BULLETIN Fox Squirrels and Gray Squirrels

Home , Fauna of Illinois

STATE OF ILLINOIS DwiGHT H. Green, Governor DEPARTMENT OF REGISTRATION AND EDUCATION Frank G. Thompson, Director

NATURAL HISTORY SURVEY DIVISION

Theodore H. Prison, Chief

\'olume 23 BULLETIN Article 5

Fox Squirrels and Gray Squirrels

In Illinois

LOULS G. BROWN LEE E. YEAGER

Printed by Authority of the State of Illinois

URBAN A, ILLINOIS

September 1945 STATE OF ILLINOIS DwiGHT H. Green, Governor DEPARTMENT OF REGISTRATION AND EDUCATION Frank G. Thompson, Director

BOARD OF NATURAL RESOURCES AND CONSERVATION Frank G. Thompson, Chairman William Trelease, D.Sc, LL.D., Biology* Arthur Cutts Willard, D.Eng., LL.D.,

Ezra J. Kraus, Ph.D., D.Sc, Forestry President of the University of Illinois L. R. HowsoN, B.S.C.E., C.E., Engineering Norman L. Bowen, Ph.D., Geology Roger Adams, Ph.D., D.Sc, Chemistry

NATURAL HISTORY SURVEY DIVISION Urbana, Illinois

Scientific .\nd Technical Staff Theodore H. Prison, Ph.D., Chief Florence A. Nyberg, Assistant to the Chief

Section of Economic Entomology Section of Aquatic Biology George W. Bennett, Ph.D., Limnologist G. C. Decker, Ph.D., Entomolgist D. F. Hansen, Ph.D., Assistant Zoologist Entomolo- M. D. Farrar, Ph.D., Research Paul G. Barnickol, M.A., Ichthyologist gist

J. H. Bigger, M.S., Associate Entomologist Section of Game Research and Managemer S. C. Chandler, B.S., Southern Field Ento- mologist R. E. Yeatter, Ph.D., Game Specialist James W. Apple, M.S., Northern Field Entomologist (on leave) Section of Wildlife Experimental Areas B. G. Berger, M.A., Assistant Entomologist Arthur S. Hawkins, M.S., Game Tech John M. Wright, B.A., Assistant Ento- nician (on leave) mologist (on leave) F. C. Bellrose, Jr., B.S., Associate Gam H. B. Petty^ Jr., M.A., Associate in Ento- Technician mology Extension Harold C. Hanson, M.S., Assistant Gam

C. J. Weinman, Ph.D., Special Research Technician Assistant Willis N. Bruce, B.S., Special Research Section of Applied Botany and Plant Assistant Pathology L. R. Tehon, Ph.D., Botanist C. Carter, Ph.D., Section of Insect Survey J. Assistant Botanist G. H. Boevve, M.S., Field Botanist H. H. Ross, Ph.D., Systematic Entomologist J. L. Forsberg, M.S., Research Pathologist Carl O. Mohr, Ph.D., Associate Entomolo- Bessie B. Henderson, M.S., Research Assist gist, Artist (on leave) ant B. D. Burks, Ph.D., Assistant Entomolo- gist (on leave) Section of Publications Milton W. Sanderson, Ph.D., Assistant James S. Ayars, B.S., Technical Editor Entomologist Eleanor G. Wolff, B.Ed., Assistant Ted Phyllis A. Beaver, Laboratory Assistant nical Editor

Technical Library Section of Forestry Marguerite Simmons, M.A., M.S., Techn James E. Davis, M.F., Extension Forester cat Librarian ^

Consultants in Herpetology: Howard K. Gloyd, Ph.D., Director of the Museum, Chicag Academy of Sciences; Clifford H. Pope, B.S., Curator of Amphibians and Reptiles, Chict Natural History Museum

•Deceased January 1, 1945.

This paper is a contribution from the Section of the Cooperative Wildlife Restoration Program and the Section of Forestry.

(84217—3M— 6-45) 1

CONTENTS Page Objectives of Project 449 Methods of Study 45O Acknowledgments 453 Populations 454 Distribution 454 Density 455 Species Ratios 455 Sex Ratios 458 Age Classes 45O Species Competition 453 Daily Activity 454 Seasonal Movements 465 Local Movements 466 Migration 466 Dispersal 467 Condition 467 Weight 467 Length. 470 Deformities 470 Wounds 470 Molt and Color 471 Parasites and Diseases 471 Predation 473 Breeding 473 Breeding Seasons 474 Mating Chase 481 Physiological Aspects 481 Testes 48 Cowper's Glands 482 Scrotum 482 Oestrus 483 Pregnancy 483 Gestation 484 Mammae 485 Young Rearing 486 Birth Dates 486 Birth Sites 487 Lactation 487 Development of Young 487 Litter Size 489 Illinois Habitats 490 Black Prairie Habitats 490 Woodland Habitats 492 River Bluffs and Bottoms 492 Wooded Upland 493 Miscellaneous Habitats 495 Foods and Feeding 496 Food Sources 497 Food Succession 503 Food Preferences 505 Storing and Feeding Habits 508 Minerals 510 Water 510 Nesting 51 Dens 51| Leaf Nests 5li

Hunting 516 Hunters and Hunting Methods 516 Kill 519

Management 520 Habitat Improvement 520 Forestry Practices 520

Hedgerows and Fencero n r- 521 Den Boxes 522 Control of Fire and Grazing 522 Winter Feeding 523 Hunting Seasons 524 Effect of Early Seasons 525 Recommended Seasons 526

Summary 529

Literature Cited 533

•St

participate in it, both" for its recreational Squirrel hunting is highly prized by those who Illinois hunters kill approximately 1,400,000 value and because it means "meat on the table." squirrels annually, of which about 70 per cent are fox squirrels. Fox Squirrels and Gray Squirrels

/// Illinois

LOUIS G. BROWN LEE E.YEAGER

SINCE the passing of big game in not fully applicable to Illinois conditions. Illinois, fox squirrels and gray A season similar to that in Ohio or Mich- squirrels have never ranked lower igan, considered sound, would retard the than second among game mammals of this opening date in Illinois 2 months or more; state in importance to hunters. First and Illinois hunters, to whom summer place is now a toss-up between these tree squirrel shooting is traditional, could be squirrels and cottontail rabbits, with the expected to oppose strongly and in good latter declining in public esteem because of faith such a restriction on their sport. recent epidemics of tularemia (Yeatter & For educational purposes as well as for Thompson 1943), a disease more com- administrative use, therefore, a fact-finding monly associated with rabbits than other study was needed in Illinois. game. The Federal Aid Project on which this Despite the long-standing importance report is based was proposed jointly by of squirrels, very little information has the Illinois Natural History Surve>- and been available upon which to base Illinois the Illinois Department of Conservation. hunting regulations, management and res- Formally known as "Squirrel-Raccoon toration measures relating to them. Laws Investigation and Management in Illinois, in regard to hunting seasons have been Project 14-R," the study was initiated on varied, and at times grossly unsound bi- July 1, 1940, and terminated as a project ologically. The most common problem on June 30, 1942, although some field pertaining to seasons is that of mid- or work, in connection with other projects,

late-summer hunting. Such hunting is was continued through 1944. Early in demanded by many hunters, particularly the investigation it was found that, despite in the southern part of the state. The the similarity in some squirrel and raccoon Illinois squirrel season for the biennium habitats, the two phases of the study could of 1939-41 opened, in this area, on July not be carried on adequately at one time

15. The date was set back to August 1 by one man ; only the seruor author was in 1941, but again advanced to July 15 available for field work during the greater in 1943. part of the investigation. Accordingly, These early opening dates, as would be the raccoon phase was dropped except for expected, resulted in numerous complaints observations that could be made inciden- from conservation organizations and from tally or as a part of regular squirrel studies. some sportsmen. Lawmakers and administrative personnel, in coping with the OBJECTIVES OF PROJECT situation, were greatly handicapped by the lack of specific information, despite recent The project had two main objectives, investigations in Ohio, Michigan and as follows: other states. In particular, information 1. Determination of squirrel breeding on squirrel breeding was scarce, and it seasons and related biology, the informa- was feared that such as was available was tion derived to be used in recommending

"llliiii.i- F(-i]er;il Aid Hiihllratlr.n No. 4. biologically sound squirrel hunting seasons. [4491 r ^

450 Illinois Natural History Survey Bulletin Fol. 23, Art. 5

2. Determination of the environmen- It appeared, therefore, advisable for the tal requirements of Illinois squirrels, the senior author to spend the first 10 days of information on this subject to be used in each month in the southern zone, the sec- management and restoration practices. ond 10 days in the central zone, and the last 10 days in the northern zone, collect- METHODS OF STUDY ing and studying during each period a sufficiently large number of fox and gray Illinois, with a north-south length of squirrels to determine seasonal differences 385 miles, is subject to greater seasonal in reproduction. Because such a plan, variations than any other midwest state. however sound theoretically, was expensive In the formulation and administration of in travel time, only the first year was fish and game laws, these variations are given to this periodical study by zones. partially compensated for through the During this time the zonal differences in division of the state into the northern, the seasons of reproductive activity were central and southern zones, fig. 1, each determined approximately. The second comprising about one-third of the state year was devoted to intensive field study and each representing a difference in sea- on representative central zone areas, on son of 6 or 7 days. which both fox and gray squirrels oc- The necessity for determining seasonal curred. variations in squirrel breeding and related In general, data on breeding and other phenomena in each of the three zones was seasonal phases of this study relate to recognized at the beginning of the project. the central zone, except where otherwise stated, and practical utilization of the information in the northern and southern zones necessitates appropriate allowance in

ILLINOIS time. Sample material yielding information on WMIieSlOE L t C squirrel biology consisted of freshly shot, KENOALL. "1 * --r^^— steel-trapped and live-trapped specimens. I BUREAU I Study of dead specimens was carried on mainly in several improvised field stations,

"««s"»i-i. L jj I although some material was examined in y^ t iKKo.p ^ ii r '

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I squirrels available I for r I ! were study every

CASS I BHOWN^' Pll T"^ MACON month for of project, al- I the duration the r 1- SANGAMON DOUOLAS . 1 T ( MORGAN I ^ \ J"^J^ Lj. though it was of course impossible to I K t. \sCOTT^ i^OULTfllEJ T" ^-1 =""""•' COLES n 1 ^ obtain equal numbers of squirrels each

' ^="ELB, ^ ^ol.BkJ month, either in species or sex. Fox squir- J "'"" _r\ MACOUPIN ' MONTGOMEft' rels far exceeded gray squirrels in number, -1^ amounting to about 70 per cent of the

"l ^->i total examined. C L A V - . -W- I mCHLANO [LAWRENCE/, I Each collecting method has its advan-

I 1 "•'"" 11}/, tages. Over much of the study period I JEFFERSON I guns and steel traps were employed simul-

I PERRYBE,,. ' RANDOLPH ) -j / , taneously. Hunting was most effective / FRANKLIN I ^ j during the main mast-feeding months, '""" IwilliamsonI saline oallatin;)- from mid or late August into October.

UNION IJOHNSONlp O P El Trapping was particularly successful during the winter and early spring, when corn was readily taken as bait. Traps were set, uncovered, on logs and Fig. 1.—Map of Illinois showing the three each was baited with a half ear of corn, zones on which the game and fish code of the usually impaled on a nail a few inches state is based. above the trap. Twenty-five to 50 traps September, 1945 Brown & Yeager: Squirrels in Illinois 451 were employed, and they were visited at breeding, pregnancy and lactation. Many least daily, and, as often as possible, twice squirrels were taken repeatedly. This daily. The most serious disadvantage of phase of the study supplied information this trapping method was that of taking on species ratio, sex ratio, population den- animals other than squirrels. These in- sity, movements and home range, in addi-

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Fig. 2.—Live trap, baited with shelled corn, in a tyjiical set location. Fifty live traps, used in three Pike County areas, yielded useful information on squirrel populations and life history. eluded skunks, foxes, raccoons, opossums, tion to breeding and related data. Vari- woodchucks, cottontail rabbits and a ous animals, including woodchucks, cotton- variety of birds. Since No. 1 traps were tail rabbits, skunks and opossums, and a used, practically all mammals caught ex- few birds, were captured in the live traps. cept squirrels and rabbits were uninjured These were unharmed and were released. and were released at the point of capture. The period of continuous trapping was Most birds caught in the traps were dead from October 16, 1941, to August 7, 1942. when found. Blue or red corn was found Prior to each of the two hunting seasons, to attract fewer birds than yellow corn, 1940 and 1941, covered by this project, but it appeared to be somewhat less at- copies of a questionnaire were distributed tractive to squirrels. thr(jughout the main squirrel hunting Live trapping, which was conducted in regions of the state. This questionnaire three wooded areas in Pike County, in- contained blanks to be filled by hunters volved both fox squirrels and gray squir- before the copies were returned to the rels. Shelled corn was used for bait. project leader. It was hoped that from Fifty live traps of the type described by the returned forms information pertaining Baumgartner (1940) were used, fig. 2. to kill, distribution, species ratio and Squirrels so taken were not killed, but population trends could be obtained. A were examined in the field for evidence of total of 3,300 forms were distributed 452 Illinois Natural History Survey Bulletin Vol. 23. Art. 5

during the 2 years, of which onlj' 236, or habits, activity, behavior, habitat require- 7 per cent, were returned. The writers ments and other matters of ecological in- consider that the most valuable informa- terest. tion yielded by the questionnaire pertained Unfortunately, no fully satisfactory to population trends and hunters' opinions technique has been developed for censusing of squirrel seasons. squirrels. That such a tool is important Data pertaining to breeding were ob- is obvious because the first information tained directly from examination of squir- needed in management relates to the rels of all age classes and of both species. number of animals present on each study Such information was recorded systemati- unit. This information is most useful cally under appropriate headings, as shown when it supplies numbers at a definite in fig. 3. For males, the information time; for example, population in the fall. particularly sought was size and weight In the absence of standardized methods

of testes and size of Cowper's glands ; for for determining squirrel numbers, it be- females, evidence of oestrus, pregnancy, comes necessary to make the best estimates lactation and placental scars. The age possible. These estimates are generally of all specimens was determined with as made by rules-of-thumb, or by using one much accuracy as possible, and, throughout or more of the various techniques that

the study, special efforts were made to have been described. The result is often develop aging criteria. Weights and expressed in reference to the population general measurements were taken of nearly by such terms as "plentiful," "common," all specimens. Other records related to "scarce," or "heavy," "medium," "light." locality and date of collection, condition Dice (1931) proposed, as the best of pelage, parasites, disease and stomach method of determining mammal abun- contents. Supplementing these data were dance, the listing of individuals observed in detailed observations on foods and feeding each ecological unit of the habitat. This September, 1945 Brown & Yeager: Squirrels in Illinois 453 method gives more properly an index of of the nest-count method. The hunting- relative abundance in the various units with-dog method was not tried. It is rather than a true census. Later, Dice probably significant that Goodrum refers " (1941) summarized various census tech- to these census techniques as . . . methods niques, some of which were applicable found most effective in estimating gray directly or indirectly to squirrels. Leo- squirrel populations in eastern Texas." pold (1933) discussed census methods for Chapman (1937, 1938«) in Ohio, and both game birds and mammals. Like others, have used data taken directly from Dice, he suggested techniques that could hunters as a means of determining trends be used in squirrel census. in populations. This is a rapid and use- Goodrum (1940) developed three cen- ful method, and, if based on many samples, sus techniques for gray squirrels in Texas, may indicate trends for large areas, even which probably would be equally appli- for a state as a whole. However, most cable to fox squirrels. These methods kill data are subject to too many variations were as follows: to yield more than very general informa- 1. Time-area counts, using number of tion, thus limiting materiallv their use. squirrels observed during definite time Baumgartner (1940), Allen (1942, period on random plots of known size in 1943) and the present writers determined, each ecological type. by exhaustive live trapping, and with a 2. Nest counts in each ecological type, relatively high degree of accuracy, squirrel multiplied by a factor of two. numbers on small study areas. This tech-

