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Conifer seed predation by the deer mouse : a problem in reforestation Sullivan, Thomas Priestlay 1978

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CONIFER SEED PREDATION BY THE DEER MOUSE: A PROBLEM IN REFORESTATION by T.HOHAS PRIESTLAY SULLIVAN B- Sc. (Hons.) , U n i v e r s i t y o f B.C., 1973 H.Sc., U n i v e r s i t y of B.C., 1976 THESIS .SUBMITTED IN PARTIAL FULFILLMENT 0 THE REQUIREMENTS FOR THE DEGHEE OF DOCTOR -OF PHILOSOPHY i n THE FACULTY OF GRADUATE STUDIES (Departmeat of Zoology) We accept t h i s t h e s i s as conforming to the r e g u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA NOVEMBER, 1978 © Thomas P r i e s t l a y S u l l i v a n , 1978 In present ing t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree tha t the 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 re fe rence and s tudy. I f u r t h e r agree tha t permiss ion f o r ex tens ive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s en t a t i v e s . I t i s understood tha t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be a l lowed wi thout my w r i t t e n pe rm iss i on . Department n f Z o o l o g y  The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook P lace Vancouver, Canada V6T 1W5 Qg-j-g January 1 8 , 1 9 7 9 . Abstract fieforestation of c u t o v e r f o r e s t land by d i r e c t a p p l i c a t i o n of seed has long been a go a l of f o r e s t e r s i n North America. D e s t r u c t i o n o f the seed supply by s m a l l mammals and b i r d s has r e s u l t e d i n a general f a i l u r e o f these r e f o r e s t a t i o n p r o j e c t s -Numerous techniques have been developed f o r p r o t e c t i n g t r e e seed from rodents and s e e d - e a t i n g b i r d s . C o n v e n t i o n a l c o n t r o l methods i n c l u d e mechanical d e v i c e s , poison b a i t s , and chemical r e p e l l e n t s a p p l i e d d i r e c t l y t o seeds. None of these techniques has been s u c c e s s f u l . L i t t l e r esearch has been done on methods i n v o l v i n g b i o l o g i c a l c o n t r o l , and consequently, t h i s t h e s i s w i l l d e s c r i b e the development of a b i o l o g i c a l technique f o r reducing c o n i f e r seed p r e d a t i o n i n deer mice. The e f f e c t s of f o r e s t r y p r a c t i c e on p o p u l a t i o n s of deer mice and other s m a l l mammals have been w e l l documented. Most s t u d i e s have concluded t h a t there a re higher d e n s i t i e s of deer mice and r e l a t e d s m a l l mammals on c l e a r c u t areas than i n f o r e s t e d r e g i o n s . The f i r s t c h a pter i n t h i s t h e s i s was designed to t e s t the w i d e l y - h e l d hypothesis t h a t c l e a r c u t (logged) h a b i t a t s support h i g h e r d e n s i t y p o p u l a t i o n s of Peromyscus than do f o r e s t e d h a b i t a t s . Deer mouse p o p u l a t i o n s were l i v e - t r a p p e d i n f o r e s t and c l e a r c u t h a b i t a t s at Maple Bidge, B r i t i s h Columbia, from May 1975 to A p r i l 1978. Another c l e a r c u t p o p u l a t i o n was monitored from A p r i l 1977 to A p r i l 1978. The average d e n s i t y of mice per ha i n the f o r e s t was: 19.6 (1975), 15.8 (1976), 22.3 (1977) and on the c l e a r c u t areas was: 23.3 (1975), 16.6 (1976), 29.9 and 20.2 (1977). The s l i g h t l y h i g h e r number of animals on the c l e a r c u t i n 1975, and on one of the c l e a r c u t areas i n 1977, r e f l e c t e d a burst of recruitment i n the l a t e summer and f a l l of each year- The d e n s i t y of mice on c l e a r c u t areas d e c l i n e d during each winter t o a l e v e l comparable to t h a t i n the f o r e s t - More female mice were breeding on the c l e a r c u t i n a l l years than i n the f o r e s t , but there was l i t t l e d i f f e r e n c e i n male r e p r o d u c t i o n . F o r e s t animals sere c o n s i s t e n t l y h e a v i e r than those on the c l e a r c u t . J u v e n i l e male deer mice were ab l e to enter i n t o the c l e a r c u t p o p u l a t i o n s d u r i n g the breeding season i n the f i r s t year a f t e r l o g g i n g . The second chapter was designed to t e s t the hypothesis t h a t removal of a l l deer mice from a given area would r e s u l t i n s a t i s f a c t o r y s u r v i v a l of c o n i f e r seed. Areas of 1.1 ha were c l e a r e d of deer mice and r e l a t e d s m a l l mammals. C o l o n i z a t i o n of these depopulated areas by deer mice and the s u r v i v a l o f Douglas f i r seed d i s p e r s e d over the c l e a r c u t were monitored. During the f a l l # a t o t a l o f 99 mice c o l o n i z e d a depopulated area. Animals c o n t i n u a l l y moved onto the a r e a , and 95% of the c o n i f e r seed was l o s t w i t h i n a 3-day p e r i o d . S i m i l a r l y , d u r i n g a removal experiment i n the s p r i n g , a t o t a l o f 48 mice immigrated i n t o the vacant h a b i t a t from surrounding r e g i o n s . These animals destroyed 92.6% of the c o n i f e r seed w i t h i n a 5-day p e r i o d . T h i s i n t e n s i v e study of seed s u r v i v a l and movements of deer mice on c o n t r o l and removal areas has shown the f u t i l i t y of b a i t i n g owing to the r a p i d r e i n v a s i o n by mice and consequent d e s t r u c t i o n of the seed s u p p l y . The t h i r d chapter d i s c u s s e s the use of a l t e r n a t i v e foods as a b i o l o g i c a l c o n t r o l technique which has s u c c e s s f u l l y reduced c o n i f e r seed p r e d a t i o n by deer mice., The upper l i m i t s to the iv number of mice and number of seeds taken per mouse were determined over a wide range of d e n s i t i e s of Couglas f i r seed. The number of seeds taken s t a b i l i z e d at about 860,000 seeds/ha. Experiments with a l t e r n a t i v e foods were done a t t h i s seed d e n s i t y i n r a t i o s of 7 sunflower t o 1 Douglas f i r and 5 sunflower to 2 o a t s t o 1 Douglas f i r seed. These mixtures produced the best r e s u l t s : 70% s u r v i v a l o f c o n i f e r seed a f t e r 2 weeks and 50% s u r v i v a l a f t e r H weeks compared with 5% s u r v i v a l of c o n t r o l Douglas f i r by i t s e l f . These r e s u l t s were obtained i n the e a r l y s p r i n g (March to A p r i l ) with s i m i l a r l y f a v o u r a b l e r e s u l t s obtained i n t h e f a l l (November to December). Seeding experiments with a l t e r n a t i v e foods during other times of the year and with lower d e n s i t i e s of sunflower seeds were not s u c c e s s f u l . The f o u r t h and f i f t h c h a p t e r s d i s c u s s the a p p l i c a t i o n of t h i s b i o l o g i c a l c o n t r o l technique to r e f o r e s t a t i o n by d i r e c t seeding. The very best time f o r seeding with r e s p e c t to low pop u l a t i o n s of s e e d - e a t i n g s m a l l mammals (chipmunks and deer mice) and b i r d s ( s e v e r a l species) i s i n the l a t e w i n t e r - e a r l y s p r i n g i n southwestern D.C. This p e r i o d f i t s i n well with the presumed most f a v o u r a b l e time f o r c o n i f e r seed germination. The recommended mixture of seed to be a e r i a l l y seeded over a c l e a r c u t area i s as f o l l o w s : 0.10 kg Douglas f i r seed or other c o n i f e r seed ( e q u i v a l e n t number of seeds by weight) to 56 kg sunflower seed and 7 kg oats per ha. V TABLE 07 CONTENTS Ab s t r a c t ................................................. i TABLE OF CONTENTS ....... i v LIST OF FIGURES ......................... ^  .. ^  ........ v i i LIST OF TABLES ................................. . . . . . . . . X ACKNOWLEDGEMENTS ......................................... x i i GENERAL INTRODUCTION .. 1 DESCRIPTION OF STUDY AREAS ... 4 CHAPTER 1. DEMOGRAPHY OF POPULATIONS OF DEES MICE IN FOREST AND CLEARCUT (LOGGED) HABITATS. . . ... 7 INTRODUCTION ........................................... 7 MATERIALS AND METHODS ........ 9 RESULTS ................................................ 11 T r a p p a b i l i t y ......................................... 11 Po p u l a t i o n d e n s i t y and re c r u i t m e n t ................... 12 Reproduction ......................................... 14 M o r t a l i t y 16 Growth ...... ,.....,..........,.....y............... 20 Sex r a t i o s ........................................... 23 DISCUSSION - 23 FIGUBES .......... ............................... 31 TABLES ................................................. 49 CHAPTER 2. BEPOPULATION OF VACANT CLEABCUT HAEITAT AND CONIFEB SEED PREDATION BY THE DEEB MOUSE- 57 IN T80DUCTION ..... 57 MATERIALS AND METHODS ................. ' m ...... , ...... 59 RESULTS 61 Trappa.bil.ity ......................................... 61 Experimental poison b a i t i n g .......................... 62 DISCUSSION .... 66 FIGUBES ................................ .......... 73 TABLES .... 87 CHAPTER 3. THE USE OF ALTERNATIVE FOODS TO REDUCE CONIFER SEED PBEDATION BY DEEB MICE 90 INTRODUCTION 90 MATERIALS AUD METHODS .................. 92 Douglas f i r seed p o p u l a t i o n s ......................... 93 Predation ............................................ 94 B a d i o a c t i v e l y - t a g g e d seed ............................ 95 I n v e r t e b r a t e p o p u l a t i o n s ............................. 96 Laboratory s t u d i e s ................................... 97 a l t e r n a t i v e food seed t r i a l s ......................... 97 RESULTS .................... - 99 T r a p p a b i l i t y ............ ..... ........................ 100 Experimental se e d i n g with Douglas f i r seed ........... 101 Seed consumption ..................................... 101 B a d i o a c t i v e l y - t a g g e d seed ........................ 102 I n v e r t e b r a t e s ........................................ 103 Responses of deer mice to Douglas f i r seeds .......... 103 Experimental seeding with Douglas f i r seed and a l t e r n a t i v e foods .................................... 105 DISCUSSION .... ..................... ............ 109 FIGUBES .......... ---- . 116 TABLES ............. ...... , 140 CHAPTER 4. SEASONAL ABUNDANCES OF CONIFER SEED y i i PREDATORS. ....................... 151 INTRODUCTION ..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151 MATERIALS AND METHODS . ---- 152 Chipmunk p o p u l a t i o n s ................................. 152 Copulations o f s e e d - e a t i n g b i r d s ..................... 153 RESULTS ....... - --- 153 Chipmunk p o p u l a t i o n s ................................. 153 Popu l a t i o n s o f s e e d - e a t i n g b i r d s ..................... 154 DISCUSSION .... . 154 FIGURES 157 CHAPTER 5. REFORESTATION BY DIRECT SEEDING »ITH CONIFER SEED AND ALTERNATIVE FOODS. ..................... 161 INTRODUCTION .............. 161 RESULTS ....... ......... .......................... 162 D i r e c t seeding with Douglas f i r seed and a l t e r n a t i v e foods. .................................. 162 A p p l i c a t i o n i n r e f o r e s t a t i o n p r o j e c t s ................. 163 Economic a s p e c t s ..................................... 164 DISCOSSION ..................................... ........ 164 FIGURES , 169 LITERATURE CITED 173 v i i i LIST OF FIGOHES Fi g u r e 1.1. L o c a t i o n o f the f o u r study a r e a s . .......... 32 F i g u r e 1-2- A e r i a l photograph of the Burn, S l a s h , and f o r e s t study areas. ........................ 34 F i g u r e 1.3. A e r i a l photograph of the Loon Lake study a r e a . ................................ 36 Fi g u r e 1.4. L i v e - t r a p g r i d with t r a p s t a t i o n s and seed sampling guadrats. ................ 38 Figure 1.5. P o p u l a t i o n d e n s i t y on f o r e s t and Burn c o n t r o l g r i d s . ............................. 40 F i g u r e 1.6. P o p u l a t i o n d e n s i t y on the Loon Lake c o n t r o l g r i d . .............................. 42 Fi g u r e 1.7. Mean body weights f o r deer mice during summer p e r i o d s . ............................ 44 Fi g u r e 1.8. Growth r a t e s f o r deer mice during 1975-77. . 46 F i g u r e 1.9. Median body weight at s e x u a l m a t u r i t y f o r deer mice d u r i n g summer p e r i o d s . ........... 48 Fi g u r e 2.1a. Hap o f study area f o r removal experiments. 74 Fi g u r e 2.1b. P r e d i c t e d response of mice moving onto the removal area. .......................... 76 F i g u r e 2.2. O r i g i n o f mice c o l o n i z i n g removal g r i d J during experiment A- ....................... 78 F i g u r e 2.3. O r i g i n o f mice c o l o n i z i n g removal g r i d J du r i n g experiment B. ....................... 80 Fi g u r e 2.4. P o p u l a t i o n d e n s i t y on g r i d s H, I , and J . ... 82 F i g u r e 2.5- O r i g i n o f mice c o l o n i z i n g removal g r i d J during experiment C. ....................... 84 ix F i g u r e 2.6. O r i g i n o f mice c o l o n i z i n g removal g r i d J during experiment D. ....................... 86 F i g u r e 3.1. Cumulative number of seeds taken during seeding t r i a l s i n 1975. ....................117 F i g u r e 3-2- Responses of numbers of mice to d i f f e r e n t d e n s i t i e s of Douglas f i r seed. .............119 Figu r e 3.3- Responses o f numbers o f new mice to d i f f e r e n t d e n s i t i e s of Douglas f i r seed. --...-.-.,..,121 F i g u r e 3.4. Number o f seeds taken per mouse per day at d i f f e r e n t seed d e n s i t i e s i n the f o r e s t . . 123 F i g u r e 3.5, Number of seeds taken per mouse per day at d i f f e r e n t seed d e n s i t i e s i n l a b o r a t o r y . . 125 F i g u r e 3.6. S u r v i v a l of Douglas f i r seed and sunflower seed (7:1 r a t i o ) i n August 1976. 127 Fi g u r e 3.7. S u r v i v a l o f a mixture of Douglas f i r seed and oats (7:1 r a t i o ) i n August 1976. 129 F i g u r e 3.8. S u r v i v a l o f Douglas f i r , sunflower, and oats (3:3:2 r a t i o ) i n August 1976. ...... .... 131 F i g u r e 3.9. S u r v i v a l of Douglas f i r and sunflower seed (7:1 r a t i o ) i n November 1976. .............. 133 F i g u r e 3.10. S u r v i v a l of Douglas f i r and sunflower (7:1 r a t i o ) on the c l e a r c u t i n s p r i n g 1977. 135 Fi g u r e 3.11. S u r v i v a l o f Douglas f i r and sunflower (7:1 r a t i o ) i n the f o r e s t i n s p r i n g 1977- -. 137 F i g u r e 3.12. S u r v i v a l o f Douglas f i r , sunflower, and oats (5:2:1 r a t i o ) i n November 1S77. ....... 139 F i g u r e 4.1. Numbers of chipmunks on the Burn and S l a s h t r a p l i n e s d u r i n g 1976-77. .................. 158 X F i g u r e 4.2. Numbers of the s i x most common seed - e a t i n g b i r d s p e c i e s on the Burn. .................. 160 F i g u r e 5.1. Success o f d i f f e r e n t Douglas f i r to sunflower (and oats) r a t i o s . ......................... 170 F i g u r e 5.2. Procedure f o r s u c c e s s f u l r e f o r e s t a t i o n with c o n i f e r seed and a l t e r n a t i v e f o o d s . ........ 172 x i LIST OF TABLES Table 1-1. T r a p p a b i l i t y e s t i m a t e s f o r deer mice on the th r e e study a r e a s . .......................... 49 Table 1.2. P r o p o r t i o n o f mice i n breeding c o n d i t i o n . ... 50 Table 1.3. Minimum s u r v i v a l r a t e s f o r mice on the three study areas. ................................ 51 Table 1.4. I n d i c e s of e a r l y j u v e n i l e s u r v i v a l - ......... 52 Table 1.5. Number o f s u c c e s s f u l pregnancies and j u v e n i l e r e c r u i t s . ................................... 53 Table 1.6. Sex r a t i o s i n the three p o p u l a t i o n s . ........ 54 Table 1.7. Comparison o f summer and f a l l d e n s i t i e s i n f o r e s t and c l e a r c u t h a b i t a t s . ............... 55 Table 1.8. Summary of annual v a r i a t i o n i n demography. ... 56 Table 2.1. T r a p p a b i l i t y estimates f o r mice on c o n t r o l and experimental areas., ......................... 87 Tabl e 2.2. Comparison o f seed s u r v i v a l on c o n t r o l and removal g r i d s . .............................. 88 Tabl e 2.3. Numbers o f v o l e s and shreus on c o n t r o l and experimental g r i d s . ......................... 89 Table 3.1. T r a p p a b i l i t y e s t i m a t e s f o r mice on the c o n t r o l and s i x experimental g r i d s . ......... 140 Tabl e 3.2. Mean number of seeds per stomach at two d i f f e r e n t seed d e n s i t i e s . ................... 141 Table 3.3. Number o f seed caches and p r o p o r t i o n of whole and eaten seeds., ...................... 142 Appendix 3.1. The means, standard e r r o r s , and 95% c o n f i d e n c e l i m i t s f o r seed t r i a l s . .......... 143 Appendix 3.2- Summary o f f i e l d data f o r number of seeds taken per mouse per day- .............. 150 x i i i ACKNOWLEDGEMENTS I thank C h a r l e s J . Krebs f o r h i s guidance and encouragement duri n g t h i s study and Dennis C h i t t y f o r h i s h e l p f u l comments on the t h e s i s . I a l s o thank J . H a l t e r s and h i s s t a f f a t the U.B.C. Research F o r e s t f o r t h e i r h e l p and co o p e r a t i o n throughout the study, and Kent Humphrey and B i l l Kachuk f o r a s s i s t a n c e i n r a d i o a c t i v e tagging of the seeds. For help with the f i e l d work, I thank JBudy Boonstra, C h r i s Fleming, John F r y x e l l , D a r y l Jahnke, Walter K a i s e r J r . , Dick L a n c a s t e r , Lance Nordstrom, E r i c ¥atts, and Big White. S p e c i a l thanks go to Dru S u l l i v a n f o r her c o n t i n u a l i n s p i r a t i o n and encouragement durin g the f i e l d work and s y n t h e s i s o f t h i s study. F i n a n c i a l support was provided by the B.C. F o r e s t S e r v i c e , N.H.C. funds awarded t o C.J. Krebs, and by a U.B.C. F e l l o w s h i p f o r which I am most g r a t e f u l . 1 GENEBAL IMTBODDCTIOH For almost h a l f a century f o r e s t e r s i n North America have used d i r e c t seeding as a method o f r e g e n e r a t i n g c u t o v e r f o r e s t l a n d s . D e s t r u c t i o n o f the seed supply by s m a l l mammals and b i r d s has had adverse e f f e c t s on the success of these r e f o r e s t a t i o n p r o j e c t s . Black (1969), Badwan (1970), and Badvanyi (1973) have pr o v i d e d comprehensive reviews on t h i s s u b j e c t . The deer mouse (Peromyscus maniculatus) i s con s i d e r e d to be the most important seed predator i n the P a c i f i c Northwest. Chipmunks, m i c r o t i n e s , and s e v e r a l s p e c i e s o f seed - e a t i n g b i r d s have a l s o c o n t r i b u t e d t o the problem by t h e i r consumption of c o n i f e r seeds (Black 1969; Badvanyi 1S73; Pank 1574). The e f f e c t s of l o g g i n g a c t i v i t y and f o r e s t r y p r a c t i c e on po p u l a t i o n s of deer mice and other s m a l l mammals have been w e l l documented (Hooven 1969, 1973; Gashwiler 1970; and Badvanyi 1973). In g e n e r a l , most s t n d i e s have concluded t h a t there are highe r d e n s i t i e s o f deer mice and r e l a t e d s m a l l mammals on c l e a r c u t areas than i n f o r e s t e d r e g i o n s . There have been two b a s i c approaches t o reducing c o n i f e r seed predation by s m a l l mammals and b i r d s . F i r s t l y , t h e r e are c o n v e n t i o n a l c o n t r o l methods which have mainly i n v o l v e d c h e m i c a l s , and secondly, t h e r e i s b i o l o g i c a l c o n t r o l . C o n v e n t i o n a l c o n t r o l methods have predominated, and the f o l l o w i n g d i s c u s s i o n about them i s based on reviews by Badwan (196S, 1970). C o n t r o l used i n the context o f t h i s t h e s i s means to c o n t r o l damage. Since the e a r l y 1900*s, f o r e s t managers i n the P a c i f i c Northwest have t r i e d numerous methods f o r p r o t e c t i n g c o n i f e r o u s 2 seeds from r o d e n t s and b i r d s . These i n c l u d e mechanical d e v i c e s , poison b a i t s , and t o x i c a n t s and r e p e l l e n t s a p p l i e d d i r e c t l y to seeds. Mechanical d e v i c e s such as screens have been too expensive and not p r a c t i c a l f o r l a r g e - s c a l e f i e l d p r o j e c t s such as r e f o r e s t a t i o n . Poison b a i t s are now c o n s i d e r e d i n e f f e c t i v e because c o n t r o l of rodents i s only p o s s i b l e f o r very s h o r t p e r i o d s . E l i m i n a t i o n of the i n i t i a l rodent p o p u l a t i o n i s incomplete and r e i n v a s i o n from surrounding areas i s o f t e n r a p i d (Gashwiler 1969; Badwan 1969; Hooven 1975). Poisons, e i t h e r as b a i t s or as t o x i c a n t s on seeds, are hazardous to non-target s p e c i e s , and the f a t e of these chemicals i n the environment i s unknown (see review by Evans 1974). In a d d i t i o n , the d i r e c t a p p l i c a t i o n of t o x i c a n t s and r e p e l l e n t s t o seeds has o f t e n r e s u l t e d i n reduced seed germination (Badwan 1969, 1S70). According to Evans (1974), a s u b s t a n t i a l change i n p r i o r i t i e s has taken p l a c e , from e x c l u s i v e r e l i a n c e on chemicals to r e s e a r c h d i r e c t e d towards non-chemical methods of c o n t r o l . There i s a trend to reduce the use of p e r s i s t e n t p e s t i c i d e s ( t o x i c a n t s and r e p e l l e n t s ) and r e p l a c e them with l e s s p e r s i s t e n t and l e s s hazardous c h e m i c a l s . In the meantime, perhaps methods of b i o l o g i c a l c o n t r o l can be developed which w i l l provide l o n g -term s o l u t i o n s to t h i s r e f o r e s t a t i o n problem. A broad concept of b i o l o g i c a l c o n t r o l with r e s p e c t to i n s e c t s has been d i s c u s s e d by van den Bosch (1971). T h i s concept i n v o l v e s an attempt t o reduce the average d e n s i t y of a pest p o p u l a t i o n by the a c t i o n of p a r a s i t e s , p r e d a t o r s , or d i s e a s e s . However, b i o l o g i c a l c o n t r o l can a l s o be more g e n e r a l l y d e f i n e d as a type o f c o n t r o l i n which the damage 3 caused by the pest i s reduced or e l i m i n a t e d by a b i o l o g i c a l agent or process. T h i s approach has been d i s c u s s e d by Howard (1967), who i n c l u d e s as b i o l o g i c a l c o n t r o l any h a b i t a t m o d i f i c a t i o n r e s u l t i n g i n reduced food and c o v e r , or i n t e n t i o n a l a l t e r a t i o n of the p e s t ' s environment which r e s u l t s i n lowered numbers of the pest s p e c i e s . I f we assume the pest p o p u l a t i o n does not have to be reduced i n s i z e , b i o l o g i c a l c o n t r o l may a l s o r e f e r t o the use of p r e f e r r e d (buffer) or a l t e r n a t i v e foods. T h i s process has shown some success i n l u r i n g waterfowl away from g r a i n and vegetable crops (Howard 1967). F l o c k s of dark-eyed juncos have been e a s i l y d i v e r t e d from f i r seed by s u p p l y i n g a r t i f i c i a l food a t j u s t one p l a c e on a cutover (Hagar 1860). Prunings p i l e d around the base of orchard t r e e s as a b u f f e r food have o f t e n minimized damage from meadow v o l e s ( F i t z w a t e r 1962). Browsing of c o n i f e r s e e d l i n g s by deer may be reduced by the a v a i l a b i l i t y of a l t e r n a t i v e and p r e f e r r e d s p e c i e s of browse (Campbell 1974). fiost s t u d i e s , to date, i n p r o v i d i n g a l t e r n a t i v e f o o d s , have been concerned with deer browsing (Hoy 1960; Barcn e t a l . 1966; Dasmann e t a l . 1967; and Campbell and Evans 1975) . The development o f a b i o l o g i c a l technique to counter c o n i f e r seed p r e d a t i o n i n the deer mouse has been based on the use of a l t e r n a t i v e foods. The technique i s d i s c u s s e d i n t h i s t h e s i s with respect t o the responses of deer mice t o v a r y i n g d e n s i t i e s of Douglas f i r seeds. I f the upper l i m i t s f o r the number of mice and number of seeds eaten per mouse can be determined, then the use of a l t e r n a t i v e foods with Douglas f i r seeds could r e s u l t i n reduced p r e d a t i o n on the c o n i f e r seeds. 4 Presumably, the mice develop what might be termed an " o l f a c t o r y search image" to e x p l o i t a food source. Howard and Cole (1967), Howard et a l . (1968), and Howard and Harsh (1970) have pr o v i d e d evidence t h a t mice f i n d t h e i r food by s m e l l . T h e r e f o r e , by i n t r o d u c i n g a l t e r n a t i v e foods of v a r y i n g p a l a t a b i l i t i e s , d e n s i t i e s , and d i s t r i b u t i o n s , the predators may switch to a new food source with a r e s u l t i n g i n c r e a s e d s u r v i v a l of c o n i f e r seeds. T h i s study was designed toz 1) Test the w i d e l y - h e l d hypothesis that c l e a r c u t (logged) h a b i t a t s support higher d e n s i t y p o p u l a t i o n s of Peromyscus than f o r e s t e d h a b i t a t s . 2) T e s t the h y p o t h e s i s t h a t removal of a l l deer mice w i l l r e s u l t i n s a t i s f a c t o r y s u r v i v a l of c o n i f e r seed. 3) Determine the responses of deer mice to a wide range of c o n i f e r seed d e n s i t i e s and the e f f e c t s of p r o v i d i n g more or b e t t e r a l t e r n a t i v e f o o d s . 