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University' M icrdnlms international 300 N. Zeeb Road Ann Arbor, Ml 48106 8308934 FogI, John George ECOLOGY OF MELANISTIC GRAY SQUIRRELS (SCIURUS CAROLINENSIS) AND FOX SQUIRRELS (S. NIGER) IN AN URBAN AREA Michigan State University University Microfilms International 300 N. Zeeb Road. Ann Arbor, MI 48106 PH.D. 1982 PLEASE NOTE: In all c ases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark V 1. Glossy photographs or p ag es______ 2. Colored illustrations, paper or print_____ 3. Photographs with dark background ✓** 4. Illustrations are poor copy______ 5. Pages with black marks, not original copy______ 6. Print shows through as there is text on both sides of page______ 7. Indistinct, broken or small print on several pages 8. Print exceeds margin requirements_____ 9. Tightly bound copy with print lost in spine______ 10. Computer printout pages with indistinct print______ 11. Page(s)___________ lacking when material received, and not available from school or author. 12. Page(s)___________ seem to be missing in numbering only as text follows. 13. 14. 15. Two pages num bered___________ . Text follows. Curling and wrinkled p ages______ Other___________________________________________________________________ University Microfilms international ECOLOGY OF MELANISTIC GRAY SQUIRRELS (S ciurus c a r o lin e n s is ) AND FOX SQUIRRELS (S. n i g e r ) IN AN URBAN AREA By John George Fogl A DISSERTATION Submitted to Michigan S ta te U n iv e rs ity in p a r t i a l f u l f i l l m e n t of th e requirem ents f o r the degree of DOCTOR OF PHILOSOPHY Department of F is h e r ie s and W ild life 1982 ABSTRACT ECOLOGY OF MELANISTIC GRAY SQUIRRELS ( Sciurus c a r o l i n e n s i s ) AND FOX SQUIRRELS ( S. n ig e r) I O N URBAN AREA BY John George Fogl The ecology of an urban s q u i r r e l p o p u la tio n was s tu d ie d and compared w ith d a ta on r u r a l s q u i r r e l p o p u la tio n s . The s q u ir r e l p op u la tio n in a 200 a c re r e s i d e n t i a l a re a of East Lansing, Michigan, was composed of fox s q u i r r e l s ( Sciurus n ig e r) and th e descendants of m e la n is ti c gray s q u i r r e l s ( S. c a r o l i n e n s i s ) introduced during th e l a t e 1950's and e a r ly 1 9 6 0 's. During th e 36 month study (June 1977-May 1980), 128 s q u i r r e l s (81 black and 47 fox) were in d iv id u a lly marked w ith dye and observed f o r more than 4000 h o u rs. An average of 1.25 f e e d e rs per acre were m aintained by r e s i d e n t s in th e re s e a rc h area from which s q u i r r e l s could supplement t h e i r n a tu ra l food supply. The d i s t r i b u t i o n of black s q u i r r e l s in th e G reater Lansing area and f a c t o r s a f f e c t i n g t h e i r ra p id d is p e r s a l are d is c u s s e d . Compared to p u b lic a tio n s on ru r a l gray and fox s q u ir r e l p o p u la tio n s : 1) th e s tu d ie d urban s q u ir r e l d e n s i t i e s were higher - w in te r d e n s i t i e s ranged from 1 .6 - 2 .4 per acre and f a l l d e n s i t i e s were b e lie v e d to have been between 2 .0 - 4 .0 per a c re ; 2) average black s q u i r r e l l i t t e r s i z e was la r g e r (3.16 + .16 y o u n g / l i t t e r ) , while average fox s q u i r r e l l i t t e r s iz e was comparable (2.65 + .16 John George Fogl y o u n g / l i t t e r ) ; 3) d a i l y a c t i v i t y l e v e l s of E ast Lansing s q u i r r e l s were much hig her throughout th e y e a r ; 4) urban s q u i r r e l home ranges were sm a lle r (5-10 a c r e s ) and showed no d if f e r e n c e between males and fe m a les. Road k i l l s and c a t p re d a tio n were th e major sources of s q u i r r e l m o r t a l i t y in th e urban a re a s s tu d ie d , though m a ln u tr itio n and mange were suspected of c o n tr ib u tin g a p p re c ia b ly during sev ere w in te rs . Levels of i n t e r s p e c i f i c agg ressio n in creased d ra m a tic a lly during w in te r , when most i n t e r a c t i o n s occurred a t th e supplemental f e e d e r s . The black s q u i r r e l s e x c e lle d a t dominating th e se fe e d e rs and t h i s was b e lie v ed to have caused th e observed weight gain in black s q u i r r e l s and weight lo ss in fox s q u i r r e l s during th e Winter of 1979-80. Although th e presence of a s o c ia l h e ira rc h y was not in v e s t i g a t e d , some form o f a complex i n t e r s p e c i f i c dominance h e ira rc h y was suspected to e x i s t . Winter n e stin g a g g reg ation s iz e and t r e e sp e c ie s p re fe re n ce f o r n e s t lo c a tio n are in v e s t ig a te d . Recommendations f o r management and f u tu r e re s e a rc h on urban s q u i r r e l p op u latio n s was p re s e n te d . ACKNOWLEDGEMENTS I wish to thank th e members o f my d o c to ra l committee, Drs. George P e t r i d e s , R o llin Baker, John King and John H au fler f o r t h e i r h e lp fu l su g g estio n s and c o n s tr u c ti v e reviews o f the d i s s e r t a t i o n m an uscript. I am e s p e c i a l l y g r a te f u l t o Dr. John King f o r h is co n tin u a l guidance and encouragement throughout my re s e a rc h . His concern f o r gradu ate s tu d e n ts and h is w illin g n e s s to make time to s i n c e r e l y t a l k w ith them about t h e i r re sea rc h i s very much a p p re c ia te d . Thanks are a ls o extended to Chuck E lz in g a , Bobby Holder and B arbie Nawor f o r t h e i r a s s i s t a n c e in help ing w ith th e f i e l d work and f o r always being w i l l i n g to t a l k about s q u i r r e l s . 1 am most deeply in d eb t to B arbie f o r giving me a reason to f i n i s h my re s e a rc h . I would a ls o wish to thank Tena French, w ith o u t whose a s s i s t a n c e th e re s e a rc h would have never been pu t on paper. Watching h e r "g e n tly encourage" th e word p ro c e sso r to o p e ra te c o r r e c t l y was a le a r n in g e x p e rie n c e . The many hours o f tedio u s t o i l she p u t in to t h i s d i s s e r t a t i o n were c e r t a i n l y above and beyond the c a l l o f duty and have been g r e a t l y a p p re c ia te d throughout the e n t i r e w r itin g - r e w ritin g e x p e rie n c e . TABLE OF CONTENTS Page LIST OF TABLES......................................................................................... v LIST OF FIGURES.................................................................................... v ii INTRODUCTION............................................................................................. 1 LITERATURE REVIEW ................................................................................ 6 METHODS AND PROCEDURES........................................................................ 20 Study Area............................................................................................. Trapping and Marking........................................................................ F ie ld O b serv atio n s.............................................. D is tr ib u tio n of Black S q u ir re ls ............................................... P o p u la tio n ............................................................................................. Movements............................................................................................. Food A v a i l a b i l i t y ............................................................................ I n t e r s p e c i f i c Aggressive Behavior .......................................... Weather and Winter Weight F lu c tu a tio n s .................................. N e s t s ..................................................................................................... In te r a c tio n s with People............................................................... RESULTS....................................................................... 20 25 38 39 40 41 43 43 44 45' 46 47 D is tr ib u tio n of Black S q u ir re ls ......................... . . . . . 47 P o p u la tio n ......................................................................................... 51 M ovements......................................................................................... 60 Food A v a i l a b i l i t y ....................................................................... . 70 I n t e r s p e c i f i c Aggressive Benavior ...................................... 75 Weather and Winter Weight F l u c tu a tio n s .............................. 82 N e s t s ....................................................... .... . . . ................. 88 I n te r a c tio n s with People........................................................... 90 DISCUSSION........................................................................................ 94 D is tr ib u tio n of Black S q u ir re ls .......................................... 94 P o p u la tio n . . . . . . . . . . . . . . .............................. 96 Movements..............................................................................................106 Food A v a i l a b i l i t y ........................................................................ 113 I n t e r s p e c i f i c A ggressive Behavior ...................................... 115 Weather and Winter Weight F lu c tu a tio n s ...................................118 Nests ..................................................................................................120 I n te r a c tio n s with People. . . ............................................... 122 iii SUMMARY.......................................................................................................... 124 RECOMMENDATIONS ..................................................................................... APPENDIX A: APPENDIX B: Research exp lan a tio n sh ee t d i s t r i b u t e d t o r e s id e n ts of re sea rc h area a t the beginning of East Lansing s q u i r r e l study . . 129 132 New r e le a s e prepared by the Michigan S ta te U n iv e rs ity O ffice of Information Services which appeared in lo cal news­ papers during J u ly , 1980....................................... 135 LITERATURE CITED ................................................................................ 137 iv LIST OF TABLES Page Table 1, Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8. Pop ulation e s tim a te s of black and fox s q u i r r e l s in East Lansing, Michigan, using B a i le y 's modified formula of th e P e te rse n e s tim a te . E stim ates were based on s q u i r r e l counts ob tain ed by walking a predeterm ined course through a 50 acre tra p p in g a re a in th e re s e a rc h a r e a .................................................... 52 Comparison of tra p p in g success o f s q u i r r e l s in E ast Lansing, Michigan, w ith expected success based on black and fox s q u i r r e l p ro p o rtio n s observed in th e po pu la tio n on s q u i r r e l counts (d a ta summarized from Table 1) .............................. 56 D aily a c t i v i t y of black and fox s q u i r r e l s in East Lansing, Michigan, during each season. A c tiv ity le v e l is based upon th e average number of s q u i r r e l s s ig h te d w hile making o b se rv a tio n s during each two hour d a y lig h t tim e period during e n t i r e study (June 1977-May 1980). Time c o rre c te d to E astern Standard Time................................................................................. 61 Major t r e e s p e c ie s used as n a tu ra l food sources by black and fox s q u i r r e l s a t some time of th e year in East Lansing, Michigan, study (June 1977-May 1980). 71 A v a i l a b i l i t y of n a tu ra l foods to East Lansing, Michigan, s q u i r r e l s during f a l l seasons of 1977, 1978 and 1979.. 74 Monthly in d ic e s o f ag gressio n based on encounters between black and fox s q u i r r e l s in East Lansing, Michigan. Encounters ra te d a t 3 - severe a g g re ssio n , 2 = moderate a g g re ss io n , 1 - mild a g g re ssio n , 0 = t o le r a n c e or submissive behavior (moving away). D iffere n c e between black and fox s q u i r r e l in d ic e s t e s t e d with t - t e s t s ......................................................................... 77 C lim a to lo g ic al d a ta f o r Lansing, Michigan, during th e Winters o f 1977-78, 1978-79 and 1979-80. . . . 83 Changes in th e w eights of East Lansing, Michigan, s q u i r r e l s captu red more than once during th e October 27, 1979 to February 22, 1980 tra p p in g p e rio d . Weights in grams................................................... 84 v Table 9. Comparison o f a d u lt and s u b a d u lt black and fox s q u i r r e l weight changes ( in grams) cap tu red in East Lansing, Michigan, from October 27, 1979 to February 22, 1980. D iffere n c es between means t e s t e d w ith t - t e s t ........................................................................... 87 Table 10. Comparison of t r e e u t i l i z a t i o n as w in te r le a f n e s t s i t e s in dominant t r e e regions by s q u i r r e l s in East Lansing, Michigan.................................................................. 89 Table 11. Comparisons between d if f e r e n c e s in means of black and fox s q u i r r e l w inter n e s t a g g reg ation s in East Lansing, Michigan............................................................................. 91 vi LIST OF FIGURES Page Figure 1 Figure 2 A e ria l photograph of East Lansing and p a r t of th e Michigan S ta te U n iv e rs ity campus showing th e degree of t r e e canopy p re s e n t in r e s i d e n t i a l a r e a s . The s q u i r r e l re sea rc h are a is o u tlin e d . . . . S t r e e t map of th e same are a of East Lansing and Michigan S ta te U n iv e rs ity as shown in Figu re 1. . . 21 . Figure 3 Dominant t r e e regio ns of th e 200 acre s q u ir r e l re s e a rc h a re a in East Lansing, Michigan..........................24 Figure 4 Location of th e 50 acre tra p p in g are a w ith in th e East Lansing, Michigan, s q u i r r e l re s e a rc h a r e a . Route followed f o r s q u ir r e l po pu la tio n counts is i n d i c a t e d ............................................................. Figure 5 Fig ure 6 Figure 7 22 26 Equipment and procedure used in th e East Lansing, Michigan, s q u i r r e l study (June 1977-May 1980). (a) Box t r a p s , handling cones, weighing and tagging equipment, and f i e l d i d e n t i f i c a t i o n cards used during s q u i r r e l study, (b) Locking t r a p door open so trapp ed s q u ir r e l can e n te r handling cone. (c) Blowing in screened end of tr a p to encourage s q u ir r e l to leave t r a p , (d) Nose of black s q u i r r e l i s p ro te c te d by foam paddina a t end of handling cone w hile being e a r -ta g g e d , ( e j Bleaching black s q u i r r e l with Q -tip s and Helene C u rtis "Ready-Set-Glow" b le ac h ­ ing s o l u t i o n , (f ) Release of fox s q u i r r e l marked on r i g h t s id e w ith Nyanzol-D. (g) Black s q u i r r e l bleached on head and l e f t sid e is easy to i d e n t i f y from a d is ta n c e , (h) Black s q u i r r e l calm ly w a itin g in hand­ lin g cone w hile bleach s o lu tio n begins to ta k e e f f e c t . 27 Edge-punched s q u i r r e l i d e n t i f i c a t i o n cards used f o r E ast Lansing, Michigan, s q u i r r e l s tu d y ................................ 37 D is tr ib u tio n o f black s q u i r r e l s in th e East Lansing, Michigan, a re a as of f a l l 1981. I s o la te d p o pu lation o f black s q u i r r e l s in Abbott Road Park a ls o in d ic a te d . 48 vi i Figure 8 . Figure 9. Locations of the eleven is o l a t e d p o p u la tio n s of black s q u i r r e l s discovered in th e G re a te r Lansing, Michigan a re a , as of f a l l 1981................................................................ 49 E stim ates (+ S E) o f black and fox s q u i r r e l p o p u la tio n s in a 50 acre tra p p in g are a in East Lansing, Michigan, f o r th e Winters of 1977-78, 1978-79 and 1979-80. Due t o a lack of marked fo x s q u i r r e l s , o n ly black s q u i r r e l p op u la tio n e s tim a te s were c a lc u la te d f o r 1977-78. . . 54 Figure 10. Spring l i t t e r s iz e s of black and fox s q u i r r e l s in East Lansing, Michigan, f o r 1978, 1979 and 1980 ................... 58 Figure 11. Dates on which black and fox s q u i r r e l l i t t e r s in East Lansing, Michigan, were f i r s t observed ou t of th e n e s t in A pril and May of 1978, 1979 and 1980.......................... 59 Figure 12. D aily a c t i v i t y p a tte r n s of black and fox s q u i r r e l s during each season of th e y e ar in E ast Lansing, Michigan. Time is c o rre c te d t o Eastern Standard Time. Black s q u i r r e l s shown in s o lid l i n e , fox s q u i r r e l s in broken l i n e .......................................................... 65 Figure 13. Home ranges of female black s q u i r r e l s #7 (7 .8 a c re s ) and #10 (8 .3 a c re s ) in East Lansing, Michigan. . . . 66 Figure 14. Home ranges of male black s q u i r r e l s #27 (7 .8 a c re s ) and #48 (6 .3 a c r e s ) in East Lansing, Michigan. . . . 67 Figure 15. Home ranges of female fox s q u i r r e l #31 (9.1 a c re s ) and male fox s q u i r r e l s #36 (8 .2 a c re s ) and #61 (5 .5 a c re s ) in East Lansing, Michigan............................... 68 Figure 16. D is tr ib u tio n of supplemental fe e d e rs m aintained by r e s id e n ts in East Lansing, Michigan, s q u i r r e l re se a rc h a re a . D ensity of fe e d e rs in each t r e e region was: Oak = 1 .0 2 /a c r e ; elm = 1 .3 4 /a c r e ; maple = 1 .5 5 /a c r e ; h ick ory = 2 . 5 5 / a c r e ................ 76 Figure 17. In d ic e s of aggression (+ S E) f o r black and fox s q u i r r e l s during 36 month study in East Lansing, Michigan............................................................................................ vi i i 79 INTRODUCTION The urban environment 1s not one homogeneous e n t i t y , but r a t h e r a m ixture of ecoty pes. These areas can be roughly c l a s s i f i e d as those dominated by 1) th e t a l l b u ild in g s and pavement of b u s in e s s , commercial and l i g h t in d u s t r i a l areas having lim ite d green space, 2) th e smoke­ s ta c k s , n oise and d e b ris of heavy in d u s try having d is tu rb e d and p o l l u t ­ ed open areas c o n tain in g l i t t l e green space, or 3) th e b u ild in g s and surrounding grounds of r e s i d e n t i a l areas having varying amounts of green space. Within each of th e se ecotypes may be found green is la n d s o f parks and c e m e te rie s. They a re , f o r the most p a r t , is o la te d pockets o f the r u r a l environment and c o n tain w i l d l i f e populations which are only v i s i t e d by humans and, t h e r e f o r e , only s l i g h t l y in fluen ced by th e human presence. Within th e urban environment e x i s t s a number of animal s p e c ie s , i n v e r te b r a te as well as v e r t e b r a t e . Those sp ec ie s of g r e a t e s t i n t e r e s t t o th e w i l d l i f e e c o l o g i s t , and most o fte n r e f e r r e d to as urban w i l d l i f e , are th ose which a lso e x i s t in th e ru r a l environment and have adapted to th e urban environment. As noted by Edwards (1975:93), th e w i l d l i f e sp ec ie s most l i k e l y to su rv iv e in th e b u siness and i n d u s t r i a l are as of the urban environment would be b i r d s , because winged c re a tu r e s were most " e f f i c i e n t a t ty in g to g e th e r the f a r flu n g h a b i t a t elements" and were " a lso good f o r r i s i n g 2 above th e d e s tr u c tiv e n e s s of high d e n s ity people, dogs and c a t s . . . th e re i s no g re a t f u t u r e f o r mammalian w i l d l i f e in the c i t y p ro p e r." The urban sprawl exerienced by c i t i e s during th e l a s t 25-30 years has g r e a t l y in creased th e amount of ru r a l and sem i-natural land modified f o r human h a b ita tio n and a c t i v i t y . Of th e ecotypes in the urban environment, th e r e s i d e n t i a l area most n e arly d u p lic a te s th e r u r a l environment, th ereby making i t the most amenable to occupation by r u r a l mammalian w i l d l i f e s p e c ie s . The ubiqu itou s presence of humans and t h e i r a c t i v i t i e s in flu en c e t h i s ecotype, th e w i l d l i f e p o p u la tio n s, and the hum an-w ildlife r e l a t i o n s h i p , thus making th e urban w i l d l i f e pop ulation s unique from ru r a l w i l d l i f e p o p u la tio n s. Human in flu e n c e on w i l d l i f e in the r e s i d e n t i a l ecotype can c o n tr ib u te to m o r t a lit y through road k i l l s , t o v i t a l i t y through fe e d in g , and to d i v e r s i t y through th e in tro d u c tio n of w i l d l i f e s p e c ie s . All of th e se i n t e r a c t i o n s are i l l u s t r a t e d by the h is to r y of the gray s q u ir r e l in Michigan and subsequent re in tro d u c tio n of th e black phase in to a r e s i d e n t i a l ecotype. During th e n in e te e n th centu ry when most of Michigan was covered w ith f o r e s t s , th e gray s q u i r r e l (in c lu d in g th e black phase) was p re sen t in la rg e numbers along with the le s s common fox s q u ir r e l t h a t was mostly confined to southwestern Michigan (D. A llen , 1942). C learing the dense hardwood f o r e s t s f o r lumber, firewood and a g r ic u ltu r e elim in a te d much of the n a tu ra l h a b i t a t of th e gray s q u ir r e l and, with th e development of a g r i c u l t u r e and the near disappearance of th e gray s q u ir r e l in th e southern p a rt of lower Michigan (some blacks and grays 3 survived in th e D e tr o it a re a * ) , th e fox s q u i r r e l s of southw estern Michigan a p p a re n tly moved i n . "In woodlots throughout th e a g r i c u l t u r a l re g io n , th e fox s q u i r r e l found c o n d itio n s s im ila r in many re s p e c ts to i t s former p r a i r i e - e d g e h a b i t a t . I t extended i t s ran ge, learn ed to e a t corn, and prospered on s o i l t h a t had p re v io u s ly nu rtu red dense f o r e s t s and th e gray s q u i r r e l " (D. A lle n , 1943). While th e a g r i c u l t u r a l lands and woodlots of th e c o u n try sid e were b e t t e r s u ite d to th e fox s q u i r r e l , in c r e a s in g ly dense t r e e growths in th e wooded parks and r e s i d e n t i a l are as of c i t i e s and v i l l a g e s soon became p o te n tia l gray s q u i r r e l h a b i t a t . According to Johnson (1973), th e black phase of th e gray s q u i r r e l was introduced in to B a t t l e Creek in 1912 and soon became an abundant animal of th e urban environment. In th e 1 9 4 0 's , some of th e s e B a t tle Creek black s q u i r r e l s were trapped and in tro du ced in to th e Kellogg Bird Sanctuary - Gull Lake a re a . T h e r e a f te r , i t a p p a re n tly became somewhat of a fad to tr a n s p l a n t th e se a t t r a c t i v e black ro d e n ts in to urban environments. A number of southern Michigan c i t i e s follow ed t h i s p r a c t i c e , in c lu d in g M arsh a ll, Holland, Grand Haven and P o rt Huron (p erso n al o b serv atio n s and personal communications from c i t y o f f i c i a l s ) . In 1958, e ig h t black s q u i r r e l s from the Kellogg B io lo g ical S ta tio n a t Gull Lake were re le a s e d on th e Michigan S ta te U n iv e rs ity campus, with twelve more being s e t f r e e in 1962 (Baker, 1973). 1. These s q u i r r e l s Personal communication from Mr. Henry Glowniak, n a t u r a l i s t , B elle I s l e Nature C e n te r, D e t r o i t , and th e D e tro it Free P r e s s , D e tr o it Magazine, Jan. 21, 1979, a r t i c l e w r itt e n under th e pseudonym of Barbara M ille r . 4 a p p a re n tly l e f t th e campus a re a s h o r t l y a f t e r r e l e a s e and occupied nearby East Lansing r e s i d e n t i a l a r e a s . By 1977, almost 20 y e a rs a f t e r t h e i r in tr o d u c tio n , black s q u i r r e l s had Increased t h e i r d i s t r i b u t i o n and p o p u la tio n , t o th e p o in t where th e blacks comprised from 50-9056 of th e s q u i r r e l s in many neighborhoods (personal o b s e r v a tio n ) . Lack of inform ation on th e r e s i d e n t fox s q u i r r e l p o pu lation a t th e time of th e black s q u i r r e l in tr o d u c tio n makes i t im possible to determ ine whether th e b lack s were re p la c in g th e fox s q u i r r e l s or were only adding to i t . I t i s known, however t h a t by 1977 th e black s q u i r r e l s introduced in to M arsh a ll, Michigan, had t o t a l l y rep laced th e r e s id e n t fox s q u i r r e l p op u la tio n w ith in th e c i t y l i m i t s . 2 I n v e s tig a t io n s of s q u i r r e l p o p u la tio n s in r e s i d e n t i a l areas of East Lansing and in Toomey Woodlot, a 30-acre n a tu ra l are a s i t u a t e d among th e farms on th e southern p a r t of Michigan S ta te U n iv e rs ity , emphasized w i l d l i f e d if f e r e n c e s in r u r a l and urban environments. An obvious d if f e r e n c e was th e c lo se d is ta n c e to which one could approach s q u i r r e l s in r e s i d e n t i a l a r e a s . There a lso was an e v id e n t g r e a te r d e n s it y of s q u i r r e l s in r e s i d e n t i a l a r e a s . In th e urban a re a , to o , both black and fox s q u i r r e l s were f r e q u e n tly observed a t b ird feeders. The a d d itio n a l food a v a il a b le during c r i t i c a l times of the year would seem to have probable impact on th e behavior and popu latio n dynamics of urban s q u i r r e l s . 2. Personal communication from Mr. Bart Cook, Grounds Foreman, Department of P ark s, R ecreation and Cemetery, C ity of M arsh all, Michigan. V e rifie d by personal o b s e rv a tio n . 5 I t was decided to conduct a study on th e ecology of th e black and fox s q u i r r e l p o p u la tio n s in a r e s i d e n t i a l are a o f East Lansing in o rd er to : 1. determ ine th e p re s e n t d i s t r i b u t i o n of black s q u i r r e l s in the G re ater Lansing a re a , 2. compare th e behavior p a tte r n s and r e l a t e d biology of urban s q u i r r e l s with s im ila r d ata f o r r u r a l s q u ir r e l p o p u la tio n s , and 3. examine i n t e r s p e c i f i c com petition among th e black and fox s q u i r r e l s in E ast Lansing. LITERATURE REVIEW The l i t e r a t u r e r a r e l y r e f e r s to th e w i l d l i f e ecology o f urban mammals. In a paper p re se n te d a t th e 32nd North American W ild life Conference, Davey (1967:57) s t a t e d " th e re are few re fe re n c e s in the l i t e r a t u r e r e l a t i n g t o w i l d l i f e in urban a r e a s . W ild life Review, over some 30 y e a rs of p u b l i c a t i o n , has y e t to f in d and re p o r t papers r e l a t e d to d e s ir a b le w i l d l i f e s p e c ie s in urban a r e a s . The Journal of W ild life Management Index s i m i l a r l y c o n tain s nothing on th e s u b j e c t ." In 1969, th e 34th North American W ild lif e Conference theme was "Conservation in an Urbanizing S o c ie ty ," but f a i l e d to c o n tain a s in g le paper reg ard in g urban w i l d l i f e . Not u n t i l the 1974 symposium on " W ild life in an Urbanizing Environment" a t the U n iv e rs ity o f M assachusetts, Amherst, and th e 1975 symposium on " W ild life in Urban Canada" a t th e U n iv e rs ity of Guelph, O n ta rio , did urban w i l d l i f e re s e a rc h re c e iv e a t t e n t i o n as an area of study w ith in th e f i e l d o f w i l d l i f e ecology. P r io r to th e s e symposia, i n t e r e s t in urban w i l d l i f e was expressed m ostly in th e are as of (1) th e problems with w i l d l i f e in th e c i t y , (2) th e need f o r and value o f having w i l d l i f e w ith in the urban environment, and (3) how urban p lan ners and r e s i d e n t s can m anipulate th e h a b i t a t to a l t e r th e sp ec ie s d i v e r s i t y in th e urban environment. 