@prefix vivo: . @prefix edm: . @prefix ns0: . @prefix dcterms: . @prefix skos: . vivo:departmentOrSchool "Science, Faculty of"@en, "Zoology, Department of"@en ; edm:dataProvider "DSpace"@en ; ns0:degreeCampus "UBCV"@en ; dcterms:creator "Millar, John Steven"@en ; dcterms:issued "2011-07-06T00:28:28Z"@en, "1968"@en ; vivo:relatedDegree "Master of Science - MSc"@en ; ns0:degreeGrantor "University of British Columbia"@en ; dcterms:description "The reproductive condition of male and female red squirrels (Tarniasciurus hudsonicus) in southern British Columbia was studied in relation to age, season, relative population level, and foods utilized. The reproductive cycle of males and females is described on the basis of gross anatomy and histological characteristics. A low population on Vancouver Island was studied in 1966 and 1967 and a high population was studied near Princeton, B.C. in 1967. The habitats are similar in both regions. The low 1966 population had a late breeding season in which all females sampled produced two large litters. The ovulation rate for the two litter season averaged 5.12 per litter. The second ovulation occurred shortly after the birth of the first litter, before the uteri and vaginae came into full estrus condition. In 1967 both the low Vancouver Island population and the high Princeton population had early breeding seasons when nearly all adults bred yet only one third of the yearling females participated. Only single litters were produced in both areas. The ovulation rate was 4.11 per litter in the low Vancouver Island population and 3.58 per litter in the high Princeton population. Preimplantation losses of about 11% were fairly constant in both years. Postimplantation losses were not present in the low 1966 population, were about 19% in the high 1967 population, and were not determined in the low 1967 population. Similarities between the high and low 1967 populations and differences between the low 1966 and low 1967 populations on Vancouver Island suggest that density was not the primary force Influencing productivity. Another explanation is found in the evaluation of the primary food sources. Conifer cones are the main winter food of the red squirrel. Lodgepole pine cones were the main food source before the highly productive breeding season in I966 while Douglas fir cones made up the diet before the less successful breeding season in 1967. The fruiting habits of the conifers is discussed and It appears that it is advantageous for the squirrel to feed on lodgepole pine cones. A good winter food supply is particularly important to the red squirrel since it breeds during the late winter and it's already high metabolic rate increases still more during cold winter weather. It is inferred that the winter food supply may influence the relative capacity of the female to produce young. The timing of the breeding season is quite variable and seems to be affected by the severity of the winter weather."@en ; edm:aggregatedCHO "https://circle.library.ubc.ca/rest/handle/2429/35904?expand=metadata"@en ; skos:note "THE REPRODUCTIVE BIOLOGY OF THE WESTERN RED SQUIRREL by JOHN STEVEN MILLAR B.Sc, 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 , 1965 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE.REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n t h e Department o f Z o o l o g y We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA F e b r u a r y , 1968 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t t h e L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e Head o f my D e p a r t m e n t o r by h i s r e p r e s e n -t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f The U n i v e r s i V a n c o u v e r 8, t y o f B r C a n a d a Date ^ ^ s / V ABSTRACT / The r e p r o d u c t i v e c o n d i t i o n o f male and femal e r e d s q u i r r e l s (Tarn l a s c l u r u s h u d s o n l c u s ) i n s o u t h e r n B r i t i s h C o l u m b i a was s t u d i e d i n r e l a t i o n t o age, seas o n , r e l a t i v e p o p u l a t i o n l e v e l , and foods u t i l i z e d . The r e p r o d u c t i v e c y c l e o f males and females i s d e s c r i b e d on t h e b a s i s o f g r o s s anatomy and h i s t o l o g i c a l c h a r a c t e r i s t i c s . A l o w p o p u l a t i o n on Vancouver I s l a n d was s t u d i e d i n and I967 and a h i g h p o p u l a t i o n was s t u d i e d n e a r P r i n c e t o n , B.C. i n I967. The h a b i t a t s a r e s i m i l a r i n b o t h r e g i o n s . The lo w I966 p o p u l a t i o n had a l a t e b r e e d i n g s eason i n w h i c h a l l f e m a les sampled produced two l a r g e l i t t e r s . The o v u l a t i o n r a t e f o r t h e two l i t t e r s e a son a v e r a g e d 5«12 p e r l i t t e r . The second o v u l a t i o n o c c u r r e d s h o r t l y a f t e r t h e b i r t h o f t h e f i r s t l i t t e r , b e f o r e t h e u t e r i and v a g i n a e came i n t o f u l l e s t r u s c o n d i t i o n . I n 19&7 b o t h t h e low Vancouver I s l a n d p o p u l a t i o n and t h e h i g h P r i n c e t o n p o p u l a t i o n had e a r l y b r e e d i n g seasons when n e a r l y a l l a d u l t s b r e d y e t o n l y one t h i r d o f t h e y e a r l i n g f e males p a r t i c i p a t e d . Only s i n g l e l i t t e r s were produced i n b o t h a r e a s . The o v u l a t i o n r a t e was ^.11 p e r l i t t e r i n t h e l o w Vancouver I s l a n d p o p u l a t i o n and 3«58 p e r l i t t e r i n t h e h i g h P r i n c e t o n p o p u l a t i o n . P r e i m p l a n t a t i o n l o s s e s o f about 11$ were f a i r l y c o n s t a n t i n b o t h y e a r s . P o s t i m p l a n t a t i o n l o s s e s were n o t p r e s e n t i n t h e low 1966 p o p u l a t i o n , were about 19% I n t h e h i g h 19&7 p o p u l a t i o n , and were n o t d e t e r m i n e d i n t h e low 19^7 p o p u l a t i o n . S i m i l a r i t i e s i l l between t h e h i g h and l o w 19&7 p o p u l a t i o n s and d i f f e r e n c e s between t h e low 1966 and low 196? p o p u l a t i o n s on Vancouver I s l a n d s u g g e s t t h a t d e n s i t y was n o t t h e p r i m a r y f o r c e I n f l u e n c i n g p r o d u c t i v i t y . A n o t h e r e x p l a n a t i o n i s found i n t h e e v a l u a t i o n o f t h e p r i m a r y f o o d s o u r c e s . C o n i f e r cones a r e t h e main w i n t e r f o o d o f t h e r e d s q u i r r e l . L o d g e p o l e p i n e cones were t h e main f o o d s o u r c e b e f o r e t h e h i g h l y p r o d u c t i v e b r e e d i n g s e a s o n i n I966 w h i l e Douglas f i r cones made up t h e d i e t b e f o r e t h e l e s s s u c c e s s f u l b r e e d i n g s e a s o n i n 19&7. The f r u i t i n g h a b i t s o f t h e c o n i f e r s I s d i s c u s s e d and I t appears t h a t i t i s advantageous f o r t h e s q u i r r e l t o f e e d on l o d g e p o l e p i n e c o n es. A good w i n t e r f o o d s u p p l y i s p a r t i c u l a r l y i m p o r t a n t t o t h e r e d s q u i r r e l s i n c e i t breeds d u r i n g t h e l a t e w i n t e r and i t ' s a l r e a d y h i g h m e t a b o l i c r a t e i n c r e a s e s s t i l l more d u r i n g c o l d w i n t e r weather. I t i s i n f e r r e d t h a t t h e w i n t e r f o o d s u p p l y may i n f l u e n c e t h e r e l a t i v e c a p a c i t y o f t h e f e m a l e t o produce young. The t i m i n g o f t h e b r e e d i n g s eason i s q u i t e v a r i a b l e and seems t o be a f f e c t e d by t h e s e v e r i t y o f t h e w i n t e r w eather. i v TABLE OF CONTENTS page . TITLE PAGE ... ...................... i ABSTRACT • • • 1 1 TABLE OF CONTENTS • i v LIST OF FIGURES v i LIST OF TABLES . . . . . . . v i i LIST OF P L A T E S « • « • • » v i i 1 INTRODUCTION **• ° • • • • « e » » « » » « e » » » » » . • « • « • 1 MATERIALS A N D METHODS 3 D e s c r i p t i o n o f h a b i t a t s • • • e # . « * « « « . » « « « « « » . « . 3 FiGXcL HietllO(3.S • • e e e t « « e * Q a o « 0 « e o « o « c o 0 « o « o e « « ^ Xiaboxa'cory m s t t i o d s « » o o » c « « o « * « e 0 c e o * e e o » o 6 « « o 3 Asj© ciet ©jtmiiiatxon f o * « * « » e * c « « * « » « « o « « » * o o « « « ^ RESULTS 9 The male reproductive cycle 9 I n f a n t i l e 11 . Developing 1 3 Functional 17 Degenerate 20 The female reproductive cycle 2 3 I n f a n t i l e e 24-Proestrus 26 Estrus 28 3? JC*3^ ]Qar i t • • • e e « o e 0 « e o 0 * » f e o 0 0 « c « » t > t e « e o * « 3-1 Lactating 3 3 Anoestrus -. 3 6 The breeding season ........ \\ 3 8 F©OTJm.(3.it\"y\" • • • • f l o 0 « 0 C 9 e e o « o e 0 e o » « « e c » * 0 O * * « » ^ 3 0*V*lllat i 0*fl X*atO « « o o « « * e * • e o o a v o e c a c e o e o * ^ * 3 Preimplantation losses 4-5 Eoib2?yo conribs « « o c 0 * o « t c » * « * » « o e « « o e « o * « Embryo resorptions 4-7 Frequency of breeding females........... 5 0 Reproduction i n r e l a t i o n to Population Level. 5 2 Reproduction In r e l a t i o n to food 5 3 V page DISCUSSION , . 58 The r e p r o d u c t i v e c y c l e , . . 58 The male c y c l e 58 The f e m a l e c y c l e 58 Age a t m a t u r i t y 59 The b r e e d i n g season 60 T i m i n g o f b r e e d i n g 60 Y e a r l y v a r i a t i o n s 60 E f f e c t s o f weather 6 l D u r a t i o n o f b r e e d i n g 63 P o s s i b l e i n f l u e n c e s o f h a b i t a t . . . . 0 6k Male and female s y n c h r o n y 65 Y e a r l y v a r i a t i o n 66 E f f e c t o f d e n s i t y dependent f a c t o r s . . . . . . 66 E f f e c t o f foods 67 N a t u r e o f t h e c o n i f e r cone c r o p s 68 Advantages o f p i n e cone c r o p s o v e r f i r cone c r o p s , 69 P o s s i b l e c o n t r o l o f b r e e d i n g 71 ACKNOWLEDGMENTS 83 LITERATURE CITED. 84 v i L I S T C F F I G U R E S F I G U R E 1. Dried eye lens weight-age s c a l e , tabulated from 59 animals aged independently by tooth wear and c l o s u r e of the raidsagittal c r e s t . 2 . Seasonal changes In the mean leng t h of male reproductive- organs. Taken d u r i n g (A) the 1966 breeding season on Vancouver > I s l a n d and (B) d u r i n g the 19&7 breeding season on Vancouver I s l a n d and i n the i n t e r i o r of B r i t i s h Columbia, 3. The d u r a t i o n of various reproductive stages of males and females. P l o t t e d as the period between the c o l l e c t i n g of the f i r s t and l a s t animal i n each p a r t i c u l a r stage. (A) The I 9 6 7 breeding season on Vancouver I s l a n d and i n the i n t e r i o r of B r i t i s h Columbia. (B) The I 9 6 6 breeding season on Vancouver I s l a n d h. The frequency of l a c t a t i o n as i n d i c a t e d by the .condition of the n i p p l e s i n 1 9 6 6 , 19^7 • and of p r e v i o u s l y c o l l e c t e d animals i n the Vertebrate Museum at the U n i v e r s i t y of B r i t i s h Columbia v i i L I S T OP TABLES TABLE page I The o v u l a t i o n r a t e as i n d i c a t e d by-c o r p o r a l u t e a c o u n t s o f a l l b r e e d i n g f e m a l e s . T a b u l a t e d by age, s e a s o n , y e a r and l o c a t i o n . . - . *l4 I I P r e i m p l a n t a t l o n l o s s e s as i n d i c a t e d by t h e d i f f e r e n c e between t h e number o f o v u l a t i o n s i t e s and i m p l a n t a t i o n s i t e s . T a b u l a t e d by age, seas o n , y e a r &11GL 1 OGStfc 3. O H © e o « o e e o « » « c o o v o o o e « » e e » « « 9 0 « o o e e o o 4^*6 I I I Embryo counts as i n d i c a t e d by v i s i b l e embryos o r i m p l a n t a t i o n s i t e s . R e s o r b i n g embryos i n c l u d e d . T a b u l a t e d by age, se a s o n , y e a r and l o c a t i o n . . . . . . . . 0 0 0 . 0 . 0 . 0 . . . . . 48 I V P o s t i m p l a n t a t i o n l o s s e s as i n d i c a t e d by t h e number o f v i s i b l e r e s o r b i n g embryos. T a b u l a t e d by age, s e a s o n , V P e r c e n t females b r e e d i n g a f t e r t h e o n s e t o f t h e b r e e d i n g season as i n d i c a t e d by p r o e s t r u s , pregnancy o r l a c t a t i o n . T a b u l a t e d by age, y e a r V I R e l a t i v e p o p u l a t i o n l e v e l s as i n d i c a t e d by t h e number o f c a l l s h e a r d p e r hour and t h e number k i l l e d p e r day. T a b u l a t e d by y e a r and l o c a t i o n . . ........ 54 V I I Frequency o f g e n e r a l f o o d t y p e s found i n s q u i r r e l stomachs. T a b u l a t e d as a p e r c e n t o f t h e t o t a l number o f stomachs examined v l i i L I S T OF PLATES PLATE page I Vancouver I s l a n d h a b i t a t 7 3 A. An open r o c k y s i t e . B. Dense v e g e t a t i o n . IX l i l t 63?!. O fa&Di fc&*fc « # \"o • • « « « o e » » o o « * o e « « « » e e « 7 ^ A. An open s i t e . Bo Dense v e g e t a t i o n . I l l S e a s o n a l changes i n t h e t e s t e s . ............... 7 5 A. I n f a n t i l e . B. D e v e l o p i n g . C. E a r l y f u n c t i o n a l . D. L a t e f u n c t i o n a l . E. D e g e n e r a t i n g . I V S e a s o n a l changes i n t h e e p i d i d y m i d e s . 7 6 A. I n f a n t i l e . 3. D e v e l o p i n g . C. F u n c t i o n a l . D. D e g e n e r a t i n g . V S e a s o n a l changes i n the s e m i n a l v e s i c l e s . 7 7 A. I n f a n t i l e . B . E a r l y d e v e l o p i n g . C. F u n c t i o n a l ( C i , i i , i i i ) C o n s e c u t i v e s t a g e s o f e p i t h e l i u m development. D. L a t e f u n c t i o n a l . V I S e a s o n a l changes i n t h e p r o s t a t e . «. 7 8 A. I n f a n t i l e . B . E a r l y d e v e l o p i n g . C. F u n c t i o n a l ( i ) e a r l y ( i i ) l a t e D. Degenerate. V I I S e a s o n a l changes i n t h e v a g i n a 7 9 A. I n f a n t i l e . B . E a r l y P r o e s t r u s . C. E s t r u s . D. L a t e Pregnancy. E. E a r l y a n o e s t r u s . i x PLATE page V I I I S e a s o n a l changes i n t h e u t e r u s , I X X 80 A. I n f a n t i l e . B. E s t r u s . C. E a r l y l a c t a t i o n . D. A n o e s t r u s ( i ) w i n t e r ( i i ) summer S e a s o n a l changes A. I n f a n t i l e i n t h e o v a r y • ( i ) t h r e e t o f o u r months o l d ( i i ) f o u r t o f i v e months o l d n e a r i n g p r o e s t r u s 81 ( i i i ) B. P o s t o v u l a t o r y . C. W i n t e r a n o e s t r u s Changes i n t h e c o r p o r a l u t e a . . A. Pregnancy and l a c t a t i o n . ( i ) e a r l y pregnancy ( i i ) l a t e pregnancy ( i i i ) l a c t a t i o n . B. L a t e l a c t a t i o n . C. E a r l y a n o e s t r u s . 82 INTRODUCTION The r e d s q u i r r e l ( T a m i a s c i u r u s h u d s o n i c u s ) i s a common i n h a b i t a n t o f t h e c o n i f e r o u s f o r e s t s o f N o r t h A m e r i c a . A l t h o u g h i t i s e a s i l y o b s e r v e d a n d . g e n e r a l l y abundant, much o f i t s b a s i c b i o l o g y i s u n r e c o r d e d . R e p r o d u c t i o n i s one f a c e t o f t h e r e d s q u i r r e l ' s b i o l o g y t h a t i s n o t w e l l documented, p a r t i c u l a r l y i n t h e west. T h i s s t u d y concerns t h e r e d s q u i r r e l s T a m i a s c i u r u s h u d s o n i c u s l a n u g i n o s u s and T a m i a s c i u r u s h u d s o n i c u s s t r e a t o r l . C o l l e c t i o n s were made o f T.h a l a n u g i n o s u s on s o u t h e r n Vancouver I s l a n d from O c t o b e r 19&5 *° September 1967,, T o h . s t r e a t o r l was s t u d i e d i n t h e v i c i n i t y o f P r i n c e t o n , B„C. from J a n u a r y I967 t o October 1967. O b s e r v a t i o n s were made on t h e l i f e h i s t o r y i n o r d e r t o e v a l u a t e t h e y e a r l y and s e a s o n a l r e p r o d u c t i v e changes w i t h p a r t i c u l a r emphasis on t h e v a r i a t i o n i n r e p r o d u c t i v e performance i n r e l a t i o n t o age, f o o d , s e a s o n , and p o p u l a t i o n d e n s i t y . I n a d d i t i o n , h i s t o l o g i c a l p r e p a r a t i o n s were made o f male and female organs t o d e t e r m i n e t h e y e a r l y c y c l e s as w e l l as t h e e x a c t r e p r o d u c t i v e c o n d i t i o n o f each a n i m a l . I m p o r t a n t p r e v i o u s f i e l d s t u d i e s on t h e r e p r o d u c t i o n o f t h i s s p e c i e s a r e t h o s e o f Layne (195^) and S m i t h (1965). Layne*s s t u d y I n c l u d e s t h e g r o s s s e a s o n a l changes i n t h e r e p r o d u c t i v e organs o f Toh. l o q u a x i n New York. S m i t h s s s t u d y i n c l u d e s d a t a on l i t t e r s i z e and b r e e d i n g seasons - 2 -f o r t h e Douglas s q u i r r e l ( T a m i a s c l u r u s d o u g l a s l ) and t h e r e d s q u i r r e l (T.h. s t r e a t o r l ) i n B r i t i s h C olumbia. The anatomy o f t h e male r e p r o d u c t i v e t r a c t has been d e s c r i b e d by Mossman, Lavxlah, and B r a d l e y ( 1 9 3 2 ) . MATERIALS AND METHODS Red s q u i r r e l s were c o l l e c t e d m o n t h l y , e x c e p t when p r e v e n t e d by heavy snow o r f o r e s t f i r e danger. A l l a n i m a l s , w i t h t h e e x c e p t i o n o f a few.road k i l l s , were o b t a i n e d w i t h a .410 s h o t g u n . One hundred and s i x t y - n i n e a n i m a l s were t a k e n on Vancouver I s l a n d d u r i n g 1965-66 and 51 i n 1967. Two hundred and t w e n t y - t h r e e were t a k e n from t h e i n t e r i o r o f B r i t i s h Columbia i n I967. The a r e a s s t u d i e d on V a n c o i i v e r I s l a n d a r e i n t h e C o a s t a l Douglas F i r zone ( K r a j i n a , 1965) and g e n e r a l l y c o n s i s t o f open r o c k y b l u f f s where Douglas f i r ( P s e u d o t s u g a m e n z l e s l i ) and l o d g e p o l e p i n e (Pinu£ o o n t o r t a ) a r e t h e dominant t r e e s ( P l a t e I ) . Other t r e e s on t h e a r e a i n c l u d e r e d a l d e r ( A l n u s r u b r a ) , w e s t e r n hemlock (Tsuga h e t e r o p h y l l a ) and a r b u t u s ( A r b u t u s m e n z l e s l i ) . S a l a l ( G a u l t h e r i a s h a l l o n ) i s t h e dominant shrub b e n e a t h t h e t r e e canopy and k i n n l k i n n i k ( A r c t o s taphy I o s u v a - u r s 1 ) , h a i r y m a n z a n i t a (Arctostaphy 1os c o l u m b l a n a ) , and ocean s p r a y ( H o i o d l s o u s d i s c o l o r ) a r e common on open s i t e s . The c l i m a t e o f t h e s e a r e a s i s v e r y m i l d . The mean a n n u a l t e m p e r a t u r e averages 