t i v e n e s s of these r e s p o n s e s i n the l y n x ' s e f f o r t s t o c o n t i n u e t o f u l f i l l i t s e n e r g e t i c needs as hare abundance d e c l i n e s . Lynx Home Range S i z e Mean home range s i z e f o r l y n x i n t h i s study i n c r e a s e d 3 f o l d c o n c u r r e n t w i t h a d e c l i n e i n snowshoe hare abundance from 14.7 t o about 0.2 h a r e s / h a . T h i s i n c r e a s e was s u f f i c i e n t t o c o m p l e t e l y overshadow any e f f e c t of sex, age, or season on home range s i z e . In c o n t r a s t t o t h i s s t u d y , Brand e t a l . (1976) found no r e l a t i o n s h i p between l y n x home range s i z e and e i t h e r l y n x or snowshoe hare d e n s i t y . The reason f o r t h i s d i f f e r e n c e i s u n c l e a r but may be a t l e a s t p a r t i a l l y a f u n c t i o n of d i f f e r e n c e s i n t h e t e c h n i q u e used t o a s s e s s home range s i z e . The work of Brand e t a l . (1976) was conducted u s i n g w i n t e r snow t r a c k i n g . The l i m i t a t i o n s of t h i s t e c h n i q u e have been p o i n t e d out by Mech (1980): "(1) e r r o r s a r e p o s s i b l e i n i d e n t i f y i n g i n d i v i d u a l l y n x e s by t r a c k s from day t o day, (2) o b s e r v a t i o n s a re r e s t r i c t e d t o w i n t e r , (3) the a r e a of s e a r c h i s l i m i t e d , and (4) the sexes of the study a n i m a l s o f t e n cannot be de t e r m i n e d " . 50 P o i n t s 1 and 3 may be r e s p o n s i b l e f o r the l a c k of an i n c r e a s e i n home range s i z e found by Brand e t a l . (1976). I t i s p o s s i b l e t h a t the e x p a n s i o n of i n d i v i d u a l l y n x home ranges i n t o unmonitored a r e a s went u n d e t e c t e d . I f an i n d i v i d u a l expanded i t s home range i n t o the range of a n o t h e r , t h i s e x p a n s i o n may have gone u n d e t e c t e d because of m i s i d e n t i f i c a t i o n of the t r a c k s . Brand e t a l . a l s o s t a t e d t h a t home range s i z e was a f u n c t i o n of sam p l i n g i n t e n s i t y , and home ranges i n t h e i r study would p r o b a b l y have c o n t i n u e d t o i n c r e a s e w i t h a d d i t i o n a l k i l o m e t e r s of s n o w - t r a c k i n g . A l t h o u g h t e c h n i c a l d i f f e r e n c e s may e x p l a i n some of the v a r i a t i o n i n home range s i z e s r e p o r t e d f o r l y n x , I f e e l t h a t the o v e r - r i d i n g f a c t o r i s food abundance. Home range s i z e s r e p o r t e d f o r l y n x i n p r e v i o u s s t u d i e s span over an o r d e r of magnitude. Brand e t a l . (1976) and P a r k e r e t a l . ( 1 9 8 3 ) , working i n a r e a s of r e l a t i v e l y h i g h snowshoe hare abundance, r e p o r t e d l y n x home ranges between 7.9 and 49.5 km 2. Carbyn and P a t r i q u i n (1983) found l y n x home ranges of between 138 and 221 km 2 d u r i n g a p e r i o d of r a p i d i n c r e a s e i n hare abundance. Mech (1980), r e p o r t e d l y n x home ranges of 51 t o 243 km 2 and suggested t h a t low prey abundance may have been r e s p o n s i b l e f o r the l a r g e home ranges. Saunders (1963b) found l y n x home ranges between 15.5 and 20.7 km 2 a t low hare d e n s i t i e s . H i s e s t i m a t e s a r e based on l i m i t e d w i n t e r snow t r a c k i n g which may not have been s u f f i c i e n t t o d e l i n e a t e the e n t i r e home ranges. I f I i n c l u d e the area c o v e r e d by Rene d u r i n g the summer of 1983, my 90% home ranges span from the s m a l l e s t t o the l a r g e s t p r e v i o u s l y r e p o r t e d . 51 The concept of i n c r e a s i n g f e e d i n g t e r r i t o r y or home range s i z e w i t h d e c l i n i n g food abundance i s i n t u i t i v e l y r e a s o n a b l e and has been d i s c u s s e d i n t h e o r e t i c a l terms by s e v e r a l a u t h o r s ( D i l l 1978, H a r e s t a d and B u n n e l l 1979, Hixon 1980, and McNab 1963 among o t h e r s ) . F i e l d e v i d e n c e f o r i n c r e a s i n g home range s i z e has come from such wide r a n g i n g systems as r e p t l i e s ( K r e k o r i a n 1976, Simon 1975), b i r d s (see D i l l , 1978 and Schoener, 1968 f o r r e v i e w s ) , mammals ( AHaber e t a l . 1976) and f i s h ( S l a n e y and N o r t h c o t e 1974). A l t h o u g h i n c r e a s i n g home range s i z e would o b v i o u s l y not i n c r e a s e f o r a g i n g s u c c e s s i n terms of c a t c h per u n i t e f f o r t , i t would mean t h a t the food r e s o u r c e s w i t h i n the i n d i v i d u a l s home range would not be d e p l e t e d as r a p i d l y . T h i s i s e v i d e n t from my d a t a . The 4 l y n x u s i n g the a r e a around g r i d A i n May 1982 had a mean home range s i z e of 13.2 km 2. Assuming u n i f o r m hare d e n s i t y throughout the a r e a each l y n x home range would c o n t a i n about 19,400 h a r e s . I f a l y n x had e x c l u s i v e use of t h i s home range and r e q u i r e d 0.5 hares/day f o r maintenance, t h i s hare p o p u l a t i o n would l a s t the l y n x over 106 y e a r s . Even w i t h the 4 l y n x s h a r i n g a t o t a l a r e a of 29.2 km 2 t h i s hare d e n s i t y would l a s t them 58.8 y e a r s . I t t h e r e f o r e seems t h a t l y n x home ranges a t t h i s time were w e l l i n e x c e s s of t h e i r immediate needs. F u r t h e r m o r e , i t seems u n l i k e l y t h a t the d e c l i n e i n the hare p o p u l a t i o n i n t h i s a r e a can be a t t r i b u t e d t o l y n x p r e d a t i o n a l o n e . At 2 hares/ha when l y n x home ranges a v e r a g e d 25.1 km 2 the s t a n d i n g c r o p of h a r e s w i t h i n i t s home range, a g a i n assuming e x c l u s i v e use, would l a s t an i n d i v i d u a l l y n x 27 y e a r s . At- 0.5 hares/ha the e x i s t i n g hare p o p u l a t i o n 52 w i t h i n the average l y n x home range of 39.2 km 2 would l a s t about 10.7 y e a r s . O v e r l a p p i n g home ranges would d e c r e a s e t h i s time s t i l l f u r t h e r and the hare p o p u l a t i o n ( w i t h o u t r e c r u i t m e n t ) w i t h i n the 99.0 km 2 shared by 5 r e s i d e n t s i n the summer of 1983 would l a s t them o n l y about 5.4 y e a r s . These c a l c u l a t i o n s show t h a t the i n c r e a s e i n l y n x home range s i z e i n response t o d e c l i n i n g hare abundance was not s u f f i c i e n t t o m a i n t a i n a c o n s t a n t s i z e hare p o p u l a t i o n w i t h i n t h e i r home range. These e s t i m a t e s o b v i o u s l y o v e r - e s t i m a t e the amount of time t h a t l y n x c o u l d s u r v i v e on the hares e x i s t i n g w i t h i n i t s home range. I t assumes t h a t l y n x a r e s u f f i c i e n t l y e f f i c i e n t p r e d a t o r s t o t o t a l l y d e p l e t e t h e i r home range. Prey abundance w i t h i n a p r e d a t o r s home range cannot be e x t r a p o l a t e d d i r e c t l y t o prey a v a i l a b i l i t y f o r the p r e d a t o r . As prey abundance d e c l i n e s t h e p r e d a t o r w i l l have t o expend more e f f o r t t o f i n d and c a p t u r e each prey i t e m . A d o u b l i n g of a l y n x ' s home range s i z e i n response t o a h a l v i n g of snowshoe hare abundance would t h e r e f o r e not r e s u l t i n e q u i v a l e n t prey a v a i l a b i l i t y f o r the l y n x . I t a l s o assumes t h a t no o t h e r p r e d a t o r s a r e h a r v e s t i n g snowshoe ha r e s w i t h i n the l y n x ' s home range. I noted i n t h i s s tudy t h a t r a p t o r s and o t h e r mammals were a l s o i m p o r t a n t p r e d a t o r s on snowshoe h a r e s , and a l s o seemed t o c o n c e n t r a t e i n ar e a s of r e l a t i v e l y h i g h prey abundance. I f prey d i s t r i b u t i o n i s not u n i f o r m w i t h i n the environment, by expanding i t s home range, the i n d i v i d u a l would a l s o i n c r e a s e the chance of h a v i n g r e l a t i v e l y good p a t c h e s of pre y w i t h i n i t s home range. T h i s would be e s p e c i a l l y i m p o r t a n t t o a l y n x d u r i n g 53 a snowshoe hare d e c l i n e i f the few r e m a i n i n g hares a re c o n c e n t r a t e d w i t h i n r e f u g i a as suggested by W o l f f (1980). T h i s w i l l be d i s c u s s e d i n more d e t a i l i n the l a t e r s e c t i o n on p a t c h u t i l i z a t i o n by l y n x . Three l y n x abandoned t h e i r home ranges and became nomadic at hare d e n s i t i e s below about 0.5 ha r e s / h a . S i m i l a r p a t t e r n s have been r e p o r t e d f o r o t h e r f e l i d s . Hanby and B y g o t t (1979) found t h a t the number of nomadic female l i o n s wandering through the s u b o p t i m a l h a b i t a t of the S e r e n g e t i P l a i n s d e c l i n e d and some of t h e s e p r e v i o u s l y nomadic females became r e s i d e n t when pr e y abundance i n c r e a s e d . B a i l e y (1981) r e p o r t e d t h a t bobcats t h a t defended t e r r i t o r i e s d u r i n g p e r i o d s of prey abundance a l s o became nomadic a f t e r prey abundance d e c l i n e d . He suggested t h a t i f p rey abundance i s u n p r e d i c t a