6 7 Problems with Urban W ild life Concerning th e problems caused by w i l d l i f e in th e urban environ­ ment, Smith (1974) suggested they g e n e ra lly f e l l in to s ix a re a s : s t r u c t u r a l damage, crop damage, ornamental p la n t and landscape damage, a e s t h e t i c d e g ra d atio n , human s a f e t y , and d is e a s e tra n s m is sio n . To keep th e se problems a t a minimum, he concluded i t must be r e a liz e d th a t animals responded to fa v o ra b le h a b i t a t co n d itio n s by in c re a s in g t h e i r numbers and we must th e re fo re t r y to modify h a b i t a t s so t h a t th e re is th e l e a s t amount of c o n f l i c t , or a t the l e a s t , r e a l i z e t h a t damage abatement may be n e ce ssa ry . In d is c u ssin g th e hazards of w i l d l i f e to a i r c r a f t , Solman (1974) a lso suggested e co lo g ica l m o d ifica tio n to make th e a i r f i e l d u n a t t r a c t i v e to b ird s as the b a sic way to minimize the c o n f l i c t with w i l d l i f e . A fte r d is c u ssin g the d isea se problems of urban w i l d l i f e , Karstad (1975) suggested t h a t i t may be p re fe ra b le to l i v e with th e d is e a s e hazards and enjoy th e e s t h e t i c b e n e f its of having w i l d l i f e , r a t h e r than t r y to keep th e w i l d l i f e o u t. He a ls o suggested t h a t w i l d l i f e in the c i t y could be a useful in d ic a to r of problems in th e environment. For example, th e occurrence of salm o n ello sis in urban w i l d l i f e may in d ic a te raw sewage was e n te rin g a stream . In connection with d is e a s e and p a r a s i t e s in urban w i l d l i f e , Locke (1974:111) concluded t h a t "the p ub lic needs to be made aware of th e causes of m o r t a lit y among w i l d l i f e liv in g in c lo se proxim ity to human h a b ita tio n so t h a t f e a r s based on ignorance can be e lim in ated and, when n e c e ssa ry , c o n tro l or s a n i t a t i o n procedures can be undertaken to prevent human i n f e c tio n " . Excluding th e many h e a l t h - r e l a t e d s tu d ie s on r a t s and mice, th e o nly mammalian sp ecies causing problems in th e urban environment were s q u i r r e l s , f e r a l dogs and coyotes. Flyger (1970) dism issed urban gray s q u i r r e l s as i n s i g n i f i c a n t hazards from a p u b lic h e a lth s ta n d p o in t, but conceded t h e i r p ro p e n sity f o r gnawing caused much damage to telephone cables and houses or b u ild in g s which they e n te r e d . They were also n oto riou s f o r damaging gardens and ornamental tr e e s and shrubs. Although f e r a l dogs were not s t r i c t l y a w i l d l i f e problem, th ey i l l u s t r a t e d the problems involved in m aintaining an u n r e s t r i c t e d , la rg e mammal commensal with man. Beck (1971, 1973, 1974) conducted ex ten siv e s tu d ie s on th e ecology of urban dogs. He found l i t t l e evidence t h a t s t r a y s were an a c ti v e ly s e lf - p e r p e t u a tin g pop ulatio n and hypothesized th e s tr a y population was m aintained by con tinu al re c ru itm e n t from re le a s e d or escaped p e ts . The r e a d i l y a v a ila b le s u p p lie s of food and water in th e c i t y provided dogs, c a ts and r a t s nourishment and a l l seemed to t o l e r a t e each o t h e r 's p resen ce, sometimes being observed e a tin g garbage w ithin a f o o t of each o th e r . Beck f e l t t h a t dogs could be used as in d ic a to r s of urban environmental degradation and could be c o r r e la te d with tr a s h and pest s p e c ie s . One of th e e co lo g ica l im p lic a tio n s of a la rg e population of f e r a l dogs in th e urban environment was th e p o te n tia l h e a lth hazard caused by th e thousands of tons of excrement and hundreds of thousands of g a llo n s of u rin e l e f t on th e s t r e e t s each y e a r . Besides d is e a s e s picked up by c h ild re n playing in in fe c te d d i r t , dogs fe c es was a major f a c t o r in the breeding of h o u s e f lie s , which could then tra n s m it Salm onella from dogs to man. A lso, r a t s have been observed fe edin g on dog fe c e s and were most common in a l le y s with high f e c a l r e s id u e s . Leach and Hunt (1974) reviewed th e problem of coyote co n tro l in th e r u r a l w est, c o n c e n tra tin g m ainly on i t s h i s t o r y in C a l i f o r n i a , and G ottsch alk (1981) re p o rte d a number of documented a tta c k s of coyotes upon humans in urban a r e a s . The urban coyote was i d e n t i f i e d as a new dangerous breed which had l o s t i t s f e a r of humans. Los Angeles County a u t h o r i t i e s faced an u n n a tu r a lly la rg e pop ulatio n of c o y o te s, where th e only " n a tu ra l enemy" was th e autom obile. The presence and a c t i v i t i e s of human beings was i d e n t i f i e d as th e major c o n tr ib u to r to th e coyote problem. Besides i n te n tio n a l fe e d in g of coyotes by well-meaning s u b u r b a n ite s , coyotes a lso fed on garbage and d rie d dog and c a t food, as well as on an oc ca sio n al p e t poodle or c a t . pools served as water h o le s. The u b iqu itou s swimming Inform ation on th e po p u la tio n l e v e l s , re p ro d u c tiv e success and movements were la ck in g in th e l i t e r a t u r e , making i t d i f f i c u l t to recommend management p roced ures. Value of Urban W ild life Surveys have shown a s tro n g d e s ir e among c i t y d w ellers f o r c o n ta c t and ex p erien c e s w ith w i l d l i f e . Dagg's (1970, 1974) surveys in W aterloo, O n ta rio , in d ic a te d most householders lik e d having b ir d s , s q u i r r e l s , chipmunks and r a b b i t s on t h e i r p ro p e rty , but not o th e r mammals because of th e damage th e y caused. Dawson e t a l . (1978) found a r e l a t i v e l y high awareness and i n t e r e s t in w i l d l i f e f o r most respondents in t h e i r Albany, New York, survey: 54% m aintained one or more h a b i t a t improvements around t h e i r home, 73% p a r t i c i p a t e d in 10 non-consumptive (photography, e t c . ) and 36% in consumptive (h un tin g , e tc .) w ild life-relate d a c tiv itie s . In T a y lo r, Michigan, a suburb of D e t r o i t , Cauley (1974) found t h a t 76% of th e people interview ed lik e d and enjoyed seeing w i l d l i f e on t h e i r p ro p e rty , only 4% d i s l i k e d wild an im als, and no one a c t i v e l y discouraged th e presence of w i l d l i f e . Attempts to a t t r a c t w i l d l i f e were made by 32% o f th e r e s i d e n t s and 80% put food out f o r w i l d l i f e some time during th e y e a r . A survey of cem eteries in th e G re ater Boston are a by Thomas and Dixon (1973) re v e a le d they were being h e a v ily u t i l i z e d by u rb a n ite s f o r a number of outdoor r e c r e a tio n a l a c t i v i t i e s in clu d in g some which were w i l d l i f e re la te d . Davis (1974) s t a t e d t h a t th e National W ild life F e d eratio n Backyard W ild life Program demonstrated p e o p le 's hunger f o r le a d e rs h ip in urban w i l d l i f e management on a small s c a l e . Over a q u a rte r m illio n r e p r i n t s were d i s t r i b u t e d concerning methods to a t t r a c t w i l d l i f e in to th e backyard. Others in t e r e s t e d in urban w i l d l i f e have addressed th e educational and p o l i t i c a l value of w i l d l i f e in th e c i t y . E uler (1975) suggested t h a t th e r o l e of th e O ntario M in istry of N atural Resources, W ild life Branch, in managing urban and non-game w i l d l i f e was to educate the p u b lic toward a more r e a l i s t i c view of th e n a tu ra l world and make them aware of w i l d l i f e management p r a c t i c e s . Howard (1974:17-18) s t a t e d t h a t "man has a moral r e s p o n s i b i l i t y to manage n a tu re once he has d is ru p te d i t " and "th e e s s e n t i a l need i s f o r man to reco gn ize th a t he i s p a r t of n a tu re , and t h a t he must meet n a tu re a t l e a s t halfway." DeGraaf and Thomas (1973) r e a l i z e d t h a t an urban e l e c t o r a t e uninformed about n a tu ra l p ro c e sses and resou rce problems could c r e a te problems f o r 11 b i o l o g i s t s and o th e r re so u rce managers. Dagg (1970) p o in ted out th a t urban p u b lic v oting power could a f f e c t w i l d l i f e c o n se rv a tio n throughout th e world. Perhaps th e most thought provoking and c o n tr o v e r s ia l value of w i l d l i f e in th e urban environment was th e e f f e c t w i l d l i f e may have on th e developmental b io lo g y of human c h ild r e n . V alerius G e ist (1975) hypothesized t h a t th e r e t e n t i o n of n a tu ra l environments during the ontogeny of c h ild re n was b e n e f ic ia l to them. He p resented da ta from a number of s tu d ie s on th e phenotypic development of th e b ra in and I n t e l l i g e n c e Q uotients in r e l a t i o n to environmental m a n ip ulation . G e ist noted t h a t " in i t s phenotypic development during ontogeny, an in d iv id u a l needs not only a n u t r i t i o n t h a t is e x c e l l e n t , but a ls o a s o c i a l l y d iv e rs e and i n t e l l e c t u a l l y c h allen g in g m ilie u ." He argued t h a t " th e a v a i l a b i l i t y o f n a tu re is an e x c e lle n t p r e r e q u i s i t e to high i n t e l l e c t u a l and phy sical development of humans during ontogeny, a p r e r e q u i s i t e many m iddle- and u p p e r-c la ss f a m ilie s c l e a r l y are exposed t o , s in c e th e y re s id e more o fte n than not c lo s e to or in areas with d iv e rs e p la n t and animal l i f e . . . th e r e f o r e a n e g le c t to provide in urban areas r ic h n a tu ra l environments in areas where people of low income are found reduces th e p o te n tia l of c h ild re n found th e re to develop i n t e l l e c t u a l l y o r p h y s ic a lly to th e same e x te n t as c h ild re n from econom ically more p r iv ile g e d p a r e n ts ." Conceding t h a t "no one stu d y demonstrates c o n c lu s iv e ly t h a t r e t e n t i o n of n a tu ra l environments f o r th e b e n e f i t of c h ild r e n during ontogeny i s b e n e f ic ia l to them," he concluded " th e c ir c u m s ta n tia l evidence makes such a conclusion a l l but in e s c a p a b le ." 12 W ild life in the c i t y could a lso in flu e n c e th e awareness of world wide environmental problems. s tim u la tio n Again G e ist (1975) observed th a t "th e of i n t e r e s t in n a tu ra l e v e n ts , o b je c t s and environments g e n e ra te s an i n t e r e s t i n , a p p re c ia tio n of and u ltim a te ly r e s p e c t f o r th e land from which we d e riv e our s u ste n a n c e ." He suggested t h a t perhaps th e b e st way to c u r t a i l th e tre n d of environmental degrad ation would be to "provide in urban a r e a s , where most of our c i t i z e n s l i v e , some is la n d s of environments t h a t support a r ic h p la n t and animal l i f e . I t s tim u la te s p e rso n s, ro uses c u r i o s i t y and in th e longrun helps to c r e a te a c i t i z e n r y aware o f the values of th e la n d ." Urban H a b ita t M anipulation Davey (1967:58) noted t h a t "most s o c i o l o g i s t s , a r c h i t e c t s , landscape a r c h i t e c t s , and c i t y planners today s t r e s s th e importance of d i v e r s i t y in our c i t i e s . . . th e y v i s u a l i z e . . . a s t a b i l i z e d , s e l f - r e s t o r i n g neighborhood and community - a climax c i t y , in e c o lo g ic a l t e r m s . . . th e s e u rb a n -o rie n te d p r o f e s s io n a ls can use inform ation on w i l d l i f e management." A number of problems with urban h a b i t a t s which tended to decrease s p ec ie s d i v e r s i t y have been i d e n t i f i e d by b i o l o g i s t s . Edwards (1975) n o tic e d a d e f i n i t e need f o r a shrub la y e r in th e urban f o r e s t , and S te a rn s (1967) f e l t t h a t th e small s iz e and d i s c o n t i n u i t y of u n i t s , g e n e r a lly w ithout c o r r i d o r s , and the absence o f d i v e r s i t y were th e major problems in urban w i l d l i f e h a b i t a t . G e ist (1975) suggested th e p r o te c tio n of r i v e r floo d p la in s as parks to in c re a s e th e d i v e r s i t y of w i l d l i f e , and th e b u ild in g of highway underpasses where major animal t r a i l s c ro ss to reduce highway 13 w i l d l i f e k i l l s in urban a r e a s . M a ffe i's (1978) study showed t h a t p ro p e rly managed urban g o lf courses could supply th e d i v e r s i t y of h a b ita ts necessary f o r s u rv iv a l of w i l d l i f e through the use of uncut f i e l d s , marshes and water ha za rd s, high roughs, unmanaged f r in g e a r e a s , c o nifero us and mixed hardwood s ta n d s , and th e c a re fu l use of i n s e c t i c i d e s to minimize hazards to w i l d l i f e . Whatever the s p e c i f i c improvements in urban h a b i t a t , Stearns (1967) observed t h a t they must provide a v a r i e t y of food sources such as annual and perennial p la n tin g s or planned n e g le c t f o r regrowth of wild and weedy food p l a n t s , adequate water both summer and w in te r, adequate cover and tr a v e l c o rrid o r s between h a b i t a t u n its such as c o n ife r stands and unmowed grass a re a s , p ro te c tio n from humans as through the use of thorny shrub s p ec ie s and hidden fe n c in g , and population co n tro l by p re d a to rs , weather or o th e r means to prevent h a b ita t d e t e r i o r a t i o n . While an awareness of th e need f o r and the value of having w i l d l i f e w ith in th e urban environment has been e s t a b lis h e d , and the problems r e l a t e d to w i l d l i f e in the c i t y have been discussed f o r some tim e, recommendations f o r managing those ru r a l sp ec ie s drawn in to urban areas by b e n e f ic ia l h a b i t a t manipulation have been based upon knowledge of ru ra l p o p u la tio n s . Maestro (1974) r a is e d some q u e stio n s about the a p p l i c a b i l i t y of knowledge on r u r a l sp ec ie s to populations p re s e n t in urban a r e a s . "The home range requirem ents of most species have been documented in th e 'w i l d 1, but can we consider th e se requirem ents to hold in an open-space system in the middle of a 10,000 acre newtown? ...w h a t are the e f f e c t s of human d is tu rb a n c e , n o is e , domestic p e ts , 14 b a r r i e r s to movement p a tte r n s such as ro a d s, and narrow connecting lin k s in th e open-space system? ...how do t h e i r home range and h a b i t a t requirem ents compare to t h e i r c o u n te rp a rts in th e w ild ?". Geis (1975:83) a lso noted t h a t " th e usual approaches to enhancing w i l d l i f e p o p u latio n s based on experience in ru r a l areas o fte n do not apply in urban s i t u a t i o n s . . . f u r t h e r research on f a c t o r s d e fin in g urban w i l d l i f e p opu latio ns and t h e i r management i s needed." Urban W ild life Stud ies S tu d ie s on b ird popu latio n s in urban areas are common compared to mammal s t u d i e s . Thomas and DeGraaf (1975) b r i e f l y mentioned the e s s e n t i a l s of seventeen urban b ird s t u d i e s , but only noted th re e auth o rs who had stu d ie d gray s q u i r r e l s and raccoons in urban a re a s . A few o th e r urban mammal s tu d ie s have sin ce been re p o rte d . Beck's (1971, 1973, 1974) study on f e r a l dogs, though an e x c e lle n t urban ecology stud y, may not be considered w i l d l i f e re sea rc h by some, in t h a t i t is not on a "wild" r u r a l sp ec ie s which has adapted to the urban environment. Ryan and Larson (1976) s tu d ie d chipmunks in a r e s i d e n t i a l environment near Amherst, M assachusetts. They found chipmunks h e av ily u t i l i z e d man-supplied food so u rc es, so much so th a t th e normal period o f chipmunk i n a c t i v i t y during l a t e J u ly and August was c l e a r l y la ck in g . They concluded t h a t " a r t i f i c i a l feeding and physical f e a tu r e s in urban r e s i d e n t i a l grounds appear to in fluen ce the seasonal p a tte r n and s p a t i a l d i s t r i b u t i o n of e a s te rn chipmunk a c t i v i t y " . 15 In t h e i r study of an urban deer herd in Winnipeg, Manitoba, Shoesmith and Koonz (1977) noted t h a t over a h a lf m illio n people and 200 w h i t e - t a i l e d deer c o h a b ita te d in th e g r e a te r Winnipeg a re a . While th e deer herd was f l o u r i s h i n g , th e a v a ila b le h a b i t a t , la r g e ly p r iv a te land, was dw indling. The deer herd e x is te d in a number of small c o n c e n tra tio n s c lo s e ly a s s o c ia te d with parks or wooded a r e a s , of which th e Charieswood deer herd was the l a r g e s t c o n ce n tra tio n and th e one most in te n s iv e ly s tu d ie d . The Charleswood deer herd was found to be la r g e ly sed e n ta ry , marked in d iv id u a ls having " a l l been re-observed or recovered w ithin th e c i t y l i m i t s and w ithin 2-3 km of t h e i r i n i t i a l cap tu re s i t e . Man-made b a r r i e r s such as fe n c e s , b u ild in g s and h e av ily used s t r e e t s probably prevent much exchange of deer" w ith o th e r nearby a re a s . The d e n s i t i e s of c i t y deer were found to be as high as or higher than d e n s i t i e s anywhere in Manitoba. One of th e major reasons f o r t h i s was the c lo se a s s o c ia tio n of w inter cover to r e a d ily a c c e s s ib le food so u rc e s. N ative foods were "not p re sen t in s u f f i c i e n t q u a n t i t i e s to support th e p re s e n t deer herd i f they had to r e l y on n a tiv e foods a lo n e." During w in ter the deer r e l i e d mostly on "sugar beet t a i l i n g s l e f t in f i e l d s , waste hay and g ra in around rid in g s t a b l e s , waste hay a t a garbage dump and con cen trated a l f a l f a p e l l e t s and powder near a processing p l a n t " . The g r e a t e s t s in g le m o r t a lit y f a c t o r was c ar k i l l s with an average of 27 deer being k i l l e d each year on c i t y s t r e e t s in Charleswood. Dogs, harassment by people, i l l e g a l sh o o tin g , p a r a s i t e s and d is e a s e s accounted f o r some m o r t a lit y , but none had a s i g n i f i c a n t in flu en c e on the base p o p u la tio n . The re s e a rc h e rs concluded t h a t deer had "demonstrated i t s a b i l i t y to qu ickly recover 16 from th e e f f e c t s of severe w inter c o n d itio n s , t o a d ju s t to dim inishing a v a i l a b l e h a b i t a t and to t o l e r a t e human p re s s u re " . S tu d ie s on urban raccoon pop ulatio ns have been conducted by Schinner and Cauley (1973, 1974) in C l i f t o n , Ohio (a suburb of C i n c i n n a t i ) , Cauley (1974) in T a y lo r, Michigan, and Hoffman and Gottschang (1977) in G lendale, Ohio (a n o th e r suburb of C i n c in n a ti ) . A s i g n i f i c a n t d if f e r e n c e in d e n s ity of raccoons in urban and r u r a l are as was ap p aren t. Maximum d e n s i t i e s in r u r a l are as ranged from one raccoon p er 1 1.7 -1 6 .2 a c r e s , w hile Schinner and Cauley re p o rte d a range of 1 /1 .4 -2 3 acres in C lif to n and Hoffman and Gottschang re p o rte d 1 /3 .6 ac re s (1 /1 .4 6 ha) in G lendale. The g re a t range in th e C lif to n p op u la tio n d e n s i t i e s was due to an outbreak of canine distem per which reduced popu latio n e s tim a te s from 145 in 1968 to 51 in 1969. While t h i s was th e major p o p ulatio n lim it in g f a c t o r during th e s tu d y , dog and c a r k i l l s and i l l e g a l hunting were a lso recorded as m o r t a l i t y so u rc e s. Hoffman and Gottschang found t h a t permanent water did not seem as im portant in th e d i s t r i b u t i o n of Glendale raccoons as th e presence of supplemental fo o d s , such as garbage and handouts by r e s i d e n t s . Perhaps more im portant t o th e d i s t r i b u t i o n of raccoons would be th e presence of high d e n s ity housing. Cauley re p o rte d no raccoon c a p tu re s in densely housed areas in Taylor and a t t r i b u t e d th e lack of raccoons to th e back­ yard s being enclosed w ith a fo u r f o o t c h a in - lin k fe n c e , th e presence of many dogs kept o u t- o f - d o o r s , l i t t l e v e g e ta tiv e cover and a t o t a l lack o f n a tu ra l den s i t i e s . The home ranges were found to be much sm aller f o r urban raccoons (average of 20.6 a c re s in C lif to n and 12.75 acres in G lendale) than 17 re p o rte d f o r r u r a l raccoon p o p u la tio n s (a range of 27-500 a c r e s ) . Schinner and Cauley noted t h a t movements of urban raccoons were r e s t r i c t e d to t r a v e l between den s i t e s and fe ed in g areas and did not show th e random fo ra g in g c h a r a c t e r i s t i c of non-urban raccoons. Hoffman and Gottschang a ls o observed extreme l i n e a r i t y of home ran ge, averaging 5 .5 tim es longer than wide in G lendale, and a t t r i b u t e d i t to th e r e a d i l y a v a il a b le food supply and th e e f f e c t of th e l i n e a r urban h a b ita t. Not only did th e raccoons adapt t h e i r tr a v e l ro u te s to l i n e a r man-made s t r u c t u r e s such as fence l i n e s , storm d ra in s and s t r e e t c u l v e r t s , but they a lso used sew ers, r e fu s e dumps, a t t i c s , garages and chimneys as den s i t e s . Cauley a lso re p o rte d th e use of ground hog dens and o u tb u ild in g s as den s i t e s in T a y lo r. Opossums were th e only p o te n tia l com petitors of raccoons in urban are as to be re p o rte d (Hoffman and G ottschang). These s tu d ie s have in d ic a te d t h a t th e presence of supplemental fe e d in g in th e urban environment, whether in te n tio n a l or a c c id e n ta l ly provided as garbage o r w aste, can in flu e n c e seasonal and/or d a ily a c t i v i t y and abundance of anim als. The a v a i l a b i l i t y of food was probably th e s in g le most im portant f a c t o r a f f e c t in g th e s p a t i a l d i s t r i b u t i o n , home ranges and pop ulation dynamics o f urban w i l d l i f e . New m o r t a l i t y sources were introduced in th e urban environment, w hile th o se of major importance in r u r a l environments played a l e s s e r r o l e . S q u irre l s tu d ie s w ith in th e urban environment have been conducted m ostly in parks and cem eteries which were in s u la te d from th e in flu e n c e o f humans in nearby r e s i d e n t i a l a r e a s . These cemetery and park s q u i r r e l p o p u la tio n s were a c t u a l l y in a h a b i t a t more c lo s e ly r e l a t e d to 18 r u r a l environments and could not be expected to d is p la y a l l th e c h a r a c t e r i s t i c s of p o p u la tio n s su b jec te d to th e f u l l impact of human presence and a c t i v i t i e s in th e urban environment. Bakken (1952) s tu d ie d th e i n t e r r e l a t i o n s h i p s of gray and fox s q u i r r e l s in an 80 a c re cemetery in Madison, W isconsin, in which "th e p o pu la tio n was unfed, n a t u r a l l y o c cu rrin g and r e l a t i v e l y u n d is tu rb e d ." Robinson and Cowan (1954) s tu d ie d a p o pu latio n of gray s q u i r r e l s (m ostly m e la n is tic phase) which had been introduced in to an i s o la te d f o r e s t and park are a of 1000 a c r e s . The in flu e n c e of human a c t i v i t y was minimal in t h e i r 60 a c re study area and only about a t h i r d of th e s q u i r r e l s made some use of "hand-outs" from park v i s i t o r s . F ly g e r 's (1955, 1959, 1960, 1970, 1974) r e p o r t s on gray s q u i r r e l s have been r e f e r r e d to as being urban or suburban, but th e s q u i r r e l po p u latio n s s tu d ie d were a c t u a l l y in two 10 acre woodlots r e l a t i v e l y i s o l a t e d from o th e r woodlots. The woodlots were about o n e - th ir d of a m ile a p a rt and were on th e enclosed grounds of a h o s p ita l and were not d is tu rb e d by human a c t i v i t i e s . A p o rtio n of each woodlot had a ls o been l i g h t l y grazed. Hathaway (1973) s tu d ie d gray s q u i r r e l s in a 733 a c re cemetery in a la rg e u n id e n tif ie d midwest c i t y . S e le c tin g "a small p o rtio n in th e middle of th e o ld e s t s e c tio n of th e cemetery in which to conduct th e s tu d y ," he noted t h a t th e s q u i r r e l s were "not e x c ite d and endangered by th e dogs, c h ild r e n , and high-speed c ars t h a t may plague s q u i r r e l s in o th e r s e c tio n s of th e c i t y . " Thompson (1977a, 1977b, 1978a, 1978b, 1980) s tu d ie d a gray s q u i r r e l p o p u la tio n in a 72 a c re (28.7 ha) s e c tio n o f a cemetery in T oronto, O n ta rio . He noted t h a t "although the 19 s q u i r r e l s in th e cemetery were accustomed to the a c t i v i t y and presence o f peop le, th e y were not as tame as those found in th e surrounding re sid e n tia l a r e a s ... None of the s q u i r r e l s sought or received 'h an d o u ts' from th e cemetery v i s i t o r s . Not one case was noted of a r t i f i c i a l feeding of th e s q u i r r e l s by people v i s i t i n g th e cemetery," (1980:702). The only s q u i r r e l study to be conducted in the r e s i d e n t i a l ecotype was on fox s q u i r r e l s by Cauley (1974) in T ay lo r, Michigan. He noted th e abundance of food, a reduced home range (10.3 acres f o r ju v e n ile s and 5.3 acres f o r a d u lts ) and e x ten siv e use of the non-natural environment ( tr a v e l along telephone cables and denning in chimneys and a ttic s). This study was a c t u a l l y on fo u r d i f f e r e n t species ( c a r d in a l, blue j a y , raccoon and fox s q u i r r e l ) w ith in the urban environment and th e r e f o r e supplied only lim ite d inform ation on s q u i r r e l s . While th e cemetery and park s tu d ie s on s q u i r r e l s re p o rte d some of th e d iff e r e n c e s observed in o th e r species adapted to urban a re a s , no in -d ep th study has to d ate been conducted on s q u i r r e l s in the urban environment. This East Lansing black and fox s q u i r r e l study i s b elieved to be the f i r s t to do so. METHODS AND PROCEDURES Study Area East Lansing i s a d jac e n t to th e c a p it a l c i t y of Michigan and is located in Ingham County in the s o u th -c e n tr a l p a r t of the s t a t e . I t is mainly a r e s i d e n t i a l community with a small downtown business d i s t r i c t across from th e Michigan S ta te U n iv e rs ity campus. An a e r ia l photograph taken on August 21, 1978 (F igure 1) ana a s t r e e t map of East Lansing (Figure 2) covering th e same area show the r e s i d e n t i a l n ature of the town, degree of canopy cover and th e lo c a tio n of the re sea rc h a re a . The study s i t e is in an o ld e r p a r t of town where th e tr e e s have developed such la rg e crowns t h a t th e s t r e e t s are hidden from view in th e a e r i a l photograph. A d i f f e r e n t s i t u a t i o n is obvious to the n o rth e a s t of the re s e a rc h area where the s t r e e t s of the newer su b d iv isio n are q u ite prominent. The research are a i s bounded by Saginaw S t r e e t (M-78, Temporary 1-69) on th e n o rth , H arrison Avenue on the w est, Abbott Road on the e a s t and Grand River Avenue (M-43) on the so u th. The area i s g e n tly r o l l i n g with e le v a tio n s ranging between 840-870 f e e t . Covering a l i t t l e more than 200 a c r e s , th e re sea rc h area is 4% business d i s t r i c t , 8% open park area (in c lu d in g a school b u ild in g and playground) and 88% r e s i d e n t i a l (20% occupied by paved s t r e e t s and 68% being l o t s with 20 Figure 1. A erial photograph o f East Lansing and p a r t o f the Michigan S ta te U n iv ersity campus showiny the degree o f tr e e canopy p re s e n t in r e s i d e n t i a l a re a s . The s q u ir r e l research a re a i s o u tlin e d . EAST LANSING tlMTII □ tu m i'u lw r iw iw lin Figure 2. S t r e e t map o f th e same a re a o f E ast Lansing and Michigan S ta te U n iv e rs ity as shown in Figure 1. 