50°F, r a i n f a l l i s g r e a t e r t h a n 50\" and s n o w f a l l a v e r a g e s l e s s t h a n 30\". The s t u d y a r e a i n t h e i n t e r i o r o f B r i t i s h C o l u m b i a was chosen f o r I t s s i m i l a r i t y t o t h e i s l a n d h a b i t a t . C o l l e c t i n g was done w i t h i n t h e I n t e r i o r Douglas F i r zone n e a r P r i n c e t o n where t h e dominant t r e e s a r e l o d g e p o l e p i n e (P. c o n t o r t a ) and Douglas f i r (P. m e n z i e s i i ) , a l t h o u g h ponderosa p i n e ( P i n u s pondergsa) and Engelraann s p r u c e ( P i c e a engelmannl) a r e common on c e r t a i n s i t e s . The h a b i t a t i s more open t h a n t h a t found on Vancouver I s l a n d ( P l a t e I I ) . S o o p a l a l l i e ( S h e p h e r d l a canadensis)„ r e d - o s i e r dogwood (Cornus s t o l o n i f e r a ) and snowbrush (Ceanothus v e l u t i n u s ) a r e t h e dominant s h r u b s . The c l i m a t e I s d r i e r t h a n Vancouver I s l a n d w i t h an a n n u a l p r e c i p i t a t i o n o f l e s s t h a n 22\". S n o w f a l l I s between 30 and 70\" a l t h o u g h t h e mean a n n u a l t e m p e r a t u r e i s ^9°P« Specimens were weighed and measured as soon a f t e r c o l l e c t i n g as p o s s i b l e . A n o t e was made o f each a n i m a l ' s a c t i v i t i e s o r l o c a t i o n a t t h e t i m e o f c o l l e c t i o n . The c o n d i t i o n o f t h e n i p p l e s and v u l v a o f females and t h e scr o t u m o f t h e males was r e c o r d e d . E y e b a l l s were removed and s t o r e d i n 10% b u f f e r e d f o r m a l i n f o r u s e as a c r i t e r i o n o f age by eye l e n s e w e i g h t . The g e n e r a l c o n d i t i o n o f t h e r e p r o d u c t i v e t r a c t was n o t e d , and t h e u t e r i , vaginae,, and o v a r i e s o f females were measured. The c o r p o r a l u t e a , embryos o r p l a c e n t a l s c a r s were cou n t e d when p o s s i b l e . I n males t h e t e s t e s , s e m i n a l v e s i c l e s , and p r o s t a t e g l a n d s were measured. A l l r e p r o d u c t i v e t r a c t s were f i x e d I n B o u i n s f i x a t i v e f o r t h r e e days and s t o r e d i h 70^ e t h y l a l c o h o l . Stomachs - 5 -.were.noted as f u l l , h a l f f u l l , l i t t l e o r empty and t h e p r e s e n c e o f g e n e r a l f o o d t y p e s r e c o r d e d . R e p r e s e n t a t i v e m o n t h l y stomach samples were s t o r e d i n 10$ f o r m a l i n i n case c l o s e r e x a m i n a t i o n became d e s i r a b l e . S k u l l s were c l e a n e d d u r i n g 1965=66 t o be used i n e s t a b l i s h i n g an eye l e n s w eight-age s c a l e . S p e c i a l a t t e n t i o n was p a i d t o s i g n s o f s q u i r r e l f e e d i n g such as s t o r e d f o o d s , d i g g i n g s , and cone remains i n middens. The number o f c a l l s h e a r d p e r u n i t t i m e was n o t e d f o r d i f f e r e n t t i m e s d u r i n g t h e day i n o r d e r t o get a r e l a t i v e i n d e x o f p o p u l a t i o n d e n s i t y . One hour was t h e u s u a l t i m e p e r i o d used on Vancouver Island„ Because o f t h e much g r e a t e r number o f c a l l s h e a r d , 15 m i n u t e p e r i o d s were r e c o r d e d a t P r i n c e t o n . A p r i l and May o n l y were used f o r t h i s i n d e x s i n c e t h e s e months i n c l u d e d t h e b r e e d i n g seasons o f b o t h y e a r s , b e f o r e t h e young o f t h e y e a r were o u t . I n t h e l a b o r a t o r y , a r e p r e s e n t a t i v e sample o f each month 8s c o l l e c t i o n o f r e p r o d u c t i v e organs was trimmed, embedded i n p a r a f f i n and s e c t i o n e d a t 7 . The o v a r i e s o f a l l f e m a les i n r e p r o d u c t i v e c o n d i t i o n , as w e l l as a sample o f a l l o t h e r f e m a l e s , were s e r i a l l y s e c t i o n e d i n o r d e r t o g e t a c c u r a t e counts o f c o r p o r a l u t e a , c o r p o r a a l b l c a n t i a , and f o l l i c l e s . A l l s e c t i o n s were s t a i n e d w i t h D e l a f i e l d s h a e m a t o x y l i n and e o s i n . -6-Age was d e t e r m i n e d by t h e use o f t h e d r i e d eye l e n s w e i g h t t e c h n i q u e d e v e l o p e d by L o r d (1959)* Each f i x e d l e n s .was c l e a n e d o f a l l v i t r e o u s humor, p l a c e d I n a s m a l l v i a l and d r i e d f o r 72 hours a t 65°C. Each d r i e d l e n s was t h e n weighed t o t h e n e a r e s t t e n t h o f a m i l l i g r a m on an e l e c t r i c b a l a n c e . A t f i r s t b o t h l e n s e s were weighed, b u t t h e maximum d i f f e r e n c e found i n 17 p a i r s o f l e n s e s was ,2mg, so o n l y one l e n s was used t h e r e a f t e r . S i n c e no known age a n i m a l s were a v a i l a b l e , an a c c u r a t e eye l e n s age s c a l e c o u l d n o t be d e t e r m i n e d . I t was p o s s i b l e , however, t o s e p a r a t e a n i m a l s g r e a t e r t h a n one y e a r o l d from a n i m a l s l e s s t h a n one y e a r o l d t h r o u g h t h e use o f o t h e r c h a r a c t e r i s t i c s ; namely, t o o t h wear and m i d s a g i t t a l c r e s t c l o s u r e . One hundred and f i f t y - o n e s k u l l s were c l a s s e d as j u v e n i l e ( l e s s t h a n one y e a r o l d ) o r a d u l t ( g r e a t e r t h a n one y e a r o l d ) by t o o t h wear. S i n c e t o o t h wear can v a r y w i t h f e e d i n g c o n d i t i o n s t h e s k u l l s were a g a i n c l a s s i f i e d as a d u l t s o r j u v e n i l e s by t h e degree o f c l o s u r e o f t h e m i d s a g i t t a l c r e s t . Those w i t h f u l l y c l o s e d c r e s t s were c o n s i d e r e d a d u l t s , and t h o s e w i t h open c r e s t s were c o n s i d e r e d j u v e n i l e s . The eye l e n s w e i g h t was p l o t t e d f o r 59 o f t h e s e a n i m a l s i n w h i c h t h e age was t h e same by b o t h methods ( f i g . 2 ) . Once t h e eye l e n s w e i g h t s c a l e was co m p l e t e d , t h e age was d e t e r m i n e d on t h e b a s i s o f eye l e n s w e i g h t a l o n e . I n F i g u r e I . D r i e d eye l e n s weight-age s c a l e , t a b u l a t e d from 59 a n i m a l s aged i n d e p e n d e n t l y by t o o t h wear and c l o s u r e o f t h e m i d s a g i t t a l c r e s t . -7-- 8 -c a s e s where t h e e y e b a l l s were destroyed., t h e a n i m a l s were aged on t h e b a s i s o f s k u l l c h a r a c t e r i s t i c s , body s i z e , w e i g h t and c o n d i t i o n o f t h e r e p r o d u c t i v e t r a c t . RESULTS The Male R e p r o d u c t i v e C y c l e The anatomy o f t h e male r e p r o d u c t i v e t r a c t o f T a m i a s c i u r u s h u d s o n i c u s has been d e s c r i b e d by Mossman, L a w l a h , and B r a d l e y (1932). B a s i c a l l y t h e t r a c t c o n s i s t s o f p e r m a n e n t l y s c r o t a l t e s t e s , a s i n g l e compound t u b u l a r p r o s t a t e g l a n d , a p a i r o f s a c - l i k e t u b u l a r s e m i n a l v e s i c l e s and a p a i r o f v e s t i g i a l Cowpers g l a n d s . A l l b u t t h e Cowpers g l a n d s a r e c o n s i d e r e d i n t h e p r e s e n t s t u d y . Extreme s e a s o n a l changes b o t h i n g r o s s s i z e and h i s t o l o g i c a l s t r u c t u r e o c c u r i n t h e r e p r o d u c t i v e o r g a n s . These changes i n v o l v e a l l a c c e s s o r y as w e l l as p r i m a r y r e p r o d u c t i v e o r g a n s . The r e p r o d u c t i v e c o n d i t i o n was d e t e r m i n e d by t a b u l a t i n g t h e c h a r a c t e r i s t i c s o f a l l r e p r o d u c t i v e o r g a n s , r a t h e r t h a n j u s t t h e t e s t e s and e p i d i d y m i d e s . U s i n g two i n d e p e n d e n t l y d e r i v e d c r i t e r i a , r e p r o d u c t i v e c o n d i t i o n and age a p p r o x i m a t i o n , t h e males a r e c l a s s i f i e d i n t o f o u r major grou.ps; i n f a n t i l e , d e v e l o p i n g , f u n c t i o n a l and d e g e n e r a t e . I n f a n t i l e males a r e t h o s e t h a t were b o r n w i t h i n t h e y e a r ; t h a t i s , t h e y a r e l e s s t h a n one y e a r o l d and show no s i g n s o f h a v i n g e x p e r i e n c e d any r e p r o d u c t i v e development. D e v e l o p i n g males i n c l u d e a n i m a l s o f a l l ages, i n c l u d i n g young o f t h e y e a r t h a t show an i n c r e a s e i n t h e s i z e o f r e p r o d u c t i v e organs a l o n g w i t h h i s t o l o g i c a l changes, b u t w h i c h a r e n o t s e x u a l l y f u l l y f u n c t i o n a l . F u n c t i o n a l males a r e a n i m a l s -10-o f a l l ages t h a t possess l a r g e a c t i v e r e p r o d u c t i v e organs and appear t o be c a p a b l e o f b r e e d i n g s u c c e s s f u l l y . T h i s i n c l u d e s o n l y t h o s e males i n which a l l r e p r o d u c t i v e organs a r e f u n c t i o n a l . D e g e n e r a t i n g males i n c l u d e a n i m a l s of a l l ages t h a t have been s e x u a l l y f u n c t i o n a l b u t appear t o have l o s t t he c a p a c i t y t o b r e e d . The d i s t i n c t i o n between d e v e l o p i n g , f u n c t i o n a l and d e g e n e r a t i n g males i s o f t e n d i f f i c u l t t o make so t h a t h i s t o l o g i c a l c r i t e r i a i n t h e s e cases i s p a r t i c u l a r l y u s e f u l . The g e n e r a l c l a s s i f i c a t i o n i s s i m i l a r t o t h a t made f o r the f o x s q u i r r e l ( S c i u r t i s n l g e r ) t e s t e s ( K i r k p a t r l c k , 1955) a n d male a c c e s s o r y organs o f t h e f o x s q u i r r e l and gra y s q u i r r e l ( S c i u r u s c a r o l l n e n s i s ) (Mossraan, Hoffman and K i r k p a t r l c k , 1955). -11-I n f a n t i l e M a l e s I n f a n t i l e males a r e p r e s e n t i n t h e p o p u l a t i o n f o r most o f t h e y e a r . They a r e a b s e n t o n l y between t h e t i m e o f f i r s t b r e e d i n g i n t h e s p r i n g and t h e time when t h e young l e a v e t h e n e s t about two months l a t e r . The young r e m a i n i n t h e i n f a n t i l e c o n d i t i o n u n t i l about s i x t o t e n months o l d . d e p e n d i n g on when t h e y were b o r n . They b e g i n t o come i n t o b r e e d i n g c o n d i t i o n i n J a n u a r y o r F e b r u a r y , a l o n g w i t h t h e o l d e r males« Throughout t h e i n f a n t i l e pha.se t h e scrotum i s b a r e l y d i s c e r n a b l e and t h e p e n i s i s s m a l l , u s t i a l l y b e i n g l e s s t h a n 40 mm i n l e n g t h . The t e s t e s , w h i c h a r e about 6 mm i n l e n g t h , a r e t y p i c a l l y s c r o t a l i n p o s i t i o n , a l t h o u g h t h e y a r e sometimes found i n t h e i n g u i n a l c a n a l o r a b dominal c a v i t y . I n t e x t u r e t h e t e s t e s a r e f i r m and smooth, and f i n e s t r a i g h t b l o o d v e s s e l s can be seen i n t h e t u n i c a a l b u g i n e a . The e p i d i d y m i d e s a r e s m a l l and compact, and a l l a c c e s s o r y organs r e m a i n s m a l l and i n c o n s p i c u o u s t h r o u g h o u t t h e i n f a n t i l e p e r i o d . On each s i d e o f t h e a n t e r i o r u r e t h r a a r e s i t u a t e d t h e s m a l l , w i n g - l i k e s e m i n a l vesicles„ These a r e about 3 mm i n l e n g t h and f r e q u e n t l y h i d d e n i n a mass o f f a t . J u s t c a u d a l t o t h e s e g l a n d s l i e s t h e p r o s t a t e , a s i n g l e g l a n d about 3 mm l o n g and 2 mm wide t h a t i s i n t i m a t e l y a s s o c i a t e d w i t h t h e v e n t r a l u r e t h r a . M i c r o s c o p i c a l l y , t h e i n f a n t i l e t e s t e s p o s s e s s c l o s e l y packed s e m i n i f e r o u s =12= t u b u l e s a v e r a g i n g 7 0 ^ i n d i a m e t e r ( P l a t e I I I A ) . These t u b u l e s , w h i c h a r e bound w i t h smooth basement membranes, c o n t a i n l o o s e l y a s s o c i a t e d rows o f s p e r m a t o g o n i a , p r i m a r y s p e r m a t o c y t e s and S e r t o l i c e l l s . There a r e no open l u m i n a i n t h e t u b u l e s , a l t h o u g h t h e c e n t r e o f t h e t u b u l e s f r e q u e n t l y c o n s i s t s o f an a c i d o p h i l i c m a t r i x r a t h e r t h a n c e l l u l a r components. Between t h e t u b u l e s t h e r e a r e s c a t t e r e d L e y d i g c e l l s , w h i c h a r e g e n e r a l l y l e s s t h a n 9/< i n d i a m e t e r . These p o s s e s s d a r k i r r e g u l a r n u c l e i and v e r y l i t t l e c y t o p l a s m . The e p i d i d y m i d e s d u r i n g t h e i n f a n t i l e p e r i o d c o n s i s t o f s m a l l round t u b u l e s w i t h open l u m i n a t h a t a r e l i n e d w i t h columnar e p i t h e l i u m about 12/< i n h e i g h t ( P l a t e I V A ) . These columnar c e l l s c o n t a i n o b l o n g b a s a l n u c l e i w i t h s e v e r a l n u c l e o l i and a v e r y t h i n a r e a o f a p i c a l c y t o p l a s m . No s e c r e t i o n d r o p l e t s ©an be seen i n t h e s e c e l l s . The r e s t o f t h e b u l k o f t h e e p i d i d y m i d e s c o n s i s t s c h i e f l y o f l o o s e c o n n e c t i v e t i s s u e . The s e m i n a l v e s i c l e s o f the i n f a n t i l e male p o s s e s s s e c r e t o r y t u b u l e s w h i c h a r e s m a l l and few i n number ( P l a t e V A ) . Much o f the g l a n d c o n s i s t s o f h e a v i l y n u c l e a t e d c o n n e c t i v e t i s s u e s e p a r a t e d by t h i n s t r i p s o f c o l l a g e n f i b r e s e A l t h o u g h t h e t u b u l e l u m i n a r e m a i n open t h e s e c r e t o r y e p i t h e l i u m l i n i n g them shows no s i g n o f a c t i v i t y . The s e c r e t o r y c e l l s a r e e l o n g a t e and t h e i r n u c l e i a r e l a r g e , b u t l i t t l e c y t o p l a s m i s p r e s e n t . - 1 3 -Th e p r o s t a t e a l s o c o n s i s t s m a i n l y o f h e a v i l y n u c l e a t e d c o n n e c t i v e t i s s u e , a l o n g w i t h s m a l l t u b u l e s . ( P l a t e V I A ) . A few o f t h e s e t u b u l e s p o s s e s s open l u m i n a b u t i n many the randomly o r i e n t e d e p i t h e l i a l c e l l s o c c l u d e t h e o p e n i n g s . I n t h e l a . t t e r c a s e , I n w h i c h t h e e p i t h e l i a l c e l l s a r e o r i e n t e d randomly, t h e r e does n o t appear t o be any t r u e s e c r e t o r y e p i t h e l i u m i n t h e t u b u l e s . There i s , however, a d i s t i n c t row o f o v a l n u c l e i about t h e p e r i p h e r y o f t h e t u b u l e s t h a t i s p r o b a b l y d e s t i n e d t o become the f u n c t i o n a l s e c r e t o r y e p i t h e l i u m . Taken t o g e t h e r , t h e male r e p r o d u c t i v e organs d u r i n g t h e i n f a n t i l e s t a g e a r e c h a r a c t e r i z e d by s m a l l t e s t e s p o s s e s s i n g c l o s e l y packed s e m i n i f e r o u s t u b u l e s t h a t a r e bounded by smooth basement membranes and w h i c h c o n t a i n no n a t u r a l l u m i n a . Open l u m i n a a r e found i n t h e e p i d i d y m i d e s and s e m i n a l v e s i c l e s and o c c a s i o n a l l y i n t h e p r o s t a t e , a l t h o u g h t h e e p i t h e l i a w i t h i n t h e s e g l a n d s p o s s e s s l i t t l e c y t o p l a s m and show no s i g n s o f s e c r e t o r y a c t i v i t y . D e v e l o p i n g D e v e l o p i n g males can be found i n t h e p o p u l a t i o n from l a t e December t o e a r l y March, depending on t h e y e a r . I t p r o b a b l y t a k e s an i n d i v i d u a l male l e s s t h a n a month t o d e v e l o p t o t h e f u n c t i o n a . 