b l e , or v e r y low, i t would be a d a p t i v e f o r bob c a t s t o become t r a n s i e n t and s e a r c h out w i d e l y s e p e r a t e d c o n c e n t r a t i o n s of p r e y . These arguments h o l d e q u a l l y w e l l f o r l y n x . At d e n s i t i e s below about 0.5 h a r e s / h a , l y n x may not be a b l e t o f u l f i l l t h e i r e n e r g e t i c r e q u i r e m e n t s and must seek out p a t c h e s of r e l a t i v e l y h i g h prey abundance. I do not have good i n f o r m a t i o n on the s p a t i a l and t e m p o r a l d i s t r i b u t i o n snowshoe h a r e s i n my ar e a but i f the r e f u g i a a r e w i d e l y spaced i t may be n e c e s s a r y f o r l y n x t o wander g r e a t d i s t a n c e s i n s e a r c h of them. Mean home range o v e r l a p f o r l y n x exceeded 10.5% both w i t h i n and between sexes throughout t h i s s t u d y . F u r t h e r , a b s o l u t e snowshoe hare d e n s i t y had no e f f e c t on the degree of home range o v e r l a p between l y n x . The degree of home range o v e r l a p a t 54 extreme h i g h and low hare d e n s i t i e s i n t h i s s t u d y were not s i g n i f i c a n t l y d i f f e r e n t . Schoener (1968) suggested t h a t t e r r i t o r i a l i t y i s i n v e r s e l y p r o p o r t i o n a l t o the degree of home range o v e r l a p between i n d i v i d u a l s . B a i l e y (1974) found home ranges of t e r r i t o r i a l b o b c a t s o v e r l a p p e d 0.1 and 2.0 p e r c e n t f o r male w i t h males, females w i t h females r e s p e c t i v e l y . The h i g h degree of home range o v e r l a p w i t h i n and between a l l sexes i n t h i s s tudy i s s t r o n g e v i d e n c e t h a t l y n x a re not t e r r i t o r i a l a t l e a s t d u r i n g the p e r i o d of d e c l i n e and low snowshoe hare abundance. P r e v i o u s s t u d i e s show no c o n s i s t e n t t r e n d i n the r e l a t i v e e x c l u s i v e n e s s of l y n x home ranges w i t h i n and between se x e s . N e l l i s e t a l . (1972) r e p o r t e d t h a t l y n x tend t o be s e p a r a t e d i n time and space. Brand e t a l . (1976) r e i t e r a t e d t h i s s t a t i n g t h a t " a v o i d a n c e b e h a v i o r appears t o s e p a r a t e l y n x i n both time and space, but p r o b a b l y does not a c t l o c a l l y as a d e n s i t y -l i m i t i n g mechanism". B e r r i e (1974) found t h a t female l y n x were " l e s s t o l e r a n t of each o t h e r than were males". In h i s study the home ranges of males o v e r l a p p e d w i t h each o t h e r and w i t h n e i g h b o u r i n g females w h i l e female home ranges d i d not o v e r l a p . Mech (1980) r e p o r t e d t h a t female home ranges o v e r l a p p e d w h i l e t h o s e of males d i d not. In h i s s t u d y , home ranges of male l y n x a l s o o v e r l a p p e d l i t t l e w i t h those of f e m a l e s . P a r k e r e t a l . (1983) r e p o r t e d e x t e n s i v e o v e r l a p i n the home ranges of the a d u l t male and female i n h i s s t u d y . The home ranges of these two a d u l t s d i d not o v e r l a p w i t h t h a t of a j u v e n i l e female which he presumed t o t o be the o f f s p r i n g of h i s a d u l t female. Carbyn 55 and P a t r i q u i n (1983) found the home ranges of two females w i t h k i t t e n s o v e r l a p p e d but i t was u n c e r t a i n whether t h e home range of the male i n t h e i r study o v e r l a p p e d w i t h t h a t of the fe m a l e s . The l a c k of a c o n s i s t e n t p a t t e r n i n the degree of l y n x home range o v e r l a p i s p u z z l i n g . One p o s s i b l e e x p l a n a t i o n i s t h a t the t o t a l l y n x p o p u l a t i o n w i t h i n the study a r e a s of the s e s t u d i e s was not m o n i t o r e d . The home ranges of unmonitored l y n x may have o v e r l a p p e d e x t e n s i v e l y w i t h those of m o n i t o r e d l y n x i n some c a s e s . The p a t t e r n s of o v e r l a p r e p o r t e d i n the l i t e r a t u r e would t h e r e f o r e be a f u n c t i o n of which a n i m a l s i n the p o p u l a t i o n happened t o be m o n i t o r e d . A second p o s s i b i l i t y i s t h a t the s p a t i a l d i s t r i b u t i o n of l y n x i s a f u n c t i o n of s u b t l e e n v i r o n m e n t a l v a r i a b l e s . Under v a r i o u s c o n d i t i o n s d i f f e r e n t degrees of home range o v e r l a p w i t h i n and between sexes i s t o l e r a t e d . No i n d i c a t i o n of what the s e e n i r o n m e n t a l f a c t o r s might be or how they might a c t i s e v i d e n t from a review of p a s t s t u d i e s . I f any b e h a v i o r a l s p a c i n g mechanism e x i s t s i n l y n x p o p u l a t i o n s , i t i s e a s i l y o v e r - r i d d e n by p r o x i m a t e e n v i r o n m e n t a l f a c t o r s such as snowshoe hare d i s t r i b u t i o n (see d i s c u s s i o n of p a t c h u t i l i z a t i o n by l y n x ) . 56 E f f e c t of Snowshoe Hare Abundance on Lynx F o r a g i n g E f f o r t Lynx i n t h i s study i n c r e a s e d t h e i r mean s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e from 2.7 km/day a t h i g h hare d e n s i t y t o 5.3 km/day a t low hare d e n s i t y . In c o n t r a s t , N e l l i s and K e i t h (1968), Brand et a l . (1976), P a r k e r (1981) and P a r k e r e t a l . (1983) a l l found no c o r r e l a t i o n between snowshoe hare abundance and the d i s t a n c e t h a t l y n x t r a v e l l e d per day. N e l l i s and K e i t h (1968) and Brand et a l . (1976) found t h a t w i n t e r d a i l y t r a v e l d i s t a n c e s (DTD) of l y n x f l u c t u a t e d markedly from year t o y e a r , independent of hare abundance. Brand et a l . (1976) found a s i g n i f i c a n t n e g a t i v e c o r r e l a t i o n between l y n x d a i l y t r a v e l d i s t a n c e and h u n t i n g s u c c e s s . P a r k e r (1981) found t h a t l y n x d a i l y t r a v e l d i s t a n c e remained c o n s t a n t a t about 8 km/day as hare abundance d e c l i n e d t h r o u g h one w i n t e r . He found, however, t h a t h u n t i n g s u c c e s s , i n terms of k i l l s per a t t e m p t , i n c r e a s e d t h r o u g h the w i n t e r . He c o n c u r r e d w i t h N e l l i s and K e i t h (1968), and Brand et a l . (1976) t h a t d a i l y t r a v e l d i s t a n c e was p r i m a r i l y a f u n c t i o n of h u n t i n g s u c c e s s i n terms of k i l l s / k m . Brand et a l . (1976) and P a r k e r (1981) suggest t h a t h u n t i n g s u c c e s s , and t h e r e f o r e d a i l y t r a v e l d i s t a n c e , i s a f u n c t i o n of snow c o n d i t i o n s and i n d i v i d u a l h u n t i n g s k i l l s . I found, however, t h a t a t hare d e n s i t i e s above 1.0 hares/ha l y n x d i d not i n c r e a s e t h e i r DTD s i g n i - f - i c a n t l y w i t h d e c l i n i n g hare abundance i n summer, when snow c o n d i t i o n s c o u l d not be a f f e c t i n g h u n t i n g s u c c e s s . F u r t h e r , i f (1) d a i l y t r a v e l d i s t a n c e i s an i n v e r s e f u n c t i o n of h u n t i n g s u c c e s s i n terms of k i l l s per day and (Brand et a l . 1976, P a r k e r 1981), (2) t h e r e 57 i s no r e l a t i o n s h i p between k i l l s per attempt and hare d e n s i t y (Brand et a l . 1976), and (3) attempted k i l l s per km t r a v e l l e d d e c l i n e w i t h d e c l i n i n g hare d e n s i t y (Brand et a l . 1976), l y n x s h o u l d t r a v e l f u r t h e r as hare abundance d e c l i n e s i n an e f f o r t t o f u l f i l l t h e i r e n e r g e t i c r e q u i r e m e n t s . Below hare d e n s i t i e s of 1.0 h a r e s / h a , however, l y n x showed a d r a m a t i c i n c r e a s e d i n f o r a g i n g e f f o r t i n a l l seasons. The s t u d i e s of both Brand et a l . (1976) and P a r k e r e t a l . (1983), were conducted at hare d e n s i t i e s of 0.7 h a r e s / h a or h i g h e r . ^ N e l l i s and K e i t h (1968) worked a t hare d e n s i t i e s below 0.7 h a r e s / h a . They used w i n t e r s n o w - t r a c k i n g t o c o l l e c t t h e i r d ata and r e p o r t e d o n l y i n s t a n c e s where l y n x "beds used on c o n s e c u t i v e n i g h t s c o u l d be e s t a b l i s h e d w i t h c e r t a i n t y " . I t may be t h a t on days when l y n x t r a v e l l e d u n u s a l l y l o n g d i s t a n c e s , i t was not p o s s i b l e f o r them t o e s t a b l i s h the t o t a l d i s t a n c e t r a v e l l e d and these d a t a were t h e r e f o r e o m i t t e d . In any e v e n t , the most d r a m a t i c i n c r e a s e i n l y n x f o r a g i n g e f f o r t o c c u r s a t v e r y low hare d e n s i t i e s . My r e s u l t s above 0.5 hares/ha t h e r e f o r e are i n g e n e r a l agreement w i t h those of Brand et a l . (1976) and P a r k e r et a l . ( 1983) . 