3. Hunting with dog, using number of nique, however, is too time consuming for squirrels treed per hour. practical, large scale censuses. Estimates The first method is based on the average of the population made by less exacting distance a squirrel can be seen, and thus means, if based on experience and judg- the size of the territory that may be ob- ment, serve many purposes of manage- served from a stationary position. Good- ment; and, if made uniformly year after rum, using three-fourths of this territory year, may indicate population trends satis- as the unit that could be watched effec- factorily. Some experienced hunters de- tively, calculated populations in each ec- velop almost uncanny accuracy in judging ological type by multiplying the average squirrel numbers on areas with which they number of squirrels seen per acre on each are familiar. observation territory by the number of acres in the type represented. The second ACKNOWLEDGMENTS method involved counting all twig and leaf nests, preferably in the fall and win- For aid in various aspects of this in- ter, in each ecological type and multiplying vestigation the writers are indebted to the by two. The third method, employed following organizations and individuals. only when squirrels were active on the Illinois Natural History Survey: ground, gave the number of animals treed Dr. T. H. Frison, Chief, for general

per hour in each ecological type. In each supervision ; Dr. George W. Bennett, of these methods, the greater the number Limnologist, for several photographs and of counts and the more uniform the vege- for aid in collecting; Dr. Carl O. Mohr, tational types, the more nearly accurate Associate Entomologist, for suggestions in is the census. regard to field work; Dr. H. H. Ross, It should be noted that Goodrum's first Systematic Entomologist, for identification two methods result, theoretically at least, of external parasites; Dr. D. H. Thomp-

in a true census ; the third, unless several son, Zoologist, for assistance with statisti- factors not given are known, could not be cal analysis; Mr. Frank C. Bellrose, Jr., more than an index of relative abundance. and Dr. Ralph E. Yeatter, for numerous The present writers made limited use of records and suggestions; and Mr. James the time-area method and were convinced S. Ayars, Technical Editor, for several of its possibilities provided the investigator photographs and for assistance in the had time for making a large number of choice of illustrative material. counts. In agreement with Allen (1942, Illinois Department of Conserva-

1943), who worked with fox squirrels in tion : Hon. Livingston E. Osborne, Di- Michigan, we are uncertain of the value of rector, and Mr. Anton J. Tomasek, State :;

454 Illinois Natural History Survey Bulletin Vol. 23. Art. 5

Forester, for fiscal administration and Hatfield (1941) as occurring in Illinois. many courtesies; Mr. Louis E. Martin, The fox squirrel has statewide distribu-

Superintendent of Game Restoration, for tion ; records for the northern gray squir- assistance with special problems; Mr. rel include counties in approximately the Robert C. Sparks, Chief Inspector, and northern two-thirds of the state and for numerous conservation officers for aid in the southern gray squirrel several of the collecting study material and in distrib- southernmost counties, fig. 4. Both sub- uting questionnaires. species of gray squirrels undoubtedly ex- University of Illinois: Dr. L. J. tend beyond the range given. Thomas, Associate Professor of Zoology, The red squirrel, Tamiasciurus hudson- identified all internal parasites; Dr. B. icus loquax Bangs, is listed by Necker & V. Hall, Assistant Professor of Zoology, Hatfield as still being present in the wild gave information concerning the physical in Illinois, but no observations or other of it characteristics of breeding in rodents ; and records were obtained during the Dr. Robert Graham, Head, Department present study. If red squirrels occur here, of Animal Pathology, cooperated in the it is believed that they do so only in re- study of a number of diseased squirrels. duced numbers and in quite restricted lo- Gun Clubs AND Landowners: The calities. Kennicott (1857) gives a good following gun clubs extended to the senior account of their early abundance in the writer many courtesies and provided a northern parts of the state. large number of squirrels for examination Fox squirrels are found on farm and East St. Louis Gun Club, Wolf Lake; forested areas, and in cities and villages. Gilead Gun Club, Hardin; and Red's Outside of some urban communities, gray Landing Gun Club, Hardin. The fol- squirrels are restricted to heavily wooded lowing landowners are among those who areas, generally those having abundant gave access to their property and assisted ground cover and brushy understory. with certain phases of the study; Mr. Samuel Wade, Mr. Wayne Harshman and Mr. Frank Birch, all of Griggsville Mr. Robert Allerton, through Mr. Elmer Priebe, Monticello; Mr. Charles Price, Charleston. To many others, not named, the authors express their appreciation. POPULATIONS

During the second year of the investigation, considerable time was given to study of squirrel populations on representative areas in Pike County, in the central zone. From data gathered there, from questionnaires returned by hunters and from kill records supplied by the Illinois Department of Conservation, detailed information on squirrel distribution, kill, sex ratios, species ratios and related subjects was obtained and added to the more general information gathered in the first year. FOX SQUIRREL

Distribution ^ CRAY SQUIRREL

The western fox squirrel, Sciurus Jiiger rufiventer (Geoffroy), the northern gray squirrel, S. carolinensis leucotis (Gapper), and the southern gray squirrel, S. c. car- Fig, 4.— Distribution of fox squirrels an^ oliiiensis Gmelin, are listed by Necker & gray squirrels in Illinois. September, 1945 Brown & Yeager: Squirrels in Illinois 455

Woodland of this type is found in Illinois known that fox squirrels frequented this

principally along the main river valleys site. 1 he figure of 1.49 individuals per

and in the southern and southwestern parts acre for the Wade area, table 1, probably of the state, Hg. 4. Further discussion represents for gray squirrels the upper of the preferences of the two species are density limit found on the better Illinois given under "Illinois Habitats." range. The figure of 2.23 fox squirrels per acre Density for the Harshman area represents the density on a small, very favorable area.

During this study squirrel population A density of half this figure is considered density vv^as determined with a high degree as probably representative for large areas, of accuracy on only one area. This area, even of the better habitats. however, was typical of the large region No evidence was obtained to show con- of good squirrel habitat in southern and clusively that either fox or gray squirrels southw^estern Illinois, where both squirrel are cyclic in Illinois. Fluctuations in species often occur in mixed populations. populations from year to year, as long ob- On three other areas, all representative of served by hunters and reflected in kill extensive Illinois habitat types, rough es- records, suggest that these squirrels may timates of the population were obtained. be cyclic, although the degrees of fluctu- Population estimates of the four areas are ation are only minor. If squirrel cycles presented in table 1 and are discussed operate at all in Illinois, they show little below. of the spectacular nature common in hares Great differences in population density and other species in northern regions. were found in Illinois fox squirrel habitats. Edminster (1937), at least by implication,

Comparable data are not available for the suggested that the gray squirrel is cyclic gray squirrel. This species, however, is in the New England region. known to occur in varying densities, although not in the extremes found in the Species Ratios fox squirrel. The lack of extremes is due probably to relative uniformity in the From data presented in tables 2 and 3, habitat occupied by gray squirrels, which, and from general observations throughout as stated previously, is mainly heavily the state, it is evident that the fox squirrel wooded areas. The populations given per is more abundant than the gray squirrel in acre for the Harshman and Urbana Town- Illinois. ship areas, table 1, probably represent the All of the squirrels listed in table 3 highest and lowest densities for fox squir- and 86 per cent of the 4,597 animals in- rel habitats likely to be encountered in cluded in table 2 were obtained by hunt- the state. On the Mason County area, ing. Because of tw^o differentials associ- which is of the black oak type, composed ated with hunting, the relative abundance of all ages and degrees of stocking, it was of fox squirrels may be actually somewhat found that fox squirrels may occur in lower than the figures indicate. First, varying densities in the same general habi- fox squirrels may be easier to kill than tat. The censused populations in 16 black gray squirrels; they are so considered by oak stands in this area ranged from 0.02 many hunters, although the writers found to 2.20 squirrels per acre. little difference between the species in this

Although many areas were found where respect. Second, there is a small differ- both species were present, as well as many ence in the accessibility of habitat pre- areas carrying only fox squirrels, none ferred by the two species, that for the gray were encountered that held gray squirrels squirrel being, in general, the more re- alone over a relatively large tract. Local mote and the more difficult and time con- concentrations of gray squirrels were often suming for hunters to reach. seen. The junior author counted 16 of On areas harboring presumably typical these animals late in the afternoon of populations of fox and gray squirrels, both October 16, 1942, on an area of less than steel trapping and live trapping showed a 3 acres. All were foraging in an oak- preponderance of fox squirrels in the hickory stand that bordered a young river- catch, table 2 ; in live trapping the differ- bottom forest in Coles County. It Avas ence was small. In view of the first I

456 Illinois Natural History Survey Bulletin Vol. 23. Art. 5

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Table 2.—Species ratio in Illinois squirrels as determined from 4,597 animals, some of them shot by hunters and others collected by the writers, 1940, 1941 and 1942.

1 low Taki.n 458 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

Sex Ratios gray squirrels the numbers were nearly equal for the sexes. Litter counts, on the The sex of 4,651 squirrels, 3,197 fox basis of a very few samples, showed slight- squirrels and 1,454 gray squirrels, as de- ly more males than females in both species. termined during the investigation is A summary of figures listed in table 4 shown in table 4. These data were de- showed a preponderance of males in both rived largel_v from hunters' questionnaires, species, giving a male to female ratio of and were therefore subject to whatever roughly 60 to 40. differentials there may have been in bag- The sex ratio of 17 litters of fox squir- ging the sexes. rels, totaling 43 young, recorded during It appears that Illinois squirrel popula- the spring of 1941 was 105 males to 100 tions either have a preponderance of males, females, table 4. Of 179 first-season or or that males are more easily bagged by spring juvenile fox squirrels taken by the hunters, who invariably shoot at squirrels writers and by hunters from May through in the order of their appearance until the November 15, 62 per cent were males and limit is reached or the hunt is over. Fox 38 per cent were females; of 109 second- squirrel males and females were taken in season or summer juveniles taken during steel traps in approximately the ratios in September and October, 57 per cent were they shot gray squirrel males males and 43 per cent were females. The which were ; and females were steel trapped in more sex ratio of all juvenile fox squirrels for nearly equal numbers, but with males pre- which records were obtained, including lit- dominating, table 4. Live trapping, for ters, 195 males and 136 females, was 144 which the samples are too small for re- to 100. liability, yielded in both fox and gray In gray squirrels, the sex ratio of 3 squirrels more females than males, but in litters, totaling 11 young, was 120 males

Table 4.—Sex ratio in Illinois squirrels as determined from sample litter counts and from animals shot, steel-trapped and live-trapped, 1940-1943.

How Taken —

September, 1945 Brown & Yeager: Squirrels in Illinois 459 to 100 females, table 4. Of 60 spring October, 58 per cent were males and 42 juveniles taken hy the writers and b}' per cent were females. The sex ratio hunters, 55 per cent were males and 45 of all juvenile gray squirrels for which per cent were females; of 38 summer records were obtained, 61 males and 48 juveniles collected in late September and females, was 127 males to 100 females.

Fig. 5. Juvenile (left) and adult male fox squirrels. Note smoothed, blackened appearance of scrotum in adult and the smaller, less conspicuous scrotum in juvenile. Piatt County, late January, 1944. Gray squirrels of the same ages show the same characteristics. 460 Illinois Natural History Survey Bulletin Vol. 23. Art. 5

The actual sex ratio of Illinois squirrels to writers) placed some value on compar- may be more nearly equal in both species ative growth stages, skin texture, and de- than shown in table 4. It seems that velopment of pigment and hair on various males, because of somewhat more active parts of the body, particularly on the scro- habits, offered hunters more opportunities tal sac of the males and on the ventral

Fig. 6.—Juvenile (left) and adult female fox squirrels, Mason County, August 15, 1944. Juvenile was first-season j-oung; adult had weaned a first-season litter, but was neither pregnant nor lactating. Note the inconspicuousness of the mammary glands of the juvenile, and the prominent, blackened nipples of the adult.

for shots than did females, and probably region of females. Chapman (1938(7, b) for the same reason proportionately more working with gray squirrels, found a cor- males were taken in steel traps. relation of age and weight classes. In both species males were the more Age Classes difficult of the sexes to age. Juvenile males born in late winter or early spring No simple, yet infallible, method of de- were easily confused wnth adult males by

termining age classes in fox and gray the October and November following ; and squirrels has been reported. Such tech- by December, when weights and measure- niques are much needed, not only for squir- ments of the two groups were approxi- rels but for many other animal groups. mately equal, they could scarcely be differ- The nearest approach to a workable entiated. In adult males the scrotal sac

method for aging squirrels requires the is more pendent, and is blackened and less use of a number of criteria introduced by nearly clothed by hair on the ventral sur- several workers, and validity of the method face, fig. 5. In December, appearance of is somewhat conditioned by the experience the teeth, and of hair and skin on the soles

of the user. For fox squirrels, Allen of the feet, is very similar in the two age (1942, 1943) and Baumgartner (in letter groups. Some juvenile males born in the

I September, 1945 Brown & Yeager: Squirrels in Illinois 461 summer remain distinguishable from adult applicable to all individuals of a given males until about May of the following species or sex, and in some individuals age jear. could not be determined with complete In females, the teats offer the best means satisfaction when all criteria were used. of determining age classes. In individuals Hunters distinguish young from adult that have never bred, these structures are squirrels by several criteria other than ap- small, light in color, and with the entire pearance. The skinning test is perhaps gland more or less hidden in the growth most common, young squirrels being "easy" of hair. Mature females, after breeding to skin and old squirrels "tough." Young and nursing, have much larger and more squirrels remain "easy" to skin well into conspicuous mammary glands, the nipples the fall or into the following spring, ac- of which, in both species, are dark in color, cording to time of birth. The ease with fig- 6- which the leg bones may be snapped when . . The criteria found useful in aging the animals are being dressed is another squirrels in this study are listed in table criterion sometimes used by hunters. 5. Collectively, and when used by an Squirrels may properly be classed as experienced observer, they are believed to adults after they reach breeding condition, be reliable for most individuals of both and on this basis first-season young, born species. No single criterion w'as found in late winter or early spring, become

Table 5.—Criteria for distinguishing between adult and Juvenile fox and gray squirrels.

Adults Juveniles

Males

1. 462 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

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Table 7.—Age classes of squirrels shot or steel-trapped by the writers in Illinois during the hunting seasons of 1940 and 1941. 464 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 squirrels and gray squirrels. The occur- the afternoon. In the forenoon, the hour rence of one or both species on a given area between 6 and 7 o'clock, when an hourly appeared to be due more to characteristics average of 0.89 fox squirrel and 0.77 gray of the habitat than to interspecific compe- squirrel was seen, showed the highest ac- tition or lack of it. Only two or three tivity figure for both species, table 8. The observations of belligerency, and none of next highest activity hour in the forenoon actual fighting between the two species, was 7 to 8 o'clock for fox squirrels and 5 were obtained, while, on the other hand, to 6 o'clock for gray squirrels. The both were frequently observed feeding in greatest afternoon activity was between 4 the same area and sometimes in the same and 5 o'clock for fox squirrels and between tree. Throughout the Illinois gray squir- 5 and 6 o'clock for gray squirrels. Gray rel range, hunters often kill both species squirrels were active both earlier and later on the same grounds. In one Pike County in the day than fox squirrels, but fox squir- area, live trapping revealed a squirrel pop- rels were definitely more active during ulation composed of 64 per cent gray midday hours. squirrels and 36 per cent fox squirrels. The data in table 8 are not in accord Only fox squirrels inhabited an open, oak- with the observations of Hicks (1942), hickory area a few miles away that was who found that the peak of activity in

similarly trapped. Both species were col- Iowa fox squirrels occurred between 8 : 00

lected with gun or steel trap on at least and 10 : 00 A. M., and that the next highest

50 areas throughout the state during the peak was between 1 : 00 and 2 : 00 p. m. period 1940-1943. Hicks made only a limited number of ob-

That some competition exists between servations before 8 : 00 a. m. and after

the two species for available food and 5 : 00 p. M. Most other writers discussing

cover is probable, but it seems equally this subject have indicated early morning probable that little if any more compe- and late afternoon activity peaks. tition results from the presence of two The daily activity of both species was species than from the presence of an equal observed to reach the annual zenith during number of individuals of the same species. the mast season. At this time, storing ap- The best evidence of interspecific compe- peared to be the main pursuit other than tition at hand is that usually only one feeding, and in individual squirrels in- species occurs in a given urban community. volved several hours per day. Gray squir- Seldom were both species found in any one rels were observed to be abroad during municipality. We observed that about as midday hours more during the mast season many urban populations consisted of gray than at any other time of the year except squirrels as of fox squirrels, although the at the height of mating in December anc habitat afforded by parks and tree-bor- January. During the mast season, as at

dered streets is obviously better suited to other times, there was more activity ir the latter. both species during early morning anc late afternoon hours than at midday. DAILY ACTIVITY Although the effect of various weathei conditions on squirrel behavior was no Throughout the first 2 years of this in- studied in detail, both species were founc vestigation, squirrels were hunted at least to be active all year, but least so during weekly and often daily for the purpose of unusually cold weather. In hundreds oi obtaining study specimens. The record observations made in winter examination; kept of all hunts included the time of hunt of wood duck boxes, it was noted that in^ (Central Standard), and the place and dividuals of both species were somewhat activity of each animal when seen. A to- sluggish and more or less reluctant to leave tal of 716 hours, 387 in the morning and nest boxes when the temperature was be- 329 in the afternoon, were devoted to low freezing. A total of 680 boxes hunting. Of the 554 squirrels observed, yielded 55 squirrels, 48 of which were fox

336 were fox squirrels and 218 were gray squirrels ; 32 of the fox squirrels showed squirrels. These data are summarized in noticeable reluctance to leave their nestS; table 8. Many of these individuals, which re- Activity in both species of squirrels was mained in the boxes after the lids were decidedly greater in the morning than in removed, were observed to be sleeping, September, 1945 Brown & Yeager: Squirrki.s in Illinois 465

Table 8.—Activity in Illinois squirrels based on 716 hours of hunting in which 336 fox squirrels and 218 gray squirrels were observed, June 1—October 31, 1941 and 1942. Hours specified are for Central Standard Time.