1 s t a t e . There appears t o be - I n -considerable synchrony among individuals i n development during t h i s period and the juveniles, although they have not bred before, undergo developmental changes at the same time as the older males. Gross changes during the period of development include an Increase i n s i z e and consplcuousness of the scrotum, along with a p a r t i a l shedding of the s c r o t a l f u r and a darkening of the s c r o t a l s k i n 0 The testes may vary from 8 to 16 mm In length. Blood vessels i n the tunica albuginea become conspicuous and the epididymides enlarge. Epididymal tubules are not externally conspicuous at this time. The seminal v e s i c l e s , i n which the tubules are evident externally, may be as large as 1? mm long during t h i s period of development. Although quite long, they are not as swollen as those of functional males. Two d i s t i n c t regions of the seminal v e s i c l e s become evident; a large, promlnant portion showing distended tubules and a smaller d o r s o - l a t e r a l portion made up of small tubules. The developing prostate may be as large as 6 mm long and k mm wide and forms a thick, l i g h t coloured bulge on the ventral urethra. Because of i t s compact form, the gross morphology of the prostate does not show any clear cut i n d i c a t i o n of i t s p h y s i o l o g i c a l state. A much more accurate determination can be made h i s t o l o g i c a l l y . Microscopically, the testes show several d i s t i n c t features during the developmental phase, a l l of which -15-g e n e r a l l y o c c u r s i m u l t a n e o u s l y . The basement membranes around t h e s e m i n i f e r o u s t u b u l e s become t h i n n e r as t h e t u b u l e s i n c r e a s e i n d i a m e t e r . As t h e t u b u l e s i n c r e a s e , t h e y a l s o s e p a r a t e , l e a v i n g l a r g e i n t e r t u b u l a r spaces t h a t c o n t a i n d i s t i n c t clumps o f L e y d i g c e l l s ( P l a t e I I I B) The c e l l s a r e about 11^ i n d i a m e t e r and t h e y g r a d u a l l y a c q u i r e an i n c r e a s i n g amount o f c y t o p l a s m . W i t h i n t h e s e m i n i f e r o u s t u b u l e s t h e r e i s s p e r m a t o g e n i c a c t i v i t y and spermatozoa may be seen a t t h e time t h a t t h e t u b u l e l u m i n a open. The i n c r e a s e I n t h e g r o s s s i z e o f t h e e p l d i d y m i d i s c h i e f l y a r e s u l t o f i n c r e a s i n g t u b u l e d i a m e t e r . ( P l a t e I V B ) . L a r g e open l u m i n a a r e p r e s e n t b u t may be p a r t i a l l y o c c l u d e d by c y t o p l a s m i c f i l a m e n t s p r o j e c t i n g from t h e d e v e l o p i n g a p i c a l c y t o p l a s m o f t h e s e c r e t o r y e p i t h e l i u m . The e p i t h e l i u m I t s e l f i s a p s e u d o s t r a t i f i e d columnar c e l l l a y e r . As t h e t u b u l e s i n c r e a s e t h e i n t e r t u b u l a r c o n n e c t i v e t i s s u e becomes t h i n and compact. Changes w i t h i n t h e s e m i n a l v e s i c l e s a l s o i n v o l v e b o t h t h e t u b u l e s and t h e c o n n e c t i v e t i s s u e , t h e c o n n e c t i v e t i s s u e becoming t h i n as t h e t u b u l e s i n c r e a s e i n s i z e . W i t h i n t h e t u b u l e s t h e p r e v i o u s l y jumbled a r r a y o f e p i t h e l i a l c e l l s forms a b a s a l p s e u d o s t r a t i f i e d l a y e r ( P l a t e V B ) . F u r t h e r t u b u l e development r e s u l t s i n t h e f o r m a t i o n o f a t h i n l a y e r o f a p i c a l c y t o p l a s m and t h e p r e s e n c e o f s e c r e t i o n d r o p l e t s w i t h i n them. Most o f t h e g l a n d growth r e s u l t s from t h e tremendous -16-I n c r e a s e i n t h e s i z e o f t h e l u m i n a i n c o n j u n c t i o n w i t h t h e f o r m a t i o n o f s e c r e t i o n d r o p l e t s . D u r i n g l a t e development th e s e c r e t o r y e p i t h e l i u m becomes thrown i n t o f o l d s and t h e a p i c a l c y t o p l a s m becomes v e r y t h i c k . D e v e l o p m e n t a l changes i n t h e p r o s t a t e d i f f e r f rom t h o s e i n t h e s e m i n a l v e s i c l e s i n t h a t t h e p r o s t a t e does n o t form l a r g e l u m i n a ( P l a t e V I B ) . The t u b u l e l u m i n a a r e c o n s i d e r a b l y s m a l l e r i n t h e p r o s t a t e b u t t h e t u b u l e s a r e much more numerous, and a r e l o b u l a t e d . The t u b u l e s a r e s e p a r a t e d by t h i c k c o n n e c t i v e t i s s u e l a y e r s . W i t h i n t h e t u b u l e s and between t h e l o b u l e s a r e t h i n l a y e r s o f c o n n e c t i v e t i s s u e . S m a l l open l u m i n a a r e o c c a s i o n a l l y seen b u t most l o b u l e s r e m a i n c l o s e d d u r i n g t h e d e v e l o p m e n t a l p e r i o d . The s e c r e t o r y e p i t h e l i u m i n t h e p r o s t a t e f i r s t forms a p s e u d o s t r a t i f i e d l a y e r and a c q u i r e s a d e f i n i t e a p i c a l c y r o p l a s m i c a r e a w h i c h o c c l u d e s t h e l u m i n a . On t h e b a s i s o f g r o s s o r gan morphology a l o n e I t i s d i f f i c u l t t o d e t e r m i n e t h e d e v e l o p m e n t a l s t a g e o f t h e male. M i c r o s c o p i c a l l y , however, t h e d e v e l o p m e n t a l phase can be r e a d i l y r e c o g n i z e d . The t e s t e s show e n l a r g e d , s e p a r a t i n g s e m i n i f e r o u s t u b u l e s t h a t may p o s s e s s open l u m i n a and spermatozoa. D i s t i n c t clumps o f L e y d i g c e l l s d e v e l o p i n t h e i n t e r t u b u l a r s p a c e s . The e p i d i d y m i d e s p o s s e s s e n l a r g e d t u b u l e s b u t no sperm. The p r o s t a t e d e v e l o p s an a c t i v e s e c r e t o r y c e l l l a y e r b u t w i t h few open l u m i n a and s e m i n a l v e s i c l e s p o s s e s s open l u m i n a w h i c h a r e -17-n o t g r e a t l y d i s t e n d e d , w i t h o n l y a few s e c r e t i o n d r o p l e t s . There does seem t o be a f a i r l y synchronous development o f t h e t e s t e s , p r o s t a t e and s e m i n a l v e s i c l e s b u t on o c c a s i o n a l l t h r e e have t o be s t u d i e d t o d e t e r m i n e t h e r e p r o d u c t i v e s t a t e o f t h e a n i m a l . F u n c t i o n a l M a l e s w i t h f u n c t i o n a l r e p r o d u c t i v e organs may be t a k e n from J a n u a r y u n t i l A ugust. The sc r o t u m i s l a r g e , and t h e s k i n i s d a r k and s p a r s e l y f u r r e d . The p e n i s i s g e n e r a l l y around 50 mm i n l e n g t h . The s i z e o f t h e f u n c t i o n a l male organs v a r i e s c o n s i d e r a b l y and some o v e r l a p o c c u r s between t h e s i z e o f d e v e l o p i n g , f u n c t i o n a l and d e g e n e r a t i n g o r g a n s . F o r t h i s r e a s o n t h e gross, s i z e i s n o t an a b s o l u t e i n d i c a t i o n o f o r g a n f u n c t i o n . T e s t i s l e n g t h v a r i e s from 16 t o 23 mm i n f u n c t i o n a l a n i m a l s . The t e s t e s a r e u s u a l l y f i r m i n t e x t u r e , b u t may become s l i g h t l y f l a c c i d as t h e se a s o n p r o g r e s s e s , and t h i c k prominent b l o o d v e s s e l s c a n be se e n i n t h e smooth, l i g h t c o l o u r e d t u n i c a a l b u g i n e a e . The l a r g e e p i d i d y m i d e s e x h i b i t a few l a r g e t u b u l e s t h a t r e m a i n d l s c e r n a b l e t o t h e naked eye t h r o u g h o u t t h e f u n c t i o n a l p e r i o d . The s e m i n a l v e s i c l e s a r e g e n e r a l l y l a r g e d i s t e n d e d g l a n d s t h a t v a r y i n l e n g t h from 13 t o 33 mm. The p r o s t a t e , always r e t a i n i n g a s o l i d t e x t u r e , r e a c h e s a maximum s i z e o f about 16 by 11 mm. -18-M i c r o s c o p i c a l l y , t h e t e s t e s p o s s e s s l a r g e s e m i n i f e r o u s t u b u l e s about 200^ i n d i a m e t e r . T h e i r l u m i n a , w h i c h c o n t a i n l o o s e l y a s s o c i a t e d spermatozoa and a l l s t a g e s o f s p e r m a t o g e n e s i s , appear t o i n c r e a s e i n s i z e as t h e f u n c t i o n a l s t a t e p r o g r e s s e s ( P l a t e I I I C and I I I D ) . L e y d i g c e l l s , w i t h a maximum d i a m e t e r o f about 15A occupy a c e n t r a l p o s i t i o n i n t h e l a r g e i n t e r t u b u l a r s p a c e s . A l t h o u g h t h e L e y d i g c e l l s d e c r e a s e i n d i a m e t e r t h r o u g h a l o s s i n c e l l c y t o p l a s m towards t h e end o f t h e f u n c t i o n a l p e r i o d , s e c r e t i o n v a c u o l e s r e m a i n e v i d e n t . F u n c t i o n a l L e y d i g c e l l s may be as s m a l l as 11^ i n d i a m e t e r . The f u n c t i o n a l e p i d i d y m i d e s do n o t show t h e same degree o f v a r i a t i o n as do t h e t e s t e s . A t h i c k a p i c a l c y t o p l a s m i s r e t a i n e d by t h e e p i t h e l i a l c e l l s o f t h e t u b u l e s and t h e whole e p i t h e l i u m I s m a i n t a i n e d a t a h e i g h t o f 20 t o 25/< o The t u b u l e l u m i n a a r e f r e e o f c y t o p l a s m i c f i l a m e n t s and r e m a i n f i l l e d w i t h sperm t h r o u g h o u t t h e f u n c t i o n a l p e r i o d ( P l a t e I V C ) . Changes i n t h e i n t e r t u b u l a r c o n n e c t i v e t i s s u e o f t h e e p i d i d y m i d e s a r e n o t e v i d e n t d u r i n g t h e f u n c t i o n a l phase. The s t r u c t u r e o f t h e s e m i n a l v e s i c l e s i s q u i t e v a r i a b l e a t t h i s t i m e . V a r i o u s s t a g e s o f e p i t h e l i u m development c a n be seen a t a l l t i m e s d u r i n g t h e b r e e d i n g s e a s o n and I t i s l i k e l y t h a t t h e t u b u l e s go t h r o u g h c y c l e s o f a c t i v i t y w h i c h , i n c r o s s s e c t i o n i s seen as -19-s e v e r a l s t a g e s w i t h i n one g l a n d . However a predominance o f one e p i t h e l i u m t y p e c a n u s u a l l y be seen i n any one g l a n d . The e a r l y f u n c t i o n a l e p i t h e l i u m shows a f o l d e d l a y e r o f a c t i v e columnar c e l l s w h i c h p o s s e s s e l o n g a t e , d a r k l y s t a i n e d , b a s a l n u c l e i ( P l a t e V G i ) . The a p i c a l c y t o p l a s m I n t h e s e c e l l s i s w e l l d e v e l o p e d and s e c r e t i o n d r o p l e t s a r e common. L a t e r s t a g e s p o s s e s s o v a l b a s a l n u c l e i , and t h e e p i t h e l i u m e v e n t u a l l y becomes a s i n g l e , c u l o i d a l c e l l l a y e r ( P l a t e V C i and V C i i ) . A t t h i s t i m e , f o l d i n g o f . t h e e p i t h e l i u m i s uncommon and r e l a t i v e l y few s e c r e t i o n d r o p l e t s a r e p r e s e n t . As t h e t u b u l e e v e n t u a l l y s h r i n k s , t h e r e i s a t h i c k e n i n g o f t h e e p i t h e l i u m t h r o u g h p s e u d o s t r a t i f i c a t i o n . The a p i c a l c y t o p l a s m i s t h i n b u t some s e c r e t i o n d r o p l e t s a r e s t i l l p r e s e n t ( P l a t e V D ) . The p r o s t a t e , a l t h o u g h r e t a i n i n g i t s s o l i d c o n s t i t u e n c y , a l s o shows e p i t h e l i a l changes t h r o u g h o u t t h e b r e e d i n g s e a s o n . The l o b u l e s p o s s e s s a s i n g l e e p i t h e l i a l c e l l l a y e r about 20/, i n h e i g h t and s e c r e t i o n d r o p l e t s a r e common n e a r and on t h e s u r f a c e o f t h e l a y e r . D u r i n g t h e e a r l y s t a g e s t h e c e l l s p o s s e s s a t h i c k a p i c a l c y t o p l a s m w h i c h g r a d u a l l y becomes r e d u c e d i n t h i c k n e s s . I n c o n j u n c t i o n w i t h t h i s r e d u c t i o n i n c e l l h e i g h t t h e l u m i n a open ( P l a t e V I C i and VI C i i ) . L a t e i n t h e f u n c t i o n a l p e r i o d t h e c e l l s appear c u b o i d a l , b e i n g as l i t t l e as 10^ i n h e i g h t . S e c r e t i o n d r o p l e t s a r e p r e s e n t even on t h e s e s m a l l c e l l s . The c o n n e c t i v e t i s s u e s e p a r a t i n g - 2 0 -t h e t u b u l e s and l o b u l e s remains t h i n d u r i n g most o f the f u n c t i o n a l p e r i o d , b u t may appear somewhat t h i c k e n e d as t h e g l a n d r e g r e s s e s d u r i n g t h e l a t e r s t a g e s . D e s p i t e v a r i a t i o n s i n o r g a n s i z e , t h e f u n c t i o n a l s t a t e i s c h a r a c t e r i z e d by s e v e r a l m i c r o s c o p i c c r i t e r i a . Spermatozoa a r e p r e s e n t i n b o t h t h e s e m i n i f e r o u s t u b u l e s and i n t h e e p i d i d y m i d e s . S e m i n a l v e s i c l e s p o s s e s s l a r g e open l u m i n a and s e c r e t i n g e p i t h e l i a l c e l l s . The p r o s t a t e a l s o p o s s e s s e s an a c t i v e s e c r e t o r y e p i t h e l i u m and open l u m i n a . Degenerate Once t h e male r e p r o d u c t i v e organs a r e no l o n g e r f u n c t i o n a l , complete d e g e n e r a t i o n o c c u r s r a p i d l y . The scr o t u m becomes f u l l y f u r r e d a l t h o u g h t h e h a i r s a r e g e n e r a l l y t i p p e d w i t h brown and t h e d a r k p i g m e n t a t i o n o f t h e integument i s l o s t . The p e n i s r e t a i n s a l e n g t h o f kO t o 5 0 mm. The t e s t e s s h r i n k , t h e t u n i c a t a k e on a b l u e t i n g e and t h e s u r f a c e o f t h e t u n i c a becomes w r i n k l e d . The e p i d i d y m i d e s t e n d t o remai n l a r g e i n r e l a t i o n t o t h e t e s t e s , b u t e v e n t u a l l y s h r i n k . The e p i d i d y m a l t u b u l e s become e x t e r n a l l y i n c o n s p i c u o u s and cannot be seen by t h e naked eye. Consequent t o t h e s e changes i n t h e t e s t e s , t h e a c c e s s o r y organs a l s o d e g e n e r a t e . S e m i n a l v e s i c l e s l o s e t h e i r t h i c k t u b u l a t e d appearance and become i n f a n t i l e - l i k e p r o j e c t i o n s about k mm l o n g w h i l e t h e p r o s t a t e becomes l e s s t h a n 7 by k mm i n l e n g t h and w i d t h -21-d a r k i n c o l o r , and \"rather i n c o n s p i c u o u s . H i s t o l o g i c a l l y , t h e t e s t e s show c l o s e l y packed t u b u l e s about 100^ i n d i a m e t e r w h i c h assume i r r e g u l a r s hapes. Basement membranes become t h i c k and w r i n k l e d . Germ c e l l l a y e r s a r e t h i n and a l l l u m i n a e v e n t u a l l y become c l o g g e d w i t h d e g e n e r a t e sperm and c e l l u l a r d e b r i s ( P l a t e I I I E ) . Only s p e r m a t o g o n i a , p r i m a r y s p e r m a t o c y t e s and S e r t o l i c e l l s r e m a i n i n t h e tubules„ The L e y d i g c e l l s l o s e t h e i r v a c u o l a t e d appearance, t h e i r c y t o p l a s m becomes s c a r c e , and t h e i r n u c l e i become d a r k , g i v i n g t h e I m p r e s s i o n t h a t t h e y a r e f u n c t i o n a l l y d e g e n e r a t e . The e p i d i d y m i d e s g r a d u a l l y assume t h e i n f a n t i l e form t h r o u g h a t h i c k e n i n g o f the c o n n e c t i v e t i s s u e , s h r i n k i n g o f t h e t u b u l e s and c l e a r i n g o f t h e l u m i n a . The f i r s t s i g n o f n o n f u n c t i o n i n t h e e p i d i d y m i d e s i n v o l v e s a d e g e n e r a t i o n o f t h e sperm and t h e p r e s e n c e o f some c e l l u l a r d e b r i s and l e u c o c y t e s ( P l a t e I V D ) . F u r t h e r changes show a r e d u c t i o n i n e p i t h e l i u m h e i g h t and a breakdown o f some o f t h e c e l l s . D e g e n e r a t i o n i n t h e s e m i n a l v e s i c l e s c o n s i s t s o f s u b t l e changes t h a t e s s e n t i a l l y i n v o l v e a l o s s o f s e c r e t i o n d r o p l e t s and a p i c a l c y t o p l a s m i n t h e s e c r e t o r y c e l l s , t h e breakdown o f some e p i t h e l i a l c e l l s and an a c c u m u l a t i o n o f d e b r i s w i t h i n t h e s h r i n k i n g l u m i n a . E v e n t u a l l y t h e s e m i n a l v e s i c l e s t a k e on t h e i n f a n t i l e f orm, showing s m a l l t u b u l e s s u p p o r t e d by t h i c k , h e a v i l y n u c l e a t e d c o n n e c t i v e t i s s u e . They d i f f e r from the i n f a n t i l e a n i m a l m a i n l y I n t h e maintenance o f more - 2 2 -a c l d o p h i l i c c o n n e c t i v e t i s s u e . P r o s t a t e d e g e n e r a t i o n b e g i n s w i t h a breakdown o f e p i t h e l i a l c e l l s and o c c l u s i o n o f t h e l u m i n a w i t h d a r k s t a i n i n g n u c l e i and c y t o p l a s m i c d e b r i s . C o i n c i d e n t a l w i t h t h i s i s a d e c r e a s e i n t u b u l e s i z e and number, and t h e f o r m a t i o n o f a heavy basement membrane. Many o f t h e l o b u l e s a r e l o s t and a r e r e p l a c e d by h e a v i l y n u c l e a t e d c o n n e c t i v e t i s s u e ( P l a c e V I D ) . The c o m p l e t e l y d e g e n e r a t e p r o s t a t e assumes the i n f a n t i l e form and c a n o n l y be d i s t i n g u i s h e d from th e i n f a n t i l e p r o s t a t e by a l a r g e r p o r t i o n o f c o l l a g e n i n t h e i n t e r t u b u l a r t i s s u e . Thus t h e d e g e n e r a t i n g male can be c h a r a c t e r i z e d by t h e p r e s e n c e o f d e g e n e r a t e sperm i n t h e e p i d i d y m i d e s r e s u l t i n g f i n a l l y i n t h e complete absence o f sperm. I n a d d i t i o n , t h e s e m i n i f e r o u s t u b u l e s t a k e on i r r e g u l a r s hapes, w r i n k l e d basement membranes, and e v e n t u a l l y l o s e open l u m i n a . L e y d i g c e l l s become s m a l l , f o r m i n g l o o s e l y a s s o c i a t e d clumps packed between the s e m i n i f e r o u s t u b u l e s . S e m i n a l v e s i c l e s l a c k s e c r e t i n g e p i t h e l i a l c e l l s and t h e p r o s t a t e shows a s l o u g h i n g o f t h e e p i t h e l i u m a l o n g w i t h a l o s s i n number o f l o b u l e s and t u b u l e s . Complete d e g e n e r a t i o n r e s u l t s i n i n f a n t i l e - l i k e organs t h a t a r e d i s t i n g u i s h e d from th e i n f a n t i l e a n i m a l s on t h e b a s i s o f a s l i g h t l y l a r g e r s i z e and a few h i s t o l o g i c a l c h a r a c t e r i s t i c s t h a t a r e n o t always r e l i a b l e . The d e g e n e r a t e a d u l t t e s t e s show more i r r e g u l a r s h a p e d s e m i n i f e r o u s t u b u l e s and more w r i n k l e d basement membranes - 2 3 -t h a n the i n f a n t i l e . The s e m i n a l v e s i c l e s possess c o n n e c t i v e t i s s u e t h a t i s q u i t e t h i c k i n the a d u l t and l e s s so i n the I n f a n t i l e . A c i d i p h i l i c c o l l a g e n i s prominent i n most a d u l t s e m i n a l v e s i c l e s and v e r y s c a r c e i n t h e i n f a n t i l e organs. S i m i l a r l y , the a d u l t p r o s t a t e shows a much h e a v i e r d e s p o s i t i o n o f c o l l a g e n t h a n t h e i n f a n t i l e . The Female R e p r o d u c t i v e C y c l e The female r e p r o d u c t i v e organs undergo s e a s o n a l changes t h a t a r e a l m o s t as extreme as t h o s e found i n the male. Layne (195^) d e s c r i b e d t h e g r o s s s e a s o n a l changes I n t h e male and female r e p r o d u c t i v e organs o f T.h. l o q u a x i n New York and t h e h i s t o l o g y o f t h e o v a r i e s has been d e s c r i b e d by Mossman (1966). I n the p r e s e n t s t u d y , t h e g r o s s and m i c r o s c o p i c changes i n the o v a r i e s , u t e r i and v a g i n a e were r e c o r d e d t h r o u g h o u t t h e y e a r so t h a t t h e e x a c t c o n d i t i o n o f any a n i m a l c o u l d be d e t e r m i n e d . F o r c o n v e n i e n c e , t h e female c y c l e was d i v i d e d i n t o s i x f u n c t i o n a l phases; i n f a n t i l e , a n o e s t r o u s , p r o e s t r o u s , e s t r o u s , p r e g n a n t , and l a c t a t i n g . These phases were d e f i n e d so t h a t the a n i m a l s c o u l d be c l a s s i f i e d on t h e b a s i s o f g r o s s form and, i f n e c e s s a r y , c o n f i r m e d m i c r o s c o p i c a l l y . I n d e p e n d e n t l y d e t e r m i n e d age d a t a a i d e d i n some o f t h e c l a s s i f i c a t i o n . The I n f a n t i l e females I n c l u d e o n l y t h o s e t h a t a r e t h e young o f the y e a r and have n e v e r been i n b r e e d i n g c o n d i t i o n . The a n o e s t r o u s s t a g e a p p l i e s t o those females t h a t have produced young p r e v i o u s l y , -24-o r a r e o l d enough t o produce young, b u t wh i