58 I c a l c u l a t e d e x p e c t e d t o t a l d a i l y t r a v e l d i s t a n c e s f o r l y n x a t d i f f e r e n t hare d e n s i t i e s u s i n g the e q u a t i o n : e x p e c t e d d a i l y t r a v e l d i s t a n c e maintenance l e v e l ^energy requirement. Y i n t e r c e p t of r e g r e s s i o n l i n e f o r a t t e m p t e d k i l l s per km _ s l o p e of r e g r e s s i o n l i n e hare a t t a c k X d e n s i t y X s u c c e s s r a t e U s i n g d a t a from Brand e t a l . (1976) I s e t a t f o l l o w i n g parameter v a l u e s ; maintenance l e v e l energy r e q u i r e m e n t = 0.5 hares/day Y i n t e r c e p t of r e g r e s s i o n l i n e = 17.5 s l o p e of r e g r e s s i o n l i n e = 0.075 a t t a c k s u c c e s s r a t e ( p r o p o r t i o n of s u c c e s s f u l a t t a c k s ) = .23 In c o n t r a s t t o Brand e t a l . ( l 9 7 6 ) , P a r k e r e t a l . (1983) found t h a t l y n x k i l l an average of 1 hare per day. S u b s t i t u t i n g t h i s h i g h e r k i l l r a t e i n the above e q u a t i o n would r e s u l t i n a d o u b l i n g of the e x p e c t e d d a i l y t r a v e l d i s t a n c e s . P a r k e r (1981) a l s o r e p o r t e d an average i n d i v i d u a l h u n t i n g s u c c e s s r a t e of 17%. T h i s lower v a l u e would a g a i n t e n d t o i n c r e a s e the e x p e c t e d d a i l y t r a v e l d i s t a n c e s . U s i n g a range of hare abundances I d e r i v e d the e x p e c t e d d a i l y t r a v e l d i s t a n c e c u r v e shown as l i n e A i n F i g u r e 10. From 59 F i g u r e 10. Observed and e x p e c t e d t o t a l d a i l y t r a v e l d i s t a n c e s f o r l y n x v e r s u s snowshoe hare abundance. For d e r i v a t i o n of l i n e s A, B and C see t e x t . EXPECTED TOTAL DAILY TRAVEL DISTANCE (KM) 61 N e l l i s and K e i t h (1968) and Saunders (1963b) I c a l c u l a t e d t o t a l d a i l y t r a v e l d i s t a n c e t o s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e r a t i o s of 3.0 and 1.9 r e s p e c t i v e l y . I t h e r e f o r e m u l t i p l i e d my s t r a i g h t - l i n e d a i l y t r a v e l d i s t a n c e s by 2.5, the mean of t h e s e v a l u e s , t o e s t i m a t e t o t a l d a i l y t r a v e l d i s t a n c e . These are a l s o p l o t t e d i n F i g u r e 10. A l t h o u g h the c u r v e t h r o u g h the expected v a l u e s i s s i m i l a r t o my o b s e r v e d v a l u e s , the i n f l e c t i o n p o i n t i s not s h a r p enough t o mimic my d a t a a c c u r a t e l y . D a i l y t r a v e l d i s t a n c e s are t h e r e f o r e u n d e r - e s t i m a t e d a t v e r y h i g h and v e r y low hare abundances and o v e r - e s t i m a t e d a t i n t e r m e d i a t e d e n s i t i e s . E s t i m a t e s f o r the Y i n t e r c e p t and s l o p e parameters used i n the above e q u a t i o n a r e d e r i v e d from F i g u r e 2 of Brand e t a l . (1976). A l t h o u g h the c o r r e l a t i o n c o e f f i c i e n t f o r t h e i r r e g r e s s i o n l i n e i s good,(r 2=0.91) th e s e v a l u e s a r e b i o l o g i c a l l y u n r e a s o n a b l e . A Y i n t e r c e p t c o n s i d e r a b l y h i g h e r than z e r o s u g g e s t s t h a t l y n x a r e c o n t i n u i n g t o attempt t o k i l l h a r e s l o n g a f t e r t h e r e a r e no hares l e f t t o attempt t o k i l l . C l e a r l y t o be b i o l o g i c a l l y r e a s o n a b l e the r e g r e s s i o n l i n e must run t h r o u g h the o r i g i n or i n t e r s e c t the x - a x i s near the o r i g i n . Two p o s s i b l e l i n e s can be drawn t h r o u g h the o r i g i n t o i n t e r s e c t t h e i r d a t a ( F i g . 11); a s t r a i g h t l i n e r e g r e s s i o n or a c u r v e s i m i l a r t o a type I I f u n c t i o n a l response ( H o l l i n g 1959). Both r e s u l t i n a l a r g e r s l o p e f o r the r e g r e s s i o n l i n e a t low hare d e n s i t i e s . The type I I f u n c t i o n a l response c u r v e a l s o r e s u l t s i n a s m a l l e r s l o p e a t h i g h hare d e n s i t i e s . L i n e B of F i g u r e 10 shows p r e d i c t e d v a l u e s f o r the s t r a i g h t 62 F i g u r e 11. R e p r o d u c t i o n of F i g u r e 2, Brand and K e i t h (1979), w i t h 2 a d d i t i o n a l r e g r e s s i o n l i n e s added. L i n e A i s the o r i g i n a l r e g r e s s i o n l i n e p r e s e n t e d by Brand and K e i t h (1979). L i n e s B and C a r e a l t e r n a t i v e , more b i o l o g i c a l l y r e a s o n a b l e r e g r e s s i o n s p a s s i n g t h r o u g h the o r i g i n . See t e x t f o r e x p l a n a t i o n and j u s t i f i c a t i o n of l i n e B and C. 63 B 100 200 300 400 500 SNOWSHOE HARES/100 Ha of HABITAT (1 DECEMBER) 64 l i n e r e g r e s s i o n through the o r i g i n ( l i n e B F i g . 11) u s i n g the above e q u a t i o n w i t h a Y i n t e r c e p t of z e r o and a s l o p e of 0.13. The r e s u l t i n g r 2 v a l u e of 0.11 f o r t h i s l i n e i s f a r l e s s than t h a t of 0.91 r e p o r t e d by Brand e t a l . (1976) I t i s however, more b i o l o g i c a l l y r e a s o n a b l e . The i n f l e c t i o n p o i n t of the r e s u l t i n g l i n e ( l i n e B, F i g . 10), a l t h o u g h more c l o s e l y r e s e m b l i n g the observed d a t a , o c c u r s a t too h i g h a hare d e n s i t y . T h i s l i n e a l s o g r o s s l y o v e r -e s t i m a t e s t r a v e l d i s t a n c e a t low hare d e n s i t i e s and under-e s t i m a t e s i t a t h i g h hare d e n s i t i e s . I t h e r e f o r e p l o t t e d the da t a from F i g u r e 2 of Brand et a l . (1976) on l o g - l o g s c a l e , the e q u i v a l e n t of c a l c u l a t i n g a best f i t h y p e r b o l i c c u r v e through t h e i r d a t a t o the o r i g i n ( l i n e C, F i g . 1 1 ) . The r 2 v a l u e f o r t h i s l i n e i s 0.87, o n l y s l i g h t l y lower than 0.91 r e p o r t e d by Brand e t a l . (1976). F u r t h e r m o r e , t h i s l i n e i s a g a i n b i o l o g i c a l l y r e a s o n a b l e because i t goes through the o r i g i n . T h i s i s a l s o the g e n e r a l form of the type I I f u n c t i o n a l response ( H o l l i n g , 1959) t h a t i s common f o r many v e r t e b r a t e p r e d a t o r s (Krebs 1978). U s i n g the s l o p e and Y i n t e r c e p t from t h i s t r a n s f o r m a t i o n we a g a i n c a l c u l a t e d e x p e c t e d t r a v e l d i s t a n c e s w i t h the above e q u a t i o n . These a r e p l o t t e d as l i n e C on f i g u r e 10. A l t h o u g h t h i s l i n e s l i g h t l y o v e r - e s t i m a t e s d a i l y t r a v e l d i s t a n c e a t low d e n s i t i e s and u n d e r - e s t i m a t e s t r a v e l d i s t a n c e s a t e x t r e m e l y h i g h hare d e n s i t e s , the i n f l e c t i o n p o i n t i s the c o r r e c t form and o c c u r s a t t h e r i g h t p o i n t t o mimic my observed d a t a so t h a t the f i t of t h i s l i n e i s s u r p r i s i n g l y good. The 65 s l i g h t o v e r - e s t i m a t i o n of t r a v e l d i s t a n c e a t low hare d e n s i t i e s may be due t o p h y s i o l o g i c a l c o n s t r a i n t s on the l y n x . Lynx may not be a b l e t o t r a v e l f a r enough per day a t low hare d e n s i t i e s t o meet t h e i r e n e r g e t i c r e q u i r e m e n t s . T h i s , i n t u r n , would r e s u l t i n the d e c l i n e i n g e n e r a l body c o n d i t i o n of l y n x a t low hare d e n s i t i e s . The u n d e r - e s t i m a t i o n of t r a v e l d i s t a n c e at e x t r e m e l y h i g h hare d e n s i t i e s may be due t o l y n x c o n t i n u i n g t o t r a v e l and sample the environment a f t e r t h e i r e n e r g e t i c r e q u i r e m e n t s have been met. P a r k e r e t a l . (1983) found e v i d e n c e t h a t l y n x o f t e n c o n t i n u e t o t r a v e l a f t e r consuming the f i r s t k i l l of the day. T h i s model a l s o demonstrates t h a t my data and t h o s e of Brand et a l . (1976) are i n s t r o n g a c c o r d . A l t h o u g h the e x p l a n a t i o n s of Brand et a l . (1976) and P a r k e r e t a l . (1983) may be s u f f i c i e n t t o e x p l a i n why t h e r e i s no a p p arent i n c r e a s e i n l y n x f o r a g i n g e f f o r t a t hare d e n s i t i e s above 1.0 h a r e s / h a , they cannot be e x t r a p o l a t e d t o lower d e n s i t i e s . Lynx f o r a g i n g e f f o r t i n c r e a s e s d r a m a t i c a l l y a t hare d e n s i t i e s below 1.0 hare/ha but the i n c r e a s e i s not s u f f i c i e n t f o r l y n x t o c o n t i n u e t o f u l f i l l t h e i r e n e r g e t i c r e q u i r e m e n t s . 