UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The inter-relations of the introduced gray squirrel (Sciurus carolinensis) with the ecological conditions… Robinson, Donald Joseph 1951

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1951_A8 R63 I5.pdf [ 5.46MB ]
Metadata
JSON: 831-1.0107008.json
JSON-LD: 831-1.0107008-ld.json
RDF/XML (Pretty): 831-1.0107008-rdf.xml
RDF/JSON: 831-1.0107008-rdf.json
Turtle: 831-1.0107008-turtle.txt
N-Triples: 831-1.0107008-rdf-ntriples.txt
Original Record: 831-1.0107008-source.json
Full Text
831-1.0107008-fulltext.txt
Citation
831-1.0107008.ris

Full Text

(-£3 B7 19 Si A a (Z C b I 5 i THE INTER-RELATIONS OF THE INTRODUCED GRAY SQUIRREL (SCIURUS CAROLINENSIS) WITH THE ECOLOGICAL CONDITIONS IN STANLEY PARK by DONALD JOSEPH ROBINSON A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS IN THE DEPARTMENT OF ZOOLOGY We accept this thesis as conforming to the standard required from candidates f o r the degree of MASTER OF Members of the THE UNIVERSITY OF A p r i l , Department of BRITISH COLUMBIA 1 9 5 1 THE INTER-RELATIONS OF THE INTRODUCED GRAY SQUIRREL (SCIURUS CAROLINENSIS) WITH THE ECOLOGICAL CONDITIONS IN STANLEY PARK A b s t r a c t An Introduced p o p u l a t i o n o f S c l u r u s c a r o l l n e n s l a p l a n t e d at S t a n l e y Park, Vancouver, B.C. about 1913 has maintained i t s e l f s u c c e s s f u l l y f o r a t l e a s t 38 years In competition w i t h the indigenous s q u i r r e l S c i u r u s d o u g l a s l . T h i s p o p u l a t i o n was s t u d i e d through a p e r i o d of 18 months. I t was found t h a t the gray s q u i r r e l has reached a p o i n t o f s a t u r a t i o n i n the mixed d e c i d u o u s - c o n i f e r f o r e s t type f a v o r e d by i t . The s p r i n g p o p u l a t i o n approximates .7 p e r acre and the autumn p o p u l a t i o n about 1 per a c r e . Two l i t t e r s are born p e r year to a d u l t s q u i r r e l s , one to y e a r -l i n g s . These a r i s e from matings i n March and A p r i l and June and J u l y . The r a t i o between breeding females and young a t weaning age i s 1 to 1.6, i n d i c a t i n g a very low r e p r o d u c t i v e success. The gray s q u i r r e l i s not t e r r i t o r i a l i n i t s b e h a v i o r . Females move through an a r e a of 5 to 15 acres w i t h l i t t l e seasonal v a r i a t i o n . In the winter the males have about the same range of movements as the females but d u r i n g the re3t of the year they move i n a non random manner over an area of 50 to 55 a c r e s . Polygamy Is the r u l e w i t h s e v e r a l males competing f o r the r e c e p t i v e female. Dominance among such a group of males i s p o s i t i v e , p h y s i c a l and not a s s o c i a t e d w i t h t e r r i t o r y . The most important food p l a n t s are the vine maple (Acer c l r c l n a t u m ) and the b r o a d - l e a f e d maple (Acer macrophyllum). Pood storage takes place i n a random f a s h i o n w i t h i n a r a d i u s of 50 f e e t from the source. Subsequent recovery of s t o r e d food i s by random searc h i n g over the s t o r a g e area. The Douglas s q u i r r e l e x e r t s p h y s i c a l dominance over the gray s q u i r r e l but has a d i f f e r e n t h a b i t a t p r e f e r e n c e t h a t reduces c o m p e t i t i o n between the two s p e c i e s . Twenty-six b i r d s nests were watched i n the s q u i r r e l a r e a and o n l y two were d e s t r o y e d by them. Acknowledgments I wish to express my appreciation;to Dr. Ian McTaggart-Cowan .for the i n i t i a l Impetus of the investigation... and for his continued assistance throughout i t s course.. The summer f i e l d work was carried out through the help of a National Research Council grant. The B. C. Game Commission and the Parks Board of Vancouver rendered f u l l assistance and furthered the investigation by allowing the trapping of squ i r r e l s in. a game preserve. Zoo manager F. Beebe and head keeper T. Ferguson gave valuable assistance and advice during the study, I would l i k e to sincerely thank the following f o r the i r i n t e r e s t and assistance; Dr. P. A. Larkin; Mr. W. A. Sheppe; Mr. E. Taylor. Table of Contents Page Introduction 1 Taxonomic . Position and Description: 1 3 Methods 10 Population 12 Sex r a t i o ^ .5 Age Classes ]_7 Condition . . . . . 18 Pelage 20 Habitat. Preference 22 Intra S p e c i f i c Intolerance 25 Sp a t i a l Relationships 28 Daily movements 3 5 Seasonal movements » 3 3 Home range 22 A c t i v i t y 42 Time of day 42 Temperature 4g Humidity • 47 Wind 48 Overcast and p r e c i p i t a t i o n 49 Nesting 50 Leaf nests 50 Den trees 54 Resting platform 56 Predation 59 Parasites Reproduction . Breeding season Mating chase Development of the young Food Spring Summer F a l l Winter Food succession Storing of food Minerals Water . . . Human interference . . . . Relationship with the Douglas S q u i r r e l Relationship with Aves Modifying E f f e c t of the Environment . Food Nesting Reproduction Conclusions ; . . . . Literature cited L i s t of I l l u s t r a t i o n s F i g . No. Page 1. Cover map of gridded area showing r e l a t i o n -ship between conifer, mixed conifer-deciduous and maple stands. May, 1950 8 2 . Second growth conifers, mainly hemlock. February, 1951 , . 9 3. A stand of interwoven and prostrate vine maple trunks. February, 1951 9 4. The use accorded by the gray s q u i r r e l to each of the f l o r a l types „, . 23 5. Movements of a female s q u i r r e l from May, 1 9 5 0 to January, 1951 30 6. Movements of a female s q u i r r e l from June, 1950 to January, 1951 31 7. Movements of a female s q u i r r e l during June, July, 1950 3 2 8 . Movements of a male s q u i r r e l from May to September, 1950 . 3 3 9 . Movements of a male s q u i r r e l from June to August, 1950 34 10. Movements of a male s q u i r r e l from June to August, 1950 35 11. Relationship between time of day and s q u i r r e l a c t i v i t y . . . . . 43 12. An outside nest constructed on the crown of a hemlock . , 53 1 3 . A large cedar den tree on the study area that harbored gray sq u i r r e l s the year round . . . 55 14. A resting platform erected by gray sq u i r r e l s 10 -feet above the ground on the side of a large cedar - . 58 THE INTER-RELATIONS OF THE INTRODUCED GRAY SQUIRREL (SCIURUS CAROLINENSIS) WITH THE ECOLOGICAL CONDITIONS IN STANLEY PARK Introduction , The gray s q u i r r e l (Sclurus carolinensis) i s not indigenous to the P a c i f i c Northwest. However several l o c a l populations have been established and the one inhabiting Stanley Park, Vancouver, B r i t i s h Columbia, furnished the data for the present study. The primary objective of the i n v e s t i -gation was to determine the environmental factors that have limited the growth and modified the behaviour of the population. Stanley Park comprises an isthmus that protrudes from the northwest side of Vancouver.. It i s surrounded by the sea on three sides and the c i t y e f f e c t i v e l y blockades the fourth. These physical barriers have been successful in preventing the dissemination of the squirrels out of the park. F. Beebe (Pers. Comm.) and the late J . Fee (Pers. Comm.) both park employees, state that the gray s q u i r r e l was introduced into the park p r i o r to 1 9 1 4 when three or four pairs were released. These subsequently increased t i l l the early 1 9 2 0 ' s when the population approximated - the present l e v e l . The o r i g i n of the released s q u i r r e l s i s i n some doubt but i t i s generally accepted that they came from Eastern Canada. The s i m i l a r i t y of the grays inhabiting the park and those described by M i l l e r ( 1 9 2 3 ) and Anthony ( 1 9 2 8 ) for South Eastern Canada and the North Eastern United States gives credence to this theory. Taxonomic position and description . The gray s q u i r r e l i s a member of the genus Sciurus which i s found i n the family Sciuridae of the order Rodentia. Anderson (1946) in his publication - Catalogue of Canadian Recent Mammals - gives the following information about the sub-species that inhabits eastern Canada and i s established l o c a l l y at Vancouver, B. C. Sciurus flarolinensis leucotis (G-apper). 1830 S. leucotis Gapper, zool. Journ. Vol. 5, P. 206 1877 S. Carolinensls var. leucotis A l l e n , mongr. N. American.Rodentia, P. 701 (Aug..1877) 1885 S. leucotis Gapper, zool. Journ. Vol..5 , P. 206 Type l o c a l i t y - Region between York and Lake Simcoe, Ont., Canada. (Type not known.) Range - Pound-in t r a n s i t i o n zone and l o c a l l y lower edge of Canadian zone from the Alleghenies of Penn.. north through New York and New England, to southern. New Brunswick, southern Quebec and southern-Ontario -west to Manitoba. Description: The following description was gleaned from M i l l e r (1923), Anthony (1928), and Burt (1946). Larger and grayer than t y p i c a l carolinensls; apt to occur i n black or melanistic phase; 30les of feet may be hairy in the winter. Upper parts, i n winter s i l v e r ^ y gray with f a i n t wash of yellowish brown on head, back and upper surfaces of hands and feet, underparts white. Summer pelage with more rusty brown, especially along the sides. Melanistic phase; various degrees of intergrade between gray and black phases may occur. Total length 405-515 MM., t a i l vertebrae 193-250 MM., hind foot 60-75 MM. Weight"500-600 grams. This agrees with the description of the gray i n d i -viduals present in the resident population of Stanley Park. However, this colour phase i s i n the minority and It i s necessary to add a few.notes on the melanistic and i n t e r -grading portion of the population which outnumber the gray approximately 6 :1 . These range from e n t i r e l y black specimens to those with the ventral body and caudal pelage, reddish brown or brown with a d i s t i n c t although f a i n t , yellow wash.-;-.. A few melanistic individuals exhibit patches of white or g r i z z l e d h a i r s , such areas are most common.on the saddle and caudal regions. Measurements of 28 s q u i r r e l s representing a cross-section of the population produced the following ranges: Total length, 439-462 MM. T a i l vertebrae, 213-225 MM. Weight, 512-594 grams. Description of the Area From a cursory survey at the s t a r t of the i n v e s t i -gation i t was determined that the f l o r a of Stanley Park consisted i n the main iof conifers with a few discontinuous stands of deciduous and mixed deciduous-conifer woods. There-fore to enable comparisons of the d i f f e r e n t f l o r a l associations an area which had a l l types plus a healthy population of squirrels was chosen. Random >samples were taken of the trees and understorey. Different methods were used in determining the relative abundance of species of the two sections. The tree cover was measured by counting a l l trunks over 12 feet in height present in a 22 yard c i r c l e . Each: species was then expressed as a percentage of the total number of a l l species. The understorey, on the other hand, was~ tall i e d by a line intercept method and the percentage express-ion is that of the amount of ground shaded by each species. While the two methods cannot be directly compared i t is believed that the use of both give a truer representationnto the different elements of the flora. Table I. illustrates the f l o r a l composition, comprised of the more important species. Table I., shows a certain relationship of the species to one another, a different method of presentation or of collecting the data would show new relationship. For example, broad leaf maple accounts for only six per cent of the total number of trees, however, a survey on the basis of how much, shade or cover the different species produced would rate i t much higher. Thus the interpretation.of food data, availability of nests, cover, et cetera, must be made with respect to the" method of f l o r a l analysis. Originally the area was to have been presented as three f l o r a l types and although they exist as quite discreet entities in a f l o r a l sense they were a l l found to be included in the range of a single animal. Thus i t was decided to present them as a single unit bearing in 6. Table I. Showing the per cent composition of the f l o r a of the study area i n Stanley Park, B. G., May, 1950. SPECIES TREES SHRUBS % over 12' % under 12* Vine maple Acer circinatum 59.6 3 . Hazel nut COrylus c a l i f o r n i c a 13-5 • Hemlock Tsuga heterophylla 11.4 .3 Elderberry Sambuc(y<.s melanocarpa 6.3 , 1.9 Ash Sorbus aucuparia 3 . .1 Cedar .06 Thuja p l i c a t a 2 . Choke cherry Prunus emarginata 1.6 • Birch Betula papyrifera • 9 • Cascara Rhanwius purshiana .6 • Broadleaf maple Acer macrophyllum .6 • Spruce Plcea sitchenaivs .2 • Horse-chestnut Aeaculus hiopocastanu.m .1 • Willow Salix^sp. .1 F i r 4.1 PseudotsuRa t ^ x i f o l i a .1 Salmonberry 15.3 Rubus s p e c t ^ b i l i s • Huckleberry 1.8 Vaccinium parvifolium • Thimbleberry Rubus parviflorus • • 5 Foxglove D i g i t a l i s purpurea • .2 Ferns Polystichum sp. • .6 mind that the unit ia not homogenous but can be divided into its components. (Fig. 1). The coniferous portion consists in the main of second growth trees (Tsuga)A which probably are the result of logging procedures in the past. The mixed portion is believed to present the original picture of the flora for this area. The stands of maple may be explained on the basis of local edaphic conditions. Figure 3 . shows the interwoven jungle of prostrate trunks characteristic of such stands. Figure.1. Cover map of the gridded area showing the relationship between.the conifer, mixed conifer-deciduous and maple stands. May, 1950. Second growth c n n i f e r s , mainly hemlock. February, 1 9 5 1 * A stand of interwoven and p r o s t r a t e vine maple t r u n k s . Febrauary, 1 9 5 1 . Methods The area on which the study was undertaken .is a public park and a game reserve. It is utilized to a great extent by the citizens of the adjoining city of Vancouver: and partially in respect 1 of their wish to see squirrels and partially the inadvisability of upsetting the normal population i t was deemed impractical to k i l l large numbers of the squirrels for laboratory study. This necessitated an observational technique in order to collect data perti-nent to the investigation. The actual f i e l d study began in January, 1950, and until May the technique employed.to gathe facts upon squirrel biology was to follow an individual and record a l l actions, the conditions under which they took place and the time. With the coming of May the foliage increased to such an extent that i t was impossible to use successfully and another method was tried. This consisted of observing for one half hour periods from random sites the actions of squirrels seen and their distance from the observer. Goodrum (1940) in Texas and Hicks (1949) In Iowa both recommend this technique as useful in., gathering certain data. In the present study i t was possible to obtain nearly a l l the necessary information on food habits, range, inter, and intra specific relationships and reproduction. Live trapping and a few dead animals helped immeasurably in round ing out certain portions of the work. Random trapping and grid trapping were both out of the investigator's reach due to the number of,people who utilized the area and also due to the scarcity of good live traps. Therefore to gather useful data on the population . i t appeared necessary that a method of marking be employed that rendered the animals identifiable without handling. To this end most of May was spent in attempting to dye the pelage of squirrels. The following substances were tried, 'i malachite green, congo red, India ink, various analine dyes, eosin, acid fuschia, o i l paints and enamels; a l l were unsuccessful. Perhaps the main reason for their failure is the result of the property exhibited by melanin in that i t masks a l l colours. Finally 30 per cent H 20 2 was tried and i t worked very sucessfully on the black members of the population. These marked squirrels facilitated the gather-ing of data on daily and seasonal movements, reproduction, et cetera. This method of marking fi t t e d in very well with the observational technique which formed the basis of the s tudy.. Finally to enable the investigator to make a cover map and to plot various data, the area was gridded into one half acre plots. There were several reasons for choosing this, size, f i r s t , i t was the approximate area that could be watched by an observer and second, the units were not too unwieldy and could be combined with adjoining squares to give areas of desired size. Population From the outset of the investigation.