c h a r e n e i t h e r b r e e d i n g n or p r e p a r i n g t o b r e e d . Young o f th e p r e v i o u s y e a r a r e c o n s i d e r e d a n o e s t r o u s i f th e y do no t b r e e d , o r show s i g n s o f development a t t h e t i m e when o t h e r s o f t h e i r age group do s o , and when t h e i r r e p r o d u c t i v e organs a r e i n s i m i l a r c o n d i t i o n t o a n o e s t r o u s a d u l t s . A l l o t h e r s t a g e s ( p r o e s t r o u s , e s t r o u s , p r e gnant and l a c t a t i n g ) i n c l u d e a l l s e x u a l l y a c t i v e age groups f o r t h e purpose o f h i s t o l o g i c a l d e s c r i p t i o n . I n f a n t i l e Female The i n f a n t i l e f e m a l e can f r e q u e n t l y be c l a s s i f i e d on t h e b a s i s o f e x t e r n a l c h a r a c t e r i s t i c s , u s u a l l y by the s i z e and shape o f t h e n i p p l e s w h i c h appear o n l y as p i n p o i n t s o f l i g h t brown p i g m e n t a t i o n on t h e s k i n . The v u l v a i s s m a l l and i m p e r f o r a t e and does n o t p r o t r u d e t o any g r e a t e x t e n t . When t h e s e e x t e r n a l f e a t u r e s a r e n o t d i s t i n c t , the morphology o f t h e r e p r o d u c t i v e t r a c t i s f r e q u e n t l y I n d i c a t i v e o f t h e i n f a n t i l e s t a g e . The I n f a n t i l e o v a r i e s and u t e r i a r e n o t c o n s p i c u o u s and a r e o f t e n found l o d g e d w i t h i n t h e p e l v i s . The u t e r u s i s r a r e l y more t h a n 20 mm l o n g by 1 mm wide and i s g e n e r a l l y around 1? mm l o n g , w h i l e t h e o v a r i e s , which remain h i d d e n w i t h i n t h e b u r s a , a r e about 3 nun by 2 mm i n s i z e and a r e seen as smooth o v a l s o f opaque t i s s u e . The v a g i n a , about 1 mm i n w i d t h i s s i t u a t e d a l m o s t e n t i r e l y w i t h i n the p e l v i s and i s s i m i l a r t o t h e u t e r u s i n appearance. - 2 5 -M i c r o s c o p l c a l l y , t h e i n f a n t i l e v a g i n a i s a s i m p l e t u b e - l i k e s t r u c t u r e made up o f s e v e r a l c o n c e n t r i c l a y e r s ( P l a t e V I I A ) . Beneath t h e t h i c k o u t e r a d v e n t i t i a l i e s a t h i n c i r c u l a r l y o r i e n t e d submucosa t h a t i s i n t e r s p e r s e d w i t h a few c o l l a g e n f i b r e s . The submucosa Is n o t s h a r p l y demarcated from the c o l l a g e n l c l a m i n a p r o p r i a and no d i s t i n c t g e r m l n a t i v u m can be seen between i t and t h e e p i t h e l i u m l i n i n g t h e v a g i n a l lumen. The l i n i n g e p i t h e l i u m c o n s i s t s o f a p s e u d o s t r a t i f i e d l a y e r o f c u b o i d a l c e l l s showing l i t t l e c y t o p l a s m and l y i n g a l o n g a r a t h e r c o n v o l u t e d lumen. The u t e r u s d u r i n g t h e i n f a n t i l e s t a g e shows s e v e r a l t i s s u e l a y e r s i n c r o s s s e c t i o n ( P l a t e V I I I A ) . The o u t e r myometrium, r o u g h l y 75# i n t h i c k n e s s , i s made up o f muscle c e l l s w h i c h p o s s e s s l i t t l e c y t o p l a s m and d a r k s t a i n i n g , e l o n g a t e n u c l e i . Two d i s t i n c t l a y e r s w i t h i n t h e myometrium a r e d i s c e r n a b l e ; an o u t e r l o n g i t u d i n a l l a y e r and an i n n e r c i r c u l a r l a y e r . The endometrium, s i t u a t e d d i r e c t l y b e n e ath the myometrium, i s o f s i m i l a r t h i c k n e s s and c o n s i s t s o f an u n o r g a n i z e d mass o f h e a v i l y n u c l e a t e d t i s s u e . A few e n d o m e t r i a l g l a n d s can be seen n e a r t h e i n n e r s u r f a c e and l i k e t he i n n e r s u r f a c e , a r e l i n e d w i t h a d i s t i n c t s i n g l e l a y e r o f c u b o i d a l e p i t h e l i u m about 10^ i n h e i g h t . The e p i t h e l i u m c o n t a i n s l i t t l e c y t o p l a s m and t h e d a r k s t a i n i n g n u c l e i a r e i r r e g u l a r i n shape. -26-Th e o v a r y o f t h e i n f a n t i l e f e m a l e i s q u i t e s i m p l e . I t i s o f t h e t y p i c a l r o d e n t t y p e as d e s c r i b e d by Mossman (I966) and shows a t h i c k c o r t e x h e a v i l y p o p u l a t e d w i t h naked ova f o r t h e f i r s t t h r e e t o f o u r months o f l i f e ( P l a t e IX A i ) . D e g e n e r a t i n g s e c o n d a r y f o l l i c l e s a r e f a i r l y common i n t h e m e d u l l a r y r e g i o n o f o l d e r i n f a n t i l e a n i m a l s ( P l a t e I X A i i ) , and e v e n t u a l l y , a t about e i g h t months th e i n f a n t i l e o v a r y appears v e r y s i m i l a r t o t h e a n o e s t r o u s a d u l t o v a r y , e x c e p t f o r a h e a v i e r c o r t i c a l p o p u l a t i o n o f naked ova ( P l a t e I X A l i i ) . The P r o e s t r o u s Female The p r o e s t r o u s p e r i o d was c o n s i d e r e d t o b e g i n w i t h t h e f i r s t s i g n s o f c o i l i n g o f t h e v a g i n a t h a t accompanied an i n c r e a s e i n s i z e o f a l l p a r t s o f t h e r e p r o d u c t i v e t r a c t s . D u r i n g t h i s p e r i o d t h e n i p p l e s o f t h e p r e v i o u s l y i n f a n t i l e and a n o e s t r o u s a n i m a l s become e n l a r g e d so t h a t i t i s d i f f i c u l t t o d i s t i n g u i s h j u v e n i l e and a d u l t a n i m a l s w i t h any degree o f c e r t a i n t y . Development f o l l o w s a v e r y s i m i l a r p a t t e r n whether o r n o t t h e a n i m a l s have b r e d b e f o r e . F o r t h i s r e a s o n a l l d e v e l o p i n g females were c l a s s i f i e d i n one group. A t t h e t i m e j u s t p r e c e d i n g e s t r u s , t h e n i p p l e s become c o n s p i c u o u s l y t h i c k e r . The v u l v a remains s m a l l . I n t e r n a l l y , t h e o v a r i e s t a k e on a r a t h e r g r a n u l a r appearance b u t r e m a i n h i d d e n w i t h i n t h e b u r s a . The u t e r i become t u r g i d and measure o v e r 30 mm l o n g and about 3 mi i n d i a m e t e r . The v a g i n a shows the g r e a t e s t d e g r e e o f change, becoming an e x t r e m e l y e l o n g a t e and h i g h l y c o l l e d organ o f up t o 7 mm i n d i a m e t e r d u r i n g p r o e s t r u s . M i c r o s c o p i c a l l y , t h e whole v a g i n a i n c r e a s e s i n s i z e t h r o u g h h y p e r p l a s i a o f t h e t i s s u e and i n c r e a s e d c e l l s i z e ( P l a t e V I I B) . The n u c l e i assume r e g u l a r .shapes and s t a i n l i g h t l y . The submucosa d e v e l o p s i n t o b u n d l e s of randomly o r i e n t e d smooth muscle and a l i t t l e c o l l a g e n i s p r e s e n t between the muscle b u n d l e s . The g r e a t e s t change i n the v a g i n a i s seen i n t h e l a m i n a p r o p r i a where the whole l a y e r becomes e x t r e m e l y c o l l a g e n ! Only a few w i d e l y spaced n u c l e i a r e p r e s e n t i n t h e c o l l a g e n . As t h e l a m i n a p r o p r i a I n c r e a s e s i n t h i c k n e s s , t h e g e r m i n a t i v u m becomes a c o n s p i c u o u s l a y e r w h i c h i s h e a v i l y n u c l e a t e d o n l y I n t h e b a s a l r e g i o n s . S l i g h t i n d i c a t i o n s o f s l o u g h i n g o f the s u r f a c e l a y e r s can be seen b u t i s minor when compared w i t h t h a t seen i n e s t r u s . As w e l l as b e i n g h i g h l y c o i l e d the v a g i n a shows a v e r y i r r e g u l a r i n n e r s u r f a c e . As a r e s u l t , a c r o s s s e c t i o n a l view o f the t r a c t shows l a y e r s o f t i s s u e t o be much t h i c k e r t h a n they r e a l l y a r e . P r o e s t r u s changes i n t h e u t e r u s a r e n o t as marked as t h o s e seen i n t h e v a g i n a . There i s a g e n e r a l I n c r e a s e i n myometrium t h i c k n e s s , t h e c e l l s become d i s t e n d e d w i t h c y t o p l a s m and the two muscle l a y e r s become c o n s p i c u o u s . The endometrium i n c r e a s e s t o about 400/, i n t h i c k n e s s and becomes Invaded i t f i t h many g l a n d s w h i c h f r e q u e n t l y show open l u m i n a o n l y d u r i n g l a t e p r o e s t r u s . I n c r e a s e d c y t o p l a s m i s e v i d e n t i n a l l c e l l s . -28-A l t h o u g h i t m a i n t a i n s i t s p s e u d o s t r a t i f i e d appearance, t h e s e c r e t o r y e p i t h e l i u m l i n i n g t h e lumen o f t h e u t e r u s a c q u i r e s c y t o p l a s m . E p i t h e l i a l c e l l n u c l e i s t a i n l i g h t l y and assume r e g u l a r shapes, u s u a l l y s l i g h t l y e l o n g a t e . The o v a r i e s d u r i n g p r o e s t r u s show few naked ova i n the c o r t i c a l r e g i o n even i n t h o s e females t h a t a r e young o f the y e a r . The m e d u l l a r y r e g i o n however, has many sec o n d a r y and t e r t i a r y f o l l i c l e s , a l t h o u g h many o f t h e s e a r e i n v a r i o u s s t a g e s o f d e g e n e r a t i o n . The a c t i v e f o l l i c l e s r emain s m a l l and few l e s s t h a n 3 0 0 ^ i n d i a m e t e r show a n t r a . The l a r g e s t o f 2 9 d e v e l o p i n g f o l l i c l e s o v e r 300^ I n d i a m e t e r measured i n f o u r p r o e s t r o u s a n i m a l s was 6 0 0 * , and t h e mean s i z e was . The l a r g e s t o f 2 3 a t r e t i c f o l l i c l e s o v e r 3 0 0 * , found i n t h e same f o u r a n i m a l s was w i t h a mean o f 3 8 3 ^ - . The E s t r o u s Female E x t e r n a l l y t h e e s t r o u s female has n i p p l e s t h a t a r e e l o n g a t e and pigmented b u t n o t n o t i c a b l y s w o l l e n and t h e v u l v a i s a t h i c k p i n k p r o j e c t i o n about 5 mm i n h e i g h t . I n t e r n a l l y , t h e v a g i n a remains h i g h l y c o i l e d and b o t h t h e v a g i n a and u t e r i a r e t u r g i d . B o t h o v a r i e s become i r r e g u l a r I n shape t h r o u g h the development o f G r a a f i a n f o l l i c l e s and, a f t e r o v u l a t i o n , o f c o r p o r a l u t e a . R i p e f o l l i c l e s appear as v i s c o u s b u b b l e s on the o v a r i a n s u r f a c e , w h i l e new c o r p o r a l u t e a appear as -29-d i s t l n c t opsque b u l g e s about 1 mm i n d i a m e t e r . Blood-c l o t s sometimes show as brown s p o t s i n r e c e n t l y formed c o r p o r a . The m i c r o s c o p i c f e a t u r e s o f ' e s t r u s a r e f a i r l y d i s t i n c t , e s p e c i a l l y i n t h e v a g i n a ( P l a t e V I I C ) . The v a g i n a l submucosa remains f u l l y formed b u t t h e h i g h l y c o l l a g e n i c l a m i n a p r o p r i a shows a l o o s e n i n g o f t h e c o l l a g e n f i b r e s t h a t may be t a k e n as t h e f i r s t s i g n o f c o l l a g e n d e g e n e r a t i o n . As t h i s d e g e n e r a t i o n proceeds t h e c o l l a g e n t i s s u e n u c l e i become v e r y g r a n u l a r . The g e r m l n a t l v u m , w h i c h i s v e r y t h i c k d u r i n g l a t e p r o e s t r u s , produces t h e s l o u g h i n g corneum t h a t a l m o s t c o m p l e t e l y o c c l u d e s t h e v a g i n a l lumen. U n l i k e t h e l a m i n a p r o p r i a , t h e g e r m l n a t l v u m and corneum a r e b a s o p h i l i c . The Immediate p o s t o v u l a t o r y v a g i n a becomes permeated w i t h l e u c o c y t e s . D e f i n i t e u t e r i n e changes a r e a l s o e v i d e n t d u r i n g e s t r u s . P r i o r t o o v u l a t i o n t h e myometrium shows an absence o f c o n s p i c u o u s b l o o d v e s s e l s and t h e m i d d l e c i r c u l a r nmscle l a y e r d e v e l o p s s t r a n d s o f c o l l a g e n . E n d o m e t r i a l g l a n d s p o s s e s s open l u m i n a . The s e c r e t o r y e p i t h e l i u m c o n s i s t s o f a s i n g l e l a y e r o f t a l l columnar c e l l s t h a t p o s s e s s e l o n g a t e b a s a l n u c l e i and a t h i c k a c t i v e a p i c a l c y t o p l a s m . S e c r e t i o n d r o p l e t s a r e common on the e p i t h e l i a l s u r f a c e . Those s e c r e t o r y c e l l s fo\\ind w i t h i n the e n d o m e t r i a l g l a n d s a r e more c u b o i d a l t h a n columnar, bu t they t o o a r e a c t i v e . The -30-4 internal surface of the uterus is rough and highly convoluted at this time (Plate VIII B ) . There is considerable variation in the ovaries. Some animals show many developing f o l l i c l e s and others shox-7 very few. One juvenile female taken in May 1966 was in f u l l estrus by a l l other c r i t e r i a but showed no developing f o l l i c l e s in the ovaries. Normally the f o l l i c l e s that develop large antra assume cortical positions while smaller ones continue to develop and degenerate in the medulla. Atretic f o l l i c l e s in four estrous females varied from zero to eleven in number, averaged 39^- in diameter and had a maximum size of 64o# . Developing f o l l i c l e s over 300/, in diameter in the same four estrous females varied from zero to five in number, averaged 55^ i n diameter and had a maximum size of 880/,. . As noted by Mossman (I966) the ripe f o l l i c l e s possesses a distinct thecal glandular layer between the granulosa and I n t e r s t i t i a l c e l l s . Following ovulation, the corpora lutea develop rapidly. The average diameter of 21 corpora lutea found in four females during the preimplantatlon stage was 1036^ . Early corpora lutea possess large central blood clots which are usually gone by the time the embryos are discernable. A few females had corpora lutea without blood clots and did not have v i s i b l e embryos. The corpora lutea showed no signs of degeneration and i t is unknown whether or not they would have produced young (Plate IX B ) . One case was found where small blood clots were present in -31-c o n j u n c t i o n w i t h 7 mm embryos. The l u t e a l c e l l s d u r i n g t h e p o s t o v u l a t i o n p e r i o d show l a r g e n u c l e i w i t h many n u c l e o l i . T h e i r c y t o p l a s m appears s l i g h t l y g r a n u l a r , t h e c e l l s a r e f a i r l y r e g u l a r i n shape, and c e l l b o u n d a r i e s a r e i n d i s t i n c t . The P r e g n a n t Female D u r i n g pregnancy t h e n i p p l e s r e m a i n c o n s p i c u o u s b u t n o t p a r t i c u l a r l y d i s t e n d e d , w h i l e the v u l v a l o s e s i t s c o n s p i c u o u s s w o l l e n appearance. D u r i n g l a t e r pregnancy, when t h e abdomen becomes n o t i c e a b l y s w o l l e n , the v a g i n a l o s e s i t s h i g h l y c o i l e d appearance and becomes a s h o r t f l a c c i d tube about 7 mm wide. The o v a r i e s d u r i n g pregnancy may be as l a r g e as 6 by 4 mm due t o the presence o f c o r p o r a l u t e a . C o r p o r a l u t e a r e m a i n c o n s p i c u o u s b u t become d a r k e r as pregnancy p r o g r e s s e s . I n l a t e pregnancy t h e mammary g l a n d s can be seen as two t h i n w h i t e s h e e t s r u n n i n g t h e f u l l l e n g t h o f the abdomen. The m i c r o s c o p i c p i c t u r e of t h e v a g i n a d u r i n g pregnancy shows a g e n e r a l d e c r e a s e i n t i s s u e l a y e r s . The m u s c u l a r submucosa remains i n t a c t b u t r a t h e r t h i n b e n e a th the a d v e n t i t i a . G r e a t e r changes a r e shown by the r e m a i n i n g t i s s u e s . The l a m i n a p r o p r i a has a f a i r l y r a p i d d e g e n e r a t i o n o f c o l l s g e n , u n t i l o n l y a v e r y t h i n l a y e r o f l o o s e l y a s s o c i a t e d s t r a n d s remains p o s t par turn. Of the germinativu.m and corneum, o n l y t h e b a s a l g e r m l n a t l v u m remains and - 3 2 -t h e r e seems t o be no s l o u g h i n g o f c e l l s . L e u c o c y t e s r e m a i n I n t h e v a g i n a l lumen f o r some time and t h e lumen i t s e l f e n l a r g e s and e v e n t u a l l y d e v e l o p s smooth w a l l s by t h e time o f p a r t u r i t i o n ( P l a t e V I I D). S e c t i o n s o f the u t e r i , t a k e n where p o s s i b l e beyond or between the embryonic s w e l l i n g s , show some changes s i m i l a r t o t h o s e found i n t h e v a g i n a . The o u t e r l o n g i t u d i n a l l a y e r o f the myometrium remains i n t a c t b u t t h e more c o l l a g e n i c m i d d l e l a y e r appears t o d e g e n e r a t e , d e v e l o p b l o o d v e s s e l s and become f a i r l y l o o s e . The endometrium remains r e l a t i v e l y unchanged. The o v a r y d u r i n g pregnancy shows a c o n s t a n t g e n e r a t i o n and d e g e n e r a t i o n o f f o l l i c l e s , a l t h o u g h much o f i t s volume i s t a k e n up by c o r p o r a l u t e a . S e v e r a l a c t i v e and d e g e n e r a t i n g t e r t i a r y f o l l i c l e s a r e p r e s e n t a t a l l t i m e s . I n f i v e females c a r r y i n g embryos l e s s t h a n 10 mm i n l e n g t h , t h e l a r g e s t d e v e l o p i n g f o l l i c l e measured 600/, , w h i l e the average d i a m e t e r o f 58 f o l l i c l e s was 4 1 4 ^ .. A t r e t i c f o l l i c l e s i n t h e same f i v e f e m ales averaged 38.5^ i n d i a m e t e r and t h e maximum was 600/, . Four females c a r r y i n g embryos g r e a t e r t h a n 30 mm had 66 d e v e l o p i n g f o l l i c l e s a v e r a g i n g 501/, i n d i a m e t e r . The maximum s i z e was 720/, . T h i r t y - o n e a t r e t i c f o l l i c l e s averaged kZ6ju , and t h e l a r g e s t b e i n g 680/< . C o r p o r a l u t e a r e t a i n an average d i a m e t e r o f about 900/, t h r o u g h o u t pregnancy a l t h o u g h t h e r e does seem t o be a s l i g h t d e c r e a s e . The average d i a m e t e r i n -33= a n i m a l s c a r r y i n g embryos l e s s t h a n 10 mm l o n g was 9^8^ . The average f o r a n i m a l s i n the embryos l a r g e r t h a n 30 mra was 888# . The s t r u c t u r e o f the l u t e a l t i s s u e does n o t change, e x c e p t f o r t h e l o s s o f t h e b l o o d c l o t e a r l y i n pregnancy ( P l a t e X A l and X A i l ) . From t h e n u n t i l p a r t u r i t i o n a t about t h e 40 mm embryo s t a g e , t h e r e a r e no g r e a t l u t e a l changes. N u c l e i w i t h i n t