66 E f f e c t of Snowshoe Hare D i s t r i b u t i o n on Lynx F o r a g i n g P a t t e r n s I f p r e y a r e not u n i f o r m l y d i s t r i b u t e d throughout the environment i t w i l l always be t o the advantage of a p r e d a t o r t o c o n c e n t r a t e i t s f o r a g i n g e f f o r t s i n the p a t c h e s of r e l a t i v e l y h i g h p r e y abundance (Krebs 1978). T h i s w i l l become i n c r e a s i n g l y i m p o r t a n t as the r e l a t i v e d i f f e r e n c e between the good p a t c h e s and the s u r r o u n d i n g a r e a s i n c r e a s e s and i t becomes d i f f i c u l t f o r the p r e d a t o r t o f u l f i l l i t s e n e r g e t i c r e q u i r e m e n t s o u t s i d e the good p a t c h e s . I do not have good d a t a on the p a t c h i n e s s of snowshoe hare d i s t r i b u t i o n but i f the system i s s i m i l i a r t o t h a t d e s c r i b e d by W o l f f (1980) snowshoe hare d i s t r i b u t i o n s h o u l d have been v e r y clumped. W o l f f (1980) suggested t h a t d u r i n g the d e c l i n e and low p e r i o d of t h e i r t en year c y c l e , snowshoe hare p o p u l a t i o n s r e t r e a t i n t o p a t c h e s of o p t i m a l h a b i t a t . I t would seem r e a s o n a b l e then t h a t i t would be a d a p t i v e f o r l y n x t o seek out and u t i l i z e t h e s e good p a t c h e s . In t h i s s t u d y I found t h r e e independent l i n e s of e v i d e n c e i n d i c a t i n g t h a t l y n x do seek out and c o n c e n t r a t e t h e i r f o r a g i n g e f f o r t s i n p a t c h e s of h i g h snowshoe hare abundance. F i r s t , my l y n x t r a p p i n g s u c c e s s was h i g h e r i n an a r e a of r e l a t i v e l y h i g h hare abundance. Second, t r a c k t r a n s e c t s t h r o u g h a r e a s of d i f f e r e n t hare abundance a l s o i n d i c a t e d t h a t l y n x used a r e a s of h i g h hare abundance more i n t e n s i v e l y than s u r r o u n d i n g a r e a s . T h i r d , l y n x ' d e n s i t y was h i g h e r w i t h i n the p a t c h of r e l a t i v e l y h i g h prey abundance than elsewhere i n the s t u d y . F u r t h e r , I found t h a t l y n x abandoned t h e s e good p a t c h e s when they became 67 d e p l e t e d . O t h e r s have a l s o found t h a t l y n x tend t o c o n c e n t r a t e i n pa t c h e s of r e l a t i v e l y h i g h prey abundance. Brand e t a l . (1976) s t a t e t h a t one of the t h r e e h u n t i n g methods used by l y n x was t o c o n c e n t r a t e t h e i r e f f o r t s i n a r e a s of hare a c t i v i t y , e s p e c i a l l y d u r i n g c y c l i c lows i n hare abundance. He d i d not q u a n t i f y t h i s . Saunders (1963a) r e p o r t e d t h a t l y n x c o n c e n t r a t e d i n an a r e a of abundant c a r r i o n d u r i n g a p e r i o d of low hare numbers and then d i s p e r s e d a f t e r the c a r r i o n became u n a v a i l a b l e . B e r r i e (1974), K o e h l e r e t a l . (1979) and Bergerud (1971) a l s o note t h a t l y n x tend t o c o n c e n t r a t e i n a r e a s of r e l a t i v e l y h i g h food abundance. B e r r i e (1974) f u r t h e r s u g g ested t h a t r e f u g i a f o r snowshoe hare were i m p o r t a n t f o r the s u r v i v a l of l y n x t h r o u g h the low of the c y c l e and t h a t the e x p a n s i o n of the l y n x p o p u l a t i o n out of these r e f u g i a f o l l o w e d t h a t of the snowshoe hare p o p u l a t i o n d u r i n g the i n c r e a s e phase. That l y n x cannot meet t h e i r e n e r g e t i c needs a t hare d e n s i t i e s below 0.5 h a r e s / h a , as p r e v i o u s l y s u g g e s t e d , s u p p o r t s t h i s * i d e a . As d i s c u s s e d above, a b s o l u t e hare d e n s i t y has l i t t l e e f f e c t on the degree of a g g r e g a t i o n of l y n x , but r e l a t i v e p rey abundance ( p a t c h i n e s s of d i s t r i b u t i o n ) may p l a y a l a r g e r o l e i n d e t e r m i n i n g the s p a t i a l d i s t r i b u t i o n of l y n x . The h i g h degree of home range o v e r l a p found between the 4 l y n x d u r i n g A p r i l - J u n e 1982 was a f u n c t i o n of t h e i r s h a r i n g a p a t c h of r e l a t i v e l y h i g h p rey abundance. A l t h o u g h I do not have d a t a on prey d i s t r i b u t i o n i n the a r e a of l y n x home range o v e r l a p a t low hare d e n s i t y , i t i s p o s s i b l e t h a t t h i s a r e a a l s o had r e l a t i v e l y h i g h 6B prey abundance. Lynx home range o v e r l a p may then be a f u n c t i o n of r e l a t i v e prey abundance. Lynx home ranges may o v e r l a p e x t e n s i v e l y i n ar e a s of r e l a t i v e l y h i g h prey d e n s i t y and not o v e r l a p i n ar e a s of r e l a t i v e l y low prey d e n s i t y . T h i s might a l s o e x p l a i n the l a r g e v a r i a t i o n i n degree of home range o v e r l a p between l y n x at i n t e r m e d i a t e hare d e n s i t i e s i n t h i s s t u d y . Lynx d e n s i t y was a l s o h i g h e r i n the two. a r e a s of h i g h home range o v e r l a p than elsewhere i n the st u d y . Lynx P i s p e r s a l and M o r t a l i t y P u r i n g the p e r i o d of r a p i d d e c l i n e i n snowshoe hare numbers (January t h r o u g h Pecember 1982) 3 of the 7 l y n x t h a t I had r a d i o - t a g g e d d i s p e r s e d between 250 and 700 km b e f o r e b e i n g t r a p p e d by p r o f e s s i o n a l t r a p p e r s . Other l o n g d i s t a n c e d i s p e r s a l s by l y n x of from 103 t o a p p r o x i m a t e l y 800 km have been r e p o r t e d elsewhwhere by o t h e r r e s e a r c h e r s (Saunders 1963b, N e l l i s and Wetmore 1969 , Mech 1977, P. B r i t t e l p e r s . comm.). These d i s p e r s a l s a r e n o r m a l l y a s s o c i a t e d w i t h the d e c l i n e phase of the snowshoe hare c y c l e and l y n x have been r e p o r t e d t o invade a r e a s w e l l south of t h e i r normal range ( Adams 1963, Mech 1973, Gunderson 1978). T h i s and o t h e r s t u d i e s have shown t h a t a d u l t s as w e l l as j u v e n i l e s undertake such l o n g movements. The t h r e e d i s p e r s e r s i n my study had minimum d a i l y s t r a i g h t l i n e t r a v e l d i s t a n c e s s i m i l a r t o or l a r g e r than those r e c o r d e d f o r r e s i d e n t l y n x d u r i n g the same p e r i o d . T h i s s u g g e s t s t h a t once these a n i m a l s abandoned t h e i r home ranges they d i d not 69 r e s e t t l e i n o t h e r a r e a s . I t i s i n t e r e s t i n g t o note t h a t a l l the l o n g d i s t a n c e movements r e c o r d e d i n t h i s s t u d y o c c u r r e d d u r i n g the r a p i d d e c l i n e i n snowshoe hare numbers. A f t e r hare d e n s i t i e s had s t a b l i z e d a t a low l e v e l , (below about 1.0 hares/ha.) l y n x expanded t h e i r home range d r a m a t i c a l l y , or became nomadic but remained w i t h i n the g e n e r a l study a r e a . Whether t h i s r e p r e s e n t s a change i n the response of l y n x t o d i f f e r e n t e n v i r o n m e n t a l c o n d i t i o n s , or i s merely a chance o c c u r r e n c e due t o s m a l l sample s i z e i s not c l e a r . I t might be t h a t the l o n g d i s t a n c e movements e x h i b i t e d by th e s e l y n x were a response t o r a p i d l y changing and u n f a m i l a r c o n d i t i o n s . These l y n x may have been s e e k i n g c o n d i t i o n s s i m i l a r t o t h o s e t h e y had e x p e r i e n c e d i n the p a s t . Once prey abundance became s t a b l e a g a i n a t a lower l e v e l and the l y n x a c c l i m a t e d t o t h i s new l e v e l of r e s o u r c e abundance they may have been l e s s i n c l i n e d towards such d r a m a t i c movements. Man was the s i n g l e most i m p o r t a n t m o r t a l i t y f a c t o r f o r l y n x i n t h i s s t u d y . P r o f e s s i o n a l t r a p p i n g was r e s p o n s i b l e f o r 7 of 8 of o b s e r v e d d e a t h s . Only 2 of 9 r a d i o - t a g g e d i n d i v i d u a l s t h a t were known t o t r a v e l o u t s i d e Kluane Game Sa n c t u a r y were not t r a p p e d ; most were t r a p p e d w i t h i n 2.5 months of the b e g i n n i n g of t r a p p i n g season. One of the 2 a n i m a l s t h a t were not t r a p p e d (Rene) d i e d of n a t u r a l c auses and presumably s t a r v e d . Other s t u d i e s have a l s o r e p o r t e d h i g h human-related m o r t a l i t y r a t e s i n l y n x p o p u l a t i o n s . P a r k e r e t a l . (1983) found 65% of a l o c a l l y n x p o p u l a t i o n was t r a p p e d i n the f i r s t 70 open season a f t e r a one year c l o s u r e . Mech (1980) r e p o r t e d t h a t 3 of 5 l y n x r a d i o - t a g g e d i n 1972 were k i l l e d by humans w i t h i n f i v e months and a f o u r t h was k i l l e d w i t h i n a y e a r . In t o t a l , 7 of h i s 14 l y n x were k i l l e d by humans. Carbyn and P a t r i q u i n (1983) r e p o r t t h a t a l l t h r e e l y n x they r a d i o - t a g g e d i n R i d i n g Mountain N a t i o n a l Park were t r a p p e d and k i l l e d o u t s i d e the park. Two were t r a p p e d w i t h i n 4 months of r a d i o - t a g g i n g and one was t r a p p e d two y e a r s and t h r e e months l a t e r . N e l l i s e t a l . (1972) r e p o r t e d 3 of 9 a d u l t l y n x tagged between August 1964 and F e b r u a r y 1965 were t r a p p e d w i t h i n one year of t a g g i n g . The f a t e of the r e m a i n i n g 6 i s unknown. Of e i g h t l y n x tagged between August 1965 and F e b r u a r y 1968, 1 was dead w i t h i n 1 y e ar and 3 were r e c a p t u r e d a f t e r a t l e a s t 1 y e a r . K o e h l e r e t a l . (1979) b e l i e v e d t h a t one of two l y n x he had r a d i o - t a g g e d was p r e d a t e d by a mountain l i o n . The f a t e of h i s second a n i m a l i s a p p a r e n t l y unknown. Brand and K e i t h (1979) e s t i m a t e d a n n u a l t r a p p i n g m o r t a l i t y r a t e s of 10% d u r i n g the e a r l y i n c