^much effort was directed in trying to determine the actual population residing on the area. Census techniques that had been re-ported by Leopold (1933), Chapman (1937), Goodrum (1937), Baumgartner (1938), Allen (1942) and Fitzwater and Frank (1944) were investigated. Some of these techniques such as hunters' reports by Chapman (1937) and extensive live trapping• utilized by Baumgartner (1938) and Allen (194-2) were not •possible. The method suggested by Fitzwater and Frank (1944) which employs the use of a ratio between leaf nests and squirrels was equally impossible. Finally i t was decided to rely upon spot counts (Goodrum, 1937) and use of the Lincoln Index (Lincoln, 1930) . Data for the latter w-&& obtained by recording a l l marked squirrels seen and by a simple arithme-t i c a l calculation which utilizes the relationship that i f three numerical facts are known then the fourth can be calculated. The spot method outlined by Goodrum (1937) uses the number of squirrels observed in a definite time period on random plots of known.size. A comparison of the two methods for the period of June to August can be seen, in Tables II and III. Table II. Population calculated using the spot count. MONTH NO. OF i HR. NO. OF SQUIRRELS SQUIRRELS POP. SIZE PERIODS SEEN PER £ HR. June 71 70 .991 ' 45.6 July 71 64 .908 43.6 August 114 84 .808 38.8 The total area was 48 acres and If .991 squirrels were seen per acre per period then the population is (48 x .991) = 45.6 Table III. Population::calculated using the Lincoln. Indexv. r MONTH' MARKED MARKED UNMARKED X( UNMARKED TOTAL Ff DUCIAL ANIMALS ANIMALS ANIMALS ANIMALS POPU- LIMITS ON AREA SEEN SEEN CALCULATED) LATION PROB.95$ June 6 41 196 28.7 34.7 L x 25-0 L 2 42.8 July/ 8 30 116 30.9 38.9 L x 30.8 L 2 54.4 August 9 31 120 38.0 47.0 L x 34.6 L 2 60.0 The spot count or quadrate method is credited by Brown and Yeager (1945) to produce, theoretically, a true census. However this method has several conditions which must be met before significant results may be obtained. First a large number of counts must be made from randomly selected spots. Second, activity must be assumed to be constant the year round for comparative results. Lastly, the time period must be selected so that a l l squirrels resident on the area under inspection w i l l appear once. The poor results obtained by the use of this method suggest that at least one of these factors was not in proper operation in this area. While not producing an absolute, figure i t did present a figure by which the calculations of the Lincoln Index could be evaluated. The Lincoln.Index produced very satisfactory re-sults, especially when compared with the data on juvenile squirrels. The Increase in the population from June to August amounted to 13 individuals using the most probable figures obtained from the Index. The sex ratio determined from 4-92 observations was 293 males to 189 females or 1:.645 . When this ratio is applied to the probable June population-of 3 4 , i t is found to consist of 20 males and 14 females. From careful observations on the study area i t was known with certainty that 13 females were present, 3 of which bore no young. This is in close agreement with the calculated number. The 13 females actually present produced 16 juvenile squirrels, which figure added to the calculated population for June i n -dicates the pre-fall level should be 50 individuals. This f a l l s within the feducial limits for the population.as calcu-lated by the Lincoln Index and gives credence to i t s accuracy. The calculated density in the f a l l of .98 squirrels per acre represents a 36.1 per cent increase over the spring density of .72 squirrels per acre. '3~. Sex Ratio A total of 492 observations resulted in a sex,ratio of 1 male to .645 females. These observations were in the main, made on free animals but include some live trapped specimens. This observed summer sex ratio appears to change in the winter as a similarly derived ratio for November, December and January resulted in 39 males to 13 females, or 1 male to .333 females. This is a marked difference from the summer ratio and to explain i t several probable c a u s e s w i l l be examined.. Fir s t l y i t may be the result of some force which is acting selectively upon the females. However, the inves-tigator was unable to uncover any factor that would qualify as. such. Secondly i t may be attributed to a differential birth rate between the sexes. This hypothesis is not accept-able for the sex ratio during August and September, when the young' exerted a pronounced influence, tended toward an evening of the ratio. The third possible cause is a difference in the activity level of the sexes. This seems to be the case and two facts tend to substantiate i t . During January a period of live trapping was undertaken and resulted in the capture of 9 males and 3 females. Now this by i t s e l f could in turn be the result of an unbalanced sex.ratio. But when .taken in conjunction with facts acquired from observing • animals caged under natural weather conditions i t is suggestive of a differ-ence in activity. Three males and three females were kept during late January and February. For the i n i t i a l tem.days of confinement they were kept in a room at 70°F. and both seses were active. They were next housed in a building open to the variations of the weather and a marked difference in the activity was noted. Four of the squirrels spent nearly a l l their time in the nest boxes, emerging only to eat and drink. The other two, both males, were quite active a l l day. The four that were quiescent included the three females and one male. This male's testes had not descended fully whereas the other males'^  from the external appearance of the genitalia, evidenced signs of breeding activity. This suggests that the winter sex,ratio shows a distortion due to differences in activity between the sexes rather than a discrepancy in actual numbers. This in part may be accounted for by the fact that" adult males become sexually active earlier in the spring than do the females and immature males. Age Classes An attempt was made by live trapping to procure an age class distributionuduring late summer and f a l l . Unfortu-nately live trapping at this season is quite d i f f i c u l t due perhaps to the super-abundance of natural foods, and this course was not realized. However an analysis of the age classes can be made using the calculated number of adults in June and the known number of juveniles on the area t i l l the end of August. This shows the ratio between adults and juveniles to be 1:.47 . The winter live trapping program resulted in a ratio of adults to juveniles of 1: .71 . The winter sample was too small to be other than indicative but i t does show a substantial increase in the numbers of juveniles in the population. This can be explained in the following manner. Several l i t t e r s were born during August and the juveniles would not be noticed in the population t i l l October. Thus there is good reason to expect that the winter ratio between adults and juveniles would show a higher incidence of the latter. Condition Weight and length measurements were taken of a l l squirrels captured and form the basis for Table IV. Table IV. Presents the body weight, length of t a l l and total length of a l l squirrels handled from May, 1950 to February, 1951• A D U L T J U V E N I L E MALE FEMALE MALE FEMALE WEIGHT, GRAMS.. 594.2 562.5 -512.6 512.6 TOTAL LENGTH IN MM. 4-60.8 439.4- 448.9 462.4 TAIL LENGTH IN MM. 219.7 213.1 225-6 225.6 NO. OF INDIVID. MEASURED 14 9 3 2 The data on the adults were largely collected in June and July of 1950 whereas that pertaining to the juveniles was gathered in January, 1951 • The adults would probably be slightly heavier in the f a l l than, the weights shown in Table IV. Although the sample of juveniles Is small i t i n -dicates that they weigh less than the adults while having a similar total body length. A black male captured on June 14th weighed 1^ pounds, this individual was recaptured on August 20th and had gained one-quarter of a pound. An increase of nearly 100 per cent in body weight was exhibited by a black female between June 5 th and February 3 r d . This female weighed only l i pounds when f i r s t weighed but by the end of the following winter i t weighed 2^ pounds and was the heaviest squirrel handled during the investigation. In total length there does not appear much difference between the various age classes. This is due in part to the greater length of t a i l of the juveniles of both sexes.. Most adults in Stanley Park show some degree of t a i l cropping but Brown and Yeager (1944) state that the stub; t a i l deformity,/Is found only i n l 3 . 5 per cent of the gray squirrels in I l l i n o i s . However they do not state the degree of pruning that consti-tutes a stub t a i l . In comparing the weight of juveniles and adults as presented in Table IV. i t can be seen that the adults are definitely heavier, with the males in turn weighing more than the females. This differs from the findings of Brown and Yeager (1945) who found that both sexes weighed the same and in contrast to Baker (1944) who found that the females out-weighed the males. Pelage Colour The population, of gray squirrels harbors five basic by colour patterns . The accepted type of gray as described/^Burt (1946) and the:-melanistic individuals form-:the two opposing poles, with the other three types variously related between them. Brownish black individuals are quite common and a r e t definitely closer to the melanistic members.of the population, than the gray.. These specimens usually are black above but have the abdomen a distinct reddish brown. Another variation from the completely black type is represented by those ex.-hibiting patches of gray or white hairs, giving them a grizzled appearance. These white patches are usually asso-ciated with the caudal pelage. The last type of colour variation was seen on a large gray male who had d i s t i n c t light reddish brown areas of pelage on his abdomen,.along the lateral body wall and a distinctly reddish cast to the t a i l . It was presumed that this individual was.exhibiting a ten-dancy toward erythrism. Brown and Yeager (145) report the capture of a gray female that showed a similar condition. The gray squirrels of Stanley Park have a ratio of gray to melanistic individuals of 1 to 6.1 . The melan-i s t i c portion of the population includes the two afore-mentioned variations of melanism. No satisfactory explanation has been advanced to explain this phenomenon. Recent work by Shorter (1945)' in England advances the theory that in the gray squirrel melanism is recessive and unifactorial. The evidence does not appear too c o n v i n c i n g . In St a n l e y Park melanism does not appear to be r e c e s s i v e , however the ex-tremely s m a l l i n i t i a l p o p u l a t i o n may have b i a s e d the r a t i o of normal t o m e l a n i s t i c i n d i v i d u a l s . I t i s u s u a l l y a s s o c i a t e d with the gray s q u i r r e l i n the nor t h e r n reaches of i t s range. A l l e n (1943) r e p o r t s t h a t m e l a n i s t i c s q u i r r e l s were very abundant i n Michigan i n p r i m i t i v e times but since the p e r i o d of heavy f o r e s t c l e a r i n g and heavy hunting they have n e a r l y d i s a p p e a r e d . M i d d l e t o n (1930) working on the i n t r o d u c e d gray s q u i r r e l i n England could uncover no records of melanism. Observations made on l i t t e r s d u r i n g the present", i n v e s t i g a t i o n showed t h a t both c o l o u r phases may be present i n the same l i t t e r . . aa. Habitat Preference A cursory survey made at the beginning of the inves-tigation revealed that in pure stands of conifers gray squirrels were practically non-existent. The few grays that were in-such areas were either transients or dependent upon some ab-normal food supply such as scraps of human food, handouts or dumping grounds and thus could not be regarded as members of a normally existing population. The area on which the study was carried out consisted of three f l o r a l types. These were coniferous, mixed conifer-deciduous and nearly pure maple stands. The ranging propensities of the squirrels made i t practical to lump these divisions for the purpose of overall f l o r a l analysis, however to evaluate the use accorded to each of these types the number of squirrels seen in each during a l l one-half hour periods of observation was recorded. Figure A. gives the relationship from the point of view of use by the squirrels among the three types. It can be seen that the pure conifer stands were occupied to a much lower extent than either of the other types. Indeed the discrepancy is much less than is actually the case due to several factors giving the conifer regions an apparently higher use. The conifer stands were adjacent to areas populated by gray squirrels and in one case a coniferous stand separated an attractive nesting and den site from a rich supply of food. Therefore transient squirrels were seen amongst the conifers. The number of squirrels seen per one-half hour period Figure 4-. The use accorded by the gray squirrels to each of the f l o r a l types. A -Q -C -C O N I F E R M IXED C O N I F E R - D E C I D U O U S D E C I D U O U S ( M A P L E ) SQUIRRELS SEEN PER. ONE MR. P E R I O D F L O R A L T Y P E F I G U R E A. N U M B E R O F S Q U I R R E L S SEEN PER ONE H O U R •eBS.ERVATORV P E R I O D IN CONIFER, MIXED CONIFER— D E C I D U O U S A N O I DECI D U O U S P O R T I O N S O F T H E S T U D I E D A R E A . 