4) Determine the s e a s o n a l abundances of c o n i f e r seed predators and how t h i s r e l a t e s to the best time f o r d i r e c t s e e d i ng. 5) Recommend the procedure by which t h i s b i o l o g i c a l technique should be a p p l i e d i n r e f o r e s t a t i o n p r o j e c t s . Each of these f i v e t o p i c s i s presented as a chapter i n t h i s t h e s i s . DESCRIPTION OF STUDY AREAS T h i s p r o j e c t was l o c a t e d i n the U n i v e r s i t y of B r i t i s h Columbia Research F o r e s t at Maple Ridge, B. C. (Figure 1.1). F i e l d i n s t a l l a t i o n s ( g r i d s and l i n e s ) were l o c a t e d i n f o r e s t and 5 c l e a r c u t h a b i t a t s (Figures 1.2 and 1.3). The f o r e s t h a b i t a t , i n the southeast c o r n e r of the Research F o r e s t , c o n s i s t e d of second-growth timber f o l l o w i n g a f i r e i n 1925. Na t u r a l r e g e n e r a t i o n began between 1930 and 1932 and r e s u l t e d i n a f o r e s t 43 t o 45 years o l d a t the time of my study. T h i s f o r e s t was dominated by western hemlock (Tsuga h e t e r o p h y l l a ) and western r e d cedar (Thuja p l i c a t a ) with seme Douglas f i r (Pseudptsuga m e n z i e s i i ) : ground v e g e t a t i o n was sparse. G r i d s A, B # C , B, E, F, and P were s i t u a t e d i n t h i s area and a l l were on r e l a t i v e l y f l a t t e r r a i n . The c l e a r c u t h a b i t a t (Eurn and S l a s h study areas) was l o c a t e d i n two areas i n the southern part of the Research F o r e s t . G r i d s G, H, I , and J were on an area logged i n the f a l l of 1973 f o l l o w e d by s l a s h burning i n August 1974. The s l a s h burn was uniform i n some areas but patchy i n o t h e r s . The main cover was burnt or dead s l a s h with growth of bracken (Pteridium aguilinum) , f i r e weed (Epilpbium an gust i f oliuTo) , and s e v e r a l o t h e r l e s s abundant s u c c e s s i o n a l herbs. G r i d Q was l o c a t e d i n the f o r e s t surrounding the nor t h and west s i d e s of g r i d J . G r i d s K and L were on a s i m i l a r area a l s o logged i n the f a l l of 1973 but not burnt. Cover i n c l u d e d dead s l a s h and a s i m i l a r s p e c i e s composition to that of the burn. There was a g r e a t e r abundance o f red a l d e r (Alnus r u b r a ) , b l a c k r a s p b e r r y (Rubus l e u c o d e r m i s ) , and salmonberry (Rubus s p e c t a b i l i s ) on the s l a s h a r e a. Of these s i x g r i d s , G was on a 20 degree s l o p e with southwest asp e c t , and a l l ot h e r s were on r e l a t i v e l y f l a t landscape. Another study a r e a was added i n 1977 on a cut o v e r area e a s t 6 of Lccn Lake (Figure 1.3). G r i d s H and H were l o c a t e d on t h i s a r e a , which was logged i n the s p r i n g of 1976. Ground v e g e t a t i o n was very sparse amid the s l a s h . Both g r i d s were on r e l a t i v e l y f l a t t e r r a i n . T r a p l i n e s f o r monitoring chipmunk p o p u l a t i o n s were l o c a t e d along the boundary of the f o r e s t and c l e a r c u t h a b i t a t s a t the Burn and S l a s h study areas (Figure 1.2). 7 CHAPTER 1 DEMOGRAPHY OF POPULATIONS OF DEEB MICE IN FOBIST AND CLEABCUT (LOGGED) HAEITATS INTRODUCTION The e f f e c t s on p o p u l a t i o n s of s m a l l mammals by removal of the f o r e s t c over have been w e l l documented i n North America d u r i n g the l a s t 30 years. Regeneration o f these c u t o v e r f o r e s t lands has been a d v e r s e l y a f f e c t e d by d e s t r u c t i o n of the seed supply by s m a l l mammals and b i r d s . The deer mouse (Peromvscus  maniculatus), i n p a r t i c u l a r , has r e c e i v e d much a t t e n t i o n as the most important seed p r e d a t o r , at l e a s t i n the P a c i f i c Northwest. Consequently, many s t u d i e s have d e a l t with changes i n deer mouse po p u l a t i o n s and v e g e t a t i o n f o l l o w i n g l o g g i n g . Most of these s t u d i e s concluded that there i s a g r e a t e r number of deer mice on logged areas compared with adjacent f o r e s t h a b i t a t {Orr-Ewing 1950a; T e v i s 1956a, 1956b; Ahlgren 1966; Hooven 1969, 1973; Gashwiler 1959, 1970; Badvanyi 1973; and Hooven and Black 1S76). According to a review ty Bunnell and Eastman (1976), the d i v e r s i t y of seed-eating animals should be h i g h e s t s h o r t l y a f t e r removal of the o v e r s t o r y f o r e s t . The abundance of s p e c i f i c animals v a r i e s , with those r e l y i n g p r i m a r i l y on c o n i f e r seed 8 i n c r e a s i n g i n abundance with advancing stand age and those p r e f e r r i n g other seed sources from herbs and shrubs, becoming more abundant e a r l i e r . In t h e i r o p i n i o n , the deer mouse, which e x p l o i t s annual or p e r e n n i a l seeds as w e l l as c o n i f e r seeds, p r e f e r s the e a r l i e r s u c c e s s i o n a l stages of a logged area regrowing to a f o r e s t . H a r r i s (1968) and Petticrew and S a d l e i r (1974) found very l i t t l e d i f f e r e n c e i n d e n s i t y between f o r e s t and c l e a r c u t p o p u l a t i o n s of deer mice. In a d d i t i o n , P e t t i c r e w and S a d l e i r (1974) and S a d l e i r (1974) concluded from t h e i r i n t e n s i v e 3-year study t h a t p o p u l a t i o n s on r e c e n t l y - l o g g e d areas were s i m i l a r i n s u r v i v a l , r e c r u i t m e n t , and r e p r o d u c t i o n to those i n the mature f o r e s t . Few other s t u d i e s have i n t e n s i v e l y sampled deer mouse po p u l a t i o n s through s e v e r a l years to determine both seasonal and annual v a r i a t i o n s i n demography. Sampling o n l y 2 or 3 times a year, as was the case with most s t u d i e s , i s inadequate s i n c e temporary changes i n numbers may be r e f l e c t e d as d i s t i n c t d i f f e r e n c e s between the two h a b i t a t s . For example, f a l l r e c r u i t m e n t may be higher i n one h a b i t a t but d e n s i t y w i l l d e c l i n e over winter to a l e v e l comparable to that of the other h a b i t a t . P o p u l a t i o n s of deer mice f l u c t u a t e s e a s o n a l l y with low s p r i n g breeding d e n s i t i e s and high d e n s i t i e s through the f a l l and s i n t e r ( S a d l e i r 1965; Healey 1967; Fordham 1971; P e t t i c r e w and S a d l e i r 1974; F a i r b a i r n 1977; and S u l l i v a n 1977). T h e r e f o r e , the best time (with r e s p e c t to low p o p u l a t i o n s of deer mice) f o r seeding logged areas i s i n the e a r l y s p r i n g . Arnott (1973), i n h i s review o f germination and s e e d l i n g 9 e s t a b l i s h m e n t , concluded t h a t seedbed moisture and temperature c o n d i t i o n s are l i k e l y to be optimum i n the s p r i n g . The m a j o r i t y o f s t u d i e s have not determined the number of deer mice i n d i f f e r e n t h a b i t a t s d u r i n g the e a r l y s p r i n g , which presumably i s the most c r i t i c a l time f o r d i r e c t - s e e d i n g purposes. I f there are more deer mice on logged areas, then t h i s should be apparent through a l l seasons of the year and i n p a r t i c u l a r , the s p r i n g , when popul a t i o n s d e c l i n e to breeding d e n s i t i e s . The study r e p o r t e d i n t h i s chapter was designed to t e s t the widely-held hypothesis t h a t c l e a r c u t (logged) h a b i t a t s support higher d e n s i t y p o p u l a t i o n s of Peromyscus than do f o r e s t e d h a b i t a t s . I f there are no demographic d i f f e r e n c e s between these two p o p u l a t i o n s (as P e t t i c r e w and S a d l e i r 1971 and S a d l e i r 1974 c l a i m ) , then d e n s i t y , r e c r u i t m e n t , r e p r o d u c t i o n , s u r v i v a l , and growth parameters should be s i m i l a r . . MATERIALS AMD METHODS From May to November 1975, March to December 1976, March to November 1977, and March to A p r i l 1978, two 1.1-ha g r i d s were l i v e - t r a p p e d every two weeks w i t h Longworth l i v e - t r a p s . One g r i d was l o c a t e d i n the f o r e s t and another on the c l e a r c u t (Burn study a r e a ) . From A p r i l to November 1977 and March to A p r i l 1978, a t h i r d g r i d was operated at the Loon Lake study area. On each checkerboard g r i d , 49 t r a p s t a t i o n s were l o c a t e d at 15.2-m i n t e r v a l s marked by f l a g g i n g tape and s t r i n g (Figure 1.4). One-l i v e t r a p was placed w i t h i n a 2-m r a d i u s o f each s t a t i o n . Traps 10 were b a i t e d with peanut butte r and Purina l a b chow. T e r y l e n e b a t t i n g was s u p p l i e d as bedding. Traps were s e t on day 1, checked on days 2 and 3, and then l o c k e d open between t r a p p i n g p e r i o d s . ftll deer mice captured were weighed on P e s o l a s p r i n g b a l a n c e s , sexed, and ear-tagged with s e r i a l l y numbered f i n g e r l i n g f i s h t a g s . Information on breeding performance was noted by p a l p a t i o n o f male t e s t e s and n o t i n g the c o n d i t i o n of v a g i n a l openings and mammaries of the females. Population parameters were determined by enumeration technigues to a v o i d the s t a t i s t i c a l assumptions c f random sampling. H i l b o r n e t a l . '(1976) demonstrated by a s i m u l a t i o n model t h a t enumeration techniques provide s u f f i c i e n t l y a c c c r a t e e s t i m a t e s f o r a t r a p p i n g design i n which 80% or more of the animals are caught each sampling time. Age c l a s s e s of animals were determined by body weight. J u v e n i l e s were 0-12 g i n weight; s u b a d u l t s 13-16 g; and a d u l t s >17 g. Two age c l a s s e s of deer mice have been used by S a d l e i r (1965), B r i t t e n (1966), Healey (1967), and Fordham (1971): j u v e n i l e s and a d u l t s . I r e f e r to these two age c l a s s e s of a d u l t s and j u v e n i l e s (animals i n j u v e n i l e and subadult age c l a s s e s pooled together) throughout the r e s u l t s and d i s c u s s i o n . J u v e n i l e s are c o n s i d e r e d to be young animals r e c r u i t e d d u r i n g the breeding season. In the a p p r o p r i a t e f i g u r e s and t a b l e s , each of the g r i d s i s designated by a l e t t e r : f o r e s t - A; c l e a r c u t (Burn) - B; c l e a r c u t (loon Lake) - C. The data a n a l y s i s i n t h i s study i s complicated by the same 11 animals being captured i n s e v e r a l sampling p e r i o d s . Consequently, c h i - s g u a r e analyses have been u t i l i z e d f o r data i n which the samples are not completely independent. Examples are the p r o p o r t i o n of animals i n breeding c o n d i t i o n , s u r v i v a l r a t e s , and sex r a t i o s . For t h i s reason, the t e s t s may not be s t a t i s t i c a l l y v a l i d but are used as an i n d i c a t i o n of the degree of d i f f e r e n c e between s e t s of data. Chi-square a n a l y s e s were used to t e s t f o r d i f f e r e n c e s i n v a r i o u s demographic a t t r i b u t e s between these p o p u l a t i o n s of deer mice i n f o r e s t and c l e a r c u t ha b i t a t s -BESULTS Trappa f c i l ty The demographic a n a l y s i s o f these f o r e s t and c l e a r c u t p o p u l a t i o n s i s based on the assumption that most of the i n d i v i d u a l s i n a given p o p u l a t i o n are captured. Maximum t r a p p a b i l i t y has been d e f i n e d by Krebs e t a l . <1976) as f o l l o w s : t r a p p a b i l i t y = Ho. a c t u a l l y caught at time i / No. known to be present a t time i T h i s method i n c l u d e s a l l captures and t h e r e f o r e , tends to bias upwards the t r a p p a b i l i t y estimate. Minimum unweighted t r a p p a b i l i t y i s a l e s s b i a s e d estimate s i n c e i t e l i m i n a t e s f i r s t 12 and l a s t c aptures and hence a l l mice caught only once or twice. T h i s estimate of t r a p p a b i l i t y p r o v i d e s only one value f o r each i n d i v i d u a l r e g a r d l e s s of how long i t l i v e s and so i s not i n f l u e n c e d by animals with long capture h i s t o r i e s . Both of these e s t i m a t e s f o r the three p o p u l a t i o n s i n each year are given i n T a b l e 1.1. As expected i n most cases, maximum t r a p p a b i l i t y was higher and was always above 70%. In the f o r e s t , minimum unweighted t r a p p a b i l i t y was above 75% i n a l l t h r e e y e a r s . For deer mice on the c l e a r c u t study a r e a s , t h i s estimate of t r a p p a b i l i t y was always above 70%. There was very l i t t l e d i f f e r e n c e between males and females i n the f o r e s t or c l e a r c u t p o p u l a t i o n s . P o p u l a t i o n d e n s i t y and recruitment The p o p u l a t i o n changes f o r the three study areas were s i m i l a r but not i d e n t i c a l and so w i l l be d i s c u s s e d s e p a r a t e l y . The d e n s i t y of the f o r e s t p o p u l a t i o n i s shown i n F i g u r e 1.5. The 1975 breeding season commenced at the s t a r t of the study with the p o p u l a t i o n c o n s i s t i n g of 16 to 20 animals during the f i r s t f o u r months. Density i n c r e a s e d t o 23 irice at the end of breeding. The number of r e c r u i t s averaged 1 .0 male and 0.9 female per t r a p p i n g week of breeding season during 1975. Host recruitment occurred during the breeding season, which l a s t e d u n t i l l a t e October. The p o p u l a t i o n d e c l i n e d overwinter to 16 mice and then down to 8 animals as breeding con meneed i n 1976. Numbers were s t a b l e a t 14 animals during b r e e d i n g . The number of r e c r u i t s averaged 1.1 males and 1.1 females per t r a p p i n g week of breeding season. In September, breeding ceased and there was the t y p i c a l autumn i n c r e a s e i n j u v e n i l e recruitment i n t o the 13 p o p u l a t i o n . Density again d e c l i n e d overwinter to 14 animals i n March 1977. Breeding began i n A p r i l and the d e n s i t y i n c r e a s e d to 32 animals i n June. The number of mice d e c l i n e d as breeding ceased i n September. The number o f r e c r u i t s averaged 2.2 males and 1.2 females per t r a p p i n g week of breeding season. Most rec r u i t m e n t o c c u r r e d d u r i n g the time of breeding, and the t y p i c a l f a l l i n c r e a s e i n d e n s i t y was l e s s dramatic than i n 1976. Pop u l a t i o n changes on the Burn g r i d are a l s o i l l u s t r a t e d i n Fi g u r e 1.5. The breeding season commenced a t the s t a r t of t h i s study i n 1975. Density was s t a b l e at 14 deer mice and then i n c r e a s e d t o 35 towards the end of breeding. The number of r e c r u i t s averaged 3.2 males and 2.0 females per t r a p p i n g week of breeding season. There was some a d d i t i o n a l r e c r u i t m e n t during the f a l l and then the number of animals d e c l i n e d over the winter of 1975-76 to 17 mice. D e n s i t y d e c l i n e d a f t e r breeding s t a r t e d i n 1976 and was s t a b l e during the r e s t of the r e p r o d u c t i v e p e r i o d . R e c r u i t s averaged 1.6 males and 0.9 female per t r a p p i n g week of breeding season. There was the t y p i c a l i n c r e a s e i n j u v e n i l e recruitment i n t o the p o p u l a t i o n i n September 1976. The number of mice d e c l i n e d t o 16 i n December 1976 but i n c r e a s e d to 20 i n the s p r i n g o f 1977. Density i n c r e a s e d d u r i n g the f i r s t h a l f of the breeding season as new mice r e c r u i t e d i n t o the p o p u l a t i o n . The average number of r e c r u i t s was 1.9 males and 1.8 females per t r a p p i n g week of breeding season. There was a f a l l i n c r e a s e i n j u v e n i l e recruitment which reached a peak at 44 animals. Density d e c l i n e d overwinter to 18 animals i n March 1978. The p o p u l a t i o n f o r the Loon Lake c l e a r c u t i n 1977 i s shown 14 i n F i g u r e 1.6. Breeding began i n e a r l y May with d e n s i t y i n c r e a s i n g t o a peak of 25 mice i n l a t e J u l y . The average number of r e c r u i t s was 2.6 males and 1.9 females per t r a p p i n g week of breeding season. The l a c k of a f a l l i n c r e a s e i n numbers was s i m i l a r to t h a t of the f o r e s t and Burn p o p u l a t i o n s i n 1975 and 1977 as recruitment occurred throughout the time of breeding. Density d e c l i n e d overwinter t o 16 asimals i n March 1978. The average d e n s i t y of mice per h e c t a r e was 19.6 i n the f o r e s t and 23.3 on the Burn i n 1975; 15.8 i n the f o r e s t and 16.6 on the Burn i n 1976; and 22-3 i n the f o r e s t , 29.9 on the Burn, and 20-2 a t Loon Lake i n 1977. Thus, t h e r e was very l i t t l e d i f f e r e n c e i n the d e n s i t y of deer mice between f o r e s t and c l e a r c u t h a b i t a t s d u r i n g the t h r e e years of t h i s study. The s l i g h t l y higher number of animals on the Burn i n 1975 and 1977 r e f l e c t e d the b u r s t o f recruitment onto the c l e a r c u t area i n the l a t e summer and f a l l of each year^ Beproduction The best v a r i a b l e to use f o r determining the breeding a c t i v i t y of a p o p u l a t i o n i s probably the percentage of l a c t a t i n g f e s a l e s (Krebs e t a l . 1969). T h i s measure underestimates the s t a r t o f a c t i v e breeding by the l e n g t h of the g e s t a t i o n p e r i o d , which i s about t h r e e weeks. Percentage of females with medium to l a r g e n i p p l e s and percentage of males with s c r o t a l t e s t e s have been used t o determine the l e n g t h of the breeding season f o r my three p o p u l a t i o n s . In the f o r e s t , the l e n g t h of the breeding seasons were: 1915 - 23 veeks; 1976 - 16 weeks; 1977 - 22 weeks. On the Eurn, 15 the d u r a t i o n of the breeding seasons were: 1975 - 13 weeks; 1976 - 16 weeks; 1977 - 20 weeks. At the Loon Lake c l e a r c u t , breeding i n 1977 l a s t e d f o r 15 weeks. Thus, the breeding seasons of mice l i v i n g i n the f o r e s t were at l e a s t the same l e n g t h , or l o n g e r than those of animals at the Burn study area (and Loon Lake i n 1 9 7 7 ) . Table 1.2 g i v e s two measures of breeding performance f o r the three p o p u l a t i o n s d u r i n g t h e i r r e s p e c t i v e breeding seasons. The p o p u l a t i o n o f deer mice at Loon Lake has been compared with the 1975 p o p u l a t i o n s i n the f o r e s t and Burn. T h i s allowed comparison of the two c l e a r c u t p o p u l a t i o n s a t the s i m i l a r time i n t e r v a l of one year a f t e r l o g g i n g or burning of the study area. Looking f i r s t at v a r i a t i o n between h a b i t a t s , we see no s i g n i f i c a n t d i f f e r e n c e s i n p r o p o r t i o n of a d u l t males i n breeding c o n d i t i o n during any of the years i n t h i s study. However, t h e r e were more j u v e n i l e males breeding during 1976 on the Burn compared with the f o r e s t . In 1977 , a d i f f e r e n c e i n j u v e n i l e male breeding was s t a t i s t i c a l l y s i g n i f i c a n t when the two c l e a r c u t p o p u l a t i o n s were compared. There was a s i g n i f i c a n t l y g r e a t e r p r o p o r t i o n of a d u l t females l a c t a t i n g on the Burn compared with that i n the f o r e s t p o p u l a t i o n i n 1975 and 1976. T h i s t r e n d continued i n 1977 but was not s t a t i s t i c a l l y s i g n i f i c a n t . There was no d i f f e r e n c e i n p r o p o r t i o n of breeding j u v e n i l e females between areas. I f we compare breeding performance between years f o r the f o r e s t p o p u l a t i o n we see a s i g n i f i c a n t l y higher percentage of a d u l t males i n breeding c o n d i t i o n i n 1976 than i n e i t h e r 1975 or 1 9 7 7 . There was l i t t l e v a r i a t i o n i n j u v e n i l e male breeding 16 performance between years. The Burn p o p u l a t i o n had the h i g h e s t p r o p o r t i o n of a d u l t and j u v e n i l e males with s c r o t a l t e s t e s i n 1976 compared with t h a t i n 197 5 or 1977. The p r o p o r t i o n of l a c t a t i n g a d u l t females i n the f o r e s t was s i g n i f i c a n t l y g r e a t e r i n 1975 compared with that i n 1976. T h i s p r o p o r t i o n was a l s o higher i n 1977 but was not s t a t i s t i c a l l y d i f f e r e n t from t h a t i n 1976. There was not a s i g n i f i c a n t d i f f e r e n c e i n percentage of breeding j u v e n i l e females i n the f o r e s t d u r i n g the years of t h i s study. S i m i l a r l y , there was l i t t l e annual v a r i a t i o n i n p r o p o r t i o n of a d u l t and j u v e n i l e females on the Burn. In summary, there were more males i n b r e e d i n g c o n d i t i o n on the Burn than i n the f o r e s t i n 1975 but about the same number i n both h a b i t a t s i n 1976-77. More females were breeding on the Burn i n a l l years than i n the f o r e s t s The g r e a t e s t p r o p o r t i o n of animals breeding was i n 1S76 f o r males and 1975 f o r females i n both h a b i t a t s . M o r t a l i t y M o r t a l i t y i n t h i s study i s r e p r e s e n t e d by disappearance from the t r a p p a b l e p o p u l a t i o n , and so i n c l u d e s e m i g r a t i o n . Temporal changes i n s u r v i v a l r a t e s are measured by d i r e c t enumeration, and i n c l u d e s u r v i v a l i n the t r a p p a b l e p o p u l a t i o n and e a r l y j u v e n i l e s u r v i v a l . Minimum s u r v i v a l r a t e s f o r a l l males and females i n the three p o p u l a t i o n s f o r breeding (summer) and non-breeding (winter) seasons are given i n Table 1.3. These average r a t e s are summed over a season with an i n d i v i d u a l mouse being t a l l i e d each time i t i s trapped. There were no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e s i n s u r v i v a l between h a b i t a t s f o r both 17 males and females- In g e n e r a l , deer mice s u r v i v e d s l i g h t l y b e t t e r i n the f o r e s t than on the Burn during the summers of 1975 and 1976 but t h i s d i f f e r e n c e was r e v e r s e d i n 1977- Hale mice i n the f o r e s t s u r v i v e d b e t t e r than t h e i r c o u n t e r p a r t s on the Burn duri n g the winters of 1976-77 and 1977-78 but t h i s was reversed i n the winter of 1975-76- T o t a l s u r v i v a l of females d u r i n g the winters of 1975-76 and 1976-77 was n e a r l y i d e n t i c a l - However, females on the Burn s u r v i v e d b e t t e r than those i n the f o r e s t d u r i n g the winter of 1977-78-The f o r e s t p o p u l a t i o n of male deer n i c e s u r v i v e d much b e t t e r i n summer 1975 than i n 1976-, S u r v i v a l appeared hi g h e r i n 1977 compared with t h a t i n the p r e v i o u s y e a r , but t h i s d i f f e r e n c e was not s t a t i s t i c a l l y s i g n i f i c a n t . T h i s t r e n d was s i m i l a r f o r males on the Burn. The only s i g n i f i c a n t d i f f e r e n c e s i n winter s u r v i v a l were i n the f o r e s t i n 1975-76 when 6Q% of males s u r v i v e d compared with 87% i n 1976-77 and 65% i n 1977-78. T h i s trend i n winter s u r v i v a l was s i m i l a r f o r females with a s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e between the w i n t e r s of 1975-76 and 1976-77 on the Burn. There was very l i t t l e v a r i a t i o n i n female s u r v i v a l on the Burn during the three summers. In the f o r e s t , female deer mice s u r v i v e d b e t t e r i n 1975 and 1976 than i n the f i n a l year and t h i s d i f f e r e n c e was s t a t i s t i c a l l y s i g n i f i c a n t between 1975 and 1977. E a r l y j u v e n i l e s u r v i v a l may be measured by an index r e l a t i n g r e c r u i t m e n t of young i n t o the t r a p p a b l e p o p u l a t i o n to the number of p o s s i b l y l a c t a t i n g females (Krebs 1966): index= NO. s t t a l l mice i n week t / Uo. females with medium to l a r g e 18 n i p p l e s caught i n week t-4 Small mice were d e f i n e d as those l e s s than 17 g. Sable 1-4 g i v e s the mean i n d i c e s f o r the three p o p u l a t i o n s d u r i n g the breeding season and up to t h e end of r e c r u i t m e n t of young- In the breeding season of 1975, e a r l y j u v e n i l e s u r v i v a l on the Burn was 3-5 times higher than that of the f o r e s t . I f we compare the Loon Lake data o f 1977 with those of the f o r e s t and Burn (1975), we f i n d s u r v i v a l was more than twice that o f f o r e s t deer mice and a l i t t l e more than one-half that of the Burn p o p u l a t i o n . With the a d d i t i o n of r e c r u i t m e n t a f t e r the breeding season, the i n d i c e s of s u r v i v a l changed very l i t t l e on the three study a r e a s . In 1976, the index of e a r l y j u v e n i l e s u r v i v a l was s l i g h t l y higher i n the f o r e s t a t 1.14 compared with 0.86 f o r the Burn deer mice. Recruitment at the end of breeding i n c r e a s e d the index to 1.07 on the Burn, but the f o r e s t index was unchanged. More j u v e n i l e s entered the p o p u l a t i o n a f t e r breeding on the Burn compared with the f o r e s t p o p u l a t i o n (see F i g u r e 1-5). I n 1977, j u v e n i l e s i n the f o r e s t p o p u l a t i o n s u r v i v e d b e t t e r than those of e i t h e r p o p u l a t i o n on the Burn or a t Loon Lake. Both the f o r e s t and Burn p o p u l a t i o n s gained j u v e n i l e s a f t e r the breeding season. The number of s u c c e s s f u l pregnancies during the breeding season and expected and observed number of j u v e n i l e s which were r e c r u i t e d i n t o each p o p u l a t i o n up to one month a f t e r breeding are l i s t e d i n Table 1-5. ft pregnancy was c o n s i d e r e d s u c c e s s f u l i f the female was l a c t a t i n g during the p e r i o d f o l l o w i n g the estimated time of b i r t h of a l i t t e r . The f o r e s t p o p u l a t i o n had 19 a g r e a t e r number of s u c c e s s f u l pregnancies i n 1975 but a very poor recruitment of j u v e n i l e s compared with t h a t on the Burn. In 1976 and 1977, the f o r e s t had a lower number of s u c c e s s f u l pregnancies but a higher p r o p o r t i o n of r e c r u i t s e n t e r i n g the p o p u l a t i o n than on the Burn, and Loon Lake i n 1977. For animals which were r e c r u i t e d i n t o p o p u l a t i o n s up to one month before the end of breeding, t h e r e was very l i t t l e d i f f e r e n c e between h a b i t a t s . S i m i l a r l y , there was l i t t l e v a r i a t i o n between h a b i t a t s with r e s p e c t to the p r o p o r t i o n of r e c r u i t s s u r v i v i n g and becoming r e p r o d u c t i v e during the breeding season of a given y e a r . the Burn p o p u l a t i o n i n 1976 had 4 males and 3 females s u r v i v i n g to breed as young of the year compared with the f o r e s t p o p u l a t i o n which had no males and 1 female s u r v i v i n g to reproduce. T h i s d i f f e r e n c e was not s i g n i f i c a n t because of s m a l l sample s i z e s . I f we compare v a r i a t i o n between y e a r s , 1976 l a s the poorest year f o r j u v e n i l e males s u r v i v i n g d u r i n g the breeding season. Of j u v e n i l e animals which s u r v i v e d and bred before the end of b r e e d i n g , 1977 was the poorest year f o r a l l 3 study areas. In summary, t o t a l male and female s u r v i v a l was higher (but not s t a t i s t i c a l l y s i g n i f i c a n t ) i n the f o r e s t p o p u l a t i o n i n the summers cf 1975-76, In summer 1977, male and female s u r v i v a l was s l i g h t l y higher f o r the Burn p o p u l a t i o n . During winter 1975-76, males s u r v i v e d b e t t e r on the Burn but t h i s was reversed i n favour cf the f o r e s t animals i n 1976-77 and 1977-78. Females from the two