r e a s e phase of the hare c y c l e and 17-29% d u r i n g the e a r l y d e c l i n e phase. Non-t r a p p i n g m o r t a l i t y r a t e s f o r a d u l t s were e s t i m a t e d a t 7 t o 38% d u r i n g e a r l y d e c l i n e phase. T h e i r e s t i m a t e s c o n t a i n s e v e r a l a s s u m p t i o n s t h a t makes them s u s p e c t , i n c l u d i n g an assumption t h a t a l l n o n - t r a p p i n g m o r t a l i t y o c c u r s b e f o r e the s t a r t of t r a p p i n g season ( i . e . from May t o November). I t would be s u r p r i s i n g i f n a t u r a l m o r t a l i t y were h i g h e s t d u r i n g the most benign time of y e a r . F u r t h e r , h i s e s t i m a t e s of t r a p p i n g m o r t a l i t y a r e low and h i s n o n - t r a p p i n g m o r t a l i t y r a t e s a r e h i g h compared t o d a t a from the above t a g g i n g s t u d i e s . Combining the 71 r e s u l t s of t h i s study w i t h those p r e v i o u s s t u d i e s ( e x c l u d i n g the e s t i m a t e s of Brand and K e i t h 1979), man i s the s i n g l e most im p o r t a n t m o r t a l i t y f a c t o r i n l y n x p o p u l a t i o n s . The deaths of 55% of a l l l y n x tagged i n the s e s t u d i e s were human-related. Of those a n i m a l s f o r which the cause of dea t h i s known, man i s r e s p o n s i b l e ' f o r 95% of the m o r t a l i t y . In c o n t r a s t , n a t u r a l m o r t a l i t y i n t h i s and the above s t u d i e s was r e s p o n s i b l e f o r an annual l o s s of o n l y 5.6% of tagged l y n x . The b e h a v i o r a l r e s p o n s e s of l y n x t o d e c l i n i n g snowshoe hare abundance s h o u l d i n c r e a s e l y n x v u l n e r a b i l i t y t o t r a p p i n g . A c o m b i n a t i o n of i n c r e a s e d home range s i z e and d a i l y t r a v e l d i s t a n c e s w i t h d e c l i n i n g p r e y abundance s h o u l d b r i n g the l y n x i n t o c o n t a c t w i t h more t r a p s . When prey a r e s c a r c e , l y n x might be more e a s i l y a t t r a c t e d t o t r a p b a i t s , t h u s i n c r e a s i n g t r a p p i n g s u c c e s s . F i n a l l y , because l y n x aggregate i n a r e a s of r e l a t i v e l y h i g h snowshoe hare abundance, i t would be p o s s i b l e f o r a t r a p p e r t o t r a p a r e l a t i v e l y l a r g e p r o p o r t i o n of the l y n x p o p u l a t i o n i n an a r e a by c o n c e n t r a t i n g h i s e f f o r t s i n a r e a s of r e l a t i v e l y h i g h hare abundance. I f t h e s e f a c t o r s a r e i m p o r t a n t , they s h o u l d have most e f f e c t when r e c r u i t m e n t i n t o the l y n x p o p u l a t i o n i s l o w e s t . T h i s may r e s u l t i n l y n x p o p u l a t i o n s b e i n g e s p e c i a l l y s e n s i t i v e t o o v e r - h a r v e s t i n g d u r i n g the d e c l i n e and low i n snowshoe hare abundance. 72 Lynx S o c i a l S t r u c t u r e The s o c i a l s t r u c t u r e of any mammalian s p e c i e s i s a f u n c t i o n of the environment i n which i t l i v e s ( F i s l e r 1969). In t h i s s e c t i o n , I w i l l d i s c u s s the s o c i a l o r g a n i z a t i o n observed i n l y n x p o p u l a t i o n s and the e n v i r o n m e n t a l f a c t o r s t h a t have s e l e c t e d f o r i t . Lynx, l i k e most f e l i d s are s o l i t a r y a n i m a l s . A l t h o u g h l y n x were o c c a s i o n a l l y near each o t h e r i n t h i s s t u d y , the o n l y s i g n s of extended s o c i a l i t y i n v o l v e d females and t h e i r young of the y e a r . The degree of s o c i a l i t y o bserved i n p o p u l a t i o n s of c a r n i v o r e s i s g e n e r a l l y c o n s i d e r e d t o be a f u n c t i o n of p r e f e r r e d p r e y s i z e and h u n t i n g s t r a t e g y . B o u l i e r e (1963) noted t h a t s o l i t a r y c a r n i v o r e s t y p i c a l l y p rey on a n i m a l s s m a l l e r than t h e m s e l v e s w h i l e s o c i a l c a r n i v o r e s o f t e n s e l e c t l a r g e r p r e y . Kruuk (1972, 1975) d e v e l o p e d t h i s o b s e r v a t i o n t o suggest t h a t s o c i a l i t y i n c a r n i v o r e s i s an a d a p t a t i o n f o r c a p t u r i n g r e l a t i v e l y l a r g e p r e y , and t h i s has been used t o e x p l a i n s o c i a l i t y i n l i o n s ( S c h a l l e r 1972, Kruuk 1972, B e r t r a m 1978,1979, G i t t l e m a n 1983, Macdonald 1983). Kruuk's t e s t of t h i s h y p o t h e s i s f o r f e l i d s , however, was i n c o n c l u s i v e . P acker ( i n p r e s s ) s u g g e s t s i n s t e a d t h a t s o c i a l i t y i n l i o n s r e s u l t s from a c o m b i n a t i o n of t h r e e f a c t o r s : 1) p r e f e r e n c e f o r l a r g e p r e y , 2) the openess of the h a b i t a t i n which they l i v e and 3) the h i g h p o p u l a t i o n d e n s i t i e s which they a t t a i n . Lynx i n h a b i t dense b o r e a l f o r e s t s and consume p r i m a r i l y snowshoe hares which weigh o n l y 10-15% of the a d u l t body weight 73 of a l y n x . The r e l a t i v e l y s m a l l s i z e of l y n x prey and l i f e i n dense b o r e a l f o r e s t would t h e r e f o r e not f a v o r s o c i a l i t y i n l y n x . F u r t h e r , Kleiman and E i s e n b e r g (1973) suggest t h a t h u n t i n g by s t e a l t h , the p r i m a r y h u n t i n g s t r a t e g y of l y n x , demands a s o l i t a r y l i f e s t y l e . In a r e a s of h i g h prey abundance, however, l y n x can r e a c h p o p u l a t i o n d e n s i t i e s e q u a l t o those of l i o n s . I t i s i n t e r e s t i n g t o n o t e , however, t h a t h u n t i n g success, f o r l y n x i n c r e a s e s w i t h group s i z e . P a r k e r et a l . (1983) found t h a t h u n t i n g s u c c e s s r a t e s ( p e r c e n t of chases t h a t a r e s u c c e s s f u l ) f o r f a m i l y u n i t s of one, two, t h r e e and fo u r were 14, 17, 38 and 58 p e r c e n t r e s p e c t i v e l y . There may t h e r e f o r e be l i t t l e d i s a d v a n t a g e t o group l i v i n g i n l y n x d u r i n g p e r i o d s of h i g h snowshoe hare abundance. F u r t h e r , group l i v i n g might b e n e f i t l y n x when snowshoe abundance i s . low by e n a b l i n g them t o c a p t u r e l a r g e r p r e y i t e m s , such as c a r i b o u , D a l l sheep and perhaps moose c a l v e s . Why l y n x a r e not s o c i a l may be r e l a t e d t o P a c k e r ' s second p o i n t . Lynx l i v e i n dense co v e r w h i l e l i o n s a r e t y p i c a l l y open c o u n t r y a n i m a l s and i t may not be p o s s i b l e t o c o o r d i n a t e group hunts f o r l a r g e p r e y i n dense c o v e r where v i s i b i l i t y i s low. Wolves hunt c o o p e r a t i v e l y i n c l o s e d f o r e s t h a b i t a t but use v o c a l i z a t i o n s t o c o o r d i n a t e t h e i r e f f o r t s ( P e t e r s o n 1977). Lynx do not v o c a l i z e . Based on t h e h i g h degree of home range o v e r l a p , l y n x i n t h i s study were not t e r r i t o r i a l . As d i s c u s s e d by D a v i e s (1978), i f a l i m i t i n g r e s o u r c e i s s t a b l e and p r e d i c t a b l e i n time and space then i t i s t o the advantage of the p r e d a t o r t o t o defend e x c l u s i v e use a r e a s ( t e r r i t o r i e s ) . I f the r e s o u r c e i s not 74 s t a b l e and p r e d i c t a b l e i n time and space, however, t h e r e i s no b e n e f i t t o d e f e n d i n g a t e r r i t o r y i n which the r e s o u r c e i s l i k e l y t o d i s a p p e a r . T e r r i t o r i a l i t y w i t h i n s e x e s , have been d e s c r i b e d f o r s e v e r a l f e l i d s p e c i e s . Female t i g e r s ( S u n g u i s t 1981), b o b c a t s ( B a i l e y 1974), l e o p a r d s (Bertrum 1982), and European w i l d c a t s ( C o r b e t t 1979: c i t e d i n Packer i n p r e s s ) have been r e p o r t e d t o have e x c l u s i v e home ranges. Food i s g e n e r a l l y c o n s i d e r e d t o be the defended r e s o u r c e i n these systems. C o a l i t i o n s of male cheetahs (Frame 1980) and l i o n s ( S c h a l l e r 1972) are a l s o been r e p o r t e d t o defend t e r r i t o r i e s a g a i n s t o t h e r c o a l i t i o n s of males. Females are g e n e r a l l y c o n s i d e r e d t o be the r e s o u r c e b e i n g defended by these male c o a l i t i o n s . Home range o v e r l a p between sexes i s common i n f e l i d s . Male-female home range o v e r l a p has been r e p o r t e d f o r t i g e r s ( S u n g u i s t 1981), j a g u a r s ( S c h a l l e r and Crawshaw 1980), cougars ( S e i d e n s t i c k e r et a l . 1973) , European w i l d c a t s ( C o r b e t t 1979), and bob c a t s ( B a i l e y 1974) . Snowshoe hare numbers, the l i m i t i n g r e s o u r c e f o r l y n x p o p u l a t i o n s , a r e u n s t a b l e i n both time and space and a r e l i k e l y u n p r e d i c t a b l e t o the l y n x . Areas which may have h i g h hare d e n s i t i e s a t the c y c l i c peak may be v i r t u a l l y empty w i t h i n months of the s t a r t of the d e c l i n e . Under t h e s e c o n d i t i o n s i t would be m a l a d a p t i v e f o r a l y n x t o expend energy m a i n t a i n i n g a t e r r i t o r y . In summary, snowshoe hare abundance and d i s t r i b u t i o n seem to be the p r o x i m a t e s t r u c t u r i n g f o r c e s c o n t r o l l i n g l y n x 75 abundance and d i s t r i b u t i o n . A b s o l u t e abundance of l y n x i s a f u n c t i o n of snowshoe hare abundance. C y c l e s i n l y n x abundance l a g b e h i n d those of hare s by one t o two y e a r s ( E l t o n and N i c h o l s o n 1942, Brand e t a l . 