1 in the mixed deciduous-conifer and maple stands indicates that both are heavily u t i l i z e d . The maple stands undoubtedly serve as primary food sources the year round but due to their lack of cover and den sites they would not support large popula-tions. The mixed deciduous-conifer habitat provides necess-it i e s other than food. These necessities are den sites, outside' leaf nest sites, cover the year round and resting sites. Probably the habitat best suited for gray squirrels would have interspersed areas of mixed forest and stands of maple positioned so that both types could be readily reached in a squirrel's daily ranging. Intra Specific Intolerance The relationship between members of the gray squirrel population is generally amicable. From extensive f i e l d observations upon squirrels on their feeding and nest-ing areas i t can be shown that they display a high level of intra specific tolerance. Groups of squirrels ranging in number from 3 to 10 have been seen foraging for food either on the ground or in vine maple trees within a radius of 20 feet without visible signs of s t r i f e . Further evidence taken from nesting areas reveals that nests may be in adjoining trees, indeed in one instance four occupied nests were in a similar number of adjoining hemlocks without s t r i f e . However there are exceptions and during the course of the f i e l d work four distinct types of intra specific intolerance were noted. The most readily noted type of intolerance evi-dences i t s e l f where several squirrels are foraging on a small area. In a l l situations of this type one squirrel makes t h e o t h e r s give way and i n a l l r e c o r d e d i n s t a n c e s the squirrel displaying this behaviour has been a male. This is undoubtedly a form of peck order however there appeared no continuation of the hierarchy beyond the dominant male and i t may be noted in a l l seasons of the year. Gorden (1936) in h is work on t e r r i t o r i a l behaviour among the Sciuridae re-ports that a peck order is established when more than.one chipmunk is foraging on one location. This appears to be e s s e n t i a l l y t h e s a m e c o n d i t i o n f o u n d i a m o n g s t t h e g r a y s q u i r -r e l s . M a l e s , o b s e r v e d c h a s i n g o t h e r m a l e s o u t o f b r o a d -l e a f m a p l e t r e e s , f u r n i s h e d t h e d a t a t o d e s c r i b e t h e s e c o n d t y p e o f i n t o l e r a n c e - . N o d e n s o r n e s t s c o u l d b e f o u n d i n t h e m a p l e s a n d a s t h e t i m e o f d e f e n c e c o i n c i d e d w i t h t h e h a r v e s t o f t h e k e y s i t s e e m s l i k e l y t h a t t h e h o s t i l i t y w a s o v e r t h i s r i c h f o o d s u p p l y . I n t o l e r a n c e o f t h i s t y p e w a s o b s e r v e d o n l y i n t h e a u t u m n . S t r i f e b e t w e e n n e s t i n g f e m a l e s c o n s t i t u t e s a n o t h e r f o r m o f i n t o l e r a n c e . T h e f i v e i n s t a n c e s o f t h i s t y p e t h a t w e r e r e c o r d e d s h o w e d t h e i n t e n s i t y o f t h e c h a s e t o b e m o s t s t r i k i n g . T h e r e i s s o m e e v i d e n c e t h a t a n e s t t r e e m a y b e p r o t e c t e d f o r a l o n g e r p e r i o d o f t i m e t h a n J u s t t h e n e s t i n g p e r i o d . T h e d a t a o n w h i c h t h i s i s b a s e d w e r e o b t a i n e d f r o m w a t c h i n g a g r a y f e m a l e c h a s e a m a r k e d , b l a c k f e m a l e f r o m t h e s a m e d e n t r e e i n M a y , A u g u s t a n d D e c e m b e r . . . T h e l a s t d a t e c o u l d s c a r c e l y r e p r e s e n t a p r o t e c t i o n o f y o u n g . T h e l a s t f o r m o f i n t r a s p e c i f i c i n t o l e r a n c e w a s n o t e d d u r i n g A u g u s t a n d t h e b e g i n n i n g o f S e p t e m b e r . T h r e e c h a s e s t o o k p l a c e d u r i n g t h i s t i m e t h a t i n v o l v e d a d u l t s a n d j u v e n i l e s . I n o n e c a s e t h e s e x o f t h e a d u l t w a s k n o w n t o b e a f e m a l e . T h e i n t o l e r a n c e d i s p l a y e d b y m a l e s p r o t e c t i n g a f o o d t r e e a n d t h e f e m a l e s p r o t e c t i n g a d e n t r e e s e e m c l a s s i -f i a b l e a s t e r r i t o r i a l i t y w h i l e t h e l a s t f o r m h i n t s a t a m o d e o f d i s p e r s a l o f t h e y o u n g . T e r r i t o r i a l behaviour i s presumed to be exhibited when an in d i v i d u a l defends an area from others of the same population (Burt, 1940). The size of the t e r r i t o r y defended by gray s q u i r r e l s i s very small and i n a l l observed cases was confined to a single tree. The defense of a nest tree as d i s t i n c t from a den tree, i s confined to the period of rearing the young. A den tree as cited previously, may be protected the year round. The defense of a p a r t i c u l a r l y abundant and desired food source may be c l a s s i f i e d as seasonal t e r r i t o r i a l i t y . Behaviour of this type does not appear deeply rooted as i t was only seen on two occasions.in the f a l l while during the same period many observations were made of two or more sq u i r r e l s harvesting broadleaf maple keys from the same tree. The significance of the fourth type of intolerance can be better appreciated when ..it i s coupled with the know-ledge that at this time of the year the s q u i r r e l populationn i s at a maximum. The r e s u l t i n g i r r i t a b i l i t y expresses i t -s e l f i n quite savage chases by adults of the juveniles. These pursuits undoubtedly help i n the dispersal of the young from the immediate v i c i n i t y of occupied trees. Spatial Relationships The spatial relationship between the gray squirrel and its environment is very complex. To present the data as clearly as possible an attempt was made to divide i t into three aspects, daily movements, seasonal movements and home range. Undoubtedly the treatment of each w i l l be found to overlap the others, as in reality the last two, seasonal movements and. .home range are the composite results of daily movements. Squirrels live in a three dimensional world; i t has length, width and depth. The f i r s t two are familiar to ter-re s t i a l species but the third is alien. It is a product of the arboreal habit of squirrels. In this cuboid environment they must carry out a l l the v i t a l processes of l i f e . To do so i t is necessary to exploit the environment in regard to food, water, nest sites, cover, et cetera. To be exploited successfully these elements of the environment must be within certain spatial limits, an individual attempting to exist in a region where these boundaries are overstepped is at a dis-advantage (Errington, 1 9 4 6 ) . Several techniques were employed to gather the necessary information. Two methods, live trapping and sight records of marked, animals as suggested by Burt (1940) supplied the information on seasonal movement and home range. Follow-ing certain individuals of the population furnished the data pertaining to daily movements.- To expedite the evaluation.. of seasonal movements and home range, a l l observations and cap-tives were plotted on a grid of the studied area. The move-ments of three females and three males are shown in Figures 5, 6, 7, 8, 9 and 10. Figure 5 . Movements .cf a female squirrel from May, 1 9 5 0 to January, 1 9 5 1 . 3o. MAV M JUNE .'\ JULY 0 AUGUST P. SEPTEMBER S OCTOBER r JANUARY X «1 A S C A L E 1 I N C H = 4 0 0 F E E T A Figure 6 . Movements of a female squirrel from June, 1 9 5 0 to January, 1 9 5 1 . MAY ISA JUNE A JULY O AUGUST R SEPTEMBER S OCTOBER r JANUARY X S C A L E 1 I N C H = 4 0 0 F E E T Figure 7. Movements of a female s q u i r r e l during June, July, 1950. 3*. M A V ISA J U N E A J U L Y A U G U S T R S E P T E M B E R S O C T O B E R r J A N U A R Y X 5CALE 1 I N C H = 4- OO F E E T F i g u r e 8. Movements of a male s q u i r r e l from May to September, 1950. MAY M JUNE A JULY 0 AUGUST R S E P T E M B E R S O C T O B E R r J A N U A R Y X fir SCALE 1 INCH = 4-00 F E E T Figure 9. Movements of a male squirrel from June to August, 1950. MAV J U N E J U L Y AUGUST S E P T E M B E R . OCTOBER JANUARY N\ R S r x o o SCALE 1 I N C H = A OO F E E T g u r e 1 0 . M o v e m e n t s o f a m a l e s q u i r r e l f r o m J u n e t o A u g u s t , 1 9 5 0 . MAY JUNE JULY AUGUST SEPTEMBER OCTOBER JANUARY A 0 P. S r x S C A L E 1 I N C H = 4 0 0 F E E T Dally Movements The extent of the d a i l y movements depend upon i n t r i n s i c factors such as sex and age, and e x t r i n s i c factors such as weather, season, food and shelter. These two basic--: types of factors w i l l be discussed as separately as possible and some of t h e i r components w i l l be treated b r i e f l y . No attempt w i l l be made here to interpolate the a c t i v i t y periods as they are presented elsewhere. Table V. Distances traversed by marked male and female squ i r r e l s i n a single day's a c t i v i t i e s . F E WINTER A L E REMAINDER M A L E WINTER REMAINDER OF YEAR OF YEAR 600 feet 500 feet 400 feet 2000 feet 500 600 ti 1000 1600 " 1000 550 II 1100 1100 " 1000 1200 tt 1200 1200 " 950 1100 tt 800 1300 " 1200 1200 it 400 1000 " 500 400 it 550 1200 " 800 400 ti 1000 " 1000 1000 it 1200 " 700 tt 2000 " 839 feet 765 feet 771 feet 1360 feet AVERAGE I n t r i n s i c factors seem to determine the extent of the d a i l y wanderings. Table V. shows adult males move through g r e a t e r d i s t a n c e s than a d u l t females. A male on June 9 t h was observed to move a t l e a s t a d i s t a n c e of 2000 f e e t i n one and one-half hours. The maximum recorded movement of an a d u l t female was 1200 f e e t . J u v e n i l e s were never noted more than 300 f e e t from the nest up t i l l t h e i r time of d i s p e r s a l . Fe-males d u r i n g the p e r i o d of r a i s i n g t h e i r young appeared to have approximately the same r a d i u s of d a i l y a c t i v i t y as u t i l i z e d the r e s t of the ye a r . Perhaps i t i s the minimum th a t can supply a l l the needs of an i n d i v i d u a l . While the area u t i l i z e d - i s f a i r l y constant, the p o r t i o n s emphasized v a r i e s with the p h e n o l o g i c a l season. T h i s b r i n g s up the p a r t played by the e x t r i n s i c f a c t o r s . E x t r i n s i c f e a t u r e s appear to govern the degree of d a i l y movements. The d i f f e r e n c e i n seasonal food alone r e -quire s t h a t the p a t t e r n of d a i l y l i f e be changed from season to season. In w i n t e r there are p l a c e s where vine and broad-l e a f maple keys are b u r i e d and s q u i r r e l s congregate here to fo r a g e . These areas are much more r e s t r i c t e d i n s i z e than those which produce these foods d u r i n g the summer and f a l l . Weather can i n f l u e n c e the d a i l y a c t i v i t y of gray s q u i r r e l s markedly and e f f e c t s of t h i s nature are d i s c u s s e d elsewhere. In summary i t appears t h a t males move through.greater d i s t a n c e s than females or j u v e n i l e s d u r i n g the course of a s i n g l e day's wandering. F u r t h e r , many e x t e r n a l f e a t u r e s were noted t h a t could modify these d a i l y r a n g i n g a c t i v i t i e s . Seasonal Movements No migration or seasonal movement in i t s f u l l e s t implication was observed during this study. However the da i l y movements., of the gray, s q u i r r e l changed according to the time of the year and thus seasonal trends were noted. While the range of females did not a l t e r appreciably the amount of time spent i n the d i f f e r e n t portions did change thus accentuating the use of these regions. The males exhibited a d i f f e r e n t i a l size i n home range between the late f a l l and early winter with the remainder of the year. This i s discussed under home range. Factors that caused the changes were usually related to the taking of food. For example. During the summer when vine maple keys are eaten the squirrels tend to congregate in the vine maple groves, however i n the winter they group around certain broadleaf maple trees. A further example that empha-sizes also that the s q u i r r e l h a b i t a l i s three dimensional is observed in the increased amount of time they spend foraging for food on the ground during winter. Home Range Before presenting this aspect of the investigation i t i s necessary to define several terms« to ensure c l a r i t y . In this paper "home range" means the area an animal traverses i n the normal a c t i v i t i e s of food gathering, mating, caring for the young and other acts necessary for a successful l i v e l i h o o d . Wandering either by vagrants or individuals searching for home sit e s i s excluded. The term " t e r r i t o r i a l i s m " i s reserved for the act whereby an in d i v i d u a l of a population exhibits defence of some area from others of the same population, f o r some species of animals the two terms, home range and t e r r i t o r i a l i s m , may be synonymous but for the gray s q u i r r e l there exists a marked difference. T e r r i t o r i a l i t y i s d i s -cussed under the broader heading of i n t r a s p e c i f i c intolerance so only home range w i l l be considered i n this section. The plot on which the study was carried out has an area s l i g h t l y i n excess of 50 acres and supported a population of approximately 45 gray s q u i r r e l s . Thus i t appears that there i s nearly one s q u i r r e l per acre. This supposition i s erroneous on two accounts. F i r s t , the amount of habitat suitable to the grays i s considerably less than 50 acres. Second, the areas that are suitable are not always available to them. It can be appreciated therefore the gray s q u i r r e l population on the regions u t i l i z e d has a density considerably above one per acre. There are two ways i n which the habitat for gray s q u i r r e l home range could be divided up. It could consist of a series of discrete home ranges or the home ranges can overlap each other. A glance at Figures 5 , 6 , 7 , 8 , 9 and 10, reveals that the l a t t e r condition prevails. This implies that the bulk of gray s q u i r r e l habita^ i s common ground and is therefore used by the population or some portion of i t . . Burt (1940) working on small mammals i n Michigan found that the size of the home ranges of the sexes may d i f f e r a p p r e c i a b l y . T h i s appears t o be the case w i t h the gray s q u i r r e l . I t i s d i f f i c u l t , however, t o f i n d a sound b a s i s on which t o compare the r e l a t i v e areas of home ran g e s . The methods used by B u r t (op. c i t . ) and Hayne (1949) do n o t appear a p p l i c a b l e t o the d a t a g a t h e r e d d u r i n g t h i s s t u d y . The P o i s s o n theorem of c o n t a g i o u s d i s t r i b u t i o n = . w a s a p p l i e d and i t shows s t a t i s t i c a l l y t h a t b o t h males and females move i n t h e i r r e s p e c t i v e ranges i n a non random manner. Caution.! must be e x e r c i s e d i n a p p l y i n g such s t a t i s t i c a l t r e a t m e n t as the r e s u l t s , o b t a i n e d can o f t e n be m i s l e a d i n g due t o s a m p l i n g . In a n a l y s i s of home range by the P o i s s o n theorem i t i s n e c e s -s a r y t o have a l a r g e number of r e c o r d s t o p l o t and the t o t a l a r e a used i n the c a l c u l a t i o n must be c a