23 h o u ses). While th e l o t s in some p a r ts of th e re sea rc h area are about an acre in s i z e , o th e r p a r ts o f th e area have houses very c lo se t o g e th e r . A t o t a l of 598 houses are lo c ated in th e r e s i d e n t i a l area f o r an average d e n s ity o f about th r e e houses per a c re . The p la n tin g of t r e e s along c i t y s t r e e t s by c i t y planners many y e a rs ago and th e p re s e rv a tio n of n a t u r a l l y o c cu rrin g la rg e t r e e s by housing developers has had two im portant r e s u l t s : 1) th e domination of some r a t h e r la rg e areas by two or th r e e s p ec ie s of th e same genus, and 2) th e presence o f many la r g e t r e e s forming a m oderately dense canopy covering th e e n t i r e r e s i d e n t i a l a re a in the re s e a rc h a r e a . The dominant t r e e regio ns (F igure 3) a re : a. maple region (about 90 a c re s ) composed of s i l v e r (Acer saccharinum) , sugar (A. saccharum) and Norway (A. p l a t a n o i d e s ) maples - average d . b . h . = 2 2 .5 " , b. oak region (about 45 a c re s ) composed of re d , black and white oaks (Quercus spp) - average d . b . h . » 2 1 . 5 " . c. elm region (about 45 a c re s ) composed of american elm (Ulmus am ericana) - average d . b . h . * 22.76". d. hickory reg io n (about 5 a c r e s ) composed of shagbark hickory (Carya o v a ta ) - average d . b . h . * 13.65". Most of th e r e s i d e n t s w ith in th e re se a rc h area are a s s o c ia te d with Michigan S ta te U n iv e rs ity e i t h e r in a m a in te n a n c e -c le ric a l or a d m in is tr a tiv e - p r o f e s s io n a l c a p a c ity , o r as s tu d e n t s . T heir c o operation was s o l i c i t e d by d i s t r i b u t i n g a re s e a rc h e x p lan a tio n sheet (Appendix A) t o as many of them as p o s s ib le . Many hours were spent s o c i a l i z i n g with th e r e s i d e n t s and informing them of a sp e c ts of 24 ■ H i lilii SCHOOL tfx&x Hickory 0 Roads j \ B usiness D i s t r i c t o r Open Park Area Figure 3. Dominant t r e e regions o f th e 200 a cre s q u ir r e l re sea rc h area in E a st Lansing, Michigan. ABBOTT RD HANNAH MIDDLE 25 s q u ir r e l bio log y, and th e importance of t h e i r a s s is ta n c e and goodwill to the success of th e study cannot be overemphasized. Trapping and Marking To study th e behavioral in te r a c t io n s and r e l a t e d biology of the black and fox s q u ir r e l p o p u la tio n s , i t was necessary to c ap tu re and mark them f o r in d iv id u a l r e c o g n itio n . A 50 acre area in th e southern p a r t of the re sea rc h area (Figure 4) was s e le c te d as th e tra p p in g a re a . This area included p a r ts of each of the dominant t r e e regions and was believ ed to be r e p r e s e n ta tiv e of the e n t i r e a re a. Wooden box tr a p s (Figure 5a) were used f o r c ap tu rin g s q u i r r e l s because they would provide a g re a te r degree of in s u la tio n from the n a tu ra l elements than would open wire cages. F if te e n tr a p s were b u i l t a f t e r t h a t described in W ild life Management Techniques Manual, 4th E d itio n (Schemnitz, 1980:64). The tr a p s were b a ite d with cracked corn, sunflower seeds, an d /o r acorns and hickory n u ts . To reduce th e lik e lih o o d of m o r t a l i t i e s in the t r a p s , they were checked twice a day a t midday and s h o r t l y befo re su n se t. Since s q u i r r e l s molt over summer, tra p p in g was confined mainly to f a l l and w inter to mark again in d iv id u a ls captured th e previous y ear and a lso to mark new ju v e n ile s and s u b a d u lts. To remove trapped s q u i r r e l s from th e box t r a p and r e s t r a i n them f o r i d e n t i f i c a t i o n and marking, (Figures 5b and 5 c ), two handling devices (one f o r a d u lt fox s q u i r r e l s and th e o th e r f o r th e sm aller black s q u i r r e l s and young fox s q u i r r e l s ) shaped l i k e fu nn els were E3 B e g in n in g o f Route 0 T rapp in g Area Boundary Figure 4. Location o f th e 50 acre tra p p in g area w ith in ; the E ast Lansing, Michigan, s q u ir r e l research a re a . Route followed f o r s q u ir r e l population counts i s in d ic a te d . 27 Figure 5. Equipment and procedure used in the E ast Lansing, Michigan, s q u ir r e l study (June 1977 - May 1980). (a) Box t r a p s , handling cones, weighing and tagging equipment, and f i e l d i d e n t i f i c a t i o n cards used during s q u ir r e l study. (b) Locking tra p door open so trapped s q u ir r e l can e n t e r handling cone. 28 Figure 5 ( a ) . Figure 5 (b). 29 Figure 5 (cont'd.) (c) Blowing in screened end o f tr a p to encourage s q u i r r e l to leave tr a p . (d) Nose o f black s q u i r r e l i s p ro te c te d by foam padding a t end o f handling cone w hile being e a t- ta g g e d . 30 Figure 5 (c) Figure 5 (d). 31 Figure 5 (cont'd.) (e) Bleaching black s q u i r r e l with Q -tip s and Helene C u rtis "R eady-Set-6 low" ble ac h in g s o l u t i o n . (f ) Release o f fox s q u i r r e l marked on r i g h t s id e with Nyanzol-D. Figure 5 (e) Figure 5 (f). 33 Figure 5 (cont'd.) (g) Black s q u ir r e l bleached on head and l e f t s id e i s easy to i d e n t i f y from a d is ta n c e . (h) Black s q u ir r e l calmly w aitin g in handling cone while bleach s o lu tio n begins to take e f f e c t . 34 If*- '«*r Figure 5 (h). 35 c o n s tr u c te d . The wire cone end was made of one h a lf inch mesh wire r o l l e d to f i t snuggly around a s tu f f e d fox s q u i r r e l , and an oth er made t o f i t around a s t u f f e d black s q u i r r e l . The mesh w ire of one end was c u t and fo ld e d in , and a l l o verlapping seams were sewn s e c u re ly to g e th e r with s o f t copper wire woven through th e mesh w ire . One to two inches of foam padding was s t u f f e d in s id e a g a in s t t h i s end to p r o te c t th e s q u i r r e l ' s nose from in ju r y . A canvas funnel about 24 inches long was made with one end small enough to be hand sewn t o th e open end of th e mesh wire cone. The o th e r end, with an e l a s t i c band sewn i n , was la rg e enough to f i t snuggly over th e end of a box t r a p . Two s e t s (one f o r each e a r) o f numbered monel metal s i z e 1 e a r ta g s and a p a i r of s iz e 1 p l i e r s were obtained from th e N ational Band and Tag Company of Newport, Kentucky,and used to permanently i d e n t i f y captured s q u i r r e l s (F igure 5 d ). As a s h o rt term method f o r e a s i e r i d e n t i f i c a t i o n , fox and gray s q u i r r e l s were dyed p u rp le -b la c k w ith Nyanzol-D (F igu re 5 f) ob tain ed from J . Belmar I n c . , North Andover, M assachusetts. Since Nyanzol-D would not show up on t h e i r f u r , black s q u i r r e l s were bleached orange-blonde w ith Helene C u rtis "Ready-Set-Glow" h a i r f r o s t i n g m ixture (Figure 5 e - g ) . In p lace o f th e s o lu tio n provided with th e Helene C u rtis k i t , a s o lu tio n of 240 ml of 15% hydrogen peroxide and 10 ml of c o n ce n tra te d ammonium hydroxide (58%) was added to th e f r o s t i n g powder to in c re a s e th e speed o f b le ac h in g . (A 30% hydrogen peroxide s o lu tio n was f i r s t t r i e d , but r e s u l t e d in too much skin i r r i t a t i o n and subsequent shedding of f u r by bleached s q u i r r e l s . ) A fte r applying the 36 bleach or dye w ith Q - tip s , th e canvas p o rtio n o f th e funnel was folded over the s q u i r r e l in th e cone to reduce s t r e s s i n g th e s q u ir r e l w hile i t s a t f o r about f i v e minutes f o r th e bleach or dye to ta k e e f f e c t (Figure 5 h). ( I f re le a s e d immediately a f t e r marking, th e s q u i r r e l s had th e h a b it of lic k in g o f f th e s o lu tio n b efore i t could thoroughly a f f e c t th e fu r). When not being used in th e f i e l d , th e bleaching s o lu tio n was s to re d in th e r e f r i g e r a t o r to extend th e e f f e c t i v e l i f e of th e hydrogen p erox ide. This procedure was not needed f o r th e Nyanzol-D. A system f o r i d e n tif y in g in d iv id u a l s q u i r r e l s by body markings was devised in which th e s q u i r r e l body was d iv ided in to twelve d i s t i n c t re g io n s : r i g h t sh o u ld e r, l e f t s h o u ld er, head and neck, r i g h t s i d e , l e f t s id e , mid-back, r i g h t f l a n k , l e f t f la n k , rump, t a i l b a se , m i d - t a i l and ta il tip . By marking each s q u ir r e l w ith a combination of one, two or th r e e body re g io n s , hundreds of s q u i r r e l s could e a s i l y be in d iv id u a lly i d e n t i f i e d a t a d is ta n c e w ith b in o c u la rs . Since fox and black s q u i r r e l s were marked d i f f e r e n t c o lo r s , th e same body region combinations could be used tw ic e , th e re b y doubling th e number of s q u i r r e l s t h a t could be marked. Edge-punched card s a f t e r t h a t describ ed in W ild life Management Techniques Manual, 4th E d itio n (Schemnitz, 1980:46) were used as f i e l d i d e n t i f i c a t i o n c a r d s , except t h a t 3x5 index cards were used in s te a d of keysort cards (F igu re 6 ) . Immediately a f t e r a s q u i r r e l had been captured and marked, th e a p p ro p ria te holes were notched f o r th e s p e c ie s , sex and body regio ns marked. Ear ta g number was noted and such th in g s as changes in body markings due to lo s s or regrowth of f u r , 37 w\n/w\r\jJ] Q) U IB CO 3 ec to• DC to■ _1 or co« Q£ Lt- L.Flan T ail Base ( MASTER CARD Female Tail Mid. ( Black Keep on top o f deck Tail Tip C #6 Black Male 1/15/78 Head and back bleached 2 /2 7 /7 8 B elieved n e stin g in oak tr e e in f r o n t o f 651 H ill c r e s t Figure 6. Edge-punched s q u i r r e l i n d e n t i f i c a t i o n cards used f o r E a s t Lansing, Michigan, s q u i r r e l stud y. 38 pregnant or l a c t a t i n g c o n d itio n , o r inform ation on n e st lo c a tio n s were recorded under remarks. The pack of cards of a l l liv in g marked s q u i r r e l s (card s f o r recovered dead s q u i r r e l s were removed) were always c a r r ie d in th e pocket while in th e f i e l d , along with a s h o rt n a il to serv e as th e card e x t r a c t o r . F ie ld O bservations All f i e l d o b serv atio n s were recorded on a p o rta b le c a s s e t t e tape re c o rd er and l a t e r tr a n s f e r r e d to 5x8 index c a rd s . Tours through the re s e a rc h are a by f o o t or b ic y c le were made under a l l weather c o n d itio n s a t l e a s t th re e times during each month f o r each two hour period of d a y lig h t. During th e 36 months of th e s tu d y , some ob serv atio n s of th e s q u i r r e l s were made almost every day. Over 4000 hours were spent g a th erin g d a ta , averaging about 30 hours/week. During a to u r of th e re se a rc h a re a , th e i d e n t i f i c a t i o n number and/or sp ec ie s of observed s q u i r r e l s were recorded along with th e tim e, d a te , lo c a tio n and a c t i v i t y in which th e s q u i r r e l s were engaged. In c id e n ta l o b serv atio n s were a lso recorded while I was engaged in o th e r re sea rc h a c t i v i t i e s in th e a re a . Such a c t i v i t i e s involved mapping dominant t r e e region s and th e d i s t r i b u t i o n of supplemental fe e d e rs or overw inter l e a f n e s t s , checking tr a p s and marking or weighing s q u i r r e l s , conducting s q u ir r e l counts f o r population e s tim a te s , to u rin g th e area f o r sp rin g l i t t e r counts or s q u ir r e l m o r t a lit y reco very , g a th erin g f a l l mast samples or observing fe e d in g on n a tu ra l food sources or a t supplemental f e e d e r s , and determ ining th e number of s q u i r r e l s in a w in te r n e stin g ag g re g atio n . 39 D is tr ib u tio n of Black S q u ir r e ls A p re lim in a ry survey conducted in th e sp rin g of 1977 rev ealed t h a t most of th e black s q u i r r e l s were r a t h e r co ntin u ou sly d i s t r i b u t e d throughout th e East Lansing a re a . However, a number of discontinuous clumps of black s q u i r r e l s were lo c ated or re p o rte d in woodlots and neighborhoods a good d is ta n c e from th e East Lansing population of black sq u irre ls. To determine th e boundaries of th e main body of th e black s q u ir r e l popu lation and a ls o to lo c a te is o la te d groups of black s q u i r r e l s in th e G re ater Lansing a r e a , a news r e le a s e about th e black s q u i r r e l study was prepared by the Michigan S ta te U n iv e rs ity O ffice of Inform ation S erv ices (Appendix B). This newspaper r e le a s e requested inform ation from a re a r e s id e n ts about the presence of black s q u i r r e l s in t h e i r neighborhoods. P u b lic a tio n of t h i s a r t i c l e in local newspapers and an appearance on a lo c al ra d io s t a t i o n (WKAR) t a l k show r e s u lte d in many l e t t e r s and phone c a l l s from in te r e s t e d in d iv id u a ls . Each lead was followed by a d is c u s s io n with th e r e s id e n t to determine when th e black s q u i r r e l s f i r s t appeared in the neighborhood and approximately what p o rtio n of th e p re s e n t s q u ir r e l population was b la c k . The presence of black s q u i r r e l s in a l l re p o rte d neighborhoods was l a t e r v e r i f i e d by f i e l d o b se rv a tio n . Reports of black s q u i r r e l s being p re sen t on p a r t s of th e Michigan S ta te U n iv e rsity campus north of th e Red Cedar River were in v e s tig a te d by p e rio d ic system atic to u rs through t h i s area and a ls o through the Sanford Natural Area on the south s id e of th e r i v e r . 40 Population Estim ates The composition of th e s q u ir r e l popu latio n was measured each f a l l and w in te r. S q u irre l counting walks (tagged and untagged, black and fox s q u i r r e l s ) were conducted through the tra p p in g area follow ing a predetermined course (F ig ure 3) t h a t would minimize th e lik e lih o o d of counting th e same s q u ir r e l tw ic e . The walks were taken during peak s q u ir r e l a c t i v i t y time in th e morning on sunny and mild days to in c re a s e th e p r o b a b i l i t y of o b ta in in g a count which a c c u ra te ly re p re se n te d th e tr u e pop ulation compositon. Population e stim ate s were made using B a i le y 's modified formula of th e Petersen e stim a te (Begon, 1979:7): where n is the t o t a l number of s q u i r r e l s observed, r is th e number of marked s q u i r r e l s in th e p o p u la tio n , and m i s the number of marked s q u i r r e l s observed. The formula f o r the stan dard e r r o r of B a ile y 's e stim a te i s : (m+l)2(m+2) N a ta li ty N a ta li ty was measured by determ ining th e s iz e of th e l i t t e r s as they emerged from the n e s t during d a ily morning to u rs of th e e n t i r e re sea rc h area in A pril and May. Dates of n e s t- le a v in g were noted f o r marked females with l i t t e r s th e f i r s t day th ey were seen. Unmarked 41 fem ales with l i t t e r s were a ls o noted as to lo c a tio n and probable leafnest s i t e . Any unmarked females w ith l i t t e r s observed in th e same general a re a on subsequent days were d isre g ard ed and considered as having been a lre a d y re c o rd ed , u n le ss th e female and l i t t e r could d e f i n i t e l y be i d e n t i f i e d by d i f f e r e n t body markings or c o lo r a t i o n . To avoid do ub le -c o u n tin g , l i t t e r s appearing during th e summer and f a l l were recorded only when th e i d e n t i t y of th e female and l i t t e r was d e fin ite . Since f u r was molted during t h i s tim e, very few females could be d e f i n i t e l y i d e n t i f i e d and thus few l i t t e r s were record ed . M o rta lity M o rta lity was measured by making evening to u rs of re s e a rc h area roads to recover s q u i r r e l s k i l l e d by c a r s . Inform ation was a ls o obtained from r e s i d e n t s re g a rd in g any s q u ir r e l m o r t a l i t y by household p ets they observed, o r by any o th e r p re d a to rs known to be p re s e n t in th e a re a . s tu d y . R esidents a ls o a s s i s t e d by re co v erin g s q u i r r e l k i l l s f o r th e The presence o f d is e a s e s in th e s q u i r r e l p op u la tio n was lim ite d t o notin g th e occurrence of e c t o p a r a s i t e i n f e s t a t i o n s on handled or observed i n d iv id u a ls . Movements D aily A c tiv ity Seasonal d if f e r e n c e s in th e d a i l y a c t i v i t y p a tte r n s of black and fox s q u i r r e l s were determined in sp rin g (March, A pril and May), summer (June, J u ly and A ugust), f a l l (September, October and November), and w in te r (December, January and F e b ru a ry ). At th e end of th e s tu d y , d a ta from a l l th r e e y e a rs were combined f o r each of th e fo u r seasons ( i . e . , 42 d a i l y a c t i v i t y p a tte r n s f o r each season was a c t u a l l y a t o t a l of nine months of o b s e r v a tio n s ) . The d a y lig h t hours were divided in to two hour tim e perio ds (b e fo re 7 AM, 7-9 AM, 9-11 AM, 11 AM-1 PM, 1-3 PM, 3-5 PM, and a f t e r 5 PM). Periods of time spent in th e f i e l d making to u r s of th e re s e a rc h area or conducting ro u tin e a c t i v i t i e s a s s o c ia te d with the s tud y were considered o b se rv a tio n p erio ds during which s q u i r r e l s could p o t e n t i a l l y be observed. O bservation p eriod s v a rie d in length and could include a number of d a y lig h t time p e rio d s . For example, o b se rv a tio n s made from 7:30 AM to 2:30 PM would count as ob serv atio n perio ds in th e time p erio ds of 7-9 AM, 9-11 AM, 11 AM-1 PM and 1-3 PM, o r a t o t a l of fo u r o b serv atio n p e r io d s ) . While th e number of o b serv atio n perio ds during each of the d a y lig h t time p eriod s f lu c tu a te d each month, th e t o t a l number of o b serv atio n p e rio d s during each d a y lig h t time period were comparable, season to season, when t o t a l e d f o r the e n t i r e s tu d y . (The only exception was during w in ter when the e a r l y morning and l a t e evening tim e period s were dark and had no observed s q u ir r e l a c t i v i t y ) . The average number of s q u i r r e l s observed during each o b serv atio n period of each d a y lig h t time period was used to p lo t th e d a ily a c t i v i t y p a tte r n f o r each season. Home Range To determine th e minimum home ranges of black and fox s q u i r r e l s , th e lo c a tio n s of each marked s q u i r r e l observed w hile making to u rs of th e re sea rc h area or conducting ro u tin e a c t i v i t i e s a ss o c ia te d with the study were p lo tte d on sca le d down maps of th e re s e a rc h a re a . To o b ta in an a c c u ra te r e p r e s e n ta tio n of th e are a u t i l i z e d throughout th e y e a r , 43 only th o se in d iv id u a ls captured and/or observed a t l e a s t f i v e times during each season were used. Food A v a i l a b i l i t y Food a v a il a b le to th e s q u i r r e l s c o n sis te d of t h a t n a t u r a l l y o c c u rrin g on v e g e ta tio n in th e area and t h a t su p plied by r e s i d e n t s a t supplemental f e e d e r s . O bservations were made on th e s q u i r r e l s ' feed in g h a b its to a s c e r ta in which foods were most h e av ily used during v a rio u s times of th e y e a r . Since th e mast crop i s th e major n a tu ra l food source a v a il a b le to s q u i r r e l s in th e f a l l and through much o f th e w in te r , measurements of th e mast abundance were made. Each f a l l , th r e e 1 m2 samples were gathered under th e same randomly s e le c te d oak, h ic k o ry , maple and walnut t r e e s . The d i s t r i b u t i o n o f supplemental f e e d e rs was mapped and o b serv atio n s made on t h e i r use by s q u i r r e l s to determ ine th e s q u i r r e l s ' use of them as a food source during w in te r. I n t e r s p e c i f i c A ggressive Behavior The a g g re ssiv e i n t e r a c t i o n s between black and fox s q u i r r e l s were c a r e f u l l y re c o rd ed . The u n it measuring a g g re ssiv e i n t e r a c t i o n s was th e " e n c o u n te r," defin ed as th e approach of two in d iv id u a ls near enough to each o th e r so as to produce a behavio ral respo nse. Encounters were c l a s s i f i e d in to fo u r ty p e s , based on th e s e v e r i t y of th e i n t e r a c t i o n : 1. Tolerance - each s q u ir r e l seemed aware of th e o t h e r 's proxim ity but did nothing to cause th e o th e r t o move f a r t h e r away 2. Mild Aggression - one s q u ir r e l c h a tte re d s o f t l y and/or f l i c k e d i t s t a i l , causing the second s q u ir r e l to move away 44 3. Moderate Aggression - one s q u ir r e l c h a tte r e d and f l i c k e d i t s t a i l and/or made a s h o rt rushing charge ( l e s s than f iv e f e e t ) causing th e second s q u ir r e l to move away 4. Severe Aggression - much c h a tt e r i n g and/or t a i l f l i c k i n g and a long chase (over f i v e f e e t ) by one s q u ir r e l causing th e second s q u ir r e l to move away. An index of aggression was computed using the follow ing r a t i n g s : to le ra n c e = 0 mild aggression = 1 moderate aggression » 2 severe aggression = 3 Weather and Winter Weight F lu c tu a tio n s Weather data were obtained from the Lansing Weather Bureau f o r the months of November through March f o r the Winters of 1977-78, 1978-79, and 1979-80 t o document th e s e v e r i t y of w in te rs during th e s tu d y . Special a t t e n t i o n was given to those f a c to r s which put ph y sio lo g ic al s t r e s s upon th e s q u i r r e l s , such as measurements on the s e v e r ity of the c o ld , amounts of snowfall and q u a n tity of snowcover on the ground. From October 27, 1979 t o February 22, 1980, in te n s iv e tra p p in g and weighing of s q u i r r e l s was conducted to measure the weight f lu c tu a tio n s experienced during t h i s most s t r e s s f u l time of the year f o r the sq u irre ls. Data obtained would be used as an i n d i r e c t r e f l e c t i o n of the ph y sio lo g ical co n d itio n of the in d iv id u a ls handled. 45 Nests With r e l a t i v e l y few dens a v a ila b le to th e s q u i r r e l s {old t r e e s w ith many hollow c a v i t i e s were o fte n considered s a f e ty hazards in the urban areas and th e r e f o r e cu t down), le a f n e s ts were th e most common form of n e s tin g . (A few s q u i r r e l s nested in homes, but they were often q u ic k ly trapped out by th e r e s i d e n t s ) . Since w inter is th e e a s i e s t time to lo c a te l e a f n e sts and dens and also to d i f f e r e n t i a t e between abandoned and m aintained n e s t s , th e lo c a tio n o f overw intering l e a f n e s ts and the sp ec ie s of t r e e s they were in were mapped during the Winters of 1978-79 and 1979-80. The d i s t r i b u t i o n of le a f n ests was used to determine whether the s q u i r r e l s p re fe rre d n e stin g in one sp ec ie s of tr e e or in one of the dominant t r e e re g io n s . The s iz e s of w in ter n e st aggregations were determined based on the follow ing o b s e rv a tio n . When n e stin g in groups during w in te r, a s q u ir r e l o fte n h e s it a te d a t the n e st en trance and exchanged some muted c a l l s with any occupants of th e n e st ( t h i s c a l l i n g has a ls o been observed by Bakken, 1959:403). A fter e n te rin g th e n e s t, t h i s in d iv id u a l and th e o th e r occupants u s u a lly emerged and ran around the t r e e f o r a few m inutes, then a l l would r e e n te r the n est f o r th e n ig h t. S q u ir r e ls e n te r in g a n e st w ithout h e s i t a t i n g to c a ll and not reemerging l a t e r , were considered to be n e stin g alone. On January and February evenings (about 5-6 PM) during a l l th re e w in ters of the stu dy , th e l a s t s q u ir r e l re le a s e d from the tr a p s was followed to i t s n e st to determine how many in d iv id u a ls were n e stin g to g e th e r . The data were compiled f o r 46 each w inter to determine whether th e re was a d iff e r e n c e between black and fox s q u i r r e l s in th e average w inter n e s tin g aggregation s i z e . I n te r a c tio n s with People Impromptu d is c u s s io n s with r e s id e n ts in th e re sea rc h area were o fte n used to o b ta in t h e i r opinions on th e in tro d u c tio n of black s q u i r r e l s in to East Lansing, how black s q u i r r e l s ' behavior compared with t h a t of th e fox s q u i r r e l s , and a lso anecdotes concerning problems with and the behavior of s q u i r r e l s . The opinions of re s id e n ts o u ts id e th e research area who responded to the newspaper a r t i c l e s or ra d io interview were a lso obtained when they were interview ed about th e presence of black s q u i r r e l s in t h e i r neighborhoods. RESULTS D is tr ib u tio n o f Black S q u ir r e ls The area occupied by black s q u i r r e l s , as of f a l l 1981, included th e major p o rtio n in East Lansing (Figure 7) and eleven i s o la te d p o p u la tio n s lo c a te d throughout th e G re ater Lansing area (Figure 8 ) . Black s q u i r r e l s were common throughout th e o ld e r r e s i d e n t i a l areas of East Lansing from Park Lake Road on th e e a s t t o Frandor Shopping C enter on th e w est. The presence of th e Shopping Center and the superhighways (US 127 and 1-496) appeared to have impeded f u r t h e r sp read in g to th e w est. While black s q u i r r e l s were known to be p re s e n t n orth of Saginaw S t r e e t between Coolidge and Abbott Roads, th e e x te n t of t h e i r p e n e tr a tio n in to th e newer housing developments th e r e was unknown. Not observed to th e north o f Towar Park, black s q u i r r e l s were found as f a r n o r th e a s t as Walnut H ills Country Club. T h e ir presence in th e new s u b d iv isio n s between th e s e p o in ts was not a s c e r ta in e d . Only in th e l a s t few y e a rs was th e r e any movement of black s q u i r r e l s to th e south of town. They were common near Red Cedar School and some were seen along th e Red Cedar R iver near U n iv e rs ity V illa g e . Two black s q u i r r e l s were re p o rte d near th e Michigan S ta te U n iv e rs ity baseb all diamond in th e t r e e s lin in g th e Red Cedar R iv er. In th e F a ll of 1980, a lone black s q u i r r e l was n e s tin g in th e sugar maple west of Cowles 47 snrnrz Figure 7. D is tr ib u tio n o f black s q u i r r e l s in the E a st Lansing, Michigan, area as o f f a l l 1981. I s o la te d p o p ulation o f black s q u i r r e l s in Abbott Road Park a ls o in d ic a te d . 