1976, P a r k e r e t a l . 1983 ). Lynx d i s t r i b u t i o n i n space i s dependent on snowshoe hare d i s t r i b u t i o n . Lynx c o n c e n t r a t e i n a r e a s of r e l a t i v e l y h i g h hare abundance (Saunders 1963a, Bergerud 1971, B e r r i e 1974, K o e h l e r et a l . 1979 and t h i s s t u d y ) and d i s p e r s e a f t e r these a r e a s of r e l a t i v e abundance have been d e p l e t e d ( t h i s s t u d y ) . 76 MANAGEMENT IMPLICATIONS I n t r o d u c t i o n E f f e c t i v e management of w i l d l i f e p o p u l a t i o n s e x h i b i t i n g marked f l u c t u a t i o n s i n r e c r u i t m e n t r a t e s r e q u i r e management p l a n s t h a t v a r y h a r v e s t r a t e d i r e c t l y w i t h changes i n r e c r u i t m e n t r a t e . F a i l u r e t o reduce the h a r v e s t r a t e d u r i n g p e r i o d s of low r e c r u i t m e n t can i n h i b i t the p o p u l a t i o n s a b i l i t y t o i n c r e a s e when c o n d i t i o n s a g a i n become f a v o u r a b l e (Caughley 1977). R e c r u i t m e n t of l y n x i n t o the p o p u l a t i o n f l u c t u a t e s from near z e r o d u r i n g p e r i o d s of low snowshoe hare abundance t o 3 t o 4 young per female per year d u r i n g p e r i o d s of h i g h hare abundance. Management s t r a t e g i e s c u r r e n t l y b e i n g used f o r l y n x , however, do not take i n t o account f l u c t u a t i o n s i n r e c r u i t m e n t r a t e . Lynx p o p u l a t i o n s a r e t h e r e f o r e e s p e c i a l l y s u s c e p t i b l e t o o v e r - h a r v e s t i n g . In a d d i t i o n , e v i d e n c e from t h i s and pas t t a g g i n g s t u d i e s , s u g g e s t s t h a t man i s r e s p o n s i b l e f o r an annual l o s s of over 55% of l y n x p o p u l a t i o n s . Other f a c t o r s cause the l o s s of 5.6% of l y n x p o p u l a t i o n s each y e a r . D u r i n g p e r i o d s of d e c l i n e and s c a r c i t y i n snowshoe hare abundance both t r a p p i n g and n a t u r a l m o r t a l i t y r a t e s can be ex p e c t e d t o be h i g h e r than t h e s e f i g u r e s . D u r i n g 2 y e a r s of d e c l i n i n g hare abundance, I found annual m o r t a l i t y r a t e s of 100 and 75 p e r c e n t of my tagged l y n x which were known t o l e a v e Kluane Game S a n c t u a r y . I t h e r e f o r e produced 2 s i m u l a t i o n models t o a s s e s s the e f f e c t of the observ e d h a r v e s t r a t e s on l y n x p o p u l a t i o n dynamics 77 t h r o u g h t h e i r t e n year c y c l e . The Models I d e v e l o p e d the m o d e l s , u s i n g p o p u l a t i o n parameters ( T a b l e 6) from my work and t h a t of Brand and K e i t h (1979). In both models I s u b d i v i d e d the snowshoe hare c y c l e i n t o 3 y e a r s of h i g h hare abundance, 2 y e a r s of i n t e r m e d i a t e hare abundance d u r i n g i n c r e a s e and d e c l i n e phases and 3 y e a r s of low hare abundance a t the bottom of the c y c l e . I assumed a 1:1 sex r a t i o i n the l y n x p o p u l a t i o n . I s e t the i n i t i a l s p r i n g l y n x age d i s t r i b u t i o n a t 7% y e a r l i n g s and 93% a d u l t s , s i m i l a r t o the age d i s t r i b u t i o n found by Brand and K e i t h (1979) a f t e r 3 y e a r s of low hare abundance and j u s t p r i o r t o the s t a r t of the i n c r e s e phase of the hare c y c l e . E s t i m a t e s of in u t e r o l i t t e r s i z e and pregnancy r a t e s f o r y e a r l i n g and a d u l t females a t low, i n t e r m e d i a t e and h i g h hare abundance were taken from T a b l e 5 of Brand and K e i t h (1979). I a l l o w e d k i t t e n s 100% s u r v i v a l from b i r t h t o the s t a r t of the t r a p p i n g season (May t o November) d u r i n g p e r i o d s of h i g h hare abundance. E s t i m a t e s of k i t t e n s u r v i v a l d u r i n g p e r i o d s of i n t e r m e d i a t e and low hare abundance were taken from Brand and K e i t h (1979) and s e t a t 35 and 8 % r e s p e c t i v e l y . In model A (see appendix 1a f o r d e t a i l s of the model), an n u a l k i t t e n p r o d u c t i o n by y e a r l i n g and a d u l t females was c a l c u l a t e d by the e q u a t i o n : NK = (NY * .5 * RY) + (NA * .5 * RA) 78 T a b l e 6. Parameter e s t i m a t e s used i n l y n x p o p u l a t i o n s i m u l a t i o n models. A d u l t and y e a r l i n g m o r t a l i t y r a t e s a r e per y e a r . K i t t e n summer m o r t a l i t y r a t e s a re b i r t h t o November. P o s t November k i t t e n m o r t a l i t y r a t e s were assumed e q u a l t o a d u l t m o r t a l i t y r a t e s . Lynx pregnancy r a t e s , l i t t e r s i z e s , k i t t e n m o r t a l i t y r a t e s and a d u l t m o r t a l i t y r a t e s f o r model B a r e from Brand and K e i t h (1979). I assume l y n x have a maximum of 1 l i t t e r per y e a r . See t e x t f o r d e r i v a t i o n of a d u l t m o r t a l t y r a t e s f o r model A. PARAMETER SNOWSHOE HARE ABUNDANCE LOW INTERMEDIATE HIGH A d u l t l y n x pregnancy r a t e 0.33 0.46 0.7 3 Y e a r l i n g l y n x pregnancy r a t e 0.0 0.0 0.4 A d u l t l y n x i n u t e r o l i t t e r s i z e 3.4 3.9 4.6 Y e a r l i n g l y n x i n u t e r o l i t t e r s i z e 3.9 Lynx k i t t e n summer m o r t a l i t y r a t e 0.92 0.65 0.0 T r a p p i n g m o r t a l i t y r a t e (model A) 0.55 0.55 0.55 N a t u r a l m o r t a l i t y r a t e (model A) 0.06 0.06 0.06 T r a p p i n g m o r t a l i t y r a t e (model B) 0.14 0.14 0.14 N a t u r a l m o r t a l i t y r a t e (model B) 0.35 0.35 0.35 80 where * = m u l t i p l i e d by NK = number of k i t t e n s i n the f a l l ; NY = number of y e a r l i n g s i n the s p r i n g p o p u l a t i o n ; RY = pregnancy r a t e * i_n u t e r o l i t t e r s i z e f o r y e a r l i n g females * summer s u r v i v a l r a t e f o r k i t t e n s ; NA = number of a d u l t s i n the s p r i n g p o p u l a t i o n ; RA = pregnancy r a t e * i_n u t e r o l i t t e r s i z e f o r a d u l t females * summer s u r v i v a l r a t e f o r k i t t e n s I assumed t h a t November t o May m o r t a l i t y r a t e s were eq u a l f o r a l l age c l a s s e s and t h a t a l l y e a r l i n g and a d u l t m o r t a l i t y o c c u r r e d i n t h i s p e r i o d . I assumed no d e n s i t y dependence i n m o r t a l i t y r a t e s . I s e t an n u a l t r a p p i n g and n o n - t r a p p i n g m o r t a l i t y r a t e s at 55% and 6% r e s p e c t i v e l y (see p r e v i o u s s e c t i o n on l y n x m o r t a l i t y f o r d e r i v a t i o n of the s e v a l u e s ) . Post t r a p p i n g season (May) a d u l t l y n x p o p u l a t i o n numbers were c a l c u l a t e d by the e q u a t i o n : NAS = (NAF + NYF) * S where * = m u l t i p l i e d by NAS = number of a d u l t s i n May NAF = number of a d u l t s i n November NYF = number of y e a r l i n g s i n November S = s u r v i v a l r a t e November t o May 81 May y e a r l i n g p o p u l a t i o n numbers was c a l c u l a t e d by the e q u a t i o n : NYS = NKF * S where NYS = number of y e a r l i n g s i n s p r i n g ; NKF = number of k i t t e n s i n f a l l ; Brand and K e i t h (1979) a l s o m o d e l l e d the dynamics of a l y n x p o p u l a t i o n t h rough a d e c l i n e t o the f o l l o w i n g peak. Model A c o n t a i n e d s e v e r a l q u a l i t a t i v e and q u a n t i t a t i v e d i f f e r e n c e s from t h e i r model. To determine i f t h e s e d i f f e r e n c e s would have an e f f e c t on the dynamics of the m o d e l l e d p o p u l a t i o n , I m o d i f i e d model A t o r e f l e c t the a s sumptions and parameter e s t i m a t e s of Brand and K e i t h ( 1 9 7 9 ) ( T a b l e 6 ) ( s e e appendix 1b f o r d e t a i l s of model B ) . C a l c u l a t i o n of k i t t e n r e c r u i t m e n t i n t o the l y n x p o p u l a t i o n was the same i n models A and B. As i n model A, Brand and K e i t h (1979) assumed t h a t t r a p p i n g and n o n - t r a p p i n g m o r t a l i t y were a d d i t i v e and t h a t t r a p p i n g m o r t a l i t y was s i m i l a r i n a l l age c l a s s e s . Brand and K e i t h (1979), however, assumed t h a t a l l non-t r a p p i n g m o r t a l i t y o c c u r r e d from May t o November. Brand and K e i t h (1979) e s t i m a t e d ' t o t a l a n n u a l m o r t a l i t y a t 44%, s i m i l a r t o the v a l u e used i n my f i r s t model. They e s t i m a t e d annual n a t u r a l m o r t a l i t y l o s s e s a t 35% of the s p r i n g l y n x p o p u l a t i o n and 8 2 t r a p p i n g m o r t a l i t y a t 14% of the f a l l p o p u l a t i o n . Model B t h e r e f o r e c a l c u l a t e s independent e s t i m a t e s f o r s p r i n g and f a l l y e a r l i n g and a d u l t numbers u s i n g t h e i r e s t i m a t e s of t r a p p i n g and n o n - t r a p p i n g m o r t a l i t y r a t e s . R e s u l t s and P i s c u s s i o n I ran both models through 5 complete c y c l e s (50 y e a r s ) s t a r t i n g w i t h 2 y e a r s of i n c r e a s e phase hare abundance. The l y n x p o p u l a t i o n i n model A was v i r t u a l l y e x t i n c t a t the end of one f u l l c y c l e of 10 y e a r s ( F i g . 