h a b i t a t s showed no d i f f e r e n c e i n winter s u r v i v a l i n the f i r s t two years but Burn females s u r v i v e d b e t t e r i n 1977-78 compared with those i n the f o r e s t . T o t a l s u r v i v a l through the 20 study showed very l i t t l e v a r i a t i o n between the f o r e s t and c l e a r c u t h a b i t a t s . E a r l y j u v e n i l e s u r v i v a l was h i g h e r on the Burn i n 1975 but t h i s was lower r e l a t i v e to t h a t i n the f o r e s t i n 1576-77. Growth Growth r a t e s may be used as a f u r t h e r index of c o n d i t i o n s w i t h i n p o p u l a t i o n s of Peromyscus maniculatus. The aspects of growth to be c o n s i d e r e d are sexual maturity and body weight, growth r a t e r e g r e s s e d on body weight, and average body weight d u r i n g breeding and non-breeding seasons. Age at sexual maturity i s an important demographic v a r i a b l e . Owing to the l a c k of a b e t t e r c r i t e r i o n , body weight must be used as an index of age,. The percentage of s e x u a l l y mature animals i n a s e r i e s of weight c l a s s e s may be used to determine the weight l i m i t a t i o n s f o r j u v e n i l e s , s u b a d u l t s , and a d u l t s . Hy age c l a s s e s assume j u v e n i l e s are never s e x u a l l y mature; groups of i n d i v i d u a l s of which l e s s than 50% are mature i n the upper weight c l a s s are c a l l e d s u b a d u l t s ; and a d u l t s must have at l e a s t 503* of mice s e x u a l l y mature in the lowest weight c l a s s . Using these c r i t e r i a , I e s t i m a t e d the weight l i m i t s f o r age c l a s s e s i n a s i m i l a r manner d e s c r i b e d i n a previous study ( S u l l i v a n 1977). In t h i s study, j u v e n i l e s were 0-12g i n weight; sub a d u l t s 13-16g; and a d u l t s > 17g. The mean weights of male and female deer mice are i l l u s t r a t e d i n F i g u r e 1.7. Female body weights are complicated by undetected pregnancies but are presented here f o r comparison of animals i n the two h a b i t a t s . None of the i n d i v i d u a l means i s s i g n i f i c a n t l y d i f f e r e n t because of the broad c o n f i d e n c e 21 i n t e r v a l s - Male deer mice i n the f o r e s t , cn the average, weighed up to one gram more than t h e i r c l e a r c u t c o u n t e r p a r t s d u r i n g the summers of 1975 and 1976. T h e i r weights were s i m i l a r i n the summer of 1977 but showed c o n s i s t e n t d i f f e r e n c e s d u r i n g the w i n t e r s . S i m i l a r l y , female f o r e s t mice were heavier during each summer compared with animals on the Burn. However, females on the Burn weighed more i n the winters of 1975-76 and 1977-78 and at Loon Lake i n 1977-78. In a l l c a s e s , deer mice were he a v i e r i n the summer than i n the winter of each year. Loon Lake males were an e x c e p t i o n to t h i s t r e n d . To show t h a t growth c o n d i t i o n s f o r animals d i f f e r between h a b i t a t s , t h e r e must be v a r i a t i o n i n growth r a t e s . Since growth r a t e i s dependent on body weight, r e g r e s s i o n s f o r these v a r i a b l e s may be compared between study areas. An a n a l y s i s of c o v a r i a n c e was done f o r growth r a t e regressed cn body weight of animals l e s s than 18g f o r the breeding season and subseguent pe r i o d of r e c r u i t m e n t each year. Males and females had s i m i l a r growth r a t e s and have been combined f o r each of the f o r e s t and Burn p o p u l a t i o n s . There were no s i g n i f i c a n t d i f f e r e n c e s i n growth r a t e between the Burn and f o r e s t p o p u l a t i o n s d u r i n g the t h r e e years of t h i s study. I t i s b i o l o g i c a l l y s i g n i f i c a n t , however, t h a t f o r e s t mice grew s l i g h t l y f a s t e r than t h e i r Burn c o u n t e r p a r t s i n 1975, twice as f a s t i n 1976 and 3 times as f a s t i n 1977. There was a h i g h l y s i g n i f i c a n t (p<.01) d i f f e r e n c e between 1975 and 1976 and between 1975 and 1977 as the growth r a t e of Burn animals d e c l i n e d . The growth r a t e s of i n d i v i d u a l s comprising the f o r e s t p o p u l a t i o n should be h i g h e r than those on the logged area, and 22 t h i s d i f f e r e n c e should be accentuated as the c l e a r c u t advances i n age. Mean growth r a t e s (adjusted to 13-g animals) and 95% confidence l i m i t s f o r males and females are shown i n F i g u r e 1.8. As p r e v i o u s l y d i s c u s s e d , growth r a t e s of f o r e s t mice were always higher than those from the Burn except f o r females i n 1975. Growth r a t e s d e c l i n e d i n both h a b i t a t s during 1976, remained at the same l e v e l on the Burn and i n c r e a s e d i n the f o r e s t i n 1S77 f o r both sexes. The males at Loon Lake i n 1977 grew f a s t e r than females, but t h e i r combined r a t e of growth was much lower than t h a t of the Burn mice i n 1975 (a s i m i l a r i n t e r v a l of one year a f t e r l o g g i n g ) . Age a t s e x u a l m a t u r i t y i s a u s e f u l v a r i a b l e f o r determining i f mice are maturing at the same age i n d i f f e r e n t a reas. The weight a t sexual maturity f o r l i v e - t r a p p e d mice was estimated i n the same manner as d e s c r i b e d f o r v o l e s by Krebs e t a l . (1S76). F i g u r e 1.9 p r e s e n t s these data f o r males and females d u r i n g the p e r i o d June to August of each year i n the study. There was very l i t t l e d i f f e r e n c e i n body weight o f deer mice a t s e x u a l raatcrity i n f o r e s t and Burn h a b i t a t s - In 1976, the data comparing f o r e s t and Burn animals are somewhat misleading because of very low sample s i z e s on the Burn. I f we compare d i f f e r e n t y e a r s , deer mice i n both h a b i t a t s i n 1975 and 1976 matured at weights up to 2 grams l i g h t e r than i n 1977. In summary, animals i n the f o r e s t were c o n s i s t e n t l y h e a v i e r than Bice on the c l e a r c u t , although t h i s v a r i a t i o n was not s t a t i s t i c a l l y s i g n i f i c a n t . F o r e s t mice grew 3 times f a s t e r than t h e i r Burn c o u n t e r p a r t s i n 1976 and 2 times f a s t e r i n 1977, a f t e r showing l i t t l e d i f f e r e n c e i n 1975. Deer mice i n the 23 f o r e s t and Burn p o p u l a t i o n s tended to mature at s i m i l a r weights. Sex r a t i o s The sex r a t i o s of the three p o p u l a t i o n s have been estimated from the minimum number of animals known to be a l i v e , and these data have been summed f o r each year o f the study. Table 1.6 g i v e s the p r o p o r t i o n of males and s t a t i s t i c a l comparisons f o r each p o p u l a t i o n . The Burn p o p u l a t i o n had a s i g n i f i c a n t l y higher number of males i n 1975 compared with the f o r e s t . There tas a s i m i l a r number of males and females i n both h a b i t a t s i n 1976. In 1977, the f o r e s t and lo o n Lake p o p u l a t i o n s had a s i g n i f i c a n t l y g r e a t e r p r o p o r t i o n of males r e l a t i v e to the Burn. T h i s p r o p o r t i o n f o r Loon Lake (0.61) was s i m i l a r to t h a t of the Burn (0.67) i n 1975, and was s i g n i f i c a n t l y higher than t h a t of the f o r e s t (0.50) i n 1975. Thus, f o r t h e i r f i r s t year of s u c c e s s i o n a f t e r l o g g i n g , both the Burn and Loon Lake p o p u l a t i o n s had a gre a t e r p r o p o r t i o n of males (>0.60), and t h i s d i f f e r e n c e was s t a t i s t i c a l l y s i g n i f i c a n t when the Burn p o p u l a t i o n was compared with that of the f o r e s t i n 1975. DISCUSSION In t h i s study, the demographic a t t r i b u t e s of deer mice have been compared between f o r e s t and c l e a r c u t (logged) h a b i t a t s . I n f o r m a t i o n was o b t a i n e d at biweekly i n t e r v a l s throughout most of the snow-free p e r i o d s of 1975 to the s p r i n g of 1978. There were very few d i f f e r e n c e s i n t h e parameters of d e n s i t y , r e c r u i t m e n t , r e p r o d u c t i o n , s u r v i v a l , and growth between f o r e s t 24 and c l e a r c u t p o p u l a t i o n s . There were however, seasonal f l u c t u a t i o n s i n numbers of mice, p a r t i c u l a r l y on the c l e a r c u t . Few other s t u d i e s have been as i n t e n s i v e , s i n c e most workers have r e l i e d upon annual censuses i n the e a r l y summer and f a l l to compare d e n s i t i e s i n the two h a b i t a t s . These l a t t e r s t u d i e s have concluded t h a t t h e r e are 2 t o 3 times more deer mice on c l e a r c u t areas than i n f o r e s t (Gashwiler 1959, 1970; Ahlgren 1966; K r e f t i n g and Ahlgren 1974; and M a r t e l l and Badvanyi 1977a). S i m i l a r r e s u l t s were ob t a i n e d by Orr-Ewing (1950a) t r a p p i n g f o r one n i g h t every month, f o r 12 months, i n d i f f e r e n t a r e a s . T r o u s d e l l (1954), a f t e r t r a p p i n g d u r i n g 3 winter months, concluded t h a t the number of deer mice was ten times higher on c l e a r c u t s compared with mature f o r e s t of l o b l o l l y p i n e . T e v i s (1956a) found 3 to 4 times the number of mice on logged areas f o l l o w i n g s i x months t r a p p i n g i n s e v e r a l d i f f e r e n t aged c l e a r c u t s . Hooven (1969, 1973) and Hooven and Black (1976) trapped at more fr e g u e n t i n t e r v a l s (1 to 3 months) over s e v e r a l years and concluded t h a t there were from 2 t o 10 times more deer mice i n cutover f o r e s t h a b i t a t s compared with unlogged s i t e s . T e v i s (1956b), Lawrence (1966), Sims and Buckner (1973), and K r e f t i n g and Ahlgren (1974) came t o the s i m i l a r c o n c l u s i o n of a g r e a t e r number (2 to 10 times) o f mice on burnt c l e a r c u t s compared with the f o r e s t . H a r r i s (1968) i n Alaska, u s i n g annual censuses i n the e a r l y summer and f a l l , concluded t h a t a g r e a t e r number of mice e x i s t s i n the f o r e s t . K r u l l (1970) concluded from annual summer censuses i n northern hardwood f o r e s t t h at there were s l i g h t l y more, but not s t a t i s t i c a l l y s i g n i f i c a n t l y more, s h i t e - f o o t e d 25 mice (Peromyscus sj>.) i n f o r e s t areas than i n c l e a r c u t h a b i t a t . In a s i m i l a r f o r e s t type, l o v e j o y (1975) trapped at bimonthly i n t e r v a l s over 18 months and found l i t t l e d i f f e r e n c e i n numbers of deer mice between f o r e s t e d and r e c e n t l y - l o g g e d h a b i t a t s . P e t t i c r e w and S a d l e i r {1911*) a l s o came to t h i s c o n c l u s i o n i n t h e i r 3-year p r o j e c t with i n t e n s i v e sampling a t monthly i n t e r v a l s . I f sampling was conducted during June and October i n the data presented i n t h i s paper and those given by P e t t i c r e w and S a d l e i r (1974) , what c o n c l u s i o n s would be drawn when the d e n s i t i e s i n the two h a b i t a t s are compared? T h i s comparison i s shewn i n Table 1.7. I t i s obvious that t h e r e appear to be approximately 40% more animals on logged areas than i n the f o r e s t , p a r t i c u l a r l y i n the censuses f o r October of each year. T h i s i s r e f l e c t e d by the f l u c t u a t i n g p o p u l a t i o n on the Burn, with the g r e a t e s t i n c r e a s e i n number of mice o c c u r r i n g i n the f a l l . S i m i l a r l y , t here were g r e a t e r f l u c t u a t i o n s i n d e n s i t y and hence, r e c r u i t m e n t , i n the study by Petticrew and S a d l e i r (1574). Recruitment i n my study was higher on the Burn (2.08 males and 1,54 females per t r a p p i n g week of breeding seasons) than i n the f o r e s t (1.47 males and 1.06 females per t r a p p i n g week of breeding s e a s o n s ) . The d e n s i t y c f mice on the Burn returned each s p r i n g t o a l e v e l comparable to t h a t of the f o r e s t . T h i s i n d i c a t e s t h a t the m o r t a l i t y and/or e s d g r a t i o n r a t e s of P. manicnlatus must be higher on the Burn than i n the f o r e s t . I f t h e s i z e and growth of mice was g r e a t e r i n the f o r e s t , then i s t h i s h a b i t a t a b e t t e r area f o r deer Bice than i n a logged c l e a r c u t ? I s i t p o s s i b l e t h a t the c l e a r c u t i s l e s s 26 d e s i r a b l e h a b i t a t i n terms of food, cover, and v u l n e r a b i l i t y t o p r e d a t i o n such t h a t s u bordinate animals are , i n f a c t , d r i v e n out of the f o r e s t onto the c l e a r c u t ? I f t h i s i s the case, then r e c e n t l y - l o g g e d areas may be a c t i n g as d i s p e r s a l s i n k s ( L i d i c k e r 1975) or i n terms of a g g r e s s i v e i n t e r a c t i o n s between i n d i v i d u a l s , b e h a v i o u r a l s i n k s . F o r e s t p o p u l a t i o n s of deer mice i n southern B r i t i s h Columbia f l u c t u a t e s e a s o n a l l y , with low s p r i n g breeding d e n s i t i e s and high d e n s i t i e s through the f a l l and winter. During the breeding season, re c r u i t m e n t i s low, with few j u v e n i l e s s u r v i v i n g to t r a p p a b l e age; I t i s c u r r e n t l y thought that seasonal changes i n the s u r v i v a l of j u v e n i l e mice are determined by seasonal changes i n the a g g r e s s i v e n e s s of the a d u l t p o p u l a t i o n ( S a d l e i r 1965; Healey 1S67; Fordham 1971; Petticrew and S a d l e i r 1974; F a i r b a i r n 1977; and S u l l i v a n 1977). Some female j u v e n i l e s may be t o l e r a t e d , p a r t i c u l a r l y immigrants, i f they a t t a i n s e x u a l maturity ( P e t t i c r e w and S a d l e i r 1S74). Experimental evidence from the c o l o n i z a t i o n of vacant h a b i t a t (removal areas) by deer mice has shown t h a t j u v e n i l e s w i l l c o l o n i z e these open areas s u c c e s s f u l l y ( S a d l e i r 1965; Healey 1967; S u l l i v a n 1977; and F a i r b a i r n 1978). There was a s i g n i f i c a n t l y higher p r o p o r t i o n of j u v e n i l e r e c r u i t s i n the Burn p o p u l a t i o n d u r i n g the breeding season i n 1975 (92-3% of t o t a l r e c r u i t s ) and Loon Lake p o p u l a t i o n i n 1977 (70.9% - not s t a t i s t i c a l l y s i g n i f i c a n t ) than i n the f o r e s t (60.9% of t o t a l r e c r u i t s ) ( F i g u r e s 1.5 and 1.6). In 1976 and 1977, there was l i t t l e d i f f e r e n c e between the two h a b i t a t s with r e s p e c t to p r o p o r t i o n of j u v e n i l e r e c r u i t s . T h i s t r e n d i s a l s o 27 r e f l e c t e d by the index of e a r l y j u v e n i l e s u r v i v a l , which was f o u r times h i g h e r on the Burn i n 1975 than i n the f o r e s t . Again i n 1S76 and 1977, there was much l e s s of a d i f f e r e n c e i n t h i s index of s u r v i v a l between the two areas. The annual v a r i a t i o n i n demography f o r f o r e s t and c l e a r c u t p o p u l a t i o n s o f deer mice i s summarized i n Table 1.8-Demographically, the years of 1975 and 1977 were g u i t e s i m i l a r to each o t h e r and they i n t u r n , d i f f e r e d from 1976 i n both h a b i t a t s - T h i s d i f f e r e n c e was most e v i d e n t i n average d e n s i t y of animals and number of r e c r u i t s (at l e a s t on the Burn). B i t h r e s p e c t to the onset of breeding, the p o p u l a t i o n s i n both h a b i t a t s d e c l i n e d i n d e n s i t y during the s p r i n g of 1976, but t h i s phencnencn was not e v i d e n t i n e i t h e r 1975 or 1977. F a i r f c a i r n (1977) has d i s c u s s e d the s p r i n g d e c l i n e i n deer mice, which u s u a l l y occurs a t the s t a r t of the breeding season and i n c l u d e s d e c l i n i n g numbers of males as w e l l as females. The low summer s u r v i v a l r a t e s o f males and the poorer growth r a t e s of animals i n 1976 may be a r e s u l t of there being a g r e a t e r p r o p o r t i o n of male deer mice i n breeding c o n d i t i o n . T h i s c o u l d produce a much more t i g h t l y r e g u l a t e d p o p u l a t i o n with r e s p e c t t o poor j u v e n i l e r e c r u i t m e n t d u r i n g the breeding season which r e s u l t s i n the t y p i c a l autumn i n c r e a s e i n d e n s i t y . The l e n g t h of the 1976 breeding season f o r the f o r e s t and Burn p o p u l a t i o n s (16 weeks) was much s h o r t e r than that of the Burn p o p u l a t i o n i n 1977 as well as the r e p r o d u c t i v e p e r i o d s o f the f o r e s t p o p u l a t i o n i n 1975 and 1977- These longer breeding seasons may r e s u l t i n g r e a t e r recruitment of deer mice before the end of breeding and thereby i n c r e a s e d the f a l l d e n s i t y to a higher l e v e l compared 28 with years with s h o r t e r breeding seasons. The f i r s t year a f t e r l o g g i n g and burning of the Burn study area was 1975 and the f i r s t year a f t e r l o g g i n g a t Loon Lake was 1977. Both these areas had a s i g n i f i c a n t l y h i g h e r p r o p o r t i o n of males i n t h e i r f i r s t year of s u c c e s s i o n compared s i t h the f o r e s t . T h i s r e f l e c t s a g r e a t e r number o f male j u v e n i l e s i n the r e c r u i t s e n t e r i n g the p o p u l a t i o n during the breeding season. The f o r e s t p o p u l a t i o n i n 1975 r e c r u i t e d 8 males:6 females compared with the Burn j u v e n i l e sex r a t i o of 16:8 and Loon Lake (1977) of 13:9- Thus, j u v e n i l e male deer mice were able to e n t e r i n t o the c l e a r c u t p o p u l a t i o n s d u r i n g the f i r s t breeding season f o l l o w i n g l o g g i n g - T h i s provides some evidence t h a t e i t h e r a d u l t - j u v e n i l e b e h a v i o u r a l i n t e r a c t i o n s are l e s s p r e v a l e n t because the c l e a r c u t i s a poorer h a b i t a t with mainly subordinate mice, or a l t e r n a t i v e l y , t h a t t h i s h a b i t a t i s s u p e r i o r i n one or more unknown re s o u r c e s (food, s h e l t e r , etc.) and can support a g r e a t e r number of animals. T h i s l a t t e r e x p l a n a t i o n i s u n l i k e l y s i n c e the d e n s i t i e s of f o r e s t and c l e a r c u t p o p u l a t i o n s have d e c l i n e d overwinter to s i m i l a r l e v e l s during the three winters of t h i s study. I f the logged h a b i t a t i s s u p e r i o r , then t h e higher f a l l d e n s i t y of mice should p e r s i s t . Very few s t u d i e s have provided i n f o r m a t i o n on the d e n s i t y of deer mice cn c l e a r c u t areas i n the e a r l y s p r i n g . For the p r a c t i c a l purposes of r e f o r e s t a t i o n by d i r e c t - s e e d i n g , the s p r i n g i s the most important time f o r optimum seedbed moisture and temperature c o n d i t i o n s (ftrnott 1973). However, a c c o r d i n g t o a review by Waldron (1973), the m a j o r i t y of d i r e c t seeding to 29 date, in Canada, has been carried out in the autumn. S i m i l a r l y , in the northwest regions of the United States, seeding has been done mainly i n the f a l l (Carmichael 1957; Lavender 1958). I t i s not s urprising, then, that foresters have concluded there to be a greater number of mice on clearcuts, since most work has been done in the summer and f a l l . Orr-Ewing (1950a) and Hooven (1S5 6) provided data for the spring months which showed fewer mice than i n subsequent summer and f a l l months i n the habitats studied. Petticrew and Sadleir (1974) also found the lowest density to be in the spring, and t h i s was most pronounced a f t e r a long non-breeding season. According to these authors (Petticrew and Sadleir 1974), i f the non-breeding season i s long, there i s a steady decrease i n numbers as the monthly mortality operates over an increasing period of time. When breeding begins a f t e r long non-breeding seasons, the density i s so low that there should not be a spring decline.. However, in my study, the spring decline in 1976 followed the longest non-breeding season on the Burn (36 weeks). The length of the non-breeding season i n the forest prior to t h i s spring decline s»as 29 seeks- This was the same length as the 1S76-77 non-breeding period, which was not followed by a decline i n numbers at the onset of reproduction. There appears to be no rela t i o n s h i p between the length of the non-breeding season and the presence or absence of a spring decline in density in my study. Thus, the number of deer mice i s lowest and very similar i n forested and logged areas during the spring with a s p i l l - o v e r of animals in the f a l l temporarily creating a higher number on the clearcut. Consequently, a newly-logged area may not be a 30 p a r t i c u l a r l y f a v o u r a b l e h a b i t a t f o r deer mice and r e l a t e d s m a l l mammals once the i n i t i a l c o l o n i z a t i o n has occurred, as expounded by Badvanyi (1973) and Bunnell and Eastman (1S76). P o p u l a t i o n processes and trends observed i n the study o f f o r e s t p o p u l a t i o n s of deer mice should be s i m i l a r f o r p o p u l a t i o n s occupying c l e a r c u t a r e a s . T h e r e f o r e , techniques f o r c o n t r o l l i n g c o n i f e r seed p r e d a t i o n i n deer mice which are developed i n f o r e s t areas should be a p p l i c a b l e to p o p u l a t i o n s on logged r e g i o n s , p a r t i c u l a r l y i n the s p r i n g . The most impressive f i n d i n g of t h i s study i s the s i m i l a r i t y i n d e n s i t y and a s s o c i a t e d demographic a t t r i b u t e s of deer mouse po p u l a t i o n s i n f o r e s t e d and c l e a r c u t (logged) h a b i t a t s . The sp u r i o u s c o n c l u s i o n t h a t there are 2 to 10 times more deer mice cn c l e a r c u t areas than i n f o r e s t i s not supported by t h i s study nor those of P e t t i c r e w and S a d l e i r (1974) and S a d l e i r (1974), which used i n t e n s i v e sampling o f mouse p o p u l a t i o n s over s e v e r a l y e a r s . T h i s work should be f o l l o w e d up by b e h a v i o u r a l s t u d i e s of deer mice i n f o r e s t and c l e a r c u t areas t o determine whether or not r e c e n t l y - l o g g e d areas are s i n k s f o r d i s p e r s i n g subordinate animals. In a d d i t i o n , there should be i n t e n s i v e monitoring of p o p u l a t i o n s of P* maniculatus d u r i n g a l l the s e r a i stages i n the s u c c e s s i o n of a logged area to f o r e s t . 3 1 F i g u r e 1.1. L o c a t i o n o f t h e f o u r s t u d y a r e a s 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 R e s e a r c h F o r e s t , M a p l e B i d g e , B.C. U B C Research Forest Scale= , one km 33 F i g u r e 1.2. A e r i a l photograph showing the l o c a t i o n of the g r i d s and t r a p l i n e s at the Burn and S l a s h c l e a r c u t and f o r e s t study areas. S c a l e : 1:12,000. 3k 35 F i g u r e 1.3. A e r i a l photograph showing the l o c a t i o n of the g r i d s a t the Loon Lake study area. S c a l e : 1:12,000. 36 37 F i g u r e 1.4. L i v e - t r a p g r i d (1.1 ha) with 49 t r a p s t a t i o n s (one trap per s t a t i o n ) and l o c a t i o n of 36 (0.61 m x 0.61 m) seed sampling quadrats. 38 A • a • —tr— A *-• A • A • A * , • A i • k • • A • A • • A • A • k • A • • • A • • • • A t i. • A. • • A • • • • • • • • —A .— A -A— • A • — A — • A • —A A • i 1 0.61 m seed sampling quadrat 15.2 m 91.4 m A - trap s t a t i o n | | - seed sampling quadrat 39 Figure 1.5- Population d e n s i t y on f o r e s t amd Burn c l e a r c u t g r i d s d u r i n g 1975-78, Peromvscus maniculatus. Non-breeding seasons are shaded. V e r t i c a l dotted bars r e p r e s e n t s t a r t and end of breeding a c t i v i t y . S o l i d v e r t i c a l bars e n c l o s e d e f i n e d breeding seasons. Histograms i n d i c a t e number of new males (shaded) and females (unshaded) r e c r u i t e d i n t o p o p u l a t i o n . F O R E S T 4 0 -3 5 -1 9 7 5 1 9 7 6 1 9 7 7 1 9 7 8 B U R N M J S N J M M J S N J M M J S N J M 1 9 7 5 1 9 7 6 1 9 7 7 1 9 7 8 41 F i g u r e 1.6- P o p u l a t i o n d e n s i t y on Loon Lake c l e a r c u t g r i d d u r i n g 1977-78, Peromvscus maniculatus- Non-breeding season i s shaded- V e r t i c a l d o tted bars r e p r e s e n t s t a r t and end of breeding a c t i v i t y . S o l i d v e r t i c a l bars e n c l o s e d e f i n e d breeding season. Histograms i n d i c a t e number of new males (shaded) and females (unshaded) r e c r u i t e d i n t o p o p u l a t i o n . M J 5 N J M 1977 1978 43 F i g u r e 1.7. Mean body weights with 95% conf i d e n c e l i m i t s f o r male and female Peromyscus maniculatus during summer and winter p e r i o d s 1975-77. Sample s i z e above upper con f i d e n c e l i m i t s . F o r e s t (A); Burn (B) ; and Loon Lake (C). Weight in Grams 45 F i g u r e 1.8. Mean growth r a t e s with 95% conf i d e n c e l i m i t s f o r male and female Peromyscus manicnlatus dur i n g 1975-77- Sample s i z e above upper c o n f i d e n c e l i m i t s - F o r e s t p o p u l a t i o n represented by c l o s e d c i r c l e and c l e a r c u t p o p u l a t i o n s by open c i r c l e - F o r e s t (A); Burn (B) ; and Loon Lake (C). A+E-1975 (June - 15 November); A+B-1976 (June - October); A+E-1977 (15 A p r i l - October) ; C-1977 (15 May - Oc t o b e r ) . Ci) -r~> o CD c •+-» c .020 4-.01 5 01 0 + + 76 c/) o c . 005 0 --.005 --2 M A L E S 705 B 65 32 B 123 95 143 F E M A L E S 6e> 51 0 B 62 72 I 50 115 7d B B C 1975 1976 1977 1975 1976 1977 HI F i g u r e 1.9- Median body weight a t sexual maturity and 95% confidence l i m i t s f o r males and females d u r i n g the peri o d June to August of each year. F o r e s t p o p u l a t i o n r e p r e s e n t e d by c l o s e d c i r c l e and c l e a r c u t p o p u l a t i o n s by open c i r c l e . F o r e s t (A); Burn (E) ; and lo o n Lake (C). M A L E S ti) 24 i .Iz! D •+-» CO CO X LO -t-> _C CD c 22 20 18 16 1 4 1 A 12 1 / / T / 7 4 \ \ \ \ o B \ T \ A B 1975 1976 1977 F E M A L E S JT B \ \ \ \ o B \ B 1975 1976 1977 -p-Oo 49 Table 1.1. Trappability estimates for Peromyscus maniculatus on the three study areas for 1975-77. Sample size in parentheses. Maximum trappability is the proportion of those known to be alive that are actually caught in a trap-ping session. Minimum unweighted trappability estimates fi r s t and last captures and provides only one value for each individual regardless of how long i t lives. Forest Burn Loon Lake Males Females Males Females Males Females 1975 0.95 (19) 0.94 (19) 0.79 (37) 0.86 (22) Maximum 1 9 y 6 Q ^ 2 ( 3 g ) Q > 8 9 ( 3 2 ) Q > 7 4 ( 3 g ) Q > 8 4 ( 3 5 ) trappability i g 7 7 Q ^ 5 ( 4 5 ) Q ^ 9 ( 3 5 ) Q ^ Q Q ( 5 2 ) Q ^ 9 ( 3 g ) Q ^ Q ( 3 4 ) Q ^ 9 3 ( 2 1 ) Minimum 1975 0.86 (17) 0.84 (15) 0.71 (28) 0.79 (12) unweighted 1976 0.87 (21) 0.87 (20) 0.74 (25) 0.87 (26) trappability 1977 0.75 (37) 0.78 (20) 0.77 (39) 0.74 (27) 0.75 (22) 0.93 (13) Table 1.2. Proportion of Peromyscus maniculatus in breeding condition on study areas during the breeding season of each year. Sample size in parentheses. Year and Group 1975 Testes scrotal Adults 0.78 (74) 0.90 (40) 0.91 (43) Juveniles 0.14 (21) 0.12 (25) 0.11 (28) Nipples med-rlarge . Adults 0.59 (74) 0.84 (32) 0.74 (39) A-B* Juveniles 0.13 (16) 0.00 (7)+ 0.05 (19) 1977 Testes scrotal Adults 0.86 (74) 0.82 (79) 0.91 (43) Juveniles 0.21 (56) 0.34 (35) 0.11 (28) B-C* Nipples med.