49 f lO ffi L A M M flL O L 'P R A R IA ? • M M H IT I P •• KIT H 3 P E •• OK E M O S • •••• holt holt r p b p C ity Limits S quirrel Research Area I s o la te d Populations of Black S q u irr e ls Figure 8. Locations o f th e eleven i s o l a t e d p o p ulation s o f black s q u i r r e l s discovered in th e G re ater Lansing, Michigan a r e a , as o f f a l l 1981. 50 House and was f r e q u e n tly observed near Beaumount Tower. By th e F a ll of 1981, th r e e black s q u i r r e l s were on th e north campus and a fo u r th was l a t e r observed across th e l i b r a r y brid g e near th e stadium. The f i r s t black s q u i r r e l in Sanford N atural Area was observed during th e F a ll of 1978 and by th e F a ll of 1981 a t l e a s t f i v e were in th e p re s e rv e . Below are th e lo c a tio n s and d e s c r ip ti o n s of th e eleven i s o la te d p o p u latio n s of black s q u i r r e l s discovered in t h i s study: 1. Abbott Road Park - unknown number of black s q u i r r e l s re le a s e d by agents of th e Ingham County Animal Control Department. 2. 16961 S. Nichols Road (1/2 m ile n o rth of th e C lin to n County l i n e ) - two black s q u i r r e l s f i r s t appeared in l a t e sp rin g 1981 in th e yard of Ted and J u l i e Wycoff. 3. C ity of Okemos - a la rg e p o p ulation e s ta b lis h e d south of Grand River Avenue f o r a t l e a s t f iv e y e a r s . 4. Grand River Avenue and Cornell Road, south of Ethel Road - a t l e a s t two black s q u i r r e l s appeared r e g u l a r l y a t th e fe e d e r of Mr. Roger C lark . 5. Toomey Woodlot, Michigan S ta te U n iv e rs ity - p o pu lation e s ta b lis h e d in 1972-73 by r e l e a s e of about twenty in d iv id u a ls by East Lansing r e s i d e n t s . 6. Cedar S t r e e t - J o l l y Road - Logan S t r e e t - M ille r Road block — black female #69 tagged in East Lansing on December 11, 1978 captu red by Lansing Vector Control on October 10, 1979 a t V alencia and South Logan S t r e e t ; a few black s q u i r r e l s observed in a small woodlot on South Washington about 1/4 mile north of M ille r Road; two black s q u i r r e l s observed running 51 across J o l l y Road j u s t west of Cedar S tr e e t - a l l of th e se may be p a r t of a small popu lation s c a tte r e d over a la rg e area or th e r e s u l t of numerous se p a ra te in tr o d u c tio n s . 7. W alter French School area - many black s q u i r r e l s re p o rte d by s tu d e n ts to th e south and west of scho o l, but only a few a c t u a l l y observed in 1980. 8. P o tte r Park Zoo - many black s q u i r r e l s re le a s e d by Ingham County Animal Control Agents. 9. Groesbeck Golf Course - many black s q u i r r e l s rep orted to west in Bancroft and P o rte r P arks, but only a few observed in 1979. 10. West of A irp o rt (6800 Grand River Avenue about 1/2 mile e a s t of 1-96) - Mrs. Clark liv e d in house on 10 acres of land f o r 38 y ears and f i r s t black s q u i r r e l appeared a t fe e d er in June, 1981. 11. Sandhill Road - two orphaned black s q u i r r e l s tagged by Marti Schneiderman and re le a s e d in a p r iv a te woodlot in F a ll of 1981. Population Estim ates Black and fox s q u i r r e l popu latio n e s tim a te s , based on counts made during th re e w in ters o f th e stud y , ranged f o r th e most p a r t between 30 and 70 in d iv id u a ls (Table 1; Figure 9 ). Due to th e lack of marked fox s q u i r r e l s during th e Winter of 1977-78, only th e population estim ate s of the black s q u ir r e l p o p u lation could be c a lc u la te d . However, th e fox s q u ir r e l p o p u latio n was believ ed to have been about equal to th e black 52 Table 1. Population e s tim a te s of black and fox s q u i r r e l s in East Lansing, M ichigan,using B a ile y 's modified formula of the P etersen e s tim a te . E stim ates were based on s q u ir r e l counts obtained by walking a predetermined course through a 50 acre tra p p in g area in th e re sea rc h a re a . BLACK Dates of S q u irre l Counts 1977-78 Dec 11 Dec 17 Dec 23 Jan 11 Jan 18 Jan 23 Feb 9 Feb 14 Feb 23 1978-79 Oct 20 Oct 31 Nov 7 Nov 30 Dec 10 Dec 16 Dec 17 Jan 12 Jan 27 Feb 3 Feb 20 Feb 28 ADr 3 Apr 14 Apr 20 1979-80 Oct 31 Nov 18 Dec 10 Dec 19 Jan 9 Jan 25 Feb 4 Feb 18 Aor 13 Aor 20 Observed Marked (m) - Total Marked in Observed* population (n) (r) 4 10 9 15 12 19 22 17 22 11 1 1 2 4 6 5 4 6 4 3 5 5 1 2 12 13 14 11 18 22 17 12 16 11 8 13 14 3 6 6 30 28 21 26 29 26 17 ZO 22 23 - 1 1 2 3 3 7 lo 8 10 10 10 8 9 11 11 SQUIR RE L S Population Estimate Standan Error - - - 2 4 6 - - '""7 16 26 40 4o ' 8 15 18 36 43 43 5 5 11 14 15 15 35 38 44 53 49 45 39 36 36 34 35 38 30 35 re 15 15 15 15 15 18 15 16 29 29 29 29 29 33 ‘ " 71 69 ................... “ 34 34 "" 'r e . 7 ” 2 0 ' .... 19.1 18.6 14.5 13.9 12.5 9.9 11.2 ~ ll.3 10.0 11.0 12.2 13.2 71 71............... 79 71 66 71" 65 68 8 .6 13.8 T8". 4' 16.4 14.2 11.6 13.5 22.0 15.0 17.2 15.8 18.2 15.8 14.8 15.6 12.5 i'3.3 ' 53 Table 1 (cont'd.) FOX Dates of S q u ir re l Counts 1977-78 Dec 11 Dec 17 Dec 23 Jan 11 Jan 18 Jan 23 Feb 9 Feb 14 Feb 23 Observed Marked (m) - 1 1 1 Total Observed (n) 13 8 12 10 9 15 13 15 13 SQUI RRELS Marked in population (r) Population Estim ate Standan Error - - - - - - - - - - - - - - * - - - 2 3 3 14 24 21 1 2 2 6 15 3.2 8.1 TS "O ' 1'7.3 — 7: 5 " 13.0 11.2 1978-79 Oct 20 Oct 31 Nov 7 Nov 30 Dec 10 Dec 16 Dec 17 Jan 12 Jan 27 Feb 3 Feb 20 Feb 28' Apr 3 Apr 14 Apr 20 1979-80 Oct 31 Nov 18 Dec 10 Dec 19 Jan 9 Jan 25 1 1 1 1 2 2 2 3 3 2 2 1 3 1 1 2 4 4 7 11 14 14 12 21 16 17 19 20 14 12 7 16 5 6 6 7 1 7 1 1 1 7 7 7 1 18 4 16 12 17 17 20 21 24 26 26 26 9 13 "2'1 23 9 2o 4 7 Feb 18 Apr 13 Apr 20 8 11 8 12 15 21 16 feb 5 " 33 44 40 42 35 37 35 30 28 30 21 -? g . 25 48 47 48 44 39 46 48 49 20.4 18.0 19.2 14.0 14.8 15.7 13.3 14.0 11.6 9.9 12.0 11.6 ~ IO 15.6 12.4 rr;i 9.6 8.1 9.7 8.9 10.7 P O P U L A T I O NE S T I M A T E S U I N T E R O F 1 9 7 7 -7 8 1 0 0 9 0 8 0. 7 0 8 0 T T 5 0 4 0■ T ? * • 3 0. 2 0 T 'i1 1 0‘ 1 2 58 2 2 O e c J a n Figure 9. W I N T E R O F 1 9 7 9 -8 0 W H I T E R O F 1 9 7 8 -7 9 m B la c kS q u ir r e ls F o xS q u ir r e ls II u 1 I H a r 1 A p rO c tN o v D e c a r J a n F e b H A p r E stim ates (+ S E) o f black and fox s q u i r r e l p o p u la tio n s in a 50 a c r e tra p p in g a re a in E a st Lansing, Michigan, f o r th e W inters o f 1977-78, 1978-79 and 1979-80. Due to a lack o f marked fox s q u i r r e l s , only black s q u i r r e l p o p u la tio n e s tim a te s were c a lc u la te d f o r 1977-78. 55 s q u i r r e l s t h a t w in te r , because th e y were observed in th e s q u ir r e l counts about as o fte n as th e black s q u i r r e l s . The black and fox s q u i r r e l p o p u la tio n s appeared comparable f o r th e Winters of 1977-78 and 1978-79, being near 40 in d iv id u a ls f o r each sp ec ie s w ith in th e 50 acre tra p p in g a r e a . This was a t o t a l s q u i r r e l d e n s ity of 1 .6 / a c r e . During th e Winter of 1979-80, th e fox s q u i r r e l p o p u la tio n was near 50 in d iv id u a ls and th e black s q u i r r e l p o pu lation had in c re ase d to near 70 i n d iv id u a ls . This was a t o t a l s q u ir r e l d e n s ity of 2 . 4 / a c r e . T r a p - r e tr a p methods of po pu la tio n e stim a tio n were not used because th e t r a p s appeared to be b ia se d , c a p tu rin g more black s q u i r r e l s than would re ason ab ly be e x p ected. C hi-square a n a ly s is (Table 2) comparing th e tra p p in g success (both f i r s t - t i m e c a p tu re s and subsequent r e c a p tu r e s ) during th e study with th e expected success based on th e p ro p o rtio n s of black and fox s q u i r r e l s observed in th e pop ulatio n counts in d ic a te d t h a t th e p r o b a b i l i t y of o b ta in in g th e s e r e s u l t s by chance was very low f o r re c ap tu red animals during a l l th re e w in te rs and f o r f i r s t - t i m e c a p tu re s during th e Winters of 1977-78 and 1978-79. Only during th e Winter of 1979-80 was th e p r o b a b i l i t y of o b ta in in g th e f i r s t - t i m e c a p tu re s very h ig h , and i t is suspected t h a t th e mildness of t h i s w in ter (see Table 7) in flu enced th e se r e s u l t s . During most of th e s tu d y , th e black s q u i r r e l s were trapped with a d is p r o p o r ti o n a te ly g r e a t e r frequency than th e fox s q u i r r e l s . Table 2. Comparison o f tr a p p in g su ccess o f s q u i r r e l s in E ast Lansing, Michigan*with expected s u ccess based on black and fox s q u i r r e l p ro p o rtio n s observed in th e p o p u la tio n on s q u i r r e l counts ( d a ta summarized from Table 1 ). Year Black Fox T otal Black Fox T otal Black Fox T o tal 19771978 19781979 19791980 T otal Number of S q u irrels Observed 137 108 245 190 204 394 239 175 414 %o f Total Observed 55.9 44.1 -----48 .2 51.8 ------ 57.7 42.3 ------- ’ Number of S q u ir r e ls Captured F irst Recap­ C aptures t u r e s 44 33 11 4 44 48 20 20 9 8 29 28 40 63 30 26 70 89 Number of S q u ir r e ls Expected to be captured F irst Recap­ Captures t u r e s 25 27 19 21 44 48 14 13.5 15 14.5 29 28 40 51 30 38 70 89 P ro b ab ility of O btaining th e s e R e s u lts by Chance 1 s t C aptures .025>P >.01 Recap. .005>P 1 s t Captured .05>P>.025 Recap. .025>P>.01 1 s t C aptures P>.95 R ecaptures .025>P >01 57 N a ta li ty L i t t e r s iz e s f o r th e black s q u i r r e l s during th e Springs of 1978, 1979, and 1980 appeared to be la r g e r than t h a t of fox s q u i r r e l s , and f o r both sp e c ie s l i t t e r s iz e f o r th e Spring of 1979 appeared to be sm aller than in 1978 or 1980 (Figure 10). T - t e s t s on d iff e r e n c e s between th e means, however, in d ic a te d th a t 1) average l i t t e r s iz e f o r black s q u i r r e l s showed no s i g n i f i c a n t d iff e r e n c e s y ear to y e a r, 2) th e average fox s q u ir r e l l i t t e r f o r th e Spring of 1979 was s i g n i f i c a n t l y (.001 le v e l ) sm aller than in 1978 or 1980, 3) average black and fox s q u ir r e l l i t t e r s iz e s were not s i g n i f i c a n t l y d i f f e r e n t in the Springs of 1978 or 1980, but 4) in 1979, th e average black s q u ir r e l l i t t e r was s i g n i f i c a n t l y (.001 le v e l ) la r g e r than the average fox s q u ir r e l litte r. The f i r s t appearance of l i t t e r s out of th e n e st occurred l a t e r in th e Spring of 1979 than in 1978 or 1980 (Figure 11). Using April 20 as th e f i r s t day l i t t e r s appeared, t - t e s t s on d iff e r e n c e s between th e means in d ic a te d th e average day of emergence during th e Spring o f 1973 was s i g n i f i c a n t l y (.001 le v e l ) l a t e r f o r both th e black and fox s q u i r r e l s than was tr u e f o r th e Springs of 1978 or 1980. There was no s i g n i f i c a n t d iff e r e n c e in th e average day of emergence between black and fox s q u ir r e l l i t t e r s in the Springs of 1978 or 1980, but th e black s q u ir r e l l i t t e r s in th e Spring of 1979 emerged s i g n i f i c a n t l y (.001 le v e l ) e a r l i e r than th e fox s q u ir r e l l i t t e r s . B la c k A v era g e = 3 .4 0 Fox A v era g e =2.92 B la c k A v era g e = 2 .8 2 Fox A v era g e =1.75 B la c k A v er a g e = 3 .3 3 Fox A v er a g e =3.26 Number of L itte r s tn oo 1 Number o f y o u n g i n l i t t e r S p r in g 1978 Figure 10. Number o f you n g i n l i t t e r S p r in g 1979 2 3 4 5 Number o f y o u n g i n l i t t e r S p r in g 1980 Spring l i t t e r s iz e s of-black and fox squirrels in East Lansing, Michigan, for 1978, 1979 and 1980. S p rin g m m 1980 ± 3 1 i. m 11 4 | 2 H 1 1 1 1 1 ■ II - I ________L . I I I 1 m . I S p rin g 1979 -I I I I I I 28 30 I L. ■ ■ I x i. 8 10 12 i « i ■ ■ i i ■ i 14 16 18 20 22 24 26 28 30 S p rin g 1978 20 22 24' April p ii | | Figure 11. 26 2 6 Ma y B lack S q u ir r e l L i t t e r (number in d i c a t e s l i t t e r s i z e ) Fox S q u ir r e l L i t t e r (number in d i c a t e s l i t t e r s i z e ) Dates on which black and fox s q u i r r e l l i t t e r s in E a s t Lansing, Michigan, were f i r s t observed o u t o f the n e s t in A pril and May o f 1978, 1979 and 1980. 60 M o rta lity During th e stu d y , 29 dead s q u i r r e l s were recovered in th e re s e a rc h a re a: 12 black and 12 fox s q u i r r e l s were k i l l e d by c a r s ; 3 black s q u i r r e l s were k i l l e d by c a t s ; and 2 black s q u i r r e l s were k i l l e d in a c c id e n ts . The g r e a t e s t p a r t of th e c ar m o r t a l i t y (17/24) occurred among ju v e n ile s r e c e n t l y out of th e n e s t . Few c ar k i l l s occurred when snow covered th e ground. Most of th e s q u i r r e l s handled during th e study had f l e a s . These were most abundant on th e s q u i r r e l s during February and March. Examination o f th r e e l e a f n e s ts blown down from t r e e s rev ealed la rg e numbers of f l e a s (50-100) in each n e s t . S a rc o p tic mange and bald areas on th e body were common during l a t e w in te r . Sometimes 50-80% o f the body was b are with raw b leeding areas obvious. Movements D aily A c tiv ity Throughout th e y e a r , black and fox s q u i r r e l s were s im ila r in the p a tte r n of d a i l y a c t i v i t y , showing high le v e l s of a c t i v i t y from 9 AM 5 PM (Table 3; Figure 12). While black s q u i r r e l s showed a s l i g h t l y g r e a te r le v el of a c t i v i t y in th e morning and l a t e afternoon than did th e fox s q u i r r e l s in s p r in g , t h i s d if f e r e n c e was not s t a t i s t i c a l l y sig n ific a n t. Home Range During t h i s s tu d y , fo u r black s q u i r r e l s and th r e e fox s q u i r r e l s were observed o fte n enough over a long enough time span to p lo t t h e i r minimum home ranges (F ig u re s 13, 14, and 15). The m a jo rity of marked Table 3. D aily a c t i v i t y o f A c t i v i t y le v e l i s t i o n s during each Time c o rre c te d to b lack and fox s q u i r r e l s in E ast Lansing, M ichigan, d urin g each season . based upon th e average number o f s q u i r r e l s s ig h te d w hile making o bserva­ two hour d a y lig h t tim e p eriod durin g e n t i r e stud y (June 1977-May 1980). E astern Standard Time. SPRING <-7 D aylight 7-9 9-11 T ime llam-1 1-3 P e rio d s 3-5 5-» am am am pm pm pm pm BLACK S QUI Total T o tal Number Number of of O bservation S q u irrels Observed P e rio d s 26' 29 35 166 32 731 541 29 30 551 744 36 33 177 SQUI RREL R R E L S _________ F O X Total Average Total Number of Number Number S q u ir r e ls of of Observed O bservation S q u ir r e ls Observed P erio d s Per Period .90 21 29 4.74 142 35 22.84 554 32 18.66 509 29 18.37 536 30 20.67 447 36 5.36 139 33 S Average Number of S q u irrels Observed Per Period .93 4.06 17.31 17.55 17.87 12.42 4.21 Table 3 (cont'd.) SUMNER <-7 D ay lig h t 7-9 9-11 Time llam-1 1-3 P erio d s 3-5 5 -> am am am pm pm pm pm BLACK S Q U I R R E L S ____________ F O X T otal Total Average Total Number Number Number of Number of of S q u ir r e ls of S q u ir r e ls O bservation Observed S q u ir r e ls Observed Per Perio d P erio d s Observed 262 32 8.19 248 1104 28.30 39 53 1059 41 25.83 1192 956 38 25.16 1040 902 34 26.53 827 1007 37 27.22 834 44 18.29 805 560 S QUI RRELS Total Average Number of Number of S q u irrels Observation Observed Per Period P erio d s 32 7.75 39 24.43 41 29.07 38 27.37 34 24.32 37 22.54 44 12.73 Table 3 (cont'd.) FALL < -7 D aylight 7-9 9-11 Time llam-1 1-3 P erio d s 3-5 5 -> am am am pm pm pm pm BLACK S QUI Total Total Number Number of of O bservation S q u irrels Observed P erio d s 141 30 636 31 1074 36 35 835 712 32 32 761 360 41 R R E L S ____________ F O X Average Total Number of Number S q u ir r e ls of Observed S q u ir r e ls Per Period Observed 4.70 157 20.52 587 29.83 1092 23.86 857 22.25 698 23.78 647 8 .78 417 S QUI RR Total Number of O bservation P e rio d s 30 31 36 35 32 32 41 ELS Average Number of S q u ir r e ls Observed Per Period 5". 23 18.94 30.33 24.49 21.81 20.22 10.17 Table 3 (cont'd.) WINTER < rl am D aylight 7-9 9-11 Time llam-1 1-3 P erio d s 3-5 5-> am am pm pm pm pm BLACK S QUI T otal Total Number Number of of O bservation S q u irrels Observed P erio d s 6 0 17 92 27 291 574 29 543 30 27 272 14 0 R R E L S ________________F O X Average T otal Number of Number S q u ir r e ls of Observed S q u ir r e ls Per Period Observed 0 0 5.41 77 10.98 248 19.79 591 18.10 496 9.71 323 0 0 S QUI RR Total Number of O bservation P erio ds 6 17 27 29 30 28 14 ELS Average Number o f S q u ir r e ls Observed Per Perio d 0 4.53 9.19 20.38 16.53 11.54 0 Spring ( March-April-May) A verage Sumner (June-July-August) 30 Number Of S q u ir r e ls 20 O bserved Per 10 O b serv a tio n P erio d 7 -9 9 -1 1 11-1 1 -3 3 -5 5 -» 7 -9 9 -1 1 1 1 -1 1 -3 3 -5 5 -> W inter { D ecem ber-January-F ebruary) F a ll (Septem ber-O ctober-N ovem ber) A verage < 7 30 Number Of S q u ir r e ls 20 Observed Per 10 O b serv a tio n P er io d <• 7 7 -9 9 -1 1 1 1 -1 D a y lig h t Time P er io d s Figure 12. 1 -3 3 -5 5 -^ 7 -9 9 -1 1 D a y lig h t Time 1 1 -1 1 -3 P e r io d s D aily a c t i v i t y p a t t e r n s o f b lack and fox s q u i r r e l s d u rin g each season o f th e y e a r in E a s t L ansing, Michigan. Time i s c o r r e c te d to E a stern Standard Time. Black s q u i r r e l s shown in s o l i d l i n e , fox s q u i r r e l s in broken l i n e . 3 -5 5 -* > HI HI HARRISON ROAD • • Ml N e st S i t e o f #7 L o c a tio n s where #7 was trapped o r ob served ea [10] N e st S i t e o f #10 L o c a tio n s where #10 was trapped o r ob served Figure 13. Home ranges of female black squirrels #7 (7.8 acres) and #10 (8.3 acres) in East Lansing, Michigan. M U D W OOD W IL D W O O D D R IV E D R IV E HARRISON ROA9 lit ip!®! ' H N est S i t e o f #27 L o c a tio n s where #27 was trapped o r o b served col N e st S i t e o f #48 L o c a tio n s where #48 was trapped o r ob served Figure 14. Home ranges of male black squirrels #27 (7.8 acres) and #48 (6.3 acres) in East Lansing, Michigan. aco ~ns) L a s t ' e a r s 1 ; aco ~nsl. . Hickory, Shagbark Carya ovata Walnut, Black Ju g lan s n ig ra Ash, White Fraxinus americana Apple and Crabapple Maius spp. (Gi *een) P a rts o f p la n t e a te n : --------------Buds and flo w ers ________ F r u i t / s e e d / n u t e ate n on t r e e ( r i p e an d /o r u n rip e) .................... F r u i t / s e e d / n u t e aten on ground (on th e s u rfa c e or b u rie d ) Overi ‘i pe Feb 72 u t i l i z e d by th e s q u i r r e l s m ostly during th e summer, w hile white oak acorns matured and were u t i l i z e d in th e f a l l of th e f i r s t y e a r. Green apples were used by both black and fox s q u i r r e l s during th e summer, but fox s q u i r r e l s were observed feeding on them more o f te n . I n t e r e s t i n g l y , th e s q u i r r e l s went through g re a t e f f o r t to gnaw away th e f l e s h y p a r t of th e a p p le, but never a te th e core or s k in , which were d is c a rd e d . During th e w inter months a t times of deep snow, they were observed fe e d in g on th e brown o v e rrip e apples t h a t remained on tre e . the While th ey appeared to consume both th e sk in and f le s h y p a rts th e n , th e y s t i l l discard ed th e co re. Spring l i t t e r j u v e n ile black and fox s q u i r r e l s were observed feeding on ash and box e ld e r seeds during summer, but f o r th e most p a r t , th e s q u i r r e l s d e fe rre d use of th e se u n t i l th e heavy snows of e a r ly w in ter covered th e ground. Then, th e se seeds were o fte n th e only foods s t i l l hanging from th e branches a t t h i s tim e. The use of shagbark h ic k o rie s by both black and fox s q u i r r e l s was i n tr i g u i n g . In August and September, when th e s q u i r r e l s were " c u ttin g n u ts ," in d iv id u a l t r e e s appeared to rip e n a t d i f f e r e n t r a t e s , some e a r l y , some l a t e r . This sequence of rip e n in g hickory t r e e s was th e same each y e a r and th e s q u i r r e l s would a tta c k them in sequence. A fte r converging on an e a r l y rip e n in g t r e e , i t was c e r t a i n t h a t they would appear a t th e next t r e e in th e sequence a few days l a t e r . At tim es, th e number of s q u i r r e l s in a t r e e was so g re a t and th e a c t i v i t y so con fu sing , i t was n e a rly im possible to record a l l th e i n t e r a c t i o n s . On August 20, 1978, n e a r ly every s q u i r r e l in th e hickory region had converged on one la rg e shagbark. From e a r ly morning to near s u n se t, a t 73 l e a s t 25 b lack and fox s q u i r r e l s were in t h a t one t r e e a t a l l tim es. Probably another 20-30 a ls o moved in and out of th e t r e e from neighboring h ic k o rie s o r nearby r o o f to p s . While many of th e nuts were e a te n , i t appeared much o f th e time was sp en t j u s t gnawing away th e green husks. A la rg e p a r t o f th e d isca rd e d n u ts had th e husk p a r t l y or e n t i r e l y gnawed away w hile th e nuts were l e f t i n t a c t . Two 3 0-g allo n p l a s t i c t r a s h cans were f i l l e d with th e d isca rd e d nuts and l a t e r o ff e re d to th e s q u i r r e l s during w in te r . In th e cold season, n e a r ly a l l were e a te n . The major n a tu ra l food sources a v a il a b le to th e s q u i r r e l s during th e f a l l seasons o f 1977, 1978, and 1979 v a rie d from y e a r to year (Table 5 ) . The food supply in th e F a ll o f 1977 was abundant, but a d e a rth of acorns and w alnuts occurred in th e subsequent f a l l . Only h ic k o rie s produced c o n s i s t e n t l y la rg e c ro p s , and in th e F a ll of 1978 th e se were supplemented by a bumper crop of sugar maple seeds which helped make up f o r th e lack o f acorns and w aln uts. About a hundred shagbark h ic k o r ie s were in th e hickory reg ion but they alone could not provide an autumn supply of nuts f o r th e e n t i r e s q u i r r e l p o p u la tio n . The s q u i r r e l s r e l i e d h e a v ily upon supplemental fe e d e rs from November through th e e n t i r e w in te r . Feeding s t a t i o n s in th e re s e a rc h a re a v a rie d in design from e l a b o r a t e l y b u i l t p la tfo rm s (o f te n a ttem p tin g to be s q u i r r e l p r o o f ) , to o th e rs t h a t were no more th an p i l e s of seeds dropped on th e ground. While th e m a jo rity of th e fe e d in g s t a t i o n s were meant p r im a r ily f o r b i r d s , much seed was s c a t t e r e d to th e ground by th e b i r d s , th e re b y making i t a v a il a b le t o ground fo rag in g mammals. During th e p eriod of 74 Table 5. A v a i l a b i l i t y of n a tu ra l foods to East Lansing, Michigan, s q u i r r e l s during f a l l seasons o f 1977, 1978 and 1979. Oak Species of t r e e sampled Hickory Maple Walnut F a ll 1977 Number of t r e e s sampled 23 10 Average number of nuts 21.6 13.1 42.3 5.2 (±4.0) (±1.3) (+6 . 6 ) ( tO .5) (seeds) per m under 7 3 t r e e ( t S E) F all 1978 Number of t r e e s sampled Average number of nuts (seeds) per m under 23 10 7 3 2.3 17.8 217.4 (*1 . 1 ) ( t l . 6) (+9.8) (+0.3) 7 3 0.33 t r e e (+ S E) F a ll 1979 Number of t r e e s sampled Average number of nuts (seed s) per m under t r e e (± S E) 23 10 8.7 16.7 13.0 1.1 (*1. 1 ) (+1.5) (+1 . 6 ) (+0 . 2 ) 75 t h i s study, a number of mammal sp ec ie s were observed fe ed ing a t th e se supplemental feed in g s t a t i o n s during some time of th e y e a r . These included black s q u i r r e l s ( Sciurus c a r o l i n e n s i s ). fox s q u i r r e l s (S. n i g e r ) , red s q u i r r e l s (Tamiasciurus hudsonicus) , f l y i n g s q u i r r e l s (Glaucomys v o la n s ) , chipmunks (Tamias s t r i a t u s ) , t h i r t e e n - l i n e d ground s q u i r r e l s ( C l t e l l u s tr id e c e r n ! in e a tu s ) , r a b b i t s ( S ylvilagu s f l o r i d a n u s ). raccoons (Procyon l o t o r ) , opossums ( D idelphis v i r g i n i a n a ) , skunks (M ephitis m e p h itis ) , woodchucks (Marmota monax) . r a t s (R attus norvegicus) and mice ( Peromyscus s p p . ) . Of the 598 houses in th e re sea rc h a re a , 183 (30.6%) m aintained a t o t a l of 250 fe eding s t a t i o n s , an average of 1 .2 5 /a c re (Figure 16). While th e re was some clumping of th e se f e e d e r s , th e r e was no r e s i d e n t i a l block devoid of them. The d e n s ity of fe e d e rs in the dominant t r e e regio ns making up th e m a jo rity of th e re sea rc h area ranged from about 1 . 0 - 1 . 