h e l u t e a l c e l l s a r e d i s t i n c t l y g r a n u l a r and round o r o v a l I n shape. The c e l l s show i n d i s t i n c t b o u n d a r i e s , a l t h o u g h t h e c y t o p l a s m tends t o pack around, the n u c l e i , g i v i n g a r e l a t i v e l y d i s t i n c t shape t o t h e c e l l . L a c t a t i n g Females F o l l o w i n g p a r t u r i t i o n t h e r e a r e two p o s s i b l e p a t t e r n s t h a t may be f o l l o w e d . The f i r s t i s a d e g e n e r a t i o n of a l l organs and r e g r e s s i o n t o the a n o e s t r o u s s t a g e . T h i s o c c u r r e d d u r i n g 19&7, b o t h on Vancouver I s l a n d and i n t h e I n t e r i o r . The second p a t t e r n shows p o s t partum e s t r u s o c c u r r i n g s h o r t l y a f t e r p a r t u i t l o n , as was found on Vancouver I s l a n d \" d u r i n g 1966. When no p o s t partum e s t r u s o c c u r s a f a i r l y s i m p l e p a t t e r n can be seen. The n i p p l e s become v e r y d i s t e n d e d and the f u r around them i s worn away, and t h e v u l v a remains f l a c c i d f o r some t i m e . The mammary glan d s themselves can be seen as two w h i t e pads r u n n i n g the f u l l l e n g t h o f t h e abdomen. Towards t h e end o f l a c t a - t i o n - 3 4 -t h e y become f a i r l y compact and d a r k I n c o l o r . The v a g i n a and u t e r i a r e s w o l l e n f o r a s h o r t p e r i o d o n l y and p l a c e n t a l s c a r s a r e c o n s p i c u o u s f o r some time a f t e r l a c t a t i o n . The o v a r i e s do n o t s h r i n k a p p r e c i a b l y d u r i n g t h i s t i m e . M i c r o s c o p i c a l l y t h e r e i s a g e n e r a l d e g e n e r a t i o n o f t h e v a g i n a and u t e r u s u n t i l t h e y assume t h e a n o e s t r o u s form. The organs do not appear t o r e g r e s s f u l l y a f t e r t h e p e r i o d o f l a c t a t i o n . The most n o t i c e a b l e change i s t h e d e g e n e r a t i o n o f t h e c o l l a g e n t i s s u e . The o v a r i e s d u r i n g l a c t a t i o n c o n t i n u e t o show some d e v e l o p i n g and r e g r e s s i n g f o l l i c l e s . The c o r p o r a l u t e a , w h i c h show no a p p r e c i a b l e change I n s i z e s i n c e e a r l y pregnancy, do show some s t r u c t u r a l d i f f e r e n c e s . The i n d i v i d u a l l u t e a l c e l l s appear t o l o s e t h e f i n e v a c u o l e s and t h e c y t o p l a s m c o a l e s c e s around t h e n u c l e i , g i v i n g them a more d i s t i n c t form. Some l u t e a l c e l l s t e n d t o s e p a r a t e from each o t h e r . a n d a l i t t l e f a t t y d e g e n e r a t i o n becomes e v i d e n t d u r i n g l a t e l a c t a t i o n ( P l a t e X A l i i and X B ) . The p o s t partura e s t r o u s female cannot be d i s t i n g u i s h e d from t h e l a c t a t i n g female on an e x t e r n a l b a s i s . A s w o l l e n v u l v a was n e v e r seen on a p o s t partum f e m a l e , a l t h o u g h t h e sample was t o o s m a l l t o g i v e c o n c l u s i v e e v i d e n c e . There a r e a l s o few g r o s s s i g n s o f p o s t partum e s t r o u s . Seven p o s t partum females t h a t had n o t y e t o v u l a t e d d i d not show any s i g n o f i n c r e a s e d s i z e o r -35-c o i l i n g o f t h e v a g i n a , L i k e w i s e , none o f t h e t e n p o s t partum females t h a t had o v u l a t e d showed any s i g n o f v a g i n a l I n c r e a s e . M i c r o s c o p i c a l l y t h e r e i s no c l e a r p i c t u r e o f the p o s t partum e s t r o u s s i n c e t h e r e were n o t enough a n i m a l s t a k e n t o make an a c c u r a t e h i s t o l o g i c a l d e t e r m i n a t i o n . Pour o f t h e seven p o s t partum females t h a t had n o t o v u l a t e d showed l a r g e f o l l i c l e s b u t i t i s u n c e r t a i n whether o r n o t they would have o v u l a t e d . U t e r i and v a g i n a e o f t h e s e f o u r a n i m a l s were i d e n t i c a l t o t h o s e i n a normal l a c t a t i n g f e m a l e . The u t e r i and v a g i n a e were s t u d i e d i n t h r e e females t h a t had o v u l a t e d b u t d i d n o t p o s s e s s d i s c e r n a b l e embryos. I n one, b o t h t h e u t e r u s and v a g i n a were s m a l l and h i s t o l o g i c a l l y d e g e n e r a t e . The o v a r i e s , however, c o n t a i n e d c o r p o r a l u t e a w i t h l a r g e b l o o d c l o t s , i n d i c a t i n g t h a t t h e a n i m a l had r e c e n t l y o v u l a t e d . I n t h e o t h e r two females t h e r e were no b l o o d c l o t s i n the c o r p o r a l u t e a , so th e y had not j u s t o v u l a t e d . The v a g i n a e were d e g e n e r a t e h i s t o l o g i c a l l y and o n l y about 3 mm i n d i a m e t e r . The u t e r i , however, were t u r g i d and I d e n t i c a l h i s t o l o g i c a l l y t o normal e s t r o u s a n i m a l s . A l t h o u g h t h e e v i d e n c e i s s c a n t y , i t appears t h a t when p o s t partum e s t r u s o c c u r s soon a f t e r p a r t u r i t i o n t h e v a g i n a does n o t have t h e c a p a c i t y t o d e v e l o p t o t h e i n i t i a l e s t r o u s c o n d i t i o n . That i s , o v u l a t i o n o c c u r s w h i l e t h e v a g i n a e and u t e r i a r e s t i l l r e c u p e r a t i n g from t h e e f f e c t s o f pregnancy and p a r t u r i t i o n . When p o s t partum e s t r u s o c c u r s i t i s p o s s i b l e t o d i f f e r e n t i a t e between t h e two s e t s o f c o r p o r a l u t e a . 36 The o l d c o r p o r a l u t e a a r e s m a l l e r and more m e d u l l a r y i n p o s i t i o n t h a n t h e new s e t . F u r t h e r m o r e , t h e l u t e a l c e l l s t r u c t u r e o f each s e t i s somewhat d i s t i n c t , t h e o l d s e t a p p e a r i n g as c o r p o r a l u t e a o f l a c t a t i o n and t h e new s e t a p p e a r i n g as c o r p o r a l u t e a o f pregnancy. Even a f t e r t h e b i r t h o f the second l i t t e r t h e s t a g e o f d e g e n e r a t i o n i s more advanced i n t h e o l d e r c o r p o r a . Because o f t h i s t h e number o f eggs o v u l a t e d a t each e s t r u s can be d e t e r m i n e d even a f t e r t h e b r e e d i n g season by c o u n t i n g c o r p o r a a l b l e a n t i a . The A n o e s t r o u s Female The a n o e s t r o u s female shows s e v e r a l f e a t u r e s i n i t s g r o s s anatomy t h a t s e p a r a t e s i t from the i n f a n t i l e . A l t h o u g h t h e n i p p l e s can o n l y be seen upon c l o s e e x a m i n a t i o n , t h e y r e m a i n as d a r k t i p p e d p r o j e c t i o n s about 1 mm i n l e n g t h and s e r v e as a f e a t u r e t h a t d i s t i n g u i s h e s a d u l t s from young t h r o u g h o u t t h e n o n b r e e d i n g w i n t e r season. The o v a r i e s , u t e r i and v a g i n a e a r e s l i g h t l y l a r g e r t h a n t h o s e o f the i n f a n t i l e f e m a l e s , and a r e u s u a l l y seen as f a i r l y c o n s p i c u o u s abdominal organs. The u t e r i measure about 30 by 2 mm i n l e n g t h and w i d t h , t h e v a g i n a I s g e n e r a l l y g r e a t e r t h a n 2 mm i n d i a m e t e r , and t h e o v a r i e s a r e about 4 by 3 mm i n l e n g t h and w i d t h . D u r i n g t h e e a r l y a n o e s t r o u s p e r i o d c o r p o r a a l b i c a n t i a may be seen as l i g h t c o l o u r e d b u l g e s on the smooth s u r f a c e o f t h e o v a r y . Towards l a t e a n o e s t u s , t h e c o r p o r a a l b i c a n t i a cannot be seen e x t e r n a l l y and the -37 o v a r i e s a r e e s s e n t i a l l y i n f a n t i l e I n appearance. M i c r o s c o p i c a l l y , t h e a n o e s t r o u s v a g i n a I s v e r y s i m i l a r t o t h a t found i n t h e I n f a n t i l e f e m a l e . The o n l y a p p a r e n t d i f f e r e n c e i s i n t h e more d e f i n i t e l a y e r i n g o f t h e m u s c u l a r submucosa and t h e p r e s e n c e o f c o n s p i c u o u s s c l e r o t i c b l o o d v e s s e l s i n t h e l a m i n a p r o p r i a ( P l a t e . V I I E ) . The u t e r i a r e a l s o s i m i l a r t o t h o s e seen I n t h e I n f a n t i l e s t a g e , a l t h o u g h t h e t i s s u e l a y e r s r e m a i n t h i c k e r . The myometrium remains r o u g h l y 150* i n t h i c k n e s s w h i l e t h e endometrium i s m a i n t a i n e d a t about 130* . L i t t l e o r g a n i z a t i o n i s shown by t h e myometrium and s c l e r o t i c b l o o d v e s s e l s r e m a i n c o n s p i c u o u s f o r the d u r a t i o n o f t h e a n o e s t r o u s s t a g e ( P l a t e V I I I D i ) . E n d o m e t r i a l g l a n d s a r e s c a r c e and the s u r f a c e e p i t h e l i u m tends t o r e m a i n p s e u d o s t r a t i f i e d r a t h e r t h a n as a s i n g l e c e l l l a y e r . The e p i t h e l i a l c e l l s c o n t a i n l i t t l e c y t o p l a s m and t h e i r n u c l e i s t a i n d a r k l y . A n o e s t r o u s o v a r i e s show s e v e r a l c h a r a c t e r i s t i c s m i c r o s c o p i c a l l y w h i c h s e r v e t o d i s t i n g u i s h them from t h e i n f a n t i l e organs. C o r p o r a a l b l c a n t l a a r e m a i n t a i n e d f o r many weeks a f t e r the end o f l a c t a t i o n and i n some ca s e s c a n be seen even I n t h e p r o e s t r o u s s t a g e ( P l a t e I X C ) . Many s i g n s o f d e g e n e r a t i o n , such as s m a l l s i z e , many f i b r o b l a s t s , l a r g e v a c u o l e s between c e l l s , i r r e g u l a r l y shaped n u c l e i and p o o r l y , d e f i n e d l u t e a l c e l l s s e r v e t o d i s t i n g u i s h t h e s e o l d c o r p o r a a l b i c a n t i a . The c o r t i c a l r e g i o n s p o s s e s s r e l a t i v e l y few naked ova and p r i m a r y f o l l i c l e s . The m e d u l l a r y r e g i o n shows t h e remains o f - 3 8 -many r e g r e s s e d f o l l i c l e s and l i t t l e s i g n o f antrum f o r m a t i o n i s seen d u r i n g most o f the a n o e s t r o u s p e r i o d . S m a l l a n t r a do become r e l a t i v e l y common towards t h e end o f t h e a n o e s t r o u s p e r i o d . Summer a n o e s t r o u s f e m a l e s , w h i c h have u s u a l l y n o t b r e d p r e v i o u s l y , a r e q u i t e s i m i l a r t o t h e w i n t e r a n o e s t r o u s a d u l t s i n e x t e r n a l appearance. The v u l v a remains s m a l l and the n i p p l e s do become s l i g h t l y e n l a r g e d and appear as s m a l l w h i t e p r o j e c t i o n s about one mm l o n g . The gonads r e m a i n s m a l l and a r e o c c a s i o n a l l y found t o be as s m a l l as i n i n f a n t i l e f e m a l e s . There i s no c o i l i n g o f t h e v a g i n a . M i c r o s c o p i c a l l y , however, t h e summer a n o e s t r o u s females do appear d i f f e r e n t t h a n the w i n t e r a n o e s t r o u s a n i m a l s . They a r e h i s t o l o g i c a l l y s i m i l a r t o t h e e a r l y p r o e s t r o u s a n i m a l s b u t show no s i g n o f r e a c h i n g e s t r u s . F o r t h i s r e a s o n t h e y a r e c l a s s e d as a n o e s t r o u s a l t h o u g h w i t h the r e a l i z a t i o n t h a t some a c t i v i t y o c c u r s i n t h e gonads. The B r e e d i n g Season. The b r e e d i n g season o f each y e a r was d e t e r m i n e d by m i c r o s c o p i c e x a m i n a t i o n o f a l l r e p r o d u c t i v e o r g a n s . As emphasized by Layne (195^), the a c c e s s o r y organs o f t h e male r e d s q u i r r e l a r e u s e f u l c r i t e r i a by w h i c h t o judge t h e s e x u a l c o n d i t i o n . The p o i n t a t w h i c h t h e male becomes f u n c t i o n a l , o r l o s e s t h e c a p a c i t y t o b r e e d , i s d i f f i c u l t t o a s s e s s and t h e c o n d i t i o n o f t h e a c c e s s o r y organs can a i d i n t h i s d e t e r m i n a t i o n . I n o r d e r t o be s u r e - 3 9 -that only males that v/ere t r u l y functional were c l a s s i f i e d as such, males which showed only one functional accessory organ v/ere considered nonfunctional, even i f epidldymal sperm was present. The seasonal reproductive changes found i n 1966 on Vancouver Island are presented i n Figure 2A and 3B. The males came into condition i n March and remained so u n t i l the beginning of September, although there was a steady decline i n organ si z e a f t e r May. The sharp drop i n seminal v e s i c l e length i n June was not due to a drop i n function since microscopic examination showed them to be f u l l y f unctional. The drop probably resulted from the release of the contents of the gland since the females v/ere i n estrus at this time. No second peak i n gland size occurred v/hen the females came into estrus again i n August. A s l i g h t increase appeared i n the testes length but thi s was.likely' due to the small sample siz e for that month. The females in 1966 showed no sign of coming Into reproductive condition u n t i l A p r i l and estrus was not found u n t i l May, at lea s t a month a f t e r the males became functional. The females again came into estrus a f t e r b i r t h of the f i r s t l i t t e r . There was a gap during l a t e June and July between the c o l l e c t i n g of the l a s t pregnant female carrying the f i r s t l i t t e r and the c o l l e c t i n g of the f i r s t v i s i b l y pregnant female carrying the second l i t t e r . Post partum estrus did occur during l a c t a t i o n but probably not immediately following p a r t u r i t i o n . FIGURE 2 -~ S e a s o n a l changes i n t h e mean l e n g t h s o f male r e p r o d u c t i v e o r g a n s , A„ The I966 b r e e d i n g season on Vancouver I s l a n d , B, The I967 b r e e d i n g s e a s o n on . Vancouver I s l a n d and I n t h e i n t e r i o r o f B r i t i s h C o l u m b i a , -40-FIGURE 3 - The d u r a t i o n o f v a r i o u s r e p r o d u c t i v e s t a g e s o f males and f e m a l e s , p l o t t e d as t h e p e r i o d between t h e c o l l e c t i n g o f t h e f i r s t and l a s t a n i m a l i n each p a r t i c u l a r s t a g e , A c The 1967 b r e e d i n g s e a s o n on Vancouver I s l a n d and i n t h e i n t e r i o r o f B r i t i s h C o l u m b i a . B. The I966 b r e e d i n g s eason on Vancouver I s l a n d . - 4 1 -Developing Functional Proestrus Estrus Pregnant Lactatlng M A L E F E M A L E < A. J _ J L J L _ ! D J F M A M J J A S O Developing Functional Proestrus Estrus Pregnant Post Partum Estrus & Pregnant Lactating MALE F E M A L E w/JM////////m l I I L J I L D J F M A M J J A S O The c y c l e found i n 196? i s shown i n Figure 2B and 3A. The small sample taken from Vancouver I s l a n d i n I967 showed an i d e n t i c a l p a t t e r n to those taken from the I n t e r i o r i n I967 and the data were combined f o r the purpose of seasonal comparisons. One male showed e a r l y signs of development In l a t e December and a l l were i n f u l l breeding c o n d i t i o n by the end of January. They remained i n breeding c o n d i t i o n only u n t i l the end of March. The p a t t e r n was the same as found In 1966 i n that there was a peak i n organ s i z e , p a r t i c u l a r l y the seminal v e s i c l e s , t h i s time when the females were coming i n t o e s t r u s . The peak was not as high as that In I966 but c o l l e c t i n g was done only once a month and a higher peak may have been missed by a few weeks. There was a drop i n male organ s i z e s i n February and March which c o i n c i d e d w i t h estrus i n the female. The drop i n organ s i z e s f o l l o w i n g the breeding p e r i o d was not as pronounced as i n 1 9 6 6 . This i s p o s s i b l y a r e s u l t of the lower p r o p o r t i o n of females breeding t h a t year. The females d u r i n g 1967 came i n t o breeding c o n d i t i o n at the end of January along with'the males. During l a c t a t i o n i n A p r i l and May there was no post partum e s t r u s . I f there had been one i t would not have been s u c c e s s f u l s i n c e the males were no longer capable of breeding. F e c u n d i t y The c o r p o r a l u t e a proved u s e f u l i n d e t e r m i n i n g th e o v u l a t i o n r a t e s s i n c e they a r e l a r g e , e a s i l y seen and a r e m a i n t a i n e d f o r months a f t e r t h e b r e e d i n g season. Even w i t h a p o s t partum e s t r u s , the f i r s t s e t o f c o r p o r a l u t e a can be d i s t i n g u i s h e d from the second by t h e i r s m a l l e r s i z e , more m e d u l l a r y p o s i t i o n and d i s t i n c t l u t e a l c e l l morphology. C o r p o r a l u t e a counts g i v e a good i n d i c a t i o n o f o v u l a t i o n r a t e o n l y i f i t can be assumed t h a t \"each corpus luteum r e p r e s e n t s the o v u l a t i o n s i t e o f one egg. Two females were c o l l e c t e d w h i c h had more I m p l a n t a t i o n s i t e s t h a n c o r p o r a l u t e a . I n one case the i m p l a n t a t i o n s i t e s v/ere n o t e d from p l a c e n t a l s c a r s a l o n e and t h e r e may have been an e r r o r i n c o u n t i n g . The o t h e r f e m a l e showed f i v e c o r p o r a l u t e a i n c o n j u n c t i o n w i t h s i x embryos. T h i s d i s c r e p a n c y may have been caused by t w i n n i n g o f t h e ova or from a p o l y o v u l a r f o l l i c l e . No embryos were seen t h a t p o s s e s s e d a common c h o r i o n so th e d i f f e r e n c e was p r o b a b l y t h e r e s u l t o f p o l y o v u l a t i o n . No f o l l i c l e s were seen t h a t c o n t a i n e d more t h a n one ovum. W i t h t h e e x c e p t i o n o f t h e s e two a n i m a l s , t h e c o r p o r a l u t e a counts were t a k e n t o be i n d i c a t i v e o f the o v u l a t i o n r a t e . C o r p o r a l u t e a \" c o u n t s were t a b u l a t e d by age, a r e a , s e a s o n , and y e a r . The comparisons a r e p r e s e n t e d i n T a b l e 1'. On Vancouver I s l a n d i n 19&7» t n e j u v e n i l e s had TABLE I - O v u l a t i o n r a t e s as i n d i c a t e d by c o r p o r a l u t e a c o u n t s o f a l l b r e e d i n g f e m a l e s . T a b u l a t e d by age, s e a s o n , y e a r and l o c a t i o n . Season . Age N Ran,a;e Mean May-June 1966 Van. I s . Ad. 16 4-7 5.18 Juv. 14 4-6 4.85 Tot. 30 4-7 5.03 1966 Van. I s . Ad. 4 6 6.00 J u v . 