-large Adults 0.56 (59) 0.68 (74) 0.74 (39) Juveniles 0.00 (26) 0.00 (39) 0.05 (19) 1976 Testes scrotal Adults 1.00 (44) 1.00 (28) Juveniles 0.00 (6)+ 0.86 (14) Nipples med.-large Adults 0.39 (51) 0.68 (37) - A-B** 51 Table 1.3. Minimum survival rates per 14 days for the three study areas. Sample size in parentheses. Males Forest Burn Loon Lake Season and group (A) (B) (C) Summer 1975 Total 0.92 (84) 0.87 (52) -Adults 0.92 (65) 0.85 (33) -Juveniles 0.89 (19) 0.89 (19) Winter 1975-76 Total 0.68 (34) 0.81 (126) -Summer 1976 Total 0.78 (45) 0.64 (39) -Adults 0.83 (42) 0.65 (26) -Juveniles 0.00 (3) + 0.62 (13) -Winter 1976-77 Total 0.87 (70) 0.78 (49) -Summer 1977 Total 0.85 (120) 0.87 (103) 0.84 (61) Adults 0.88 (67) 0.89 (75) 0.82 (39) Juveniles 0.81 (53) 0.82 (28) 0.86 (22) Winter 1977-78-Total 0.85 (84) 0.80 (137) 0.83 (103) Total 0.84 (437) 0.81 (506) 0.83 (164) + Inadequate sample size to test for difference. Table 1.3 (continued) 51a Females Forest Burn Loon Lake Season and group (A) (B) (C) Summer 1975 Total 0.92 (78) 0.86 (36) -Adults 0.92 (64) 0.89 (27) -Juveniles 0.93 (14) 0.78 (9) + -Winter 1975-76 Total 0.74 (42) 0.74 (62) -Summer 1976 Total 0.90 (50) 0.87 (39) -Adults 0.91 (45) 0.90 (30) -Juveniles 0.80 (5) + 0.78 (9) -Winter 1976-77 Total 0.85 (75) 0.84 (75) 0.84 (101) Summer 1977 Total 0.81 (80) 0.89 (97) 0.86 (50) Adults 0.88 (56) 0.90 (67) 0.89 (36) Juveniles 0.67 (24) 0.87 (30) 0.79 (14) Winter 1977-78 Total 0.76 (54) 0.86 (111) 0.87 (75) Total 0.84 (379) 0.85 (446) 0.86 (125) + Inadequate sample size to test for difference. - 52 Table 1.4. Indices of early juvenile survival for the three populations. Ranges for indices of survival based on samples including 2 or more females. N= number of trapping weeks. Forest Burn Loon Lake mean N Range mean N Range mean N Range Breeding season 1975 0.38 12 0-1.0 1.33 6 0-2.2 — — — Breeding season + to end of 0.38 12 0-1.0 1.34 9 0-2.2 - - -recruitment Breeding season 1976 1.14 8 0-1.0 0.86 8 0-1.0 - - — Breeding season + to end of 1.13 13 0-1.8 1.07 12 0-2.7 - - -recruitment Breeding season 1977 0.87 12 0-1.7 0.62 11 0-2.0 0.82 8 0-0.8 Breeding season + to end of 1.24 16 0-1.7 0.84 14 0-3.0 0.88 12 0-0.8 recruitment Table 1.5. Number of successful pregnancies during breeding seasons and observed and expected numbers of juveniles recruiting into populations up to one month after breeding. Sample size i n parentheses for observed proportion of juveniles surviving and surviving to breed. N = number of trapping weeks. Total N Range Total N Range Total N Range Number of successful pregnancies 1975 15 12 1-3 11 7 1-3 -1976 8 8 1-2 13 8 1-3 -1977 11 12 1-3 18 11 1-4 12 8 1-2 Expected number of juveniles 1975 67.8 49.7 -1976 36.2 58.8 -1977 49.7 81.4 54.2 Observed number of juveniles 1975 22 (32.4%) 39 , (78.5%) 1976 23 (63.5%) 30 (51.0%) 1977 38 (76.5%) 40 (49,1%) Males Females Males Females Males Females Proportion . . 1 surviving 1975 1976 1977 1.00 (5) 1..00 (5.) 1.00 (6) 0.50 (2.) 0.00 (1) 0.67 (3) 0.67 (6) 1.00 (3) 0.94 (17) 0.44 (9) 0.75 (8) 0.60 (10) 0.89 (9) 0.80 (5) 1 Animals caught up to one month before end of breeding and survive at least 2wks. Animals i n reproductive condition before end of breeding. 54 Table 1.6. Sex ratios (proportion of males) in the three populations of Peromyscus maniculatus in 1975-77. Sample size in parentheses. Forest Burn Loon Lake Comparisons Year (A) (B) _ ... (C) _ A-B A-C B-C 1975 0.50 (210) 0.67 (279) - A-B** 1976 0.46 (315) 0.46 (315) -1977 0.62 (468) 0.52 (599) 0.61 (343) A-B** B-C** ** p<.01 significant difference by chi-square. Table 1.7. Minimum number of animals known to be alive in June and October of 1975-77 for forest and clearcut habitats in this study and for 1968-70 in a study by Petticrew and Sadleir (1974). Density is number of animals per hectare. Forest Clearcut 1975 June October 16 22 14 30 1976 June October 14 18 15 24 1977 June October 27 21 29 37 Forest Clearcut 1968 June October 9 22 10 26 1969 June October 28 30 37 32 "after Petticrew and Sadleir (1974) Table 1.8. Summary of the annual variation in demography of forest and clearcut populations of Peromyscus maniculatus. 1975 Forest 1976 1977 1975 Burn 1976 1977 Average density (per ha) 19.6 15.8 22.3 23.3 16.6 29.9 No. recruits per trapping week of breeding season (males) 1.0 1.1 2.2 3.2 1.6 1.9 (females) 0.9 1.1 1.2 2.0 0.9 1.8 Reproductive rate -length of breeding season (weeks) 23 16 22 13 16 20 -number of successful pregnancies 15 8 11 11 13 18 -proportion of breeding animals (males) 0.78 1.00 0.86 0.90 1.00 0.82 (females) 0.59 0.39 0.56 0.84 0.68 0.68 -proportion of recruits surviving to breed 0.50 0.25 0.15 0.38 0.78 0.17 Survival (adults and juveniles summer males -winter 0.92 0.68 0.78 0.87 0.85 0.89 0.87 0.81 0.64 0.78 0.87 0.84 summer^ ' females winter 0.92 0.74 0.90 0.85 0.81 0.87 0.86 0.74 0.87 0.84 0.89 0.92 Average growth rates per day (xlO ^ ) 7.5 2.7 4.9 5.3 1.3 1.7 Average body weight (g) summer males winter 18.3 17.0 18.8 15.2 17.0 16.7 17.2 16.3 17.7 15.0 17.0 15.3 summer females winter 19.5 15.4 19.4 15.8 17.8 15.8 18.3 16.3 19.0 14.9 17.2 16.5 57 CH5PTEE 2 REPOPULATION 0? VACANT CLEARCUT HABITAT AND CONIFER SEED PREDATION BI THE DEEB HOUSE INTRODUCTION C o n i f e r seed l o s s t o rodents has been a problem to f o r e s t e r s and w i l d l i f e managers s i n c e the e a r l y p a r t o f t h i s c e n t u r y . The main c o n t r o l method has i n v o l v e d the use of poison b a i t , u s u a l l y c h e m i c a l l y - t r e a t e d g r a i n , s c a t t e r e d over the area to be seeded. An a l t e r n a t i v e method c o n s i s t s of a p p l y i n g a t o x i c a n t or r e p e l l e n t d i r e c t l y to the t r e e seed such that rodents would be k i l l e d by, or r e p e l l e d from, e a t i n g the seed. The success of these techniques has seldom been s a t i s f a c t o r y . Poison b a i t s are now con s i d e r e d i n e f f e c t i v e because c o n t r o l of rodents i s p o s s i b l e only f o r very s h o r t p e r i o d s . E l i m i n a t i o n of the i n i t i a l rodent p o p u l a t i o n i s incomplete and r e i n v a s i o n from surrounding areas i s o f t e n r a p i d (Oashwiler 1969; H o f f e r et a l . 1969; Bank and Matschke 1972; and Hooven 1975)- Poisons, e i t h e r as b a i t s or as t o x i c a n t s on seeds, are hazardous to non-target s p e c i e s and the f a t e of these c h e m i c a l s i n the environment i s unknown (see review by Evans 1914). In a d d i t i o n , the d i r e c t a p p l i c a t i o n of t o x i c a n t s and r e p e l l e n t s t o seeds has o f t e n 58 reduced seed germination (Badwan 1969, 1970). The c o l o n i z a t i o n by deer mice of depopulated areas was f i r s t s t u d i e d by s e v e r a l workers i n the 1940's ( B l a i r 1940; Spencer 1941; and S t i c k e l 1946). I t may be concluded from these e a r l y s t u d i e s t h a t there was a r a p i d i n v a s i o n of deer mice onto areas from which animals had been removed ( e i t h e r p h y s i c a l l y with snap-traps or by poison b a i t s ) . More re c e n t work on the c o l o n i z a t i o n of vacant h a b i t a t by P. maniculatus has supported these e a r l i e r r e s u l t s ( S a d l e i r 1965; Healey 1967; S u l l i v a n 1977; and F a i r b a i r n 1978). Why then have f o r e s t e r s continued to advocate the poison b a i t i n g of c l e a r c u t areas or the chemical treatment of c o n i f e r seed f o r rodent c o n t r o l , when keeping an area devoid of mice f o r more than a few days i s v i r t u a l l y i m p o s s i b l e ? For the past f o r t y y e a r s , poison b a i t i n g has been c o n t i n u a l l y attempted with very l i t t l e s u c c e s s . I t seems i r o n i c t h a t a r e c e n t F o r e s t Research Report (Oregon State U n i v e r s i t y , 1976) advised the use of poison b a i t s c o n t a i n i n g a n t i c o a g u l a n t s f o r rodent c o n t r o l on areas to be seeded. Even a f t e r n e a r l y h a l f a century o f f u t i l i t y , the use of chemical poisons and r e p e l l e n t s c o n t i n u e s to r e f l e c t the philosophy of f o r e s t e r s d e a l i n g with the problem of d i r e c t seeding and rodent p o p u l a t i o n s . Few s t u d i e s have measured both seed s u r v i v a l and d e n s i t y of deer mice on the removal (poisoned) and c o n t r o l a r e a s . The present study was designed to t e s t the hypothesis that removal of a l l deer mice (simulated poison b a i t i n g ) w i l l r e s u l t i n s a t i s f a c t o r y s u r v i v a l of c o n i f e r seed. I f a poisoned area can be completely depopulated and t h e n maintained f r e e of i n v a s i o n 59 by deer mice from surrounding r e g i o n s , then the consequent s u r v i v a l of c o n i f e r seed should be adequate f o r s u c c e s s f u l s t o c k i n g of a c u t o v e r area. MATERIALS AND METHODS Deer mouse p o p u l a t i o n s From J u l y t o October 1977 and March t o A p r i l 1978, f o u r 1.1 ha g r i d s (G, H, I , and J) and an L-shaped g r i d Q were l i v e -trapped every two weeks with Longworth l i v e - t r a p s . I n a d d i t i o n , 2 f o r e s t g r i d s (D and E) and 2 c l e a r c u t g r i d s (G and I) were trapped i n a s i m i l a r manner during August and September 1975. G r i d s G, H, I, and J were on an area logged i n the f a l l of 1973 followed by s l a s h burning i n August 1974. The s l a s h burn was uniform i n some areas but patchy i n o t h e r s . The main cover was burnt or dead s l a s h with growth of bracken, f i r e w e e d , and s e v e r a l other l e s s abundant s u c c e s s i o n a l herbs, G r i d s D and E were l o c a t e d i n the f o r e s t , as was g r i d Q, which surrounded the north and west s i d e s of g r i d J (see F i g u r e s 1.2 and 2.1a). On each checkerboard g r i d , 49 t r a p s t a t i o n s were l o c a t e d a t 15.2-m i n t e r v a l s marked by f l a g g i n g tape and s t r i n g (Figure 1,4). One l i v e - t r a p was placed w i t h i n a 2-m r a d i u s of each s t a t i o n . Traps were b a i t e d with peanut b u t t e r , Purina l a b chow, and Terylene b a t t i n g was s u p p l i e d as bedding. Traps were s e t on day 1, checked on days 2 and 3, and then l o c k e d open between t r a p p i n g p e r i o d s . A l l deer mice captured were weighed on P e s o l a s p r i n g 60 balances, sexed, and ear-tagged with s e r i a l l y numbered f i n g e r l i n g f i s h tags. Information on breeding performance was gained by p a l p a t i n g t e s t e s and n o t i n g the c o n d i t i o n of vagina and niammaries. During the removal experiment (simulated poison b a i t i n g ) i n 1915, g r i d s G and E had k i l l - t r a p s c o n t i n u o u s l y s e t to remove a l l animals. In the experiments dur i n g the e a r l y f a l l of 1977 and the s p r i n g of 1978, a l l t r a p p a b l e s p e c i e s of s m a l l mammals were removed from g r i d J each t r a p p i n g week. Seed p o p u l a t i o n s Each of the e x p e r i m e n t al g r i d s was s y s t e m a t i c a l l y d i v i d e d i n t o 36 {15.2 HI X 15.2 m = 231 sguare m) p l o t s . In each p l o t , a 0*61 m x 0.61 m guadrat was l o c a t e d i n a s u i t a b l e area f o r seed sampling and r e c o v e r y (Figure 1.4). Equal amounts of Douglas f i r seed were used on both g r i d s (I and J) d u r i n g the 2 experimental seeding t r i a l s of e a r l y f a l l 1977 (0.81 kg/ha) and the two seeding t r i a l s i n the s p r i n g of 1978 .(0.405 kg/ha). P r i o r to each experiment, seed was weighed and packaged a c c o r d i n g t o the amount d e s i r e d per square meter of g r i d (area of g r i d = 8,361.3 sq. m). S e v e r a l samples of 2500 Douglas f i r seeds were weighed with the mean value r e p r e s e n t i n g t h a t given number of seeds. T h i s value was subsequently used as a m u l t i p l e to o b t a i n the number of seeds by weight f o r each of the 36 p l o t s on a g r i d . In each of 25 randomly chosen p l o t s , a known d e n s i t y of seed was placed i n one or more of the 4 (0.093 sg. m) u n i t s i n a seed-sampling guadrat. L o c a t i o n o f i n d i v i d u a l seeds was marked by wooden t o o t h p i c k s - The r e s t of the a l l o t t e d seed was 6 1 then spread by hand as u n i f o r m l y as p o s s i b l e over the remaining area of t h a t p l o t . Care was taken not to throw more seed by a c c i d e n t i n t o the sampling quadrate A p l a s t i c cover was placed over each guadrat on a g r i d . These covers prevented r a i n from d i s t u r b i n g the seed-sampling areas but were propped up to allow mice and any other p o t e n t i a l seed predators f r e e access under them. They were p l a c e d on the g r i d s at l e a s t one week before the f i r s t seed experiment began. Sampling was then conducted two weeks a f t e r seeding f o r the f i r s t t r i a l i n each o f the f a l l and s p r i n g p e r i o d s and at 3 days ( f a l l period) and 5 days f s p r i n g period) a f t e r seeding f o r the second t r i a l i n each period-I p l a c e d one s e e d - f a l l t r a p i n a c e n t r a l p o s i t i o n on each g r i d t o measure p o t e n t i a l n a t u r a l s e e d - f a l l during these experiments. These t r a p s were 0.37 sg. m i n area and composed of a frame box (2.5-cm x 7.5-cm s i d e s ) . Hindow s c r e e n (14 by 18 mesh) covered the base with 1 cm mesh hardware c l o t h on the top a l l o w i n g seeds to f a l l i n t o the t r a p . RESULTS T r a p p a b i I t y The a n a l y s i s of the c o n t r o l and experimental p o p u l a t i o n s i s based on the assumption that most of the i n d i v i d u a l s i n a given p o p u l a t i o n are c a p t u r e d . Maximum t r a p p a b i l i t y has been d e f i n e d by Krebs et a l . (1976) as f o l l o w s : 62 t r a p p a b i l i t y = No. a c t u a l l y caught at time i / Mo- known to be present at time i This method i n c l u d e s a l l c a p t u r e s and t h e r e f o r e , tends to b i a s upwards the t r a p p a b i l i t y estimate- Minimum unweighted t r a p p a b i l i t y i s a l e s s biased estimate s i n c e i t e l i m i n a t e s f i r s t and l a s t captures and hence a l l mice caught only once or t * i c e . T h i s estimate of t r a p p a b i l i t y provides only one value f o r each i n d i v i d u a l r e g a r d l e s s of how long i t l i v e s and so i s not i n f l u e n c e d by animals with long capture h i s t o r i e s - Both of these e s t i m a t e s f o r the two p o p u l a t i o n s i n the f a l l 1977 and s p r i n g 1978 experiments are given i n Table 2-1. T r a p p a b i l i t y estimates f o r c o n t r o l and experimental animals were s i m i l a r during the f a l l experiment. There was l i t t l e d i f f e r e n c e between sexes at t h i s time. In the s p r i n g experiment, t r a p p a b i l i t y of males was s i m i l a r on both g r i d s but that of female deer mice was much higher on the experimental seed g r i d . These r e s u l t s support my c o n t e n t i o n t h a t Douglas f i r seed on removal g r i d J (or g r i d I) would not lower the t r a p p a b i l i t y of deer mice. Consequently, my continuous l i v e -t r a p p i n g of g r i d J d u r i n g the f a l l and s p r i n g experiments e f f e c t i v e l y removed the m a j o r i t y of deer mice and a c c u r a t e l y simulated the use of poison b a i t s . Experimental poison ha l t i n g . To show t h a t deer mice are e f f e c t i v e l y e l i m i n a t e d from seeded areas by the use of poison b a i t s , one must measure seed s u r v i v a l and compare i t with t h a t on a c o n t r o l a r e a . Comparison 63 of s u r v i v a l of Douglas f i r seed on c o n t r o l and removal g r i d s i n 1975 i s shown i n Table 2.2. Animals were c o n t i n u a l l y removed by k i l l - t r a p s on the experimental g r i d s , whereas the r e s i d e n t p o p u l a t i o n was not manipulated on the c o n t r o l a r ea. In both h a b i t a t s , seed s u r v i v a l was very low, with the removal g r i d s having even l e s s seed s u r v i v i n g than on the c o n t r o l . The t o t a l number of mice c o l o n i z i n g the removal areas (61 i n f o r e s t and 34 on c l e a r c u t ) was immediate and continuous throughout the s i x -week experiment. Bhat i s the o r i g i n of these mice on c l e a r c u t s and a t what r a t e do they move onto an area s e t with poison b a i t s or o t h e r removal methods? F a l l Removal T h i s question was answered i n a removal experiment i n August-September 1977. A map f o r t h i s experiment i s shown i n F i g u r e 2-Ta. Grid J was a c l e a r c u t experimental area bordered on two s i d e s by g r i d Q (L-shaped) i n the f o r e s t . These g r i d s were trapped normally f o r s e v e r a l weeks be f o r e the s t a r t of the experiment so t h a t a l l animals were tagged and t h e i r place of o r i g i n c o u l d be determined. F i g u r e 2.1b i l l u s t r a t e s my p r e d i c t e d response of mice moving onto the removal area (J) from the surrounding f o r e s t and c l e a r c u t . The r e s u l t s of the f i r s t 2 removal p e r i o d s (experiment A) are shown s c h e m a t i c a l l y i n F i g u r e 2.2. From August 21-24, a t o t a l cf 41 mice was removed from g r i d J , 36.65? of these were non-resident, c o l o n i z i n g animals. During the second removal p e r i o d another 10 mice were removed, a l l c o l o n i z i n g animals from g r i d Q o r other surrounding areas. There was no c o n i f e r seed s u r v i v i n g at the end of t h i s 12-day experiment. Thus, the 64 removal of a l l r e s i d e n t mice on g r i d J d i d not r e s u l t i n a higher s u r v i v a l of seed r e l a t i v e to t h a t cn a c o n t r o l area. These animals were r e p l a c e d by mice from surrounding areas w i t h i n a 12-day p e r i o d . T h i s removal experiment was then repeated to determine the r a t e at which c o n i f e r seed was eaten by c o l o n i z i n g mice on poisoned areas. F i g u r e 2.3 s c h e m a t i c a l l y o u t l i n e s removal p e r i o d s no. 3 and 4 i n experiment B. On September 18-19, 18 animals were removed from g r i d J . Two days l a t e r on September 21 (traps were c o n t i n u o u s l y s e t d u r i n g t h i s experiment), f o u r t e e n mice had c o l o n i z e d the a r e a , and only 5% of the Douglas f i r seed was s t i l l present compared with 3% f o r the c o n t r o l g r i d . In the f i n a l t r a p p i n g peri o d o f t h i s experiment, 16 mice (11 from g r i d Q, 1 from g r i d G, and 4 new) had again c o l o n i z e d the removal g r i d . In summary, d u r i n g the s i x weeks of t h i s removal experiment, a t o t a l o f 99 mice c o l o n i z e d removal g r i d J . The o r i g i n s of these mice were as f o l l o w s : 26 r e s i d e n t mice on g r i d J ; 32 mice from g r i d Q i n the f o r e s t ; 7 from g r i d G; and 34 new animals from surrounding areas. Thus, there i s a continuous movement of animals onto a poisoned area, and a r e s u l t a n t l o s s of 95% of the c o n i f e r seed w i t h i n a 3-day p e r i o d . S p r i n g Removal Populations of Peromyscus maniculatus g e n e r a l l y reach t h e i r h i g h e s t d e n s i t y i n the f a l l and d e c l i n e over winter to the lowest point i n the springs T h i s annual c y c l e on the c o n t r o l , seed, and removal g r i d s i s i l l u s t r a t e d i n F i g u r e 2.4. Since the f a l l 1977 removal experiment was performed d u r i n g the p e r i o d of 65 h i g h e s t p o p u l a t i o n d e n s i t y , the r a p i d c o l o n i z a t i o n of the depopulated area may have been s t r i c t l y a r e s u l t of an abundance of s u r p l u s animals. The f a l l i s thus a poor time f o r seeding logged areas. Also, d i r e c t s e e d i n g should be done i n the s p r i n g when c o n d i t i o n s f o r germination and s e e d l i n g e s t a b l i s h m e n t are f a v o u r a b l e (Arnott 1973). Thus, t h i s experimental poison b a i t i n g and seeding was r e p l i c a t e d i n the s p r i n g of 1978. Many f o r e s t e r s attempt to reduce the number of s e e d - e a t i n g s m a l l mammals by p r e - b a i t i n g with poison before d i r e c t seeding (Hooven 1975). In my s p r i n g experiments, seeding was c a r r i e d out a f t e r the second removal p e r i o d which allowed s i m u l a t i o n of a p r e - b a i t i n g p e r i o d (experiment C i n F i g u r e 2-5). During t h i s time, 16 mice were removed from g r i d J . . There was nc c o n i f e r seed s u r v i v i n g on the c o n t r o l ( g r i d I) and only 8.0% on g r i d J at t h e end of the 12-day experiment. Again, the removal of r e s i d e n t mice on g r i d J d i d not r e s u l t i n an a p p r e c i a b l y h i g h e r s u r v i v a l of seed compared with that on the c o n t r o l a r e a . Thus, removal of animals two weeks p r i o r t o seeding was not e f f e c t i v e i n p reventing seed l o s s to deer mice. This removal experiment was repeated to determine the r a t e at which Douglas f i r seed was eaten d u r i n g the s p r i n g . F i g u r e 2.6 i l l u s t r a t e s the t h i r d and f o u r t h removal p e r i o d s (experiment D). L i v e - t r a p s were c o n t i n u o u s l y s e t from A p r i l 2 t o 7 a f t e r the removal area was seeded on A p r i l 2. A f t e r f i v e days, 21 deer mice c o l o n i z e d the removal a r e a , and only 7-4% of the Douglas f i r seed was s t i l l p resent compared with 10% on the c o n t r o l g r i d . In the f i n a l t r a p p i n g p e r i o d of t h i s experiment, 11 mice (3 from g r i d G, 5 from g r i d Q, and 3 new) had again 66 c o l o n i z e d the removal g r i d . In summary, a t o t a l of 48 mice c o l o n i z e d removal g r i d J. The o r i g i n s of these mice were as f o l l o w s : 14 r e s i d e n t mice on g r i d J ; 15 mice from g r i d Q i n the f o r e s t ; 9 from g r i d G; and 10 new animals. Thus, there i s a continuous source of animals moving onto a poisoned area during the s p r i n g , r e p o p u l a t i n g that a r e a , and e a t i n g 92.6% of the c o n i f e r seed w i t h i n a 5-day p e r i o d . The c o l o n i z a t i o n of the removal area by other s p e c i e s of s m a l l mammals (Microtus o r e g o n i , Sorex spp., and Clethrionomys gapperi) was a l s o monitored i n these experiments. These r e s u l t s are l i s t e d i n T a b l e 2.3. P r i o r t o the f a l l removal experiment, t h e r e was l i t t l e d i f f e r e n c e i n the average number o f i n d i v i d u a l s of other s p e c i e s . However, the t o t a l numbers of each of the three s p e c i e s which c o l o n i z e d removal g r i d J was much higher than the average numbers per t r a p p i n g p e r i o d on e i t h e r g r i d H or g r i d I duri n g the f a l l and sp r i n g experiments. There appeared to be no measurable n a t u r a l f a l l of Douglas f i r seeds i n the s e e d - f a l l t r a p s on any o f the g r i d s i n t h i s study. DISCUSSION In these experiments I attempted t o maintain areas f r e e of deer mice i n a s i m u l a t i o n of poison b a i t i n g . The 1975 experiment used l i v e - t r a p s supplemented with k i l l - t r a p s which sere c o n t i n u o u s l y s e t . The experiments i n 1977 and 1978 used 67 only l i v e - t r a p s set f o r two n i g h t s every two weeks (with minor e x c e p t i o n s ) . Peromvscus maniculatus i s very trappable (see T a b l e s 1-1 and 2.1) and r e a d i l y e n t e r s u n f a m i l i a r t r a p s . I have assumed t h a t t h i s t r a p p i n g program captured the m a j o r i t y of animals, both r e s i d e n t and those c o l o n i z i n g the removal g r i d from surrounding areas, during c o n s e c u t i v e t r a p p i n g p e r i o d s . An a l t e r n a t i v e design would have been to t r a p the removal area c o n t i n u o u s l y . T h i s was done duri n g experiment B i n 1977 and experiment D i n 1978 and i s assumed to have the same e f f e c t as continuous p o i s o n i n g . I t c o u l d be argued t h a t t r a p p i n g only every two weeks would have allowed more mice to occupy the removal area than i f poison b a i t s were c o n t i n u a l l y k i l l i n g them. In a d d i t i o n , some deer mice may have avoided t r a p s because of the temporary abundant food supply a v a i l a b l e from the a p p l i c a t i o n of c o n i f e r seed* However, both these o b j e c t i o n s overlook the p o s s i b i l i t y of b a i t avoidance by mice. T h i s phenomenon was e v i d e n t i n the work of T e v i s (1956c), who r e p o r t e d that every attempt to p r o t e c t seed by k i l l i n g rodents with poison b a i t s i n the Douglas f i r r e g i o n of C a l i f o r n i a had f a i l e d . He concluded that poisoning only removes pa r t of the p o p u l a t i o n of deer mice and some i n d i v i d u a l s always s u r v i v e by b a i t avoidance and continue t o eat c o n i f e r seed. Thus, the p o s s i b i l i t y of i n e f f i c i e n t removal of animals because of t r a p avoidance would be s i m i l a r to or l e s s than that a s s o c i a t e d with b a i t avoidance. Trap avoidance d i d not a f f e c t the p r e d i c t e d r e s u l t s of t h i s study because of the great number of mice captured and high m o r t a l i t y o f seed dur i n g experiments B and D when l i v e - t r a p s were c o n t i n u o u s l y set f o r 4-night (E) and 6-68 n i g h t (D) p e r i o d s . In removal s t u d i e s with other s p e c i e s of s m a l l mammals, depopulated areas were c o l o n i z e d e i t h e r immediately or very s h o r t l y a f t e r the r e s i d e n t animals had been removed. Spencer (194 1) removed s m a l l