5 / a c r e . Only th e small hickory region had a d is p r o p o r ti o n a te ly high er d e n s ity of 2 .5 5 /a c r e . I t would be reasonable to exp ect, t h e r e f o r e , t h a t almost every s q u ir r e l n e stin g overw inter in th e re sea rc h area would have had a t l e a s t f iv e fe e d ers w ith in i t s home range to supplement i t s n a tu ra l food supply. I n t e r s p e c i f i c Aggressive Behavior Black and fox s q u i r r e l s were t o l e r a n t of each o th e r during l a t e s p r in g , summer, and e a r l y f a l l , but became in c re a s in g ly ag g ressiv e dur­ ing l a t e f a l l and reached a peak in l a t e w in te r (Table 6 ; Figure 1 7 ); During t h i s time of y e a r , th e blacks were f a r more ag gressive than the fox s q u i r r e l s , th e d if f e r e n c e s between in d ic e s being s i g n i f i c a n t . HANNAH MIDDLE SCHOOL •: ABBOTT &D. 76 • Z * * * Supplemental Feeders [TJ Roads Q Tree Region Boundary Figure 16. D is tr ib u tio n of supplemental fe e d ers m aintained by r e s id e n ts in E ast Lansing, Michigan, s q u ir r e l research a r e a . Density o f feed ers in each t r e e region was: oak = 1 .0 2 /a c r e ; elm = 1 .3 4 /a c r e ; maple = 1 .5 5 /a c re ; hickory = 2 .5 5 /a c r e . Table 6 . Monthly in d ic e s o f agg re ssio n based on en cou nters between black and fo x s q u i r r e l s in E ast Lansing, Michigan. Encounters r a te d a t 3 = sev e re a g g re s s io n , 2 = moderate a g g re s s io n , 1 = m ild a g g re s s io n , 0 = to le r a n c e o r subm issive behavior (moving away). D iffe re n c e between black and fo x s q u i r r e l in d ic e s t e s t e d w ith t - t e s t s . >UJ Total Number o f En­ co un ters < OS T 0 L. Month 1 9 7 7 1 9 7 8 June J u ly August S e p t. O ct. Nov. Dec. 38 81 64 78 91 71 59 Jan. Feb. March A pril May June J u ly Aug. S e p t. O ct. Nov. Dec. 91 125 91 34 59 75 111 151 145 105 106 105 M BLACK M M I 0 L D. D 34 75 57 69 74 56 51 4 5 3 7 12 11 6 49 64 56 31 47 63 100 121 102 63 52 41 18 20 8 1 7 9 10 20 26 17 18 22 SQU I R R E L S S Index Standard E rror E Value V. _(2)_(3). F OX T 0 L M I L D S Q M 0 D. U I R R E L S S Index Standard E Value Error V. D iffere n c e Between In d ic e s 0 1 4 2 5 4 2 0 0 0 0 0 0 0 0.105 0.086 0.172 0.141 0.242 0.268 0.169 0.050 0.036 0.065 0.047 0.057 0.066 0.059 33 74 58 68 78 60 51 5 7 5 9 10 8 5 0 0 1 1 3 3 3 0 0 0 0 0 0 0 ■' 0.132 0.086 0.109 0.141 0.176 0.197 0.186 0.055 0.031 0.045 0.043 0.048 0.058 0.066 n .s . n .s . n .s n .s . n .s . n .s . n .s. 15 30 9 1 4 3 1 1 13 16 21 28 9 11 18 1 1 0 0 9 4 9 15 14 0.824 0.904 0.879 0.176 0.305 0.200 0.108 0.325 0.441 0.724 0.991 1.143 0.108 0.094 0.128 0.106 0.087 0.057 0.032 0.063 0.064 0.099 0.109 0.106 75 103 81 32 49 64 95 132 124 83 81 85 6 9 5 1 6 9 13 11 10 10 7 8 6 7 3 1 2 1 3 8 8 8 11 8 4 6 2 0 2 1 0 0 3 4 7 4 0.330 0.328 0.187 0.088 0.271 0.187 0.171 0.179 0.241 0.362 0.472 0.343 0.082 0.070 0.062 0.064 0.089 0.059 0.042 0.041 0.054 0.076 0.090 0.076 * * * ★* * * * * n .s. n .s . n .s . n .s . n .s . * * ★ * * * * * * *sj Table 6 ( c o n t 'd . ) >- ui< os Total Number o f Enc o u n ters BLACK T M 0 I L. L 0 (0 ) 1) L2 38 34 L9 35 LI 41 L3 56 8 67 6 75 5 68 12 92 21 74 21 57 12 65 21 Month 1 9 7 9 1 9 3 dan. Feb. March A pril May June J u ly Aug. S e p t. Oct. Nov. Dec. 106 111 72 60 67 73 81 87 129 119 89 116 Jan. Feb. March A pril May 135 138 151 136 165 70 76 91 96 114 27 21 34 28 39 M 0 D. SQUI RREL S S Index Standard E Value E rror V. Index Value = * = -05 S QU M M I 0 L D. I RR E L S S Index E Value V. Standard E rro r D ifferent Between In d ic e s (2) 31 28 15 6 2 0 0 2 10 16 12 17 (3) 25 30 11 0 1 0 1 5 6 8 8 13 1.406 1.486 1.028 0.417 0.224 0.082 0.099 0.356 0.457 0.647 0.674 0.810 0. U 6 0.112 0.135 0.086 0.069 0.032 0.045 0.084 0.073 0.087 0.108 0.098 81 88 52 44 52 67 69 71 103 98 71 98 CD (2) (3) 10 9 6 10 8 5 10 8 2 10 5 1 10 4 1 6 0 0 8 2 2 8 4 4 14 7 5 9 7 5 7 8 3 11 3 4 0.434 0.369 0.444 0.383 0.313 0.082 0.222 0.322 0.333 0.319 0.360 0.250 0.084 0.076 0.094 0.092 0.080 0.032 0.068 0.082 0.066 0.070 0.083 0.062 * * * * * * * * * n .s. n .s. n .s. n .s . n .s. n .s . * * * * * * 25 23 19 8 8 13 18 7 4 4 0.859 0.877 0.616 0.412 0.406 0.089 0.094 0.071 0.063 0.054 117 120 129 113 132 9 8 13 16 23 0.222 0.225 0.219 0.235 0.279 0.054 0.054 0.048 0.050 0.049 * * * * * * * * * * n .s . 0 Levels o f s i g n i f i c a n c e : FOX T 0 L. ** = .01 *** = .001 I(E n co un ters X R ating)_______ T otal Encounters 6 7 7 5 7 3 3 2 2 3 «**J 00 T Black Squirrels Fox Squirrels A A I N D E X V A L U E I tffiP 19 7 7 19 8 0 J A S O N D| J F M A M J J A S O N DIJ F M A M J J A S O N D J F M A M Figure 17 In d ic e s o f agg re ssio n (+ S E) f o r b lack and fox s q u i r r e l s during 36 month study in E a s t Lansing, Michigan. 80 Most of th e i n t e r a c t i o n s between s p e c ie s during l a t e s p rin g , summer and e a r l y f a l l were observed to be d i s t r i b u t e d r a t h e r uniformly throughout th e re s e a rc h a r e a . During th e warmer months, both sp ec ie s were fe ed ing on n a t u r a l l y o c c u rrin g food sources which tended to be d is p e rse d over la rg e are as (thousands o f square f e e t ) . They o fte n fed t o l e r a n t l y in mixed groups, sometimes 10-15 in d iv id u a ls spread over two house l o t s . D isplays of a g g re ssiv e behavior were observed only where a person had put out some food in a small area (one or two f e e t in diam eter) which could be e a s i l y dominated by one in d iv id u a l. For th e most p a r t , a g g re ssiv e behavior during t h i s time o f th e y e ar was disp lay ed only by females near t h e i r n e sts o r with r e c e n tly emerged l i t t e r s of j u v e n i l e s . Once snow had accumulated to a depth of two inches or more, th e s q u i r r e l s seldom dug th e nuts th ey had b u rie d . In ste ad th e y r e l i e d on th e more e a s i l y o b ta in a b le supplemental foods put out a t feed in g s t a t i o n s by r e s i d e n t s . During w in te r, th e s e p la ce s were where th e v a st m a jo r ity o f behavioral i n t e r a c t i o n s took p la c e . With most fe ed in g s t a t i o n s c o n s is tin g o f a s i n g le b ird f e e d e r , a lone s q u i r r e l could e a s i l y dominate th e c o n c e n tra te d food source while o th e r le s s a g g re ssiv e in d iv id u a ls were chased away and had to w ait t h e i r tu r n s . Black s q u i r r e l s e x c e lle d a t dominating a fe e d e r when they wanted to feed t h e r e . They would d riv e away or warn o f f fox s q u i r r e l s two or th r e e times as o fte n as they were driven away o r warned o f f by fox sq u irre ls. During th e w in te r, to le r a n c e was observed m ostly when a black and fox s q u i r r e l happened to be sunning themselves in th e same 81 t r e e or where a supplemental feeding s t a t i o n had a number of fe e d e rs or food s c a tte r e d w idely about. During th e Winter of 1977-78, heavy snow did not a r r iv e u n t i l the end of December and th e s q u i r r e l s fed u n til then on bumper crops of acorn s, hickory nuts and w alnuts. A twenty inch snowfall in January remained on th e ground well in to March and t h i s was r e f l e c t e d in the high le v el of black s q u i r r e l aggression a t th e feeding s t a t i o n s throughout t h a t p e rio d . The f a i l u r e of oaks to produce acorns in th e F a ll of 1978 forced s q u i r r e l s to r e l y more h e av ily on hickory nuts and th e bumper crop of sugar maple seeds in l a t e summer and e a r ly f a l l . As th e s e n a tu ra l sources of food dim inished, aggression a t feeding s t a t i o n s appeared much e a r l i e r than the previous year and a t higher le v e ls f o r both black and fox s q u i r r e l s . The black s q u ir r e l aggression lev el f o r th e fiv e months from November 1978 - March 1979 was contin uo usly higher than the peak aggression le v e ls of the preceding and succeeding y e a rs . With only a s l i g h t crop of acorns, walnuts and sugar maple seeds in the F a ll of 1979, th e s q u i r r e l s again turned e a r ly to th e hickory nuts as the major n a tu ra l food source. Again th e aggression a t the feed in g s t a t i o n s appeared in f a l l , but moderated somewhat as th e w in ter turned out to be exceedingly m ild. With l i t t l e snow on th e ground, th e s q u i r r e l s foraged throughout th e w inter and did not r e l y t o t a l l y on the feed in g s t a t i o n s . P o ssib ly th e m ilder tem peratures a lso allowed th e s q u i r r e l s to remain out of th e n e st longer with reduced body heat l o s s . Both of th e se f a c t o r s e v id e n tly had th e e f f e c t of reducing th e s e v e r ity of encounters and in c re a s in g th e number of t o l e r a n t in te r a c t io n s through the w in te r. 82 Weather and Winter Weight F lu c tu a tio n s The c lim a to lo g ic a l d a ta f o r Lansing, Michigan, during th e Winters of 1977-78, 1978-79, and 1979-80 (Table 7) showed t h a t th e f i r s t two were more severe in terms of both cold and sn o w fall. Perhaps one of th e most im portant c lim a to lo g ic a l f a c t o r s was th e number of days with two or more inches of snow on th e ground, s in c e t h i s influenced th e s q u i r r e l s ' dependence on th e supplemental f e e d e r s . The tra p p in g and weighing of black and fox s q u i r r e l s from October 27, 1979 to February 22, 1980 happened to ta k e place during a very mild w in ter having r e l a t i v e l y few days of deep ( 2+") snow cover. During t h i s tra p p in g p e rio d , changes in th e weights of 24 black and 12 fox s q u i r r e l s captured and weighed more than once were recorded (Table 8 ) . While s ix a d u lt black s q u i r r e l s were captured and weighed once, th e y were never subsequently re c ap tu red and, t h e r e f o r e , no data were obtained f o r t h i s age group. However, s ix a d u lt fox s q u i r r e l s were each captured and weighed a number of tim es. Of th e s e , one gained 45 g, ano ther showed no gain and fo u r o th e rs l o s t a t o t a l of 455 g. Three of th e se a d u lts were females which should have been mating and becoming pregnant during th e January-February period they were observed. Only one gained w eight, however, while another managed to m aintain i t s weight over a 24 day p e rio d . The t h i r d l o s t 205 g during a 43 day p e rio d . The su bad ults appeared to have gained weight b e t t e r than the a d u lts. Of th e 14 black su b ad u lts t h a t were weighed a number of tim es, s ix were followed through f a l l and w in ter and gained a t o t a l of 245 g. Table 7. C lim a to lo g ic al d a ta f o r Lansing, M ichigan,during th e W inters o f 1977-78, 1978-79 and 1979-80. Days with Minimum Temperature Below 0 ° F 1977-78 Nov Dec Jan Feb March Total Days with Average D aily Temperature Below 32° F Degree Days Below 32° F Monthly Ave. Temperature D eparture From Normal Snowfal1 Per Month (In ch e s) Days with Snow on Ground Over 2 inches 0 3 6 14 7 30 9 19 30 28 20 106 74 254 441 564 249 1582 + 1.1 - 1 .8 - 5 .0 -1 2 .7 - 7.3 -2 5 .7 8 .1 13.3 34.0 6 .7 4 .6 66.7 5 9 31 28 28 101 1978-79 Nov Dec Jan Feb Mar T otal 0 0 lo 13 0 23 7 20 31 26 9 93 28 176 486 536 71 1297 + 1 .4 - 0 .3 - 6 .5 - 11.0 + 4 .9 -1 1 .5 7 .0 14.7 27.1 4 .1 4 .2 57.1 3 17 29 28 4 81 1979-80 Nov Dec Jan Feb March T otal 0 1 4 6 2 13 10 17 26 23 14 90 33 127 320 366 149 995 0 .0 +3.5 - 0 .4 - 4 .4 -3 .0 4 l 7.2 3 .2 6 .7 5 .5 8 .8 3 0 3 4 1 6 3 17 Table 8 . I.D . Number B L A C K 1 2 3 4 5 6 7 S Q 8 9 u i 10 R 11 R 12 E 13 L 14 S 15 16 17 18 19 20 21 22 23 24 70 73 74 76 77 78 79 81 83 84 85 86 87 89 94 97 98 99 101 105 106 107 121 124 Changes in th e w eights o f E ast Lansing, M ic h ig a n ,s q u irre ls cap tu red more than once during th e October 27, 1979 t o February 22, 1980 tr a p p in g p e rio d . Weights in grams. Sex M M F M F M F M F F M M F M M F F M M M M F F F Age Group JUV SUB SUB SUB SUB SUB SUB SUB SUB JUV SUB JUV JUV SUB SUB JUV JUV SUB JUV JUV JUV JUV SUB SUB AD AD AD AD AD AD AD AD AD AD AD AD AD AD F irst Capture Weight 305 465 495 515 460 475 510 505 440 360 450 330 310 500 470 320 330 450 385 395 365 370 525 505 Last Capture Weight 305 500 555 520 480 540 555 490 450 380 440 345 315 485 480 435 380 540 430 510 490 435 530 465 Wei ght G ain/ /Loss 0 + 35 + 60 + 5 + 20 + 65 + 45 - 15 + 10 + 20 - 10 + 15 + 5 - 15 + 10 +115 + 50 + 90 + 45 +115 +125 + 65 + 5 - 40 Number o Days Beti F i r s t am Captures 6 99 117 2 4 94 9 91 4 2 21 15 2 19 95 65 2 105 7 99 99 79 17 19 Comments 00 -p » Lost weight to 385 b e fo re g a in in g t o 540 Table 8 F 0 X S Q U I R R E L S (cont'd.) I.D Number Sex 1 36 2 82 3 88 4 90 5 100 6 110 7 111 8 114 9 115 10 117 11 118 12 122 M F F M M F M F F F M F Age Group AD SUB JUV JUV SUB SUB AD SUB AD AD AD AD AD AD AD AD F irst Capture Weight 800 660 335 445 605 600 825 610 935 825 765 770 Last Capture Weight 690 750 380 440 640 560 715 620 980 620 735 770 Weight G ain/ /L oss -110 + 90 + 45 - 5 + 35 - 40 -110 + 10 + 45 -205 - 30 0 Number of Days Between F i r s t and L ast C aptures 80 107 6 19 57 89 84 88 69 43 25 24 Comments / L o s t weight to 385 b e fo re gaining t o 440 ^ ^ ^ " T i a i n e d weight t o 675 b e fo re ^ x j o s i n g t o 560 / / g 86 Four s u b ad u lt fox s q u i r r e l s were a lso followed through most of f a l l and w in te r but managed to gain only a t o t a l of 95 g. Perhaps th e most s p e c ta c u la r weight changes were recorded f o r black j u v e n i l e s . The summer l i t t e r s in 1979 were well behind sch ed ule, th e ju v e n i l e s f i r s t emerging from th e n e st in l a t e October and e a r ly November and weighing s l i g h t l y more than 300 g. Had they been s u b je c te d to th e ty p ic a l l a t e f a l l / e a r l y w in te r weather of Michigan, th e y would have had l i t t l e chance of s u r v i v a l . However, th e very mild weather t h a t occurred allowed them to achieve sub adu lt weight (450+ g) by th e time th e f i r s t snows and cold weather a rriv e d in Jan uary . Ten black j u v e n i l e s gained a t o t a l of 565 g, of which f o u r in d iv id u a ls were follow ed through f a l l and w in ter and accounted f o r a t o t a l of 430 g g ain ed. Only two fox j u v e n i l e s were captured during th e f a l l , but n e ig th e r was captured or observed during w in te r. One in d iv id u a l gained 45 g in a week, w hile th e o th e r l o s t 60 g before re g a in in g 55 g w ith in a th r e e week p e rio d . Since th e te n black s q u i r r e l ju v e n ile s c o n trib u te d s i g n i f i c a n t l y t o th e t o t a l black s q u i r r e l weight g a in , but th e two fox s q u ir r e l j u v e n i l e s made only a s l i g h t c o n tr ib u tio n to th e t o t a l fox s q u i r r e l w eight g a in , s t a t i s t i c a l comparisons were made only between th e a d u lt and su b ad u lt black and fox s q u i r r e l s (Table 9 ) . While th e t o t a l weight g a i n / l o s s of th e 14 su b a d u lt black s q u i r r e l s handled throughout th e e n t i r e tra p p in g p e rio d (r e g a r d le s s of how long th e y were followed) was +265 g, and t h a t of th e 10 a d u lt and su bad ult fox s q u i r r e l s was -315 g, th e d if f e r e n c e between th e means of th e s e groups was not s i g n i f i c a n t a t Table 9. Comparison o f a d u lt and su b a d u lt black and fox s q u i r r e l weight changes ( in grams) cap tured in E ast L ansing, M ichigan,from October 27, 1979 t o February 22, 1980. D iffe re n c e s between means t e s t e d w ith t - t e s t . Number of In d iv id u a ls Black s q u i r r e l s caught more than once Fox s q u i r r e l s caught more th a n once 14 10 Only in d iv id u a ls follow ed through e n t i r e tra p p in g p e rio d . 6 black 7 fox Only in d iv id u a ls follow ed through w in te r weather p e rio d (1 /5 -2 /2 2 /8 0 ) 6 black *See Table 8 . 9 fox Total Id e n tifica tio n Weight Gain/Loss Numbers * 73 - 74 - 76 + 265 77 - 78 - 79 81 - 83 - 85 89 - 94 - 99 121 - 124 - 315 36 - 82 - 100 110 - 111 - 114 115 - 117 - 118 122 73 - 74 - 78 + 245 81 - 94 - 99 - 80 36 - 82 - 100 110 - 111 - 114 115 73 - 74 - 78 81 - 94 - 99 + 235 36 - 82 - 110 111 - 114 - 115 117 - 118 - 122 - 315 Average Wei ght Gain/Loss + 18.93 - 31.5 + 40.83 - 11.43 + 39.17 - 35.00 Comments Average weight g a i n / l o s s o f th e s e groups not s i g n i f i c a n t l y d i f f e r e n t a t .05 l e v e l , bu t s i g n i f i c a n t l y d i f f e r e n t a t 0 .1 le v el Not s i g n i f i c a n t l y d i f f e r e n t a t .05 l e v e l , but s i g n i f i c a n t a t 0 .2 l e v e l . S ig n ific an tly d ifferen t at .05 l e v e l . 88 th e .05 l e v e l , but was s i g n i f i c a n t a t th e 0.1 l e v e l . A lso, w hile the t o t a l weight g a in /lo s s of th e 6 su b ad u lt black s q u i r r e l s followed through th e f a l l and w in ter was +245 g, and t h a t of th e 7 a d u lt and su b ad u lt fox s q u i r r e l s was -80 g, th e d if f e r e n c e between th e means of th e s e groups was not s i g n i f i c a n t a t th e .05 l e v e l , but was s i g n i f i c a n t a t the 0.2 l e v e l . The groups of in d iv id u a ls involved in th e se comparisons showed weight f l u c t u a t i o n s o ccu rring during f a l l and w in te r. When comparing th e weight changes occurring in in d iv id u a ls followed only during th e w in ter weather period (1/5 - 2 /2 2 /8 0 ), however, th e 6 su bad ult black s q u i r r e l s gained a t o t a l of 235 g and the 9 a d u lt and subadult fox s q u i r r e l s l o s t a t o t a l of 315 g and the d if f e r e n c e between th e means was s i g n i f i c a n t a t th e .05 l e v e l . Apparently the fox s q u i r r e l s did f i n e during th e mild f a l l and e a r ly w in ter w eather, but had d i f f i c u l t y m a intain ing weight when the w inter weather f i n a l l y a r r iv e d . This was so in s p i t e of th e f a c t t h a t t h i s weather was not as severe as t h a t occu rring in th e previous w in te rs . Nests Overwinter Leaf Nest S it e s The number of w in te r l e a f n e sts m aintained in th e various t r e e s p ec ie s by black and fox s q u i r r e l s changed a p p re cia b ly from th e Winter of 1978-79 t o th e Winter of 1979-80 (Table 10). The n e a rly 50% in c re a s e in t o t a l l e a f n e s ts in th e Winter of 1979-80 may have been due t o the m ild er weather t h a t w inter and/or an in creased s q u ir r e l population (see population e s ti m a te s ) . While oak t r e e s contained the l a r g e s t number of l e a f n e s ts during both w in te rs , th e r e was only a Table 10. Comparison of t r e e u t i l i z a t i o n as w in te r l e a f n e s t s i t e s in dominant t r e e re g io n s by s q u i r r e l s in E ast Lansing, Michigan. Number o f l e a f n e s ts m ain tained in each t r e e s p e c ie s Winter of 19781979 Winter of 19791980 Oak Reqion Elm Reqion Maple Region Hickory Reqion T o tal n e s ts in s p e c ie s Oak Reqion Elm Reqion Maple Reqion Hickory Reqion T otal n e s ts in s p e c ie s Percentage In c re a s e Elm 2 2 33 2 — — 9 6 27 — «» 1 1 3 108 53% Maple 2 Hickory 2 Oak 96 Apple 2 4 7 2 4 1 5 1 — 1 4 4 14 2 38 15 — 1 12 25 50 —— 7 2 1 2 59.5 138.2 ■“ ““ • • 3 7 .4 Others 5 100 67 81 22% 27% Ash 1 5 42 34 20% 17% 116 38% Willow 4 1 5 9 — — 6 7 — — — — 4 Total Nests In Region 103 50.7% 48 23.6% 42 20.7% 10' 5.0% 203 127 41.9% 2 58 19.1% 7 107 35.3% 1 "11 3.7% 14 P ercen t I n c re a s e 303 23.3 20.8 154.8 10 49.3 90 s l i g h t in c re a s e in th e second w in te r. The l a r g e s t p a r t of th e in c re ase in l e a f n e st number was among th e t r e e s in th e maple re g io n . The use of maple t r e e s as l e a f n e s t s i t e s a lso in creased throughout th e re sea rc h a re a . Winter Nest Aggregations A major f a c t o r in flu e n c in g th e numbers of black and fox s q u i r r e l s occupying n e s ts over w inter (Table 11) was th e mating of many females during January and February. Upon becoming pregnant, they e i t h e r drove o ut^th e o th e r n e st members or moved out themselves to a l t e r n a t e n e s ts . This r e s u lte d in a la r g e r number of sin g le-o ccu p an t n e s ts . With th e s q u ir r e l pop ulation in th e re sea rc h area composed of approximately equal numbers of black and fox s q u i r r e l s , an approximately equal number of sin g le-o ccu p an t n e sts could be a t t r i b u t e d to pregnant females f o r each s p e c ie s . During each w in te r, however, twice as many s in g le -o cc u p a n t n e sts were observed f o r fox s q u i r r e l s . Winter n e st ag gregation s of black s q u i r r e l s c o n s is te n tly averaged 40-45% la r g e r than average fox s q u ir r e l n e s t a g g re g atio n s. The d iff e r e n c e s between th e s e means were s t a t i s t i c a l l y s i g n i f i c a n t a t the .01 le v e l . In te r a c tio n s with People Of 178 r e s id e n ts inte rv ie w ed , 51 (28.7%) p re fe rre d fox s q u i r r e l s to black s q u i r r e l s , 73 (41.0%) had p o s itiv e opinions in p referen ce f o r th e black s q u i r r e l s and 54 (30.3%) expressed no p re fe re n c e , enjoying them both e q u a lly . sq u irre ls. None of th o se interview ed expressed a d i s l i k e f o r Only two r e s id e n ts of the re sea rc h area were known to spend much time "discouraging s q u i r r e l s from e n te rin g t h e i r y a rd s ." 91 Table 11. Comparisons between d if f e r e n c e s in means of black and fox s q u i r r e l w inter n e st agg regatio ns in East Lansing, Michigan. Year 1 Black S q u ir r e ls Per Nest 2 4 Total 3 1977-78 Number of Nests Number of S q u ir re ls 7 14 7 28 1978-79 Number of Nests Number of S q u ir re ls 1979-80 Number of Nests Number of S q u ir re ls 9 2 32 27 . 8 70 x = 2.2 6 13 10 6 26 30 1 Fox S q u ir r e ls Per Nest 2 3 4 Total 16 8 3 16 16 9 34 14 10 20 82 x = 2 .4 14 20 18 5 6 0 27 0 X 41 = 1.5 0 30 0 52 = 1.7 X D ifferences Between means S ig n i f ic a n t a t .01 lev el S ig n i f ic a n t a t .01 lev el ; 9 14 7 9 28 21 31 20 8 2 0 30 _4 62 x = 2 .0 20 16 6 0 X 42 = 1.4 1 S ig n i f ic a n t a t .01 le v el 92 Most of th e time people considered th e black and fox s q u i r r e l s as a source of p le a s u re and amusement, sometimes a source of problems and o nly r a r e l y a source of a q u a rre l with a neighbor. Most people thought th e fox s q u i r r e l s were f r i e n d l i e r than th e black s q u i r r e l s and could more e a s i l y be e n tic e d to ta k e food from th e hand or even e n te r the house. One r e s i d e n t of th e re sea rc h are a op erated an orphaned animal r e h a b i l i t a t i o n c e n te r in her house and many r e s i d e n t s a s s i s t e d in re c o v erin g young from blown-down n e sts or r a i s i n g th e young u n t i l big ■> enough to be re le a s e d in th e neighborhood. One r e t i r e d r e s id e n t d e riv ed p le a s u re from watching a female black s q u i r r e l , which nested in th e a t t i c , as she crossed th e s t r e e t on the teleph on e w ire. This fem ale, tagged #10 had th e h a b it of tr a v e r s in g th e wire upside down, s l o t h - s t y l e . S q u ir r e ls n e s tin g in a t t i c s caused problems f o r some r e s i d e n t s . These nuisance animals were e a s i l y removed with l i v e t r a p s obtained from th e Ingham County Animal Control Department and th e e n tra n ce s in to th e a t t i c were then s e a le d . While most of the r e s id e n ts f e l t i t was t h e i r r e s p o n s i b i l i t y to make t h e i r houses s q u i r r e l - p r o o f , one r e s i d e n t did n o t want any s q u i r r e l s t o come near th e house and enforced t h i s p re fe re n c e w ith a BB-gun and s l i n g s h o t . This a t t i t u d e r e s u l t e d in a p e rp e tu al q u a rre l with th e neighbor, who had th re e feed in g s t a t i o n s in th e backyard. Two i n d iv id u a ls , r e s i d i n g o u ts id e th e re s e a rc h a re a , so d is lik e d s q u i r r e l s t h a t th e y each had th r e e l i v e t r a p s o p e ra tin g con tin u o u sly in t h e i r backyards in an attem p t to get r i d of a l l th e s q u i r r e l s in th e neighborhood. The animal c o n tro l agent would check th e tr a p s d a ily to remove captured s q u i r r e l s . Captured in d iv id u a ls would be re le a s e d 93 about a block away in sympathy with th o se r e s i d e n t s who enjoyed having s q u i r r e l s in th e neighborhood. DISCUSSION D is tr ib u tio n o f Black S q u ir r e ls D isregarding i s o l a t e d popu lation s o u ts id e East Lansing, twenty years a f t e r i t s in tr o d u c tio n in to East Lansing th e black s q u ir r e l population occupied an area of about f i v e square miles (3200 a c r e s ) . While much of the d is p e r s a l may have been n a t u r a l , a s i g n i f i c a n t p o rtio n must be a t t r i b u t e d to human a c t i v i t y . A number of independent re p o rts from long-tim e r e s id e n ts of the re sea rc h area claimed t h a t a r e s i d e n t , Dr. Musselman, liv in g on Sunset Lane introduced a number of black s q u i r r e l s to th e neighborhood s h o r t l y a f t e r they had been introduced on th e Michigan S ta te U n iv e rs ity campus. Attempts to v e r if y t h i s f a i l e d sin ce th e fam ily moved away a f t e r the deaths of Dr. Musselman and h is w ife . Other r e s id e n ts claimed to have moved some black s q u i r r e l s to W h ite h ills E s ta te s and near Park Lake Road in the East Lansing a re a , and even to lo c a tio n s o u ts id e th e county. The Ingham County Animal Control Department most c e r t a i n l y c o n trib u te d to th e spread of black s q u i r r e l s through th e in d is c rim in a te r e le a s e of captured nuisance anim als. While the black s q u ir r e l pop ulatio n had managed to in c re a s e i t s d i s t r i b u t i o n , i t had not e x c lu s iv e ly taken over any neighborhoods. Fox s q u i r r e l s were s t i l l found throughout East Lansing and th e p rop ortio n 94 95 of black s q u i r r e l s v a rie d from 2556 - 9056 of any neighborhood s q u ir r e l p o p u la tio n . The q u e stio n is whether the black s q u i r r e l w ill e v e n tu a lly re p la c e th e fox s q u i r r e l , as they did in M arshall, Michigan. Perhaps th e most i n t e r e s t i n g question ra is e d by th e black s q u ir r e l presence in East Lansing was why i t had not fa re d well on th e Michigan S ta te U n iv e rsity campus. Individual black s q u i r r e l s were o fte n observed fo rag in g along th e edges of the campus and some had spent the e n t i r e f a l l season feed in g on campus hickory nuts and acorns. however, none has e s ta b lis h e d a permanent re s id e n c e . To d a te , One f a c t o r p o s sib ly a f f e c t in g th e black s q u i r r e l s was th e presence of la rg e numbers of s tu d e n ts whose d iurnal a c t i v i t y coincided with t h a t of the sq u irre ls. Compared to th e q u ie t of a r e s i d e n t i a l neighborhood during th e daytime, black s q u i r r e l s might have found a campus of thousands of s tu d e n ts and b ic y c le s h a ra ss in g . The fox s q u i r r e l s , on th e o th e r hand, had a d ju sted well to t h a t a c t i v i t y and o fte n approached s tu d e n ts f o r "handouts". Perhaps th e r e is a d iff e r e n c e between black and fox s q u i r r e l s in t h e i r to le ra n c e of human a c t i v i t y . Another f a c t o r t h a t may have influenced th e black s q u i r r e l s on campus was the presence of many red s q u i r r e l s (Tamiasciurus hudsonicus) t h e r e . Robinson and Cowan (1954) mentioned i n t e r a c t i o n s between introduced e a s te r n gray s q u i r r e l s and th e chick aree (T. d o u g l a s i i ) , a c lo se r e l a t i v e of th e red s q u i r r e l , in B r i t i s h Columbia. Like th e red s q u i r r e l , th e ch ickaree i s t e r r i t o r i a l and showed a p re fe re n ce f o r co n ifero u s h a b i t a t . The chickaree was dominant in a l l c o n f l i c t s with th e much la r g e r gray s q u i r r e l , but the gray s q u ir r e l never h e s i t a t e d to tr e s p a s s re p e a te d ly . C o n flic ts between black and 96 red s q u i r r e l s on th e Michigan S ta te U n iv e rs ity campus may have a ffe c te d th e black s q u i r r e l s ' success t h e r e . At th e s t a r t of th e black and fox s q u ir r e l study in 1977, red s q u i r r e l s were common on campus, but r a r e l y observed in th e r e s i d e n t i a l neighborhoods. By th e end of th e study, however, red s q u i r r e l s were sig h te d o fte n in East Lansing and o c c a s io n a lly c a p tu re d . In 1981, a number of re s id e n ts re p o rte d c o n f l i c t s involving red s q u i r r e l s with black or fox s q u i r r e l s a t the supplemental f e e d e r s . Another c o n f l i c t between a red s q u ir r e l and a black s q u i r r e l concerned th e use of a den s i t e . The d is p u te continued f o r over two weeks befo re th e black s q u ir r e l managed to secure th e den fo r i t s own use. The r o l e of the red s q u ir r e l in the urban s q u ir r e l population awaits in v e s t ig a ti o n . Population Estim ates S q u irre l d e n s i t i e s in ru r a l environments vary with the v i c i s s i t u d e s of th e n a tu ra l food supply and may be expected to be le s s than th o se of urban s q u ir r e l po p u latio n s which have a more c o n sta n t food supply. D. A llen (1943) f e l t t h a t a f a l l population of th re e fox s q u i r r e l s per wooded acre was r a r e l y exceeded and two per wooded acre was considered high. The s q u i r r e l s stu d ie d by Bakken (1952) varied between .04 and 1 . 