Species ;

466 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 a well-defined direction; and "Dispersal," resident population covered only about 150 which deals with the phenomenon of acres. spread or "shuffle" in squirrel populations, During the young-rearing period par- especially in the fall prior to the breeding ticularly, females seemed to confine their season. movements to the vicinity of their brood sites, which numbered from one to several. Local Movements In both species local movements were most extensive during the fall. Both fox and gray squirrels are usually When not disturbed by overhunting, considered sedentary species, although the fire, drought or lumbering, individual latter, according to some authors, are squirrels may spend an entire year or more subject to irregular migrations, discussed in the vicinity of a given nest tree. Allen below. As has been reported by Seton ( 1942) reported an example of a Michigan (1928), Baumgartner (1938, 1943^0, fox squirrel female that used a red maple Goodrum (1940) and Allen (1942, as headquarters continuously from Oc- 1943), local movements in both species of tober, 1937, at least until observations squirrels appear to be caused mainly by were terminated in December, 1939. food conditions. In the course of a year, Seton (1928) stated that a gray squirrel fox squirrels, apparently in foraging, may may live its entire life on a 100-acre plot. cross woodland or open fields for a dis- Goodrum (1940) considered the home tance of 2 or 3 miles. Gray squirrels, range of this species to be 200 yards or where favored by continuity of forest less, but he believed that some individuals cover, may travel equal if not greater dis- may cover 4 or 5 miles during the course tances. The homing instinct of this spe- of a year. Middleton (1930) intimated cies was studied by Hungerford & Wilder that gray squirrels in Great Britain seldom (1941), who reported returns in 6 of 15 travel more than 100 yards from head- animals, the greatest distance being 2.8 quarters, but also stated that the species miles during a period of 4 weeks. extended its range 35 miles in 5 years. Squirrels shift readily from one local food area to another. On the Chautau- Migration qua National Wildlife Refuge, fox squirrels deserted one area after another as No evidence of migration in fox squirrels specific foods in other areas became avail- was observed in this study. Baumgartner able. They frequented the elm lowlands (1938) writes: "General and regular mi- from late February into July, when elm gration of the fox squirrel is unknown." buds and seeds, and later mulberries, sup- Allen (1943) states: "Fox squirrels have plied staple foods; they raided adjacent seldom been observed in mass movements cornfields from midsummer until fall similar to those of the gray, which was and they used upland oak-hickory areas as known in early daj's as the 'migratory main foraging grounds during the fall and squirrel.' " There are numerous reports winter. These shifts, however, at no time of mass movements or migrations of gray involved travels of more than a few squirrels covering considerable distances; hundred yards, and in no sense did they in these movements the animals were not take on the usual characteristics of mi- deterred even by the formidable Avidths of gration. the Hudson, Ohio or Mississippi rivers. In one wooded area on the Chautauqua Seton (1928) associated this phenomenon Refuge containing mature oaks, pecans with food shortage, overpopulation and and hickories, in addition to elms, maples cyclic influences. Chapman (1936) at- and other riverbottom species, seasonal tributed it mainly to the first two reasons. shifts in the squirrel population (all fox Jackson (1910, 1921) cited two instances squirrels) were much less distinct than in which numbers of the gray squirrel, in those mentioned in the foregoing para- one case possibly because of a food short- graph. Indeed, day-to-day travel here age, swam the Mississippi River from Wis- seemed to be confined to a small area, consin to enter Minnesota. Goodwin usually not more than a few acres, and (1934) reported an extensive migration often the vicinity of one or a small group in the New England states in 1931 of food trees. The annual range of the and 1933. Osgood (1938) reported a.

i September, 1945 Brown & Yeager: Squirrels in Illinois 467 gray squirrel migration of small propor- 1942. Ihis individual was trapped on tions in Vermont in 1935. According to August 5, and it is likely that the squirrel the reports of numerous authors, the mi- had only recently moved onto the area grations covering the most territory, as from a woodland to the east. On August well as involving the most individuals, oc- 8, 1942, the writers shot two fox squirrels curred before the twentieth century. (Nos. 11 and 26) and seven gray squirrels (Nos. 1, 5, 9, 13, 26, Zi and 50) on the Dispersal Wade area. No unmarked animals were among these squirrels. In the period Oc- According to Baumgartner (1940), the tober 15 through 17 the senior writer shot most extensive and important movement in 13 additional specimens, 5 fox squirrels fox squirrels "is the traveling associated and 8 gray squirrels, of which 1 fox and 2 with the annual readjustment of popula- gray individuals were unmarked. They tions. This dispersal movement occurs were 1942 spring juveniles, and therefore between August 10 and September 15. subject to trapping and marking had they J'he distances traveled at this time average been present during the last 8 to 10 weeks about two or three miles, although two of trapping. It is believed that these long records of 14 and 8 miles respectivel\ three animals had moved onto the area were secured. This movement is respon- during the period of August 8 through sible for the annual restocking of over- October 17. Other than these three hunted areas." spring juveniles, six unmarked 1942 Allen (1943) indicates that a popula- summer juveniles (one fox, live gray) tion shuffle occurs in Michigan fox squir- were collected in mid October, 1942, but rels. He states (1943) that "... it these may have been young born on the appears that increased activity among area and too small to be taken in live traps squirrels begins in late August, rises to a prior to August 8. peak in late September, and is over by the middle of December." CONDITION Of the reasons for dispersal Baumgart- ner (1943rt) writes: "The cause of this Weight and length measurements w^ere movement is controversial. The motivat- taken of most squirrels collected, and in- ing factor is usually considered to be formation on diseases, parasites, deformi- population pressure correlated with a ties and pelage development was recorded shortage of food, yet it occurs when the when observed in the specimens. food supply is greatest, almost simultaneously with the maturing of the nut Weight crop. The moving squirrels are more noticeable when the population is high, Weights were obtained for a total of and the writer believes the movement re- 706 fox squirrels and 317 gray squirrels. sults from intra-species intolerance. This The data are given in table 9. In adults, view is partially substantiated by the fact weights were recorded by sex, but in that no record of excessive fox squirrel juveniles the weights of the two sexes populations, either in the literature or in were lumped. the field, could be authenticated. Seven As indicated in table 9, there were no such reports were investigated but none significant differences in weight between showed more than two squirrels per acre." male and female adults in either species. Our evidence indicates that in Illinois a Allen (1942, 1943) found female fox dispersal occurs in both fox and gray squir- squirrels in Michigan to be slightly larger rels during the fall. Continuous and in- than males. A point of interest in the tensive live trapping on the Wade area present stud>' is that of size in juveniles over a 10-month period prior to August at the time the\ began to enter hunters'

8, 1942, resulted in the capture and mark- bags in July. Spring juvenile fox and

ing of most if not all resident squirrels, gray squirrels at that time had an average since only one unmarked animal, a 1941 weight of 1.28 pounds and 0.84 pound, summer juvenile (female), was taken respectively. By late October or Novem- either by trapping or hunting during the ber, the spring juveniles of both species period between July 12 and October 15, had reached approximately average adult I

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weight, representing gains in weight of known to hunters, who commonly attrib- about ZZ or more per cent since July. ute it to fighting between males and the Development of summer or second-litter mating chase between males and females. juveniles approximated that of spring or We have no more logical explanation. In first-litter young in both species, and, as no case was the deformity observed to im- would be expected, summer-born animals pede travel or any other activity. taken the following September and Oc- tober showed the lowest average weight Wounds of any age class in the kill at that time. Six crippled squirrels, four fox and two Length gray, were collected by the writers.

Body and total lengths of 706 fox squirrels and 317 gray squirrels were recorded, table 10. All readings were taken in a standard manner (Anderson 1932). Length of the hind foot was taken for a large series, but the differences appeared so insignificant that taking of this measurement was discontinued. Spring juveniles were first collected in May, at which time the average body length and total length in the fox squirrels were 231 millimeters and 461 millimeters, respectively, and, in the gray squirrels, 205 millimeters and 389 millimeters, respectively, table 10. By mid fall these measurements had increased, respectively, about 17 and 13 per cent in fox squirrels, and about 27 and 21 per cent in gray squirrels. The apparently greater rate of increase in gray squirrels may be ac- counted for by the 2-week difference in the average breeding dates of the two species, and, consequently, in the propor- tionally 3-ounger age of gray squirrels collected in May. Summer juvenile fox squirrels, first collected in August, had an average body length of 236 millimeters at the time, and 267 millimeters in December. Summer juvenile gray squirrels were first collected in September. At that time their average body length was 209 millimeters. In December it was 245 millimeters.

Deformities

Only one type of deformity, that of stub tail, was noted in 706 fox squirrels and 317 gray squirrels handled by the writers. Ninety-five, or 13.5 per cent of all fox Fig- 7. Crippled female squirrels, and 39, or 12.3 per cent of all — fox squirrel collected in Piatt County, February, 1945. The gray squirrels, showed this defect to a injufy was probably caused by a steel trap or greater or less degree. This incidence of a .22 caliber bullet. Despite the injury and stub tail in the two species is considered a case of mange, this female was pregnant surprisingly high. The deformity is well and in good condition as to body fat. September, 1945 Brown & Yeager: Squirrels in Illinois 471

These numbers represented little more anistic individuals were taken. However, than one-half of 1 per cent of the total albino gray squirrels occur in considerable number of animals collected, but they numbers in Olney, where they are said to gave, of course, no true index of crippling have increased from an albino pair re- loss, which hunters' questionnaires indi- leased some years ago. Melanistic squir- cate are much higher, table 23. Animals rels have been reported from Ogle County showing imbedded shot but healed wounds, and other northern Illinois localities. In or missing toes probably due to shooting, an early report, Kennicott (1857) stated were not counted among the cripples. In that of 50 gra>- squirrels killed near Rock- tw^o cases, one in each species, bones of a ford, Illinois, all were black. During the hind leg were so badly shattered that re- pioneer period, black squirrels were com- covery was improbable. Some seriously mon in Michigan (Allen 1943), Indiana wounded squirrels undoubtedly make their (Haymond 1869, Hahn 1909) and in way to cavities or nests, from which they other states. One adult male gray squir- probably never emerge. In all except one rel trapped in Pike County, February 25, case, shotgun pellets were the cause of the 1941, had reddish thoracic hair and black crippled condition observed. A fox squir- abdominal hair. A juvenile male fox rel that recovered from a severe wound is squirrel with blue eyes was trapped in sliown in fig. 7. Pike County, February 8, 1942. Baum- gartner (1943/*) reported nine different Molt and Color color patterns in Ohio fox squirrels, including melanistic, near albino, brown- Fox and gray squirrels molt once a tail, and variations of black and red or year, the two species having similar molt- rufus. ing characteristics. The molt consists of two phases, the first involving the body PARASITES AND DISEASES and the second the tail. Males molt before females, beginning in the spring and Several papers dealing with the para- concluding the process during the summer. sites of squirrels, particularly fox squirrels, Females appear to molt at any time be- have been published. Katz (1939) tween April and September, after their brought most of this information together. last young of the year have been born. Harkema (1936) studied the parasites of Adult males and spring juveniles ordi- 53 gray squirrels in North Carolina, find- narily molt before adult females, especially ing one species of tapeworm, one of round those producing second-season or summer worm, three of mites, two of lice and one litters. These adult females usually com- of flea. Chandler (1942) recently re- plete the molt in September. ported on the helminth worms of tree

Molting in both fox and gray squirrels squirrels in southeast Texas ; and Graham requires 3 to 4 weeks. Progress in the & Uhrich (1943) published on the ex- body phase is from nose to tail ; on the ternal and internal parasites of the fox tail, molting begins at the distal end and squirrel in southeastern Kansas. Baum- progresses anteriorly to the base of the gartner (1940) and Allen (1942, 1943) tail. In most individuals there is a defi- discussed briefly the parasites and diseases nite line of demarkation between the new of fox squirrels in Ohio and Michigan, and old hair. When such a line is not respectively-; and Goodrum (1940) represent in molting animals, new hair is ported similarly for gray squirrels in being replaced over a relatively wide area, Texas. The most prevalent parasites re- the old and new hair tending to blend. ported by all these authors were mange Few of the colf)r patterns ordinarily mites. No diseases of endemic nature found in squirrels were encountered in other than mange were reported. Illinois during the course of this study. Most squirrels studied during 2 years One very reddish female fox squirrel w-as of field work in this investigation were shot that may have been an example of examined for mange, and for ticks and erythrism. This was a mature animal, other external parasites. The same spe- taken on August 7, 1942, while "cutting" cies of parasites were found to occur on a hickon,' nut. She was host to a very both fox and gray squirrels. Mange large ascarid. No distinct albino or mel- (caused by Sarcoptcs sp.) occurred to a 472 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 noticeable degree in only 0.03 per cent of Fleas (Siphonaptera) the 722 fox squirrels and 0.06 per cent of Orchopeas ho^vardii (Baker). Very the 353 gray squirrels examined for this — common and frequently extremely abundant. This condition. Incidence of mange in all species has been found in great numbers in squirrels studied was 0.04 per cent. All overwintering nests throughout Illinois. zones were represented by the animals Orchopeas nepos Rothschild.—Taken only examined for parasites. rarely in Illinois. The degree of infestation was negligible in most woodland populations, but in some Sucking Lice (Anoplura) urban populations of both species a heavier rate prevailed. Woodland squirrels show- Hoplopleura sciuricola Ferris. —Taken only ing evidence of mange were found on only rarely in Illinois. two localized areas, one the pin oak bot- to undoubt- toms near Thomson in Carroll County, In addition the above, chiggers edly occur on Illinois squirrels. Although we involving only fox squirrels, and the other have no definite records for this state, Roger near Griggsville in Pike County, involving Williams, while at the University of North both fox and gray squirrels. The first Carolina, found chiggers on squirrels. These infestation of per cent area showed an 47 chiggers belong to the mite genus Trombicula in a sample of 15 squirrels; the latter, 15 and allied genera. per cent in a sample of 94. The degree of infestation in Pike County was about In a small number of squirrels studied the same in the two species. In both for internal parasites, one-third of the localities squirrels were collected during animals contained parasitic worms. Iden- the breeding seasons, and in both infested tification of these specimens was made by | individuals were apparently normally ac- Dr. Lyell J. Thomas of the University of tive. A female shot February 26, 1941, Illinois. The following remarks are on the Thomson area had bare patches of quoted from his report. skin on head, neck and back, yet contained three well-developed embryos. Another No. 1. —Female fox squirrel, Thomson, Illi- collected on February 17, 1945, near Mon- nois, collected May 27, 1941: Eight cestode ticello, Piatt County, had the left hind cysts in visceral cavity, identified as Taenia foot missing and was practically devoid pisiformis. These generally occur in rabbits. No. 2. Female fox squirrel, Griggsville, of hair, due to mange, on the neck and — Illinois, collected April 19, 1942: Several nem- thoracic regions, but this animal, fig. 7, atodes from intestine ; all females, and identi- likewise contained three normal embryos. fied as Impalaia sp., probably new. None of the infested squirrels were in poor No. 3. —Female fox squirrel, Griggsville, physical condition. Illinois, collected August 7, 1942: One large Practically every squirrel, fox and gray, male nematode from large intestine identified was host to fleas ; many animals carried as Ascaris sp. (probably A. lumbricoides). Has been recorded from Indian squirrels, the common dog tick ; less than 1 per cent East carried sucking lice. Dr. H. H. Ross of but not, to my knowledge, from North Ameri- can squirrels. Normal hosts are and the Illinois Natural History Survey sup- man pig. Closely allied species occur in skunks plied the following notes on ectoparasites. and armadillos. No. 4.—Female gray squirrel, Griggsville, The same species of ectoparasites occur on Illinois, collected April 21, 1942: Three male both the gray and fox squirrels in Illinois. and five female nematodes from intestinal tract identified as Impalaia sp., probably new. Two Ticks (Ixodoidea) female nematodes from intestinal tract identified as Mescistocirrcus sp., probably new. Dermacentor 'variabilis (Say). —Taken very commonly on squirrels throughout Illinois. The four squirrels yielding the above This is the common dog tick and occurs on many other mammals. endoparasites appeared to be in normal vigor, although none contained noticeable Parasitic Mites (Parasitoidea) fat in the body cavity. The female that was host to the ascarid was reddish to the Several species of this superfamily of mites point of erythrism. The uterus showed have been encountered on Illinois squirrels. five placental scars and the mammae con- September, 1945 Brown & Yeager: Squirrels in Illinois 473

tained milk. This squirrel weighed 1.59 climbed back to the box with difficulty. pounds, was 544 millimeters in total Two months later another inspection re- length, and had about half completed the vealed that he had died in the box. No molt. sign of gunshot or other injury could be A female fox squirrel, too weak to found. escape, was captured alive near Urbana, A northern Illinois coon hunter reported Illinois, on April II, I94I. Diagnosis in one instance of weasel predation on fox the Animal Pathology Laboratory of the squirrels. This attack was at night. The University of Illinois revealed a fractured hunter first heard a squirrel in a tree, then tibia and the presence of hepatic coccidio- a crash, followed by a struggle on the sis. On August 5, 1943, Dr. R. E. ground. With the aid of a flashlight the Yeatter of the Illinois Natural History hunter saw the squirrel and weasel plainly.