mammals c o n t i n u o u s l y from an area i n the Sonoran Desert and found a p e r i o d i c i t y i n extent o f i n v a s i o n which was dependent on the p o p u l a t i o n d e n s i t y of the given s p e c i e s . Calhoun and Hebb (1953) removed s m a l l mammals by snap-t r a p p i n g and found immediate i n v a s i o n of the experimental p l o t . Van Vleck (1968) rep o r t e d that H i c r o t u s pennsylvanicus c o l o n i z e d a depopulated area up to the pre-removal d e n s i t y i n a pe r i o d of two weeks. T h i s movement was density-dependent as was found by Myers and Krebs (1971) f o r 2 s p e c i e s o f H i c r o t u s and by Krebs e t a l . (1976) f o r M- townsendii. For these s p e c i e s of v o l e s , these authors concluded t h a t the immigration r a t e i n t o e s t a b l i s h e d p o p u l a t i o n s was much l e s s than the immigration r a t e i n t o vacant areas. B a r t e l l and Badvanyi (1977b) c o u l d not remove a l l H i c r o t u s pennsylvanicus from a hardwood p l a n t a t i o n by the use of poisoned g r a i n . S i m i l a r r e s u l t s from removal experiments have been obtained f o r Peroroyscus ( B l a i r 1940; S t i c k e l 1946; S a d l e i r 1965; Healey 1967; S u l l i v a n 1977; and F a i r b a i r n 1978), and i n t h i s study. A l s o , the movement of other s m a l l mammal s p e c i e s onto the removal area ( g r i d J) accompanied the i n f l u x of deer mice and reached l e v e l s much higher than those observed on the c o n t r o l areas (see Table 2.3) When my removal (poison b a i t i n g ) experiments are compared with those reported i n the l i t e r a t u r e , t here have been very few 69 s t u d i e s which have measured both seed s u r v i v a l and d e n s i t y of deer mice on the b a i t e d and c o n t r o l areas- Schopmeyer (1940) concluded t h a t b a i t i n g was s u c c e s s f u l but d i d not present q u a n t i t a t i v e data f o r deer mice- Orr-Ewing (1950b) presented i n f o r m a t i o n on both seed s u r v i v a l and deer mice but there was l i t t l e data a v a i l a b l e f o r the p r e - b a i t i n g p e r i o d - In a d d i t i o n , the b a i t i n g area was l o c a t e d on a p e n i n s u l a which r e s t r i c t e d i n v a s i o n by mice. A l l e n et a l . (1955) reported s u c c e s s f u l s t o c k i n g of c l e a r c u t s , but t h e i r c e n s u s i n g methods f o r determining the e f f e c t of poison b a i t i n g was not p r o p e r l y c o n t r o l l e d . , McGregor (1958), Yeatman (1960), Hooven (1953, 1955a) and Gashwiler (1969) r e p o r t e d r e p o p u l a t i o n of poisoned c l e a r c u t s s h o r t l y a f t e r b a i t i n g and suggested t h a t r e b a i t i n g s e v e r a l times was necessary. Cochran (1970) a l s o came t o t h i s c o n c l u s i o n and s t r e s s e d the need f o r more i n t e n s i v e sampling of rodent p o p u l a t i o n s and t h e i r e f f e c t on c o n i f e r seed i f poisoned b a i t s are to be used. In g e n e r a l , the few f o l l o w - u p censuses that have been done concluded that rodents are absent from a poisoned area f o r a very s h o r t time o n l y as evidenced i n my study. T h e r e f o r e , the c o n t i n u a l r e a p p l i c a t i o n of poison b a i t s i s necessary f c r any permanent r e d u c t i o n i n the numbers of small mammals^ H o f f e r et a l . (1969) came to a s i m i l a r c o n c l u s i o n i n t h e i r r e p o r t of mice s u r v i v i n g poison b a i t i n g . My experiments were conducted on s m a l l e r areas (1.1 ha) than most c l e a r c u t r e g i o n s (>20 ha) which have been b a i t e d with poisons. Conseguently, there i s a much g r e a t e r area f o r mice to c o l o n i z e i n these l a r g e - s c a l e p o i s o n i n g programs. However, because of the r a p i d r a t e a t which mice c o l o n i z e d my removal 70 a r e a s , and the i n a b i l i t y to remove a l l animals with poi s o n , I conclude that seed s u r v i v a l on l a r g e c l e a r c u t s would be l i t t l e b e t t e r than that obtained i n t h i s study. The more l o g i c a l approach of having the c o n i f e r seed c a r r y i t s own r c d e n t i c i d e or r e p e l l e n t was f i r s t d i s c u s s e d by Spencer (1954). Since then, F i n n i s (1955) and Hooven (1955b, 1956, 1957) concluded that the r e p e l l e n t , t e t r a m i n e , was e f f e c t i v e i n stopping mice from e a t i n g t r e a t e d seed and t h a t e n d r i n r e s u l t e d i n an abrupt r e d u c t i o n i n numbers. However, Dick and Lawrence (1S57) reported that rodents d i d not avoid f i r seed as a r e s u l t of exposure to t etramine-coated seed. T h i s r e s u l t was a t v a r i a n c e with p r e v i o u s l y reported f i n d i n g s . Thus, the e a r l y r o d e n t i c i d e s such as s t r y c h n i n e and 1080 (sodium f l u o r a c e t a t e ) were r e p l a c e d by tetramine and e n d r i n , which s i m i l a r l y f a i l e d to remove rodent p o p u l a t i o n s completely. In the past ten years, r e s t r i c t i o n s on the above chemicals and the need f o r a poison or r e p e l l e n t which was not hazardous to non-target s p e c i e s produced s e v e r a l more v e c t o r s f o r r e d u c i n g p o p u l a t i o n s of deer mice. Howard e t a l . (1S7G) and Marsh et a l . (1974) repo r t e d on poison b a i t s which r e s u l t e d i n complete r e d u c t i o n of r e s i d e n t animals. However, there was s t i l l the i n e v i t a b l e i n v a s i o n of new mice onto the poisoned areas. Fank and Matschke (1972) came t o a s i m i l a r c o n c l u s i o n from t h e i r p o isoning program and emphasized t h a t methods to c o n t r o l r e i n v a s i o n must be evaluated as w e l l as the hazard to non-target s p e c i e s . Passcf (1974) reviewed the use of r o d e n t i c i d e s i n C a l i f o r n i a and the new a n t i c o a g u l a n t b a i t s t h a t had been developed. However, he d i d not d i s c u s s the problem of t h e i r 71 f a i l u r e to remove a l l mice from a poisoned area. Hcoven (1975) d i s c u s s e d the merits of two new a n t i c o a g u l a n t poisons (chlcrophacinone and diphacinone) f o r c o n t r o l of s m a l l f o r e s t mammals. He r e p o r t e d t h a t chlorophacinone was only s l i g h t l y t o x i c to b l a c k b i r d s , ducks, and pheasants. The g u e s t i o n i s then r a i s e d as to what i s t h e d e f i n i t i o n of s l i g h t l y t o x i c f o r non-t a r g e t s p e c i e s i n the wild? T h i s r e p o r t concluded t h a t d i a p h a c i n o n e - k i l l e d deer mice caused secondary p o i s o n i n g when f e d to predator owls and weasels. Secondly, Hooven (1975) s t a t e d t h a t t h i s hazard was reduced i n nature because a f f e c t e d animals disappeared i n t o t h e i r burrows before death, which reduced the a v a i l a b i l i t y of the poison to predators. Evidence i s l a c k i n g f o r t h i s statement, and i n g e n e r a l , the f a t e of s m a l l mammals which d i e of poisoning or of n a t u r a l causes i s very p o o r l y known. Marsh et a l . (1977) f u r t h e r d i s c u s s the e f f i c a c y of the above two chemicals and i n d i c a t e the problems a s s o c i a t e d with inclement weather (r a i n and snow) i n making the b a i t a v a i l a b l e and a c c e p t a b l e to deer mice f o r more than a few days. Howard e t a l . (1977) concluded from t h e i r study on a v e r s i v e c o n d i t i o n i n g of mice to t o x i c a n t s t h a t deer mouse c o n t r o l should not employ the same poison at i n t e r v a l s s h o r t e r than 8 months. The management i m p l i c a t i o n s of t h i s are obvious when r e a p p l i c a t i o n of b a i t i s attempted to c o n t r o l i n v a s i o n of the t r e a t e d area by mice. Very few animals (as i n d i c a t e d i n F i g u r e 3.5, 5 mice/ha co u l d d e s t r o y 50,000 Douglas f i r seeds i n 15 days) are r e q u i r e d t o d e s t r o y most of the c o n i f e r seed d i s p e r s e d over a c l e a r c u t . I t i s i m p o s s i b l e to remove a l l animals, and yet f o r the past 72 f o r t y y e a r s , poison b a i t i n g has been c o n t i n u a l l y attempted, with very l i t t l e success. Thus, i n t e n s i v e study of seed s u r v i v a l and movements of deer mice cn c o n t r o l and removal (poisoned) areas , i n my study, has shown the f u t i l i t y o f b a i t i n g owing t o the r a p i d r e i n v a s i o n by mice and consequent d e s t r u c t i o n of the seed supply. I t has a l s o shown the need f o r a new philosophy i n d e a l i n g with t h i s h i s t o r i c a l and contemporary problem of rodents consuming the seed supply used i n d i r e c t - s e e d i n g p r o j e c t s . The b i o l o g i c a l c o n t r o l technique d e s c r i b e d i n t h i s t h e s i s p r o v i d e s the b a s i s f o r t h i s much-needed new approach to r e f o r e s t a t i o n . 73 F i g u r e 2. 1a- Map of study g r i d s G, and Q. G r i d Q f o r e s t . G r i d s G and J were area f o r removal experiments showing was L-shaped and l o c a t e d i n the l o c a t e d on the c l e a r c u t a rea. 74' + + * Grid Q I 1 1 \ 1 1 r- -I 1 \ K 1 H—I—»—I—I 1 1—| r -I—I—1 I I \ 4 V H 1 f 1 1 1—\ + trap stat ion Grid J Removal CLEARCUT FOREST N Grid G Sca l e : 1 cm= 23 m F i g u r e 2 . 1 b - Schematic i l l u s t r a t i o n of the p r e d i c t e d response of mice moving onto the removal area (e.g. an area t r e a t e d with poison b a i t s ) , g r i d J , from surrounding r e g i o n s . 76 77 f i g u r e 2.2- Schematic i l l u s t r a t i o n o f the o r i g i n o f mice c o l o n i z i n g removal g r i d J d u r i n g the f i r s t two t r a p p i n g p e r i o d s of experiment ft i n the f a l l of 1977-7$ Fall 1977 EXPERIMENT A. Removal Period No. 1 . Aug. 21 A l l animals removed Ori g i n of mice col o n i z i n g removal B Grid J (resident) A Grid Q ; O New ' O ' A B A l l animals removed A m\ Q o A ng Ea o , •' m Aug. 23 O S A O I O A l l animals removed 1 o 1 A Aug. 24 A l l animals removed Douglas f i r seed (0.81 kg/ha)' set out on Aug. 24; checked 12 days l a t e r (Sept. 5) % Survival of seed ' Aug. 24 Control Removal 100 100 Sept. 5 Removal Period No. 2 ' • Sept. 4 O O o o A l l animals removed Sept. 5 A l l animals A 1 removed O O 1 79 F i g u r e 2 . 3 . Schematic i l l u s t r a t i o n of the o r i g i n of mice c o l o n i z i n g removal g r i d J d u r i n g the t r a p p i n g p e r i o d s no. 3 and 4 of experiment B. Fall 1977 EXPERIMENT B. Removal Period No. S A 9 O • A ® O O O o A l l animals, removed . 80 O r i g i n of mice colonizing removal area: © Grid G.. A Grid Q O New Sept. 19  O A l l animals removed Sept. 21 O ° ' O A O A ° © o A O O O. A l l animals removed Douglas f i r seed (0.81 kg/ha) set out on Sept. 18; checked 3 days l a t e r (Sept. 21) % Sur v i v a l of seed , Sept. 1£ Control Removal 100 100 Sept. 21 3i.O 5.0 Removal Period No. 4 Oct. 2 Oct. 3 81 F i g u r e 2.4. P o p u l a t i o n d e n s i t y on c o n t r o l g r i d H, seed g r i d I , and removal g r i d J d u r i n g the f a l l 1977 and s p r i n g 1S78 seeding experiments. 82: Control Grid H Removal Grid J Removal Mar Apr 1978 Removal Aug Sep Oct 1977 83 F i g u r e 2.5. Schematic i l l u s t r a t i o n of the o r i g i n of mice c o l o n i z i n g removal g r i d J d u r i n g the f i r s t two t r a p p i n g p e r i o d s of experiment C i n s p r i n g 1978. 84 Spring 1978 EXPERIMENT C. Removal Period No. 1 March 5 • • A l l animals _ • removed • • • • • • Origin of mice colonizing removal • Grid J (resident) • Grid G O New March 6 A l l animals • removed • Removal Period No. 2 March 19 March 20 O A l l animals removed A l l animals removed Douglas f i r seed (0.405 kg/ha) set out on March 2 ; checked 12 days l a t e r ( A p r i l 1) - % Survival of seed March 20 A p r i l 1 Control Removal 100.0 100.0 0.0 8.0 85 F i g u r e 2.6. Schematic i l l u s t r a t i o n o f the o r i g i n o f mice c o l o n i z i n g removal g r i d J d u r i n g the t r a p p i n g p e r i o d s no. 3 and 4 of experiment D. Spring 1978 EXPERIMENT D. Removal Period No. 3 A p r i l 2 O O A l l animals removed 86 Origin of mice co l o n i z i n g removal • Grid G A Grid Q O New A p r i l 3 , A l l animals removed A A A l l animals removed • A A • O — n r i LU , A l l animals A removed O O O A Douglas f i r seed (0.405 kg/ha) set out on A p r i l 2; checked' 5 days l a t e r ( A p r i l 7) % S u r v i v a l of seed A P r i l 2 A p r i l 7 Control 100.0 10.0 Removal 100.0 7.4 Removal Period No. 4 A p r i l 16 A p r i l 17 A o A A • • . & o o * O A A • A A o A 87 Table 2.1. Trappability estimates for Peromyscus maniculatus on the control and experimental areas. Sample size in parentheses. Maximum trappability is the proportion of those known to be alive that are actually caught in a trapping session. Minimum unweighted trappability estimates fi r s t and last captures and provides only one value for each individual regardless of how long i t lives. Control Grid H Seed experimental Grid I Males Females > Males Females Fall 1977 Maximum trappability 0 .72 (30) 0.79 (20) 0 .73 (34) 0.76 (28) Minimum unweighted trappability 0 .71 (26) 0.75 (17) 0 .66 (29) 0.66 (22) Sprint 1978 Maximum trappability 0 .88 (14) 0.61 (10) 0 .81 (23) 0.71 (19) Minimum unweighted 0 .74 (9) 0.39 (6) 0 .71 (16) 0.54 (13) trappability Table 2.2. Comparison of survival of Douglas f i r seed on control and removal grids. The number of animals removed and number of seeds surviving on removal areas are compared with control areas which were seeded in an idential manner but did not have the resident population of mice removed. The experiment was conducted for six weeks (August 14 - September 25, 1975). I n i t i a l seeding density was 3.24 kg/ha. . Forest Clearcut Control Removal Control Removal Number of animals captured during 16* 61 23* 34 experiment Percentage of Douglas-fir seed 13.0 9.0 4.7 3.6 surviving * average of 4 trapping periods Table 2.3. Number of Oregon voles, shrews, and red-backed voles captured on control grid H and experimental seed grid I and number of these animals removed from grid J. The values for grids H and I are the averages, and for grid J are the total numbers, for the four trapping periods during each of the f a l l and spring experiments. Control Seed experimental Removal Grid H Grid I Grid J Vole. Shrew RBV Vole Shrew RBV Vole Shrew RBV Pre-removala 2.5 2.5 0 2.0 1.0 0 1.0 2.0 1.5 Fall 1977 5.8 3.5 0 3.0 6.0 0 20 18 8 Spring 1978 3.3 3.0 0 3.0 0.8 0 22 8 3 a Average of 2 trapping periods prior to f a l l removal experiments vole (Oregon vole) RBV (Red-backed vole) 90 CHAPTER 3 THE USE OF ALTERNATIVE FOODS TO REDUCE CONIFER SEED PREDATION BY DEER MICE INTRODUCTION B i o l o g i c a l c o n t r o l has been t r a d i t i o n a l l y d e f i n e d as an attempt t o reduce the average d e n s i t y of a pest p o p u l a t i o n by the a c t i o n s o f p r e d a t o r s , p a r a s i t e s , or dis e a s e s - However, b i o l o g i c a l c o n t r o l may a l s o r e f e r to a s i t u a t i o n where, without any change i n pest numbers, damage i s reduced or e l i m i n a t e d by a b i o l o g i c a l agent or process- Using p r e f e r r e d (buffer) or a l t e r n a t i v e foods may thus be co n s i d e r e d as b i o l o g i c a l c o n t r o l . T h i s approach along with h a b i t a t manipulation have been di s c u s s e d by Howard (1967). For b i r d s , p r o v i d i n g a l t e r n a t i v e foods has been f a i r l y s u c c e s s f u l i n d i v e r t i n g juncos from f i r seed on a c u t o v e r area (Hagar 1960) o r i n l u r i n g waterfowl away from vegetable crops (Howard 1967). For mammals, prunings p i l e d around the base of orchard t r e e s have o f t e n minimized damage from meadow v o l e s ( F i t z w a t e r 1962). The a v a i l a b i l i t y of a l t e r n a t i v e and p r e f e r r e d s p e c i e s of browse may reduce browsing of c o n i f e r s e e d l i n g s by sncwshoe 91 hares (Badwan and Campbell 1968). By p r o v i d i n g a l t e r n a t i v e f o o d s , v a r i o u s authors have attempted to reduce deer browsing (Boy 1960; Baron et a l . 1966; Dasmann et a l . 1967; Campbell 1974; and Campbell and Evans 1975). Seed p r e d a t i o n by the deer mouse (Peromyscus maniculatus) and other rodents has c o n t r i b u t e d t o the f a i l u r e i n r e g e n e r a t i n g c u t o v e r f o r e s t l ands as well as overgrazed range l a n d s . E v e r e t t e t a l . (1978) d i s c u s s the advantages of understanding the food h a b i t s and p r e f e r e n c e s o f deer mice. These authors b e l i e v e t h a t seed p r e d a t i o n may be reduced by p l a n t i n g seed s p e c i e s which are l e s s p r e f e r r e d by the deer mouse than indigenous foods. S i m i l a r l y , one or more a l t e r n a t i v e foods that mice p r e f e r or take as r e a d i l y as c o n i f e r seed c o u l d be used i n r e f o r e s t a t i o n p r o j e c t s to l e s s e n p r e d a t i o n on the t r e e seed. Some work on seed preference has r e c e n t l y been done f o r g r a n i v o r c u s b i r d s (Gcebel and Berry 1976) and f o r deer mice ( E v e r e t t e t a l . 1978) i n h a b i t i n g range l a n d , but no r e s e a r c h has been done on deer mouse seed p r e f e r e n c e and consumption under f i e l d c o n d i t i o n s f o r the purpose of s u c c e s s f u l r e f o r e s t a t i o n by d i r e c t s e e d i ng. T h i s study was designed t o determine the responses of deer mice t o a wide range o f d e n s i t i e s of Douglas f i r seed. I f the upper l i m i t s f o r the number of mice and number of seeds taken per mouse can be determined, then the use of a l t e r n a t i v e foods with Douglas f i r seeds (or other c o n i f e r seeds) should r e s u l t i n reduced p r e d a t i o n on these t r e e seeds. 92 MATERIALS AND METHODS From May to September 1975, A p r i l to November 1976, and March t o November 1977, one c o n t r o l and f i v e experimental g r i d s (1.1 ha) i n f o r e s t (A, B, C, D, E, F) and at the Burn and Slash study areas (G, H, I , J , R, 1) were l i v e - t r a p p e d every two weeks with Longworth l i v e - t r a p s . Another f o r e s t g r i d (P), and two c l e a r c u t g r i d s (M and N) were a l s o trapped i n 1977. On each checkerboard g r i d , 49 trap s t a t i o n s were l o c a t e d at 15.2-m i n t e r v a l s marked by f l a g g i n g tape and s t r i n g (Figure 1.4). One l i v e - t r a p was placed w i t h i n a 2-m r a d i u s of each s t a t i o n . Traps were b a i t e d with peanut b u t t e r , P u r i n a l a b chow, and T e r y l e n e b a t t i n g was s u p p l i e d as bedding. Traps were s e t on day 1, checked on days 2 and 3, and then l o c k e d open between t r a p p i n g p e r i o d s . A l l deer mice captured were weighed cn Pesola s p r i n g balances, sexed, and ear-tagged with s e r i a l l y - n u m b e r e d f i n g e r l i n g f i s h tags. Breeding performance was noted by p a l p a t i n g male t e s t e s and o b s e r v i n g the c o n d i t i o n of v a g i n a l openings and mamillaries of the females. The best value f o r p o p u l a t i o n s i z e i s the minimum number of animals known to be a l i v e (MNA) at each c o n s e c u t i v e two-week i n t e r v a l . H i l b o r n et a l . (1976) have demonstrated by a s i m u l a t i o n model that enumeration tec h n i q u e s provide s u f f i c i e n t l y accurate estimates f o r a t r a p p i n g design i n which 80% or more o f the animals are caught at each sampling time. 93 Douglas f i r seed p o p u l a t i e n s Each experimental g r i d , 91.2 m x 91.2 m, was s y s t e m a t i c a l l y d i v i d e d i n t o 36 (15.2 m x 15.2 m = 231 square ns) p l o t s . In each p l o t , a 0.61 m x 0.61 m quadrat was l o c a t e d i n a s u i t a b l e area f o r seed sampling and recovery (Figure 1.4). For measurement of the responses of deer mice to Douglas f i r seeds, two experimental seed t r i a l s were conducted i n 1975 and one t r i a l i n each of 1976 and 1977. Before each experiment, seed was weighed and packaged a c c o r d i n g t o the amount d e s i r e d per square meter of g r i d (area of g r i d = 8,361.3 sq m). Several samples of 2500 Douglas f i r seeds were weighed and averaged 22.35 g. Using t h i s f i g u r e , I then knew how many g of seeds t o use f o r a given d e n s i t y of seeds. For the f i r s t experiment, I placed a known d e n s i t y of seed i n each of f o u r (0.093 sg m) u n i t s i n a seed-sampling guadrat. The r e s t of the a l l o t t e d seed was then spread by hand as u n i f o r m l y as p o s s i b l e over the r e s t of the area of that p l o t . Care was taken not to a c c i d e n t a l l y throw more seed i n t o the sampling guadrat d u r i n g t h i s seed d i s p e r s a l . Sampling was then conducted at two-week i n t e r v a l s f o r the next s i x weeks. Twelve quadrats and one of f o u r (0.093 sg m) u n i t s i n each quadrat were randomly chosen f o r sampling each week. No quadrat was sampled more than once i n t h i s t r i a l . L i t t e r samples were c o l l e c t e d from each sampling u n i t and packaged f o r l a t e r a n a l y s i s . Whole and eaten seeds were f i l t e r e d out by i n s p e c t i o n and u s i n g d i f f e r e n t s i z e d screens. The next three experiments were i d e n t i c a l to the f i r s t t r i a l i n a l l r e s p e c t s except that 25 quadrats were randomly 94 c h o s e n f o r e a c h g r i d . l o c a t i o n o f t h e one or more s e e d s i n a 0.093 sg m u n i t was marked by wooden t o o t h p i c k s . T h e s e m a r k e r s were p l a c e d a p p r o x i m a t e l y 0.5 cm f r o m e a c h s e e d . E g u a l d e n s i t i e s o f s e e d were p l a c e d i n a d j a c e n t 0.CS3 s g m u n i t s , w h i c h c o n t a i n e d no marked s e e d s . R e m a i n s o f e a t e n D o u g l a s f i r s e e d s were removed e a c h week f o r e v e n t u a l i d e n t i f i c a t i o n o f t h e p r e d a t o r . Whole s e e d s were l e f t i n p l a c e . The r a t e o f d i s a p p e a r a n c e o f t h e s e s e e d s was ray m e a s u r e o f p r e d a t i o n r a t e . The means, s t a n d a r d e r r o r s , and 35% c o n f i d e n c e l i m i t s f o r t h e s e e d t r i a l s a r e l i s t e d i n A p p e n d i x 3.1. I n t h e f o u r t h e x p e r i m e n t a l t r i a l ( 1 9 7 7 ) , a p l a s t i c c o v e r was p l a c e d e v e r e a c h g u a d r a t on a g r i d . T h e s e c o v e r s p r e v e n t e d r a i n f r o m d i s t u r b i n g t h e s e e d - s a m p l i n g a r e a s b u t w e re p r o p p e d up t o a l l o w m i c e and any e t h e r p o t e n t i a l s e e d p r e d a t o r s f r e e a c c e s s . They were p l a c e d on t h e g r i d s a t l e a s t o n e week b e f o r e t h e s e e d e x p e r i m e n t b e g a n . I p l a c e d one s e e d - f a l l t r a p i n a c e n t r a l p o s i t i o n on e a c h g r i d t o m e asure p o t e n t i a l n a t u r a l s e e d - f a l l d u r i n g t h e s e e x p e r i m e n t s . T h e s e t r a p s were 0.37 s g m i n a r e a and composed o f a f r a m e box (2.5-cm x 7.5-cm s i d e s ) . Window s c r e e n (14 by 18 mesh) c o v e r e d t h e b a s e w i t h 1 cm mesh h a r d w a r e c l o t h on t h e t o p , w h i c h a l l o w e d s e e d s t o f a l l i n t o t h e t r a p . P r e d a t i o n G e n e r a l i n f o r m a t i o n a b o u t t h e d i r e c t e f f e c t o f p r e d a t i o n by d e e r m i c e on D o u g l a s f i r s e e d s h a s been o b t a i n e d f r o m c o l l e c t i o n o f t h e r e m a i n s o f e a t e n s e e d s and a n a l y s i s o f s t o m a c h c o n t e n t s f r o m mice t r a p p e d i n a r e a s w i t h t w o d i f f e r e n t s e e d d e n s i t i e s . Two 0.42-ha s n a p - t r a p g r i d s (S-1 and S-2) , l o c a t e d i n t h e 95 f o r e s t , had 30 t r a p s t a t i o n s at 15.2-m i n t e r v a l s marked by f l a g g i n g tape and s t r i n g . Three snap-traps b a i t e d with peanut b u t t e r were placed i n a 2-m r a d i u s of each s t a t i o n . Traps were set on day 1 and checked on days 2 and 3 and then removed. These g r i d s were seeded ( i n an i d e n t i c a l manner to the seeding of l i v e - t r a p g r i d s ) with 540,000 Douglas f i r seeds on August 14, 1975. During the f o l l o w i n g week, August 19-21, a l l mice were removed and f r o z e n f o r subseguent stomach a n a l y s e s . One month l a t e r , September 19-21, both g r i d s were again snap-trapped and a l l mice were f r o z e n f o r l a t e r autopsy. Nine l i t t e r samples were c o l l e c t e d from sampling guadrats f o r e s t i m a t i o n of number of seeds/ha at t h i s time. These quadrats were l o c a t e d i n a l t e r n a t e 232.3 sq m p l o t s and were i d e n t i c a l i n c o n f i g u r a t i o n to those on l i v e - t r a p g r i d s . One (0.093 sq m) u n i t was randomly chosen f o r sampling i n each guadrat. The number of Douglas f i r seed integuments found i n each stomach was recorded f o r a l l mice captured on snap-trap g r i d s -Seed integuments were i d e n t i f i e d by comparison with the stomach contents of a l a b mouse f e d e x c l u s i v e l y on Douglas f i r seeds. B a d i o a c t i v e l y - t a g g e d seed In August 1976, two 0.10-ha g r i d s (B-C and fi-F) were e s t a b l i s h e d i n f o r e s t and c l e a r c u t h a b i t a t s . Each g r i d had cine trap s t a t i o n s (3x3) l o c a t e d a t 15.2-m i n t e r v a l s with two Longworth l i v e - t r a p s per s t a t i o n . _ The t r a p s were b a i t e d with peanut b u t t e r and P u r i n a l a b chow and had c o t t o n f o r bedding. These g r i d s were f i r s t trapped on the n i g h t s of August 22-23, 1976, and a l l s m a l l mammals were removed except f o r deer mice, which were ear-tagged with s e r i a l l y - n u m b e r e d f i n g e r l i n g f i s h 96 tags- B a d i o a c t i v e l y - t a g g e d seed (ca. 400) and normal untagged seed (20,000 seeds) were d i s p e r s e d uniformly on each g r i d on August 27- The g r i d s were then trapped again on the n i g h t s of October 4-5 to re c o r d the number o f deer mice present f o l l o w i n g the r a d i o a c t i v e seeding. The l a b o r a t o r y procedure f o r r a d i o a c t i v e l y tagging the Douglas f i r seed was as f o l l o w s : 800 c l e a n seeds were soaked f o r two hours i n 15 ml 0.5fl BCl and 10 m i l l i C u r i e s c f Scandium-46. They were d r i e d under a fume hood f o r 24 hours and were then ready f o r d i s p e