9 / acre f o r fox and between 1.0 and 1 . 3 / acre f o r g ra y s . Brown and Yeager (1945) found fox s q u ir r e l d e n s i t i e s in I l l i n o i s woodlots and w i l d l i f e areas to be between .02 and and gray s q u i r r e l s to be 1 .4 9 /a c r e . 2 .2 3 /a c re Uhlig (1956) re p o rte d gray s q u i r r e l p o p u latio ns in fo u r West V irg in ia s t a t e f o r e s t s v aried between 97 .21 and 1 .4 1 /a c r e , during 1949 t o 1954. Thompson (1978b) noted a gray s q u i r r e l p o p u la tio n d e n s it y of 1 .7 3 /a c r e in a Toronto cemetery. The E ast Lansing s q u i r r e l p o p u la tio n e s tim a te s were made during w in te r and th e r e f o r e would have been l e s s than were found th e preceding fa ll. Robinson and Cowan (1954) re p o rte d a 21.6% d e c lin e in a gray s q u i r r e l po pu la tio n from autumn ( .8 8 /a c r e ) t o sp rin g ( . 6 9 / a c r e ) . A gray s q u i r r e l p o p u la tio n s tu d ie d by Longley (1963) experienced a 35% d e c lin e from f a l l ( 1 .0 / a c r e ) to w in ter ( . 6 5 / a c r e ) . Based on th e p o pu lation re d u c tio n s recorded by th e se i n v e s t i g a t o r s , i t is p o s s ib le to approximate th e East Lansing f a l l s q u ir r e l d e n s i t i e s . A s q u i r r e l d e n s it y of 2 .4 /a c r e during th e Winter of 1979-80 in East Lansing would have been th e remnants of a 3.06 - 3 .6 9 /a c r e d e n s ity in th e previous f a l l , and a d e n s ity of 1 .6 /a c r e during th e Winters of 1977-78 and 1978-79 would have survived from a 2,04 - 2 .4 6 /a c r e d e n s ity in the previous f a l l . I t th e r e f o r e would be reaso nable to expect the East Lansing e a r l y f a l l s q u i r r e l p o p u latio n d e n s i t i e s during t h i s study to have been between 2 .0 - 4 . 0 / a c r e . This was g e n e r a lly higher than th ose normally found in r u r a l p o p u la tio n s . Flyger (1970) re p o rte d t h a t two "suburban Baltimore woodlots" had s q u i r r e l p o p u la tio n d e n s i t i e s s h i f t i n g between 1.0 and 5 . 0 / a c r e . The East Lansing s q u i r r e l p o p u la tio n , even w hile liv in g through two severe w in te r s , f l u c t u a t e d le s s than t h i s and did not reach as low a le v e l as th e Baltimore w oodlots. This was a t t r i b u t e d to a more c o n sta n t food supply in th e r e s i d e n t i a l ecotype. 98 N a ta li ty Uhlig (1956) compared th e average l i t t e r s iz e s of gray s q u i r r e l s re p o rte d in s tu d ie s from te n s t a t e s and England f o r th e years 1934-1955. He found t h a t average l i t t e r s iz e s ranged between 2.1 and 3.43 w ith th e average of a l l averages being 2.7 2 . The gray s q u ir r e l p o pu la tio n in a Toronto cemetery re p o rte d by Thompson (1978b) averaged 3.1+ 0 . 4 / l i t t e r . The average number of ju v e n ile s f o r a l l 48 East Lansing black s q u i r r e l sp rin g l i t t e r s was 3.16± .1 6. This was much h ig h e r than th e average re p o rte d by Uhlig f o r r u r a l gray s q u i r r e l p o p u la tio n s and was comparable to t h a t re p o rte d by Thompson. This was t r u e d e s p ite th e f a c t t h a t t h i s average included l i t t e r s in fluen ced by two w in te rs of severe weather and a f a l l mast crop f a i l u r e . D. A llen (1942) re p o rte d t h a t 38 fox s q u i r r e l l i t t e r s had an average of 2.92+ 0.1 y o u n g / l i t t e r , Brown and Yeager (1945) noted 85 l i t t e r s with an average of 2 . 5 1 / l i t t e r , and Packard (1956) found an average of 2 . 8 / l i t t e r f o r 14 fox s q u i r r e l n e s t s . The average of a l l th e s e 137 l i t t e r s was 2 . 6 5 / l i t t e r and th e average of th e 49 East Lansing fox s q u i r r e l s p rin g l i t t e r s was 2.65 + .16 l i t t e r . In compiling t h i s average, th e East Lansing fox s q u ir r e l p op u la tio n had two y e a rs of sp rin g l i t t e r averages which would have been among th e h ig h e st of those re p o rte d f o r r u r a l fox s q u i r r e l p o p u la tio n s . The one y e ar of poor re p ro d u c tio n (1979), however, lowered th e average E ast Lansing fox s q u i r r e l sp rin g l i t t e r s iz e so as merely to equal to t h a t re p o rte d f o r r u r a l fox s q u i r r e l p o p u la tio n s . Though fox and gray s q u i r r e l s can have two l i t t e r s a y e a r , Bakken (1955:55) noted t h a t " th e h ig h e st percentage of gray s q u ir r e l young 99 appeared in June, w hile th e h ig h e st percentage of fox s q u i r r e l young appeared in J u ly . A s m a lle r , secondary peak occurred in October i n d ic a tin g a second breeding season f o r th e gray s q u i r r e l . not noted f o r th e fox s q u i r r e l . " This was A fte r th e peak of sprin g re p ro d u c tio n , both black and fox s q u i r r e l l i t t e r s in East Lansing emerged from th e n e s t throughout th e summer w ith only a s l i g h t second peak o c cu rrin g in e a r l y f a l l . The number and s iz e of l i t t e r s f o r both sp e c ie s appeared to be about e q u a l, except during th e F a ll of 1979. In l a t e October and e a r l y November, a group o f e ig h t black s q u i r r e l l i t t e r s averaged 2 . 5 / l i t t e r and only one fox s q u i r r e l l i t t e r of two young appeared. These must have been th e second l i t t e r s o f females which produced delayed s p rin g l i t t e r s . This was th e only time th e re appeared to be any d if f e r e n c e s between e i t h e r numbers or s i z e of black and fox s q u i r r e l summer l i t t e r s . Brown and Yeager (1945) found a c o n sid e ra b le overlap in th e two breeding and yo u n g -rearin g seasons of both gray and fox s q u i r r e l s . Bakken (1952) observed gray and fox s q u i r r e l m ating-chases from January t o June, but n e ith e r mentioned ever observing a mixed mating chase. The only r e p o r t found in th e l i t e r a t u r e concerning a mixed mating chase (Moore, 1968) was t h a t o f a f u l l y a d u lt fox s q u i r r e l involved in a gray s q u i r r e l ch ase. Black and fox s q u i r r e l s in th e East Lansing area were observed in mating chases from January through J u ly and on only one occasion was a mixed mating chase observed. of fo u r male black s q u i r r e l s was On t h a t o c ca sio n , a queue pursuing a female black s q u i r r e l when a fox s q u i r r e l jo in e d in a t th e end of th e l i n e . Following th e black s q u i r r e l s through th e t r e e s f o r a d is ta n c e of about 100 y a rd s , th e fox s q u i r r e l took up a p o s itio n in th e same t r e e t h a t th e black s q u i r r e l s 100 did upon sto pp ing . About 15 minutes l a t e r , th e chase resumed down the t r e e and across th e lawn and th e s t r i n g of s q u i r r e l s s tr e tc h e d out f o r about 60 f e e t with th e fox s q u ir r e l a t th e end. Some quick moves by th e female l o s t th e l a s t two blacks and th e fox s q u i r r e l . One of the black s q u i r r e l s e v e n tu a lly re jo in e d th e chase, but th e o th e r black and th e fox s q u ir r e l wandered o f f in another d i r e c t i o n . The mating chase observed in th e East Lansing study area involved a p o s s ib ly m ature, but probably inexperienced one y ear old fox s q u i r r e l . Such behavior is c e r t a i n l y r a r e and no matings or mixed o ffs p rin g were observed during t h i s stud y. No r e p o r ts of cross-m atings between fox and gray s q u i r r e l s were found in th e l i t e r a t u r e . The re p rod u ctio n achieved by black and fox s q u i r r e l s in th e East Lansing area appeared t o have been s im ila r f o r both species in 1978. This r e s u lte d in popu latio n e stim ate s f o r th e Winter of 1978-79 a t about the same le v e ls estim ated f o r t h a t of 1977-78. Reproduction in th e Spring of 1979 was delayed to such an e x te n t t h a t most fox s q u i r r e l s produced only one l i t t e r t h a t y e a r. The black s q u ir r e l sp rin g l i t t e r s , though l a t e r than u su a l, were e a r l i e r than th e fox sq u irre ls' l i t t e r s . This seemed to allow s u f f i c i e n t time f o r a number o f the black females to have second l i t t e r s . These l i t t e r s , emerging from the n e sts in l a t e f a l l , managed to surv ive due to a f o r t u i t o u s l y mild l a t e f a l l and e a r l y w in ter (see Table 7 ). This r e s u lte d in a higher propo rtion of black s q u i r r e l s in th e tra p p in g area during the Winter of 1979-80. This in d ic a te d t h a t changes in East Lansing s q u ir r e l population compositions do not occur evenly each y e a r . Rather i t seems t h a t small changes would occur follow ing e s p e c ia ll y s t r e s s f u l w in te rs . 101 M o rta lity With th e exception of h u n tin g , th e recorded known sources of m o r t a l i t y in r u r a l s q u ir r e l p o p u la tio n s are few. In an average y e a r , Uhlig (1956:53) re p o rte d t h a t 62% of th e f a l l population were young of th e y e a r . For th e population to remain s t a b l e , 62% m o r t a lit y must occur and, on th e average, he found hunting accounted f o r only 13% of th e f a l l p o p u la tio n . He noted t h a t p r a c t i c a l l y every r e p o r t on gray s q u i r r e l s concluded th e e f f e c t s of p re d a tio n were u su a lly not s e r io u s . Progulske (1955), however, found t h a t in V irg in ia gray s q u i r r e l s were second to r a b b its in th e d i e t of bo b c ats. Packard (1956:50) a lso noted t h a t while previous in v e s t ig a ti o n s of p re d a tio n on s q u i r r e l s had y ie ld e d an imposing l i s t of v e r te b r a te p re d a to rs , in most cases p re d a tio n had been considered r e l a t i v e l y unimportant to s q u ir r e l p o p u la tio n s . During a study of a cemetery population of s q u i r r e l s , Bakken (1952) re p o rte d only nine road k i l l s and Robinson and Cowan (1954) discovered only two s q u i r r e l s k i l l e d by c ars and two by p re d a to rs in an urban park s q u i r r e l p o p u la tio n , suggesting n e ith e r was a major source of m o r t a l i t y . Clark (1959) noted t h a t th e gray s q u ir r e l had fewer p a ra s ite '; than most o th e r small and medium siz e d mammals n a tiv e to th e U.S. and su p p lied an incomplete l i s t of 48 sp ec ie s of e c to p a r a s ite s and 30 sp e c ie s of e n d o p a ra s ite s . While c i t i n g p re d a to rs and highway k i l l s as c o n tr ib u tin g to m o r t a l i t y , D. Allen (1942:377) f e l t the most s e rio u s s i n g le f a c t o r in n a tu ra l m o r t a lit y was p a r a s i t e i n f e s t a t i o n , s p e c i f i c a l l y mange lin k e d with poor mast c ro p s. Brown and Yeager (1945), however, f a i l e d to support t h i s c o n te n tio n . Based on two years 102 of sampling, th e y found mange in only 0.03# of th e 722 fox s q u i r r e l s and 0.06# o f th e 353 gray s q u i r r e l s examined. They concluded t h a t the degree of i n f e s t a t i o n was n e g lig ib le in most woodland p o p u la tio n s , but t h a t a h eav ier r a t e p re v a ile d in some urban popu latio n s of both species of s q u i r r e l . In g le s (1947), however, re p o rte d t h a t a g re a t epidemic of sca b ie s in Bidwell Park, C a l if o r n ia , in 1913 elim in a te d a l l the s q u i r r e l s in s id e th e 2400 a cre park. The d is e a s e g r e a t l y reduced th e s q u i r r e l pop ulation throughout i t s range in th a t s t a t e between 1913 1921. Uhlig (1956:35) a lso mentioned t h a t th e sudden crash of a pop u latio n might well be a t t r i b u t e d to c o c c id io s is (a protozoan-caused d ia rrh e a in young s q u i r r e l s ) or m a ln u tritio n and mange, with th e s q u i r r e l s dying in t h e i r n e s t s . J . Allen (1952:102) found s a r c o p tic mange a t a l l times of the y e a r , but th e incidence was much higher during w inter when food was s h o r t. Since weight lo ss accompanied those with mange, he believed mange to be a secondary ailm ent follow ing d i e t a r y d e fic ie n c y . This work in d ic a te d t h a t th e study by Brown and Yeager, which found a low incidence of mange, may have been conducted during times of abundant food. The only o th e r s q u i r r e l e c to p a r a s ite s of any importance were f l e a s , which F itz w a te r and Frank (1944) found in 60# o f th e a c tiv e n e s ts examined. Kilham (1959:374) suspected t h a t mosquitoes were im portant v e cto rs of s q u i r r e l fibromas (benign tumors c o n s is tin g mostly o f fib r o u s t i s s u e ) . While a d u lt s q u i r r e l s were r e s i s t e n t , su ck ling ju v e n ile s were very s u s c e p tib le to th e tumor v i r u s . In th e East Lansing s q u ir r e l p o p u la tio n , th e degree of m o r t a lit y due to m a ln u tritio n and accompanying e c to p a r a s ite i n f e s t a t i o n s was undetermined. I t was b eliev ed to be a p p re c ia b le , however, e s p e c i a l l y 103 a t the end of th e sev ere Winter of 1978-79. The mast crop f a i l u r e of th e preceding f a l l probably c o n trib u te d g r e a t l y to the poor h e a lth of tho se in f e s te d s q u i r r e l s commonly observed during February and March, 1979. The black s q u i r r e l s then mostly had only bare patches on the head, w hile th e most s e r io u s ly mange-affected in d iv id u a ls were fox sq u irre ls. One fox s q u i r r e l , observed sunning i t s e l f on the edge of a driveway and using a t r e e trunk as p ro te c tio n a g a in s t th e wind, was bare over 75% of i t s body and allowed me to approach to w ithin 10 f e e t before slowly scrambling up th e nearby t r e e . Another fox s q u ir r e l observed sunning i t s e l f on th e low branches of a small t r e e , had f u r only on i t s legs and p a r ts of i t s t a i l . Raw bleeding areas a t the base of i t s t a i l and in th e shoulder region were obvious. This in d iv idu al allowed me to approach and touch i t s body with a p e n c il. While no mangy dead s q u i r r e l s were recovered, s q u i r r e l s d isp la y in g new growth of f u r over la rg e p a r ts of t h e i r bodies were never observed in l a t e March, in d ic a tin g those in d iv id u a ls with severe mange had probably died in t h e i r n e s ts . As was found in th e East Lansing stu d y , c ars probably account f o r a la rg e p a rt of s q u ir r e l m o r ta lity in a l l urban a re a s , even when d r iv e r s make a concerted e f f o r t to avoid h i t t i n g them, as has been observed f r e q u e n tly in th e re sea rc h a re a . E arly in the study i t was suspected t h a t fox s q u i r r e l s were more s u s c e p tib le to being h i t by cars because black s q u i r r e l s showed a g r e a te r preferen ce f o r c ro ssin g s t r e e t s by moving through th e t r e e s than fox s q u i r r e l s d id . During th e summer and f a l l of 1977, only one black s q u ir r e l was recovered as a car k i l l , w hile seven fox s q u i r r e l s were run over. This appeared to support the idea of g r e a te r fox s q u ir r e l s u s c e p t i b i l i t y to car 104 m o rtality . As th e study p ro g re s se d , however, th e number of recovered black s q u i r r e l c a r k i l l s in c re a s e d . This in c re a s e could p o s s ib ly be a t t r i b u t e d to th e in c re a s in g p ro p o rtio n of black s q u i r r e l s in th e re s e a rc h a re a . While moving through t r e e s and along w ire s , s q u i r r e l s were observed o fte n to make m is ta k e s . F a lls to th e ground were w itnessed on a number of o c c a s io n s, but only one f a t a l i t y was re c o rd ed . This in d iv id u a l, a ju v e n ile b la c k , f e l l from a t r e e to th e s t r e e t below and landed on i t s head. The only o th e r a c c id e n ta l s q u ir r e l f a t a l i t y was one which attem pted to escape from a box tr a p and managed to work i t s e l f halfway out of th e mesh wire end of th e t r a p . Caught by i t s w a ist and unable to move forward or backward, th e in d iv id u a l fr o z e in the snow. While two orphaned fox s q u i r r e l s , r a is e d in c a p t i v i t y and re le a s e d o u ts id e th e re s e a rc h a r e a , were l a t e r k i l l e d by dogs, no m o r t a l i t y due t o dogs was observed in th e re s e a rc h area or re p o rte d by r e s i d e n t s . C a ts, though, were su sp ected of being th e major p re d a to r upon s q u i r r e l s in urban a r e a s . Although only black s q u i r r e l c a t k i l l s were recov ered , th r e e r e s id e n ts in th e re s e a rc h are a observed t h a t t h e i r c a ts a lso k i l l e d fox s q u i r r e l s . One woman's c a t was re p o rte d to catch a t l e a s t one s q u ir r e l a week during summer and f a l l , most o fte n j u v e n i l e s . On th r e e o c ca sio n s, one man attem pted u n s u c c e ss fu lly to r e t r i e v e s q u i r r e l s t h a t h is c a t had k i l l e d , but th e c a t eluded him behind garages and through brush b a r r i e r s . Not a ll c a ts were k i l l e r s and th e s q u i r r e l s soon learn ed to d i f f e r e n t i a t e the " s i s s i e s " from th e k i l l e r s . One one occasio n , s q u i r r e l s feedin g on a p i l e of peanuts were observed to pass w ith in two 105 f e e t of a c a t c u rle d up by th e door of a house. Moments l a t e r , another c a t came around th e c o rn e r of th e house and a l l th e s q u i r r e l s s c a tte r e d f o r the t r e e s , c h a t t e r i n g lo u d ly . A fte r observing many c a ts s ta l k in g s q u i r r e l s , i t appeared t h a t the only chance a c a t had of k i l l i n g a s q u i r r e l was to approach unseen to w ith in te n f e e t and c atc h th e s q u ir r e l by th e back of th e neck and head in a quick ru s h . The th r e e r e t r i e v e d s q u i r r e l s k i l l e d by c a ts a l l had puncture wounds in th e s k u l l , neck and shoulder a re a . Once a s q u ir r e l n o tic e d a c a t s ta l k in g i t , th e c a t had v i r t u a l l y no chance of c atc h in g it. One black s q u i r r e l , observed feedin g a t a t r a p , was chased up a t r e e by a c a t . A fte r c h a tt e r i n g a t th e c a t from about s ix f e e t up th e t r e e tr u n k , th e s q u i r r e l descended and proceded toward th e c a t , which was between i t and th e tr a p where i t had been fe e d in g . When w ithin th r e e f e e t of th e c a t , th e s q u ir r e l made a quick lunge a t th e c a t , causing th e c a t to run about te n f e e t away. t r a p f o r a few more m inu tes, then moved away. The s q u ir r e l fed a t th e The c a t made no f u r t h e r attem pt to d i s t u r b th e s q u i r r e l . A goshawk was known to have spent a w in te r in th e re s e a rc h a re a , r e d t a i l hawks had been s ig h te d c i r c l i n g overhead on a number of occasio ns and a g r e a t horned owl was known to have been p re s e n t in th e re s e a rc h a re a throughout th e s tu d y . These p r e d a to r s , however, were f e l t to have been too few to have accounted f o r much s q u i r r e l m o rtality . Road k i l l s and c a t p re d a tio n were b e lie v ed to have been th e major sources o f m o r t a l i t y during th e s tu d y . A combination of m a ln u tritio n and d is e a s e a ls o were suspected of ta k in g an a p p re cia b le p o rtio n during w in te rs fo llow in g food s h o rta g e s . 106 Movements Daily A c tiv ity Rhythms in d a ily s q u ir r e l a c t i v i t y during th e year have been re p o rte d to follow v ario us p a tte r n s in d i f f e r e n t l o c a l i t i e s and environments. S tud ies conducted on gray s q u ir r e l and fox s q u ir r e l p o p ulatio ns in ru r a l woodlots and w ilderness areas led Brown and Yeager (1945) and J . Allen (1952) to id e n tic a l conclusions on t h e i r d a ily a c t i v i t y p a tte r n s in I l l i n o i s and In diana, r e s p e c tiv e ly . The gray s q u i r r e l s displayed a bimodal a c t i v i t y p a t t e r n , th ey found, being most a c tiv e in th e e a r ly morning and l a t e aftern o o n . The fox s q u i r r e l s , though, had a unimodal a c t i v i t y p a t t e r n , being most a c tiv e from l a t e morning on through midday. Hicks (1949), however, presented data in d ic a tin g a trimodal d a ily a c t i v i t y p a tte rn throughout the year f o r fox s q u i r r e l s in Iowa. Horwich (1972) a lso observed a trim odal summer rhythm f o r gray s q u i r r e l s in Maryland, and r e f e r r e d to a general trimodal curve re p o rte d f o r gray s q u i r r e l s in Great B r ita in by Shorten and C o u rtie r (1955). Thompson (1977b) a lso r e f e r r e d to Shorten and C o u rtie r (1955) as re p o rtin g th re e peaks in summer d iurnal a c t i v i t y . The 1955 a r t i c l e , however, made no statem ent and o ffe re d no data concerning d a ily a c tiv ity p a tte rn s. A check of the a v a ila b le l i t e r a t u r e f o r a r t i c l e s w r itte n by Shorten (1945, 1946, 1951, 1953, 1954, 1955, 1956, 1957a, 1957b, 1959a. 1959b, 1964 and T aylor, Shorten e t a l . , 1971), however, rev ealed only one statem ent concerning gray s q u ir r e l d a ily a c t i v i t y p a t t e r n s , t o which th e authors must be r e f e r r i n g : "The b a sic rhythm of a c t i v i t y shows th r e e peak p e rio d s , th e f i r s t and most important 107 o c c u rrin g between seven and ten a.m ., th e second f o r a s h o rt time around midday, and th e l a s t f o r about an hour b efore dusk" (Shorten, 1954:111). This statem ent by Shorten was not supported by d a ta and a c t u a l l y c o n f lic te d with a statem ent made e a r l i e r in th e book: "Early morning and l a t e afternoon a re th e c h ie f fe e d in g -tim e s , but when food i s abundant and th e weather f i n e , d e s u lto ry fe edin g goes on a l l day," (1 954:2). The argument f o r a trim odal a c t i v i t y p a tte r n f o r gray s q u i r r e l s i s a lso weakened by th e f a c t t h a t th e data o ffere d by Horwich (1972) concerned th e movements of a c a p tiv e sprin g l i t t e r as the ju v e n ile s ventured p ro g r e s s iv e ly f u r t h e r from th e n e s t during summer. No evidence could be lo c a te d which supported th e e x iste n c e of a trim odal d a ily a c t i v i t y p a tte r n during any season of th e year f o r a d u lt gray s q u i r r e l s . Bakken (1952) s tu d ie d gray and fox s q u ir r e l pop ulatio ns sh arin g th e same cemetery near Madison, Wisconsin. He found th e gray s q u ir r e l d a ily p a tte r n f o r sp rin g to have e a r ly morning and l a t e afternoon peaks, w hile th e summer and f a l l a c t i v i t i e s were i r r e g u l a r with i n t e r m i t t e n t su rg e s. The w in ter was more re g u la r than any o th e r season and showed a d e f i n i t e unimodal a c t i v i t y p a tte r n centered around the midday hours. U n fo rtu n ate ly , th e cemetery fox s q u i r r e l population and th e number of o b serv atio n s made on d a ily a c t i v i t y were too few to make comparisons with th e gray s q u i r r e l . Another cemetery population of gray s q u i r r e l s was stu d ie d by Thompson (1977b) in midtown Toronto, O n ta rio . That study in d ic a te d the gray s q u i r r e l s held b a s i c a l l y to a bimodal a c t i v i t y p a tte r n which was most pronounced in sunsner. Through f a l l , th e peaks were in c re a s in g ly d is p la c e d toward midday u n t i l a unimodal w in te r a c t i v i t y p a tte r n was 108 achieved. The re v e rs e occurred during sp rin g lead in g to th e summer bimodal p a t t e r n . Thompson suggested th e bimodal a c t i v i t y p a tte r n of summer could have r e s u lte d from s q u i r r e l s avoiding th e h o t t e s t p a r t of th e day, w hile th e s q u i r r e l s may have s e le c te d th e warmest p a r t of the day f o r a c t i v i t y during th e w in te r. The East Lansing black s q u ir r e l d a i l y a c t i v i t y p a tte r n s fo r s p rin g , summer and f a l l resembled th e Toronto gray s q u i r r e l a c t i v i t y p a tte r n s f o r spring and f a l l , having high le v e ls of a c t i v i t y throughout th e day. The absence of a midday l u l l in th e black s q u i r r e l ' s summer a c t i v i t y was th e most s t r i k i n g d iff e r e n c e between th e se two s q u ir r e l p o p u la tio n s . The w in ter a c t i v i t i e s of both populations showed a s im ila r unimodal p a t t e r n , except t h a t the Toronto s q u ir r e l population appeared to be a c tiv e e a r l i e r in th e morning. The e a r l i e r morning a c t i v i t y of th e Toronto gray s q u i r r e l s was apparent throughout th e y e a r . While p a r t of t h i s may have been due to Toronto being e a s t of East Lansing and experiencing s u n r is e e a r l i e r in th e same time zone, i t probably was more a r e f l e c t i o n of th e way the d a ta were c o lle c te d . Thompson recorded o b serv atio n s only during good weather (d efined as le s s than 40% cloud cover, winds of le s s than 10 mph and tem peratures approaching averages) to reduce th e e f f e c t of weather (1977:1186) and t h i s would tend to in c re ase th e le v el of measured a c t i v i t y in th e mornings. Observations on th e East Lansing black s q u i r r e l s were made re g a rd le s s of th e weather c o n d itio n s , and the in c lu s io n of many cold and inclement mornings would tend to reduce th e average measured a c t i v i t y l e v e l s . The East Lansing fox s q u i r r e l s d e f i n i t e l y showed a unimodal d a ily a c t i v i t y p a tte r n throughout the y e a r, as suggested by 0. A llen (1952) 109 and Brown and Yeager (1945). T h eir day began e a r l i e r in th e morning, however, and extended throughout th e e n t i r e day. There was no evidence o f a trim odal p a t t e r n as in d ic a te d in th e Iowa s q u ir r e l study by Hicks (1949). Reports f o r e i t h e r r u r a l or urban environments could not be found which compared th e d a ily a c t i v i t y p a tte r n s of sympatric black (gray) and fox s q u i r r e l popu lation s o f comparable p ro p o rtio n s. The East Lansing black and fox s q u i r r e l p o p ulation s were n e a rly e q u al, however, and the observed le v e ls of a c t i v i t y were a lso n e a rly eq ual. The d iff e r e n c e s between r u r a l and urban s q u ir r e l p o p u la tio n s , as in d ic a te d by th e urban black and fox s q u i r r e l s having n e a rly id e n tic a l d a ily a c t i v i t y p a tte r n s throughout th e y e a r , th e absence of th e midday l u l l in black s q u i r r e l a c t i v i t y and the ex tension of fox s q u ir r e l a c t i v i t y in to e a r ly morning and a f t e r midday, might have been accomodations of a high d e n s ity urban s q u ir r e l population to an abundant food supply. Were a l l th e in d iv id u a ls to feed a t th e "prime times" ty p ic a l of r u r a l s q u ir r e l p o p u la tio n s , an in c re a s e in c o n fro n ta tio n s might r e s u l t . A lengthening of the ty p ic a l a c t i v i t y periods by some in d iv id u a ls feed ing a t o th e r than prime times would avoid or reduce c o n fro n ta tio n s and a l l th e in d iv id u a ls would o b ta in t h e i r food requirem ents. Observations of s q u i r r e l behavior during l a t e s p rin g , summer and e a r l y f a l l suggested t h a t ag gressiv e i n t e r a c t i o n s then tended more often to be i n t r a s p e c i f i c in n a tu r e . t o l e r a n t (see Figu re 17). I n t e r s p e c i f i c behavior was most often The r e l a t i o n s h i p of s q u ir r e l a c t i v i t y periods to in tr a -a n d i n t e r s p e c i f i c s o c ia l s t a t u s w arrents in v e s t ig a ti o n . 