Survey collected near Urbana a very weak The squirrel escaped, but it is not knov\n female fox squirrel ; diagnosis in the how badly it may have been injured. University's Animal Pathology Labor- The senior writer once flushed a feral atory "... revealed the presence of small, cat that w'as obviously trying to stalk a circumscribed white foci in the liver and barking fox squirrel. On snow' in north- spleen. In view of these lesions and the ern Illinois he observed a red fox stalk a history of the squirrel having been found fox squirrel that was busily engaged in sick, we regard the possibility of tularemia eating an Osage orange fruit, but the fox in this animal as being quite good . . . was frightened before reaching a springing cultures were not made." This female position. On another occasion the senior had recently nursed young. author saw a red fox leap upon and cap- The writers and others of the Illinois ture a badly wounded fox squirrel, but Natural History Survey staff sometimes shouts caused the fox to drop its victim found dead squirrels in wood duck nest and dash away. boxes. Usually these squirrels w^ere so Fox and gray squirrels caught in steel badly decomposed that cause of death traps were occasionally attacked by hawks, could not be determined. The number of free-ranging dogs and other predators. squirrels found dead was not great, and The red-shouldered hawk and red-tailed the over-all evidence suggests that no ap- hawk were the only raptors actually preciable number of these animals die of flushed from trapped animals. A trapped diseases or the effects of parasitism. fox squirrel, caught late in the afternoon, was killed during the night by a weasel. PREDATION Dogs are known to have eaten three fox squirrels and one gray squirrel caught in Predation losses in squirrel populations traps. It is recognized, of course, that are unimportant in Illinois. There are trapped squirrels attract the attention of numerous published reports of squirrels predators and offer easy prey, making them being taken by hawks, owls, dogs and other unreliable criteria for measuring predation predators, but the writers found little losses. evidence that such losses reach serious pro- portions in this state. Extreme agility and BREEDING a speed that attains a maximum of 12 miles per hour in the fox squirrel (Cottam The term breeding as usually employed 1941), and probably an equal speed in the in this study includes pre-mating behavior, gray squirrel, enable both species to elude mating and such physiological aspects of most predators effectively. breeding as oestrus, pregnancy, testes de- In January, 1941, in the examination velopment and changes in the Cowper's of 680 wood duck boxes, one weak male glands. fox squirrel was found that showed con- During the period of investigation, data clusive evidence of having been attacked on breeding or young rearing were ob- by a raptoral bird. Talon punctures on tained from a total of 4,790 squirrels, the dorsal surface reached to the body which are listed in table 1 1 by species and cavity. Mange was present under the according to time and manner collected. forelegs and about the hocks. When re- The 1,075 squirrels shot or steel-trapped leased, the squirrel appeared dazed and by the waiters and used for detailed 474 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

Table 11.—Squirrels counted or collected for study in Illinois, 1940—1943.

How Collected OR Counted September, 1945 Brown & Yeager: Squirrels in Illinois 475 a time, second that is, during the summer, 1 he annual breeding cycle of males in in their first 18 months after birth. Fe- Illinois was found to coincide approximately males from summer litters are usually too with that of females, but the two peaks immature to breed during the ensuing are less distinct in the males, which appear winter season, at an age of 7 months or to be in breeding condition continuously less, but they breed during the following from late fall to midsummer, although a summer, at an age of about a year, minor decline is apparent in February and 'i'he gray squirrel has been found to March, fig. 9 and table 14. The data

Table 13.—Generalized peak mating dates of squirrels in three Illinois zones, based mainly on 2 years of study. .July 1, 1940, to June ?>(). 1942. 476 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 per's glands and evidence of oestrus. In in the percentage of females showing oes- the first three characteristics, all peculiar trus, fig. 8, assuming that peak oestrus and to males, there was close similarity but mating occur simultaneously, or nearly not exact uniformity in the two species. so. Dates given in table 13 are in general In both fox and gray squirrels, testes agreement with findings reported by other length and weight peaks were reached workers. before or by the time of peak mating. It The chronology of squirrel breeding is evident that none of the criteria based data in Illinois, including the earliest, on male organs are fully satisfactory for latest and peak dates for various repro- determining the breeding seasons, and for ductive activities or conditions, are given this reason we have placed greater reliance in table 16. Peak dates are applicable OESTRUS dJ 80

10 3 60

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Table 16.—Chronology of breeding in female squirrels in Illinois; data obtained mainly July 1, 1940, to June 30, 1942. Peak dates are applicable particularly to central zone. September, 1945 Brown & Yeager: Squirrels in Illinois 481

The writers believe that most of the into two or more separate chases. The females not breeding during the first or chases involving nine and six gray squir- winter season fail to do so because of im- rels, respectively, occurred late in the fore- maturity or senility. Of the two causes, noon. Observations similar to the fore- immaturity is probably the more common. going w^ere made by Baker (1944) in Probably poor physical condition is the Texas. most important cause of the failure of In both species, barking or "chatting" some old females to produce the second- was noticed more in December than in season litter. any other month, but it was more or less The first and last dates of reproductive common throughout the summer, fall and condition or activity observed in Illinois early winter. Intermittent barking may during this study and the apparent season occur during any month. Although bark- duration are given in table 17. Season ing is characteristic of mating behavior, length appears to be about the same in it may, of course, denote alarm, surprise, the two species. anger and probabl\' other reactions.

Mating Chase Physiological Aspects

The most obvious indication of breeding In studying the physiological aspects of seasons in squirrels is the mating chase. breeding, it was necessary, due to limita- Fox squirrels appear to be shier than tions of personnel and to field conditions, gray squirrels in their mating activities. to rely upon gross laboratory examination During the present study, the number of rather than the more precise technique of mating chases observed, in proportion to vaginal smears and gonad sectioning with populations, was less in fox squirrels ; like- microscopical study. wise, the average number of fox squirrels Mossman, Lawlah k Bradley (1932), per chase was less. Seldom w^re more who studied the male squirrel reproductive than three fox squirrels observed in a tract, including the Cowper's glands, re- single chase, whereas, in gray squirrels, ported the male reproductive organs in fox observations were made on chases of nine and gray squirrels to be similar. and of six animals, and many of five or Testes.—In both species the testes, fig. less. The average mating group, how- 10 and table 14, began to enlarge in Sep- ever, even in gray squirrels, involved only tember. In mature males, enlargement three or four animals. Chases were en- was from a flaccid to a turgid condition. acted indiscriminately in trees, on logs For the first breeding season the maximum and on the ground. average testis length, December 1-15, was In the chase in which nine gray squirrels 30.4 millimeters in fox squirrels, and, De- participated, two of the animals were fe- cember 16-January 15, 27.7 millimeters males, and it is believed that the remaining in gray squirrels. Testis length during seven were males, one a juvenile. The the second breeding season was slightly two females barked continuously. One greater than in the first or winter season female, despite her calling, turned and in fox squirrels, but slightly less in gray fought the nearest male when pursued too squirrels. Following the second season, closely; the other, when chased into the testes became much smaller and ap- isolated positions, such as the smaller parently inactive; the minimum average branches of a tree, was mounted by several length in mature males for any 15-day males, but copulation was not observed. period was 20.4 millimeters in fox squir- One of the females was mounted as she rels and 19.0 millimeters in gray squirrels. raced up a tree, but she fell upon reaching These measurements were reached in late the top, whereupon the male lost his August and early September, respectively-. position. The nearest pursuing male At this time, the testes may have been often turned to drive back his rivals. drawn into the abdominal cavity, and the This chase covered an acre of dense un- dormant-like condition have continued un- dergrowth, lasted about 20 minutes, and til some time in September, when the was well advertised by continuous barking organs began an increase in size that con- and noisy quarreling. Chases involving a tinued until the winter maximum was large number of squirrels sometimes split reached. Testes measurements for juve- 1

482 Illinois Natural History Survey Bulletin Vol 23, Art. 5 nile males were, of course, much smaller after which development was rapid. The than for adults, the difference being great- maximum diameter of the glands in each er in the fall than in the spring. species was about 25 millimeters, reached Weight of testes, which may be a some- during the latter half of December. The what more accurate indication of breeding spring maximum observed was about 23

B, adult gray Fig. 10.—Testes of adult and juvenile squirrels. A, adult fox squirrel ; squirrel; C, juvenile fox squirrel; D, juvenile gray squirrel. Epididymis removed in right example of each pair. Coles and Piatt counties, late January, 1944.

stage than testes length, showed greater millimeters, attained about the end of May fluctuation during the breeding seasons in fox squirrels and the last 2 weeks of than the length measurement. In fox June in gray squirrels. The number of squirrels, peak average weights of 7.38 gray squirrels examined was so small that grams and 7.84 grams for the testes were the data for them may not be representa- reached in late December and late April, tive; comparable data for the fox squirrel respectively. In gray squirrels, corres- indicate that the peak diameter of ponding data, less reliable due to fewer Cowper's glands in the gray squirrel samples, averaged 6.16 grams for the testes was reached earlier in June than is shown early in January and 5.73 in May; the in table 14. Following cessation of average of a small number of samples in breeding in the summer, these glands be- early April was 5.80 grams. Adult and came dormant and decreased so greatly m\ juvenile testes are illustrated in fig. 10. size that, in August, September and Oc- Gowper's Glands.—The location, tober, they were diflfiicult to find, even by large size and relationship to breeding dissection of the animals. activity of the Cowper's glands make them Scrotum.—Field observations showed a good criterion by which to judge the that, as the breeding season progressed, sexual condition of males. These glands, the scrotum became comparatively smooth, fig. 11, are paired, discoid bodies, the and both skin and hair assumed an oily,

function of which is production of sperm- brown-stained appearance, fig. 5. Follow- carrying fluid. The glands, coiled like a ing the mating season, in June or later, Polygyra snail shell, are situated one on the scrotum lost this rubbed, blackened each side of the rectum. Connection with appearance through sloughing of the skin the penis is by duct. When turgid, these and replacement of hair and underfur in glands extend posteriorly, distending the the molting process. The new skin of the anal orifice and increasing the average sac was of lighter pigmentation, as in juve- body length by about 10 millimeters. nile males, fig. 5. In "old squirrels, the Enlargement in the Cowper's glands in loose saclike condition of the scrotum pre- both species was first observed in October, vailed, whereas in juveniles, because ofi September, 1945 Brown & Yeager: Squirrels in Illinois 483 the more abdominal position of the testes, Pregnancy.—An attempt was made the scrotum was less pendent. early in the survey to distinguish oestrus Oestrus.—The earliest evidence of and early pregnancy by the use of vaginal first-season or winter oestrus observed in smears, but this proved impractical under fox squirrel females was December 11 in conditions prevailing in the field. The Alexander Count\^ (southern zone), tables oestrual period thus was probably not dis-

15, 16 and 17. The latest oestrus records tinguished as precisely as is desirable, and for the first season in the southern and perhaps an unknown number of very central zones were Januarj' 27 ; the two early pregnancies were listed under the observations were a year apart. In gray heading of oestrus. Pregnancy could be squirrels the earliest evidence of winter determined with some certainty by noting oestrus was December 16, and the latest the relaxed and perforated state of the was February 11, both observations in the vulva and development of the mammae. southern zone. Somewhat advanced stages of pregnancy The external indication of oestrus, (15 millimeter fetuses) could be detected commonly called "heat," is a swollen, pro- by palpating the lower abdomen. truding condition of the vulva. During The earliest and latest first-season oestrus the uterus is enlarged and con- pregnancy records for fox squirrels were gested with blood, by w'hich the vulva is January 1 (one animal with 3 fetuses commonly discolored. This condition is averaging 6 millimeters in length) and easily observed in external examination. March 22 (one animal with 3 fetuses Following copulation the congested con- averaging 19 millimeters in length), table dition of the uterus clears. The uterus 16. The first-season peak of fox squirrel becomes spongy and thick-walled, and pregnancy, based on 43 adult females, 23 fetal nodes, 3 millimeters in length, appear of them pregnant, table 15, came during about 10 davs after successful coitus. the first half of February. In gray squir-

Fig. 11.—Glans penis and urethra of adult male squirrel, with Cowper's glands attached in an uncoiled and in a nearly natural position in each case. Left, fox squirrel; right, gray squirrel. Coles County, late January, 1944, Art. 5 484 Illinois Natural History Survey Bulletin Vol. 23.

for fox squirrels, and July 5 rels, the earliest and latest pregnancy August 29 squirrels, table records were January 13 (one animal with and September 9 for gray taken on August 2 fetuses averaging 4 millimeters in 16. Fox squirrel females length) and March 29 (one animal with 15 and 29 each contained 2 fetuses; those millimeters in 3 fetuses averaging 15 millimeters in of the first averaged 20 length), table 16. Peak gray squirrel length and those of the second 48 milli- age pregnancy for the first season, based on meters. Fig. 12 shows embryos at the 16 adult females, 9 of them pregnant, of about 15 days in the uterus of a fox came about the middle of February, table squirrel. writers have re- 15. The earliest and latest second-season Gestation.—Previous pregnancy records were June 19 and ported difficulty in determining exactly the

Fig. 12.—Uterus of pregnant fox squirrel. Right horn contains two normal fetuses and one apparently in process of being resorbed, September, 1945 Brown & YEAGtR: Squirrels in Illinois 485

Fig. 13.—Lactating gray squirrels, Coles County, September 15, 19+4. Note Histended appearance of mammary glands and nipples. gestation period in squirrels. Allen gested by Goodrum, Baumgartner and (1942, 1943) and Lyon (1936) indicated other authors mentioned above. that gestation in fox squirrels is probabh' Mammae.— In both fox and gray about 45 days. Since the oestrual peak in squirrels, the mammae are eight in num- this species in Illinois, as determined by ber and are arranged in four pairs, oc- the present study, was late in December cupying the ventral body surface behind and early in January, a 45-day term would the forelegs, fig. 13. Allen (1942) des- place the birth peak in February. The ignated the mammae positions as pectoral oestrus records in table 15 and the birth 1, pectoral 2, abdominal and inguinal. He records in table 18 indicate that the ges- stated that, in the fox squirrel, the abdomi- tation period in Illinois fox squirrels is nal pair develops first following insemina- about 45 days. Seton (1928, 4:44), tion, and that the usual order of develop- quoting Powers, gives the gestation period ment is abdominal, inguinal, pectoral 2 in gray, squirrels as 44 days. Goodrum and pectoral 1. In some cases, however, (1940) and Baumgartner' (1940) also Allen found that the pectoral 2 and ab- considered that 44 days was the probable dominal pairs developed equally, or the term. The oestrus-mating peak in the former preceded the latter in development. small number of gray squirrels observed The pectoral 1 pair may not be functional in the Illinois study was early or mid in some cases. Milk can be squeezed January, table 15, and the birth peak was from the nipples a few days before the early March, table 18, indicating an av- young are born and, in some cases at least, erage gestation period of about that sug- for 2 or 3 weeks after the young are 486 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

weaned. Thus the glands may contain pigmented condition of the nipples remains milk for 3 months or more subsequent to apparent, fig. 6. parturition. The teats and mammary glands of YOUNG REARING squirrels develop rapidly after pregnancy begins. In both species, the teats swell In the term young rearing, as it is and become black pigmented. The glan- usually employed in this paper, are in- dular tissue becomes thickened and spreads cluded the biological phenomena associated to cover the ventral body surface. Hair with young squirrels. on the mammae of nursing females becomes worn and matted, and the nipples Birth Dates show^ an obviously distended and stretched condition, fig. 13. On cessation of lac- In the spring of 1941 birth dates were tation the teats become greatly reduced estimated for 35 litters of fox squirrels and, in fox squirrels at least, the black and 4 litters of gray squirrels. Most of

Table 18.—Birth dates by 2-week periods for 35 fox squirrel litters and 4 gray squirrel litters in Illinois, all zones, spring, 1941.