r s i n g i n t o the f i e l d with the untagged seed. Buried i n d i v i d u a l seeds down to a depth of one meter, c o u l d be e a s i l y detected with a c r y s t a l s c i n t i l l a t i o n counter (Thyac V i c t o r e e n I I I model) equipped with a gamma s c i n t i l l a t i o n probe. The c r y s t a l s c i n t i l l a t i o n counter with an audio t r a n s m i t t e r was used t o f i n d caches of seeds i n a s t r i p about 20 m wide on the o u t s i d e of each g r i d area on September 9 and again around the f o r e s t g r i d on September 15. I t was assumed that a t l e a s t one r a d i o a c t i v e seed would be i n c l u d e d i n any l a r g e caches s i n c e the r a t i o o f tagged to untagged seeds was 1:50, and a l l seeds were u n i f o r m l y d i s t r i b u t e d over the g r i d a r e a . To determine whether the tagged seeds were d i s t a s t e f u l , I f e d approximately 800 seeds to two deer mice i n the l a b o r a t o r y . A l l seeds were consumed a f t e r f i v e days with no apparent harmful e f f e c t s t o the animals. I n v e r t e b r a t e p o p u l a t i o n s During September and October 1977, f i v e r o dent-proof e x c l o s u r e s were l o c a t e d i n the f o r e s t and at each of the Burn and Slash study areas. The e x c l o s u r e s were 0.37 s q . m i n area 97 and 15 cm i n h e i g h t . They were covered with 0.8-cm mesh hardware c l o t h which, on the s i d e s , extended 5 cm i n t o the ground. I n v e r t e b r a t e s were thus a b l e to move i n and out of the a r e a , but rodents were e f f e c t i v e l y excluded. One Douglas f i r seed was placed i n each of the 4 (0.093 sg m) u n i t s with i t s l o c a t i o n marked by a t o o t h p i c k . T h i s d e n s i t y of seeds (0.81 kg/ha) was e q u i v a l e n t t o the lowest d e n s i t i e s used i n my experimental seeding t r i a l s and was s i m i l a r t o t h a t used i n r e f o r e s t a t i o n programs. S u r v i v a l o f seeds was then checked every two weeks over a 4-week per i o d . l a b o r a t o r y s t u d i e s From Hay;to November 1977 and March t o May 1978, the number of Douglas f i r seeds eaten and/or taken by i n d i v i d u a l deer mice was determined i n a n a t u r a l environment room at the Animal Care Center, D.B.C. Two rooms were used, each was 18.6 sg m i n area. Ten seed-sampling quadrats (0-37 sq m i n area) were e s t a b l i s h e d . A known d e n s i t y of seeds was p l a c e d i n one or mere -of the f o u r (0.0S3 sq m) u n i t s i n a quadrat and then the r e s t of the a l l o t t e d seed was spread u n i f o r m l y around the room, care being taken not to put more seed by a c c i d e n t on the sampling areas. The s u r v i v a l of the seeds was then recorded 24 hours l a t e r -I n d i v i d u a l male mice were t e s t e d o n l y once f o r a 24-hour p e r i o d f o l l o w i n g a t l e a s t 2 days a d a p t a t i o n to the environment room- Water and l a b chow were always a v a i l a b l e except during an experiment, when only water was a v a i l a b l e . A l t e r n a t i v e food seed t r i a l s S e v e r a l samples of 10 00 sunflower seeds and 100 0 oat k e r n e l s were weighed with the mean value r e p r e s e n t i n g that given 98 number o f seeds. T h i s value was used as a m u l t i p l e t o determine the number of seeds by weight f o r each o f the 36 p l o t s on a g r i d . These seeds, i n v a r i o u s combinations with Douglas f i r , were d i s t r i b u t e d and marked on the e x p e r i m e n t a l g r i d s i n a manner i d e n t i c a l t o t h a t i n the Douglas f i r seed experiments d e s c r i b e d p r e v i o u s l y . The r a t i o s with sunflower seeds and Douglas f i r were 7:1, 5:1,: 3:1, and 0: 1 ( c o n t r o l ) . The r a t i o s with oats and Douglas f i r were 7:1 and 0:1 ( c o n t r o l ) . The combination of 2 a l t e r n a t i v e foods were i n r a t i o s of 3:3:2 and 5:2:1 (sunflower:oats:Douglas f i r ) . Three a l t e r n a t i v e food seed t r i a l s were conducted i n 1S76 and f o u r t r i a l s were done i n 1977. To determine the adequacy of sampling with 25 guadrats (50 sampling u n i t s ) , I doubled the number of quadrats on a 7:1 sunflower to Douglas f i r c l e a r c u t g r i d i n experiments i n August and November 1977. In August, the p r o p o r t i o n of Douglas f i r s u r v i v i n g a f t e r 2 weeks was 0.09 f o r both sampling schemes (n=100 SE=0.04; n=50 SE=0.04), and the p r o p o r t i o n of sunflower s u r v i v i n g was i d e n t i c a l a t 0.0. In November, the p r o p o r t i o n of Douglas f i r s u r v i v i n g was 0.65 (n=100 SE=0.05) compared with 0.56 (n=50 SE=0.07), and the p r o p o r t i o n of sunflower seed s u r v i v i n g was 0.63 (n=100 SE=0.07) versus 0.54 (n=50 SE=0.09). Thus, i t appeared the sampling scheme used i n these seed experiments was adequate f o r determining the amounts of seed s u r v i v i n g and taken o r eaten by deer mice. 99 RESULTS The data composing the responses of deer mice to v a r y i n g seed d e n s i t y , presented i n t h i s chapter, are from the f o r e s t g r i d s . I d e n t i c a l experiments were conducted on the c l e a r c u t g r i d s . However, owing to the nature of the t e r r a i n on logged a r e a s , the seed-sampling quadrats were l o c a t e d i n open areas f a v o u r a b l e t o seed recovery. Consequently, p r e d a t i o n by seed-e a t i n g b i r d s such as the dark-eyed junco and song sparrow i n these open areas, r e s u l t e d i n a f a i l u r e to s u c c e s s f u l l y sample f o r and measure seed consumption by deer mice. The f o r e s t g r i d s were unaffected by any observed r e s i d e n c e or seed p r e d a t i o n by b i r d s and provided r e l i a b l e responses of deer mice to the given range of seed d e n s i t i e s . Since the f o r a g i n g behaviour of deer mice with r e s p e c t to Douglas f i r seeds i s u n l i k e l y to d i f f e r between h a b i t a t s (the source r e g i o n o f mice c o l o n i z i n g logged areas i s o b v i o u s l y the f o r e s t ) , the r e s u l t s o b t a i n e d from the f o r e s t experiments a r e e q u a l l y a p p l i c a b l e to c l e a r c u t areas. The f o r e s t allowed study o f deer mouse-seed responses without c o m p l i c a t i n g i n t e r a c t i o n s from other p r e d a t o r s . Other s m a l l mammal s p e c i e s such as shrews (Sorex spp.) and v o l e s IClethriononmys q a p p e r i , Microtus oregOni) were at very low d e n s i t i e s at a l l times and n e i t h e r group i s p r i m a r i l y a seed e a t e r . T r a p p a b i l i t y The enumeration of deer mice i n experimental and c o n t r o l p o p u l a t i o n s i s based on the assumption that most of the i n d i v i d u a l s i n a g i v e n p o p u l a t i o n are captured. Maximum t r a p p a b i l i t y has been d e f i n e d by Krebs et a l . (1976) as 100 f o l l o w s : t r a p p a b i l i t y ^ No. a c t u a l l y caught at time i / No. known to fee present a t time I T h i s method i n c l u d e s a l l c a p t u r e s and t h e r e f o r e , tends to bias upwards the t r a p p a b i l i t y estimate. Minimum unweighted t r a p p a b i l i t y i s a l e s s biased estimate s i n c e i t e l i m i n a t e s f i r s t and l a s t captures and hence, a l l mice caught only once c r t s i c e . T h i s estimate of t r a p p a b i l i t y p r o v i d e s only one value f o r each i n d i v i d u a l r e g a r d l e s s of how long i t l i v e s and so i s not i n f l u e n c e d by animals with long capture h i s t o r i e s . Both of these estimates f o r the p o p u l a t i o n s during each of the experimental p e r i o d s i n 1975-77 a r e presented i n Table 3.1. as expected, i n most cases maximum t r a p p a b i l i t y was h i g h e r than minimum unweighted t r a p p a b i l i t y and was u s u a l l y above 70%. In g e n e r a l , minimum unweighted t r a p p a b i l i t y was above 80% except d u r i c g 1976-77 on g r i d s B, E, and P. In 1977, the c o n t r o l p o p u l a t i o n a l s o had s l i g h t l y lower t r a p p a b i l i t y comparable to t h a t cf the experimental animals. In some i n s t a n c e s , there was l a r g e v a r i a t i o n between the sexes f o r a given experiment, which may be due to the animals not e n t e r i n g the t r a p s because of the Douglas f i r seeds p r o v i d e d . However, i n the p o p u l a t i o n s exposed to the higher seed d e n s i t i e s , both sexes were more trappable than mice on areas with lower d e n s i t i e s of seeds. If food were a f f e c t i n g t r a p p a b i l i t y , i t s e f f e c t should have been most p r e v a l e n t a t the higher d e n s i t i e s of seed. 101 Experimental seeding with Douglas f i r seed Seed consumption I n s p e c t i o n of stomach contents and the consumption of seeds over time on the experimental seed g r i d s provided d i r e c t evidence t h a t the deer mouse eats Douglas f i r seeds a f t e r s e e d i n g. Table 3.2 presents the mean number of seeds per stomach on g r i d S-1 over time. One week a f t e r seeding the snap-tr a p g r i d s , the mean number of seed integuments per f u l l stomach was 50.1. In a d d i t i o n , s e v e r a l subsamples from each of the f u l l stomachs of deer mice from g r i d S-2 i n d i c a t e d t h a t 78.5% (11 of 14 stomachs) c o n t a i n e d almost e x c l u s i v e l y endosperm and integuments of Douglas f i r seeds. One month l a t e r , the average number of seeds per stomach was s t i l l as high (63.5) as t h a t at a much lower seed d e n s i t y on g r i d S-1. These r e s u l t s i n d i c a t e that deer mice were indeed t a k i n g and e a t i n g Douglas f i r seeds and that they continued to do so more than f o u r weeks a f t e r the seed had been d i s p e r s e d on the g r i d . Mice were probably e a t i n g seed from that d i s t r i b u t e d on the g r i d as w e l l as that from caches made over the pr e v i o u s month a t t h i s very high d e n s i t y of c o n i f e r seed. The cumulative number o f seeds taken per hectare a t f o u r seed d e n s i t i e s d u r i n g the s i x weeks a f t e r each seeding experiment i n 1975 are i l l u s t r a t e d i n F i g u r e 3.1. The h i g h e s t r a t e of seed consumption at a l l d e n s i t i e s was duri n g the f i r s t two weeks a f t e r s e e d i n g i n both experiments. An apparent exception was the number of seeds taken i n the f i r s t t r i a l , which showed a continued high r a t e of consumption d u r i n g the t h i r d and f o u r t h weeks. However, the sample a t t h i s time 102 probably gave an o v e r e s t i m a t e , s i n c e the cumulative number o f seeds taken decreased at the f i n a l sampling p e r i o d . Consumption did not exhaust the t o t a l number of seeds on any g r i d during the s i x seeks of each experimental t r i a l . There appeared to be a d e n s i t y c f seed below which the mice reduced t h e i r p r e d a t i o n . T h i s was p a r t i c u l a r l y e v ident at the lowest d e n s i t y i n t r i a l no. 1 and the two lowest d e n s i t i e s i n t r i a l no. 2. The p a t t e r n of highest r a t e of seed consumption dur i n g the f i r s t two weeks f o l l o w i n g seeding was i d e n t i c a l i n a l l subseguent seeding t r i a l s i n 1976-77. F i g u r e 3.1 a l s o i n d i c a t e s t h a t the two d i f f e r e n t sampling techniques gave very s i m i l a r r e s u l t s . The l i t t e r samples from 12 guadrats i n t r i a l no. 1 and the seeds marked by t o o t h p i c k s i n 25 guadrats i n the second t r i a l , produced consumption curves which were almost i d e n t i c a l . The second method was adopted f o r use i n the remaining seed experiments i n 1976-77. B a d i o a c t i v e l y - t a g g e d seed The r e s u l t s from the d i s p e r s a l of r a d i o a c t i v e l y - t a g g e d seeds are shown i n Table 3.3. In the f o r e s t , 1U of 17 l o c a t i o n s where seeds or seed fragments were found had only one whole seed ( r a d i o a c t i v e ) , whereas on the c l e a r c u t , 2 of 9 caches had only one whole seed; the other 7 had the remains of up to f i v e seeds. These fragmented seeds were opened i n a manner c h a r a c t e r i s t i c of deer mice (Lawrence and l e d i s k e 1962). No t y p i c a l rodent caches of a number o f seeds were recorded from on the g r i d area. H a d i a t i o n on the g r i d s came from whole and eaten r a d i o a c t i v e seeds present from the o r i g i n a l d i s t r i b u t i o n . A s i n g l e cache i n the f o r e s t had 83 whole seeds, which may r e f l e c t the a c t i v i t y o f 103 a Northwestern chipmunk (Eutamias agio en us) observed at the a r e a . P r i o r t o seeding, a t o t a l of f i v e deer mice was captured on the c l e a r c u t g r i d and t e n animals on the f o r e s t g r i d . F ollowing seeding, f i v e mice (3 were recaptures) were captured on the c l e a r c u t and the d e n s i t y on the f o r e s t g r i d was nine animals (5 were r e c a p t u r e s ) . These d e n s i t i e s were comparable t o those on c o n t r o l g r i d s operated i n both h a b i t a t s d u r i n g the same time p e r i o d as part o f another experiments They r e p r e s e n t an average number of deer mice f o r f o r e s t and c l e a r c u t h a b i t a t s i n c o a s t a l B r i t i s h Columbia. I n v e r t e b r a t e s To determine the extent of p r e d a t i o n on Douglas f i r seeds by i n v e r t e b r a t e s , I followed the s u r v i v a l o f seeds i n rodent-proof e x c l o s u r e s . In the f o r e s t , 100% (n=20) of the Douglas f i r seeds remained a f t e r 2 weeks and 95% a f t e r f o u r weeks. a t the Slash study area, 95% (n=20) of t h e seed was present a f t e r both 2 and 4 weeks. At the Burn, there was evidence of shrews and/or mice e n t e r i n g some of the e x c l o s u r e s and e a t i n g seed. S i n c e the seed responses were measured i n the f o r e s t 2 weeks a f t e r seeding i n each experimental t r i a l , the e f f e c t of i n v e r t e b r a t e s p r e y i n g upon Douglas f i r seeds was almost n e g l i g i b l e . I s h a l l a l s o assume t h a t i n v e r t e b r a t e p r edation on seeds was n e g l i g i b l e i n the 1976-77 a l t e r n a t i v e food experiments. Responses of deer mice t o Douglas f i r seeds The response of numbers of deer mice to varying d e n s i t i e s of Douglas f i r seeds i n the f o r e s t i s i l l u s t r a t e d i n F i g u r e 3.2. T o t a l numbers (MUA - minimum number of animals known t o be a l i v e ) over a range of seed d e n s i t i e s and the c o n t r o l s are 104 shewn. These r e s u l t s are from the f i r s t two weeks a f t e r seeding, which corresponds t o the h i g h e s t r a t e s of consumption on a l l g r i d s . There was very l i t t l e d i f f e r e n c e i n the number of animals at the f i r s t f o u r seed d e n s i t i e s . There was then an i n c r e a s e i n d e n s i t y o f mice which l e v e l l e d o f f a t 860,000 seeds/ba. The response of number of new animals t o seed d e n s i t y i s shown i n F i g u r e 3.3. These data i n c l u d e only the f i r s t two weeks of each seeding experiment* There was an i n c r e a s e i n new animals with i n c r e a s i n g seed d e n s i t y up to 430,000 seeds/ha. The number of r e c r u i t s then tended to l e v e l o f f and even perhaps d e c l i n e a t the higher seed d e n s i t i e s . Thus, t h e r e was an upper l i m i t t o the t o t a l number o f mice t h a t could l i v e cn a given area even when the environment was s a t u r a t e d with f o o d . The number o f seeds taken per mouse per day i n the f o r e s t i s presented i n F i g u r e 3.4 (raw data given i n Appendix 3.2) f o r the f i r s t two weeks a f t e r seeding on each experimental g r i d . The data f o r the c l e a r c u t i n c l u d e d seed p r e d a t i o n by unknown d e n s i t i e s of chipmunks and s e e d - e a t i n g b i r d s as w e l l as deer mice. Consequently, the response i n the f o r e s t g i v e s a much more accurate r e p r e s e n t a t i o n of changes i n the numbers of seeds eaten by mice with i n c r e a s i n g seed d e n s i t y . The i n c r e a s e i n consumption with seed d e n s i t y s t a r t e d to l e v e l o f f a t 430,000 seeds/ha. In the f i e l d , consumption i n c r e a s e d again at 860,000 seeds/ha and then reached another p l a t e a u at a d e n s i t y of 1,075,000 seeds/ha. However, the response of deer mice to a range of seed d e n s i t i e s i n a simulated f o r e s t environment (Figure 3.5) was s i m i l a r t o t h a t obtained i n the f i e l d up t o 105 a p p r o x i m a t e l y 860,000 s e e d s / h a ( s e e F i g u r e 3 . 4 ) . The r a n g e o f v a l u e s was s i m i l a r a t e a c h d e n s i t y o f s e e d s i n t h e s e l a b o r a t o r y s e e d t r i a l s . T h e r e f o r e , t h e i n c r e a s e i n c o n s u m p t i o n a t 860,000 s e e d s / h a i n t h e f i e l d may be due t o t h e p r e s e n c e o f a n o t h e r s e e d p r e d a t o r . One o r two D o u g l a s s q u i r r e l s ( T a m i a s c i u r u s d o u q l a s i i ) were o b s e r v e d on some o f t h e e x p e r i m e n t a l g r i d s w h i c h had d e n s i t i e s g r e a t e r t h a n 430,000 s e e d s / h a . I t i s p o s s i b l e t h a t t h e s e s q u i r r e l s f o u n d i t a d v a n t a g e o u s t o l e a v e t h e i r n o r m a l f o r a g i n g i n t r e e s and f o r a g e f o r c o n i f e r s e e d s on t h e f o r e s t f l o o r a t t h e s e h i g h d e n s i t i e s . T h u s , t h e number o f s e e d s t a k e n a n d t o t a l n umber.of d e e r mice s t a b i l i z e d a t a b o u t 860,000 s e e d s / h a . I t h e n a t t e m p t e d t h e a l t e r n a t i v e s e e d e x p e r i m e n t s a t a c o m b i n e d s e e d d e n s i t y o f 860,GOO s e e d s / h a (8 s e e d s / s g f t o r 86 s e e d s / s g m). The number o f D o u g l a s f i r s e e d s i n t h e c o m b i n e d s e e d r a t i o s was u s u a l l y l e s s t h a n o r e q u a l t o 107,593 s e e d s / h a (1 s e e d / s q f t o r 11 s e e d s / s q m) b e c a u s e o f t h e v e r y h i g h c o s t o f t h i s c o n i f e r s e e d f o r r e f o r e s t a t i o n . The l o w e r c o s t a l t e r n a t i v e f o o d s ( s u n f l o w e r s e e d s and o a t s ) c o m p r i s e d t h e m a j o r i t y o f s e e d s i n t h e s e e d i n g e x p e r i m e n t s . E x p e r i m e n t a l s e e d i n g w i t h D o u g l a s f i r s e e d and a l t e r n a t i v e f o o d s The r e s u l t s o f e x p e r i m e n t a l s e e d i n g w i t h D o u g l a s f i r a n d s u n f l o w e r s e e d i n a u n i f o r m d i s t r i b u t i o n i n t h e f o r e s t a nd c l e a r c u t i n A u g u s t 1976 a r e p r e s e n t e d i n F i g u r e 3.6. I n t h e f o r e s t , a f t e r 2 weeks, n e a r l y 6 0 % o f t h e D o u g l a s f i r s e e d ( d i s t r i b u t e d w i t h s u n f l o w e r ) r e m a i n e d c o m p a r e d w i t h o n l y 10% o f t h e D o u g l a s f i r s e e d s ( d i s t r i b u t e d a l o n e ) . a f t e r 4 w e e k s , a p p r o x i m a t e l y 30% o f t h e D o u g l a s f i r s e e d ( w i t h s u n f l o w e r ) 106 remained, but very l i t t l e sunflower seed was l e f t a t t h i s time. On the c l e a r c u t , a g r e a t e r number of Douglas f i r seeds s u r v i v e d a f t e r 2 weeks, but very l i t t l e sunflower seed was l e f t at t h i s time. There was v i r t u a l l y no sunflower seed l e f t a t week 1 of t h i s experiment. percentage s u r v i v a l o f Douglas f i r seed and oats f o r the f o r e s t and c l e a r c u t i n l u g u s t 1976 are g i v e n i n Fig u r e 3.7. There was g e n e r a l l y poor s u r v i v a l o f Douglas f i r seed when combined with oats i n t h i s experiment. T h i s i s f u r t h e r i l l u s t r a t e d i n F i g u r e 3.8, which shows percentage s u r v i v a l of Douglas f i r seed when combined with both sunflower seeds and oats i n the f o r e s t and on the c l e a r c u t d u r i n g the same p e r i o d . In the f o r e s t , sunflower seeds were p r e f e r e n t i a l l y chosen ever oats and consequently were n e a r l y exhausted a f t e r 4 weeks. S u r v i v a l of Douglas f i r seed was very good i n week 2 and then d e c l i n e d to 30% a t week 4, when a l t e r n a t i v e food sources had been depleted. On the c l e a r c u t , s u r v i v a l of Douglas f i r was g r e a t e r than 20% a f t e r 2 weeks but d e c l i n e d at week 4, as d i d the a l t e r n a t i v e food sources. The e f f e c t of clumping a l t e r n a t i v e food sources (sunflower seed or o a t s i n two d i f f e r e n t l o c a t i o n s on a g r i d ) on the s u r v i v a l of u n i f o r m l y spread Douglas f i r seed was measured i n September-October 1976. A f t e r 2 weeks, s u r v i v a l was s i a i l a r to t h a t c f c o n t r o l Douglas f i r f o r both the f o r e s t and c l e a r c u t . Consequently, a l t e r n a t i v e seeds should be spread u n i f o r m l y with Douglas f i r seed, as was done i n the p r e v i o u s experimental t r i a l s . The r e s u l t s of experimental s e e d i n g with Douglas f i r and 107 sunflower seed i n a uniform d i s t r i b u t i o n cn the c l e a r c u t i n November 1976 are i l l u s t r a t e d i o F i g u r e 3-9- A f t e r 2 weeks, the r e was 50% and 40% r e s p e c t i v e l y of the Douglas f i r seed (with sunflower) remaining compared with c o n t r o l Douglas f i r by i t s e l f - The same d e n s i t y of sunflower seed was u n i f o r m l y d i s t r i b u t e d ( s e q u e n t i a l seeding) on one of the experimental areas a f t e r the second week. S u r v i v a l o f Douglas f i r seed a t week 4 dropped 10% on the g r i d with s e q u e n t i a l seeding o f sunflower, which was the same as the d e c l i n e (from 50% to 40%) on the other experimental g r i d . Very l i t t l e sunflower seed remained on e i t h e r g r i d a t t h i s time. Thus, i t appeared t h a t s e q u e n t i a l seeding d i d not i n c r e a s e s u r v i v a l of Douglas f i r beyond that already o b t a i n e d with the i n i t i a l seeding of sunflower. Percentage s u r v i v a l of Douglas f i r and sunflower seed i n a s p r i n g seeding experiment from March to May 1977 i s given i n F i g u r e 3.10. At week 2, th e r e was e x c e l l e n t s u r v i v a l of Douglas f i r with sunflower compared with c o n t r o l Douglas f i r by i t s e l f . A f t e r the s e g u e n t i a l seeding, s u r v i v a l of Douglas f i r seed continued to be much higher than i t was on the c o n t r o l . However, there appeared to be l i t t l e d i f f e r e n c e between the two sets of g r i d s with r e s p e c t to s e q u e n t i a l seeding at week 2. S u r v i v a l was s l i g h t l y higher i n weeks 6 and 8 cn the g r i d s with t h i s second seeding. The r e s u l t s o f t h i s same experiment r e p l i c a t e d i n the f o r e s t are presented i n F i g u r e 3.11. As recorded on the c l e a r c u t , s u r v i v a l of Douglas f i r seed was e x c e l l e n t when d i r e c t - s e e d e d with sunflower i n the s p r i n g . S e g u e n t i a l seeding 108 a t week 2 d i d n o t i m p r o v e s u r v i v a l r e l a t i v e t o t h e g r i d s w h i c h were s e e d e d o n l y o n c e w i t h s u n f l o w e r . I n summary, t h i s s p r i n g s e e d i n g e x p e r i m e n t r e s u l t e d i n e x c e l l e n t s u r v i v a l o f D o u g l a s f i r s e e d on t h e c l e a r c u t a t a l e v e l a t l e a s t f o u r t i m e s t h a t o f t h e c o n t r o l t h r o u g h o u t t h e e i g h t weeks. S u r v i v a l o f D o u g l a s f i r ( w i t h s u n f l o w e r ) on t h e f o r e s t g r i d s was o v e r t e n t i m e s h i g h e r t h a n on t h e c o n t r o l f o r t h e d u r a t i o n o f t h e e x p e r i m e n t . I n an a t t e m p t t o l o w e r t h e number o f s u n f l o w e r s e e d s t o be m i x e d w i t h D o u g l a s f i r and s t i l l s u c c e s s f u l l y c o n t r o l p r e d a t i o n on t h e c o n i f e r s e e d , I c a r r i e d o u t an e x p e r i m e n t a l s e e d i n g i n June 1977 w i t h r a t i o s o f 5:1 and 3:1 s u n f l o w e r t o D o u g l a s f i r . S u r v i v a l c f D o u g l a s f i r s e e d s was v e r y p o o r on a l l g r i d s a t t h e s e r a t i o s . T h u s , t h e 7:1 r a t i o o f s u n f l o w e r t o D o u g l a s f i r gave t h e b e s t r e s u l t s i n l o w e r i n g t h e r e s p o n s e o f d e e r m i c e t o t h e s e c o n i f e r s e e d s . O s i n g a r a t i o o f 7:1, I t r i e d a m i x t u r e o f 5 s u n f l o w e r : 2 o a t s : 1 D o u g l a s f i r i n t h e n e x t e x p e r i m e n t i n J u l y 1977. By u s i n g two a l t e r n a t i v e f o o d s o u r c e s , I h o p e d t h i s r a t i o w o u l d i m p r o v e s u r v i v a l o f D o u g l a s f i r b e y o n d t h a t a l r e a d y o b t a i n e d . The 5:2:1 r a t i o p r o d u c e d s l i g h t l y b e t t e r s u r v i v a l o f D o u g l a s f i r c o m p a r e d w i t h t h a t f o r t h e 7:1 r a t i o , b u t a l l e x p e r i m e n t a l g r i d s showed p o o r e r s u r v i v a l o v e r a l l t h a n t h a t i n t h e s p r i n g (1977) o r l a t e f a l l (1976) s e e d i n g e x p e r i m e n t s . T h u s , t h i s same e x p e r i m e n t was r e p e a t e d a t a more a p p r o p r i a t e t i m e o f y e a r i n November 1977. The r e s u l t s o f s e e d i n g w i t h o a t s a nd s u n f l o w e r i n l a t e f a l l a r e shown i n F i g u r e 3.12. T h e r e was e x c e l l e n t s u r v i v a l o f 109 Douglas f i r i n both experimental treatments- This was comparable to the r e s u l t s obtained i n the s p r i n g seeding experiment. There appeared to be no measurable n a t u r a l f a l l of Douglas f i r seeds i n the s e e d - f a l l t r a p s on any of the g r i d s d u r i n g 1975-7 7. DISCUSSION The use o f a l t e r n a t i v e foods t o lower c o n i f e r seed predation by deer mice has been based on a c c u r a t e l y measuring the responses o f deer mice to a range of Douglas f i r seed d e n s i t i e s . In a l l response measurements and c a l c u l a t i o n of percentage s u r v i v a l v a l u e s, I have assumed that seeds removed from sampling quadrats were e i t h e r taken out of the guadrat and eaten or were cached and eaten l a t e r . Regardless of when the seeds were eaten, they were c o n s i d e r e d to be removed from the experimental seed p o p u l a t i o n i n an e q u i v a l e n t manner t o those seeds found as eaten