110 Home Range Home range could be defin ed as th e are a an animal tra v e rs e d in th e normal a c t i v i t i e s of food g a th e r in g , m ating, c a rin g f o r young, n e s t and s h e l t e r c o n s tr u c ti o n , and o b ta in in g any o th e r requirem ents f o r a s u c c e ssfu l liv e lih o o d . This d e f i n i t i o n n e c e s s a r ily r e s t r i c t s th e term t o e s ta b lis h e d in d iv id u a ls and would not inclu de young of th e year as th e y moved away from th e n e s t b efo re th e y f i n a l l y e s ta b lis h e d themselves somewhere. Packard (1956:26} suggested t h a t home ranges of in d iv id u a l s q u i r r e l s might be l a r g e r in l e s s fa v o ra b le h a b i t a t than in fa v o ra b le site s. Flyger (1960:365) f e l t th e s u i t a b i l i t y of th e h a b i t a t may determ ine th e e x te n t of space re q u ire d to supply n e c e s s i t i e s and th e degree to which th e animals must move about in search of t h e i r re q u ire m e n ts. S tu d ies in r u r a l woodlots and f o r e s t s or c i t y parks and cem eteries in d ic a te d t h a t th e home ranges in th o se areas were m ostly la r g e r than th o s e observed f o r th e E ast Lansing r e s i d e n t i a l black and fox s q u i r r e l p op u la tio n (5-10 a c r e s ) . D. A llen (1943) thought fox s q u i r r e l s moved over 10 acres in a season and perhaps 40 a c re s throughout th e y e a r . Both D. A llen (1943) and Baumgartner (1943) suggested t h a t fox s q u ir r e l males moved more and f a r t h e r than fem ales. Packard (1956) in d ic a te d t h a t t h i s a p p lie d f o r both gray and fox s q u i r r e l s in Kansas. Longley (1963) b eliev ed th e gray s q u i r r e l s in th e woodlot he s tu d ie d in Minnesota probably covered most of the 40 acre study a r e a . In a cemetery a t Madison, W isconsin, Bakken (1952) observed t h a t gray s q u i r r e l males covered about 24 acres and gray fem ales approximately 10 acres. Fox s q u i r r e l fem ales, he s a id , moved over 13 a c re s but gave no d a ta f o r fox s q u i r r e l males. Based on measurements of d is ta n c e s gray Ill s q u i r r e l males and females moved from t h e i r den t r e e s , Robinson and Cowan (1954) e stim ate d t h a t Vancouver c i t y park gray s q u i r r e l males moved over th e e n t i r e study are a of 50-55 acres through th e y e a r , but t h a t females only moved over an are a of 5-15 a c r e s . Only F ly g e r 's (1960) stu dy of gray s q u i r r e l s in two 10 acre r u r a l Maryland woodlots and Thompson's (1978a) study of gray s q u i r r e l s in a Toronto cemetery re p o rte d home ranges comparable to or le s s than tho se o f th e East Lansing black and fox s q u i r r e l p o p u la tio n s . Home ranges of th e Maryland woodlot gray s q u i r r e l s v a rie d from 0 .2 - 7 .2 acres with an average of 1.4 a c r e s . The Toronto cemetery female gray s q u i r r e l s covered 4-5 a c re s and males about 5-10 acres most of th e y e a r . Longley (1963) f e l t th e lim ite d movements re p o rte d by Flyger were not t y p i c a l . He sp ecu lated t h a t th e c o n d itio n might be r e l a t e d to th e high d e n s ity of s q u i r r e l s ( 6 /a c re ) in th e Flyger stud y . A c o n d itio n which, he b e lie v e d , in d ic a te d t h a t the s q u i r r e l s must have had a c o n sta n t and adequate food supply. F l y g e r 's woodlots probably did supply adequate and v a rie d foods s in c e th ey c o n s is te d mainly of mature stands of la rg e mast producing t r e e s , some of which were up to fo u r f e e t in d . b .h . That f a c t o r was held in common with East Lansing and many o th e r urban a r e a s . Flyger (1970) emphasized th e top q u a l i t y s q u i r r e l h a b i t a t t h a t i s o ffe re d in many communities having mature uncrowded t r e e s w ith la r g e canopies p roviding e x c e lle n t s q u i r r e l food and s h e l t e r . many la rg e canopied Besides th e presence of t r e e s up to 52 inches d . b . h . in th e East Lansing a r e a , th e e x is te n c e o f supplemental fe e d e rs provided a generous food supply o v e rw in te r. Concerning behaviors a s s o c ia te d with fe e d in g , s o c ia l group and a g o n is t ic i n t e r a c t i o n s , Thompson (1978a) observed no seasonal 112 d if f e r e n c e s a t Toronto in th e use of space w ith in th e home rang e. Some East Lansing s q u i r r e l s , however, appeared s e a s o n a lly to feed in d i f f e r e n t p a r ts of th e home rang e. This may have been due p r im a r ily to th e clumped d i s t r i b u t i o n o f t r e e s th e r e (see Figure 3 ) . For example, s q u i r r e l s with both elm and h icko ry reg io ns w ith in t h e i r home ra n g e s, spent s p rin g and e a r l y summer in th e elm region and most of th e f a l l in th e hickory re g io n . The r e s u l t was t h a t , during any month or season, th e are a u t i l i z e d to o b ta in li v i n g requirem ents was only a p o rtio n of th e e n t i r e home range as c a lc u la te d on an annual b a s i s . Thompson (1978a) a lso re p o rte d a d if f e r e n c e between th e sexes in th e s iz e s of home ranges during th e w inter and summer mating p e rio d s . The fem ales' ranges remained about 4-5 a c r e s , w hile th e m ales' in creased to 15-30 a c r e s . F ly g e r 's (1960) study re v e ale d no s i g n i f i c a n t d if f e r e n c e between th e home range of th e a d u lt male and female gray s q u i r r e l , and no d if f e r e n c e appeared to e x i s t between sexes in e i t h e r th e black or fox s q u i r r e l s of East Lansing. The la r g e r home ranges f o r Thompson's Toronto male gray s q u i r r e l s during mating season p o s s ib ly may have been due to th e sp arse n ess of t r e e s on th e cemetery (about 3 /a c r e 13+ inches d . b . h . supplying about 45# canopy c o v e r). These supported a le s s dense s q u ir r e l po pu la tio n (about 1 . 7 5 / a c re ) and may have caused th e males to move f u r t h e r when mating in order to f in d fem ales in e s t r o u s . Mature woodlots w ith high s q u i r r e l d e n s i t i e s ( 6 /a c re ) o r p o rtio n s of urban a re a s , as in East Lansing, with p a r ts having 60+# canopy cover and 3+ s q u i r r e l s per a c r e , on th e o th e r hand, might o f f e r enough fem ales c lo s e by. In summary, th e home ranges of East Lansing black and fox s q u i r r e l s were sm aller than th o se re p o rte d f o r r u r a l s q u i r r e l p o p u la tio n s . 113 Probably t h i s was because th e urban environment provided a more c o n sta n t food supply throughout th e y e a r . There was a g r e a te r c o n c e n tra tio n of uncrowded t r e e s with la rg e can op ies, but a lso supplemental fe e d e rs m aintained by r e s id e n ts c e r t a i n l y played a r o l e . Food A v a i l a b i l i t y There was no g re a t d if f e r e n c e in foods used by black and fox s q u i r r e l s in East Lansing, and t h i s agreed with th e fin d in g s of J . Allen (1952) and Bakken (1952). While many e x o tic h o r t i c u l t u r a l v a r i e t i e s of t r e e s and shrubs were a v a ila b le to they fed mainly on tho se s p ec ie s a ls o used by ru r a l s q u ir r e l p o p u la tio n s . Robinson and Cowan (1954) and Thompson and Thompson (1980) a lso noted t h i s f o r the park and cemetery gray s q u ir r e l po p u latio n s they stu d ie d and concluded t h a t gray s q u i r r e l s were b a s i c a l l y c o n se rv a tiv e in t h e i r choice of foods. Thompson and Thompson (1980:708) mentioned t h a t "the only type of seed which was seen to be cached was th e husked nuts (h ic k o ry , oak, h o rs e -c h e s tn u t); none of th e various samaras was b u r i e d , " . behavior was also noted f o r th e East Lansing s q u i r r e l s . This During th e mast crop f a i l u r e in th e F all o f 1978, th e bumper crop of sugar maple seeds was v ig o rou sly atta ck e d in the t r e e s and l a t e r foraged f o r on the ground, but not once was a s q u ir r e l observed to bury any of th e se seeds. Hicks (1949) re p o rte d t h a t snow more than two inches deep impeded s q u ir r e l a c t i v i t y . Yet Brown and Yeager (1945) presented photographic evidence t h a t both fox and gray s q u i r r e l s r e a d i l y dug through a f o o t or more of snow to reach food. Experiments by Cahalane (1942) and Thompson and Thompson (1980) in d ic a te d t h a t smell was th e major f a c u l t y used by 114 th e gray s q u ir r e l to lo c a te buried n u ts . East Lansing s q u i r r e l s , however, were never observed to have dug through more than two inches of snow f o r buried n u ts . I t was q u ite p o s s ib le , due to th e a v a i l a b i l i t y of food a t supplemental fe e d e rs in r e s i d e n t i a l a r e a s , t h a t i t was not worthwhile f o r th e s q u ir r e l to dig through more than two inches of snow f o r a buried n u t, even i f i t could be lo c ated by sm ell. Sharp (1979) observed t h a t a t times of mast crop f a i l u r e s , s q u i r r e l s began d e s e r tin g h is study area by August. J . Allen (1952) and Longley (1963) re p o rte d t h a t during times of food s c a r c i t y in l a t e w in ter and e a r l y s p r in g , th e s q u i r r e l s s trip p e d bark from t r e e s f o r food. N either of th e se behaviors was ever observed in th e East Lansing a r e a , again probably because of th e presence of supplemental fe e d ers in r e s i d e n t i a l a re a s . Robinson and Cowan (1954) re p o rte d t h a t about o n e -th ird of the s q u i r r e l s in th e 60 acre study are a in t h e i r park made some use of a r t i f i c i a l food so u rc e s . P a r t i c u l a r l y during w in te r, a time of food s c a r c i t y and th e on set of the breeding season, unnatural foods were found to be more sought a f t e r than a t any o th e r season. Thompson and Thompson (1980) re p o rte d t h a t no "handouts" were sought or receiv ed by s q u i r r e l s in t h e i r Toronto cemetery study. Bakken (1952), however, noted t h a t th e s q u i r r e l s in h is Madison, Wisconsin, cemetery study were unfed except f o r one w in ter feeding s t a t i o n in a backyard bordering th e cemetery. T h is, he s a i d , was h e a v ily used by both gray and fox s q u i r r e l s in January and February. Black and fox s q u i r r e l s in th e East Lansing study area a lso r e l i e d h e av ily on the supplemental fe e d e rs during w in te r, and th e presence of th e se fe e d ers markedly changed th e fo rag in g behavior of th e s q u i r r e l s . 115 Pack e t a l . (1967) suggested t h a t in y e ars of mast s c a r c i t y when food was lim ite d in q u a n tity and c o n cen trated in a small a re a , sub ordin ate s q u i r r e l s p o s s ib ly could be re fu sed access to food. The presence of supplemental fe e d ers in r e s i d e n t i a l areas m ight, t h e r e f o r e , have influenced th e s t r u c t u r e of th e s o c ia l system of urban s q u i r r e l s and th e subsequent a llo tm e n t of food. I n t e r s p e c i f i c A ggressive Behavior Pack e t a l . (1967) and Thompson (1978a) s tu d ie d th e s o c ia l systems o f gray s q u ir r e l p o p u latio n s and Bernard (1972) did th e same f o r fox sq u irre ls. Bakken (1952) in v e s tig a te d th e i n t e r r e l a t i o n s h i p s of gray and fox s q u i r r e l s in mixed p o p u la tio n s , but mentioned l i t t l e of th e a ctu a l ag gressiv e i n t e r a c t i o n s between s p e c ie s , m ostly because of the low number of fox s q u i r r e l s in th e cemetery. In th e course of a y e a r, he recorded only fo u rte e n in s ta n c e s of gray s q u i r r e l s chasing fox s q u i r r e l s and nine in sta n c e s of fox s q u i r r e l s chasing gray s q u i r r e l s (1952:159). No r e p o r ts could be found in th e l i t e r a t u r e concerning the ag g ressiv e in te r a c t io n s of th e se two s p e c ie s . In th e n a tu ra l c o n d itio n where food was d isp erse d under tr e e s or s c a tte r-h o a rd e d by s q u i r r e l s , Thompson (1978a) found t h a t i n t r a s p e c i f i c aggression among gray s q u i r r e l s was v i r t u a l l y absent during w in ter because a s t a b l e dominance h e ira rc h y had been e s ta b lis h e d . Bakken (1952), however, noted t h a t in feedin g groups, in d iv id u a l a g gressio n, based on s ig n a lin g and ch asin g , was more e v id en t a t w in ter feeding s t a t i o n s on p r iv a te pro p erty a d jo in in g th e cemetery than in th e n a tu ra l feed ing a re a s . Bernard (1972) re p o rte d t h a t dominant fox s q u ir r e l in d iv id u a ls on an a r t i f i c i a l f e e d e r , lo c ated about s ix f e e t up a t r e e 116 tr u n k , did not allow o th e rs access to th e f e e d e r . On th e ground, however, a g g re ss iv e a c t i v i t y was disp lay ed l e s s f r e q u e n tly , with as many as th re e or fo u r animals fe e d in g peaceably in c lo se proxim ity to one a n o th e r. This behavior was a ls o f r e q u e n tly observed a t E ast Lansing fe e d in g s t a t i o n s which were in an e le v a te d p o s i t i o n . While one s q u ir r e l would dominate th e e le v a te d p la tfo rm , a number of o th e rs might be t o l e r a n t l y feed in g on th e s c a t t e r e d droppings below th e fe ed ing s t a t i o n . When a fe e d in g s t a t i o n was a t ground l e v e l , however, one in d iv id u a l a t a time used i t , and o th e rs w aited t h e i r tu rn or went elsew here to fo ra g e . These o b se rv a tio n s suggested t h a t food sources in n a tu re were d is p e rse d in such a manner t h a t i t would not be advantageous, or maybe not p o s s ib le , f o r an in d iv id u a l e x c lu s iv e ly to dominate a la r g e feedin g area. When food was p re sen te d in a small area t h a t could be e a s i l y dominated, however, as occurred a t a r t i f i c i a l f e e d e r s , a g g re ssiv e i n t e r a c t i o n s in c re ase d as in d iv id u a ls attempted to secure a food source f o r them selves. Bakken (1952:131) observed t h a t " in to le r a n c e in c re ase d n o tic e a b ly in both sp e c ie s in autumn. The beginning of th e g r e a te r in to le ra n c e v a rie d from y e a r to y e ar and appeared to c o r r e l a t e with th e s iz e of the mast cro p, as i t occurred e a r l i e r during y e ars of poor mast p ro d u c tio n ." An in c re a s e in a g g re ssiv e behavior a t t h i s time of th e year was a ls o observed in th e E ast Lansing s q u i r r e l s . However, i t was not only r e l a t e d to th e success o r f a i l u r e of th e f a l l mast cro p, but was a lso modified by th e s e v e r i t y or mildness of th e w in ter w eather. Bernard (1972:21) noted t h a t severe w in te r weather prompted an e a r l y form ation of a dominance h e ira rc h y among fox s q u i r r e l s and t h i s 117 led to very c o n s i s t e n t behavior p a t t e r n s . " I n t e r a c t i o n s were always s w i f t l y accomplished and th e v i c t o r n e a r ly always took h is p o s itio n on th e f e e d e r . " Pack e t a l . (1967) re p o rte d a r i g i d i t y in th e s o c ia l h e ira rc h y e s ta b lis h e d by th e gray s q u i r r e l s which r e s u lte d 1n i t s s ta b ility . Actual p h y sical combat was r a r e l y observed a t th e f e e d e r , w ith most s o c ia l i n t e r a c t i o n s being s e t t l e d by b lu f f i n g . Throughout the w in te rs in th e East Lansing re s e a rc h a r e a , i n t r a - and i n t e r s p e c i f i c i n t e r a c t i o n s a t th e fe e d e rs tended to be a m ixture of m ild , moderate and severe e n co u n te rs. While some in d iv id u a ls appeared to e s t a b l i s h t h e i r dominance a t a f e e d e r , th e y f r e q u e n t l y had to r e a ffirm i t with c h ase s. No rough-and-tumble combats, however, were ever observed. in d iv id u a ls were not dominant a t a l l f e e d e r s . Some I f th e fe e d e r they dominated became empty, th e y moved to another where th ey were sometimes s u b o rd in a te . Although th e presence o f a s o c ia l h e ira rc h y was not in v e s t ig a te d , some form of a complex i n t e r s p e c i f i c dominance h e ira rc h y was suspected to e x ist. Bernard (1972:22) noted t h a t "while dominants would feed to r e p le te n e s s in one hour and then d e p a r t, low ranking animals would sometimes remain th r e e o r fo u r hours e a tin g d iscard ed fragments and aw aitin g access to th e f e e d e r . " Smith and Follmer (1972:89) s t a t e d " sin c e th e n e s t serv es as i n s u la tio n f o r t r e e s q u i r r e l s , which have a t h i n f u r and high c r i t i c a l tem perature (H icks, 1949; Ir v in g , Krog, and Monson, 1955; and Muul, 1968), t h e i r w in te r energy requirem ents f o r m a in ta in in g a c o n sta n t body tem perature w ill in c re a s e in p ro p o rtio n to th e time sp ent out of th e n e s t ." Black s q u i r r e l s in E ast Lansing were o fte n observed to d is p la c e fox s q u i r r e l s a t f e e d e r s , which then waited 118 in nearby t r e e s f o r th e black s q u i r r e l s to f i n i s h fe e d in g . By dominating in encounters a t th e East Lansing supplemental fe e d e rs two or t h r e e times as o fte n as th e fox s q u i r r e l s , th e black s q u i r r e l s were b e lie v ed to have secured a more c o n sta n t food supply f o r them selves, w hile a t th e same time th ey reduced t h e i r exposure to w in te r w eather. This c e r t a i n l y must have enabled th e black s q u i r r e l s to m aintain a h e a l t h i e r physical c o n d itio n through th e w in te r than t h a t of th e l e s s f r e q u e n tly dominant fox s q u i r r e l s . Weather and Winter Weight F lu c tu a tio n s The weights of black and fox s q u i r r e l s in th e East Lansing stu dy during th e summer and f a l l compared fa v o ra b ly with th o se re p o rte d in s tu d ie s of ru r a l s q u ir r e l p o p u la tio n s (D. A lle n , 1943; Brown and Yeager, 1945; Bakken, 1952; Robinson and Cowan, 1954; Havera, 1977). w in ter months, however, a d if f e r e n c e was noted. During th e The average w in te r weight of the East Lansing a d u lt fox s q u i r r e l s (about 750 g) was le s s than t h a t (average = 800 g) re p o rte d by Bakken (1952) and th e w in ter w eights of th e East Lansing a d u lt black s q u i r r e l s (between 580 - 630 g) was h eav ier than t h a t (between 410 - 500 g) re p o rte d by J . A llen (1952) or by Bakken (average = 500 g; 1952). Packard (1956:46) re p o rte d t h a t a food sh o rtag e in th e Winter of 1954-55 reduced th e weight of both th e gray and fox s q u i r r e l s in Kansas. From December through March, he found t h a t a d u lt fox s q u i r r e l s l o s t 10-18 g/month, w hile young of th e previous year l o s t 20.5 g/month. In c o n t r a s t , a d u lt gray s q u i r r e l s l o s t 6 g/month and young of th e previous year l o s t 7.5 g/month. Adult fox s q u i r r e l s in th e E ast Lansing study 119 averaged a lo s s of between 35-40 g/month during th e w in te r. No data were obtained f o r fox s q u i r r e l ju v e n ile s or black s q u ir r e l a d u lts during th e w in te r, but th e black s q u ir r e l su b ad u lts averaged a gain of almost 3 g/month and th e black s q u i r r e l ju v e n ile s averaged a gain of almost 40 g/month. O v e ra ll, th e black s q u i r r e l s of East Lansing fa re d b e t t e r during th e w inter than r u r a l gray s q u ir r e l p o p u la tio n s , and East Lansing fox s q u i r r e l s fa re d worse than r u r a l fox s q u ir r e l p o p u la tio n s . It should be noted t h a t th e se recorded weight f l u c t u a t i o n s of black and fox s q u i r r e l s occurred during a mild w in te r. I t was suspected t h a t the d iff e r e n c e in weight g a in /lo s s between th e sp ec ie s may have been much g r e a te r during th e severe Winter of 1978-79 which followed a f a l l mast crop f a i l u r e . D. Allen (1942:365) re p o rte d t h a t poor h e alth may impede the breeding of a s q u i r r e l . J . Allen (1952:58) observed t h a t no pregnant females were trapped and few males appeared to be in breeding c o n d itio n in Janaury, February and March of 1947, follow ing th e f a l l mast crop f a i l u r e in 1946. As buds became a v a ila b le in March and A pril of 1947, s q u i r r e l weights increased and by May, males were found in breeding c o n d itio n and females in e s t r u s . All were capable of breed ing , but were fo u r months behind schedule. Havera (1977:293) f e l t i t was p o s s ib le t h a t some minimum le v el of body f a t may be needed f o r fox s q u i r r e l s to e n te r e s tr u s and t h a t a subnormal body c o n d itio n may e x p lain t h e i r lack of breeding. He a lso suggested t h a t a fox s q u i r r e l pop ulation with a low percentage of c arca ss f a t during th e w in ter breeding season may be expected to show reduced rep ro du ctio n in th e sprin g and perhaps a d e clin e in abundance or an in c re a s e in d is e a s e . I t is suspected t h a t th e East Lansing fox 120 s q u i r r e l s may have been f a i l i n g to m aintain a minimum of body f a t during severe w in te rs while th e black s q u i r r e l s m aintained t h e i r w eight. That th e black s q u i r r e l s had an edge in re p ro d u c tiv e success th e follow ing year e v id e n tly was due to t h e i r a b i l i t y to compete s u c c e s s f u lly f o r w inter foods. Nests Overwinter Leaf Nests S it e s While F itz w a te r and Frank (1944) and Robinson and Cowan (1954) found t h a t s q u i r r e l s in t h e i r study areas b u i l t th e m a jo rity of le a f n e s ts in c o n if e r s , most o th e r re s e a rc h e rs re p o rte d a stro ng p referen ce f o r oak t r e e s : black oaks held 3 /4 of the n e sts in Allegan County, Michigan (D. A lle n , 1942); most n e s ts were in oaks in an I l l i n o i s study (Brown and Yeager, 1945); a l l of th e summer and most of th e w in ter n e sts in B erk sh ire, England, were observed in oaks (S horten, 1951); J . Allen (1952) discovered 2/3 of th e n e sts in an Indiana study were lo c ated in oak, hickory and maple t r e e s (40% in oak); Uhlig (1956) noted 2/3 of the n e s ts in West V irg in ia were in beech, maple and oak t r e e s . Bakken (1952) re p o rte d n e s t b u ild in g by s q u i r r e l s in a Madison, Wisconsin, cemetery appeared to follo w a feed in g successio n: l a t e s p rin g in elms, summer n e sts in oak and h ic k o ry , and autumn and w inter in white oak. Nest b u ild in g in response to lo c a liz e d food a v a i l a b i l i t y appeared to occur among th e East Lansing s q u ir r e l pop ulation only during the hickory "nut c u ttin g " tim e of e a r ly f a l l . Most of th e se n e s ts f e l l in to d i s r e p a i r during w in te r, a f t e r they were abandoned in l a t e f a l l by ju v e n ile s which b u i l t them in th e summer and e a r ly f a l l . The observed p re fe re n ce among East Lansing s q u i r r e l s f o r oaks as n e stin g s i t e s was 121 probably due to th e o verw inter r e te n tio n of leaves by th e t r e e s . S q u ir r e ls were observed to g ath er th e se leaves throughout th e w in ter to use as added i n s u la tio n in l e a f n e s t s . Even s q u i r r e l s with n e s ts in o th e r t r e e sp e c ie s were observed g a th erin g oak le a v e s . The p r e f e r e n t i a l use of the oak region f o r w in ter n e stin g s i t e s was more im pressive when con sid e rin g th e f a c t s t h a t th e maple region was about twice as la rg e (see Figure 3) and contained a higher d e n s ity of supplemental fe e d e rs than the oak region (see Figure 16). The 50% in c re a s e in le a f n est numbers between th e Winter of 1978-79 and th e Winter of 1979-80 occurred mostly in maple t r e e s . Not only did t h i s r e s u l t in more n e s ts in the maple tr e e s in th e oak and elm re g io n s , but a lso in a ll th e t r e e s in the maple re g io n . This suggested t h a t the oak t r e e s may have been f u l l y occupied