r e f u l l y chosen. The f i r s t p r e r e q u i s i t e was n o t f u l l y r e a l i z e d i n t h i s i n v e s t i g a t i o n and thus the r e s u l t s o b t a i n e d are p o s s i b l y b i a s e d . As has been a l r e a d y s t a t e d , the range of a female i s s u b s t a n t i a l l y the:,same thr o u g h o u t the y e a r but w i t h the v a r i o u s p o r t i o n s r e c e i v i n g s p e c i a l a t t e n t i o n a c c o r d i n g t o the s e a s o n . F i g u r e s 5. and 6. r e v e a l t h a t t h e r e were no r e c o r d e d e x c u r s i o n s by the females out of the s p r i n g and summer range d u r i n g the remainder of the y e a r . The males p r e s e n t a d i f f e r e n t p a t t e r n . F i g u r e s 8, 9, and 10, show t h a t from May t o September they ranged through a much l a r g e r a r e a t h a n d i d the f e m a l e s . The range of the males from October t o January i s i n some doubt a l t h o u g h the meager i n f o r m a t i o n : : a v a i l a b l e i n d i c a t e s t h a t t h e i r range i s c o n s i d e r a b l y l e s s t h a n d u r i n g the remainder of the y e a r and approximates that of the females. In comparing the home ranges of the two sexes.it appears that the areas u t i l i z e d are si m i l a r during the late f a l l and early winter but d i f f e r markedly the" remainder of the year due to the wider ranging of the males. The females are able to l i v e successfully on th e i r smaller range and thus., i t must be adequate i n respect to the basic b i o l o g i c neces-s i t i e s of an i n d i v i d u a l . This would suggest that the increased range of the males i s the r e s u l t of some factor not not d i r e c t l y concerned with making a l i v i n g . The period of increased range agrees i n the main with the period of sexual a c t i v i t y and the period of decreased range with the period of sexual i n a c t i v i t y . The increased a c t i v i t y brought about by sexual maturity i s offered as a tentative explanation for the increased range of the males. An examination of the methods used to give absolute values such as number of acres or square yards to the home range of an in d i v i d u a l revealed that they are subject to error introduced by each investigator's interpretation of the data. Thus the writer f e e l s that u n t i l a r e l i a b l e method i s brought forth a l l that can be said of the gray s q u i r r e l home range i s that the males move i n a non random manner over at least 50 • to 55 acres and that the females move i n a simi l a r fashion through an area i n the order of 5 to 15 acres. A c t i v i t y A n i m a l a c t i v i t y c y c l e s o n a 2 4 h o u r b a s i s h a v e s t i m u l a t e d , m a n y r e c e n t r e s e a r c h e s . T h i s p h a s e o f t h e p r e s e n t -s t u d y a t t e m p t s t o f i n d t h e d a i l y p a t t e r n o f a c t i v i t y o f t h e g r a y s q u i r r e l a n d . t o e v a l u a t e c e r t a i n e n v i r o n m e n t a l f a c t o r s t h a t c o n d i t i o n i t . T h e e x a c t t i m e w a s n o t e d f o r e a c h i n d i v i d u a l s e e n a n d w h e n t h e s e n u m e r o u s o b s e r v a t i o n s w e r e r e d u c e d t o t h e c o m m o n d e n o m i n a t o r , s q u i r r e l s s e e n p e r h o u r , a r e l a t i v e i n d e x o f a c t i v i t y w a s o b t a i n e d . M e t e r o l o g i c a l r e c o r d s w e r e k e p t o n w i n d v e l o c i t y , c l o u d s , t e m p e r a t u r e , p r e c i p i t a t i o n a n d r e l a t i v e h u m i d i t y . U n f o r t u n a t e l y t h e r e c o r d s f o r t e m p e r a t u r e a n d r e l a t i v e h u m i d i t y w e r e t a k e n e a c h d a y b e t w e e n 1 2 A . M . a n d . 1 P . M . T h u s o n l y o b s e r v a t i o n s f r o m 1 0 A . M . t o 3 P . M . w e r e d e e m e d t a k e n u n d e r s u f f i c i e n t l y s i m i l a r c o n d i t i o n s t o w a r r a n t i n c l u s i o n . T h e p e r i o d 1 0 A . M . t o 3 P . M . i s s h o w n b y F i g u r e 1 1 . t o b e a p e r i o d o f l o w e r e d a c t i v i t y a n d t h i s h a s p e r h a p s b i a s e d t h e r e s u l t s . T i m e o f D a y T h e e f f e c t t h e t i m e o f d a y e x e r t s u p o n s q u i r r e l a c t i v i t y i s g i v e n i n F i g u r e 1 1 . f o r e a c h o f t h e f o u r s e a s o n s . T h e s e a s o n s a r e d i v i d e d o n t h e p h e n o l o g i c a l b a s i s s e t f o r t h i n t h e i n t r o d u c t i o n t o f o o d h a b i t s . D u r i n g t h e w i n t e r s e a s o n t h e i n i t i a l a c t i v i t y p e r i o d i s 7 A . M . t o 8 A . M . T h e n c o m e s Figure 11. Relationship between time of day and s q u i r r e l a c t i v i t y . ^3 SQUIRRELS SEEN P E R HOUR 10 T 5" O IOT W I N T E R O I O T S P R I N G 1 1 o «o-5-o • SUMMER 1 I I—r— F A L L 3 = E A 5 S 7 8 9 A . IV1. IO i l 1 2 2 3 A 5 6 P . fvl. 7 8 I T I M E O F D A V P. S.T. F I S U R E I I. an hour or two of lowered a c t i v i t y a f t e r which i t gradually builds up t i l l the d a i l y maximum i s reached between 4 P.M. and 5 P.M. The graph for spring a c t i v i t y indicates that the squirrels begin to move about shortly a f t e r 6 A.M. The i n i t i a l peak which i s also the d a i l y maximum occurs at 9 A.M. a f t e r which there ensues a gradual tapering off t i l l a low i s reached at 2 : 3 0 P.M. A c t i v i t y increases in the afternoon and the zenith i s noted between. 4 P.M. and 5 P.M. The da i l y cycle f o r the summer reveals that the grays begin to move from 4 A.M. to 5 A.M. with the greatest d a i l y and seasonal a c t i v i t y between 5 A.M. and 6 A.M. There follows a rapid drop i n . s q u i r r e l movements t i l l approximately 9 : 3 0 A.M. when a s l i g h t increase i a noted. This quickly f a l l s away and a quiescent period i s observed t i l l the late afternoon when from 3 P.M. to 4 P.M. another peak a r i s e s . F i n a l a c t i v i t i e s for the day cease shortly after 7 P.M. The autumn presents e s s e n t i a l l y the same plan of two main periods of a c t i v i t y separated by a r e l a t i v e l y quiet interim. The f i r s t signs of a c t i v i t y are realized between 6 A.M. and 7 A.M. with the primary peak i n . the succeeding hour. An inactive interlude follows that extends up to 2 P.M. when a gradual r i s e takes place, resulting in the secondary d a i l y peak reaching prominence between.4 P.M. and 5 P.M. This l e v e l of a c t i v i t y i s held to 7 P.M. after which i t dissipates r a p i d l y . It appears from the facts gleaned from Figure li>. that the period of highest a c t i v i t y occurs shortly a f t e r sun-ri s e in a l l seasons except winter. Following t h i s there i s a tendency toward a general lowering,of a c t i v i t y , this decline las t s approximately one hour and i n i t i a t e s a lengthy period of lethargy. During the late afternoon or early evening, dependent upon the season, the secondary period of d a i l y animation begins. It extends to shortly before sunset at which time the gray s q u i r r e l s end t h e i r d a i l y cycle. Undoubtedly each season presents certain refinements to this basic scheme. For example. The greatest a c t i v i t y during the winter i s recorded for the afternoon. This i s perhaps i n response to i t being the warmest part of the day and also related to the length of time that the squirrels must be without food during the winter nights. The available data i s not s u f f i c i e n t to delve into this aspect other than in this cursory manner. However the basic pattern: of d a i l y a c t i v i t y i s assumed to be f a i r l y well substantiated and i n the ensuing sections some environmental factors that can modify this pattern w i l l be discussed. These environmental factors are components of what i s generally termed weather. Each of these components, temperature, humidity, wind, degree of overcast and p r e c i p i -tation, with the exception of the l a s t two i s treated separate^ Temperature Observations were taken at temperatures ranging from 46°F. to 80°F. and Table VI. presents the relationship of the number of s q u i r r e l s seen per one-half hour period with the temperature. Table VI. The relationship between temperature and number of squirrels seen per period of observation. SQUIRRELS PER £,.H0UR PERIOD TOTAL NO. TEMPERATURE (10 A.M. TO 3 P.M.) OF PERIODS o F > JUNE JULY AUGUST SEPTEMBER 6 46-50 .7 13 51-55 .8 ' 1 .0 11 56-60 1 .6 1.0 .3 .7 14 61-65 1 .0 .5 30 66-70 1.0 1.2 1.0 0 .0 11 71-75 0 .0 .8 • 3 The monthly temperatures which show the greatest a c t i v i t y present quite a uniform pattern. In June a c t i v i t y was at i t s maximum be twe en:56°F. and 60°F ., f o r July and August the range 66°F. to 70°F. fostered the most animation. Too few observations were recorded i n September to be other than i n d i c a t i v e , although i t appears that at temperatures of 51°F. to 55°F. they are most active. Humidity The r e l a t i v e humidity i n Stanley Park i s exceedingly high and during the study i t never f e l l below 50 per cent. The range of humidities under which observations were taken was 51 per cent to 95 per cent. However the bulk of the records were obtained between 66 and 85 per cent, (Table VII.) humidities l y i n g outside this range are represented so infrequently that they could not be u t i l i z e d . Due to the very narrow range the data f o r the three months are lumped. Table VII.The relationship between number of squirrels seen per observatory period and the r e l a t i v e humidity from July to September, 1950. RELATIVE HUMIDITY NO. OF SQUIRRELS NO. OF OBSERVATION PER i HOUR PERIOD PERIODS 51-55 1.0 2 56-60 0 61-65 .2 4 66-70 .7 14 71-75 1.0 28 76-80 •8 38 81-85 .7 24 86-90 0 91-95 1.0 1 The greatest degree of gray s q u i r r e l a c t i v i t y i s centred about the range of 71 to 75 per cent. The a c t i v i t y f a l l s o f f as the humidity changes from this apparent optimum. Wind The wind v e l o c i t i e s recorded were with few excep-tions under ten miles per hour. A i r movements of this magnitude have a n e g l i g i b l e e f f e c t upon masses of standing vegetation and for t h i s reason the modifying a b i l i t y of the wind upon the d a i l y a c t i v i t y cycle i s not known for certain. On two occasions however, gray sq u i r r e l s were observed t r a v e l l i n g through the tree tops while a wind storm was in progress. Both s q u i r r e l s gave the investigator the impression that they were excited and unsure of themselves. They re-peatedly .ran out to the ends of branches three or four times before jumping to the next tree. A l l t h e i r movements were quick and hurried while a l o f t yet when they descended to a lower l e v e l where the e f f e c t of the wind was scarcely notice-able they exhibited complete confidence i n leaping from one branch to another. Hicks (1949) investigating the e f f e c t of a i r mass movement upon fo x . s q u i r r e l a c t i v i t y found that i t was in inverse proportion. The data obtained i n this inves-t l g a t i o n . i s too meager to corroborate this statement. Baker (1944) reports that i n Texas high wind v e l o c i t i e s decrease s q u i r r e l a c t i v i t y . Overcast and Eee'cipitation The l a s t environmental factor that may modify s q u i r r e l a c t i v i t y i s degree of overcast including p r e c i p i t a -t i o n . The data on which Table VIII. i s based was obtained from recording the number of squirrels seen along a d e f i n i t e route. This route was covered at a l l times of the day and in every season so i t establishes a better survey than i f the writer had just u t i l i z e d the observation periods between 10 A.M. and 3 P.M. The purpose of this section i s to present the relationship that exists between a c t i v i t y and degree of overcast and p^rgcipitatlon. To this end i t was deemed per-missable to lump the seasonal data and Table VIII. gives the average number of s q u i r r e l s seen per t r i p under three sets of a r b i t r a r i l y decided conditions. These are; clear and bright i n which cloudiness i s less than 5/10; cloudy with the sky 5/10 to 10/10 overcast and p r e c i p i t a t i n g which includes varying degrees of r a i n and snow. Table VIII. The relat i o n s h i p between s q u i r r e l a c t i v i t y and degree of overcast and p r e c i p i t a t i o n . CLEAR AND BRIGHT CLOUDY P3SCIPITATING TIME "OF AVGE. NO. NO. AVGE. NO. NO. AVGE. NO. NO. DAY- SQUIRRELS TRIPS SQUIRRELS TRIPS SQUIRRELS TRIPS SEEN SEEN SEEN 5-7 A-.M. 6.6 37 5 . 8 10 1.0 4 7-9 A.M. 3.3 6 1.2 5 1.3 3 9-31 A\M. 1.9 8 2.0 9 1.0 3 11-1 1.6 10 3.0 5 4.5 2 1-3 P.M. 0 .7 2 0 .7 3 3-5 P.M. 0 .9 8 2.3 3 5-7 P-.M. 2.6 3 Clear bright days foster the greatest amount of a c t i v i t y , however overcast conditions are assoicated with only a s l i g h t lowering of a c t i v i t y . Pre'cipitation d e f i n i t e l y lowers the movement of the s q u i r r e l s . The period 1 1 A . M . to 1 P . M . i s an exception to this statement but" can be explained by noting the very small number of observations made at this time coupled with the fact that they were made in a s l i g h t d r i z z l e which did not deter the squirrels to any degree. While these various factors that can influence s q u i r r e l a c t i v i t y were presented separately the writer be-lieves the correct interpretation must be done c o l l e c t i v e l y . The interaction of these factors may reinforce or detract from one another so that the e f f e c t upon s q u i r r e l a c t i v i t y cannot be attributed to any Isolated cause. Food supply and conditions associated with breeding a c t i v i t y may cause act i v i t y that w i l l mask the e f f e c t s of the weather. F i n a l l y , and this i s a major c r i t i c i s m of this aspect of the investigation, i t is necessary to have accurate readings from the microclimate at d i f f e r e n t a l t i t u d i n a l levels to evaluate properly the relationship that exists between weather and s q u i r r e l a c t i v i t y . Nesting In the present study two basic types of nests, the outside leaf nest and the den were observed to be u t i l i z e d . In addition a t h i r d method of receiving protection from the weather conditions was noted, this i s the rest i n g platform, which can be seen i n Figure 14. The use of nests in Stanley Park d i f f e r s somewhat from that presented by Fitzwater and Frank (1944) and Brown and Yeager (1945). The three types of nests w i l l be discussed separately so fa r as i t i s feasible and an attempt made to explain t h e i r position r e l a t i v e to the l i f e history of the gray s q u i r r e l . Leaf Nests Outside leaf nests are occupied most extensively from A p r i l to October. While some are used the year round, den trees appear to offer the greatest sanctuary i n the cold wet months of the year. Due to the abundance of suitable den s i t e s and the fac t that outside nests may be used for several years they could not be u t i l i z e d as a census method. The use of many outside leaf nests as permanent residence d i f f e r s from th e i r use i n Connecticut where Fitzwater and Frank (1944) report that outside nests are u t i l i z e d for short periods. During the f i e l d work only 18 outside nests were discovered on the test p l o t . Comparing this with the 45 gray squirrels present on the area i t i s realized that the majority of s q u i r r e l s inhabit den trees. It can be deduced that outside leaf nests are not the preferred type and are b u i l t only when suitable den s i t e s are lacking. The outside leaf nests tend to be congregated in clumps of hemlock. Such clumps supply excellent cover and protection the year round and seem to be admirably suited' for nest s i t e s . Table IX. presents the number of nests found i n Stanley Park, the tree species that they were b u i l t i n and other data such as average height of nest and B. f v H5. °f nest trees. Table IX. Heights of leaf nests and diameters of nest trees by species. SPECIES NO. AVERAGE . AVERAGE fo OF % TREE NESTS HT. NESTS 3 .B .H. NESTS SP. IN OF TREES FLORA Hemlock Tsuga heterophylla 20 36 feet 18 inches 77.0 11.4 Cedar Thuja plicatav 4 55 1 1 35 " 15.4 2.0 Spruce Picea sitchensis 1 60 " 11 " ^3.8 .2 F i r Pseudotsuga t a x i f o l i a 1 55 " 10. 