Species September, 1945 Brown & Yeager: Squirrels in Illinois 487

the litters had been born in wood duck earliest and latest records of lactation nest boxes, but a few of the fox squirrels during the first season are for fox squir- in leaf nests. The distribution of esti- rels, February 20 and May 27 ; for gray

mated birth dates by 2-week periods is squirrels. March 1 and May 31, table 16. shown in table 18. Most fox squirrel females had finished In addition to the fox squirrel births nursing by May 1 ; most gray squirrel included in table 18 were those involving females by May 15. Lactation data for two nursing females taken on February both species and for both breeding seasons 20 and another on February 21. In these are given by 2-week periods in table 15. animals the uterus had returned to ap- As indicated in table 15, lactation in the proximately normal size and all showed Illinois fox squirrels studied was most placental scars. Scars do not appear until prevalent in March and August, when 78 the uterus has cleared, several days follow- and 44 per cent, respectively, of the adult ing birth of the young. females handled showed this condition. The earliest first-season birth date es- In gray squirrels, lactation was most prev- timated for Illinois gray squirrels (only alent in April and September, when 75 four litters observed) was February 20 and 60 per cent, respectively, of the adult and the latest March 18. One pregnant females handled were nursing. In some gray squirrel female, almost to term, was females the cessation of lactation was taken March 29, indicating first-season found to be delayed. In both species, young are born at least through March. females showing second-season oestrus still No birth records were obtained for the carried first-season milk, which could second season in 1941, or for either the readily be exuded by pinching the nipples. first or second season in 1942. From the The young observed during the study were numerous records of oestrus, pregnancy weaned when about 8 or 10 weeks old. and lactation in both species, however, the birth peaks can be approximated. Development of Young

Birth Sites Fox squirrels handled shortly after birth were 50 to 60 millimeters in length and Because squirrel dens and leaf nests are weighed 14 to 18 grams (about one-half discussed later in this report, no details ounce). They were dark pinkish, naked, on birth sites are given here. Although except for vibrissae about the nose and \oung are born in both cavity and leaf chin, and virtually helpless. The claws

nests, it appears that the cavity type is were well developed. Both the eyes and preferred. More litters were found in ears were closed, and neither the upper nor natural cavities than in leaf nests, and lower incisors had erupted. The vibrissae many litters were found in boxes construct- grew rapidly, and hair first appeared on ed and erected for wood ducks. The the upper dorsal surface at an age of 8 senior author checked, on the Mason or 10 days. Further growth character- County State Forest, a total of 89 leaf istics are detailed in table 19, data for nests during the first half of April and which were obtained principally from found only 2 litters of partl_\' grown fox caged animals. squirrels. Only fox squirrels inhabited Because of a growth differential be- this area. Goodrum (1940) states that tween caged and wild specimens, the data in east Texas gray squirrels are usually- in table 19 may vary from corresponding born in hollows of trees, but that they data for wild squirrels by 2 or 3 days. may be transferred to leaf nests. Both Information relating to pelage is prob- species move their young from nest to ably subject to wider variation than that nest when disturbed. On such occasions pertaining to eyes, ears, teeth or weight. the mother grasps the young in her mouth, There was no opportunity during the in the manner of a cat moving her kittens. study to weigh or measure gray squirrels at birth. These animals are smaller and Lactation somewhat lighter in color than fox squirrels. The young of both fox and gray squir- At weaning age, or during late April rels nurse for 8 weeks or more. The and May and late August and September I

488 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

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for most individuals, fox squirrels were young in nests, of fetuses and placental found to average about one-half pound in scars, table 20. As found from study weight; gray squirrels, on the basis of a of 85 litters of fox squirrels and 34 litters very few samples, about one-third pound of gray squirrels, the average size of litters or somewhat less. By mid June, young in grays was somewhat larger than that fox squirrels handled averaged slightly in fox squirrels, but the difference was not more than 1 pound, and young gray squir- significant. Neither was there a great rels about 0.6 pound. difference in the size of the first- and At the time of weaning the pelage in second-season litters in either species. both species, including that of the tail, was Gray squirrels showed the larger average well developed. The young animals were in the first season; fox squirrels the larger active, being able to leave the nest and, in the second season. with some awkwardness, to forage for During the course of this study, in- buds and other food. Manual dexterity teresting data were gathered on the pos- in gray squirrels seemed to develop some- sible effect of food quality on fecundity. what more rapidly than in fox squirrels. The investigation was conducted mainlj At or near weaning age the young of both on the rougher, wooded parts of Illinois, species began to join the adults in travels, where soil fertility is comparatively low, and were often observed in litter groups and where the staple squirrel foods con- feeding on elm seeds and buds in the spring, sist principally of nuts, acorns, fruits, and acorns and hickory nuts in the late berries and buds. Other investigators in summer and early fall. It is doubtful, Illinois, working on the more fertile ag- however, if 8- to 10-week old squirrels are ricultural areas where corn is the main fully self-sustaining. Allen (1942, 1943) staple, found that litter size in fox squir- considers that fox squirrels are not self- rels there was larger than was found by sustaining until they are between 3 and the writers on wooded range, table 21. 4 months old, a belief shared by the present The nutritional value of corn is prob- writers. Development in first- and second- ably greater than that of the combination season squirrels appears to be at about the of nuts, acorns, buds and fruits of wooded same rate. localities, and since, on most Illinois farms,

corn is abundant at all seasons, either at Litter Size cribs or in fields, farmland fox squirrels in this state are well nourished. Most The average size of litters in Illinois woods-inhabiting squirrels in Illinois ap- squirrels was determined by counts of pear to suffer no serious food shortages,

Table 21.—Litter size in fox squirrels in two types of Illinois habitat, 1941 and 1942. :

490 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

but midwinter supplies are often less include them under two main headings abundant in the woodlands than in farm black prairie and woodlands. regions. The difference in average litter size in the two habitats, as shown in table Black Prairie Habitats 21, is significant. The writers believe that the superior quality and quantity of The black prairie region of Illinois is food characteristic of many farmland hab- overwhelmingly agricultural and is dom- itats may be the main reason for the differ- inated by the production of corn, soybeans ential in litter size. No comparative data and wheat. It contains very little wooded are available for gray squirrels, but it is area, and therefore has an acute shortage of interest that 34 litters found in wood- of den trees. Subtypes making up the land types averaged 2.68 young, table 20, squirrel range in this region are woodlots, a number smaller than the average for wooded stream bottoms, hedgerows, and farmland fox squirrels. fields and farmyards with scattered trees or groves. The woodlots are predomi- ILLINOIS HABITATS nantly oak-hickory. Walnut plantations are widely scattered and aggregate only a

Forest cover is the basic requirement of very small acreage. In the bottoms, the fox and gray squirrel habitats, and the main trees are elms, maples, sycamore,

kinds, combinations and sizes of the trees, white ash and other wet-site species ; and shrubs and brambles they contain, and the on the bluffs, oaks and hickories are the

Fig. 14.—Typical farm habitat of fox squirrels on Illinois black prairie type, Champaign County, February, 1941.

density of the stand, to a large extent principal trees. The only important determine their quality. Since the oc- hedgerow species is the Osage orange, the currence and growth of woody vegetation older and larger hedges of which are now vary with soil, climate and the activities steadily being pulled. Practically all of man and other animals, the types of wooded areas on the black prairie are squirrel habitats in Illinois are many. grazed. Although the variations in squirrel habitats Staple squirrel foods' in this region, in

are not readily classified, it is possible to probaljle order of importance, are corn. September, 1945 Brown & Yeager: Squirrels in Illinois 491

Fig. 15.—Mature elm-maple river-bottom type, Piatt County. Pin oak through the northern two-thirds of IllinoiSj and pecan and other hickories in the southern half of the state, add to the quality of many river-bottom squirrel habitats by helping to insure a year around food supply. The pure elm-maple type is rich in squirrel foods during the spring, but low in this respect during other seasons of the year. ,

492 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 acorns, nuts, buds and seeds, especially of most important wooded areas of this type elms and maples, and Osage orange fruits. are along the Mississippi, Illinois, Ohio, Water is supplied by streams and ditches Wabash, Rock, Kaskaskia, Embarrass, Big and probably by such succulent foods as Muddy and Cache rivers and aggregate berries and green corn. The fox squirrel more than 2,250,000 acres (Case & Myers

Fig. 16.—The cypress or cypress-tupelo gum type in the extreme southern tip of Illinois is fair squirrel range. Foods offered by this type are cypress seeds and tupelo gum drupes. Shown here is a tupelo gum bottom, Massac County.

exclusively is found in the black prairie, 1934). The variety of trees and shrubs except in towns and in a few heavily wood- on this extensive area is great. The prin- ed and ungrazed bottoms. Fig. 14 il- cipal bottomland trees in the northern half lustrates this type. of the state are elms and maples, and in the southern half these species plus oak,

Woodland Habitats hickory and pecan ; cypress and tupelo gum swamps are found in a few wet bottoms The term woodland, as used here, de- in extreme southern Illinois. The bluffs notes squirrel habitats other than the in all cases support oaks and hickories, with woodlot types found on the black prairie. walnut occurring in many localities. The Illinois woodland habitats contain a Shrubs are of wide variety and may be con- vastly larger total wooded area, as well sidered an important part of the cover. as much larger wooded tracts, than the A bottomland habitat in central Illinois black prairie. A rough distinction be- is illustrated in fig. 15. A southern Illi- tween the two types of squirrel habitat is nois habitat, principally tupelo gum, is that black prairie woodlots are surrounded shown in fig. 16. by fields, while woodland range is only The river bluffs and bottoms type is irregularly broken by cultivated fields or found in Illinois in varying densities and other open land. Woodland habitats, for stages of maturity. Grazing is the rule, convenience, may be divided into two as in black prairie woodlots, but not many

main subtypes : the river bluffs and bottoms of the bottomland areas are seriously in- and the wooded upland. jured as squirrel range by this practice. River BluflFs and Bottoms.—Con- Den trees are generally ample, but ex- stituting this type are the bottoms and tensive lumbering is now seriously re- contiguous bluffs of the various river sys- ducing both the number of den trees and tems bordering and within Illinois. The the number of areas containing such trees. September, 1945 Brown & Yeager: Squirrels in Illinois 493

Staple foods, in probable order of impor- der fields of corn, which thus becomes tance, are acorns, nuts, buds and seeds available as staple food, fig. 17. From the (especially of elms and maples), and corn. standpoint of food, the wooded upland Water is amply supplied by streams, lakes type affords a habitat of higher quality and springs. Both fox and gray squirrels than does the river bluffs and bottoms are common in this habitat, but the latter type, except perhaps in those bottomland are much more restricted than the former situations in which pecans are plentiful. in distribution. Den trees are not so abundant on the Wooded Upland.—The wooded up- wooded uplands as on the bottoms and land possesses many of the qualities of the bluffs, due both to the presence of large river bluffs and bottoms type, but contains numbers of hickories and other species not a larger percentage of oak, hickory, and, in given to formation of cavities and to the northwestern, central and southwestern lo- fact that upland stands have been more con- calities, of walnut. Fruit-bearing shrubs, tinuously and selectively logged, especially wild grapes, bittersweet and brambles sup- of oaks. The residual upland stands, as plement the basic food supply of nuts and a result, are younger and more vigorous. acorns. Many of the wooded areas bor- Despite this condition there is no pressing

Fig. 17.—Good squirrel country in Effingham County. Oak-hickory woods adjacent to cornfields constitute a habitat with a dependable year around food supply for fox and gray squirrels. 494 Illinois Natural History Survey Bulletin Vol.23, Art. 5

Fig. 18.—Oak-hickory type in Piatt County, a high quality fox squirrel habitat. Here various tree species provide food through most of the year. September, 1945 Brown & Yeager: Squirrels in Illinois 495

den shortage on the wooded uplands. bluffs, being restricted generally to areas Water is not so plentiful, but in most up- having heavy forest cover. Wooded upland areas is amply supplied by small runs land habitats are shown in figs. 18 and 19. and springs. Grazing is heavier than on the more rugged bluffs. Fire offers a Miscellaneous Habitats somewhat greater hazard. The cutting of walnut for military use has been more Throughout Illinois there are habitat widespread and intensive on the wooded types other than those described where uplands than in any other squirrel habitat squirrels occur in varying numbers. The in Illinois. most common are residence districts of The w'ooded upland type reaches its best cities and villages, parks, estates, ceme- development in several southern and teries and college campuses. There may southwestern counties, but there is an ap- be some question as to whether urban- preciable acreage of it in Jo Daviess, Car- dwelling animals are comparable to wild roll and other northw'estern counties. or non-urban populations. Observations The extensive black oak stands in Mason by the writers indicate that wild and urban and Cass counties may be considered a part squirrels have identical breeding periods of the wooded upland type. The aggregate and great similarity in feeding and nesting wooded upland acreage is roughly twice habits. It is estimated that the adjoining that of the river bluffs and bottoms, or cities of Champaign and Urbana, with a about 4,500,000 acres. Both fox and gray total human population of about 40,000, squirrels inhabit the upland type, the for- have 1,000 squirrels, all of which are gray.

mer occurring throughout, and the latter, It is probable that no Illinois municipality

as in the case of the river bottoms and is without a squirrel population, and that

Fig. 19.—Dense oak-hickory-hard maple type, Coles Coiinty, unpastured and undamaged by fire. A typical and high quality range for both fox and gray squirrels. 496 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

200,000 or more squirrels are resident in every opportunity to observe and record municipal areas in the state. squirrel feeding was utilized. Many as- Stripmines, which provide an unimpor- pects of the study—particularly those as- tant habitat in the state, are best repre- sociated with collecting specimens, trap- sented in Vermilion, Perry, Saline and ping live animals and making inspections Fulton counties (Yeager 1942), fig. 20. of den boxes—were well adapted to the Only in Vermilion County has forest suc- making of reliable observations. In 716 cession in this type of habitat advanced hours devoted to hunting, several hundred far enough to attract gray squirrels. The records on squirrel feeding were gathered. cover usually found in stripmine areas is Although the nature of the data precludes an early stage of river-bottom forest, quantitative evaluation, the writers be- consisting mainly of Cottonwood, syca- lieve that a good general picture of feed- more, willows, elms and maples, a coming, based on frequency of observation, was bination low in quality as all-year range. obtained. Buds, flowers and seeds of trees, and fruits In the following discussion, as well as in of brambles and wild strawberries offer table 22, no food is listed unless squirrels an appreciable amount of spring and were observed eating it, or unless other summer forage. Hickory nuts and acorns positive evidence of its having been eaten are seldom represented in these stands. was obtained. Food remains of squirrels Probably not more than a few hundred were easily distinguished from those of squirrels, most of which are fox squirrels, other rodents by the location of "cuttings" are resident on Illinois stripped lands. as well as by incisor marks on them (Pearce 1938). Only fresh material was FOODS AND FEEDING used in these determinations. It was impractical to distinguish between fox and In this investigation no study of squir- gray squirrel food remains, and for this rel foods based on detailed laboratory anal- reason, as well as because of great similar- ysis of stomach contents was attempted. ity in food habitats, this section of our re-

Through 2 years of field work, however, port is, in general, applicable to both spe-

Fig. 20.—Stripmines, lacking in trees bearing acorns and nuts, are poor year around squirrel habitats. Vermilion County. September, 1945 Brown & Yeager: Squirrels ix Illinois 497