remains. I b e l i e v e t h i s i s a f a i r assumption, because Douglas f i r seeds that were taken and then cached are u n l i k e l y t o germinate even i f they are never eaten-B e s u l t s from my r a d i o a c t i v e s e e d i n g , i n d i c a t i n g t h a t seeds may be moved a great d i s t a n c e , supports the above assumption. The m a j o r i t y of cached seeds were found under stumps and along f a l l e n l o g s , which are t y p i c a l p l a c e s t h a t mice i n h a b i t . The s m a l l p r o p o r t i o n of seeds a c t u a l l y cached suggests that aost seeds taken were soon eaten (at l e a s t at the low seed d e n s i t y of 110 1.92 kg/ha). T o t a l numbers and number of new animals i n c r e a s e d with seed d e n s i t y up to a c e r t a i n l e v e l only. B e f e r r i n g a g a i n t o F i g u r e s 3.4 and 3.5, we see t h a t the number o f seeds taken per mouse per day began to l e v e l o f f at a d e n s i t y of about 430,000 seeds/ha and maintained t h i s response above 860,C0 0 seeds/ha i n the l a b o r a t o r y seed t r i a l s . Since the numbers of animals s t a b i l i z e d at about 860,000 seeds/ha, i t seemed l o g i c a l to t r y a l t e r n a t i v e seed experiments at a combined seed d e n s i t y of about 86 0,000 seeds/ha (8 seeds/sq f t or 86 seeds/sg m). At t h i s d e n s i t y , the t o t a l number o f mice and number of new mice were no l o n g e r i n c r e a s i n g , and the number of seeds taken per mouse per day had reached an upper l i m i t . In a d d i t i o n , Douglas s q u i r r e l s were most p r e v a l e n t on seed g r i d s with d e n s i t i e s g r e a t e r than 860,000 seeds/ha. Thus, I assumed t h i s number o f seeds was considered the best d e n s i t y f o r attempting a l t e r n a t i v e food experiments. The presence of chipmunks and b i r d s on the c l e a r c u t has complicated the measurement of a seed response f o r deer mice. However, the s u c c e s s f u l a l t e r n a t i v e seed experiments used a combined seed d e n s i t y of 860,000 seeds/ha ( r a t i o s of 5:2:1 and 7:1) de r i v e d from the f i e l d data f o r the f o r e s t and t h a t obtained i n the l a b o r a t o r y seed t r i a l s . fts mentioned i n the r e s u l t s , the f o r a g i n g behaviour of deer mice with r e s p e c t to Douglas f i r seeds i s u n l i k e l y t o d i f f e r between h a b i t a t s , and so the seed response measurements i n the f o r e s t should be e g u a l l y a p p l i c a b l e t o c l e a r c u t areas* In g e n e r a l , most a l t e r n a t i v e seed experiments produced b e t t e r r e s u l t s i n the f o r e s t than i n c l e a r c u t areas. However, 111 the e x c e l l e n t s u r v i v a l of Douglas f i r seed was very s i m i l a r i n both h a b i t a t s during the l a t e f a l l of 1976 and the s p r i n g and l a t e f a l l of 1977. a t t h e s e times, secondary seed p r e d a t o r s such as chipmunks and v a r i o u s s p e c i e s of see d - e a t i n g b i r d s were r a r e o r absent (see chapter 4 ) . The success of these a l t e r n a t i v e foods i n suppressing consumption of Douglas f i r seeds by deer mice i s given f u r t h e r credence by the f a c t t h at p o p u l a t i o n s o f Peromyscus maniculatus are a t peak d e n s i t i e s i n the f a l l (see F i g u r e 1.5 and S a d l e i r 1965; Healey 1967; Fordham 1971; Petticrew and S a d l e i r 1974; F a i r b a i r n 1977; and S u l l i v a n 1977). T h i s study has provided some f i e l d as w e l l as l a b o r a t o r y evidence f o r the f u n c t i o n a l response of a g e n e r a l p r e d a t o r , the deer mouse. Solomon (1949) f i r s t a p p l i e d the terms of f u n c t i o n a l and numerical responses to the two-fold nature of the response t o changes i n prey d e n s i t y . H e l l i n g (1959a) demonstrated t h a t deer mice i n pine p l a n t a t i o n s had an S-shaped f u n c t i o n a l response t o the va r y i n g d e n s i t i e s of sawfly cocoons. Tinbergen (1960) has shown the f u n c t i o n a l response of the great t i t to d i f f e r e n t d e n s i t i e s of sawfly l a r v a e , and Hook (1963) demonstrated t h i s same response o f the bay-breasted warbler to spruce hudworm l a r v a e . Hook e t a l . (1960) have a l s o suggested that the great t i t has an S-shaped response to the d e n s i t y o f the bordered white moth (Bupalus s p . ) . The f u n c t i o n a l response to the number of jack pine seeds and s e e d l i n g s destroyed per acre by the meadow vol e ( f l i c r o t u s pennsylvanicus) has been demonstrated by Buckner (1972). The use of a lower p a l a t a b i l i t y a l t e r n a t i v e food (oats) by 112 i t s e l f at a 7:1 r a t i o produced no more than a marginal i n c r e a s e i n s u r v i v a l of Douglas f i r (see F i g u r e 3.7). Shen the two a l t e r n a t i v e foods were compared, sunflower seeds were p r e f e r r e d over oats on a f o r e s t experimental g r i d where only deer mice were present (see F i g u r e 3.8). The combination of sunflower and oats i n a 5:2:1 r a t i o produced the best s u r v i v a l of Douglas f i r . T h i s i l l u s t r a t e d the p o s i t i v e e f f e c t s of a high d e n s i t y and h i g h p a l a t a b i l i t y food mixed with a s l i g h t l y h i g h e r d e n s i t y (than Douglas f i r ) and lower p a l a t a b i l i t y (oats) food (see F i g u r e 3.11). The use of two egual d e n s i t y (higher than Douglas f i r ) and high p a l a t a b i l i t y foods i n a seeding experiment, although not attempted i n t h i s study, should produce an even higher s u r v i v a l of c o n i f e r seed. Changing the d i s t r i b u t i o n of a l t e r n a t i v e food frem uniform or random to clumped during an experimental seed t r i a l i n September 1976, d i d not lower the response of deer mice t o Douglas f i r seeds. Perhaps clumps of a l t e r n a t i v e food at s e v e r a l l o c a t i o n s spread over the area of the g r i d would have produced b e t t e r r e s u l t s . However, ac c o r d i n g to Eeichman (1977) and Eeichman and O b e r s t e i n (1977), s m a l l pocket mice i n a r i d h a b i t a t s found s c a t t e r e d food j u s t as e f f e c t i v e l y as clumped food. S i m i l a r l y , T a y l o r (1977) found t h a t southern grasshopper mice (Onychomys t o r r i d u s ) captured more prey from a d i s p e r s e d d i s t r i b u t i o n than from an aggregated p a t t e r n . I do not know of any i n f o r m a t i o n on the responses of deer mice to d i f f e r e n t d i s t r i b u t i o n s of food r e s o u r c e s . When I provided deer mice with equal amounts of sunflower seed and Douglas f i r seeds i n the experimental rooms at the 113 Animal Care Center, t h e r e was no d i f f e r e n c e i n pr e f e r e n c e i n 2 of 6 t r i a l s . However, i n the other four t r i a l s , the s i c e took at l e a s t twice as much sunflower as Douglas f i r . In l a b o r a t o r y t e s t s f o r determining t h e p r e f e r e n c e of deer mice f o r Douglas f i r or sunflower, Keyes (1978) found no s i g n i f i c a n t d i f f e r e n c e (chi-square at p<.01) when i n d i v i d u a l mice had a c h o i c e of seeds. However, Douglas f i r was p r e f e r r e d t o sunflower (ANOVA -Duncan's M u l t i p l e Range T e s t p=.05) when i n d i v i d u a l mice were allowed t o choose from a mixture o f s i x seeds. As evidenced i n the f i e l d (see F i g u r e 3.8), sunflower was p r e f e r r e d over o a t s , and t h i s d i f f e r e n c e was s i g n i f i c a n t i n both l a b o r a t o r y t e s t s . According t o Reichman (1977), d e s e r t rodents base t h e i r d i e t a r y preferences on energy c o n s i d e r a t i o n s but s t i l l o p t i m i z e t h e i r d i e t s with other seeds (low i n energy) which provide some undefined value such as n u t r i t i o n or moisture. The c a l o r i c content (kcal/gm) of the seeds used i n my study was as f o l l o w s : Douglas f i r 7.13 (Smith 1967); sunflower 6.82 (Mrosovsky 1S66) ; oats 3.90 (Bingham 1977). Thus, from my f i e l d s t u d i e s and some of the l a b experiments, p r e f e r e n c e o f deer mice f o r Douglas f i r and sunflower seeds was approximately equal and g r e a t e r than i t was f o r the other seeds o f f e r e d . T h i s t r e n d corresponds to the r e l a t i v e c a l o r i c c o n t e n t s of the seeds i n much the same manner as d e s c r i b e d by Reichman (1977). Deer mice presumably develop what might be termed an " o l f a c t o r y s e arch image" to e x p l o i t a food source. Howard and Cole (1967), Howard e t a l . (1968), and Howard and Marsh (1970) have provided evidence f o r the use of o l f a c t i o n by deer mice i n d e t e c t i n g food. By the use o f a l t e r n a t i v e foods of varying 114 p a l a t a b i l i t i e s and d e n s i t i e s i n my study, the p r e d a t o r s (deer mice) have switched (Murdoch 1969) t o a new food source with a r e s u l t i n g d e c l i n e i n the number of c o n i f e r seeds eaten. Searching-image f o r m a t i o n ( i n t h i s case, u s i n g o l f a c t i o n ) can be a b e h a v i o u r a l mechanism which c o u l d produce the e f f e c t of s w i t c h i n g (Krebs 1973). For predators which are g e n e r a l i s t s , s w i t c h i n g o p t i m i z e s two processes; forming a search image and being f l e x i b l e i n s e l e c t i n g prey ( C o r n e l l 1976). Such predators form a more f l e x i b l e l e a r n e d search image and C o r n e l l (1976) c o n s i d e r s t h i s the essence o f s w i t c h i n g . Consequently, the g e n e r a l i s t r e t a i n s the e f f i c i e n c y of search image formation as w e l l as the obvious advantage of t a k i n g many prey s p e c i e s . The deer mouse i s c e r t a i n l y a general predator and i s an o p p o r t u n i s t i c omnivore s e l e c t i n g from many d i f f e r e n t prey items i n i t s environment. Sunflower seeds must have reduced the deer mouse's response to Douglas f i r by d e c r e a s i n g i n some way the s t r e n g t h of the s t i m u l u s from the c o n i f e r seed. H o l l i n g (1965) has d i s c u s s e d lowering of the f u n c t i o n a l response when the s t r e n g t h of the s t i m u l u s from the prey was decreased. O l f a c t o r y cues, s i z e , and the very high r e l a t i v e d e n s i t y o f sunflower seed probably a l l i n t e r a c t e d t o switch deer mice from Douglas f i r t o the a l t e r n a t i v e food. Murdoch (1973) has d i s c u s s e d the importance of understanding a predator's response t o more than one prey s p e c i e s and the p o t e n t i a l b e n e f i t s f o r s u c c e s s f u l b i o l o g i c a l c o n t r o l . Of what p r a c t i c a l use, t h e n , are the present r e s u l t s ? I conclude that d e s t r u c t i o n of Douglas f i r seeds (and perhaps 115 other c o n i f e r seeds) i s much reduced by using a l t e r n a t i v e foods of high p a l a t a b i l i t y and r e l a t i v e d e n s i t y . The recommended procedure f o r a p p l y i n g t h i s b i o c o n t r o l technique i n r e f o r e s t a t i o n p r o j e c t s i s d i s c u s s e d i n chapter 5 of t h i s t h e s i s . 116 Fi g u r e 3.1. Cumulative number of seeds taken per ha at four seed d e n s i t i e s d u r i n g the s i x weeks a f t e r each seeding experiment i n 1975. The maximum number of seeds f o r each d e n s i t y i s rep r e s e n t e d by a dashed h o r i z o n t a l l i n e . 860 ,746 O X CO CD Q . C • CD CO CO "D CD CD CO CD _ Q E =3 C CD > -4—* _C0 E =3 o 75CH 600 450H 300 150 430,373 117 9Q0i 750 600i 450-L 300H 15(H 860,746 430,373 107,593 Weeks after seeding 118 F i g u r e 3.2. Responses of numbers o f mice over a range of Douglas f i r seed d e n s i t i e s f o r the study. Each symbol r e p r e s e n t s the response i n d e n s i t y of deer mice (MNA) to the d e n s i t y of seeds on a g r i d . These responses r e p r e s e n t the f i r s t two weeks a f t e r s e e d i ng. T r i a l No. 1 - J u l y 1975; T r i a l No. 2 - August 1975; T r i a l No. 3 - June 1976; T r i a l No. 4 - May to October 1977. .c 3 cr CD CD O O &) (NO O x o O _ L w ^ o o CD O O 00 O o Number of mice per ha t_ -L I\D ro CO r\3 O CO <j) 4^ —1—•—t-Q—C*>01> B>> • 1 t> & ' 1  o o o • o t> > o o o • • CD CD CL c/> "D CD 00 O O o o o o > > 6TT 120 F i g u r e 3.3- Responses of numbers of new mice over a range of Douglas f i r seed d e n s i t i e s . Each symbol r e p r e s e n t s the number of mew animals captured i n r e l a t i o n t o the d e n s i t y of seeds on a g r i d . These responses re p r e s e n t the f i r s t two weeks a f t e r seeding* T r i a l No. 1 - J u l y 1975; T r i a l No- 2 - August 1975; T r i a l No. 3 - June 1976; T r i a l No. 4 - Hay to October 1977. Number of new mice per ha -^er»—&—«»— CO CO —I 1) 1 O IV) 4^ _1 I ; . L_ IV) o o o o c CD 3 O " cr o CD -^  o CO o -U) o CD CD Q. 1 C/) o pe  -o —^  3" CO ro o -X o o L O O CD O O 00 O O © o • o • o o o > TZT 122 F i g u r e 3 . 4 - The number of Douglas f i r seeds taken per mouse per day at d i f f e r e n t seed d e n s i t i e s i n the f o r e s t - Each symbol r e p r e s e n t s the response i n number of seeds taken per mouse per day to a g i v e n d e n s i t y o f seeds on a g r i d - These responses rep r e s e n t the f i r s t t«o weeks a f t e r s e e d i n g . T r i a l No. 1 -J u l y 1975; T r i a l No. 2 - August 1975; T r i a l No. 3 - June 1S76; T r i a l No. 4 - Hay t o October 1977. 220O 2000-1800-1600-1400-1200-1000-800-600 400H 200 o o o A DEER MOUSE DOUGLAS SQUIRREL ? ? 1 2 4 8 12 16 per sq. foot 0 200 400 600 800 1000 1200 1400 1600 1800 per ha x10 N u m b e r o f s e e d s 124 Figure 3 . 5 . The number of Douglas f i r seeds taken per mouse per day at di f f e r e n t seed . densities in a simulated forest environment. Each closed c i r c l e represents the response i n number of seeds taken per mouse per day to a given density of seeds. "O i _ CD a CD CO 13 o E i _ CD d C CD XL CO CO " D CD CD CO 1200H 1000H 800-600H 400H e • • © s 200H 0 1 2 200 4 400 8 600 12 1200 1400 800 1000 Number of seeds 16 1600 1800 per sq. foot , per ha x10" 126 F i g u r e 3.6. Percentage s u r v i v a l of a mixture of Douglas f i r and sunflower seed ccopared with t h a t of c o n t r o l Douglas f i r by i t s e l f . The same p r o p o r t i o n (7 sunflower : 1 Douglas f i r ) was used on one f o r e s t g r i d and one c l e a r c u t g r i d i n August 1976. August 1976 128 F i g u r e 3.7- Percentage s u r v i v a l of a mixture of Douglas f i r and oats compared with that of c o n t r o l Douglas f i r by i t s e l f - The same p r o p o r t i o n (7 oats : 1 Douglas f i r ) was used on one f o r e s t g r i d and one c l e a r c u t g r i d i n August 1976. 129 100 80 -J 60 J 40-J A A A; A A 20 H <U W o C8 > •H > a • CO QJ ca c o M OJ A' A» A» tf Week 0 4 s. k' i A A A A* i ^1 100 H 80 H 60 J 40 H 20 J J p. fl A  A ft U A a  a  a Forest 1 Clearcut X3. rr; A A: . A m . Week 0 August 1976 130 F i g u r e 3.8. Percentage s u r v i v a l of a mixture of Douglas f i r , sunflower seed, and oats compared with t h a t of c o n t r o l Douglas f i r by i t s e l f . The same p r o p o r t i o n was used (3 sunflower : 3 oats : 2 Douglas f i r ) on one f o r e s t g r i d and one c l e a r c u t g r i d i n August 1976. August 1976 132 F i g u r e 3.9. Percentage s u r v i v a l o f a mixture of Douglas f i r and sunflower seed compared with t h a t of c o n t r o l Douglas f i r by i t s e l f . The same p r o p o r t i o n (7 sunflower : 1 Douglas f i r ) was used on both c l e a r c u t g r i d s i n November 1976. The same d e n s i t y of sunflower seed was again d i s t r i b u t e d on one g r i d a f t e r the second week ( s e q u e n t i a l s e e d i n g ) . November 1976 134 F i g u r e 3- 10. P e r c e n t a g e s u r v i v a l o f a m i x t u r e o f D o u g l a s f i r and s u n f l o w e r s e e d c o m p a r e d w i t h t h a t o f c o n t r o l D o u g l a s f i r by i t s e l f . The same p r o p o r t i o n (7 s u n f l o w e r : 1 D o u g l a s f i r ) was u s e d on a l l c l e a r c u t g r i d s i n t h i s e x p e r i m e n t f r o m M a r c h t o May 1977. The same d e n s i t y o f s u n f l o w e r s e e d was a g a i n d i s t r i b u t e d on 2 o f t h e 4 g r i d s a f t e r t h e s e c o n d week ( s e q u e n t i a l s e e d i n g ) . The v a l u e s g i v e n f o r e a c h 2-week p e r i o d a r e t h e a v e r a g e s u r v i v a l o f s e e d f r o m 2 e x p e r i m e n t a l g r i d s . 100H 80" 60 H 40 ' 20 H A , A , A / A , A . A, A ; *1 4 A ; , A , A  A > A > A  A .a; ,a. a Clearcut A A A A A Week 0 i 8 100 H 80 H 60 1 40 H 20 >! A A A A A A A i A A A J: A A A A a 1 f A -Sequential seeding Week March April May 136 Fi g u r e 3.11. Percentage s u r v i v a l of a mixture of Douglas f i r and sunflower seed compared with t h a t of c o n t r o l Douglas f i r by i t s e l f . The same p r o p o r t i o n (7 sunflower : 1 Douglas f i r ) was used cn a l l f o r e s t g r i d s i n t h i s experiment from March t o May 1977. The same d e n s i t y of sunflower seed was again d i s t r i b u t e d on 2 of the H g r i d s a f t e r the second week ( s e q u e n t i a l s e e d i n g ) . The values given f o r each 2-week p e r i o d a re the average s u r v i v a l of seed from two experimental g r i d s . 137 138 F i g u r e 3 . 1 2 . Percentage s u r v i v a l o f a mixture cf Douglas f i r , sunflower seed, and oats compared with t h a t of c o n t r o l Douglas f i r by i t s e l f . The same p r o p o r t i o n (5 sunflower : 2 oats : 1 Douglas f i r ) was used on two g r i d s and a 7 :1 r a t i o of sunflower t o Douglas f i r was used on a t h i r d g r i d oc the c l e a r c u t i n November 1977 . The values g i v e n f o r each 2-week p e r i o d f o r the 5 : 2 : 1 r a t i o are the average s u r v i v a l c f seed from two experimental g r i d s . 140 Table 3.1. Trappability estimates for Peromyscus maniculatus on the six experim-ental grids and one control grid in the forest. Sample size in parentheses. Maximum trappability is the proportion of those known to be alive that are actually caught in a trapping session. Minimum unweighted trappability estim-ates fi r s t and last captures and provides only one value for each individual regardless of how long he lives.  Experimental populations Grid B Grid C Grid D Grid E Males Females Males Females Males Females Males Females Maximum trappability 1975 .84(25) .91(16) .91(23) .88(27) .96(19) .95(8) .98(14) .96(19) 1976 .88(16) .68(19) - .66(17) .83(15) 1977 - - -- - - .81(21) .61(15) Minimum unweighted trappability 1975 .84(14) .74(9) .90(17) .81(14) .89(9) .75(4) .89(9) .85(5) 1976 .88(9) .58(15) - .62(15) .71(12) 1977 - - - - - - .79(18) .64(15) Experimental populations Control population. Grid F Grid P Grid A  Males Females Males Females Males Females Maximum trappability 1975 0.91 (20) 1.00 (17) - - 0.95 (15) 0.99 (17) 1976 - - - - 0.98 (12) 0.97 (15) 1977 - - 0.81 (60) 0.83 (47) 0.73 (41) 0.79 (29) Minimum unweighted trappability 1975 0.57 (10) 1.00 (9) - - 0.89 (14) 0.93 (14) 1976 - - - - 0.97 (8) 0.91 (12) 1977 - — 0.68 (38) 0.75 (33) 0.76 (34) 0.77 (19) 141 Table 3.2. Mean number of seeds per stomach at two d i f f e r e n t seed d e n s i t i e s . Grid M Aug. 19-21 Grid M Sept. 19-21 Seed/density/acre 522,720 53,240 Mean number of seed integuments i n f u l l 50.1 63.1 stomachs Number of f u l l stomachs 9 12 Tota l number of mice 16 15 142 Table 3.3. Number of deer mouse seed caches and proportion of whole and eaten radio-tagged Douglas f i r seeds found adjacent to seeded 0.10 ha forest and clearcut grids. Number of locations One whole Parts of one seed(radiotagged eaten seed . present . . _. (radiotagged) Caches with one seed (whole or eaten) Forest 17 14 1 (83 whole)* Clearcut 9 4 (each with ca. 5 seed fragments) 3 (each with one whole seed and 2-3 seed fragments) * This cache may be from a chipmunk rather than a deer mouse. 143 Appendix 3.1. Mean values, standard errors, and 95% confidence l imi ts for number of seeds eaten and taken per sampling unit(0.093sp.m) . n=no. of sampling units. Douglas f i r seed (2 weeks after seeding)  Experimental T r i a l No. 1 - 1975 Experimental T r i a l No. 2 - 1975 Densitv/ha mean SE 95% C L . Densitv/ha mean SE • 95% C L . 107,593 0.58 0.15 0.25-0.91 107,593 0.75 0.04 0.66-0.84 215,186 1.00 0.25 0.46-1.54 215,186 •1.77 0.04 1.68-1.86 430,373 2.50 0.36 1.71-3.29 430,373 2.68 0.14 2.40-2.96 860,746 2.67 0.59 1.36-3.98 860,746 5.75 0.33 5.07-6.43 Experimental T r i a l No. 3 - 1976 107,593 0.87 0.03 0.81-0.94 n-100 430,373 3.52 0.11 3.30-3.74 n=50 Experimental T r i a l No. 4 - 1977 107,593 0.95 0.02 0.91-0.99 1,075,932 9.46 0.11 9.24-9.68 -.- n=99 n=50-860,746 7.40 0.12 7.16-7.64 1,291,118 8.70 0.31 8.07-9.33 n=50 n=50 860,746 7.54 0.09 7.37-7.71 1,721,491 15.06 0.18 14.69-15.. n=50 n=50 1,075,932 7.70 0.29 7.11-8.29 n=50 144 /Appendix 3.1. (cont'd) Douglas f i r seed and alternative seeds August 1976 Experimental Trial No. 1. Seed densities/ha Douglas f i r Sunflower Oats mean SE 95% CL. mean SE 95% CL. mean SE 2 weeks Forest 7:1 ratio 753,151:107,593 0.58 0.07 0.43-0.73 2.58 0.30 1.98-3.18 n=45 7:1 ratio 753,151:107,593 0.34 0.07 0.20-0.48 3.98 0.34 n=50 3:3:2 ratio 322,779:322,779: 1.06 0.12 0.83-1.29 1.22 0.15 0.93-1.51 2.66 0.09 215,186 n=50 Clearcut 7:1 ratio 753,151:107,593 0.37 0.07 0.22-0.51 0.26 0.08 0.10-0.42 n=46 7:1 ratio 753,151:107,593 ' 0.12 0.05 0.03-0.21 1.62 0.23 n=50 3:3:2 ratio 322,779:322,779: 0.42 0.08 0.25-0.58 0.63 0.14 0.33-0.92 0.38 0.10 215,186 n=48 145 Appendix 3.1. (cont'd) Douglas f i r seed and a l t e r n a t i v e seeds August 1976 E x p e r i m e n t a l • T r i a l No. 1 Douglas f i r Sunflower Oats Seed d e n s i t i e s / h a mean SE 95% C L . mean SE. _~ 95%C.L.~.-,-mean SE 4 weeks F o r e s t 7:1 r a t i o 753,151:107,593 0.28 0.06 0.15-0.41 0.65 0.15 0.35-0.95 n=49 7:1 r a t i o 753,151:107,593 0.16 0.05 0.05-0.27 1.78 0.19 n=50 3:3:2 r a t i o 322,779:322,779: 0.60 0.10 0.39-0.81 0.06 0.02 0.01-0.11 1.28 0.11 215,186 n=50 C l e a r c u t 7:1 r a t i o 753,151:107,593 0.20 0.06 0.08-0.31 0.00 0.00 0.00-0.00 n=46 7:1 r a t i o 753,151:107,593 0.04 0.03 0.02-0.10 0.38 0.07 n=50 3:3:2 r a t i o 322,779:322,779: 0.10 0.05 0.01-0.19 0.00 0.00 0.00-0.00 0.29 0.06 215,186 n=48 Appendix 3.1. (cont'd) Douglas f i r seed and alternative seeds November 1976 Experimental Trial No. 2 Douglas f i r Sunflower Seed densities/ha mean SE 95% CL. mean SE 95% CL. 2 weeks Clearcut 0:1 ratio 107,593 0.02 0.02 -0.02-0.06 n=50 7:1 ratio 753,151:107,593 0.50 0.07 0.36-0.64 1.16 0.18 0.78-1.54 n=50 7:1 ratio 753,151:107,593 0.40 0.07 0.26-0.54 0.72 0.11 0.49-0.95 (sequential) n=50 4 weeks Clearcut 0:1 ratio 107,593 0.02 0.02 -0.02-0.06 n=50 7:1 ratio 753,151:107,593 0.40 0.07 0.26-0.54 0.26 0.06 0.14-0.38 n=50 7:1 ratio 753,151:107,593 0.30 0.07 0.17-0.43 0.56 0.09 0.37-0.75 (sequential) n=50 Appendix 3.1.(cont'd) Douglas f i r seed and alternative seeds March to May 1977 Experimental Trial No. 3 Douglas f i r sunflower Seed densities/ha mean .. SE 95% CL. mean SE 95% CL. 2 weeks Forest (all 7:1 ratios) 753,151:107,593 0. 62 0. .07 0. .48--0. .76 3. 60 0. ,29 3. 03--4. .17 n=50 753,151:107,593 0. 68 0. .07 0. .55--0. .81 5. 12 0. .32 4. 48--5. .76 n=50 753,151:107,593 0. 84 0. .05 0. .73--0. .95 4. 22 0. .35 3. 53--4. .91 n=50 753,151:107,593 0. 69 0. .07 0. .55--0. .82 v. 17 0. .36 3. 45--4. .88 n=48 Clearcut (all 7: 753,151:107,593 n=48 753,151:107,593 n=50 753,151:107,593 n=50 753,151:107,593 n=50 0:1 ratio 107,593 n-98 ratios) 0.48 0.07 0.58 0.07 0.52 0.07 0.52 0.07 .0.13 0.03 0.33-0.63 2.96 0.44-0.72 4.42 0.38-0.66 2.66 0.38-0.66 1.08 0.06-0.20 0.33 2.29-3.63 0.27 3.88-4.96 0.24 2.18-3.14 0.21 0.66-1.50 148 Appendix 3.1. (cont'd) Douglas f i r seed and alternative seeds March to May 1977 Experimental t r i a l No. 3 Douglas f i r sunflower Seed densities/ha mean SE 95% CL. mean SE 95% CL. 4 weeks Forest (all 7:1 ratios) 753,151:107,593 0.56 0.07 0.42-0.70 5.04 0.47 4.09-5.99 n=50 753,151:107,593 0.36 0.07 0.22-0.50 5.00 0.49 3.99-6.01 n=50 753,151:107,593 0.68 0.07 0.55-0.81 1.90 0.26 1.37-2.43 n=50 753,151:107,593 0.42 0.07 0.27-0.56 0.38 0.07 0.24-0.52 n=50 0:1 ratio 107,593 0.05 0.02 0.01-0.09 Clearcut (all 7: 1 ratios) 573,151:107,593 0.42 0.07 0.27-0.50 4.23 0.49 3.21-5.25 n=48 753,151:107,593 0.56 0.07 0.42-0.70 1.94 0.26 1.41-2.47 n=50 753,151:107,593 0.30 0.07 0.17-0.43 0.28 0.06 0.15-0.41 n=50 753,151:107.593 0.38 0.07 0.24-0.52 1.72 0.33 1.05-2.39 n=50 0:1 ratio 107,593 0.11 0.03 0.05-0.18 " n=98 149 Appendix 3.1. (cont'd) Douglas f i r seed and alternative seeds November 1977 Experimental Trial No. 4 Douglas f i r sunflower oats mean SE 95% CL. mean SE 95% CL. mean SE Seed densities/ha 2 weeks Clearcut 7:1 ratio 753,151:107,593 0.65 0.05 0.55-0.75 0.63 0.07 0.47-0.79 . n=100 5:2:1 ratio 537,965:215,186: 0.58 0.07 0.44-0.72 0.30 0.05 0.19-0.41 1.28 0.10 107,593 n=50 .. 