5 " 3 .8 .1 An analysis of the data presented i n Table IX. shows the western hemlock furnishes most of the nest sites,-another conifer, the western red cedar, furnishes the next' greatest number. Together these two species provide over 70 per cent of the nesting s i t e s although they represent only 13.4 per cent of the f l o r a . This preference for evergreen species agrees with the work of Fitzwater and Frank (1944) i n Connecticut. Further considerations of Table IX. show that in general, mature trees are preferred but the table does not give the s p a t i a l r e l a t i o n s h i p of the nests to each other nor the i r position r e l a t i v e to the f l o r a . I t can be said that i n general the nests are i n trees that are adjacent and form small groves. These stands are scattered throughout the mixed deciduous-conifer areas of the h a b i t a l but those most heavily u t i l i z e d are proximal to areas of vine and broadleaf maple stands. During August, the month of greatest a c t i v i t y in.j nest building, six gray sq u i r r e l s were observed to build leaf nests. The s p a t i a l position of the tree u t i l i z e d has been dealt with i n the previous section so the description -/will begin with the selection of the s i t e which the mest w i l l occupy i n the tree. A l l of the 26 nests observed were b u i l t i n one of the following three positions; at the top of a tree, adjacent to the trunk where a limb protrudes or at some distance from the trunk on a main .branch. The favoured s i t e s seem to be •-'.ad j a cent to the trunk and some distance along a main branch; few were found at the top of trees. Figure 12. shows an outside leaf nest constructed i n the crown of a hemlock. This nest was used from May to October. Fitzwater and Frank (1944) reporting on the leaf nests of gray sq u i r r e l s i n Connecticut found that the crown and junction of a main branch with the trunk were the pre-ferred s i t e s with few nests found on l a t e r a l branches. Figure 12. An outside nest constructed on the crown of a hemlock. S0. A c t u a l c o n s t r u c t i o n o f a n e s t t a k e s s u r p r i s i n g l y l i t t l e t i m e . O n J u l y 1 2 t h a b l a c k w a s o b s e r v e d b u i l d i n g a t 1 0 : 3 0 A.M. a n d a t 1 1 : 4 1 A.M. t h e n e s t a p p e a r e d t o b e f i n i s h e d e x c e p t f o r t h e a d d i t i o n o f m a t e r i a l s t o l i n e t h e i n n e r c a v i t y T h e m a t e r i a l s u s e d i n b u i l d i n g g e n e r a l l y c o m e f r o m t h e n e s t t r e e . T h e n e s t s e x a m i n e d s h o w e d t h a t T s u g a a n d T h u j a t w i g s a n d n e e d l e s w e r e u s e d i n a l l c a s e s , t h e a m o u n t o f e a c h d e p e n d i n g d i r e c t l y o n t h e t r e e s p e c i e s i n w h i c h t h e n e s t w a s s i t u a t e d . T h e e x t e r i o r o f t h e n e s t i s c o m p o s e d . o f i n t e r w o v e n t w i g s o f T h u j a o r T s u g a a n d b a r k o f t h e f o r m e r . T h i s m a t r i x , i s o f t e n 5 - 6 i n c h e s t h i c k a n d a p p e a r s t o b e w a t e r p r o o f f o r t w o n e s t s o p e n e d a f t e r p r o l o n g e d r a i n s s h o w e d t h e i n t e r i o r t o b e a b s o l u t e l y d r y . T h e l i n i n g o f t h e c a v i t y v a r i e d a g r e a t d e a l a n d t h e f o l l o w i n g m a t e r i a l s w e r e u s e d , v i n e a n d b r o a d l e a f m a p l e l e a v e s , s h r e d d e d c e d a r b a r k a n d h e m l o c k n e e d l e s . D i m e n s i o n s t a k e n f r o m s e v e r a l n e s t s a n d a v e r a g e d g a v e t h e l e n g t h a s 1 6 i n c h e s , w i d t h o f 1 4 i n c h e s a n d a d e p t h o f 9 . 5 i n c h e s . D e n T r e e s I n S t a n l e y P a r k t h e r e i s a n a l m o s t u n l i m i t e d s u p p l y o f t r e e s w i t h s u i t a b l e d e n s i t e s . T h i s c o n d i t i o n i s d u e t o t h e a b u n d a n c e o f l a r g e c e d a r s ( T h u j a p l i c a t a ) w h i c h h a v e a t e n d e n c y t o b e c o m e h o l l o w a n d d e v e l o p s p l i t s w i t h m a t u r i t y . ( F i g u r e 1 3 . ) T h e g r a y s q u i r r e l s h a v e r e s p o n d e d t o t h i s b y u t i l i z i n g a l l s u c h t r e e s t h a t a r e n o t o c c u p i e d b y . t h e D o u g l a s \ Figure 13. A large cedar den tree on the study.. area that harbored gray squirrels the year round. s q u i r r e l (Tamiasciurus d o u g l a s i i ) . These den trees are u t i l i z e d the year round and this i n part i s the reason that so few outside leaf nests are present. These large cedars are d i s t r i b u t e d on the area i n such a manner that i t i s d i f f i c u l t to get more than .100 yards from one. This wide-spread d i s t r i b u t i o n of potential den s i t e s has enabled the gray s q u i r r e l to u t i l i z e den trees by preference instead of a v a i l a b i l i t y . This means that a s q u i r r e l can u t i l i z e a preferred area and not be obliged to erect an outside nest. A l l e n (194-2) and Brown and Yeager (194-5) state that an environment to achieve the maximum expression of i t s s q u i r r e l potential must have a suitable supply of den trees. The area on which the present study was carried out more than amply meets th i s condition. Resting Platform Several times while examining the f l o r a of the region small platforms were observed on the sides of cedars and atop b r o k e n stumps. A c l o s e r e x a m i n a t i o n ^ r e v e a l e d the presence of black and gray hairs which indicated that these small hideouts ;were used by gray s q u i r r e l s . The retreats examined have a l l been within 8-15 feet of the ground. They are so placed that eit h e r the trunk or some .other object protects the occupant from the prevailing wind and r a i n . Those that are on the sides of cedars (see Figure 14.) u t i l i z e seams i n the trunk. The seam i s b u i l t up with cedar bark u n t i l a p l a t f o r m i s f o r m e d t h a t i s h i g h e r a t t h e o u t s i d e t h a n a t t h e b a c k . A s q u i r r e l p r e s e n t i n o n e o f t h e s e p l a t f o r m s i s n e a r l y i n v i s i b l e a n d r e c e i v e s e x c e e d i n g l y g o o d p r o t e c t i o n f r o m t h e e l e m e n t s . A b l a c k f e m a l e w a s f l u s h e d f r o m o n e d u r i n g a s e v e r e D e c e m b e r r a i n a n d w i n d s t o r m . S h e g a v e n o a p p e a r a n c e o f b e i n g w e t a l t h o u g h s h e h a d b e e n . i n t h e h i d e o u t f o r a t l e a s t 25 m i n u t e s . I t a p p e a r s t h a t s q u i r r e l s u s e t h e m a s r e s t -i n g p l a t f o r m s t h r o u g h o u t t h e y e a r ; n o e v i d e n c e w a s f o u n d t o i n d i c a t e t h a t f o o d w a s t a k e n t h e r e a n d d e v o u r e d . T h e y f u r n i s h p r o t e c t i o n f r o m t h e w e a t h e r a n d d u e t o t h e i r p o s i t i o n i n g r e n d e r s u r p r i s e f r o m p r e d a t o r s u n l i k e l y . r Figure 1 4 . A resting platform erected by gray squirrels 1 0 feet above the ground on the side of a large cedar. Predation While Stanley Park has been isolated by physical barriers for at least 50 years i t harbors both resident and transient predators. The resident predators are mink (Mustelgf vison), screech owl (Otus a s i o ) , and f e r a l dogs and cats. The transient predators observed were the goshawk (Astur  a t r l c a p i l l u a ) , specimens of which were seen on three occasions and the great horned owl (Bubo virg i n i a n u s) . While the afore-mentioned species are a l l possible predators only the cat and screech owl are known to have k i l l e d gray s q u i r r e l s . The remains of fiv e gray s q u i r r e l s were found throughout the year of f i e l d work, two had been k i l l e d by automobiles, while cats, screech owls, and an unknown agency each accounted f o r one. Thus out of the known loss of fiv e s q u i r r e l s , i t s e l f a low .figure, only two could be d e f i n i t e l y attributed to predators. This i s a low incidence of predation upon a population and i t suggests that prey-predator relationships are not d i r e c t l y responsible i n l i m i t i n g the population l e v e l of the gray s q u i r r e l i n Stanley Park. Parasites L i t t l e opportunity was afforded for detailed para-s i t o l o g i c ^ data to be coll e c t e d . An attempt was made to gather a l i s t of external parasites and this data i s presented in the remainder of the section. Most of the sq u i r r e l s examined were found to be a f f l i c t e d with the mange mite Sarcoptes sp. This ectoparasite has been reported by Brown and Yeager ( 1 9 4 5 ) as occurring on the gray s q u i r r e l i n I l l i n o i s . The areas of the body usually attacked are the ears, back of the neck and the t a i l . Ticks (^Ixodes augustus) were commonly found on the squirrels from A p r i l to October with multiple infections usual. Two species of fleas were also taken and proved to be Orchopeus nepos and Hystrichopsylla spinata. Reproduction/; The presentation of data pertaining to reproduction i s broken up into two main subdivisions - each of which w i l l be presented more or less separately. The f i r s t , on a chronological basis i s generally termed breeding and represents the course of events from premating up to the time of advanced pregnancy. The second phase extends from the time of b i r t h t i l l the young are weaned and leave the female. The bulk of the data on which this portion, of the l i f e history of the s q u i r r e l i s based was derived d i r e c t l y ; from f i e l d observations, supplemented by the examination of 33 l i v e trapped individuals representing a cross-section of the populations Breeding Season.. The work of many investigators has shown the gray s q u i r r e l to be dioestrus (Deanesby and Park, 1933); A l l e n , 1943; Brown and Yeager, 1945). In the present study two females were d e f i n i t e l y known to have two l i t t e r s , this adds substantiation to the work of the other investigators.. Males were observed pursuing females i n a l l months except September, October and November. It appears that be-tween September and November the males are quiescent. This i s substantiated by the examination of the external g e n i t a l i a . From September to the end of November the testes are not f u l l y descended and a large furrow runs across the scrotum l o n g i -t u d i n a l l y , these features are i n marked contrast to the scrot a l s a c a n d t e s t e s o f a s e x u a l l y a c t i v e m a l e . B a k e r ( 1 9 4 4 ) s t u d y i n g g r a y s q u i r r e l s i n T e x a s f o u n d e v i d e n c e o f w h a t h e t e r m s " r u t " i n m a l e s t h r o u g h o u t t h e y e a r . B r o w n a n d Y e a g e r (1945) w o r k i n g i n I l l i n o i s b e l i e v e t h a t a p e r i o d o f n o n -b r e e d i n g e x i s t s i n m a l e s a n d l a s t s f r o m A u g u s t t o N o v e m b e r . W h i l e i t i s b e l i e v e d , a s a r e s u l t o f f i e l d d a ' t a a l o n e , t h a t m a l e s m a y b e s e x u a l l y a c t i v e f r o m D e c e m b e r t o t h e f o l l o w i n g A u g u s t t h e f e m a l e s p r e s e n t a m u c h d i f f e r e n t p i c t u r e . S u c c e s s f u l c o p u l a t i o n w a s f i r s t n o t e d o n t h e 8 t h o f A p r i l , h o w e v e r t h e i n v e s t i g a t o r s u s p e c t s t h a t t h i s i s a p p r o x i m a t e l y t h e e n d o f t h e f i r s t • o e s t r u s c y c l e . I n s u p p o r t o f t h i s b e l i e f t h e f o l l o w i n g d a t a i>s. p r e s e n t e d . Y o u n g j u v e -n i l e s r e p r e s e n t i n g e i g h t l i t t e r s m a d e t h e i r a p p e a r a n c e b e t w e e n J u n e 9 t h a n d J u l y 6 t h . T h e y o u n g g e n e r a l l y m a k e t h e i r a p p e a r -a n c e s e v e n t o n i n e w e e k s a f t e r b i r t h ( A l l e n , 1943; B r o w n a n d Y e a g e r , 1945) a n d i f a g e s t a t i o n p e r i o d o f 44 d a y s ( B u r t , 1946) i s a d d e d o n e c a n w o r k b a c k f o r a t o t a l o f 1 4 w e e k s f r o m b o t h d a t e s a n d f i n d t h e i n i t i a l m a t i n g p e r i o d e x t e n d i n g f r o m M a r c h 3rd t o A p r i l 8 t h . T h i s I s q u i t e a r o u g h m e t h o d a s t h e a g e s a t w h i c h e a c h l i t t e r w a s f i r s t s e e n . w a s u n d o u b t e d l y d i f f e r e n t b u t i t d o e s s h o w t h a t a p e r i o d o f m a t i n g t a k e s p l a c e i n M a r c h . D u r i n g t h e p e r i o d J u n e 15 t o J u l y 18, s i x m a t i n g s w e r e o b s e r v e ! i n t h e f i e l d . T h i s p e r i o d : i s t a k e n t o b e c o i n c i d e n t w i t h t h e s e c o n d o e s t r u s c y c l e . F e m a l e s m a t i n g i n t h a t p e r i o d w o u l d b e e x p e c t e d t o b e a r y o u n g b e t w e e n t h e l a s t f e w d a y s o f J u l y a n d t h e e n d o f A u g u s t . T h i s s e e m s b o r n e o u t a s A u g u s t h a s t h e s e c o n d l a r g e s t n u m b e r o f l a c t a t i n g f e m a l e s o b s e r v e d , o n l y J u n e p r o d u c i n g m o r e . F r o m a c o m p a r i s o n o f t h e t i m e b e t w e e n t h e t w o p e r i o d s o f b r e e d i n g . a c t i v i t y , w i t h t i m e f r o m c o n c e p t i o n t o w e a n i n g i t c a n b e s e e n t h a t i f a f e m a l e i s g o i n g t o b e a r t w o l i t t e r s s h e m u s t b e b r e d a t t h e b e g i n n i n g o f t h e f i r s t p e r i o d t o b e r e c e p t i v e b y t h e m i d d l e o f t h e s e c o n d . T h e c a s e h i s t o r y o f a f e m a l e t h a t h a d t w o l i t t e r s b e a r s t h i s o u t . W h e n f i r s t e x a m i n e d o n M a y 30th t h e m a m m a r y d e v e l o p m e n t o f t h i s f e m a l e g a v e e v i d e n c e o f s u c k l i n g . O n J u n e 19th t h e n e s t w a s f o u n d a n d b y t h i s t i m e t h e t w o j u v e n i l e s w e r e a b l e t o l e a v e t h e n e s t t r e e . T h e y w e r e a b l e t o e a t v i n e m a p l e k e y s b u t w e r e o b s e r v e d t o s u c k l e t h e f e m a l e . B y