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Fifj. 21.— This Piatt County woodlot of mixed hardwoods, including hickory, black oak, white oak, walnut, elm and soft maple, offers staple foods at all seasons. A nearby cornfield and an Osage orange hedge supplement this food supply. The mature trees contain an ample number of cavities. These characteristics probably represent the optimum in fox squirrel habitat. cics. Information peculiar to either spe- {Cratae(/us mollis) by gra\' squirrels in cies is detailed separately. Ohio. Woods (1941) reported that a blackberry patch, wild plum thicket or cul- Food Sources tivated orchard may furnish the bulk of the food for one or a few squirrels during the In table 22, 76 species or groups of few weeks when fruits of such plantings squirrel food plants are tabulated. In- are available. However, no matter how cluded are 56 trees and shrubs, 2 groups varied and abundant auxiliary seasonal of vines, 4 brambles, 6 wild herbs, 7 cul- foods may be, most wild squirrels arc tivated crops and various fungi. The list forced to rely for much of the year on one is, of course, incomplete; the writers are or more of the staples listed. An environ- certain that other plants, particularly ment without a \ ariety of staples may be of herbs, are taken in small amounts. The little value, and may actually be uninhab- unlisted foods, however, are of little sig- itable, except when auxiliary foods prevail. nificance in the squirrel dietary. Common examples of such a deficient en- Although many items are listed in table vironment are river-bottom forests of pure 22, the important staple food sources of elm-maple or extensive cottonwood-willow Illinois squirrels comprise only a half flats, even those bordering cornfields. dozen plant groups. There are the hick- From the standpoint of food, the impor- ories, including pecan, and the oaks, wal- tance of mixed stands in squirrel habitats nuts, elms, mulberry and field corn. An is clearly apparent, fig. 21. I his factor

imposing list of other foods ma\' be im- is discussed by Goodrum (1938). Most portant locally or seasonally. E.xamples of the original forests were of suitable are Osage orange and wild grapes. Boul- composition, especially those of hardwoods conifers. ware ( 1941 ) reported local use of eucalyp- or mixtures of hardwoods and tus by fox squirrels in California, and Most of the larger natural stands now- Dambach (1942) similar use of hawthorn present in Illinois meet the staple food '

498 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

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O J. 2 -. I' S 5 ^ u 3 ^' -if N « c CI eg u 3 b! O Id U ^ 0:: c^ CQ a: 502 Illinois Natural History Survey Bulletin Fol. 23, Art. 5 requirements of both fox and gray squir- there, and they were somewhat under- rels, and many woodlots, supplemented by weight, mangy and otherwise in subnormal agricultural crops, particularly corn, meet condition during the late winter of 1940- these requirements for fox squirrels. 41. The near failure of pin oak acorns The writers found during 2 years of on the area in 1940 is believed to have field work only one extensive squirrel been the main reason for this situation. habitat showing definite evidence of food At least one other area was found where shortage. This was the Mississippi River serious food deficiency would likely result bottoms in Carroll County, where pin from mast failure. This was the sand oaks furnished the main squirrel fare over region of Cass and Mason counties, where a large area. Only fox squirrels occurred extensive and nearly pure stands of black

Fig. 22.—Nearly pure black oak stand in Mason County, Illinois. During years of mast failure, pronounced squirrel food shortage may exist in this type due to lack of variety in staple food species. Den boxes, erected for wood ducks, are readily used by fox squirrels. September, 1945 Brown & Yeager: Squirrels ix Illinois 503

Fig. 23.—Elm (left) and maple buds and flowers offer the first squirrel food jiroduced each year.

oak occurred, fig. 22. Only fox squirrels ( 1943) to feed on caterpillars of the half- inhabited this locality, and during years wing geometer {Phiyalia titea). Good- of poor acorn crops they would be forced rum (1940) found that in Texas over 3.5 to depend mainly on residues of corn, rye per cent of the food of gray squirrels con- and other grains, and such natural foods sisted of insects, mainly lepidopterous lar- as wild grapes, bittersweet and miscel- vae. He also presented limited evidence laneous seeds and herbage. to show that animal food is necessary to In practically every section of Illinois, successful breeding. Both fox and gray a general failure of oak mast, and in some squirrels are said by Seton (1928) to use sections, especially in southern and south- insects and other animal matter. The w'estern localities, failure of wild pecans evidence is general that animal life, par- in the bottoms and hickories and black ticularly insects, constitutes a small but walnuts on the uplands might create un- more or less important food source for tree fortunate food contingencies during the squirrels. late winter and early spring. That serious Brooks (1922) reported the use of food shortages did not prevail in many in- chestnut bark and other tree bark by gray

stances in 1940—1942 is indicated by the squirrels in West Virginia, and Allen

good to excellent condition of the several ( 1943) reported use of maple bark by fox hundred squirrels examined, some of which squirrels in Michigan. 'I'he use of bark were collected during every month of the by fox squirrels was observed by the junior first 2 years of study. author in Coles County, Illinois. The nature of the food studies made in The effect of lumbering, fire and graz- this investigation did not permit deter- ing on squirrel food sources is discussed mination of either the number or impor- in other sections. tance of animal foods taken by squirrels in Illinois. Numerous writers, however, Food Succession have called attention to the inclusion of insects and other animal forms in the Succession in the use of foods by squir- dietary. Davis (1907. 1924) reported rels is somewhat distinct, the Illinois study the destruction of acorn weevil larvae showed, and the order of succession in this {Balaninus) and oak apple galls {Ain- state is approximately the same in both phibolips confluens) by gray squirrels. species. The first foods of the late winter These animals were observed by Hamilton or spring season are the buds and flowers 504 Illinois Natural History Survey Bulletin Vol.23. Art. 5: of several hardwoods, particularly of elms, probably other acorns may be as early as maples and oaks, and the buds of sweet July 15 in Illinois, most mast species are gum, ash and other tree species, fig. 23. not used extensively until about mid "Budding," well described in gray squir- August. Fruits of oaks, sugar maple and in rels by Nichols (1927), Deuber (1934) honey locust are commonly eaten and Terres (1939), begins in February in August and later, and are followed by

Fig, 24.—Corn cribs or corn shocks or fields adjacent to squirrel range offer the best feeding stations, and may carry normal squirrel populations through severe food shortages. Pike County. southern Illinois and extends into April. nuts of the hickories and walnuts. Pecans, During late April and May, the winged beechnuts, hazelnuts, fall grapes, Osage seeds of the American elm are an impor- orange fruits, pokeberries, ripe corn and tant item, in the diet of Illinois squirrels. numerous other foods are generally used in From mid May until late July mulberries late August or September and later. In are utilized in all regions where they oc- the extreme southern tip of the state, the cur. Various bramble fruits, as well as seeds of cypress and tupelo gum are appre- wild cherries, wild grapes, wild strawber- ciable food items in late October. Al- ries and wild plums, are eaten during the though rare in Illinois, the seeds of various summer and early fall as they become pines are a staple fox squirrel food wher- available. Corn, in the milk stage, is ever the range of the trees and the animal eagerly sought by both species during July coincide. and August, but is much more important Following the flush of mast availability to fox squirrels than to gray squirrels be- in September and October, acorns and nuts cause of the wide occurrence of the former supply the bulk of squirrel food during the in open, agricultural range. Fungi winter and early spring. Such food is and herbage are taken probably in maxi- taken both from residues on the ground mum quantities during the spring and and from cached supplies. It is after summer ground feeding, in which fungi these sources are largely used up, and be- ; and herbage are mainly found, is most fore the availability of buds, that the food prevalent in July and August. It is dur- problem of squirrels most often becomes ing this period of extensive ground feeding acute. In many farm localities, corn, that squirrels are most difficult to see in whether residue, shocked or cribbed, is of the woods. great value during this period of deficiency,

In Illinois, July and August usher in fig- 24 ; other emergency foods consist of the principal mast season, the period of Osage orange fruits, often dug out of greatest food abundance for tree squirrels snow, still clinging box-elder seeds, dried throughout the northern hemisphere. grapes, frozen, half-decayed apples and Although initial use of black oak and such miscellaneous items as smartweed, ,

September, 1945 Brown & Yeager: Squirrels in Illinois 505

climbing buckwheat, burdock and Ameri- tribution and tendency to fruit, is easily can lotus seeds. In several instances it first in use among Illinois squirrels. Nuts was found that acorns that had fallen of the small pignut (C. oralis), occurring in water were eaten 3 or 4 months later, most commonly in east-central and south- after the winter drawdown, on areas af- ern Illinois, were found to be eaten avidly fected by navigation dams on the Missis- by both fox and gray squirrels, fig. 26. sippi River, fig. 25. Many other seeds are The mockernut (C. alba), pignut (C. undoubtedly eaten during the period of glabra), big shellbark (C laciniosa) and scarcity ; and various writers have reported most other Illinois hickories are of only greater use of animal foods, particularly secondary importance, partly because they insects, during the late winter and spring are less common than the shagbark and than at any other time. also, perhaps, because they are thicker shelled and therefore more difficult for Food Preferences squirrels to open than are the thin-shelled species. The bitternut {C. cordiformis) The acorns of every species of oak oc- although thin-shelled, is both bitter in taste curring in Illinois appear to be used by and small in size, but appears to be uti- squirrels, but because of their abundance lized. Pecan (C. pecan) is eagerly taken and wide distribution those of pin oak wherever it occurs and represents the

{Quercus palustris) , white oak {Q. alba) most important mast species in the central and black oak {Q. velutina) are the most and lower Illinois River bottomlands and important food sources. The acorns of in some southern Illinois localities. bur oak {Q. macrocarpa), shingle oak Squirrels show definite preferences when

{Q. imbricaria) , chinquapin oak {Q. several foods are abundant at one time.

Muhlenbergii) , swamp white oak {Q. During "mast years," when a dozen or bicolor) and others are taken where they more staple or substaple foods, including occur. According to Allen (1943) red hickory nuts, walnuts, pecans, acorns, oak {Q. borealis maxima) acorns are beechnuts, hazelnuts and corn, may be bitter and, in Michigan at least, appear to available in quantity from late August be used less than the fruit of most oaks. through September, hickory nuts (shag- Of the hickories, the shagbark (Carya bark and the small pignut) seem to rank ovata) , both because of its statewide dis- first in preference with both fox and gray

Fig. 25.—After winter drawdown on area affected by Mississippi River navigation dam, squirrels foraged under ice for pin oak acorns that had lain in water since the previous fall. Carroll County, January, 1941. 3

506 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

squirrels. While these nuts are available, nuts are absent, the fruit of the Osage squirrels travel greater distances for them orange seems to rank next to corn as a than for any other food and lose to a preferred food, and in numerous instances greater degree their altertness to danger was taken in winter, even when acorns when feeding on them. Pecans and black were available, fig. 27. In the early walnuts also rank high. Among fox spring, elm buds and seeds are the most squirrels living in farm habitats where used foods of both squirrel species ; in May

of Fig. 26.—Two hickory trees, heavily fruited, known to have supplied niuch of the food 20 or more Coles County squirrels (both fox and gray) from late August until late September in 1943. September, 1945 Browx & Yeager: Squirrels ix Illinois 507

Fig. 27. — Osage orange fruits provide food for fox squirrels from late summer through the winter. Cobs under the tree indicate extensive use of corn from an adjoining field. and June, mulberries apparently rank the squirrels shifted to walnuts, which first; and, during the early summer, corn were still green. Squirrels inhabiting in the milk stage is probably highest in areas short of summer foods, of which palatability rating, at least for fox squir- heavily grazed woodland is probably the rels. best Illinois example, are often driven to Because of the well-known adaptability use immature acorns. In the black oak of fox squirrels to open timber and agri- stands in Mason and Cass counties, where cultural habitats, this species makes greater the ground cover is mainly grasses, seed- use of farm crops than gray squirrels. Of lings and second-growth sprouts, immature farm-crop foods, corn is of outstanding acorns were taken by the fox squirrels resi- importance, but wheat, soybeans, oats, dent there as early as July 15. apples and other crops are popular. Field Fox squirrels were found to be more crops adjoining woodlots or other timbered tolerant of limited variety in diet than areas are used more than those in fields gray squirrels, and on many areas having some distance from such areas. Corn is only one or a very few staple foods it was the only cultivated crop used to any considerable extent by gray squirrels in Illi- nois, and this only where fields adjoin woodland suitable to their requirements. Isolated nut trees, hazel clumps or bramble patches are ordinarily monopolized by fox squirrels. Failure of any important mast species tends to hasten and increase the use of the species that produce. In 1941, the hickory nut crop was heavy over much of Illinois. Squirrels in the central zone the nuts by mid August, and began to use Fig. 28.—Svveetgum "hails" stored by a gray black walnuts were left untouched until squirrel, Horse Shoe Lake (Jame Refuge, Al- early September. In 1942, hickory mast exander County, Illinois, December, 1940. was scarce in many localities. The small This is the only instance of cavity storage supply was soon exhausted, and in August noted in tree squirrels in 4 years of field work. 508 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 noted that the squirrel population was lim- many times that both species of squirrels, ited to the former species. This situation even in regions abundantly supplied with was encountered on certain Mississippi food, made limited use of acorns, walnuts, River bottoms where pin oaks supply the hickory nuts, Osage orange fruits and main food resource; in the sand region of similar items while they were still quite Mason and Cass counties, where black oak green. What this use represented—mere- supplies the main food staple ; and on farm ly a sampling, the activity of juvenile regions throughout the state, where corn squirrels, an attempt to obtain water—was is the basis of subsistence. Food, however, not ascertained. is only one criterion for defining the preferred range of the two species. The Storing and Feeding Habits range appears to be determined by the combination of food, cover, water and pos- Storing or caching appears to be in- sibly space. stinctive in squirrels; juveniles are among In the course of field work it was noted the first to begin this activity in the fall.

Fig. 29.—Fox squirrel feeding in characteristic manner— sitting on hind legs with nut grasped between forepaws. (Photo by Gordon S. Pearsall.) Septembetj 1945 Brown & Yeager: Squirrels in Illinois 509

Caching in Michigan fox squirrels was Squirrels seem to have the ability to de- well described by Cahalane (1942). The tect unsound nuts and acorns, usually stored foods observed in the present Illi- fruits undeveloped or worm eaten. By nois study were mainly hickory nuts, wal- what means the)- make this distinction is nuts, pecans and acorns, which were com- not known, but we have many observations monly buried in the ground. Only one of squirrels dropping unsound nuts almost

30.—"Cuttings" on the ground under a hickory tree, Coles County, September, 1943.

instance of cavity storage was found : a instantly after picking them up. The un- gallon or more of sweet gum {Liquid- huiled nuts they dropped that were exam- amhar styraciflua) capsules in the hollow ined by us usually showed only one set of base of a tree of this species, fig. 28. The incisor marks ; the hulled nuts showed cache, on the Horse Shoe Lake Game little if any "cutting." Refuge, Alexander County, was the work In feeding, squirrels ordinarily sit up- of a gray squirrel. In storing, squirrels right on their hind legs, whether on a usually bury only one nut or acorn in a branch, stump, log or the ground. They place, carrying each to a point 50 to 100 possess great skill in handling food with feet from the food tree by the most direct their front paws while eating, fig. 29. route. Gray squirrels often eat on the spot where

Storing begins about September 1, and they find food, but sometimes, as with fox in both 1940 and 1941 it was noticed first squirrels usually, they carry the food to a in gray squirrels. It seems to be an ex- favorite eating place, such as a horizontal tension of the forenoon and afternoon branch, a log or stump. Animals of both feeding periods, and is conducted with species leave abundant signs in the form fewer-than-usual alerts for danger. Har- of "cuttings," figs. 30 and 31, and hunters vesting is rather thorough ; once cleaned, habitually locate them by looking under the trees are visited only infrequently. In hickory, walnut, pecan or oak trees to de- trees nearly stripped, squirrels were ob- termine the extent and recency of feeding served to go to the uppermost branches activity. The animals dislodge from trees and descend in spiral fashion until a nut more fruits than they eat but they usually was found. Acorns and nuts are gleaned eat cleanly the nuts and acorns they open. later from the ground, but apparently the Neither fox nor gray squirrels take a storing of fallen fruits does not awaken in large number of foods in making any one squirrels the intensity of purpose compa- meal. The writers opened scores of rable to that shown early in the season stomachs, but seldom found more than when stores are gathered directly from the four or five foods in any one stomach, and trees. often only one or two. Items present in 510 Illinois Natural History Survey Bulletin Vol.23, Art. 5 stomachs could often be identified by odor squirrels were never found at any appreci- or appearance. able distance from open water.