12). Even d u r i n g p e r i o d s of h i g h hare abundance m o r t a l i t y exceeded r e c r u i t m e n t i n t o the l y n x p o p u l a t i o n . In f a c t the l y n x p o p u l a t i o n d e c l i n e d t o v i r t u a l e x t i n c t i o n when t o t a l a nnual m o r t a l i t y r a t e s ( t r a p p i n g + n a t u r a l ) were 0.30 or l a r g e r ( F i g . 13). A l l p a s t t a g g i n g s t u d i e s f o r which I c o u l d d etermine a n n u a l m o r t a l i t y r a t e s ( t h i s s t u d y , P a r k e r e t a l . 1983, Mech 1980, Carbyn and P a t r i q u i n 1983, N e l l i s e t a l . 1972, K o e h l e r et a l . 1979) have r e p o r t e d r a t e s i n ex c e s s of 0.30. The l y n x p o p u l a t i o n i n model B a l s o d e c l i n e d t o v i r t u a l e x t i n c t i o n , a l t h o u g h a t a slow e r r a t e than i n model A ( F i g 14). I t i s i n t e r e s t i n g t o note t h a t i n Brand and K e i t h (1979)'S s i m u l a t i o n from the s t a r t of the c y c l i c d e c l i n e i n l y n x abundance t o the f o l l o w i n g peak i n abundance, 8 y e a r s l a t e r , the m o d e l l e d l y n x p o p u l a t i o n showed a d e c l i n e i n numbers of a p p r o x i m a t e l y 0.4%. T h i s s u g g e s t s t h a t , a l l o w e d t o run through a number of c y c l e s t h e i r p o p u l a t i o n may a l s o have c o n t i n u e d t o d e c l i n e . 83 F i g u r e 12. Dynamics of s i m u l a t e d l y n x p o p u l a t i o n u s i n g model A and observed m o r t a l i t y r a t e s . See T a b l e 6 and Appendix 1a f o r parameter e s t i m a t e s and s i m u l a t i o n model program. 84 azis NOiivnndOd 85 F i g u r e 13. Dynamics of s i m u l a t e d l y n x p o p u l a t i o n u s i n g model A w i t h t o t a l a nnual m o r t a l i t y r a t e s e t at 0.30. See T a b l e 6 and Appendix 1a f o r parameter e s t i m a t e s and s i m u l a t i o n model program. o i n o o CO CO < LU > o CM 87 F i g u r e 14. Dynamics of s i m u l a t e d l y n x p o p u l a t i o n u s i n g model B and m o r t a l i t y r a t e e s t i m a t e s from Brand and K e i t h (1979). See T a b l e 6 and Appendix 1b f o r parameter e s t i m a t e s and s i m u l a t i o n model program. 88 CO cc < UJ >-3Zis NOiivnndOd 89 Lynx p o p u l a t i o n s i n n a t u r e c e r t a i n l y do not d e c l i n e a t the r a t e i n d i c a t e d by t h e s e s i m u l a t i o n s . The s u r p r i s i n g l y r a p i d d e c l i n e i n s i m u l a t e d p o p u l a t i o n s must r e s u l t from e s t i m a t e s of l y n x r e c r u i t m e n t t h a t a r e too low, or e s t i m a t e s of m o r t a l i t y r a t e s t h a t are too h i g h . My e s t i m a t e s of r e c r u i t m e n t i n t o the l y n x p o p u l a t i o n a r e based on pregnancy r a t e s , and on i_n u t e r o l i t t e r s i z e s found by Brand and K e i t h (1979) i n c a r c a s s e s c o l l e c t e d from t r a p p e r s . They t h e r e f o r e seem t o be w e l l founded. I t i s t h e r e f o r e l i k e l y t h a t both my and Brand and K e i t h (1979)'s e s t i m a t e s of m o r t a l i t y r a t e s a r e t o o h i g h . Two components of m o r t a l i t y are i n c l u d e d i n my models: 1) k i t t e n m o r t a l i t y from b i r t h t o the s t a r t of t h e i r f i r s t t r a p p i n g season (May t o November) arid 2) t r a p p i n g and n o n - t r a p p i n g m o r t a l i t y f o l l o w i n g i n i t i a l k i t t e n m o r t a l i t y . I assumed no k i t t e n m o r t a l i t y a t h i g h hare abundance, c l e a r l y e r r i n g i n f a v o r of h i g h e r r e c r u i t m e n t than c o u l d a c t u a l l y be o c c u r r i n g i n n a t u r e . E s t i m a t e s of k i t t e n m o r t a l i t y r a t e s a t i n t e r m e d i a t e and low hare abundances were d e r i v e d from Brand and K e i t h (1979) and s e t a t 65 and 92% r e s p e c t i v e l y . K i t t e n m o r t a l i t y r a t e s may be lower a t i n t e r m e d i a t e and low hare abundance than those e s t i m a t e d . E v i d e n c e from t h i s and o t h e r s t u d i e s do, however, suggest e x t r e m e l y low k i t t e n s u r v i v a l d u r i n g p e r i o d s of low hare abundance. Both Brand and K e i t h (1979) and I , saw no e v i d e n c e of k i t t e n s on our study a r e a s d u r i n g p e r i o d s of low hare abundance. Brand and K e i t h (1979) a l s o found l e s s than 3 p e r c e n t k i t t e n s i n c a r c a s s c o l l e c t i o n s d u r i n g p e r i o d s of low hare abundance. D u r i n g p e r i o d s of h i g h 90 hare abundance, k i t t e n s c o m p r i s e d 18 t o 30 p e r c e n t of t r a p p e d samples. In any e v e n t , even w i t h 100% k i t t e n s u r v i v a l at i n t e r m e d i a t e and low hare abundance, l y n x p o p u l a t i o n s s h o u l d c o n t i n u e t o d e c l i n e under the observed m o r t a l i t y r a t e s . A d u l t m o r t a l i t y r a t e s i n model A were d e r i v e d from t h i s and pa s t l y n x t a g g i n g s t u d i e s . These e s t i m a t e s may be t o o h i g h f o r two r e a s o n s . F i r s t , t hese e s t i m a t e s a r e based on a t o t a l of 36 tagged l y n x . The h i g h m o r t a l i y r a t e s observed might t h e r e f o r e be due t o random chance w i t h i n the s m a l l sample. The f a c t t h a t t h e 6 s t u d i e s from which t h e s e 36 a n i m a l s were drawn a l l had m o r t a l i t y r a t e s i n exce s s of 0.30, the maximum annual m o r t a l i t y r a t e t h a t r e c r u i t m e n t i n t o the p o p u l a t i o n c o u l d s u s t a i n , s u g g e s t s t h a t low sample s i z e i s not the complete answer. A l t e r n a t i v e l y , the m o r t a l i t y r a t e s o b s e r v e d i n the s e s t u d i e s may be r e p r e s e n t a t i v e of m o r t a l i t y r a t e s i n areas s i m i l a r t o those i n which the s t u d i e s took p l a c e . For reasons of l o g i s t i c ease, f i e l d s t u d i e s on l y n x , as w i t h o t h e r mammals, ar e most o f t e n u ndertaken i n a r e a s of r e l a t i v e l y h i g h a c c e s s i b i l i t y . These a r e a l s o the a r e a s where t r a p p i n g p r e s s u r e i s l i k e l y t o be most i n t e n s e . T r a p p i n g m o r t a l i t y r a t e s i n remote a r e a s where a c c e s s i s l i m i t e d may be f a r lower. Average t r a p p i n g m o r t a l i t y r a t e s over l a r g e a r e a s would t h e r e f o r e be c o n s i d e r a b l y l e s s than t h o s e noted i n a r e a s of h i g h a c c e s s i b l i t y . I f t h i s i s the c a s e , remote a r e a s may be e x t r e m e l y i m p o r t a n t i n m a i n t a i n i n g l y n x p o p u l a t i o n s d u r i n g the d e c l i n e s and lows i n hare abundance. The importance of remote a r e a s i n m a i n t a i n i n g l y n x p o p u l a t i o n s t h r o u g h p e r i o d s of low 91 r e c r u i t m e n t was f i r s t suggested by B e r r i e (1974). W i t h c o n t i n u a l l y i n c r e a s i n g a c c e s s i n t o these remote a r e a s , l y n x p o p u l a t i o n s may be s u b j e c t e d t o u n i f o r m l y h i g h human m o r t a l i t y r a t e s throughout l a r g e p a r t s of t h e i r range r e s u l t i n g i n u n s u s t a i n a b l e h a r v e s t r a t e s . The importance of remote a r e a s i n m a i n t a i n i n g l y n x p o p u l a t i o n s c l e a r l y needs more r e s e a r c h . Concern f o r the c o n t i n u e d e x i s t a n c e of l y n x p o p u l a t i o n s under i n t e n s i v e t r a p p i n g p r e s s u r e has been e x p r e s s e d by s e v e r a l r e s e a r c h e r s ( P a r k e r e t a l . 