h e r a c t i o n s o f t r y i n g t o k e e p a w a y f r o m t h e y o u n g i t i s t h o u g h t t h a t t h e y w e r e b e i n g w e a n e d - i n d e e d t h e y w e r e s e e n t o s u c k l e o n c e o n l y . O n A u g u s t 31st, a f t e r a p e r i o d o f o n e m o n t h d u r i n g w h i c h s h e w a s n o t s e e n , t h o u g h a t h o r o u g h s e a r c h w a s m a d e , s h e a p p e a r e d w i t h d e f i n i t e s i g n s o f h a v i n g y o u n g . A p p a r e n t l y s h e m a t e d s u c c e s s -f u l l y d u r i n g t h e f i r s t w e e k o f M a r c h a n d a g a i n i n e a r l y J u l y . W o r k i n o t h e r a r e a s h a s s h o w n t h a t o n l y a d u l t f e m a l e s b r e e d t w i c e i n a y e a r ( D e a n e s l y a n d P a r k s , 1933; B r o w n a n d Y e a g e r , 1945). T h e s p r i n g j u v e n i l e s b r e e d o n c e t h e f o l l o w i n g y e a r , m a t i n g i n t h e J a n u a r y - F e b r u a r y o e s t r u s c y c l e , t h e f a l l a n d l a t e s u m m e r j u v e n i l e s b r e e d o n l y i n t h e J u n e - J u l y o e s t r u s c y c l e . A l t h o u g h t h e n u m b e r o f s q u i r r e l s i n t h e p r e s e n t i n v e s -t i g a t i o n w a s l i m i t e d t h e c a s e h i s t o r i e s o f t w o i n d i v i d u a l s , o n e f r o m e a c h j u v e n i l e a g e c l a s s , t e n d t o s h o w t h a t a s i m i l a r c o n d i t i o n e x i s t s . Mating chase The most obvious c h a r a c t e r i s t i c of the breeding seasons i n gray sq u i r r e l s i s the mating chase. Observors watching 6 to 1 0 males chasing a female are so often impressed by the physical properties of the episode that they neglect to interpret them on a b i o l o g i c a l basis. In order to discuss t h i s subject f u l l y a composite mating derived from six actual chases w i l l be presented i n chronological sequence. B i o l o g i c a l interpretations w i l l be attempted throughout the description. It appears that the female i n her d a i l y wanderings leaves signs that can be recognized by the males and usually one to three days before a female i s i n oestrus they follow her and attempt to copulate. A l l attempts at c o i t i o n are evaded by the female. This period can be s i g n i f i e d as the pre-courtship period and as: .mentioned, lasts one to three days; The next phase, i s the actual courtship and i t can be measured in hours rather than days. The data are not 1>ee» complete but apparently the female begins to c a l l and i s soon surrounded by several males. When several males are present she stops c a l l i n g and the dominant male begins to c a l l unceasingly. The dominance shown by this male i s of a physical order. The subordinate males are scattered about and from time to time one attempts to wrest the dominance from male-No. 1 . This can be designated as the courtship period and l a s t s one to two hours. This i s a very important time as the probable mate for the female i s selected from the attendant males and the time period i s long enough to attr a c t mos;t of the males on the immediate area. A s i t u a t i o n such as this would seemingly produce a male that had physical dominance over a l l others of the area and thus he would mate a l l the available females. However, there were at least three d i f f e r e n t No. 1 males i n the six matings observed and the area i n which they occurred could be readily reached by a l l three. I t seems that some other factor operates In determining the successful mate besides physical dominance. At t h i s time the female, who has moved very l i t t l e i n the preceding hours, begins to run about the trees and across the ground at a very fas t rate. The No. 1 male i s right behind her and the other males are strung out behind. A l l the males are emitting low grunts, inaudible at distances greater than 10-15 feet. Males that are close follow by eye and those that lag, t r a i l by scent. The No. 1 male figh t s o f f a l l intruders. F i n a l l y the No. 1. male siezes the female copulates f o r 30 to 60 seconds. A quiescent period for the female ensues a f t e r several successful matings but the No. 1 male mounts guard and fends off the excited subordinates. From the preceding description several general considerations may be drawn; f i r s t the gray s q u i r r e l i s promiscuous, second a courtship period exists during which the probable mate i s decided on a physical basis and t h i r d , the wider ranging of the males appears linked with t h e i r l o c a l concentrations about a receptive female. Development of the Young From the breeding data pertaining to mating in the previous section i t can be calculated that the bulk of the l i t t e r s are born i n the two periods April' 1 5 to June 12 and July 29 to August 3 0 . The size of the l i t t e r s was determined by observa-tions on the young as they began;to emerge from the nest. Thus Table X. represents not a true l i t t e r size but the number of young that the females raised to the age of weaning. I t i s expected that the l i t t e r size would be larger and indeed the determining of l i t t e r size through examination of placental scars showed that i t averaged three. Due to the small sample used i n a r r i v i n g at t h i s figure (only three adult females were autopsied) i t can only be taken as indicative of l i t t e r s ize. Work by Goodwin (1937) and Brown and Yeager (194-5) show that the average l i t t e r size for the gray s q u i r r e l i s between.2.5 and 3 young. In Stanley Park the r a t i o between:breeding female and young at weaning time i s 1 to 1.6 . This shows a marked reduction from the expected l i t t e r size at b i r t h . The losses seem to occur between the period of b i r t h to weaning time. Table X. Number of weaned young per breeding female on study area. NUMBER OF SIZE OF SIZE OF TOTAL NUMBER FEMALES 1ST LITTER 2ND LITTER OF YOUNG 1 2 Lost young 2 2 2 4 6 1 6 TOTAL 10 16 Food In this investigation a study based on detailed laboratory analysis of stomach contents was impossible. How-ever throughout the year, of f i e l d work a l l facts that would give an index to s q u i r r e l foods were noted. These included . opened keys under maples, husked involucres around hazel nut trees, fungi with the septa eaten and cuttings of various kinds. This type of data gives only a quotative record.and in an attempt to make this aspect of the study as quantitative as possible a technique outlined by Cowan ( 1 9 4 7 ) was u t i l i z e d . Every time a s q u i r r e l was observed eating,the food i t was i d e n t i f i e d and the exact time spent eating, noted. Undoubtedly there are several major objections to this method, fo r instance the worker must be f a m i l i a r with the f l o r a , the time spent eating d i f f e r e n t foods i s not always i n d i r e c t proportion, with the amount of food taken and i t i s more d i f f i c u l t to see squirrels while they are foraging for some items thus giving an impression of lowered consumption. It has favorable aspects also. Squirrels i n this region appear to eat only during daylight hours and as a rule a meal i s made up pr i n -c i p a l l y of one or two food items. I t would be expected that: d i f f e r e n t foods would be eaten with varying speeds yet f i e l d observations do not confirm t h i s . Indeed i t appeared that the time necessary for a gray s q u i r r e l to eat i t s f i l l of most staple foods was quite constant and varied with the i n d i v i d u a l s q u i r r e l more than the food item. With due recog-nition.,of i t s f a i l i n g s this method i s a useful t o o l and while not giving absolute results i t does show the quantitative relationship between food items. A portion of the s q u i r r e l population under study received part of its d i e t by begging from park v i s i t o r s . An e f f o r t was made to evaluate the relationship of this unnatural food i n terms of s u r v i v a l and necessity. There are a few. sq u i r r e l s that appear t o t a l l y dependent upon a r t i f i c i a l feed-ing; on the other hand there are gray squirrels i n Stanley Park that rarely come in contact with humans and are completely divorced from any unnatural food supply. On the gridded area approximately one-third of the squirrels foraged f o r a r t i f i c i a l food to some extent. Whether i t was of necessity, preference or a v a i l a b i l i t y w i l l be subsequently decided.. The separation of the yearly d i e t of squirrels into elements was phenologically based. This method gives a more natural grouping of foods than d i v i d i n g the year on the basis of the calendar seasons. Table XI. presents the four pheno-l o g i c a l seasons and the c r i t e r i a for t h e i r separation. Table XI. Gives four phenological seasons and th e i r c r i t e r i a . SEASON LENGTH CRITERIA FOR DEMARCATION IN WEEKS WINTER, 18-19 end of October t i l l March 20. SPRING, 9-10 March 20 t i l l June 1. After a l l the leaves and most crops off the trees t i l l the squirrels begin to eat buds i n the spring. Period of u t i l i z a t i o n of buds and new. shoots t i l l f i r s t most crop eaten. SUMMER, 10-12 June 1 t i l l August 23. FALL, 10-11 August 23 t i l l end of October. Period of utilization.of most crops without storing. Period when most crop i s stored and lasts t i l l leaves and most crop o f f the deciduous trees. Tables XII, XIII, XIV and XV present a summary of the food items taken i n animal minutes during the spring, summer, f a l l and winter respectively. Table XII. Foods eaten i n the Spring, 1950, expressed in animal-minutes. NATURAL FOOD ITEMS PARTS EATEN ANIMAL-MINUTES % OF FOOD Vine maple buds, flowers 469 52.2 Acer clrcinatum samaras 2 .2 Oak buds 185 20.7 Quereus sp. acorn 4 .4 Horse chestnut buds 34 3.6 Aescuius hlppocastum Weeping willow buds 14 1.6 Salix babylonica Elm buds 15 1.7 Ulmus sp. Broadleaf maple buds 17 1.9 Acer macrophyllum samaras 1 .2 Dogwood buds 10 1.1 Gornus N u t t a l l i f r u i t s 4 .4 Salmonberry buds, shoots 9 1.0 Rubus spectablis Bone 7 .8 Hazel nut leaves, petals 7 .8 Corylus c a l i f o r n i c a Miscellaneous 2.2 TOTAL 88.8 UNNATURAL FOOD ITEMS Peanuts 85•5 9V6 Ice cream wrappers 10 1.1 Cabbage stems 3 «3 Bread 2 .2 TOTAL 11.2 Table XIII. Foods eaten i n the Summer, 1950, expressed in animal-minutes. NATURAL FOOD ITEMS Vine maple Acer circinatum Broadleaf maple Acer macrophyllum PARTS EATEN ANIMAL-MINUTES % OF FOOD Hazel nut Corylus c a l i f o r n i c a f r u i t s Choke cherry f r u i t Prunus emarglnata flowers, leaves and petals samaras leaves samaras leaves, twigs Hemlock Tsuga heterophylla Salmonberry Rubus spectablis new shoots leaves berries Fungi septa Huckleberry f r u i t Vaccinium parvlfolium UNNATURAL FOOD ITEMS Bread Orange Peanuts Ice cream wrapper 633.0 598 .0 1 8 . 5 431-5 169.0 32.5 23 .0 10.5 9 . 5 2.5 7 .0 7 .0 TOTAL 2 8 . 0 11.5 10.5 6 . 0 TOTAL 32 .4 29.8 .9 21.4 8 .4 1.6 1.1 • 5 .4 .1 • 3 .3 97.2 1.4 .6 . 5 .3 2.8 Table XIV. Foods eaten i n the Autumn, 1950. expressed i n animal-minutes. NATURAL FOOD ITEMS Vine maple. Acer circinatum Broadleaf maple Acer macrophyllum Dogwood Cormus n u t t a l l i Alder Alnus rubra Horse chestnut Aescuius hippocastum Mountain ash Sorbus aucuparla UNNATURAL FOOD ITEMS Peanuts PARTS EATEN samaras samaras f r u i t s cones f r u i t f r u i t ANIMAL-MINUTES % OF FOOD 65.2 376.5 168.5 20.0 6.0 ' 4.0 1.0 TOTAL 1.0 TOTAL 29.2 3.5 1.0 .7 .2 99.8 .2 .2 7* Table XV. Foods eaten i n the Winters of 1950, 1951, expressed i n animal-minutes. NATURAL FOOD ITEMS Broadleaf maple Acer macrophyHum Pine Pinus resinosa Vine maple Acer circinatum Hawthorn Cratageous sp . Alder Alnus rubra Oak Quereus sp. Horse chestnut Aesculus hippocastum Dogwood Cornus n u t t a l l i Grass Gramineae Miscellaneous UNNATURAL FOOD ITEMS Peanuts PARTS EATEN ANIMAL-MINUTES % OF FOOD samaras seeds samaras f r u i t cones acorn f r u i t f r u i t roots 5 3 2 . 5 110.0 1 7 . 5 11.0 3 . 0 2 . 5 1.0 1.0 . 5 16.0 TOTAL 64.6 13.3 2.1 1.3 .4 .3 .1 .1 131 TOTAL 1.9 8 4 . 1 15-9 15.9 In a study of the food habits of most animals i t w i l l be found that a basic framework of staple food items e x i s t s . These whether by a v a i l a b i l i t y o>r preference form the main portion of the diet.. There exists another important type of food which may or may not be a staple food, these items are u t i l i z e d under adverse conditions and can be cata-logued as emergency rations. In this study the staple and emergency items were found to be the same, on thi s framework of staple foods others of lesser importanceaare to be found. Some of them furnish elements to the d i e t that are probably v i t a l l y necessary for continued health. Under this heading come seasonal abundant items, chance a r t i c l e s , unnatural foods and certain little-known and less understood herbs. With th i s cursory sketch of what.'.'is found i n the general d i e t of an animal the writer w i l l proceed to a d i s -cussion of the d i e t of the gray s q u i r r e l . Seasonal Foods An examination of Tables XII, XIII, XIV, and XV, reveals that the palate of the gray s q u i r r e l i s varied and they probably partake of foods that have not been recorded. For example. Many workers (Seton, 1928; Middleton, 1930; Hamilton, 1943) on the Scituridae have found that during the late spring and summer they consume a considerable quantity of animal food such as insect larvae, eggs, young birds and mammals. It i s believed that the gray s q u i r r e l i n Stanley Park also partakes of animal food but throughout-the study-not one instance was recorded. Spring Throughout the spring period there i s an increasing food supply f o r s q u i r r e l s . It i s characterized by a heavy use of buds, flowers and young shoots of a variety of plant species. Vine maple i s the source of most food items of this kindc-and i s much more u t i l i z e d than the broadleaf maple. This difference i s i n part due to sampling technique as the period i n which broadleaf maples were most readily taken was also a period of few f i e l d observations.. The broadleaf maple buds swell and burst before the vine maple which underwent its., heaviest u t i l i z t i o n dn May. The genus Quereus i s represented by only a few large specimens i n the area but i t furnished' approximately 20 per cent of the spring food. While no general conclusion can be drawn i t appears that Quereus has a high preference r a t i n g . Several large trees d a i l y attracted fiv e to seven sq u i r r e l s which often fed simultaneously.. Summer Summer i s a period of food abundance and the emphasis s h i f t s from buds and other vegetative parts to the various ripening f r u i t s . It i s considered properto men.tion.Aat t h i s point that the large percentageof vine maple vegetationr.con-sumed may represent a portion of animal matter. Many types o f i n s e c t s w e r e p r e s e n t o n t h e v i n e m a p l e l e a v e s a n d t h e a c t i o n o f s e v e r a l s q u i r r e l s i n l o o k i n g a t t h e d o r s a l s i d e o f a l e a f b e f o r e e a t i n g r e n d e r s i t a d i s t / i n c t p o s s i b i l i t y t h a t c e r t a i n l a r v a l f o r m s w e r e b e i n g t a k e n . G o o d r u