Some evidence is available that mul- Minerals berries, plums and other succulent fruits serve as water sources for Illinois fox The mineral requirements of squirrels squirrels. Robert E. Hesselschwerdt of are not well known. Little information the Illinois Natural History Survey did on the subject was gathered in this investi- not find that fox squirrels on the Urbana gation. As reported previously (Carlson Township Wildlife Area showed a ten- 1940, Coventry 1940), bones are eaten by dency to migrate during the extremely dry

Fig. 31.—Examples of squirrel "cutting" on nuts of the small pignut, Carya ovalis. The thin hull and shell of this species, in addition to the sweet-flavored meat, make it highly attractive to both fox and gray squirrels. both species of squirrels, perhaps for the summer and early fall of 1940, when all purpose of obtaining minerals. Baum- open water within 2 or 3 miles had dis- gartner (1939fl) reported that fox squir- appeared. During this period the squirrels eat soil to obtain mineral salts. Soil rels made free use of Osage orange fruits was found in small quantities in some of and of green corn and apples, from which the stomachs opened by the present writers. sufficient moisture may have been obtained. On the Mason County area, wild grapes, Water blackberries and wild plums probably supplied needed moisture during periods of

Water apparently is not a requirement drought. Other observers, including of the fox squirrel habitat, but it seems Allen (1943), have noted the ability of to be a necessity in the habitat of gray fox squirrels to survive on uplands far squirrels. The tracks of both species are from open water. Terrill (1941), work- often found in the mud or sand at the edge ing in Missouri, found that extreme of streams, ponds and lakes. It was not drought, resulting in the withering of determined in the present study how often succulent foods, tended to concentrate both squirrels drink, but observations on ani- fox and gray squirrels around ponds or mals and study of tracks indicated that other open water sources. _ during the warmer months gray squirrels, at least, take water daily. A comparison NESTING of typical habitats of the two Illinois species leads to the conclusion that the gray As has been reported by many writers, squirrel is more exacting in its water re- fox and gray squirrels throughout their quirements than its larger cousin. Gray range utilize both leaf and cavity nests. I September, 1945 Brown & Yeager: Squirrels ix Illinois 511

The degree to which they use each type is this region, a few bottoms, occasional determined, at least partly, by the kind woodlots and Osage orange hedgerows and age of the trees in an area. Squirrels supply the main tree cover. The hedges were sometimes found by the present writ- contain very few cavities, and Osage ers in young stands, in some cases where orange leaves are not well suited to nest cavities were very scarce; but the animals construction. Although both bottoms and were more common in older, cavity-con- woodlots of the black prairie region containing timber. There is no doubt of the tain numerous trees with cavities, the total superiority of the mature forest range, but acreage of such units is so small and their the fact that both fox and gray squirrels distribution so poor that great inadequacy built leaf nests even where cavities were of dens prevails in the region. In one present suggests that the highest quality Illinois study, Hesselschwerdt (1942) habitat must possess the possibility of both demonstrated that boxes made of lumber types of nest. The writers believe that serve very usefully in meeting the den either type of nest may supply the essential shortage in the fox squirrel habitat of the year around nesting requirements of either black prairie, fig. 32. Use of these boxes species. is discussed further in the section on "Management." Dens Many river bottoms and wooded upland areas, particularly in southern parts of the On the large expanse of Illinois black state, are well supplied with den trees. prairie, where only the fox squirrel is im- Most cutover areas, as a result of the des- portant, there is an acute shortage of tree tructive practice of cutting to smaller cavities suitable for denning purposes. In diameter limits, have been stripped of

big. 32.— Xesi box Miitahle tor sciiiinels in an Osage orange hedge, Champaign County, 1940. A screech owl is sitting in the entrance of the box. An acute shortage of tree cavities suitable for denning purposes exists on the Illinois black prairie. 512 Illinois Natural History Survey Bulletin Vol.23, Art. 5

«.« i^'--'^ 1

Fig. 33.—Den tree used by fox squirrels, Piatt County. Cavities are usually higher in trees than the cavity shown here. This den tree is included in the habitat illustrated in fig. 21. September, 1945 Brown & Yeager: Squirrels ik Illinois 513

trees with cavities. Selective cutting, es- (1943) found that fox squirrels used al- pecially if light, results in little harm to most any size or depth of hollow, some- squirrel range, either temporary or per- times stuffing with leaves those too large manent. for comfort. He also found that certain The best den trees in Illinois are the individuals may establish and use specific oaks, maples, American elm, white ash, dens for long periods, occasionally for the beech, sweet gum and, in extreme southern entire life of the animal. Four or i\vt Illinois, cypress and tupelo gum. The in- usable cavities per acre are probably ample herent soundness of such trees as Osage for any permanent squirrel population. orange, Cottonwood and the hickories, even The present writers found considerable when mature, eliminates them as impor- evidence that one squirrel, male or female, tant den producers. The oaks, partly be- may use concurrently two or more cavities cause of their abundance and state-wide or nest boxes. range, are easily the most important den- Of the protective value of cavity nests, tree group, fig. 33. Allen (1942) aptly states: 'Trom the The physical characteristics of cavities management standpoint, hollow trees are in relation to squirrel denning require- doubtless desirable even though squirrels ments were not studied h\ the present can live without them. They protect the writers. Baumgartner (1939/>') and Allen animals from hunters, natural enemies, (1942, 1943) reported in some detail on such as raccoons and owls, and severe this subject. Both writers found that weather." The present writers, in agree- squirrels maintain den entrances at a ment with Allen, have observed that good suitable size in growing trees by gnawing tree cavities afford, during storms and ex- the green cambium each year. Allen treme cold, a protection that may be

Fig. 34.—Typical fox squirrel leaf nest in oak, Cook County. (Photo by Gordon S. Pearsall. Vol.23, An. 5 514 Illinois Natural History Survey Bulletin

located Fig. 35.—Fox squirrel nest in white oak tree, Piatt County. Leaf nests may be crotches in almost any position or height in trees, but most commonly they are situated in branch near the central stem and at heights lower than shown here. September, 1945 Brown & Yeager: Squirrels in Illinois 515 largely responsible for high survival rates in construction materials, and position in of juveniles of and adults in winter. trees was observed in the present study. This variabilitv rendered classifving and Leaf Nests aging of nests so difficult that the writers were unable to use them as a satisfactory Late summer is the period of greatest means for censusing squirrels, although a nest-building activity in Illinois for both general correlation seemed to exist between fox and gray squirrels. Stoddard (1Q20) the number of nests and the size of the indicated that the fox squirrel in Indiana population. and Wisconsin constructs two types of leaf Squirrels in Illinois were found by the nests, a compact one used for young-rear- writers to exhibit no clearly defined choice ing, and a larger, more loosely constructed of tree species for nest building. Perhaps nest used as a summer retreat. Wide because they were the most abundant and variability in the size and shape of nests, widely distributed tree group, oaks con-

Fig. 36.—Box elder barked by fox squirrel, Ugie Lounty. (Photo by C. S. Walters.) 516 Illinois Natural History Survey Bulletin rol. 23, Art. 5 tained the largest number of nests. Oak "meat on the table." To thousands of leaves were the most widely used nest Illinois citizens, a "mess of young squir- material, partly because of abundance, but rels" is a delicacy annually looked forward represents also, the writers believe, because oak leaves to ; and to some the resource an and twigs are highly suited to the type of important and often needed food during construction found in squirrel nests, fig. the late summer and early fall, fig. 37. 34. Nests were found in every common Squirrel hunting tactics are very simple. Illinois tree species, including cypress and With experienced hunters, no form of Osage orange. In most cases they were hunting is more likely to result in game made from leaves of the host tree, but bagged, because an understanding of squir- other material also was used. Thus, nests rel habits practically insures success. If of tupelo gum leaves were found in cypress persistently hunted, however, both fox and trees. Crotches of larger limbs were the gray squirrels become wary, and under most common construction sites observed, such conditions stalking them requires a but there were many sites in forks, between considerable degree of skill. slender branches and, not uncommonly, Squirrel hunting, except when a dog is in the topmost branches of tall trees, fig. used, is primarily a stalking and waiting 35. Unlike the Bryant fox squirrel, as game. During the mast season, one of the reported by Dozier & Hall (1940), nei- most successful methods is for the hunter ther Illinois species was found to choose a to sit or stand quietly near hickory, walnut characteristic nest position in trees. or oak trees currently being "worked" by Ordinarily, the nests observed by the squirrels. Often hunters reach such feed- writers were not lined, but the inner leaves ing sites by daybreak and shoot the animals had become frayed and served as lining. as or soon after they emerge from nests Finely shredded bark was at times used for in the vicinity, or approach from outlying this purpose, and occasionally grass, fine territory. Under such conditions the roots, and even rags and paper had been killing of one squirrel does not result in utilized. Some individuals, particularly cessation of feeding by other squirrels for female fox squirrels, seemed to be addicted more than a short time, often only a few to the barking of trees, fig. 36, for the minutes. Indeed, limits of five squirrels purpose of obtaining nest material, and are often killed at a single site, and some- no doubt for other reasons. The use of times from a single tree. The writers bark in tree-cavity nests has been reported have several records of five squirrels killed previously (Yeager 1936). from one tree in the space of a few minutes. In such cases, the hunters shot the HUNTING feeding animals before they could escape into surrounding cover. It is not uncom- Material gathered during the course of mon for bags made under such conditions the present investigation included infor- to be composed of both fox and gray squir- mation on the method of hunting squirrels rels. in Illinois, on the annual kill and on crip- Stalking is a favorite method of hunting pling losses. when conditions permit. During dry periods, leaves and twigs are noisy when Hunters and Hunting Methods walked upon, making stalking difficult or impossible. When such conditions pre- In Illinois, no field sport except rabbit vail, hunters advance from point to point,

hunting is confined more to rural and remaining quietly for a time at each. small-town populations than that of squir- Points that offer a good view of the sur- rel hunting. Whereas waterfowl and up- rounding territory are usually selected. land bird shooting draws its devotees large- Thus, the end of a ridge, especially when ly from urban and professional groups, bordered by a narrow valley and with tim-

squirrel hunting is mainly the diversion of bered slopes beyond, offers a favorable farmers, laborers and local business men. waiting site. When quiet stalking is pos-

This is true particularly in the important sible, such as after a rain or early in the southern zone. The sport is highly prized morning, hunters walk slowly through the

by those who participate in it, both for its woods, either overland or along trails, recreational value and because it means pasture fences or dry creek beds, taking Sept ember 1945 Brown & Yeager: Squirrels in Illinois 517 advantage of all cover en route. This are most effective after the leaf fall, when method permits maximum coverage of squirrels can be easily seen. The 1944 hunting territory. A summary of hunt- season, closing November 15, October 30 ing success of 236 Illinois hunters in 1940 and October 15, in the northern, central and 1941 is given in table 23. and southern zones, respectively, when Dogs, which are not widel\ used in leaves were still on the trees, virtually squirrel hunting in Illinois, are perhaps eliminated the use of dogs in the soutiiern most in the common southern zone; they zone, and permitted only limited use in the

::J

Fig. 37.—A limit typical for central or southern Illinois—three gray and two fox squirrels. hiitguns are used by many Illinois s(juirrel hunters. . .

518 Illinois Natural History Survey Bulletin Vol 23, Art. 5

central and northern zones. It is said numbers, south to north, there is likewise that squirrel dogs were more widely used a decline in the number of squirrel hunt- in Illinois when the season closed later ers. This circumstance would make for than in 1944. more or less equal hunting pressure and The writers believe that the data pre- consequently success, as is indicated by the sented in table 23 are too few and selective data. to be accepted at their face value. There It is not known how accurately crip- is reason to suspect that they are based pling losses are indicated in table 23. On on returns made by the more successful the basis of the writers' observations and hunters. The strikingly uniform bag of the opinions of many experienced hunters, slightly more than one squirrel per hour the figures are conservative. The great- in all zones and for both years represents est source of error probably lies in the a very high index of hunting success. The number of animals hit but giving no indi- writers suspect that the true index of suc- cation to hunters of having been wounded. cess falls between 0.5 and 1.0 squirrel Such cases are not listed in the tabula- bagged per hour. tions. There is evidence based on skulls The uniformity in success per unit of and bones found in tree cavities that an effort in the three zones may be explained appreciable number of wounded squirrels by the relationship that exists between the reach their dens and die there. number of hunters and the number of The habit of shooting into leaf nests is squirrels in each zone. Just as there is a more or less common in Illinois. Allen progressive decline in the acreage of squir- (1940, 1943) in Michigan has shown this rel range, and consequently in squirrel to be a wasteful and altogether undesirable

Table 23.—Average number of squirrels bagged, hours of hunting, squirrels bagged per hour and crippling losses, as reported by 236 Illinois hunters, 1940 and 1941.

Cripples Not Bagged* Average Number (Per Cent of Total Number Known to Have Been OF Zone Hit) Hunters Squirrels Hours ot Squirrels Reporting Bagg&d Hunting Bagged per Hunter per Hunter Fox Gray per Hour per Year per Year Squirrel Squirrel

1940

Northern, 18 14.8 13.2 1.2 8.1 10.5 Central. 30 18.4 16.7 1.1 12.6 12.8 Southern 110 19.7 17.9 1.1 12.6 15.7

Total or Average 158 18.9 //./ 1.1 12.0 15A

1941

Northern Central .... September, 1945 Browx ^' Ye.ager: Squirrels ix Illinois 519 practice. He found that the majority of ':'. / leaf nests shot into did not harbor squirrels, and in instances where animals were present they usually did not jump from the nests if hit ; if they were killed, he believed they usualh' were not recovered. The types of guns used by Illinois squirrel hunters are indicated in table 24, which is based on 158 returned questionnaires. A carving, fig. 38, by an unknown individual is indicative of public interest in .squirrels.

Kill

Through the cooperation of the Illinois Department of Conservation, a good esti- mate of the 1942 squirrel kill in Illinois, based on hunters' kill return cards, is available. The total was 1,463,305 squirrels. A breakdown of the 1942 kill, as disclosed by the present investigation, is presented in table 25. We have no comparable data for 1940 and 1941, the hunting seasons principally represented in this study.

Table 24.—Types of firearms used by 158 Illinois squirrel hunters reporting in 1940.

Tv'i'E OF Firearm 520 Illinois Natural History Survey Bulletin Vol. 23, Art.5\

sent between 1 million and VA million Shrub-bordered woodlots or stands provide] pounds of edible game. variety in food resources, and the shrubs are of value in site protection. Logs and MANAGEMENT down treetops, or piled brush, have a certain, but unmeasured, attractiveness for Management of wildlife resources is squirrels, and their presence in the habitat basically the maintenance of various spe- adds to its quality. cies at any desired population level. To Slashing, wherein all commercial timber accomplish this objective, use is made of is ruthlessly cut and logged, may—and what is known of the life requirements of indeed often does—destroy completely a each species in question. Thus, in the field, woodland as a squirrel range. Such cut- pheasants may be provided with more ade- ting, followed by fire, may eliminate oc- quate winter cover, or quails with brush- cupancy even by fox squirrels for 10 to bramble thickets adjacent to food areas. 25 years. Likewise, the cutting of all If such changes plug the most serious en- defective trees, to which cavity dens are vironmental gaps confronting the species, largely confined, greatly reduces habitat only for squirrels but for the habitat is improved ; and, in the broad quality, not sense, further improvement is attained only other cavity-denning wildlife. Many de- when the next most serious gap has been fective trees are good mast producers. mended. It can be said that game habitats Release and improvement cuttings that are no better than their weakest environ- result in taking out all or most individuals mental factor, and that they usually may of such species as mulberry, black cherry, be improved up to the point where all wild plum, hawthorn and wild grape conditions are optimum, after which intra- make for food shortage during the spring specific tolerance, or lack of it, becomes the and summer. It has been observed that important factor in population density. one elm and one mulberry per acre in oak- Our present knowledge of squirrel ecol- hickory or beech-maple types may represent ogy, admittedly inadequate, permits some the difference between good, permanent general suggestions for managing fox and habitat and that which is deficient for gray squirrels in Illinois. squirrels during the spring and early summer months. The usefulness of mul- Habitat Improvement berry is noted by Goodrum (1938). Naturalness in forest stands, involving Among the more effective means of im- a reasonable variety of species, the presence proving squirrel habitats are maintaining of all age classes, including some defective, favorable food and den tree combinations cavity-containing trees, and an understory •through selective cutting and planting, of shrubs and young trees, insures a satis- maintaining hedgerows, providing den factory squirrel habitat in almost any part boxes, protecting against fire and grazing, of Illinois, fig. 39. and supplying feed in winter. Forest practices that result in leaving at Forestry Practices.—In that fox and least a few oaks, hickories and walnuts in gray squirrels are dependent on woodland, the stand are of the greatest importance in no factor can be more important in their maintaining the squirrel range. Of these husbandry than the woodland management three tree groups, the hickories, including policy. Fortunately, good forest practices the pecan, are, tree for tree, of the greatest generally lend themselves to good squirrel value to squirrels. Hickories are gen- management, especially in the case of fox erally considered of secondary commercial squirrels. In fact, a small amount of value for lumber, and a policy of favor- cutting improves large, unbroken stands ing them in forest practices creates a con-j as squirrel range, because the openings so flict of interests. However, where hickorj made promote the growth of food-produc- constitutes an appreciable part of the ing brambles and shrubs, and hence greater stand, as it does throughout much of the variety in both cover and food resources. oak-hickory type, it is not necessary tc Fox squirrels may respond to improve- save every hickory in maintaining gooc ments effected by selective cutting within squirrel range. Under -such circumstances^ a year or two; gray squirrels only after release and improvement cuttings mar appreciable shrub growth has appeared. well favor the commercially more valuable September, l'J45 Brown & Yeagkr: Squirrels in Illinois 521

oaks, walnuts and yellow poplar, reserving and timbered areas. Many of the scat- only a few hickories per acre. tered Osage orange trees occurring in Stand composition in high quality squir- Illinois pastures and woodlots are believed rel range must, however, consist of more to have originated in this manner. Squir- than acorn and nut species, notwithstand- rels are probably responsible for others.