5:2:1 ratio 537,965:215,186: 0.74 0.06 0.61-0.87 0.74 0.13 0.47-1.01 1.64 0.06 107,593 n=50 4 weeks Clearcut 7:1 ratio 753,151:107,593 0.48 0.05 0.38-0.58 0.15 0.04 0.07-0.23 n=100 5:2:1 ratio 537,965:215,186: 0.46 0.07 0.32-0.60 0.02 0.01-0.01-0.05.0.28 0.08 107,593 n=50 5:2:1 ratio 537,965:215,186: 0.54 0.07 0.40-0.68 0.00 0.00 0.00-0.00 0.74 0.10 107,593 n=50 Appendix 3.2. Douglas f i r seed responses of deer mice in the forest. The total number of seeds taken per hectare and total number of mice per hectare are given as is the time span over which each experimental t r i a l was conducted. Initial no. Trial Total no. of Number of Number of Number of seeds of seeds/ha no. seeds mice/ha days taken per mouse taken/ha per day 107,593 1 80,694.9 20.9 19 203.2 (1 seed/sq. ft.) 2 62,762.7 22.2 14 201.9 4 102,158.9 35.8 12 237.8 4 93,606.1 34.6 14 193.2 215,186 1 190,782.8 23.5 19 427.3 (2 seeds/sq. ft.) 2 107,593.2 19.8 14 388.1 430,373 1 288,350.3 27.2 14 757.2 (4 seeds/sq. ft.) 2 378,728.1 34.6 13 842.0 3 268,983.0 29.6 14 649.1 860,746 1 286,915.2 23.4 14 872.1 (8 seeds/sq. ft.) 2 618,660.9 35.8 14 1234.4 4 796,189.7 60.5 14 940.0 4 811,252.7 54.3 14 1067.2 1,075,932 4 828,467.6 28.4 14 2083.7 (10 seeds/sq. ft.) 4 1,017,831.7 53.1 12 1597.4 1,291,118 4 936,060.8 42.0 12 1857.3 (12 seeds/sq. ft.) 1,721,491 4 1,620,353.6 51.9 15 2081.4 (16 seeds/sq. ft.) 151 CHAPTER 4 SEASONAL ABUNDANCES OF CONIFER SEED IBEDATOBS INTRODUCTION L i t t l e i s known about the best time of year f o r seeding with r e s p e c t to low p o p u l a t i o n s of seed-eating s m a l l mammals and b i r d s . Seed-eating b i r d s appear to be absent or a t very low d e n s i t i e s during winter on c l e a r c u t areas i n C a l i f o r n i a (Bagar 1960) and Oregon (Gashwiler and Ward 1968). Pop u l a t i o n s o f chipmunks (Eutamias spp.) tend to be i n a c t i v e from November to A p r i l i n temperate zone c o n i f e r o u s f o r e s t s fSheppard 1968, 1969). T h i s p e r i o d of i n a c t i v i t y may be s h o r t e r i n other p l a c e s such as the southwestern United S t a t e s , (see Dunford 1974; S k r y j a 1974) where l o c a l c l i m a t i c c o n d i t i o n s may not be as severe as i n more n o r t h e r l y l a t i t u d e s . The e a s t e r n chipmunk f'Tamias s t r i a t u s ) i s c o n s i d e r e d to be a p h y s i o l o g i c a l i n t e r m e d i a t e between h i b e r n a t o r s and non-h i b e r n a t o r s , whereas the northwestern chipmunk (Eutamias amcenus) i s a poor or no n - h i b e r n a t i n g s p e c i e s (Stebbins and O r i c h 1977). However, both these chipmunk s p e c i e s are g e n e r a l l y i n a c t i v e and disappear below ground dur i n g winter. P o p u l a t i o n s o f Peromyscus maniculatus do net h i b e r n a t e and can be present throughout a l l months of the year. Deer mice are 152 most a b u n d a n t i n t h e f a l l and l e a s t a b u n d a n t i n t h e s p r i n g ( s e e c h a p t e r 1 i n t h i s t h e s i s and S a d l e i r 1965; H e a l e y 1967; Fordham 19 7 1 ; P e t t i c r e w and S a d l e i r 1974; F a i r b a i r n 1977; and S u l l i v a n 1 9 7 7 ) . I f t h e b i o l o g i c a l c o n t r o l t e c h n i q u e d e s c r i b e d i n t h i s t h e s i s i s t o be u s e d s u c c e s s f u l l y t o r e d u c e c o n i f e r s e e d damaqe by d e e r m i c e , c h i p m u n k s , and b i r d s , t h e n t h e b e s t t i m e f o r s e e d i n g ( i n r e l a t i o n t o f a v o u r a b l e g e r m i n a t i o n a n d s e e d l i n g e s t a b l i s h m e n t ) must be d e t e r m i n e d . The s t u d y o u t l i n e d i n t h i s c h a p t e r was d e s i g n e d t o d e t e r m i n e t h e a b u n d a n c e o f c h i p m u n k s and s e e d - e a t i n g b i r d s t h r o u g h o u t t h e y e a r and c o m b i n e t h i s k n o w l e d g e w i t h what i s a l r e a d y documented f o r d e e r m i c e . From J u l y t o November 1976 a n d M a r c h t o November 1 9 7 7 , two t r a p l i n e s ( B u r n - and S l a s b - c l e a r c u t ) were l i v e - t r a p p e d e v e r y two weeks w i t h Sherman l i v e - t r a p s . E a c h l i n e was a p p r o x i m a t e l y 900 m l o n g w i t h 25 t r a p s t a t i o n s l o c a t e d a t 37.5-m i n t e r v a l s . Two t r a p s were p l a c e d a t e a c h s t a t i o n * The t r a p p i n g p r o c e d u r e was s i m i l a r t o t h a t f o r d e e r m i c e e x c e p t t h a t t r a p s were s e t on t h e m o r n i n g o f d a y 1, c h e c k e d t h e same a f t e r n o o n , and t h e n t h e f o l l o w i n g m o r n i n g and a f t e r n o o n o f day 2. To a v o i d i n t e r f e r e n c e b e t w e e n l i n e s a nd g r i d s i n t h e same a r e a , c h i p m u n k l i n e s were u s u a l l y t r a p p e d a f t e r c o m p l e t i o n o f t h e d e e r mouse t r a p p i n g MATEBIftlS MD METHODS 153 p e r i o d or on a l t e r n a t e seeks. a l l chipmunks captured were weighed on Pesola s p r i n g balances, sexed, and ear-tagged with s e r i a l l y numbered f i n g e r l i n g f i s h tags. Information on breeding performance was noted by p a l p a t i o n of male t e s t e s and the c o n d i t i o n of v a g i n a l openings and mammaries of the females. P o p u l a t i o n s i z e was determined by enumeration and c a l c u l a t e d as the minimum number of animals known to be a l i v e (MNA) at each c o n s e c u t i v e two-week i n t e r v a l (see H i l b o r n e t a l . 1976). P o p u l a t i o n s of s e e d - e a t i n g b i r d s From February to November 1977, p o p u l a t i o n s of s e e d - e a t i n g b i r d s were censused a t the Burn study a r e a . During the mornings, u s u a l l y between 8 to 10 A. H. , the number of b i r d s of each s p e c i e s observed on each o f the f o u r g r i d s (G, H, I, and J) was recorded. The observer walked the 'C 1 and «E* l i n e s of each g r i d c o u n t i n g a l l b i r d s which were s i g h t e d and/or heard on that g r i d . Care was taken not to/ enumerate an i n d i v i d u a l b i r d more than once. T h i s census occurred on one or two days every two weeks and provided i n f o r m a t i o n on the number of b i r d s cf each s p e c i e s per h e c t a r e over the d i f f e r e n t seasons of the year. B i r d s were not censused i n J u l y and August, although most s p e c i e s were abundant during these months. SESULTS Chipmunk p o p u l a t i o n s The s e a s o n a l v a r i a t i o n i n d e n s i t y of chipmunks from the Burn and S l a s h t r a p p i n g areas i s shown i n F i g u r e 4.1. I n 1976, 154 t h e number o f a n i m a l s on t h e B u r n i n c r e a s e d d u r i n g t h e i n i t i a l w eeks o f t r a p p i n g , and l a t e r by summer r e c r u i t m e n t . D e n s i t y b e g a n d e c l i n i n g i n O c t o b e r a s a n i m a l s i n b o t h s t u d y a r e a s went i n t o h i b e r n a t i o n . C h i p m u n k s r e a p p e a r e d i n l a t e M a r c h - e a r l y A p r i l 1977 and were p r e s e n t on t h e s t u d y a r e a u n t i l l a t e O c t o b e r . p o p u l a t i e n s o f s e e d - e a t i n g b i r d s The s i x most common s p e c i e s o f s e e d - e a t i n g b i r d s and t h e i r d e n s i t y p e r h e c t a r e t h r o u g h o u t 1977 a r e shown i n F i g u r e 4.2. The d a r k - e y e d j u n c o was t h e most a b u n d a n t s p e c i e s d u r i n g t h i s s t u d y . Most s p e c i e s o f t h e s e s e e d - e a t i n g b i r d s were a b s e n t o r a t v e r y l o w d e n s i t i e s up t o l a t e M a r c h , when t h e y became more a b u n d a n t on t h e c l e a r c u t . I n l a t e O c t o b e r , t h e s e . b i r d s a g a i n became l e s s n u m e r o u s , p r o b a b l y o w i n g t o m i g r a t i o n t o more f a v o u r a b l e r e g i o n s f o r t h e w i n t e r . DISCUSSION Many s p e c i e s o f b i r d s and s m a l l mammals f e e d on t r e e s e e d , w h i c h i s consumed e i t h e r d i r e c t l y on t h e p a r e n t t r e e s o r c n t h e g r o u n d a f t e r n a t u r a l s e e d - f a l l o r f o l l o w i n g d i r e c t s e e d i n g . Among b i r d s , j u n c o s ( J u n c o _spj3.) , r o b i n s ( T u r d u s m i g r a t o r i u s ) , s o u t h e r n m e a d o w l a r k s ( S t u r n e l l a magna), and m o u r n i n g d o v e s f Z e n a i d u r a m a c r o u r a ) a r e t y p i c a l o f t h o s e c i t e d a s i m p o r t a n t a v i a n c o n i f e r s e e d p r e d a t o r s ( B u r l e i g h 1938; S m i t h and A l d o u s 1947; and E astman 1 9 6 0 ) - A c c o r d i n g t o E u n n e l l and E a s t m a n ( 1 9 7 6 ) , t h e s p e c i e s t h a t p r e f e r o r a r e r e s t r i c t e d t o r e c e n t l y 155 logged areas are p r i m a r i l y sparrows (Family F r i n g i l l i d a e ) . Numerous s t u d i e s have i n d i c a t e d t h a t the d i v e r s i t y of b i r d s p e c i e s i n c r e a s e s d u r i n g s u c c e s s i o n and then d e c l i n e s as the climax f o r e s t i s a t t a i n e d (see review by Balda 1975). However, only the s t u d i e s of Hagar (1960) and Gashwiler and Ward (1968) re p o r t on the abundance of b i r d s p e c i e s i n d i f f e r e n t seasons of the year f o r s e v e r a l y e a r s . Data of t h i s type would probably show great v a r i a t i o n with r e s p e c t to s i t e and l o c a t i o n of the c l e a r c u t areas but would s t i l l be v a l u a b l e f o r determining when po p u l a t i o n s of s e e d - e a t i n g b i r d s were absent or much reduced d u r i n g winter. In t h i s study, avian seed e a t e r s were present on the logged areas from A p r i l to l a t e October- Thus, they were absent or a t very low d e n s i t i e s d u r i n g the winter and e a r l y s p r i n g from November through March. Hagar (1960) and Gashwiler and ward (1968) reported s i m i l a r r e s u l t s from t h e i r i n d i c e s of the d e n s i t y of b i r d s throughout the year. The s t u d i e s of Sheppard (1968, 1969) provide some i n f o r m a t i o n on t h e s e a s o n a l abundance of chipmucks, and these r e s u l t s are comparable to those i n my study. I t may be g e n e r a l l y concluded t h a t chipmunks h i b e r n a t e at some time i n the f a l l and reappear above ground i n the s p r i n g i n areas with seasonal v a r i a t i o n s i n weather ( i . e . temperate zone w i n t e r s ) . Consequently, Eutamias amoenus i s not present on c l e a r c u t areas d u r i n g the w i n t e r and e a r l y s p r i n g . In a d d i t i o n , p o p u l a t i o n s of both seed-eating b i r d s and chipmunks are a t t h e i r lowest d e n s i t y du r i n g the s p r i n g before breeding commences. P o p u l a t i o n s of Pecomyscus maniculatus a l s o f o l l o w t h i s p a t t e r n , but are g e n e r a l l y a c t i v e a l l winter, except perhaps i n areas with an 156 extreme winter c l i m a t e , where they may en t e r temporary p e r i o d s of t o r p o r ( F a l l s 1968). T h e r e f o r e , the very best time f o r seeding with r e s p e c t to low p o p u l a t i o n s of seed-eating small mammals and b i r d s i s i n the l a t e w i n t e r - e a r l y s p r i n g . T h i s time p e r i o d f i t s i n w e l l with the presumed most f a v o u r a b l e time f o r c o n i f e r seed germination. 157 F i g u r e 4-1- numbers of chipmunks on the Burn ana Slash t r a p -l i n e s d u r i n g 1976-77- Minimum number of animals known to be a l i v e (MNA) f o r 25 t r a p s t a t i o n s c o v e r i n g 900 m has been p l o t t e d a g a i n s t time except f o r the f a l l d e c l i n e s and s p r i n g i n c r e a s e s i n d e n s i t y which rep r e s e n t number o f animals captured. 5 5 T J A S O N D J F M A M J J A S O 1976 159 F i g u r e 4 . 2 . Numbers o f the s i x most common seed - e a t i n g b i r d s p e c i e s on the Burn study area. Each c l o s e d c i r c l e r e p r e s e n t s the number of b i r d s per h e c t a r e as an average from f o u r d i f f e r e n t g r i d areas. The dashed l i n e r e p r e s e n t s the perio d i n J u l y and August when b i r d s were not censused. 7' & 5 4 3 2 1 5-4. 3-2 1-5 4 3 2 1 5 4 3 2 1 5 4 3 2 1 5 4 3 160 1977 161 CHAPTER 5 BEFOBESTATION BY DIRECT SEEDING WITH COHIFES SEED AND SLTEBNATIVE FOODS INTRODUCTION R e f o r e s t a t i o n o f c u t o v e r f o r e s t l a n d by d i r e c t a p p l i c a t i o n of seed has long been a goal o f f o r e s t e r s i n North America. D e s t r u c t i o n of the seed supply by s m a l l mammals and b i r d s has ad v e r s e l y a f f e c t e d the success of these r e f o r e s t a t i o n p r o j e c t s {see reviews by Black 19 69; Radwan 1970; Badvanyi 1973; and Pank 1974). These a u t h o r s l i s t deer mice (Peromyscus s p p . ) , chipmunks (Eutamias s p p . ) , and v a r i o u s s p e c i e s of se e d - e a t i n g b i r d s as the most important c o n i f e r seed predators i n the temperate c o n i f e r o u s f o r e s t s of North America* D i r e c t seeding has g e n e r a l l y f a i l e d as a means of re g e n e r a t i n g f o r e s t s i n Canada even though the technique o f f e r s g r e a t p o t e n t i a l <see Cayford 1973). S i m i l a r l y , i n the United S t a t e s , d i r e c t s e e d i n g has d e c l i n e d d r a m a t i c a l l y i n rec e n t years because of rodent p r e d a t i o n on c o n i f e r seed and the banning o f chemical r e p e l l e n t s (Abbott 1973). Two b a s i c approaches to reducing c o n i f e r seed p r e d a t i o n are c o n v e n t i o n a l c o n t r o l methods, which have mainly i n v o l v e d 16 2 c h e m i c a l s , and b i o l o g i c a l c o n t r o l . For almost h a l f a c e n t u r y , f o r e s t managers i n the P a c i f i c Northwest have developed numerous techniques f o r p r o t e c t i n g t r e e seed from r o d e n t s and s e e d - e a t i n g b i r d s . These c o n v e n t i o n a l c o n t r o l methods i n c l u d e d mechanical d e v i c e s , poison b a i t s , and chemical r e p e l l e n t s a p p l i e d d i r e c t l y to seeds. None o f these techniques has been s u c c e s s f u l . Consequently, a r t i f i c i a l r e g e n e r a t i o n of f o r e s t s has become dominated by the p l a n t i n g of s e e d l i n g s and the c u l t i v a t i o n of p l a n t a t i o n s . However, p l a n t i n g c o s t s may be f i v e times those of d i r e c t seeding (Walters and K l i n k a 1977) . The low c o s t of seeding and the p o s s i b i l i t y of q u i c k l y and e f f i c i e n t l y r e g e n e r a t i n g l a r g e areas make i t a f a v o u r a b l e technique f o r r e f o r e s t i n g the tremendous backlog of u n s a t i s f a c t o r i l y restocked l a n d s . B i o l o g i c a l c o n t r o l of c o n i f e r seed p r e d a t i o n by the use of a l t e r n a t i v e foods o f f e r s a non-chemical s o l u t i o n t o the problem of o b t a i n i n g s u c c e s s f u l r e f o r e s t a t i o n by d i r e c t s e e d i n g . In t h i s chapter I d i s c u s s the recommended procedure f o r a p p l y i n g the b i o l o g i c a l c o n t r o l technique (see chapter 3) i n r e f o r e s t a t i o n programs using d i r e c t seeding of c o n i f e r seed fcith a l t e r n a t i v e foods. BESDLTS D i r e c t seeding with Douglas f i r seed and a l t e r n a t i v e foods The r e s u l t s of e x p e r i m e n tal d i r e c t s e e d i n g with Douglas f i r and a l t e r n a t i v e foods i n a uniform d i s t r i b u t i o n on the c l e a r c u t are presented i n F i g u r e 5.1. These data have been compiled from the s p r i n g 1977 seeding experiment (see chapter 3} as well as experimental t r i a l s i n the l a t e f a l l of 1976 and 1977, which a l s o produced v a l i d r e s u l t s on s u r v i v a l of c o n i f e r seed and may be a p p l i e d t o s p r i n g c o n d i t i o n s . The 7:1 and 5:2:1 r a t i o s produced e x c e l l e n t s u r v i v a l of c o n i f e r seed. These r e s u l t s may a l s o be expressed as the p o t e n t i a l number of s e e d l i n g s per ha (assuming, i n t h i s c a s e , the cutover area i s d i r e c t - s e e d e d with 0. 10 kg Douglas f i r seed/ha, and t h a t the seeds s u c c e s s f u l l y germinate). A p p l i c a t i o n i n r e f o r e s t a t i o n p r o j e c t s The b i o l o g i c a l technigue d e s c r i b e d i n chapter 3 of t h i s t h e s i s f o r r e g e n e r a t i n g cutover f o r e s t l a n d s should be a p p l i e d i n the l a t e w i n t e r - e a r l y s p r i n g (February-March-April, depending on l o c a l snow c o n d i t i o n s ) i n the year a f t e r an area i s legged. In areas with winter snow cov e r , most of t h i s snow should or soon w i l l have disappeared before seeding commences. T h i s w i l l a l l o w the necessary seedbed moisture, which i s of paramount importance f o r germination i n d i r e c t seeding (Arnott 1973). The recommended mixture of seed t o be a e r i a l l y seeded over a c l e a r c u t i s as f o l l o w s : 0. 10 kg Douglas f i r seed or ether c o n i f e r seed ( e q u i v a l e n t number of seeds by weight) to 56 kg sunflower seed and 7 kg oats per ha. T h i s mixture may be d i s t r i b u t e d on c l e a r c u t s i n the C o a s t a l Western Hemlock (dry and wet subzones) and C o a s t a l Douglas f i r (dry and wet subzenes) b i e g e o c l i m a t i c zones of B r i t i s h Columbia. Areas chosen f o r seeding should be s u i t a b l e s i t e s f o r growth of Douglas f i r ( i . e . not lowland swamp areas or high e l e v a t i o n s i t e s ) . 164 To o b t a i n a random or uniform d i s t r i b u t i o n of t r e e s , the seed must be d i s p e r s e d evenly over the area of the c l e a r c u t - In a d d i t i o n , the c o n i f e r seed must be s t r a t i f i e d f o r a t l e a s t t h r e e weeks and soaked i n growth hormones (see H a l t e r s and K l i n k a 1977). T h i s procedure should promote seed germination w i t h i n a 2- to 4-week p e r i o d a f t e r d i r e c t seeding- T h i s p e r i o d i s w e l l w i t h i n the average l e n g t h of time (4 weeks) i n which Douglas f i r seed showed e x c e l l e n t s u r v i v a l d u r i n g my s p r i n g experiments. The suggested procedure f o r a p p l y i n g t h i s b i o l o g i c a l technique i n d i r e c t seeding o p e r a t i o n s i s summarized i n F i g u r e 5.2-Econcroic aspects The c o s t cf seeding c o n i f e r seed and a l t e r n a t i v e foods i n t h i s new r e f o r e s t a t i o n technique i s approximately $64.68/ha based on the f o l l o w i n g : Douglas f i r seed $90-00/kg x 0-10 kg = $9.00 sunflower seed $0.64/kg x 56 kg = $44.84 oats $0.12/kg x 7 kg = $0.84 D i s t r i b u t i o n o f seed mixture $10.00/ha T o t a l c o s t $64.68/ha DISCUSSION The s u c c e s s f u l e s t a b l i s h m e n t of new crops on c u t o v e r areas i s a necessary p r e r e q u i s i t e to s u s t a i n e d y i e l d of wood products and other f o r e s t (and w i l d l i f e ) r e s o u r c e s . In Canada and the United S t a t e s , approximately 22 m i l l i o n and 30 m i l l i o n ha 165 r e s p e c t i v e l y , r e q u i r e a r t i f i c i a l r e g e n e r a t i o n (Walters and K l i n k a 1977). With the present r a t e o f r e g e n e r a t i o n (about 1 m i l l i o n ha a n n u a l l y i n North America), i t i s u n l i k e l y that r e f o r e s t a t i o n i s keeping up with the r a t e of c u t t i n g or c a t c h i n g up on the tremendous backlog of u n s a t i s f a c t o r i l y r e s t o c k e d l a n d s . I t has become ev i d e n t t h a t the c r e a t i o n of man-made f o r e s t s must be i n c r e a s e d a p p r e c i a b l y i f the f o r e s t i n d u s t r y and the resources a s s o c i a t e d with f o r e s t s are to be maintained. D i r e c t seeding i s a method of r e g e n e r a t i o n which seems to o f f e r a p r a c t i c a l and economical s o l u t i o n to the massive problem of r e f o r e s t a t i o n . Among the advantages c i t e d f o r seeding a re lower c o s t , a lower requirement f o r la b o u r and s u p e r v i s i o n , r a p i d r e g e n e r a t i o n of l a r g e areas from the a i r , f l e x i b i l i t y , and a r e s u l t i n g stand of t r e e s with a n a t u r a l l y developed r o o t system (Walters and K l i n k a 1977). D i r e c t seeding has g e n e r a l l y f a i l e d as a r e l i a b l e r e f o r e s t a t i o n p r a c t i c e i n North America. Perhaps one of the most important problems a s s o c i a t e d with t h i s f a i l u r e i s the time of year when seeding has teen done and how i t r e l a t e s to p o t e n t i a l germination and p o p u l a t i o n s of s m a l l mammals and seed-e a t i n g b i r d s * Waldron (1973) has r e p o r t e d t h a t the major i t y of d i r e c t seeding i n Canada has been done i n the f a l l . However, sowing i n A p r i l , Hay, and June has y i e l d e d on the average higher s t o c k i n g than e i t h e r autumn or winter s e e d i n g . S i m i l a r l y , i n the P a c i f i c Northwest of the Un i t e d S t a t e s , seeding has been mainly c a r r i e d out i n the f a l l (Gartz 1955; Carmichael 1957; and Lavender 1958). Why has most d i r e c t seeding been attempted i n the f a l l a t a time when p o p u l a t i o n s of deer mice, chipmunks, and 166 s e e d - e a t i n g b i r d s a r e h i g h e s t ? P r e s u m a b l y , c o n i f e r s e e d sown i n t h e f a l l u n d e r g o e s n a t u r a l s t r a t i f i c a t i o n ( p r e p a r a t i o n f o r g e r m i n a t i o n by s o a k i n g i n w a t e r ) d u r i n g t h e w i n t e r and i s t h e n a b l e t o g e r m i n a t e i n t h e s p r i n g . H o w e v e r , l a b o r a t o r y s t r a t i f i c a t i o n p r e v e n t s s e e d f r o m b e i n g e x p o s e d t o s m a l l mammal d e p r e d a t i o n s i n t h e f a l l and w i n t e r . S p r i n g s e e d i n g p r o g r a m s i n N o r t h A m e r i c a , a l t h o u g h f e w i n number, h a v e p r o v e d t o be more s u c c e s s f u l , a t l e a s t when com p a r e d w i t h t h o s e a t o t h e r s e a s o n s o f t h e y e a r ( s e e C a r m i c h a e l 1957; S a l d r o n 1 9 7 3 ) . A r n o t t (1973) c o n c l u d e d t h a t s e e d b e d m o i s t u r e a n d t e m p e r a t u r e c o n d i t i o n s were l i k e l y t o be optimum i n t h e s p r i n g . H o w e v e r , t h e b e s t s o w i n g s e a s o n v a r i e d w i t h t r e e s p e c i e s , s i t e f a c t o r s , and w e a t h e r p a t t e r n s . S u c c e s s f u l r e f o r e s t a t i o n p r o g r a m s r e g u i r e a random o r u n i f o r m d i s t r i b u t i o n o f s e e d l i n g s o v e r t h e a r e a o f a c l e a r c u t . A u n i f o r m d i s t r i b u t i o n may be o b t a i n e d by m e t h o d i c a l l y p l a n t i n g t r e e s e e d l i n g s i n r o w s w h e r e a s a s c a t t e r e d o r random d i s t r i b u t i o n i s a more l i k e l y r e s u l t o f d i r e c t s e e d i n g . A c l u m p e d o r a g g r e g a t e d d i s t r i b u t i o n o f t r e e s i s u n d e s i r a b l e b e c a u s e t h i n n i n g o f t h e s t a n d must be done a f t e r t h e i n i t i a l s e e d i n g and some p a r t s o f t h e c u t o v e r a r e a a r e o b v i o u s l y u n d e r s t o c k e d . T h i s r a i s e s t h e c o s t o f r e f o r e s t a t i o n and i s one o f t h e main r e a s o n s , a l o n g w i t h p r e d a t i o n o f s e e d s by s m a l l mammals, t h a t p l a n t i n g s e e d l i n g s i s now f a v o u r e d o v e r d i r e c t s e e d i n g . A n o t h e r c r i t i c i s m o f d i r e c t s e e d i n g i s t h e w a s t e o f c o n i f e r s e e d w h i c h i s s o o f t e n i n s h o r t s u p p l y ( V y s e 1 9 7 3 ) . P r e s u m a b l y , se e d t h a t i s c o l l e c t e d d u r i n g y e a r s w i t h a good c o n e c r o p s h o u l d 167 be used i n production of nursery stock f o r p l a n t i n g . Seed shortages have o f t e n been o f f e r e d as the p r i n c i p a l reason f o r the absence cf d i r e c t seeding i n B. C- (Robinson 1S70). However, Vyse (1973) d i s c u s s e s the erroneous philosophy t h a t i t i s w a s t e f u l to apply r e l a t i v e l y l a r g e q u a n t i t i e s of seed per ha when the same seed used t o grow s e e d l i n g s c o u l d r e s t o c k a much l a r g e r a r e a . I f i t i s economically advantageous to seed a given a r e a , then the e x t r a r e s o u r c e s saved from not p l a n t i n g may be spent on r e l i e v i n g the seed shortage. Increased r e f o r e s t a t i o n work loads and dwindling s u p p l i e s of manpower f o r the arduous task of p l a n t i n g are f o r c i n g a r e a p p r a i s a l of seeding i n a d d i t i o n to generating a search f o r new r e f o r e s t a t i o n methods (Vyse 1973). The value of having one or more a d d i t i o n a l techniques f o r s u c c e s s f u l r e f o r e s t a t i o n cannot be underestimated. Recording t o the economic a n a l y s e s of Teeguarden (1969), d i r e c t seeding, when compared with p l a n t i n g , i s the best investment o p p o r t u n i t y on a number of the best s i t e c l a s s e s (in the Douglas f i r r e g i o n of southwestern Oregon) but on the poorer s i t e s was found to be i n f e r i o r . The a p p l i c a t i o n of p l a n t i n g to a l l e c o l o g i c a l , economic, and a d m i n i s t r a t i v e c o n d i t i o n s i s not a sound management approach i n r e f o r e s t a t i o n . I t has been known f o r some time that p l a n t a t i o n s u r v i v a l and subseguent s e e d l i n g growth i n B* C. are f a r from s a t i s f a c t o r y (Walters 1977). There are s e v e r a l f a c t o r s r e s p o n s i b l e f o r t h i s poor r e g e n e r a t i o n . Non-ecosystem s p e c i f i c t r e e s p e c i e s s e l e c t i o n , n o n - s e l e c t i v e management p r a c t i c e s such as i n d i s c r i m i n a t e use of s l a s h burning, poor s e l e c t i o n of p l a n t i n g m i c r o s i t e s , and poor q u a l i t y of p l a n t i n g stock and 168 p l a n t i n g have a l l c o n t r i b u t e d to the problem ( H a l t e r s 1 5 7 7 ) . The c o s t of n u r s e r i e s and production of s e e d l i n g stock must a l s o be considered when a n a l y s i n g the problems a s s o c i a t e d s i t h p l a n t i n g . Thus, t h i s c hapter has d e s c r i b e d some of the p o t e n t i a l b e n e f i t s i n r e t u r n i n g t o d i r e c t seeding as a means of re g e n e r a t i n g cutover f o r e s t l a n d s . The b i o l o g i c a l c o n t r o l technique f o r reducing c o n i f e r seed damage by deer mice should be an i n t e g r a l p a r t of the f u t u r e success of d i r e c t s e e d ing. 169 F i g u r e 5-1. The success of d i f f e r e n t Douglas f i r t o sunflower (and oats) r a t i o s a t two and f o u r weeks a f t e r seeding- The p o t e n t i a l number o f s e e d l i n g s per ha at a seeding d e n s i t y of 0-10 Kg Douglas f i r seed per ha i s a l s o shown. The c l o s e d c i r c l e s r e p r e s e n t percentage s u r v i v a l of Douglas f i r a f t e r week 2- The l i n e connects the average values at each r a t i o . The open c i r c l e s r e p r e s e n t percentage s u r v i v a l a f t e r week 4. The dashed l i n e connects the average v a l u e s at each r a t i o . 171 F i g u r e 5.2. Suggested procedure f o r s u c c e s s f u l r e f o r e s t a t i o n by d i r e c t seeding with c o n i f e r seed and a l t e r n a t i v e f o o d s . 172 Mixture of coni f e r seed with sunflower seed and oats i n 5 : 2 : 1 r a t i o — Uniform- d i s t r i b u t i o n over area of clearcut: SUCCESSFUL STOCKING OF CLEARCUT Lowest density of Deer mice Chipmunks and seed-eating birds absent from clearcuts•from l a t e October to early A p r i l Lowest density i n Spring • 173 LITERATUSE CITED Abbott, H.G- 1973. D i r e c t seeding i n the United S t a t e s . In: J.H. Cayford ( e d . ) . D i r e c t s e e d i n g symposium. Dept., of the Environment, Canad. For- Ser., Put. No. 1339. pp. 1-10. Ahlgren, C.E. 1966. Small mammals and r e f o r e s t a t i o n f o l l o w i n g p r e s c r i b e d burning. J. For. 64: 614-618. A l l e n , G.S., I.K. Barber, and I . Mahood. 1955- The 1951 a e r i a l b a i t i n g and seeding p r o j e c t , Ash B i v e r T r a c t , M+B Ltd - For. 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