m ( 1 9 4 0 ) f o u n d t h a t i n T e x a s o v e r 3 « 5 p e r c e n t o f t h e f o o d o f g r a y s q u i r r e l s c o n s i s t e d o f i n s e c t s , m a i n l y l e p i d o p t e r o u s l a r v a e . H a m i l t o n . ( 1 9 4 3 ) r e c o r d s g r a y s w i t h t h e e a t i n g o f c a t e r p i l l a r s . F a l l T h e n u m b e r o f a v a i l a b l e f o o d s b e c o m e s p r o g r e s s i v e l y ' l e s s a s a u t u m n a d v a n c e s . T h e s a m a r a s o f t h e t w o s p e c i e s o f m a p l e b e g i n t o p l a y a m o r e i m p o r t a n t r o l e i n i ' t h e d i e t . F r u i t o f t h e d o g w o o d ( C o r n u s n u t t a l l i ) , a l d e r ( A l n u s r u b r a ) a n d c h e s t n u t ( A e s c u i u s s p . ) a r e a l l e a g e r l y s o u g h t . T h r o u g h o u t t h i s p e r i o d m u c h f o o d i s s t o r e d f o r l a t e r c o n s u m p t i o n . W i n t e r W i n t e r i s a c r u c i a l t i m e f o r t h e g r a y s q u i r r e l p o p u l a t i o n ; i t i s a t i m e o f f o o d s c a r c i t y a n d i t i n i t i a t e s t h e b e g i n n i n g o f t h e f i r s t b r e e d i n g s e a s o n . T h e m o s t a v a i l a b D e f o o d s a r e t h e s a m a r a s o f t h e v i n e , a n d b r o a d l e a f m a p l e s . T h e s e f r u i t s a r e i n p a r t b u r i e d b y t h e s q u i r r e l s i n t h e f a l l a n d p a r t t h e r e s u l t o f n a t u r a l d i s s e m i n a t i o n w h i c h b e c o m e c o v e r e d u p b y f a l l i n g l e a v e s . N e a r l y e v e r y f o o d i t e m e a t e n d u r i n g t h i s p e r i o d ' . . h a s b e e n s t o r e d . T h e s i n g l e m a j o r e x c e p t i o n i s . t h e c o n e s o f P i n u s r e s i n o s a • T h i s i s n o t a n a t i v e s p e c i e s but has been planted on the area. That gray s q u i r r e l s w i l l u t i l i z e pine cones suggests the p o s s i b i l i t y that i f native pines were present they would be u t i l i z e d . Food Succession The year round di e t has been discussed under the various seasons i n s u f f i c i e n t d e t a i l to warrant no more than a mention.for food succession. The sequence of s q u i r r e l foods may be abrupt or a gradual t r a n s i t i o n . Several example of both were observed during the f i e l d work. Squirrels were feeding heavily upon vine maple vege tative parts up t i l l June 1st, within two days broadleaf maple keys had supplanted the vine maple. Sim i l a r l y gray squirrels began.foraging for Quereus sp. buds on May 10th and for the next ten mornings the oaks were heavily fed upon. An example of gradual change of food items evidenced i t s e l f when the s q u i r r e l winter d i e t of maple keys changed to buds of various species of plantsi-as they began to swell and unfold. Storing of Food Gray sq u i r r e l s were noted storing surplus food in. every month of the year. However natural foods were cached only from late August u n t i l the end of October. Caching was f i r s t noticed on August 2 3 r d during the late afternoon when a large black under observation was-seen to make four t r i p s t o the ground, each time w i t h t h r e e o r f o u r v i n e maple samaras i n i t s mouth. I n between each t r i p i t a t e a few keys . A l l keys were b u r i e d s e p a r a t e l y and w i t h i n . . t h i r t y f e e t of the t r e e . Many o b s e r v a t i o n s were .made on s q u i r r e l s engaged i n s t o r i n g f o o d and s e v e r a l g e n e r a l i t i e s have r e s u l t e d . . 1. The c a c h i n g appears t o oecea outgrowth o f the l a t e a f t e r -noon f e e d i n g p e r i o d . 2. The items s t o r e d a re b u r i e d s e p a r a t e l y and a p p a r e n t l y a t random. 3. The items are u s u a l l y h i d d e n w i t h i n a r a d i u s of f i f t y f e e t from t h e i r s o u r c e . The problem of how s q u i r r e l s r e - l o c a t e b u r l e d food s e v e r a l months a f t e r c a c h i n g has i n t e r e s t e d many i n v e s t i g a t o r s ( D i c e , 1927; Cahalane, 1942). The r e s u l t s have i n d i c a t e d t h a t memory s e r v e s t o l o c a t e the a r e a i n whi c h the n u t s are b u r i e d w h i l e the sense of s m e l l l o c a t e s the i n d i v i d u a l n u t . These c o n c l u s i o n s have been v e r i f i e d i n the p r e s e n t study as s q u i r r e l s do n o t s e a r c h a t random over the whole a r e a but con-gregate i n l o c a l s p o t s where keys and n u t s have been s t o r e d . S q u i r r e l s were i- r e p e a t e d l y watched w h i l e they t r a v e l l e d d i s -t ances up t o 3 0 0 y a r d s d i r e c t l y t o a c h o i c e f o r a g i n g s p o t . However once t h e r e , t h e i r a c t i v i t i e s become random i n n a t u r e . Cahalane '(1942) r e p o r t s t h a t m o i s t ground enhances the po s s -i b i l i t y of r e c o v e r y of cached f o o d s . I n S t a n l e y P a r k the ground, i s always, m o i s t and thus r e c o v e r y s h o u l d be f a c i l i t a t e d . A l l foods are n o t b u r i e d a t random around the f r u i t -i n g t r e e . On s e v e r a l o c c a s i o n s gray s q u i r r e l s s t o r i n g maple samaras have chanced on an acorn or hickory nut, these were taken out of the immediate vicinity and apparently were stored in a specific place. By way of a rough experiment to test this selection, two squirrels were given peanuts, these were a l l stored within twenty-five feet of the investigator. When these same squirrels were given hazel nuts they carried out a different procedure. The nuts were inspected and i f sound they were taken a considerable distance away and buried. A l l hazel nuts received were buried at the same place although many other similar spots were much closer. It is not possible to draw any definite conclusions from so few observations but i t would appear that memory would be necessary in re-locating stores of nuts stored in such instances. Minerals No study is known that l i s t s the mineral requirement of the ScdUridae. Carlson (1940) and Coventry (1940) mention that both gray and fox squirrels eat bone. In the present study one adult female 'was seen on May 12th to gnaw on a piece of bone for seven minutes. Y/hen the squirrel was finished the bone was carefully hidden under some leases. An examination irevealed that i t was part of a vertebra and had been gnawed considerably. The bone was replaced but two days later i t was gone. Water Squirrels were observed drinking water from pools in a l l seasons of the year. On one occasion after a short but violent summer shower a black was seen to lick the ventral surfaces of vine maple leaves. Other sources of water are probably dew and succulent fruits. Brown and Yeager (194-5) believe that water is a necessity in the habitat of gray squirrels. This was impossible to test f : ; v in Stanley Park due to the super-abundant supply of available water. Human Interference There would be l i t t l e to gain.from this inquiry i f $>he population was not self-supporting. At the onset of the investigation i t was thought that the population was partially dependent upon supplemental feeding. This was not borne out by the field data pertaining to food. An analysis of Tables XII, XIII, XIV and XV reveals that the portion of the diet supplied by humans to the gray squirrel varied from 15.8 per cent in the winter to .2 per cent in the f a l l . Winter is the only season in which auxiliary feeding of this type could exert a marked influence due to the; abundance of available foods during the other three seasons. Some squirrels are definitely dependent upon the public for their daily food requirements. Opposed to these there exist groups of squiriels that are practically isolated from human contact . These l a t t e r s q u i r r e l s r e c e i v e no unnatural foods and y e t they are able to s u r v i v e the w i n t e r . I t appears t h a t the gray s q u i r r e l can e x i s t on the n a t i v e food supply and the u n n a t u r a l supple-ment to the d i e t i s f o r reasons of a v a i l a b i l i t y or preference not n e c e s s i t y . Relationship with the Douglas Squirrel Some animals show a marked territorial.behaviour, the native Douglas squirrel (TamxscMrus douglasii) being one. Knowledge of this characteristic behaviour is necessary to understand the relationship that exists between them and the gray squirrel. Throughout the course of the study some data w*& collected relative to the biology of the Douglas squirrel. From this information data were screened that indicates the Douglas squirrel defends territory for three basic reasons. Firstly i t protects food caches. The defense of this site is undertaken on a year round basis. Secondly i t defends an area about the nest tree from nestbbuilding t i l l the young leave in late summer. The third; and last type of territor-ialism observed is exhibited in the protection of some seasonal food source. This latter type is year round but shifts with the food supply. Thus i t is seen that each Douglas squirrel has a territory in which the defence of certain, boundaries is emphasized throughout the year., The Douglas squirrel on an individual basis is the dominant species and:', is capable of making the gray squirrel give way. It would be expected then that they would be the dominant squirrel species. However this is not the case i f density of individuals is used as the criterion of dominance. The explanation, of why the gray squirrel is able to be more abundant in the face of strong intra specific intolerance from a physically stronger species rests on several facts.. The f i r s t reason i s the studied area i s not the best Douglas s q u i r r e l habitat. This was!indicated by obser-vations that showed the density of Douglas squirrels on nearly pure stands of conifers exceeded that found on mixed deciduous groves.. Secondly the gridded plots general u n s u i t a b i l i t y to Douglas sq u i r r e l s resulted i n t h e i r t e r r i t o r i e s being confined to the coniferous tracts and the adjoining edges. Thus the t e r r i t o r i e s presented a spotty rather than contiguous d i s t r i b u t i o n . From these facts and the knowledge of the Douglas squ i r r e l ' s t e r r i t o r i a l behaviour i t can.be appreciated that on a large portion of the investigated region no c o n f l i c t exists as the Douglas:-squirrel i s either permanently or seasonally absent. Nevertheless c o n f l i c t exists on the t e r r i -tory of the Douglas s q u i r r e l s . It i s not so severe, however that i t excludes grays from at least a p a r t i a l u t i l i z a t i o n of these areas. The native species does not defend the t e r r i t o r y with equal enthusiasm and often the defended portion has l i t t l e a t t r a c t i o n to the grays. The gray*, while recognizing the physical supremacy of the Douglas s q u i r r e l i s not the least backward in trespassing. Observations made in the f i e l d lead the investigator to conclude that the defended t e r r i t o r y has d e f i n i t e boundaries which both species recognize, for in the pursuit of a gray by a Douglas s q u i r r e l i t i s often the gray that stops f i r s t . The Douglas cannot constantly patrol its territory and so grays s i f t onto the portions that attract them and i f driven out come hack at the f i r s t opportunity. It appears that the territories of the Douglas squirrel are not inviolate. The facts represented in this section indicate that in this type of habitat the Douglas squirrel is not acting as a major influence in limiting the gray squirrel population. Relationship with Aves The relationship between nesting birds and gray s q u i r r e l s has been commented on by many inve.stigators . Anthony (1928) believes that the eggs and young of birds are taken during the late spring and early summer d i e t . Middleton (1931) working i n England comments that while they w i l l eat eggs and young t h e i r depredations had l i t t l e e f f e c t upon the nesting success of the passeriforms. In an attempt to appraise the relationship that exists between nesting birds and the gray s q u i r r e l i n Stanley Park twenty-six nests representing seven species were found and t h e i r history recorded. Table XVI presents the numerical data r e l a t i n g to nesting success while Table XVII gives the breakdown of nest losses. Table XVI. The nesting success of seven species of birds in Stanley Park from May to July, 1 9 5 0 . BIRD SPECIES NO. OF NESTS NO. SUCCESSFUL Mallard - 3 3 Anas platyrhynchos Kingbird 1 1 Tyrannus v e r t i c a l l s Creeper . 1 1 Certhia f a m i l i a r i s F l i c k e r 1 1 Colaptes cafer Willow grouse 3 3 Bonasa umbellus Robin 11 6 Turdus mlgratorius Olive-backed thrush 6 3 Hylocichla ustulata TOTAL 26 18 Table XVII. The mode of nest destruction in Stanley-Park and the bird species concerned from.: May to July, 1950. AGENCY OF LOSS NO. LOST BIRD SPECIES AFFECTED Gray squirrels 2 robin and olive-backed thrush Humans 2 robin and olive-backed thrush Douglas squirrels 1 robin Other birds 1 olive-backed thrush Unknown 2 robin The 26 nests under observation suffered a total loss of eight or 31*8 per cent. However gray squirrels could be blamed for destroying only two nests or 7«7 per cent. The sample is probably too small to provide definite conclusions but i t does indicate that gray squirrel predation.is not a serious factor in limiting; ..nesting success under the existing conditions*. Squirrels apparently have a l i k i n g for animal food of this type and i t is surprising that more nests were not raided. The following is offered by way of partial ex-planation. On several occasions birds ./were able to rear broods adjacent to trees that housed female squirrels and. young. How; were they able to do so? The study was too short to investigate this aspect other than be observation periods. However certain ideas present themselves and-.while they can-not be proven they do indicate future lines of attack. It is usually accepted that many species of animals may inhabit the same local region and yet not compete or con-f l i c t with each other due to their different ecological requirements. The squirrels are living in the same sphere as the birds but at different levels and intensities. The gray, squirrel and each of the bird species exhibit marked prefer-ences toward certain combinations of environmental factors. For example. Squirrels do not move at random from a region : of good cover to a feeding spot, they move-- along a path which seems to have certain characteristics which are discernable to them. In watching squirrels move the investigator was struck with the frequency a route was used by different indi-viduals to reach a common destination. If a bird species was attracted to the same set of physical factors and built nests along this route i t seems likely that i t would be more liable to chance discovery and thus predation. In an actual example, a pair of kingbirds built a nest and raised a brood on the edge of a clearing that was heavily utilized by gray squirrels as a feeding and resting ground and a travel route. Gray squirrels were often observed only a few feet away yet the brood was successfully raised. The answer to the question "why was