6 4-6 5.00 Tot. 10 4-6 5.40 P=.01 P=.2 J May-Aug. Ad. 20 4-7 5.35 1966 4.90 Van. I s . Ju v . 20 4-6 T o t . 40 4-7 5.12 Mar.-Apr. Ad. 19 3-5 3.68 1967 I n t e r i o r J u v . 15 2-6 3.46 T o t . 34 2-6 3.58 Mar.-Apr. Ad. 5 4 4.00 1967 Van. I s . Juv. 4 4 -5 4.25 T o t . 9 4 -5 4.11 P=.05 p=.5 P=.OOI P=.01 P=.3 P=.05 a h i g h e r o v u l a t i o n r a t e t h a n the a d u l t s b u t the d i f f e r e n c e was not s i g n i f i c a n t (P= . 0 3 ) . I n a l l o t h e r c a s e s , t h e a d u l t s showed a h i g h e r average o v u l a t i o n r a t e t h a n t h e j u v e n i l e s . 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 f o r the p o s t •partum b r e e d i n g on Vancouver I s l a n d I n I966 (P= .01) and f o r t h e 1966 b r e e d i n g season i n g e n e r a l (P= .05) b u t n o t f o r t h e f i r s t e s t r o u s p e r i o d (P= .2) o f t h a t season. I n the I n t e r i o r I n 1967, a d u l t s had an o v u l a t i o n r a t e o f 3.68 w h i c h was not s i g n i f i c a n t l y h i g h e r (P= .5) t h a n t h e j u v e n i l e r a t e o f 3.46. S i g n i f i c a n t d i f f e r e n c e s were found i n o v u l a t i o n r a t e s i n d i f f e r e n t a r e a s and y e a r s . On Vancouver I s l a n d i n 1966 the o v u l a t i o n r a t e o f 5.12 was h i g h e r (P= .01) t h a n t h e r a t e o f 4.11 found on the same a r e a i n 1967. The I n t e r i o r r e g i o n I n 1967 w i t h a r a t e o f 3.58 was l o w e r t h a n Vancouver I s l a n d I n 1966 (P= .001) and 1967 (P= . 0 5 ) . A l t h o u g h the o v u l a t i o n r a t e i s an i n d i c a t i o n o f t h e r e p r o d u c t i v e p o t e n t i a l o f an a n i m a l i t does n o t n e c e s s a r i l y show the a c t u a l p r o d u c t i v i t y . The number o f young b o r n can be reduced from t h e number o f eggs o v u l a t e d t h r o u g h p r e i m p l a n t a t i o n l o s s e s o r embryo r e s o r p t i o n . P r e i m p l a n t a t i o n l o s e s were d e t e r m i n e d from the d i f f e r e n c e between the number of o v u l a t i o n s i t e s and the number of v i s i b l e • i m p l a n t a t i o n s i t e s as i n d i c a t e d by embryonic s w e l l i n g s or p l a c e n t a l s c a r s . P r e i m p l a n t a t i o n l o s s e s a r e p r e s e n t e d i n T a b l e I I . The sample from TABLE I I - P r e i m p l a n t a t i o n l o s s e s as i n d i c a t e d by t h e d i f f e r e n c e between o v u l a t i o n s i t e s and empla.ntation s i t e s . T a b u l a t e d by age, s e a s o n , y e a r , and l o c a t i o n . -46-Season Age N Ov. S i t e s I m p l a n t S i t e s % Loss t . t e s t May-June Ad. 7 35 34 2.85 1966 Van. I s . Juv. 2 9 4 55.55 T o t . 9 44 38 13.63 J u l y - A u g . Ad. 2 12 11 8.33 1966 Van. I s . Juv. 1 5 5 0 T o t . 3 17 16 5.88 May-Aug. Ad. 9 47 45 1966 14 Van. I s . Juv , 3 - 9 T o t . 12 61 5^ 4 . 2 5 — , P = . 0 5 35.71 — J 11.49 — Mar.-Apr. 1967 I n t e r i o r Ad. Juv. 14 6 52 21 49 18 5.76 14.28 T o t , 20 73 67 8.21 Mar. -Apr.' 1967 Van. I s . Ad. Juv. 2 8 5 37.37 Tot. 2 8 5 37.37 T o t a l Ad. 25 107 99 7A7 J u v . 9 35 27 22.85 T o t . 34 142 126 11.26 p=.l 13.2 P=.4 - 4 7 -Vancouver I s l a n d i n 1967 w a s n o t l a r g e enough t o be u s e f u l . I n a l l c ases t h e j u v e n i l e s showed a h i g h e r p r e i m p l a n t a t i o n l o s s b u t t h e d i f f e r e n c e was n e v e r s i g n i f i c a n t . The o v e r a l l p r e i m p l a n t a t i o n l o s s on Vancouver I s l a n d i n 1966 was n o t s i g n i f i c a n t l y d i f f e r e n t from t h e I n t e r i o r l o s s e s I n 1967. The l o s s found f o r a l l a n i m a l s was .47 eggs p e r f e m a l e , o r an o v e r a l l l o s s o f 11.26$ o f eggs o v u l a t e d . . When p r e i m p l a n t a t i o n l o s s e s were t a k e n I n t o c o n s i d e r a t i o n , the a d u l t s and j u v e n i l e s showed no s i g n i f i c a n t d i f f e r e n c e i n t h e number o f embryos c a r r i e d . A d u l t s on Vancouver I s l a n d i n 1966 averaged 5.00 embryos p e r f e m a l e , which was n o t s i g n i f i c a n t l y d i f f e r e n t (P= .5) from the 3.75 embryos p e r female c a r r i e d by the j u v e n i l e s . A d u l t s I n the I n t e r i o r i n 1967 c a r r i e d 3.62 embryos p e r female and t h i s was n o t s i g n i f i c a n t l y d i f f e r e n t (P= .02) from t h e j u v e n i l e embryo r a t e o f 2.66 per pregnant female. When combined however, t h e 4 . 6 l embryos p e r pregnant f e m a l e on Vancouver I s l a n d i n I966 was s i g n i f i c a n t l y h i g h e r (P= .001) t h a n t h e 3.36 embryos p e r female t a k e n from the I n t e r i o r i n 1967. Embryo counts a r e p r e s e n t e d i n T a b l e I I I . Embryo r e s o r p t i o n s a r e r e c o r d e d i n T a b l e IV. None was found i n 13 females from Vancouver I s l a n d i n 1966. The I n t e r i o r s t u d y a r e a i n 1967, when 11 pregnant females were t a k e n , showed an o v e r a l l r e s o r p t i o n r a t e o f 18.91$ o f the embryos. Age d i f f e r e n c e s i n t h e r e s o r p t i o n l o s s T A B L E I I I - Embryo cou n t s as i n d i c a t e d by t h e number o f v i s i b l e embryos o r I m p l a n t a t i o n s i t e s , R e s o r b i n g embryos i n c l u d e d . T a b u l a t e d by age, s e a s o n , y e a r and l o c a t i o n - 4 8 -Season Age N Range Mean t . t e s t May-June 1966 Van. I s . Ad. Juv. 7 3 4 -5 1-6 4 .86 -3.33 -\"~p2..2 Tot. 10 1-6 4 . 4 0 J u l y - A u g . 1966 Van. I s . Ad. Juv . 2 1 5-6 5 5.50 -5.00 -P J . 3 I Tot. 3 5-6 5.33 May-Aug. 1966 Van. I s . Mar-Apr. 1967 I n t e r i o r Ad. 9 4-6 5.00 J u v . 4 1-6 3.75 Tot. 13 1-6 4.61 Ad. 8 3-4 3.62 Juv. 3 2-3 2.66 Tot. 11 2-4 3.36 P=.5 —1 P=.02 P=.001 I TABLE IV ~ P o s t i m p l a n t a t i o n l o s s e s as i n d i c a t e d by v i s i b l e r e s o r b i n g embryos. -49-Season Age N T o t a l V i a b l e % Loss Embryo Embryo May-June Ad. 7 34 34 0 1966 Van. Is.. Juv. 2 4 4 0 Tot. 9 38 38 0 J u l y - A u g . Ad. 2 11 11 0 1966 Van. I s . Juv. 1 5 5 0 Tot. 3 16 16 0 May-Aug. Ad. 9 45 45 0 1966 Van. I s . J u v . 3 9 9 0 T o t . 12 54 54 0 Mar-Apr. Ad. 8 29 22 24.13^ 1967 I n t e r i o r J u v. 3 8 8 0 Tot. 11 37 30 18.91/S - 5 0 -c o u l d n o t be d e t e r m i n e d because o f the s m a l l j u v e n i l e sample. Only t h r e e o f the e l e v e n pregnant females p o s s e s s e d r e s o r b i n g embryos. The r e s o r p t i o n s t h a t d i d o c c u r v a r i e d from one out o f t h r e e embryos t o a complete l i t t e r o f t h r e e . As w e l l as d i f f e r e n c e s i n the p r o d u c t i v i t y o f b r e e d i n g a n i m a l s t h e r e was c o n s i d e r a b l e v a r i a t i o n i n t h e f r e q u e n c y o f b r e e d i n g f e m a l e s . T a b l e V shows t h e p e r c e n t a g e a n i m a l s b r e e d i n g by age each y e a r . Almost 100$ o f t h e a d u l t females b r e d d u r i n g the t h r e e seasons. I n I966 a l l j u v e n i l e females b r e d on Vancouver I s l a n d , b u t i n I967, b o t h I n t h e . I n t e r i o r and on Vancouver I s l a n d , o n l y one t h i r d o f the j u v e n i l e s b r e d . T h i s i s a l a r g e l o s s t o t h e b r e e d i n g p o p u l a t i o n s i n c e j u v e n i l e s make up a l a r g e p r o p o r t i o n o f t h e s p r i n g p o p u l a t i o n . Of 160 a n i m a l s t a k e n betx^reen March and May o f b o t h y e a r s , 64$ were j u v e n i l e s . I n summary, t h e r e was no s i g n i f i c a n t d i f f e r e n c e between t h e s i z e o f t h e f i r s t l i t t e r and t h e second l i t t e r on Vancouver I s l a n d i n I 9 6 6 . Age d i f f e r e n c e s i n o v u l a t i o n r a t e s were e v i d e n t o n l y on Vancouver I s l a n d i n I966. P r e i m p l a n t a t i o n l o s s e s were c o n s t a n t a t about 11$ t h r o u g h o u t t h e s t u d y . The d i f f e r e n c e between p r e i m p l a n t a t i o n l o s s e s by age on Vancouver I s l a n d i n 1966 a r e p r o b a b l y n o t r e a l and s i m p l y a r e s u l t o f s m a l l sample s i z e . No age d i f f e r e n c e s were found I n embryo counts a l t h o u g h th e d i f f e r e n c e s on Vancouver I s l a n d i n 1966 p r o b a b l y would have been r e a l i f t h e sample s i z e had been l a r g e r . TABLE V - P e r c e n t females b r e e d i n g a f t e r t h e o n s e t o f t h e b r e e d i n g s e a s o n as i n d i c a t e d by p r o e s t r u s , pregnancy, o r l a c t a t i o n . T a b u l a t e d by age, y e a r , and l o c a t i o n . -51-Y e a r - A r e a Age N No. $ B r e e d i n g B r e e d i n g May-Aug. Ad. 21 21 100$ 1966 Van. I s . Juv. 18 18 100$ Apr.-Aug. Ad. 5 5 100$ 1967 Van. I s . Juv. 13 4 30.79$ F e b . - J u l y Ad. 23 22 95.59$ 1967 I n t e r i o r Juv. 59 21 35.59$ -52-Embryo r e s o r p t i o n s were p r e s e n t o n l y i n 19&7. The y e a r l y p r o d u c t i v i t y p i c t u r e i s d i f f e r e n t i n a l l o f t h e b r e e d i n g p o p u l a t i o n s s t u d i e d . On Vancouver I s l a n d I n I966 a l l females b r e d t w i c e , p r o d u c i n g about f i v e young each l i t t e r . On the same a r e a i n 1967 a l l a d u l t s b r e d b u t o n l y one t h i r d o f t h e j u v e n i l e s d i d so. Those females t h a t d i d br e e d produced o n l y one l i t t e r o f t h r e e o r f o u r young. I n t h e I n t e r i o r i n 19&7 a l m o s t a l l a d u l t s b r e d w h i l e o n l y one t h i r d o f t h e j u v e n i l e s d i d s o. There the b r e e d i n g females produced one l i t t e r o f two o r t h r e e young. R e p r o d u c t i o n i n R e l a t i o n t o R e l a t i v e P o p u l a t i o n D e n s i t i e s I n o r d e r t o e v a l u a t e t h e d i f f e r e n c e s i n p r o d u c t i v i t y o f young i n t h e t h r e e b r e e d i n g s e a s o n s , t h e r e p r o d u c t i v e s u c c e s s was compared w i t h the r e l a t i v e p o p u l a t i o n d e n s i t i e s . That t h e I n t e r i o r r e g i o n s u p p o r t e d a h i g h s q u i r r e l p o p u l a t i o n i n 19^7 was a p p a r e n t when c o l l e c t i n g began. One hundred and f o u r t e e n a n i m a l s were c o l l e c t e d i n 12 days d u r i n g March, A p r i l , and May. On Vancouver I s l a n d i n I966, 35 a n i m a l s were t a k e n i n 20 days w i t h i n t h e same p e r i o d , w h i l e t h e same a r e a i n 19&7 y i e l d e d 12 a n i m a l s i n t e n day s . Such a k i l l p e r day i s o n l y a r e l a t i v e p o p u l a t i o n count s i n c e i t took t i m e t o a u t o p s y an a n i m a l i m m e d i a t e l y a f t e r k i l l i n g , and t h i s reduced t h e h u n t i n g t i m e a p p r e c i a b l y when s e v e r a l a n i m a l s were t a k e n . I n a d d i t i o n , c o n i f e r s t a n d s were more open i n - 5 3 -t h e I n t e r i o r so t h a t t h e a n i m a l s c o u l d more r e a d i l y be seen, A f u r t h e r e s t i m a t e o f r e l a t i v e p o p u l a t i o n l e v e l was made by t a b u l a t i n g t h e number o f c a l l s heard p e r hour. Red s q u i r r e l s a r e e x t r e m e l y v o c a l and i t was t h e l o u d c h a t t e r i n g c a l l t h a t was r e c o r d e d . The c a l l s a r e n o t g i v e n a t a c o n s t a n t r a t e summer and w i n t e r ( S m i t h , I.965) and i t i s n o t u n l i k e l y t h a t the number o f c a l l s g i v e n by any one a n i m a l i n c r e a s e s c o n s i d e r a b l y w i t h i n c r e a s i n g p o p u l a t i o n d e n s i t y . F o r t h i s r e a s o n t h e number o f c a l l s h eard p e r u n i t t i m e i s n o t c o n s i d e r e d t o be an a b s o l u t e p o p u l a t i o n i n d e x . The Vancouver I s l a n d c o u n t s based on h o u r l y r e c o r d i n g s showed I . 7 8 c a l l s p e r hour w i t h i n h e a r i n g d i s t a n c e I n 1966 and 1.16 c a l l s p e r hour i n I 9 6 7 . The I n t e r i o r c o u n t s I n I967 were made on 15 minute p e r i o d s s i n c e t h e y were much too numerous t o keep p r o p e r check o f f o r an hour. These r e c o r d i n g s showed an average of 30.66 c a l l s p e r hour. From t h e s e d a t a i t can be seen t h a t the I n t e r i o r i n I967 had a h i g h p o p u l a t i o n and low r e p r o d u c t i o n , w h i l e t h e two-year low p o p u l a t i o n on Vancouver I s l a n d showed h i g h r e p r o d u c t i o n i n I966 b u t low r e p r o d u c t i o n i n I967 ( T a b l e V I ) . R e p r o d u c t i o n i n R e l a t i o n t o Foods U t i l i z e d Red s q u i r r e l s u t i l i z e a l m o s t e v e r y t y p e o f v e g e t a t i o n a v a i l a b l e t o them. S m i t h (I965) l i s t s 73 f o o d s p e c i e s o f s q u i r r e l s i n B r i t i s h C olumbia. I n t h i s s t u d y , stomach a n a l y s i s i n the f i e l d r e v e a l e d the TABLE V I - R e l a t i v e p o p u l a t i o n l e v e l s as i n d i c a t e d by t h e c a l l s r e c o r d e d p e r hour and t h e number k i l l e d p e r day. T a b u l a t e d by y e a r and l o c a t i o n . - 5 4 -P o p u l a t i o n Hours C a l l s / Days C o l l . / Pop. Reprod. ' Rec. Hour C o l l . Day , , L e v e l Vancouver I s l a n d 51 1966 .78 20 1.75 low h i g h Vancouver I s l a n d 1967 25 1.16 10 1.20 low low I n t e r i o r 1967 3.75* 30.66 12 9.50 h i g h low * Based on 15 min. r e c o r d i n g p e r i o d s . - 5 5 -o c c u r r e n c e o f v a r i o u s food types such as c o n i f e r s e e d , f u n g i , greens o r b e r r i e s and t h e monthly average f r e q u e n c i e s o f t h e s e g e n e r a l food types a r e p r e s e n t e d I n T a b l e V I I . F u r t h e r i d e n t i f i c a t i o n o f t h e f o o d s , p a r t i c u l a r l y t h e c o n i f e r seeds, was made by o b s e r v a t i o n s o f t h e a n i m a l s and t h e i r middens. Greens were e a t e n t h r o u g h o u t the y e a r i n s m a l l amounts, b e i n g p r e s e n t i n 14 . 5 $ o f a l l stomachs s t u d i e d . B e r r i e s were r e l a t i v e l y u n i m p o r t a n t t o the d i e t b u t were u t i l i z e d h e a v i l y when a v a i l a b l e i n August and September. K l n n i k i n n i k and s a l a l were t h e main b e r r i e s u t i l i z e d . The c h i e f components o f t h e y e a r l y d i e t were c o n i f e r seeds and f u n g i . F u n g i were found I n k7% o f a l l stomachs t h r o u g h o u t t h e y e a r v r h i l e c o n i f e r seeds were found i n 79%. C o n i f e r seeds were u t i l i z e d h e a v i l y i n a l l months w h i l e t h e f u n g i were n o t u t i l i z e d as h e a v i l y i n any month and o n l y s l i g h t l y i n J a n u a r y , F e b r u a r y and March. S t o r a g e caches on the a r e a s s t u d i e d c o n s i s t e d e x c l u s i v e l y o f c o n i f e r cones. A few f u n g i were found d r y i n g on l o g s and I n t r e e s b u t t h e s e were found i n t h e e a r l y summer as w e l l as i n the normal h a r v e s t time o f August and September. C o n i f e r seeds a r e t h e s t a p l e w i n t e r foods s t o r e d by r e d s q u i r r e l s . L odgepole p i n e and Douglas f i r were t h e cones most abundant i n t h e caches and I n t h e f e e d i n g middens, a l t h o u g h Engelmann s p r u c e and ponderosa p i n e were t a k e n I n s m a l l amounts when a v a i l a b l e . TABLE V I I - Frequency o f g e n e r a l food types I n s q u i r r e l stomachs. T a b u l a t e d by month as a p e r c e n t o f the t o t a l number o f stomachs examined. - 5 6 -Month No, Stomachs C o n t e n t s Greens B e r r i e s C o n i f e r Seeds Mushrooms J a n . 15 0.0 0.0 100.0 13.3 Feb. 36 8.3 0.0 100.0 19.4 Mar. 27 3.7 0.0 92.6 3.7 Apr. 19 5.3 0.0 89.5 21.0 May 38 15.8 0.0 84.2 65.8 June 54 18.5 0.0 62.9 68.5 J u l y 50 26.0 6.0 60.0 72.0 Aug. 27 14.8 40.7 85.2 59.2 S e p t . 