and th e s q u i r r e l s had to lo c a te in le s s p re fe rre d s i t e s , choosing maples over elms. Winter N esting Aggregations Bakken (1959) f r e q u e n tly observed n e stin g ag gregations which were more apparent during non-breeding p e rio d s . Uhlig (1956) g e n e ra lly found one gray s q u ir r e l f o r each l e a f n e st in l a t e f a l l , w hile Shorten (1954) mentioned fin d in g as many as nine to g e th e r in a n e s t in January. Bakken (1952), however, found th e l a r g e s t number of fox s q u i r r e l s in a n e st to be only f o u r , w ith seven f o r gray s q u i r r e l s . The most fox s q u i r r e l s observed to be sh aring a n e st in th e East Lansing study area was th r e e , while black s q u i r r e l s were fr e q u e n tly found fo u r to a n e s t. The s iz e of w in te r n e st aggregations was i n i t i a l l y b elieved to be p rim a rily an a d a p ta tio n f o r reducing energy lo ss during th e w in te r, a d ju s ta b le to meet th e needs of th e s i t u a t i o n . Were t h i s c o r r e c t , th e average ne st aggregation would be expected to be s i g n i f i c a n t l y d i f f e r e n t 122 du ring sev ere w in te rs or p o s s ib ly during w in te rs preceded by food s h o rta g e s . T h is , however, was not observed. The average s iz e s of th e black s q u i r r e l or fox s q u i r r e l w in te r n e s t a g g reg ation s were not s i g n i f i c a n t l y d i f f e r e n t ( a t th e .05 le v e l ) during severe w in ters (1977-78 and 1978-79) compared to a mild w in te r (1979-80), nor were they s i g n i f i c a n t l y d i f f e r e n t during a w in te r preceded by a food sh ortage (1978-79) compared t o a w in te r preceded by abundant food (1977-78). I t was a d i s t i n c t p o s s i b i l i t y t h a t th e abundance o f food a v a il a b le during w in ter a t th e supplemental fe e d e rs moderated th e impact of th e severe w in te r or food s h o rta g e . I f so , t h i s could r e s u l t in s im ila r w in te r n e s t ag g reg ation s iz e s f o r black and fox s q u i r r e l s from y e a r to year. I t seemed l i k e l y , however, t h a t energy c o n se rv a tio n was j u s t one of a'number of f a c t o r s determ ining aggregation s i z e . Other f a c t o r s may have been p h y s ic a l, h e a lth r e l a t e d or s o c i a l - f a m i l i a l in n a tu r e . A maximum s iz e to th e n e s t may be d ic ta te d by th e phy sical l i m i t a t i o n s of the t r e e to support th e n e s t , and th e th ic k n e s s of th e in s u l a t i o n needed in a given c lim ate may l i m i t th e in t e r n a l occupancy space. An in creased chance of spreading e c t o p a r a s i t e s among nestm ates might a lso l i m i t la r g e r a g g re g a tio n s . Many of th e l a r g e r a g greg ation s observed appeared to have been s i b l i n g su b ad u lts w ith an a d u lt female which were s t i l l n e s tin g to g e th e r w hile th e s i n g l e n e s ts were o fte n occupied by a d u lt males. The e f f e c t of th e s e s o c ia l a sp e c ts on agg regatio n s iz e m e rit f u r t h e r i n v e s t i g a t i o n . I n t e r a c t i o n s with People The major unique f e a t u r e of th e urban environment was th e presence o f abundant fo od , found m ostly a t supplemental f e e d e r s . The m a jo rity 123 o f th e se f e e d e rs was intended to be used e x c lu s iv e ly by b ird s and much e f f o r t was expended by some r e s i d e n t s in a ttem p ts to s q u i r r e l - p r o o f th e feeders. While th e s e e f f o r t s discouraged many s q u i r r e l s , no f e e d e r in th e re s e a rc h are a ever succeeded in being t o t a l l y s q u i r r e l - p r o o f f o r long, although two did succeed in d isco u rag in g a l l but one in d iv id u a l sq u irre l. The re s o u rc e fu ln e s s of th e s q u i r r e l s which f r u s t r a t e d th e r e s i d e n t s ' e f f o r t s was o fte n admired and provided a source of p le a s u ra b le com petition between man and b e a s t. The management o f in d iv id u a l nuisance s q u i r r e l s could be accomplished by h a b i t a t m anipulation to make an are a u n s u ita b le f o r s q u i r r e l s or by th e an im al-p ro o fin g of b u ild in g s . Solving th e nuisance problem by th e removal of an e n t i r e sp e c ie s from a la r g e a r e a , however, would seem u n lik e ly t o succeed. Flyger (1970) suggested th e in tr o d u c tio n of fox s q u i r r e l s in to urban communities to re p la c e th e gray s q u i r r e l s , which appeared to be more prone to n e s t in houses. From th e exp erien ce of M a rsh a ll, Michigan, and th e evidence from t h i s stu d y, however, i t can be expected t h a t j u s t th e o p p o site would occur. For most people in th e East Lansing re s e a rc h a re a , th e presence of black and fox s q u i r r e l s added to th e q u a l i t y of l i f e in th e urban environment. An a p p r e c ia tio n f o r th e values of s q u i r r e l s was shown by d r iv e r s who would sto p t h e i r c ars f o r s q u i r r e l s c ro s sin g r e s i d e n t i a l s t r e e t s or swerve to avoid h i t t i n g them. I t was a lso demonstrated by a few r e s i d e n t s who put up n e s t boxes f o r them. But most of a l l , i t was expressed by tho se r e s i d e n t s who c o n s c ie n tio u s ly m aintained supplemental fe e d e rs during w in te r . On th e a re a s tu d ie d , humans g r e a t l y a l t e r e d th e environment, b e n e f itin g both s p ec ie s o f s q u ir r e l and probably a number of o th e r urban w i l d l i f e s p ec ie s as w e ll. SUMMARY The ecology of an urban s q u ir r e l po pu la tio n was stu d ie d and compared w ith da ta on r u r a l s q u ir r e l p o p u la tio n s . The s q u ir r e l p o p u lation in a 200 acre r e s i d e n t i a l are a of East Lansing, Michigan was composed of fox s q u i r r e l s ( Sciurus n ig e r) and m e la n is tic gray s q u i r r e l s ( S. c a r o l i n e n s i s ) . and e a r ly I 9 6 0 's . The l a t t e r were introduced during th e l a t e 1950's During th e 36 month study (June 1977 - May 1980), 128 s q u i r r e l s (81 black and 47 fox) were in d iv id u a lly marked w ith dyes and observed f o r more than 4,000 h o urs. The main body of th e black s q u i r r e l p op u la tio n occupied much of East Lansing. An a d d itio n a l eleven is o l a t e d p o p ulation s were s c a tte r e d throughout the G re a te r Lansing a re a . Black s q u i r r e l s were tr a n s lo c a te d by r e s id e n ts wishing to have them in t h e i r neighborhoods. T heir d is p e r s a l was aided a ls o by th e in d is c rim in a te r e l e a s e of captured nuisance s q u i r r e l s by animal c o n tro l a g en ts. Marked and unmarked black and fox s q u i r r e l s were counted during p e r io d ic w in ter surveys which followed a predeterm ined course through a 50 acre tra p p in g are a w ith in th e re s e a rc h a re a . P opulation e s tim a te s were derived from th e se d a ta using B a i le y 's modified form ula of th e P e te rse n e s tim a to r . E ast Lansing s q u ir r e l d e n s i t i e s were g r e a te r than most r u r a l gray and fox s q u i r r e l d e n s i t i e s . Total (black and fox ) • s q u i r r e l d e n s i t i e s measured during th r e e w in te rs ranged between 1.6 and 124 125 2 .4 /a c re . S q u irre l d e n s i t i e s in th e autumns preceding those w inters were believed to have been between 2 . 0 - 4 .0 / a c r e . Average black s q u ir r e l l i t t e r s iz e (3.16 ± .16) was la r g e r than t h a t re p o rte d f o r ru r a l gray s q u ir r e l p o p u la tio n s , and th e average fox s q u ir r e l l i t t e r s iz e (2.66 + .16) was comparable to t h a t re p o rte d f o r r u r a l fox s q u ir r e l p o p u la tio n s . The mean s iz e s of black and fox s q u i r r e l l i t t e r s were not s i g n i f i c a n t l y d i f f e r e n t in the Springs of 1978 or 1980. Following a f a l l mast crop f a i l u r e and a severe w in te r, however, th e average black s q u ir r e l l i t t e r in th e Spring of 1979 was s i g n i f i c a n t l y (.001 le v e l ) la r g e r than th e average fox s q u i r r e l l i t t e r . Also during the Spring of 1979, both black and fox s q u ir r e l young emerged from th e n e st s i g n i f i c a n t l y (.001 le v e l) l a t e r than th ey had in th e Springs of 1978 and 1980. While both species had l a t e l i t t e r s t h a t s p rin g , th e fox s q u i r r e l l i t t e r s were even l a t e r than th e black s q u i r r e l s ( s i g n i f i c a n t a t the .001 l e v e l ) . Road k i l l s and c a t p re d a tio n were th e major sources of s q u ir r e l m o r t a lit y in t h i s urban a re a . Black and fox s q u i r r e l s appeared e q u a lly s u s c e p tib le to being k i l l e d by autom obiles. This may have been in flu e n c e d , however, by a g r e a te r p ro po rtion of black s q u i r r e l s in the t o t a l population during th e l a s t year of th e stu d y . Not a l l c a ts preyed upon s q u i r r e l s and th e s q u i r r e l s ap p aren tly learned to d is tin g u is h th e in d iv id u a l c a ts which were non -h un ters. M aln u tritio n and mange were ev id en t during l a t e w inter and were suspected of c o n trib u tin g a p p re cia b ly to s q u ir r e l m o r t a lit y during severe w in te rs . D aily a c t i v i t y le v e ls of East Lansing s q u i r r e l s were much higher throughout th e year than re p o rte d f o r r u r a l s q u ir r e l p o p u la tio n s . Both 126 black and fox s q u i r r e l s were s im ila r in t h e i r a c t i v i t y p a t t e r n s , showing high le v e ls of a c t i v i t y from 9 AM - 5 PM. I t was suspected th e s e high l e v e l s were an accomodation of th e high d e n s ity urban s q u ir r e l popu lation to an abundant food supply. Some in d iv id u a ls might have been fe ed in g a t o th e r than the prime times found to be ty p ic a l of r u r a l s q u ir r e l p o p u la tio n s so as to avoid or reduce urban i n t r a - or i n t e r s p e c i f i c c o n fr o n ta tio n s . The home ranges of East Lansing black and fox s q u i r r e l s (5-10 acres in s iz e ) were sm aller than t h a t re p o rte d f o r ru ra l s q u ir r e l p o p u la tio n s . I t was b eliev ed t h i s was due to th e more c o n sta n t food supply provided by th e urban environment throughout th e y e a r , not only from a g r e a te r c o n c e n tra tio n of uncrowded t r e e s with la rg e canopies, but also from supplemental fe e d e rs maintained by r e s i d e n t s . There was no g re a t d if f e r e n c e in food sp ec ie s eaten by black and fox s q u i r r e l s in East Lansing. In s p i t e o f th e presence of many e x o tic h o r t i c u l t u r a l v a r i e t i e s of t r e e s and sh rub s, urban s q u i r r e l s fed mainly on those n a tiv e sp ec ie s a ls o used by ru r a l s q u ir r e l p o p u la tio n s . East Lansing s q u i r r e l s did not d e s e r t th e area a t a time of mast crop f a i l u r e and were never observed to s t r i p bark from tr e e s or dig through more than two inches of snow during th e w in te r. These t r a i t s were a t t r i b u t e d to th e abundance of food supplied by th e ubiqu ito us supplemental f e e d e r s . Over 30% o f the r e s id e n ts in the re sea rc h area m aintained such f e e d e r s , an average of 1.25 fe e d e rs per a c re . This sup plied almost every s q u i r r e l n e stin g overw inter in the re sea rc h area with a t l e a s t f iv e fe e d e rs w ith in i t s home range from which to supplement i t s n a tu ra l food supply. 127 During l a t e s p rin g , summer and e a r ly f a l l , urban s q u i r r e l s fed t o l e r a n t l y in mixed groups on n a t u r a l l y occurrin g food sources which tended to be d isp erse d over la rg e areas (thousands of square f e e t ) . Once snow had accumulated to more than two in c h es, however, s q u i r r e l s turn ed to th e more e a s i l y o b ta in a b le s u p p lie s a t supplemental fe e d e rs . These co ncen trated food sources were e a s i l y dominated by in d iv id u a l s q u i r r e l s and during w in te r, th e le v e ls of i n t e r s p e c i f i c aggression increased d ra m a tic a lly . Black s q u i r r e l s e x ce lle d a t dominating f e e d e r s , d riv in g away or warning o f f fox s q u i r r e l s two or th re e times as o fte n as they were driven away or warned o ff by fox s q u i r r e l s . Although th e presence of a s o c ia l h e ira rc h y was not in v e s tig a te d , some form of a complex i n t e r s p e c i f i c dominance h e ira rc h y was suspected to e x ist. Weight f l u c t u a t i o n s o f the East Lansing s q u ir r e l population were followed through th e Winter of 1979-80. Black s q u ir r e l success in m a in tainin g weight during w inter was a t t r i b u t e d to t h e i r a b i l i t y to dominate a t the supplemental fe e d e r s . Oak t r e e s were p re fe rre d f o r overw inter l e a f nest s i t e s , probably because th e w inter r e t e n t i o n of dead leaves t r e e s o ffe re d a continual source of in s u la tin g m a te ria l during w in te r. Maples appeared to be second in p re fe re n ce f o r l e a f n e st s i t e s . Average w in ter n e st aggregation s iz e f o r black s q u i r r e l s was s i g n i f i c a n t l y (.01 le v e l) la r g e r than t h a t of th e average fox s q u i r r e l . The average s iz e s of black and fox s q u ir r e l w in ter n e st aggregations did not s i g n i f i c a n t l y (.0 5 le v e l) change in response to more severe w in te r weather or to food sh o rtag es preceding the w in te r. The 128 a v a i l a b i l i t y of food a t supplemental fe e d e rs during w in te r were b e lie v e d to have moderated th e impact of th e se f a c t o r s . RECOMMENDATIONS Management 1) The in c re a s in g d e s ir e of urban r e s i d e n t s to observe w i l d l i f e near t h e i r homes may lead to unplanned tr a n s l o c a t i o n s of animals n a tiv e to o th e r p a r ts of th e s t a t e or to in tr o d u c tio n s from o u t - o f - s t a t e . Local governments should work with th e S ta te Department of Natural Resources to c l a r i f y s t a t e r e g u la tio n s p e r ta in in g to urban w i l d l i f e . Local ordinances to p r o h i b i t in tr o d u c tio n s w ithout p r i o r study of th e p o te n tia l consequences may be re q u ire d . 2) While u n r e s t r i c t e d movements of c a ts in some urban areas may a s s i s t in mouse and r a t c o n t r o l , i t can a lso r e s u l t in p re d a tio n upon some d e s ir a b le w i l d l i f e sp ec ie s (both b ird s and mammals). In such communities, c a t - l e a s h , confinement or impoundment laws should be considered to p r o te c t small w i l d l i f e s p ec ie s from e x ce ssiv e p re d a tio n . 3) Animal c o n tro l departments re s p o n s ib le f o r c o n tr o llin g nuisance animals in urban areas should s e t a p o lic y of r e le a s in g such captured in d iv id u a ls only in to tho se areas where th ey are a lre a d y found. 129 130 Fu ture Research 1) Red s q u i r r e l s . Red s q u i r r e l s now appear to be abundant enough in East Lansing r e s i d e n t i a l are as to be a f a c t o r in flu e n c in g black and fox s q u i r r e l p o p u la tio n s . A study to in v e s t i g a t e t h e i r r e l a t i o n s h i p s to black and fox s q u i r r e l s a t th e supplemental f e e d e r s , to determine whether com petition f o r n e s tin g s i t e s o c cu rs, and t o a ss e ss whether t h e i r t e r r i t o r i a l n a tu re a f f e c t s th e n o n - t e r r i t o r i a l black and fox s q u i r r e l s should be conducted. 2) Black s q u i r r e l s on th e MSU campus. A study could determine how human a c t i v i t y le v e l s on campus compare with th o se in r e s i d e n t i a l a re a s and whether t h i s i s a l i k e l y f a c t o r in th e f a i l u r e of black s q u i r r e l s to e s t a b l i s h themselves on campus. The in v e s t ig a ti o n might also determ ine what happens to black s q u i r r e l s which come on campus during th e " f a l l s h u f f le " and whether ju v e n ile s could be introduced on campus and induced to s t a y . The s t a t u s of black s q u i r r e l s in Sanford Woodlot and whether they are spreading on th e e a s te rn p a r t of campus could must also be examined. 3) P opulation com parisons. The d i s t r i b u t i o n and abundance of black s q u i r r e l s in E ast Lansing and th e G re ater Lansing areas should be determined along with p o pu latio n e s tim a te s and th e p o p u la tio n composition (b1ack:fox) in the same 200 acre re s id e n tia l area. Comparisons with 1977-80 da ta could i n d ia te whether black s q u i r r e l s are d is p la c in g th e fox s q u i r r e l s as occurred in M a rsh a ll, Michigan. 131 4) Social h e ir a r c h y . A w in te rtim e study should be conducted inv olv in g a number of supplemental fe e d e rs and a l l th r e e s q u i r r e l sp e c ie s ( r e d , black and fox) in which every in d iv id u a l i s i d e n t i f i a b l e to determ ine whether a s t a b l e i n t e r s p e c i f i c s o c ia l h e ira rc h y i s e s ta b lis h e d . 5) D aily a c t i v i t y . A study could be made to determ ine whether a l l in d iv id u a ls are a c ti v e throughout the day or only a t d i f f e r e n t time p eriod s s e le c te d to avoid c o n fr o n ta tio n s . The in flu e n c e of an i n d i v i d u a l 's i n t r a - o r i n t e r s p e c i f i c s o c ia l p o s itio n upon i t s time o f a c t i v i t y might a lso be in v e s t ig a te d . 6 ) M o rta lity c a u s e s . An in te n s iv e study on c a t p re d a tio n should determ ine whether th e y c o n tr ib u te more to urban s q u ir r e l m o r t a l i t y than do autom obiles. The f a t e of mangy, under­ nourished in d iv id u a ls p re v a le n t during l a t e w inter must a lso be determined. 7) R eproductive s u c c e s s . The p re s e n t study c o n ce n tra te d on average l i t t e r s i z e and th e time of appearance of sp rin g litte rs. No inform ation was obtained on th e number of females having two l i t t e r s per y e a r . An improved measure of average re p ro d u c tiv e success conducted to determ ine whether th e re are s i g n i f i c a n t d i f f e r e n c e s between black and fox s q u i r r e l s in an urban a re a i s d e s i r a b l e . 8 ) N e stin g . A s tu d y o f th e n e stin g p re fe re n ce s o f urban s q u i r r e l s could determ ine whether th e r e i s a s i g n i f i c a n t d if f e r e n c e between black and fox s q u i r r e l s in t h e i r use of homes and o th e r man-made s t r u c t u r e s . APPENDIX A 132 APPENDIX A Research e x p lanation s h e e t d i s t r i b u t e d to r e s id e n ts of re sea rc h area at beginning of East Lansing s q u ir r e l study My name i s John Fogl and I'm doing re sea rc h on th e behavioral and eco lo g ical in t e r a c t i o n s between fox s q u i r r e l s (Sciurus n ig e r) and black s q u i r r e l s (Sciurus c a r o l i n e n s i s . m e la n is tic phase) in th e urban environment of East Lansing. The s i t u a t i o n here is unique in t h a t sp ec ie s (black s q u i r r e l ) has been introduced in to a h a b i t a t already one occupied by a c lo s e ly r e l a t e d s p ec ie s (fox s q u i r r e l ) having n e arly i d e n tic a l requirem ents and has managed to in c re a s e i t s population in th e fa c e of com petition from t h i s e s ta b lis h e d s p e c ie s . I am in te r e s t e d in what th e black s q u i r r e l is doing t h a t has r e s u lte d in t h i s remarkable in c re ase sin ce i t s in tro d u c tio n on the MSU campus 20 y e ars ago. Recent o b serv ation s have in d ic a te d th e re i s no a g gressiv e behavior d isp layed during fe e d in g , each sp ec ie s e i t h e r ignoring or avoiding th e o th e r . I , t h e r e f o r e , suspect th e f a c t o r most in flu e n c in g t h i s p o p u latio n in c re a s e in black s q u i r r e l s may be n estin g behavior. The females mate in Dec-Jan and have t h e i r l i t t e r s in Jan-Feb. A fte r nursing them in th e n e s t f o r 10 weeks, th e young of t h i s spring l i t t e r come out on t h e i r own in March, A p r il, and May. then mate again to produce a summer l i t t e r which w ill be Thefemales may on t h e i r own 133 by O ctober. A study r e l a t i n g to s q u i r r e l n e s tin g behavior must th e r e f o r e be conducted through t h i s e n t i r e p e rio d . In o rd er to g a th e r s p e c i f i c d a ta about n e s ti n g , i t w ill be n e ce ssa ry to i d e n t i f y s q u i r r e l s as i n d iv id u a ls . This w ill be accomplished by c a p tu r in g , ta g g in g and marking as many s q u i r r e l s as p o s s ib le . S q u ir r e ls have never been in t h i s stu d y , and have only died of in ju re d by th e boxt r a p to be used shock when l e f t in th e tr a p o v e rn ig h t or harassed by a p re d a to r ( c a t , dog or human). th e tr a p s a f t e r th e morning a c t i v i t y By checking period and a ls o s h o r t l y before s u n s e t, I hope to avoid any lo s s of s q u i r r e l s . A numbered ta g w ill be placed in each e a r of every captured s q u i r r e l , a process as p a in le s s as g e t t i n g your e a rs p ie rc e d . Since th e s e ta g s are r a r e l y l o s t , a tagged s q u i r r e l can be i d e n t i f i e d when handled again or when i t s body i s recov ered. The f u r on c e r t a i n body re g io n s w ill be bleached w ith hydrogen pero x id e , along with a combination o f numbers and l e t t e r s . This code bleached in to th e a n im a l's sid e f u r should be e a s i l y d i s c e r n i b l e a t a d is ta n c e . Since s q u i r r e l s molt in l a t e s p r in g , th e y w ill have to be re tra p p e d during summer, i d e n t i f i e d by e a r ta g number and re -b le a c h e d . H opefully, t h i s re s e a rc h w ill be accomplished w ith in th e next year. Your a s s is ta n c e in th e follow ing ways would c o n tr ib u te g r e a t l y t o t h i s re s e a rc h p r o j e c t . 1. Discourage c h ild r e n , c a ts and dogs from d is tu r b in g th e t r a p s or h a ra ss in g any s q u i r r e l s a lre a d y in th e t r a p s . 2. Recover any fox or black s q u i r r e l s r e c e n t l y k i l l e d in your neighborhood. Place i t in a p l a s t i c bag along with a note on when, where and how i t was k i l l e d . The te e t h can be used to a c c u r a te ly age i t , th e re p ro d u c tiv e organs of th e female can g iv e inform ation about s i z e of re c e n t l i t t e r s , and the s k e le to n and sk in preserved in th e MSU Museum c o l l e c t i o n . (D on't b o th er w ith a s q u i r r e l i f th e body i s badly crushed an d /o r decomposed as 3. i t would most l i k e l y be u s e l e s s . ) C o n trib u te inform ation about s q u ir r e l a c t i v i t y near a n e s t or o th e r i n t e r e s t i n g behavior of s q u i r r e l s t h a t was observed. Should you wish to ge t in touch with me, my o f f i c e phone i s 355-1725 (8 AM - 5 PM) and my home phone i s 351-4212. checking tr a p s an hour or two b efo re su n se t and would be happy to t a l k w ith you a t t h a t tim e. Your c o o p eratio n is g r e a t l y a p p re c ia te d . I a ls o w ill be APPENDIX B 13b APPENDIX B News r e l e a s e prepared by th e Michigan S ta te U n iv e rs ity O ffice of Inform ation S ervices which appeared in lo c a l newspapers during J u ly , 1980. EAST LANSINGITES ASKED TO COUNT SQUIRRELS In th e l a t e 1950s on th e MSU campus. and e a r l y '6 0 s , 20 black s q u i r r e l s were re le a s e d They promptly moved o f f campus in to th e c i t y of East Lansing. Today, t h e i r descendants are being found throughout th e Lansing a re a . And t h e r e 's some concern t h a t th e more a g g re ssiv e black s q u i r r e l s may be g ra d u a lly d is p la c in g th e la r g e r fox s q u i r r e l s , as they have in Marshall and some o th e r Michigan c i t i e s . U n fo rtu n a te ly , no one surveyed th e fox s q u i r r e l po pu la tio n b efore th e black s q u i r r e l s were r e le a s e d , so no one knows f o r sure whether the b lack s q u i r r e l s are d is p la c in g th e fox s q u i r r e l s here or merely c o e x is tin g with them. "What we do know," says John F ogl, a d o c to ra l c an d id a te in th e Department of F is h e r ie s and W ild lif e a t MSU," i s t h a t once we had 100 p ercen t fox s q u i r r e l s . Now we have a mix of black andfox s q u i r r e l s t h a t are competing f o r food and n e s tin g s i t e s . " Fogl i s studying th e d i s t r i b u t i o n of black s q u i r r e l s in th e Lansing-East Lansing area to f in d out how th e introduced black s q u i r r e l s are succeeding in r e l a t i o n t o the fox s q u i r r e l s . He hopes to e s t a b l i s h a benchmark which l a t e r r e s e a rc h e r s can use to monitor changes in th e s q u i r r e l p o p u la tio n . To do t h i s , he i s tra p p in g and 136 marking s q u i r r e l s with ear t a g s , dye and bleach and asking lo c a l re s id e n ts to l e t him know where black s q u i r r e l s a re . Drop him a postcard in care of the MSU Department of F is h e r ie s and W ild lif e , he a sk s, t e l l i n g him how many black s q u i r r e l s can be found in your v i c i n i t y , and give a s t r e e t i n t e r s e c t i o n . H e 'll take i t from th e re . "With enough in fo rm atio n , I could document where th ey are now and to what e x te n t they have been s p re ad ," Fogl say s. "Then f u tu r e re s e a rc h e rs w ill have some data to compare t o . " Another aim of t h i s p r o je c t i s to id e n t i f y to p ic s f o r f u tu r e stu d ie s. Why th e s q u i r r e l s p re fe r East Lansing to th e campus i s an obvious q u e stio n . How th e s q u i r r e l s have spread so f a r away from the r e le a s e point is ano ther. (Fogl surmises t h a t s q u i r r e l s trapped as nuisances in East Lansing have been haphazardly — and p u rp o s e fu lly — re le a s e d in o th e r a r e a s ) . The r o le of b ird fe e d e rs in th e success of th e black s q u i r r e l ' s a d ap ta tio n is something Fogl is p a r t i c u l a r l y i n t e r e s t e d in . He susp ects th a t the black s q u i r r e l s , which tend to be more ag g ressiv e in defending a food s o u rc e, dominate bird fe e d e rs in th e w in te r. In a harsh w in ter when n a tu ra l food i s in sh o rt supply, t h i s dominance would r e s u l t in t h e i r coming through the w inter in b e t t e r c o n d itio n than th e l e s s agg ressive fox s q u i r r e l s . re p ro d u c tiv e advantage: T h is, in t u r n , would give them a they would probably breed e a r l i e r and produce an e x tr a l i t t e r of young per y e a r . Over tim e, t h a t could give them the advantage of numbers. 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