i t not discovered?" appears to l i e in the micro-habitat in which the nest was placed. It was, built at the extreme end of a low branch of a cedar tree. Throughout the study not a single observation was; .made of a squirrel in a like position. From consideration of f i e l d observations i t appears that gray squirrels find bird nests by chance. Thus any group of physical conditions that tends to concentrate on squirrels and bird nests on any area would increase the possibility of a nest being found. From this line of reason ing i t follows that only birds nesting where squirrels habit ually frequent w i l l be destroyed. There was l i t t l e evidence of purposeful search for bird nests by the squirrels.. Modifying Effect of the Environment When an exotic species is introduced i t must establish a delicate balance with the animate and inanimate elements of its new environment. The effect may be two-fold in that both the exotic and the environment may be modified by this new relationship. This section attempts to analyze some of the habits of the gray squirrel in Stanley Park in comparison to those exhibited in its native range. Food The foods eaten by the gray in the Eastern:United States are not available in great quantity in Stanley Park. Therefore i t was necessary for the local population to adjust, to certain native sources of food. These foods would be expected to differ from those taken in areas where the gray is indigenous. Table XVIII. presents certain foods of each area and their relation to the diet of the squirrels. The portion pertaining to the native range was drawn largely from Brown and Yeager ( 1 9 4 5 ) . Table XVIII*. A comparison o f the food items of the gray s q u i r r e l i n i t s n a t i v e range w i t h those taken i n S t a n l e y Park.. NATIVE RANGE STANLEY PARK FOOD ITEMS RELATION FOOD ITEMS RELATION TO DIET' TO DIET Ciuercus (8 s p e c i e s ) .' • * Suereus spp. " 'Aux.. J u l i a n s (12 s p e c i e s ) $ Olmus (3 s m c i e s ) S Floras (1 s p e c i e ) s Corya (7 s p e c i e s ) S Cor y l u s (1 s p e c i e ) Seas. Acer (4 s p e c i e s ) Aux. Acer (2 s p e c i e s ) Gratae#us sop. Aux. Crataegus spp. Aux* Somus (2 ape e i e s ) Aux. Gornus (1 s p e c i e ) Aux* fj-urius (1 spe e i e ) Aux. Prunus (1 s p e c i e ) Aux. Fungi Aux. Fung;! Seas. S - s t a p l e , y e a r round food Seas. - se a s o n a l food t h a t i s vised as l o n g as a v a i l a b l e Aux* - a u x i l i a r y foods - taken i n l i m i t e d q u a n t i t i e s The l i s t of foods from S t a n l e y Park i n Table X V I I I . i n c l u d e s a l l the Important food items o f t h i s l o c a l p o p u l a t i o n . I t i s seen t h a t the grays In t h i s a r e a are u t i l i z i n g the same food types as i n the E a s t e r n United S t a t e s but are g i v i n g emphasis to d i f f e r e n t food s p e c i e s . I n a l l cases the impor-tant, food s p e c i e s u t i l i z e d I n St a n l e y Park have r e l a t e d s p e c i e s u s u a l l y o f the same genus, u t i l i z e d by the grays i n t h e i r n a t i v e h a b i t a t . F o r example. S e v e r a l s p e c i e s o f maples are u t i l i z e d by indigenous p o p u l a t i o n s of gray s q u i r r e l s but only as an a u x i l i a r y food ( N i c h o l s , 1927). However i n Stanley Park where the p r e f e r r e d foods such as elms, h i c k o r i e s and walnuts are l a c k i n g , maples assume the r o l e of s t a p l e foods. The s q u i r r e l s are dependent upon these two s p e c i e s of maple and a crop f a i l u r e would undoubtedly be hard on the p o p u l a t i o n . I t appears t h a t the new environment has m o d i f i e d the food items of the gray s q u i r r e l but has not changed i t s b a s i c p l a n . N e s t i n g The i n f o r m a t i o n presented by F i t z w a t e r and Frank (1944) i n d i c a t e s t h a t i n Connecticut two s p e c i e s of c o n i f e r s , the e a s t e r n hemlock (Tsuga canadensis) and the white pine (Pinus strobus) supply 60 per cent of the nest s i t e s . The remainder are b u i l t i n deciduous t r e e s which are the predomin-ant form i n the f l o r a . This suggests t h a t c o n i f e r s are p r e f e r r e d f o r nest s i t e s over deciduous s p e c i e s . Data pre-sented i n Table IX a t t e s t s t h a t i n S t a n l e y Park c o n i f e r s are s e l e c t e d as n e s t s i t e s to the e x c l u s i o n of deciduous s p e c i e s . The p l e n t i f u l supply of s u i t a b l e c o n i f e r s has; .allowed the grays to e x p l o i t t h e i r preference f o r such s i t e s . Therefore the new h a b i t a t allows a f u l l e r e x p r e s s i o n of t h i s preference than d i d t h e i r n a t i v e haunts. I t i s a l s o apparent t h a t the s q u i r r e l s i n the s t u d i e d area b u i l d fewer l e a f n e sts than do those i n the e a s t . I t i s b e l i e v e d t h a t t h i s i s the r e s u l t of an abun-dance of s u i t a b l e den s i t e s which, appear, g e n e r a l l y , to be p r e f e r r e d to l e a f n e s t s . Reproductions The dioestral habit of the gray squirrel remains unaltered in i t s new surroundings. Indeed the whole repro-ductive phase of the l i f e cycle as set forth by Brown and Yeager (1945) corresponds very closely with the.conditions found in Stanley Park. One discrepancy does appear and that is the difference in time between the two breeding peaks. They found in Connecticut the i n i t i a l peak occupied the month of January and the second lasted from June 15 to July 15. The latter coincides with the conclusions in the present i n -vestigation, however the former data is at a variance. In. Stanley Park the primary peak extends from approximately March 3rd. to April 8 t h . No plausible explanation--:can be offered at this time. A l l attempts f a i l to explain why the instigation of male sexually active coincides with that i n : the Eastern United States but the period of oestrus in the two regions di f f e r s . Conclusions 1. The population exhibited an increase from 34 i n d i -viduals in June to 47 in August. .This l a t t e r level, gives a density of .98 gray sq u i r r e l s per acre. 2. The sex r a t i o obtained from 49E observations from June to September, 1950, resulted in 1 male to .645 females. The winter sex r a t i o appeared to be 1 male to .553 females but thi s proportion i s believed the r e s u l t of d i f f e r e n t i a l a c t i v i t y between the sexes. 3. The calculated r a t i o between adults and juveniles for the summer and early autumn of 1950 was 1:.47. 4. The gray members of the population are outnumbered by the melanistic individuals in the order of 1:6.1. 5. Three types of i n t r a s p e c i f i c intolerance were noted. These are; the peok order among groups of s q u i r r e l s , t e r r i t o r i a l i t y evidenced by defense of nests or food trees and i r r i t a b i l i t y when the population i s approaching i t s maximum in the f a l l . 6. Daily movements depend upon i n t r i n s i c factors for the i r extent and e x t r i n s i c factors for t h e i r degree. 7. No seasonal migration was noted. 8. The males-and females had a d i f f e r e n t i a l home range from January to September with the males having the l a r g -er. Both sexes appeared to have similar home ranges throughout the remainder of the year which coincides with the period of • sexual i n a c t i v i t y . 9 . M a l e s m o v e i n a n o n r a n d o m m a n n e r o v e r a n a r e a o f a t l e a s t 5 0 t o ' 5 5 a c r e s a n d t h e f e m a l e s m o v e s i n a s i m i l a r f a s h i o n o v e r a n a r e a o f 5 t o 1 5 a c r e s . 1 0 . T h e d a i l y a c t i v i t y c y c l e i s i n i t i a t e d " b y a p e r i -o d o f m a x i m u m a c t i v i t y s h o r t l y a f t e r s u n r i s e . T h i s g r a d u a l l y f a l l s a w a y a n d " b y m i d - m o r n i n g a l o w i s 1 r e a c h e d w h i c h e x t e n d s t i l l t h e a f t e r n o o n . P r o m t h i s t i m e u n t i l s h o r t l y b e f o r e d a r k a n a c t i v i t y p e a k o f s e c o n d a r y m a g n i t u d e i s n o t e d . D u r i n g t h e w i n t e r t h e i n t e n s i t y o f t h e t w o d a i l y p e a k s i s r e v e r s e d . 1 1 . D e g r e e o f o v e r c a s t d o e s n o t a l t e r t h e d a i l y a c t i v i t y c y c l e b u t h e a v y p r e c i p i t a t i o n l o w e r s i t m a r k e d l y . 1 2 . T h e w e s t e r n h e m l o c k s u p p l i e s 7 7 p e r c e n t o f t h e o u t s i d e l e a f n e s t s i t e s . T h e r e m a i n d e r o f t h e ' s i t e s w e r e f o u n d i n t h e w e s t ' e r n r e d c e d a r , s p r u c e a n d D o u g l a s f i r . 1 3 . D e n t r e e s a r e u s e d e x t e n s i v e l y a n d - t h e i r a b u n d -a n c e h a s l o w e r e d t h e n e e d f o r o u t s i d e l e a f n e s t s . 1 4 . G r a y s q u i r r e l s c o n s t r u c t r e s t i n g p l a t f o r m s w h i c h a f f o r d p r o t e c t i o n f r o m t h e e l e m e n t s . 1 5 . P r e d a t i o n h a s l i t t l e e f f e c t u p o n l i m i t i n g t h e p o p u l a t i o n . 1 6 . T h e g r a y s q u i r r e l i n S t a n l e y P a r k i s d i o e s t r u s w i t h t b e f i r s t c y c l e e x t e n d i n g f r o m e a r l y M a r c h t o t h e f i r s t w e e k o f A p r i l . T h e s e c o n d p e r i o d l a s t s f r o m J u n e 1 5 t h . t o J u l y 1 8 t h . - M a l e s a p p e a r s e x u a l l y a c t i v e f r o m J a n u a r y t o t h e m i d d l e o f A u g u s t . 1 7 . T h e g r a y s q u i r r e l i s p o l y g a m o u s w i t h d o m i n a n c e e s t a b l i s h e d a m o n g t h e a t t e n d e n t m a l e s o n a p h y s i c a l b a s i s . 1 8 . E a c h b r e e d i n g f e m a l e w a s a b l e t o r e a r 1 . 6 y o u n g t o t h e w e a n i n g a g e . 1 9 . T h e s t a p l e f o o d s a r e t h e s a m a r a s a n d v e g e t a t i v e p a r t s o f t h e v i n e a n d b r o a d l e a f m a p l e s . C e r t a i n f o o d s s u c h a s -b e r r i e s , b u d s a n d f u n g i a r e t a k e n . EG. A f e m a l e g r a y w a s s e e n t o g n a w o n a b o n e . 2 1 . W a t e r i s t a k e n f r o m p o n d s a n d f r o m t h e s u r f a c e o f l e a v e s . 2 2 . H u m a n s u p p l e m e n t a r y f e e d i n g p l a y s a m i n o r r o l e a n d t h e p o p u l a t i o n c o u l d e x i s t w i t h o u t i t . 2 3 . D i s t i n c t i n t r a s p e c i f i c i n t o l e r a n c e w a s o b s e r v -e d b e t w e e n t h e g r a y a n d t h e n a t i v e D o u g l a s s q u i r r e l . O n t h e a r e a s t u d i e d t h e g r a y a p p e a r s t o s u f f e r n o h a n d i c a p f r o m t h e D o u g l a s . 2 4 . I t w a s f o u n d t h a t g r a y s q u i r r e l s w o u l d d e s t r o y -b i r d n e s t s . H o w e v e r , t h e i r d e p r e d a t i o n s a p p e a r t o h a v e l i t t l e e f f e c t u p o n t h e b i r d p o p u l a t i o n s . L i t e r a t u r e C i t e d A l l e n , D . L . A n d e r s o n , R . M . A n t h o n y , H . E . B a k e r , R . H . B a u m g a r t n e r , L . L . B r o w n , L . G . ' , a n d L . E . Y e a g e r . B u r t , W . B . C a h o l a n e , V . H . C a r l s o n , A . J . C h a p m a n , F . B . 1 9 4 2 P o p u l a t i o n s a n d h a b i t s o f t h e f o x s q u i r r e l i n A l l e g a n C o u n t y , M i c h i g a n . A m . M i d i . N a t . , 2 7 ( 2 ) : 3 3 8 - 3 7 9 . 1 9 4 3 M i c h i g a n f o x s q u i r r e l m a n a g e -m e n t . M i c h . D e p t . C o n s e r . , G a m e D i v . P u b . , 1 0 0 : 1 - 4 0 4 . 1 9 4 6 C a t a l o g u e o f C a n a d i a n r e c e n t m a m m a l s . C a n . D e p t . M i n e s a n d R e s o u r c e s , N a t l . M u s . C a n . B u l l . , 1 0 2 : 1 - 2 3 8 . 1 9 2 8 F i e l d b o o k o f N o r t h A m e r i c a n M a m m a l s . P u t n a m C o . , N e w Y o r k . 1 9 4 4 A n e c o l o g i c a l s t u d y o f t r e e s q u i r r e l s i n e a s t e r n T e x a s . J o u r . Mamm., 2 5 ( 1 ) : 8 - 2 4 . 1 9 4 0 P o p u l a t i o n s t u d i e s o f t h e f o x S q u i r r e l i n O h i o . N . - A m . W l d l f . C o n f . T r a n s . , 3 : 6 8 5 - 6 8 9 . 1 9 4 5 F o x s q u i r r e l s a n d g r a y s q u i r r e l s i n I l l i n o i s . B u l l . 1 1 1 . N a t . H i s t . S u r v e y . , 2 3 ( 5 ) . 1 9 4 0 T e r r i t o r i a l b e h a v i o u r a n d p o p u -l a t i o n s o f s o m e s m a l l m a m m a l s i n S o u t h e r n M i c h i g a n . M i r . . P u b . M u s . G o v . , U n i v . M i c h . , N o . 4 5 : 1 - 5 8 . 1 9 4 6 T h e m a m m a l s o f M i c h i g a n . A n n A r b o r . T h e U n i v . M i c h . P r e s s . 1 9 4 2 C a c h i n g a n d r e c o v e r y o f f o o d b y t h e w e s t e r n f o x s q u i r r e l . J o u r . W l d l f . M g m t . , ' 6 ( 4 ) : 3 3 8 - 3 5 2 . 1 9 4 0 S a t i n g o f b o n e b y t h e p r e g n a n t a n d l a c t a t i n g g r a y s q u i r r e l . S c i . n . s . 9 1 ( 2 3 7 2 ) : 5 7 3 . 1 9 3 7 S u m m a r y o f t h e O h i o g r a y s q u i r -r e l i n v e s t i g a t i o n . N . A m . W l d l f . C o n f . T r a n s . , 3 : 6 7 7 - 6 8 4 . Gowan, L MoT *• 1947 Coventry, A. P . 1940 Dsanesly, R», aa^ 1933 A«S« parkes. Dice* I . R e 1927 Errington, P.L, 1946 Fitzwater, W.D., ana 1944 f . J» Frank @oodrum, P.D. 1937 1940 ©oraea, K. 1936 Hamilton. W.J.,Jr. 1943 Hayne, D.W. 1949 Hicks, E. A. 1949 Leopold,. A . 1947 Lincoln, F.C. 1930 if Range competition between male deer, b i g horn sheep and elk i n Jasper Park, Alberta. 5, Am. Wldlf*. Conf. Trans., IE: 223-227. The eating of bone by squ i r r e l s «. S o l * n*s> 92(2380): 128* > The oestrus cycle of ib©5 gray s q u i r r e l (Seiurras eorolinensls), P h i l . Trans* l o y a l See. London, Series B. Vol 222: 47-78* How do s q u i r r e l s f i n d burled nuts? Jour. Mamm,,, 8: 55. Predation and vertebrate popu-l a t i o n s . Quart* ReyV B i o l . , = 21: 144-177; 221-845. Leaf nests o f gray s q u i r r e l s in Connect! est. Jour± Mamm., 25: 160-170, Squi r r e l management i n east Tex-as. - B. Amv Wldlf, ? Conf.<Trans., 3: 670-676. 4 population study o f the gray s q u i r r e l in 5 eastern mesas. Tes. Ag. Ixp. S t s , Ba l l* 591. t e r r i t o r i a l ' behaviour and s o c i a l dominance among S c u i r l d a l . Jour* Mamm*, 17: 171-172, C a t e r p i l l a r s as food of tbe gray s q u i r r e l . Jour. Earn©., 24: 104. • Galeolation o f s i z e of borne range. Jour. Mamm*, 30: 1-18, Ecological factors a f f e c t i n g the a c t i v i t y ©f the western fox squ-i r r e l , (Soiurus r u f l v enter) (Geoffray)i Eool. Jfcnogr.f 19: 288-302. Scr/6 r,ers Game Management Soriboima, lew York. Caloulating waterfowl abundance on tbe basis of banding returns. U.S. Dept. Agr. Giro. 118: 1-4 Middleton, A.D. 1930 Miller, O.S. 1924 Nichols, J.T. 1927 Seton, E.T. 1928 Shorten, M. 1945 Ecology of the American gray squirrel in the British Isles. Proc. Zool. Soc. London, 1930 (2); 809-843. List of North American recent mammals. Smiths. Inst., U.S. Natl. Mus. Bull., 128. Notes on the food habits of the gray squirrel. Jour. Marnm., 8: 55-57. Lives of game animals. Literary Guild Am., Inc., N.Y., 4: 9-58; 82-106. Melanism in gray squirrels. Nat., 156: 46. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0107008/manifest

Comment

Related Items