20 20.0 80.0 65.0 15.0 Oct. 8 12.5 0.0 87.5 62.5 Nov. 5 20.0 0.0 80.0 80.0 Dec. 5 0.0 0.0 100.0 80.0 T o t a l 304 14.5 9.7 79.3 47.4 -57-D u r l n g t h e w i n t e r o f 1965-66 on Vancouver I s l a n d , t h e f i r cone crop'was r e l a t i v e l y poor and l o d g e p o l e p i n e was u t i l i z e d a l m o s t e x c l u s i v e l y . I n J u l y I966 t h e y f e d on t h e new c r o p o f g r e e n p i n e cones b u t d i d n o t s t a r t s t o r i n g cones a t t h a t t i m e . A v e r y good f i r cone c r o p o c c u r r e d i n I966 and by September s q u i r r e l s were s t o r i n g f i r cones a l m o s t e x c l u s i v e l y . Throughout t h e w i n t e r o f 1966-67 b o t h on Vancouver I s l a n d and i n t h e I n t e r i o r , s q u i r r e l s were t a k e n most f r e q u e n t l y i n a s s o c i a t i o n w i t h Douglas f i r t r e e s , and t h e i r middens c o n s i s t e d p r i m a r i l y o f Douglas f i r cone b r a c t s . I n 19&7 t h e f i r cone c r o p was poor and p i n e cones a g a i n became th e prime o b j e c t i v e o f t h e h a r v e s t i n g s q u i r r e l s . The r a t e o f r e p r o d u c t i o n i n the r e d s q u i r r e l was h i g h i n t h e b r e e d i n g s eason t h a t f o l l o w e d a w i n t e r d i e t o f p i n e cones, b u t i t was low b o t h on Vancouver I s l a n d and i n t h e I n t e r i o r i n 19^7 when f i r cones had been u t i l i z e d a l m o s t e x c l u s i v e l y d u r i n g the p r e v i o u s w i n t e r . - 5 8 -D I S C U S S I O N The R e p r o d u c t i v e C y c l e There i s n o t h i n g p a r t i c u l a r l y u n u s u a l about t h e changes i n the male r e p r o d u c t i v e organs o f t h e r e d s q u i r r e l t h r o u g h o u t t h e y e a r . The h i s t o l o g i c a l changes a r e e x t r e m e l y s i m i l a r t o t h o s e found i n t h e f o x s q u i r r e l by K i r k p a t r i c k (1955) and the a c c e s s o r y organs f o l l o w t h e t e s t i c u l a r c y c l e v e r y c l o s e l y . The f e m a l e s , however, show h i s t o l o g i c a l changes t h a t a r e q u i t e d i s t i n c t . The h i s t o l o g y o f t h e o v a r i e s has been d e s c r i b e d by Mossman ( i 9 6 0 ). C o r p o r a l u t e a a r e m a i n t a i n e d u n t i l l a t e l a c t a t i o n and t h e e v e n t u a l r e g r e s s i o n i s a s l o w p r o c e s s l a s t i n g s e v e r a l months. C o r p o r a l u t e a a r e a l s o m a i n t a i n e d d u r i n g l a c t a t i o n i n C i t e l l u s t r i d e c e m l l n e a t u s ( D r i p s , 1919K Marmota monax (Rasmussen, 1918), C i t e l l u s l a t e r a l i s (McKeever, I966) and C i t e l l u s b e l d l n g i (McKeever, 1966) b u t n o t i n S c i u r u s c a r o l l n e n s l s ( D e a n e s l y and P a r k e s , 1933). The v a g i n a l changes, however, a r e v e r y d i s t i n c t i v e o f t h e r e d s q u i r r e l . The l a r g e c o i l e d and h i g h l y c o l l a g e n i c v a g i n a t h a t d e v e l o p s a t e s t r u s i s n o t common among s c i u r i d s . A c o i l e d v a g i n a has been d e s c r i b e d d u r i n g e s t r u s i n C i t e l l u s b e l d i n g i (McKeever, 1966) b u t has not been r e p o r t e d i n any o t h e r s c i u r l d . The development o f t h e v a g i n a i n t o a c o l l e d s t r u c t u r e o c c u r s a t a t i m e when e s t r o g e n s a r e h i g h , w h i c h s u g g e s t s t h a t e s t r o g e n may be - 5 9 -a c a s u a l f a c t o r i n v o l v e d i n the c o l l a g e n f o r m a t i o n , b u t i t i s v e r y d i f f i c u l t t o imagine the f u n c t i o n of such a p a t t e r n . The u s e f u l n e s s o f such a development Is q u e s t i o n a b l e s i n c e , i n t h e summer o f I966 when a second e s t r o u s o c c u r r e d w i t h o u t any a p p r e c i a b l e v a g i n a l growth, b r e e d i n g was s t i l l s u c c e s s f u l . I t was n o t p o s s i b l e t o d e t e r m i n e whether o v u l a t i o n i n the r e d s q u i r r e l i s spontaneous o r i n d u c e d . C l t e l l u s t r i d ec eml I n e a t u s i s an in d u c e d o v u l a t o r ( F o s t e r , 193*0 a n ( i A s d e l l ( I 9 6 6 ) s u g g e s t s t h a t many o t h e r s c i u r . i d s a r e a l s o . One female t a k e n d u r i n g a m a t i n g chase had a l r e a d y o v u l a t e d and s u g g e s t s t h a t o v u l a t i o n i n t h e r e d s q u i r r e l i s spontaneous. Age a t M a t u r i t y The q u e s t i o n o f age a t m a t u r i t y Is an i n t e r e s t i n g one t h a t i s d i f f i c u l t t o e v a l u a t e . The males, a d u l t s and j u v e n i l e s , come i n t o b r e e d i n g c o n d i t i o n i n synchrony and r e m a i n f u n c t i o n a l f o r the same l e n g t h o f t i m e . I n I967 a l l males were i n f u n c t i o n a l c o n d i t i o n i n l a t e J a n u a r y . Of t h e s e , the males b o r n i n June 1966 were seven months o l d when th e y a t t a i n e d s e x u a l m a t u r i t y , whereas t h o s e i n l a t e August were o n l y f i v e months o l d . I t i s p o s s i b l e t h a t most o f t h e young b o r n l a t e i n ' t h e y e a r had d i f f i c u l t y i n e s t a b l i s h i n g a t e r r i t o r y and h a r v e s t i n g a food s u p p l y b e f o r e w i n t e r s e t i n and were thus l e s s l i k e l y t o s u r v i v e . F o r t h i s r e a s o n , a - 6 0 -c o n s e r v a t i v e e s t i m a t e o f age a t m a t u r i t y o f males would be 7 months. The age s t r u c t u r e i n t h e female segment of t h e p o p u l a t i o n would be s i m i l a r t o t h e males, but m a t u r i t y i n r e l a t i o n t o age p r e s e n t s a c o n f u s i n g p i c t u r e . I n 1 9 6 6 a l l females b r e d a t t h e same t i m e . I n 19&7 many o f the young o f t h e p r e v i o u s y e a r d i d not b r e e d . Only about one t h i r d o f t h e young females b r e d I n 19&7 a n c l t h e y were p r o b a b l y about 7 months o l d . I t cannot be assumed t h a t t h e two t h i r d s t h a t d i d n o t br e e d were t o o young'to do so s i n c e t h e r e was no s i g n i f i c a n t d i f f e r e n c e (P=.5) between t h e eye l e n s w e i g h t s o f t h o s e j u v e n i l e s t h a t d i d br e e d and t h o s e t h a t d i d n o t . Thus i t appears t h a t age i t s e l f d i d n o t cause t h e l a c k o f b r e e d i n g among j u v e n i l e s . The age o f m a t u r i t y f o r t h e females as w e l l as males can be g i v e n a c o n s e r v a t i v e e s t i m a t e o f 7 months. The B r e e d i n g Season The b r e e d i n g season o f t h e r e d s q u i r r e l n o r m a l l y b e g i n s d u r i n g t h e w i n t e r months. I n New York development o f t h e male organs b e g i n s i n l a t e November and December and b r e e d i n g o c c u r s i n J a n u a r y (Layne, 195^). I n B r i t i s h C o l u m b i a S m i t h (I965) found males i n b r e e d i n g c o n d i t i o n i n March. I n t h e p r e s e n t s t u d y , t h e t i m i n g o f t h e b r e e d i n g season d u r i n g 1966 and 19&7 was d e t e r m i n e d by a s s e s s i n g t h e monthly o c c u r r e n c e o f l a c t a t i o n among f e m a l e s . - 61-L a c t a t l o n can r e a d i l y be d e t e r m i n e d on s t u d y s k i n s and t h e f r e q u e n c y o f t h e o c c u r r e n c e o f l a c t a t i o n was p l o t t e d f o r specimens i n t h e V e r t e b r a t e Museum 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 olumbia i n o r d e r t o g e t some Idea o f the v a r i a t i o n and l i m i t s o f t h e b r e e d i n g seasons i n B r i t i s h C o l umbia. F i g u r e 4 shows t h e f r e q u e n c y o f l a c t a t i o n f o r 1966 and 1967 and f o r B r i t i s h C olumbia over the p a s t 30 y e a r s . The e a r l i e s t o c c u r r e n c e o f l a c t a t i o n , d e t e r m i n e d from t h e s t u d y s k i n s , i s A p r i l . I n I967 l a c t a t i o n was a l s o e v i d e n t i n A p r i l and i t appears t h e r e f o r e t h a t the 1967 b r e e d i n g season can be r e g a r d e d as an e a r l y one. I n 1966 l a c t a t i o n d i d n o t o c c u r u n t i l June and was a p p a r e n t l y l a t e . A d d i t i o n a l i n f o r m a t i o n on b r e e d i n g s e a s o n v a r i a t i o n s was r e c o r d e d by S m i t h (I965). He found l a c t a t i n g females i n May o f 1962 and. I963 b u t none u n t i l J u l y i n 1964. I t appears l i k e l y t h a t a r i g i d l y timed breeding-s e a s o n does not o c c u r i n the r e d s q u i r r e l . I t i s e x t r e m e l y o p p o r t u n i s t i c i n i t s c h o i c e o f h a b i t a t and f o o d and i s a p p a r e n t l y a l s o an o p p o r t u n i s t i c b r e e d e r . The e x a c t f a c t o r s b e h i n d the t i m i n g o f any one season r e m a i n unknown, b u t t h e g e n e r a l weather c o n d i t i o n s do appear t o be an i n f l u e n c e on t h e time o f b r e e d i n g . The w i n t e r o f 1965-66 was s e v e r e w i t h t h r e e t i m e s t h e normal s n o w f a l l on t h e a r e a s s t u d i e d , and the b r e e d i n g season was l a t e . The b r e e d i n g season i n 1964 FIGURE 4 - The f r e q u e n c y o f l a c t a t i o n as i n d i c a t e d by t h e c o n d i t i o n o f t h e n i p p l e s i n 19&6, 19&7 a n c ^ °f p r e v i o u s l y c o l l e c t e d a n i m a l s i n the V e r t e b r a t e Museum 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 , MONTH -63-was a l s o l a t e (Smith, 1965) and was preceded by an above ave r a g e s n o w f a l l . The e a r l y s e a s o n i n 1967 was preceded by a v e r y m i l d w i n t e r . S i m i l a r d a t a i n w h i c h a d e l a y e d s e a s o n was preceded by a s e v e r e w i n t e r , was found f o r t h e g r a y s q u i r r e l by S h o r t e n (195*0. I t i s d i f f i c u l t t o v i s u a l i z e j u s t how s n o w f a l l c o u l d a f f e c t the normal a c t i v i t i e s o f t h e s q u i r r e l , s i n c e i t r e a d i l y burrows t h r o u g h t h e snow t o i t s f o o d caches and t h e snow p r o v i d e s an i n s u l a t i n g c o v e r f o r t h e a n i m a l s t o work bene a t h . A g r e a t d e a l o f snow, however, would f o r c e t h e a n i m a l t o spend more time d i g g i n g and l e s s t i m e e a t i n g . S e v e r e weather would a l s o f o r c e t h e a n i m a l t o spend more t i m e h o l e d up and l e s s t ime f o r a g i n g . I t was n o t p o s s i b l e t o compare t h e w i n t e r c o n d i t i o n o f a n i m a l s d u r i n g m i l d and s e v e r e w i n t e r s because o f s m a l l w i n t e r sample s i z e s . No a n i m a l s were n o t i c e a b l y f a t a t any time o f y e a r . A l t h o u g h t h e r e i s c o n s i d e r a b l e s y n c h r o n y i n b o t h males and females d u r i n g any one b r e e d i n g season t h e r e i s c o n s i d e r a b l e v a r i a t i o n i n the d u r a t i o n o f t h e b r e e d i n g season o f d i f f e r e n t y e a r s . I n most y e a r s t h e f u n c t i o n a l p e r i o d o f t h e males l a s t s about t h r e e months, as was found i n 1967 and o v e r t h r e e y e a r s from I 9 6 I t o 1964 by S m i t h (I965). O c c a s i o n a l l y t h e season l a s t s about s i x months as found i n 1966 when an a d d i t i o n a l l i t t e r was produced. The s i n g l e i n s t a n c e o f an extended -64-• b r e e d i n g season i n 1966, out o f f i v e y e a r s o f r e c o r d s , 1961-64 ( S m i t h , 1965) and 1965-67 ( p r e s e n t s t u d y ) , s u g g e s t s t h a t two l i t t e r s a r e r a t h e r uncommon i n B r i t i s h C o lumbia, T h i s i s i n s h a r p c o n t r a s t t o t h e f i n d i n g s o f Layne (1954) i n New York where t h e f u n c t i o n a l season f o r t h e males commonly l a s t s f o r about 6 months and many females produce two l i t t e r s . An a d d i t i o n a l p o i n t o f c o n t r a s t i s seen i n t h e males. Two d i s t i n c t peaks I n male r e p r o d u c t i v e organ s i z e a r e found i n t h e e a s t b u t n o t i n t h e west. I t seems u n l i k e l y t h a t l a t i t u d e i s a dominant i n f l u e n c e i n t h i s d i f f e r e n c e s i n c e o n l y about 9° o f l a t i t u d e s e p a r a t e s the a r e a s , and s o u t h e r n B r i t i s h C o l u m b i a has a r e l a t i v e l y m i l d c l i m a t e compared t o more I n l a n d r e g i o n s o f s i m i l a r l a t i t u d e s , A p o s s i b l e e x p l a n a t i o n can be seen i n t h e h a b i t a t d i f f e r e n c e s between e a s t and west. C o n i f e r o u s f o r e s t s dominate t h e w e s t e r n h a b i t a t o f t h e r e d s q u i r r e l w h i l e much o f t h e e a s t e r n h a b i t a t where r e d s q u i r r e l s were s t u d i e d c o n s i s t s o f mixed d e c i d u o u s f o r e s t s . I n d e c i d u o u s f o r e s t s two d i s t i n c t f r u i t i n g seasons o c c u r ; t h e f i r s t i n v o l v i n g e a r l y s p r i n g p l a n t s t h a t bloom and f r u i t b e f o r e t h e l e a v e s o f t h e t r e e s form a c l o s e d canopy; and t h e second i n v o l v i n g t h e f r u i t i n g t r e e s i n l a t e summer (B r a u n , 1950). C o n i f e r o u s f o r e s t s p r e s e n t a c l o s e d canopy y e a r round and o n l y one main f r u i t i n g s e a s o n o c c u r s i n l a t e summer. E a r l y f l e s h y f r u i t s , t r e e buds, and f l o w e r s a r e major s p r i n g foods o f e a s t e r n -65-s q u i r r e l s (Layne,195 i*') w h i l e i n t h e west such foods a r e u t i l i z e d v e r y l i t t l e . I t i s p o s s i b l e t h a t t h e e a s t e r n r e d s q u i r r e l r esponds t o the mixed d e c i d u o u s f o r e s t h a b i t a t by e x h i b i t i n g two d i s t i n c t b r e e d i n g peaks, so t h a t t h e young a r e produced a t t h e two times when food i s most abundant. I n t h e west t h e c o n i f e r o u s f o r e s t s do n o t n o r m a l l y p r o v i d e f a v o r a b l e c o n d i t i o n s f o r s q u i r r e l s t o produce two l i t t e r s and I t I s o n l y under p a r t i c u l a r l y f a v o r a b l e c o n d i t i o n s s u c h a l a r g e s t o r e o f good w i n t e r f o o d and a f a v o r a b l e s p r i n g t h a t t h e y can produce more t h a n one l i t t e r . D e s p i t e y e a r l y v a r i a t i o n s I n t h e time and d u r a t i o n o f b r e e d i n g t h e r e i s v e r y c l o s e s y n c hrony between peaks i n t h e male organ s i z e s and t h e o c c u r r e n c e o f e s t r o u s i n t h e f e m a l e s . I t appears t h a t the e x t e r n a l c o n d i t i o n s t h a t o p e r a t e on t h e p o p u l a t i o n t o i n i t i a t e b r e e d i n g o p e r a t e e q u a l l y on b o t h sexes t o b r i n g them i n t o c o n d i t i o n a t about t h e same t i m e . Some v a r i a t i o n i s e v i d e n t i n t h e i n i t i a t i o n o f b r e e d i n g . The females came i n t o c o n d i t i o n a month a f t e r the males i n 1966 b u t a t t h e same t i m e i n I967. The peaks i n male organ s i z e i n b o t h y e a r s c o i n c i d e d w i t h e s t r o u s i n t h e females and s u g g e s t s t h a t a s y n c h r o n i z i n g mechanism i s o p e r a t i n g between t h e s e x e s . S m i t h (I965) s u g g e s t s t h a t t h e a n a l g l a n d o r t h e v a g i n a might produce o d e r i f e r o u s s u b s t a n c e s t h a t c o u l d a t t r a c t t h e males and a i d i n s e x u a l s y n c h r o n y . -66-However, t h e gr o s s appearance o f t h e a n a l g l a n d i s t h e same i n b o t h sexes t h e y e a r round and t h e r e v/ere no a p p a r e n t h i s t o l o g i c a l d i f f e r e n c e s i n the 57 a n a l g l a n d s c o l l e c t e d d u r i n g t h e summer o f I966. Thus t h e a n a l g l a n d p r o b a b l y does n ot o p e r a t e i n t h i s mechanism. Whether o r n o t the v a g i n a produces an o d e r l f e r o u s s u b s t a n c e t h a t s t i m u l a t e s t h e male remains t o be i n v e s t i g a t e d . F e c u n d i t y There a r e d i s t i n c t y e a r l y d i f f e r e n c e s i n b r e e d i n g . A low p o p u l a t i o n i n 1966 showed a l l females p a r t i c i p a t i n g i n an extended b r e e d i n g s eason and p r o d u c i n g two l a r g e l i t t e r s . The h i g h p o p u l a t i o n o f t h e I n t e r i o r i n I967 showed a l l a d u l t females b u t few young p a r t i c i p a t i n g i n a s h o r t b r e e d i n g season and p r o d u c i n g one s m a l l l i t t e r . The low I s l a n d p o p u l a t i o n I n 1967 showed a s i m i l a r p a t t e r n t o t h e h i g h I n t e r i o r p o p u l a t i o n of t h e same y e a r . P r e I m p l a n t a t i o n l o s s e s appear c o n s t a n t a t about 11% i n a l l t h r e e i n s t a n c e s , P o s t i m p l a n t a t i o n m o r t a l i t y was e v i d e n t o n l y i n t h e h i g h p o p u l a t i o n i n 19&7 b u t may have been p r e s e n t i n the low 1967 p o p u l a t i o n as w e l l . These changes i n r e p r o d u c t i o n do n o t f i t a p a t t e r n o f an I n t r i n s i c d e n s i t y dependent c o n t r o l system. An i n d i r e c t measurement o f p o p u l a t i o n l e v e l , based on r a t e o f c a l l s and k i l l p e r day shows no c l e a r r e l a t i o n s h i p between p o p u l a t i o n d e n s i t y and r e p r o d u c t i v e o u t p u t . I n I967 t h e a r e a t h a t had a p o p u l a t i o n Index much h i g h e r t h a n t h e o t h e r had a v e r y low r e p r o d u c t i v e r a t e and d e n s i t y dependent f a c t o r s may have been o p e r a t i n g a t t h a t t i m e . -67-The Vancouver I s l a n d p o p u l a t i o n had a low p o p u l a t i o n Index I n b o t h y e a r s , b u t showed a complete r e v e r s a l o f r e p r o d u c t i v e o u t p u t i n one y e a r o ver t h e o t h e r . I n t h i s case i t i s d i f f i c u l t t o see how a d e n s i t y dependent mechanism i s a p r i m a r y f a c t o r r e g u l a t i n g r e p r o d u c t i o n . F e c u n d i t y does seem t o f l u c t u a t e w i t h t h e ty p e o f food a v a i l a b l e . R e g a r d l e s s o f p o p u l a t i o n l e v e l , t h e r e was a h i g h r e p r o d u c t i v e performance a f t e r f e e d i n g a l l w i n t e r on s t o r e d l o d g e p o l e p i n e cones, and a r e l a t i v e l y low r e p r o d u c t i v e o u t p u t a f t e r f e e d i n g on a heavy Douglas f i r cone c r o p d u r i n g the w i n t e r . Smith's d a t a (I965) shows a s i m i l a r phenomenon. R e p r o d u c t i o n was low I n 1962 a f t e r f e e d i n g on Douglas f i r cones and h i g h i n 1964 a f t e r f e e d i n g on l o d g e p o l e p i n e cones. There i s c o n s i d e r a b l e c o n t r o v e r s y as t o whether r e p r o d u c t i o n i n mammals i s c o n t r o l l e d by d e n s i t y dependent f a c t o r s o r t h r o u g h t h e amount o f food a v a i l a b l e t o s u p p o r t t h e r a i s i n g o f o f f s p r i n g . L a c k (195*0 p r e s e n t s c o n v i n c i n g e v i d e n c e t h a t t h e c l u t c h s i z e i n some b i r d s v a r i e s d i r e c t l y w i t h the a v a i l a b i l i t y o f f o o d . He su g g e s t s t h a t the same mechanism o p e r a t e s i n .mammals'. A l t h o u g h l i t t l e c o n c l u s i v e e v i d e n c e i s r e c o r d e d f o r s c i u r i d mammals, an a p p a r e n t e f f e c t o f food s u p p l y on r e p r o d u c t i o n i s seen i n t h e f o x s q u i r r e l . S i g n i f i c a n t l y l a r g e r l i t t e r s were found i n c o r n f i e l d h a b i t a t t h a n i n a r e a s o f mixed hardwoods (Brown and Yeager,19^5). Most -68-f o x s q u i r r e l s o f t h e hardwoods d i d n o t b r e e d when t h e . a c o r n c r o p f a i l e d , b u t a few d i d so i n f a r m l a n d where th e y had a s u b s i d i a r y f o o d s u p p l y ( A l l e n ^ 1 9 ^ 3 ) . S u p p o r t f o r t h e p o s s i b i l i t y t h a t t h e food • s u p p l y m i g h t be c r i t i c a l f o r b r e e d i n g r e d s q u i r r e l s i s enhanced by t h e h i g h m e t a b o l i c r a t e o f t h e s p e c i e s . T h e i r b a s a l m e t a b o l i c r a t e i s 80% h i g h e r t h a n t h a t o f o t h e r a n i m a l s o f s i m i l a r s i z e and d u r i n g c o l d weather i t i n c r e a s e s ( I r v i n g , K r o g , and Honson, 1955). Under t h e s e p h y s i o l o g i c a l c o n d i t i o n s a w i n t e r s h o r t a g e o f