1983, Todd 1983, Carbyn and P a t r i q u i n 1983, Brand and K e i t h 1979 and B e r r i e 1974). Caughley (1977) suggested t h a t a " t r a c k i n g s t r a t e g y " , where h a r v e s t r a t e s v a r y d i r e c t l y w i t h r e c r u i t m e n t i n t o the h a r v e s t a b l e p o p u l a t i o n , was the o n l y workable s t r a t e g y f o r p o p u l a t i o n s w i t h dynamics s i m i l a r t o those of l y n x . R e s e a r c h e r s were i n f a c t recommending a t r a c k i n g s t r a t e g y f o r the h a r v e s t i n g of l y n x p o p u l a t i o n s y e a r s p r i o r t o the p u b l i c a t i o n of Caughley's (1977) book. B e r r i e (1974), i n an i n s i g h t f u l d i s c u s s i o n of the f u t u r e of l y n x p o p u l a t i o n s i n A l a s k a , recommended t h a t no l y n x t r a p p i n g be a l l o w e d f o r as much as 3 y e a r s d u r i n g the c y c l i c low i n hare abundance. He suggested t h a t w i t h improved a c c e s s t o w i l d e r n e s s a r e a s and c o n t i n u e d t r a p p i n g throughout the c y c l i c low would r e s u l t i n a d e c r e a s e d c y c l i c a m p l i t u d e by r e d u c i n g the number of i n d i v i d u a l s a v a i l a b l e t o breed when c o n d i t i o n s improved. Brand and K e i t h (1979) r e i t e r a t e d t h i s recommendation w i t h the h e l p of 2 s i m u l a t i o n models of t r a p p e d and untrapped l y n x p o p u l a t i o n s . T h e i r models i n d i c a t e d a 28% i n c r e a s e i n the t o t a l h a r v e s t a b l e l y n x p o p u l a t i o n t h r o u g h one complete c y c l e i f t r a p p i n g were v 92 c u r t a i l e d d u r i n g the t h r e e y e a r s of l y n x p o p u l a t i o n d e c l i n e and low. P a r k e r e t a l . (1983) noted t h a t the l y n x h a r v e s t i n Nova S c o t i a was c u r t a i l e d d u r i n g a p e r i o d of snowshoe hare s c a r c i t y and low r e c r u i t m e n t i n t o the l y n x p o p u l a t i o n . He recommended t h a t a system of h a r v e s t c u r t a i l m e n t be c o n t i n u e d d u r i n g f u t u r e p e r i o d s of snowshoe hare s c a r c i t y and low r e c r u i t m e n t i n t o l y n x p o p u l a t i o n s . Todd (1983) a l s o p r e s e n t e d a case f o r c u r t a i l m e n t of l y n x t r a p p i n g i n A l b e r t a f o r 3 t o 4 y e a r s d u r i n g the c y c l i c d e c l i n e and low i n l y n x p o p u l a t i o n numbers. The u n d e r l y i n g assumption i n Caughley's t r a c k i n g s t r a t e g y , and the h a r v e s t p l a n s recommended f o r l y n x by p r e v i o u s r e s e a r c h e r s , i s t h a t t r a p p i n g m o r t a l i t y i s l a r g e l y a d d i t i v e t o n o n - t r a p p i n g m o r t a l i t y . That i s , l y n x t h a t a r e t r a p p e d would o t h e r w i s e s u r v i v e t h rough the the low i n hare abundance t o reprod u c e when c o n d i t i o n s improved. A l t e r n a t i v e l y , t r a p p i n g m o r t a l i t y may be compensatory f o r n o n - t r a p p i n g m o r t a l i t y d u r i n g p e r i o d s of low prey abundance. I n d i v i d u a l s which a r e t r a p p e d d u r i n g p e r i o d s of low pr e y a v a i l a b i l i t y would d i e of n a t u r a l causes anyway b e f o r e c o n d i t i o n s improved. T r a p p i n g m o r t a l i t y , or some p r o p o r t i o n of i t , would t h e r e f o r e have no e f f e c t on the number of i n d i v i d u a l s s u r v i v i n g t o breed when c o n d i t i o n s improved. In our s i m u l a t i o n s of the dynamics of l y n x p o p u l a t i o n s , both Brand and K e i t h (1979) and I assumed t r a p p i n g and non-t r a p p i n g m o r t a l i t y were a d d i t i v e . Brand and K e i t h (1979) s u p p o r t e d t h i s assumption w i t h the o b s e r v a t i o n t h a t l y n x r e s i d e n t on t h e i r study a r e a a t the end of one t r a p p i n g season 93 but were not p r e s e n t the f o l l o w i n g w i n t e r . They c o n c l u d e d t h a t the l y n x must have d i e d d u r i n g the summer and t h e i r m o r t a l i t y was t h e r e f o r e a d d i t i v e t o t r a p p i n g m o r t a l i t y . They e x t r a p o l a t e t o assume t h a t a l l n o n - t r a p p i n g m o r t a l i t y o c c u r s o u t s i d e the t r a p p i n g season. I t would be s u r p r i s i n g i f a l l n o n - t r a p p i n g m o r t a l i t y o c c u r r e d d u r i n g the most benign time of y e ar from May t o November. In my s t u d y , 42% of r a d i o - t a g g e d l y n x d i s p e r s e d d u r i n g the p e r i o d of r a p i d d e c l i n e i n hare abundance and a l l d i s p e r s a l o c c u r r e d d u r i n g the snow-free p e r i o d . I t i s p o s s i b l e t h e n , t h a t the l y nx i n Brand and K e i t h ' s (1979) study d i s p e n s e d from the a r e a r a t h e r than d i e d . A l s o , the d e a t h of one of my l y n x , presumably t o s t a r v a t i o n , d u r i n g the low i n hare abundance s u g g e s t s t h a t not a l l l y n x would s u r v i v e the c y c l i c low i n hare abundance even w i t h o u t t r a p p i n g . Brand and K e i t h (1979)'S model suggested t h a t w i t h n a t u r a l m o r t a l i t y up t o 50% compensatory f o r t r a p p i n g m o r t a l i t y , a net g a i n i n h a r v e s t a b l e l y n x t h r o u g h a complete c y c l e would be a c h i e v e d by c u r t a i l i n g t r a p p i n g d u r i n g the 3 y e a r s of low l y n x r e c r u i t m e n t . T r a p p i n g m o r t a l i t y may be more than 50% compensatory f o r n o n - t r a p p i n g m o r t a l i t y d u r i n g p e r i o d s of low h are abundance. I f t h i s i s the c a s e , c o n t i n u i n g t o h a r v e s t l y n x t h r o u g h the low i n hare abundance would have l i t t l e or no a f f e c t on the r e c o v e r y of l y n x p o p u l a t i o n s when hare abundance i n c r e a s e d . T h e r e f o r e , a l t h o u g h I a p p l a u d the e f f o r t s of Brand and K e i t h (1979) and o t h e r s who have a t t e m p t e d t o d e v e l o p sound .94 management schemes f o r l y n x , i t would be premature t o impliment t h e s e 'pla n s w i t h o u t f u r t h e r t e s t i n g . The e f f e c t i v e n e s s of any p l a n can o n l y be d e t e r m i n e d i f i t i s conducted w i t h i n the c o n f i n e s of a sound e x p e r i m e n t a l d e s i g n . T h i s would e n t a i l s e t t i n g up r e p l i c a t e study a r e a s . One study a r e a would be t r a p p e d c o n t i n u o u s l y , as under c u r r e n t management schemes f o r l y n x , and i n the second a r e a t r a p p i n g would be c u r t a i l e d d u r i n g the p e r i o d of low l y n x r e c r u i t m e n t as suggested i n Brand and K e i t h (1979)'S management p l a n . By m o n i t o r i n g l y n x r e c r u i t m e n t r a t e s , t r a p p i n g and n o n - t r a p p i n g m o r t a l i t y r a t e s and t o t a l l y n x h a r v e s t i n the 2 a r e a s the e f f e c t i v e n e s s of " t r a c k i n g s t r a t e g y " c o u l d be a s s e s s e d . T h i s type of experiment i s e s s e n t i a l i n a s s e s s i n g the e f f e c t i v e n e s s of any new management s t r a t e g y (Romesburg 1981, W a l t e r s and H i l b o r n 1976). 95 REFERENCES CITED Adams, A.W. 1963. The l y n x e x p l o s i o n . N o r t h Dakota Outdoors. 26(5):20-24. Anonymous.1982. Canadian T r a p p e r s Manual. Canadian Trappers F e d e r a t i o n , P.O. Box 140 N o r t h Bay, O n t a r i o P1B 8G8. B a i l e y , T.N. 1974. S o c i a l o r g a n i z a t i o n i n a bobcat p o p u l a t i o n . J . W i l d l . Manage. 38:435-446. B a i l e y , T.N. 1981. 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See T a b l e 6 f o r parameter e s t i m a t e and t h e i r d e r i v a t i o n . 100 IF T l > 0 THEN 200 105 T = .55:N = .06: REM T=TRAPP ING MORTALITY RATE AND N= NA TURAL MORTALITY RATE 110 NY = 7:NA = 93: REM NY= NUMB ER OF YEARLINGS IN INITIAL P •PULATION AND NA = NUMBER OF ADULTS IN INITIAL POPULATIO N 120 A = 0 200 IF A ^ = = 1 THEN 207 201 ,IF A > 1 AND A < = 4 THEN 2 06 202 IF A > 4 AND A < = 6 THEN 2 07 204 IF A > 6 AND A < = 9 THEN 2 08 205 : REM IN LINES 2 06 TO 208 RY =AVERAGE NUMBER OF KITTENS P RODUCED PER YEARLING FEMALE PER YEAR; RA = AVERAGE NUMBE R OF KITTENS PRODUCED PER AD ULT FEMALE PER YEAR 206 RY = 1.6:RA = 3.4: GOTO 210 207 RY = 0:RA = .6: GOTO 210 208 RY = O:RA = .1 210 NK = NY * .5 * RY + NA * .5 * RA: REM NK=YEARS PRODUCTION OF KITTENS 220 NA = NY + NA - (NY + NA) * (T + N) 230 NY = NK - NK * (T + N) 240 NT = NY + NA: REM NT= TOTAL PRE-BREEDING SEASON POPULATI ON 241 IF A < = 9 THEN A = 242 IF A > 9 THEN A = 0 250 Z(1,TI) = NT 251 Z(2,TI) = NA Z(3,TI> = NY 253 Z(4,TI) NK 105 Appendix l b . Program f o r s i m u l a t i o n model B. Program i s w r i t t e n i n BASIC f o r APPLE l i e microcomputer and c o m p i l e d w i t h m i c r o simcon p o p u l a t i o n s i m u l a t i o n package ( W a l t e r s 1982). See T a b l e 6 f o r parameter e s t i m a t e and t h e i r d e r i v a t i o n . 100 IF TI > 0 THEN 200 105 T = 0.14:N = 0.35: REM T= TR APPING MORTALITY RATE AND N= NATURAL MORTALITY RATE 110 NY = 7:NA =93: REM NY=NUMBE R OF YEARLINGS IN INITIAL PO PULATION AND NA=NUMBER OF AD ULTS IN INITIAL POPULATION 120 A =.0 200 IF A < = 1 THEN 207 201 IF A > 1 AND A < = 4 THEN 2 06 202 IF A > 4 AND A < = 6 THEN 2 07 204 IF A > 6 AND A < = 9 THEN 2 OB 205 : REM IN LINES 206 TO 208 RY =AVERAGE NUMBER OF KITTENS P RDDUCED PER YEAR PER YEARLIN G FEMALE AND RA= AVERAGE NUM BER OF KITTENS PRODUCED PER ADULT FEMALE PER YEAR 206 RY = 1.6:RA = 3.4: GOTO 210 207 RY = 0:RA = .6: GOTO 210 208 RY = 0:RA = .1 210 NK = NY * .5 * RY + NA * .5 * RA: REM NK= YEARS PRODUCT10 N OF YOUNG 215 NA = NA - (NA * N): REM CALC ULATION OF ADULT POPULATION PRIOR TO TRAPPING SEASON 217 NY = NY - (NY * N): REM CALC ULATION OF YEARLING POPULATI ON PRIOR TO TRAPPING SEASON 220 NA = NA + NY - (NA + NY) * T: REM CALCULATION OF POST TR APPING SEASON ADULT POPLUATI ON 230 NY = NK - NK * (T): REM CALC ULATION OF POST TRAPPING SEA SON YEARLING POPULATION 240 NT = NY + NA: REM CALCULATIO N OF TOTAL POPULATION SIZE I N SPRING 241 IF A < = 9 THEN A = A + 1 242 IF A > 9 THEN A = O 250 Z(1,TI) = NT 251 Z(2,TI) = NA 252 Z(3,TI) = NY 253 Z(4,TI) = NK 

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