food would be d e t r i m e n t a l t o t h e c o n d i t i o n o f the a n i m a l . S i n c e r e d s q u i r r e l s b e g i n b r e e d i n g d u r i n g t h e c o l d w i n t e r months, a f o o d s h o r t a g e c o u l d be r e f l e c t e d i n t h e i r whole r e p r o d u c t i v e performance. I n the p r e s e n t s t u d y a change i n f o o d s p e c i e s r a t h e r t h a n an absence o f food was f o l l o w e d by a change i n r e p r o d u c t i v e o u t p u t . There a r e s e v e r a l p o s s i b l e f a c t o r s i n v o l v i n g b o t h the h a b i t s o f t h e s q u i r r e l s and t h e f r u i t i n g h a b i t s o f the c o n i f e r s t h a t c o u l d a f f e c t t h e c a p a c i t y o f the r e d s q u i r r e l t o produce more young i n l o d g e p o l e p i n e f o r e s t s . F i r s t , t he w e s t e r n r e d s q u i r r e l i s p a r t i c u l a r l y w e l l adapted t o i n h a b i t a t i n g open f o r e s t s dominated by l o d g e p o l e p i n e . B o t h t h e i r p e l a g e c o l o r and v o c a l i z a t i o n a r e adapted t o an open f o r e s t s i t u a t i o n such as l o d g e p o l e p i n e s i t e s , and t h e i r jaw m u s c u l a t u r e i s s u f f i c i e n t l y p o w e r f u l t o enable them t o ouen the tough s e r o t i n o u s p i n e cones ( S m i t h , 19'$5). I n t h e s e r e s p e c t s i t i s - 6 9 -advantageous f o r the r e d s q u i r r e l t o l i v e i n l o d g e p o l e p i n e h a b i t a t . S e c o n d l y , t h e r e a r e advantages t o f e e d i n g on l o d g e p o l e p i n e cones. L o d g e p o l e p i n e produces a r e l a t i v e l y s t a b l e cone c r o p y e a r a f t e r y e a r , t h e cones r e m a i n on the t r e e s f o r many months and many o f them do not open u n t i l s u b j e c t e d t o i n t e n s e h e a t ( C r o s s l e y , 1952). By h a r v e s t i n g l o d g e p o l e p i n e cones the s q u i r r e l i s s u r e o f a r e l a t i v e l y c o n s t a n t c r o p o f cones t h a t r e t a i n t h e i r seeds u n t i l needed. T h i s i s b e n e f i c i a l t o t h e s q u i r r e l s i n c e a l m o s t a l l t h e cones s t o r e d a r e a v a i l a b l e as food t h r o u g h o u t t h e w i n t e r . Of 93 l o d g e p o l e p i n e cones t a k e n from s q u i r r e l caches i n 196? o n l y e i g h t p e r c e n t were open. The seeds d r o p out o f t h e s e open cones and a p p a r e n t l y a r e n o t u t i l i z e d by t h e s q u i r r e l s , f o r my c a p t i v e s q u i r r e l s , w h i c h r e a d i l y a t e c l o s e d cones, would n ot attempt t o f e e d on open cones even when no o t h e r f o o d was a v a i l a b l e . I n th e w i l d no s q u i r r e l s were observed f e e d i n g on open cones o r t h e i r i n d i v i d u a l seeds. The p o s s i b i l i t y e x i s t s t h a t t h e seeds c o u l d be r e t r i e v e d from the ground b u t c o n i f e r seeds a r e s m a l l and t h e energy expended i n s e a r c h i n g f o r them would p o s s i b l y exceed t h e energy o b t a i n e d . Thus l o d g e p o l e p i n e cones a r e a good w i n t e r f o o d f o r s q u i r r e l s s i n c e t h e r e i s a r e l i a b l e y e a r l y cone c r o p and most o f t h e cones s t o r e d remain c l o s e d and can be used by t h e s q u i r r e l s t h r o u g h o u t t h e w i n t e r . -70-Douglas f i r cones on t h e o t h e r hand p r e s e n t s e v e r a l u n c e r t a i n t i e s t o t h e r e d s q u i r r e l even though t h e y a r e e a s i e r t o open t h a n l o d g e p o l e p i n e and i n i t i a l l y have a h i g h e r c a l o r i c c o n t e n t o f seeds t h a n do t h e p i n e (Smith,1965). Douglas f i r t r e e s have e x t r e m e l y v a r i a b l e cone c r o p s and i t i s o n l y d u r i n g y e a r s o f good y i e l d t h a t t h e s q u i r r e l h a r v e s t s them i n any g r e a t amount. Douglas f i r cones open and d r o p t h e i r seeds a t m a t u r i t y and, u n l e s s h a r v e s t e d by s q u i r r e l s i n t h e i r c l o s e d s t a t e b e f o r e t h i s t i m e , a r e n o t a v a i l a b l e as a s o u r c e o f w i n t e r f o o d . When Douglas f i r cones a r e abundant a l a r g e cache o f them I s n o t n e c e s s a r i l y i n d i c a t i v e o f t h e amount t h a t w i l l be a v a i l a b l e t o s q u i r r e l s t h r o u g h o u t t h e w i n t e r . Many f i r cones open i n t h e caches and t h e i r seeds a r e l o s t . Of 94 Douglas f i r cones removed from caches I n the I n t e r i o r i n I967, kj>% were found t o be open. Under t h e s e c i r c u m s t a n c e s o n l y about h a l f the s t o r e d cones would be a v a i l a b l e f o r f u t u r e use. Most o t h e r c o n i f e r s produce cones t h a t r e a d i l y open and thus f a l l I n t o t h e poor f o o d c a t e g o r y w i t h Douglas f i r . I n t h i s manner a good s t o r e o f l o d g e p o l e p i n e cones i s b e n e f i c i a l t o the s q u i r r e l w h i l e a h a r v e s t o f f i r cones o n l y appears t o be so. The s q u i r r e l seems t o c o n c e n t r a t e on whatever cones a r e most r e a d i l y a v a i l a b l e . D u r i n g a good Douglas f i r cone c r o p the h a r v e s t i s c o n c e n t r a t e d on t h a t c o n i f e r s p e c i e s , and t h e s q u i r r e l s -71-l e a v e most o f t h e p i n e cones on t h e t r e e s . I t i s not known why the r e d s q u i r r e l c o n c e n t r a t e s on f i r cones w h i l e a s t a b l e p i n e cone c r o p i s a v a i l a b l e . They may p r e f e r t h e s o f t e r f i r cones because t h e y a r e e a s i e r t o open. The s q u i r r e l s can s t i l l go back and c u t t h e p i n e cones, b u t i t means t h a t t h e energy expended i n c o l l e c t i n g t h e f i r s t h a r v e s t i s l a r g e l y wasted. Thus poor w i n t e r caches o f p i n e cones may p r o v i d e the s q u i r r e l s w i t h enough energy t o produce a l a r g e l i t t e r , o r i n e x c e p t i o n a l y e a r s , two l i t t e r s p e r b r e e d i n g f e m a l e . On t h e o t h e r hand, a s u p p l y o f f i r cones may f u r n i s h o n l y enoiigh energy t o produce a s m a l l l i t t e r , o r i n t h e case o f young a n i m a l s w h i c h need energy f o r growth and development as w e l l as maintenance, none a t a l l . T h i s , i n p a r t , I s a p o s s i b l e e x p l a n a t i o n o f t h e c o m p a r a t i v e l y g r e a t e r s u c c e s s o f b r e e d i n g I n 1966 o v e r I 9 6 7 . I t i s n o t l i k e l y a t o t a l e x p l a n a t i o n , however f o r t h e r e was a d i f f e r e n c e i n l i t t e r s i z e between the two p o p u l a t i o n s I n I 9 6 7 . T h i s may have been due t o d i f f e r e n c e s i n t h e weather, s p r i n g f o o d s u p p l y , o r t h e major h a b i t a t d i f f e r e n c e s between the two a r e a s , The r e s o r b i n g embryos found i n 1967 c o u l d have been an I n d i r e c t r e s u l t o f t h e a n i m a l s b r e e d i n g b e f o r e t h e snow had m e l t e d , a t a time when t h e r e were no f r e s h f u n g i o r growing p l a n t s on w h i c h t h e p r e g n a n t - f e m a l e s c o u l d f e e d . D e s p i t e t h e s t r o n g c o r r e l a t i o n between b r e e d i n g s u c c e s s and foo d s u p p l y i n the p o p u l a t i o n s s t u d i e d , t h e p o s s i b i l i t y o f i n t r i n s i c d e n s i t y dependent f a c t o r s o p e r a t i n g cannot be Ignored. P o p u l a t i o n s do n o t r e m a i n s t e a d y and a l t h o u g h t h e Vancouver I s l a n d and I n t e r i o r p o p u l a t i o n s were d i f f e r e n t i t was not d e t e r m i n e d whether t h e p o p u l a t i o n s were i n c r e a s i n g o r d e c r e a s i n g . Such d a t a would a i d c o n s i d e r a b l y t h e e v a l u a t i o n o f the r o l e o f d e n s i t y dependent f a c t o r s i n c o n t r o l l i n g r e p r o d u c t i o n . F u r t h e r s t u d y i s needed t o e v a l u a t e more f u l l y the e f f e c t s o f the q u a l i t y o f the f o o d s u p p l y and o f d e n s i t y dependent f a c t o r s on b r e e d i n g i n t h e r e d s q u i r r e l , b u t i t appears t h a t t h e foo d f a c t o r e x e r t s a marked i n f l u e n c e on t h e y e a r l y p r o d u c t i o n o f young. PLATE I A. The Vancouver Island habitat An open rocky s i t e . . Arbutus, Douglas f i r and lodgepole pine are the dominant trees and ocean spray and salal are the dominant shrubs. B, Dense vegetation, A stand of predominantly Douglas f i r where salal forms a thick understory. PLATE II The Interior habitat A. An open site forested with Douglas f i r , lodgepole pine and ponderosa.'pine. Snowbrush is the dominant shrub. B. A dense stand of mixed.lodgepole pine and Douglas f i r , Soopalalie is present in the sparse slirub layer. -74-PLATE I I I - S e a s o n a l changes i n t h e t e s t e s . A. I n f a n t i l e male. The s m a l l c l o s e l y packed s e m i n i f e r o u s t u b u l e s a r e bounded by smooth basement membranes, Mag. X 101. B. D e v e l o p i n g male. The t u b u l e s , s e p a r a t e and l u m i n a form i n c o n j u n c t i o n w i t h s p e r m a t o g e n i c a c t i v i t y . Mag. X 169. C, E a r l y f u n c t i o n a l male. L a r g e clumps o f L e y d i g c e l l s a r e p r e s e n t and t h e t u b u l e l u m i n a a r e packed w i t h spermatozoa. Mag. X I69. D. L a t e f u n c t i o n a l male. L e y d i g c e l l s a r e s m a l l and t h e t u b u l e s c o n t a i n fewer spermatozoa. Mag. X 169. E. E a r l y d e g e n e r a t e male. L e y d i g c e l l s a r e v e r y s m a l l and t h e t u b u l e l u m i n a a r e c l o g g e d w i t h c e l l u l a r d e b r i s . Mag. X 169. PLATE IV - Seasonal changes i n the epididymides A. I n f a n t i l e . Very l i t t l e cytoplasm i s presen i n the e p i t h e l i a l c e l l s l i n i n g the tubules. Mag. X 169. B. Developing. The epithelium of the tubules forms a p s e u d o s t r a t i f i e d l a y e r and possesse a small amount of a p i c a l cytoplasm. Mag. X I69. C. F u n c t i o n a l . The i n t e r t u b u l a r connective t i s s u e i s very t h i n and the tubules are packed vrith sperm. Mag. X I69. D. E a r l y degenerate. The tubules s h r i n k , the r e l a t i v e amount of connective t i s s u e increases and leucocytes are present. Mag. X I 6 9 . PLATS V Seasonal changes in the seminal vesi c l e s A. I n f a n t i l e . The lumina are open but the secretory epithelium i s disorganized. Mag. X 1 6 9 . \" B. Early Development, organization of the is evident. Mag. X Only the i n i t i a l secretory eoithelium 1 6 9 . C. Functional. Consecutive stages i n the development of the epithelium from (i) a folded epithelium of elongate c e l l s , to ( i i ) a pseudostratified c e l l layer with oval n u c l e i , to ( i i i ) a single cuboidal c e l l layer Mag. X I69. D. Late functional. The epithelium becomes pseudostratified and possesses only a small amount of cytoplasm. Secretion droplets are s t i l l present. Mag. X 169.-PLATE VI - S e a s o n a l changes i n t h e p r o s t a t e A. I n f a n t i l e . The s m a l l t u b u l e s p o s s e s s no open l u m i n a and no o r g a n i z e d e p i t h e l i u m . Mag. X 169 B. E a r l y Development. I n i t i a l l y t h e e p i t h e l i u m becomes o r g a n i z e d and l u m i n a open b e f o r e t h e e p i t h e l i a l c e l l c y l o p l a s m o c c l u d e s i t . Mag. X I69. C. F u n c t i o n a l . The g l a n d s show p r o g r e s s i v e changes from ( i ) t h e e a r l y f u n c t i o n a l s t a t e vrhere t h e l u m i n a a r e l a r g e l y o c c l u d e d by s e c r e t o r y c e l l c y t o p l a s m , t o ( i i ) t h e l a t e f u n c t i o n a l s t a t e - w h e r e t h e c y t o p l a s m i s reduced and the l u m i n a l a r g e r . Mag. X 169. D. Degenerate. The t u b u l e s become h e a v i l y n u c l e a t e d and w i t h o u t l u m i n a and a r e s u p p o r t e d by c o l l a g e n i c c o n n e c t i v e t i s s u e s . Mag. X I69. PLATE V I I ~ S e a s o n a l changes i n the v a g i n a . A. I n f a n t i l e . The lumen i s c o n v o l u t e d but the e p i t h e l i u m i s o r g a n i z e d . The o u t e r t i s s u e l a y e r s a r e h e a v i l y n u c l e a t e d . Mag. X 101. B. E a r l y P r o e s t r o u s . The t i s s u e l a y e r s and t h e l u m i n a i n c r e a s e d u r i n g the i n i t i a l s t a g e s . Mag. X 101. C. E s t r o u s . The l a m i n a p r o p r i a becomes l o o s e and h i g h l y c o l l a g e n i c , a t h i c k g e r m i n a t i v u m forms and the cornium s l o u g h s h e a v i l y . Mag. X 40. D. L a t e Pregnancy. The c o l l a g e n d e c r e a s e s c o n s i d e r a b l y and t h e e p i t h e l i u m r e t u r n s t o a t h i n l a y e r . L e u c o c y t e s a r e s t i l l p r e s e n t . Mag. X 40. E. E a r l y A n o e s t r o u s . A l l t i s s u e l a y e r s s h r i n k and become h e a v i l y n u c l e a t e d , and s c l e r o t i c b l o o d v e s s e l s d e v e l o p . Mag, X 101. i PLATE V I I I S e a s o n a l changes i n the u t e r u s . A. I n f a n t i l e . A l l t i s s u e s a r e h e a v i l y n u c l e a t e d and e n d o m e t r i a l g l a n d s a r e s c a r c e . Mag. X 101. B. E s t r o u s . A l l t i s s u e l a y e r s a r e t h i c k . The lumen p r e s e n t s a c o n v o l u t e d s u r f a c e and e n d o m e t r i a l g l a n d s a r e open. Mag. X 40. C. Recent P o s t Partum. The t i s s u e and e p i t h e l i u m a r e h e a v i l y n u c l e a t e d and s c h l e r o t i c b l o o d v e s s e l s d e v e l o p . Mag. X 101. D. A n o e s t r o u s . S c h l e r o t i c b l o o d v e s s e l s a r e p r e s e n t , the t i s s u e s a r e h e a v i l y n u c l e a t e d , and e n d o m e t r i a l g l a n d s a r e m i n i m a l . I n w i n t e r (1) t h e r e i s l i t t l e c o l l a g e n p r e s e n t , b u t i n summer ( i i ) the c o l l a g e n i s d i s t i n c t . Mag. X 101. PLATE IX - Seasonal changes i n the Ovary. A. I n f a n t i l e . A thick c o r t i c a l layer of naked ova predominates for the f i r s t three to four months of l i f e . ( i ) Then secondary and regressing f o l l i c l e s appear at about four to f i v e months of age. Mag, X 68 ( i i ) and changes continue u n t i l near Proestrous. Mag. X 40. ( i i i ) Mag. X 40. B. Post Ovulation. The corpus luteum forms rapid l y although the blood c l o t may be v i s i b l e u n t i l a f t e r implantation. Mag. X 68. .C. Anoestrous, Naked ova are scarce and corpa a l b i c a n t i a (centre) may remain u n t i l the next breeding season. Mag. X 40. PLATE X - Changes I n t h e C o r p o r a L u t e a A. Pregnancy and l a c t a t i o n , There i s l i t t l e change i n the c o r p o r a l u t e a s t r u c t u r e from ( i ) e a r l y pregnancy, t o ( i i ) l a t e pregnancy, t o ( i i i ) l a c t a t i o n . Mag. X B. L a t e l a c t a t i o n . The i n i t i a l d e g e n e r a t i v e change i s a s e p a r a t i o n o f the l u t e a l c e l l s , Mag, X I69. C. E a r l y a n o e s t r o u s . V a c u o l a t i o n and f u r t h e r d e g e n e r a t i v e changes t a k e p l a c e about t h r e e months p o s t partum. Mag. X 101. - 8 2 --83-ACKNOWLEDGEMENTS I w i s h t o thank my s u p e r v i s o r , D r. J . M . T a y l o r , whose s u p p o r t and encouragement made t h i s s t u d y p o s s i b l e . Dr. C. C. S m i t h k i n d l y made h i s u n p u b l i s h e d d a t a on the s p e c i e s a v a i l a b l e t o me. D i s c u s s i o n w i t h Dr. V. J . K r a j i n a r e g a r d i n g the v e g e t a t i o n and p l a n t a s s o c i a t i o n s were v e r y u s e f u l . E x t r e m e l y h e l p f u l c r i t i c i s m was p r o -v i d e d by H . D. F i s h e r and D r . I . McT. Cowan. M r s . J . D. Hudson a i d e d i n t h e p r e p a r a t i o n o f t h e m a n u s c r i p t . 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R e p r o d u c t i o n I n C l t e l l u s b e l d l n g i and C l t e l l u s l a t e r a l i s I n n o r t h e a s t e r n C a l i f o r n i a . I n Comparative B i o l o g y o f R e p r o d u c t i o n I n Mammals, (I.W. Rowlands e d . ) . Academic P r e s s Inc.,-New York 559 P. Mossman, H.W. 1 9 6 6 . The r o d e n t o v a r y . I n c o m p a r a t i v e b i o l o g y of r e p r o d u c t i o n i n mammals, (I.W. Rowlands, e d . ) . Academic P r e s s I n c . , New York. Mossman, H.W., R.A. Hoffman, and C M . K i r k p a t r i c k . 1955. The a c c e s s o r y g e n i t a l g l a n d s o f male gray and f o x s q u i r r e l s c o r r e l a t e d w i t h age and r e p r o d u c t i v e c y c l e s . Am. J . Anat. 97: 257-302. • Mossman, H.W., J.W. Lawlah, and J.A. B r a d l e y . 1932. The male r e p r o d u c t i v e t r a c e o f the s c i u r l d a e . Am. J . Anat., 51: I89-I55. - 8 6 -Province of B r i t i s h Columbia, Dept. of A g r i c u l t u r e . Climate of B r i t i s h Columbia. Reports -for I 9 6 0 to 1 9 6 6 . Rasmussen, A.T. 1918. C y c l i c changes i n the i n t e r s t i t i a l c e l l s of the ovary and t e s t i s i n the woodchuck Marmota monax. Endocrinology 2: 353-404. Shorten, M. 195'+. S q u i r r e l s . C o l l i n s , London, 212 p. Smith, C.C. I 9 6 3 . T e r r i t o r i a l behavior i n the genus of s q u i r r e l Tamalsclurus M.S. Thesis Univ. of Washington^ 68 p. Smith, C.C. 1965. I n t e r s p e c i f i c Competition i n the genus of Tree s q u i r r e l Tamalsclurus Ph. D. Thesis, Univ. of Washington. 306 p. S t e e l , R.G.D. and J.H. T o r r i e . i960. P r i n c i p l e s and procedures of s t a t i s t i c s . McGraw-Hill Book Co. Inc Toronto. 481 p. "@en ; edm:hasType "Thesis/Dissertation"@en ; edm:isShownAt "10.14288/1.0104271"@en ; dcterms:language "eng"@en ; ns0:degreeDiscipline "Zoology"@en ; edm:provider "Vancouver : University of British Columbia Library"@en ; dcterms:publisher "University of British Columbia"@en ; dcterms:rights "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en ; ns0:scholarLevel "Graduate"@en ; dcterms:title "The reproductive biology of the western red squirrel."@en ; dcterms:type "Text"@en ; ns0:identifierURI "http://hdl.handle.net/2429/35904"@en .