Fig. 39.—Mixed hardwood stand, Piatt County. This forest type, common in Illinois, offers one of the best year around habitats for squirrels. ing the essential function of these groups Brambles, particularly blackberries and in producing food staples. Spring and raspberries, improve the food resources of summer food species are needed, since any squirrel habitat, as does adjacent corn. mast is not available until midsummer or Hedgerows and Fencerows.— In later. Highly important are buds and farm localities, or in an\' region where seeds of elms and maples, the first green woodland occupies only a small acreage, food of the \'ear; mulberries, which tend hedgerows and fencerows may constitute to replace buds and seeds in the diet in a very appreciable part of the squirrel May and which supply a staple food habitat (Whitaker 1939). Even in more con- throughout July ; and black cherries, wnld heavily wooded localities, hedgerows plums, serviceberries and similar fruits, all necting two woodlots or stands, or offering of which become available in summer. shelter along cornfields or bramble patches,

The mulberry is especially useful be- represent a valuable feature of the cause it not only offers an attractive food range. The most common black prairie during a food-deficient period, but is shade squirrel habitat is the Osage orange-corn- tolerant and grows and produces well un- soybean combination, supplemented in der a variety of site conditions. It appears some cases by food- and cavity-bearing to do best on moist, fertile, riverbottom walnuts, oaks and maples, usually near a soils. farmstead. Osage orange trees in woodlots or other Although of very low carrying capacity forested areas provide a good food re- for the total acreage involved, this type of source. Cattle ma\- eat Osage orange habitat is in some respects satisfactory for fruits during the winter and thus scatter fox squirrels, as is attested by the generally viable seeds in droppings over woodlots e.xcellent condition of animals collected in 522 Illinois Natural History Survey Bulletin Vol. 23, Art.

it. Removal of hedgerows, which has been extensive during recent years, has measurablj' reduced the acreage of habitable fox squirrel range in the state. Undoubtedly the best hedgerow cover for squirrels is offered by very large, un- trimmed Osage orange trees, but a hedge of this size lowers the crop yield for a distance of 20 or 30 feet on each side and

therefore is resented, with some justifi- cation, by many landowners. Smaller hedgerows are of material value to fox squirrels, and trimming, although it im- pairs, does not destroy their usefulness to squirrels. Fencerows of oaks, elms, maples, hickories or red cedars are commonly used by fox squirrels to the limit of food and cover offered. The value, to fox squirrels particularly, of one or a few good food trees in hedgerows, corners or in open stands is appreciable. The most desirable species for such situations are hickories, including pecans, walnuts and most oaks. They are well adapted to hedgerow planting, as they produce well when isolated and thus favored by full light. Den Boxes.—Den boxes, fig. 40, suit- boxes able for squirrels and other cavity nesting Fig. 40.—Two types of artificial den suitable for squirrels. A box having a mini- species have been tested extensively in mum cross section of 8X8 inches, at least 2 Illinois (Hawkins & Bellrose 1941, Hes- feet deep and with an entrance 3 inches in selschwerdt 1942, Yeager 1942, Brown & diameter, is recommended. Bellrose 1943) and in Michigan (Allen 1942, 1943). The outcome of these for 2 or 3 years or longer. Such boxes studies leaves little doubt of the possibility can be built and erected for a small sum

of substituting artificial for natural cavi- each ; if made of cypress or cedar lumber ties in regions where the latter are scarce that must be purchased as new, the cost or lacking. Den boxes appear to be es- will be higher. However, nests made of pecially useful on the black prairie, where the better material will give, with some the shortage of natural cavities is acute, repair, at least 10 years of service. Two and in food-producing forest stands too or three boxes per acre are ample, and they immature for cavity formation. should be placed in the larger trees, 20 Almost any covered box or keg having feet or more above ground. In order to an entrance hole and room for a nest will insure the most effective utilization, they be used by squirrels if placed in a tree on should not be placed in den trees, but in- their range. The box recommended here stead in sound trees some distance away is 2 feet deep, 8 by 8 inches inside cross from den trees. On large tracts, boxes section, and with an entrance hole 3 inches placed on or near the timber edge are more in diameter. It should have a removable attractive, at least to fox squirrels, than top to facilitate cleaning, which is oc- those 100 yards or more inside the stand.

casionally necessary because squirrels fill Where ample tree cavities already exist,

boxes with leaves and other materials. it is a waste of time and materials to in- Small cracks in the boxes do not seem to stall artificial dens, and for this reason interfere wnth use of the box by squirrels, their use in most all-age stands is unnec-

and a perch will be used if present but is essary. not necessary. Boxes constructed from Control of Fire and Grazing.—The nail kegs or sound old lumber will last burning and grazing of woodlands in Illi- September, 1945 Brown & Yeager: Squirrels in Illinois 523

nois is a common practice. About 10 able at all times. There is no evidence years ago, approximately 75 per cent of all pertaining to this state that fire is ever of timbered area in the state was grazed benefit in squirrel management.

(U. S. Department of Commerce 1935), Winter Feeding.— It is only during and an unknown, but appreciable, per- periods of heavy ice or actual food shortage centage is burned annually, especially in that winter feeding of squirrels in Illinois the south-central and southern counties. is recommended. Snow is of little hin- Both burning and grazing are injurious to drance to successful foraging, since both timber growth as well as to the site, as fox and gray squirrels dig readily through has been pointed out many times. a foot or more of snow to reach food, fig. Due to the arboreal nature of squirrels, 41. On the better oak-hickory range in fire and grazing are not so injurious to the state it is rare indeed that feeding is them as to ground-frequenting birds and necessary ; and, due to availability of waste certain other wildlife. In woodlots hav- corn left by mechanical pickers, it is needed ing very heavy ground cover, light grazing on the extensive black prairie type only may be of some benefit both to fox squir- during periods of heavy ice. rels (Allen 1941, 1943) and gray squir- If conditions warrant feeding, it is rels (Goodrum 1940). However, graz- recommended that ear corn, hickory nuts, ing of wooded land gives neither a good w^alnuts or unroasted peanuts be used. pasture nor a good woodlot, and sound Corn, because of its abundance, avail- land use decrees that stock be kept off ability and attractiveness to squirrels, is forested range. Very heavy grazing un- by far the most practical emergency food. doubtedly depletes the quality of squirrel Ears may be impaled on spikes driven up- habitats w^herever it occurs, since it results right through small poles or boards ; nuts in decreased food supply through the may be placed in trays or hoppers in such destruction of shrubs and brambles. This a manner as to prevent excessive scatter- practice, therefore, may easily result in ing. A corn shock near the woods border food shortage, or at least a shortage of makes a simple and effective feeder. Feed- certain attractive foods, during the months ing operations should be centered on the prior to the ripening of mast. best squirrel range, to take advantage of

Fire is actually and potentially so des- maximum cavity and natural food avail- tructive to Illinois woodlands that its sup- ability. Chapman & Baumgartner ( 1939) pression in these areas is considered desir- recommended one feeding station per 25

or more of snow in finding Osage Fig. 41.—Squirrels are capable of digging through a foot orange fruits or stored nuts or acorns. 524 Illinois Natural History Survey Bulletin Vol. 23, Art. acres of woodland. Hawkins (1937) es- sound open seasons on fox and gray squir- timated that individual squirrels consumed rels in Illinois. about 2 pounds of shelled corn per week. The Illinois squirrel season has always A practical feeding station is shown in begun early and lasted long, and the bag fig- ^2. limit has been liberal. Despite heavy . . Winter feeding projects are relatively hunting and extensive habitat depletion in easy to organize among sportsmen and con- the state, squirrels, particularly fox squir-^ servationists, but such activities are also rels, have maintained appreciable popula-

Fig. 42.—A practical winter feeding station—standing corn adjacent to a woodlot and hedgerow, Champaign County. m\ easy to neglect during severe weather. A tions. This circumstance attests eloquent- feeding program, if it is neglected during 1}' to high quality in much of the Illinois a critical period, especially after squirrels squirrel range. A comparison of the 1944 or other game have been concentrated by season in Illinois with seasons in other feeding during mild weather, may do more central states is given in table 26. harm than good to the animals. Of the midwest states, only Missouri and Kentucky, with 153-day and 84-day Hunting Seasons seasons, respectively, had longer open seasons than the central and northern The regulations under which squirrels zones in Illinois. Only Missouri had an are hunted are among the most important earlier season than the southern zone. factors in their management. One of the The daily bag limit in- the midwest states ultimate objectives of this study was the was rather uniform, table 26, and appar- determination of dates for biologically ently satisfactory. Only Michigan had a September, 1945 Brown & Yeager: Squirrels in Illinois 525 season limit on the kill, the total being 25. lactating females; and (3) many young It is interesting to note that long squirrels too immature to be self-sustaining seasons are, for the most part, in those die of starvation. states where the oak-hickory forest type From a biological standpoint, there is is most extensive. These forests, in the no real objection to a high percentage of central states, probably reach their best young squirrels in early-season bags. Ma- development in Missouri and Illinois. ture animals appear to be the more certain That this correlation of season with habi- winter-season breeders. From the stand- tat should occur is perhaps significant ; it point of the hunter, young squirrels rank appears to be an instance in which the law higher than old, as they are of maximum of supply and demand exerts a dominating tenderness and palatability, whereas influence on legislation governing the utili- breeding squirrels, particularly spent males zation of a wildlife resource. and lactating females, are relatively low Eflfect of Early Seasons.—The basic in these qualities. effects of early-season hunting may be The chief objection to early-season summarized as follows : ( 1 ) Approxi- hunting is that it results in the destruction mately 50 per cent of the kill is of first- of pregnant and lactating females ; the litter young; (2) the kill includes a pregnant animals involve unborn young, considerable portion of the pregnant and and many of the lactating females involve

Table 26.—Squirrel hunting seasons in midwest states, 1944. 526 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 young too immature to be self-providing. well as the squirrels fatally wounded and Cross (1942) found 100 per cent preg- not recovered, must be added to the kill nancy during the period September 1—15 in order to obtain the total theoretical loss. in a sample of 39 adult squirrel females in The net loss might be somewhat less due Virginia. to the fact that squirrels suffer some mor- The calculated degree of loss in unborn tality during the post-natal and juvenile and immature squirrels resulting from an periods. This loss, although not known, early hunting season in Illinois is given in is probably low, since the young are rela- table 27. The calculations in this table tively free from predation and usually are are from data given in tables 2, 3, 15 and well protected against the elements. 20. The dates of the period included in A calculation of the total loss of unborn table 27 (July 16-October 31) were and suckling young may be made by ap- chosen because they are a compromise plying the findings in table 27 to the total between the 1944 hunting seasons in the kill, which, as discussed under the heading central and southern zones, where most of "Kill," was calculated for 1942 at 1,463,- the squirrel kill was made and where 305 animals. The ratio of 31.8 young most of the data in tables 15 and 20 were lost for every 100 squirrels bagged applied gathered in the years of this study. Table to this kill figure gives 465,331 as the cal- 3 indicates that of each 100 squirrels culated number of young lost in an Illinois bagged during the period July 16—October season that begins early, July 16, and con- 31 (the kill during the period of Novem- tinues through October. ber 1-15 in the northern zone is negligible, Recommended Seasons.—The one while the kill during the period July 15^31 change needed in current Illinois laws to in the southern zone is appreciable), ap- provide a biologically sound squirrel hunt- proximately 70 per cent were fox squirrels ing season is a later opening date in each and 30 per cent were gray squirrels. In zone. In recommending this change, how- each 100 animals, there was an average of ever, the writers have not forgotten that 12.8 mature and therefore potentially early seasons are traditional in the state, breeding fox squirrel females and 7.7 po- and that there are thousands of hunters tentially breeding gray squirrel females who sincerely believe in summer squirrel (figures derived from table 15). Preg- hunting. That these hunters argue with nant among these mature females was an some logic is indicated by the fact that, average of 3.7 fox squirrels and 2.9 gray despite early hunting seasons in the past, squirrels, and lactating among them was in many parts of the state there is still an average of 3.7 fox squirrels and 2.4 good squirrel hunting. However, abun- gray squirrels. dance of squirrels in certain areas may be The average number of young per lit- the result of one or more of a number of ter during the second season, as determined conditions, some of them local, that favor in the Illinois study, was 2.57 in fox squir- squirrel survival. In some parts of the

rels and 2.43 in gray squirrels, table 20. state hunting is comparatively rare early

Calculations based on these data give, for in the season and is intensive only through each bag of 100 squirrels, a loss of 9.5 the peak of the mast season, roughly unborn young and 9.5 suckling young of August 15 to September 15. In many the fox squirrel, and 7.0 unborn young and places, late in the season, when squirrels 5.8 suckling young of the gray squirrel. are scarcer and the population becomes Only females showing unmistakable evi- scattered, interest in squirrel hunting de- dence of lactation were classified as lac- creases. In some agricultural communi- tating; additional losses in young may ties the fall farm harvest requires the at- have resulted through killing of mothers tention of a large number of potential in the last stages of lactation or those still hunters. In many counties, the advent exercising parental care over young. The of the dove, waterfowl and upland game losses in unborn and suckling young were seasons further reduces the number of

in addition to squirrels bagged and fatally squirrel hunters. It is probable that the hit by hunters in the period beginning July 76- to 93-day season in Illinois results 16 and ending October 31, table 23. in only a slightly larger kill than would For each 100 squirrels bagged, 31.8 a 45-day season coming during the unborn and suckling animals, table 27, as main mast season. However, a season be- .

September, 1945 Brown & Yeager: Squirrels in Illinois 527

27. Table —Calculated loss in unborn and suckling young per 100 squirrels bagged in Illinois, July 16-October 31, inclusive, 1940-1943. A kill ratio of approximately 70 fox squirrels to 30 gray squirrels was obtained from Illinois kill figures, table 3.

Number Per 100 Squirrels (70 Types of Loss bv Species Fox Squirrels, 30 Gray Squirrels)

Mature, potentially breeding, females (tabic 15j

Fox squirrels, 21 of 115 animals (tables 14 and 15; 18.3% of 70 animaisj 12 8 Gray squirrels, 16 of 62 animals (25.8% of 30 animals) 7,7

Pregnant (table 15) Fox squirrels, 6 of 21 mature females (28.6% of 12.8 mature females) .... 3.7 squirrels, of Gray 6 16 mature females (37.5% of 7.7 mature females) . . . 2.9

Lactating (table 15)

Fox squirrels, 6 of 21 mature females (28.6% of 12.8 mature females). . 3.7

Gray squirrels, 5 of 16 mature females (31.3% of 7.7 mature females). . 2.4

Unborn young* P'ox squirrels (3.7 x 2.57) 9.5 Gray squirrels (2.9 x 2.43) 7.0

Total unborn young 16.5

Suckling young* Fox squirrels (3.7 x 2.57) 9.5 Gray squirrels i2.4 x 2.43) 5.8

Total suckling young. 15.3

Tolij/ loss

^Average size of second-season litters: fox squirrels, 2.57; gray squirrels, 2.43; table 20. ginning later than the present one would of many thousands of squirrels that are not result in the survival of a much greater bagged. We suggest as a reasonable com- number of unborn and suckling squirrels promise the seasons given in table 28, that now are lost through destruction of which takes into consideration the prece- pregnant and lactating females. dent for early hunting in the state, the In the face of the considerations listed minimum requirements for adequate re- above, we feel that it would be unwise to production, and the high productive ca- enact a squirrel season beginning ifo late pacity of much of the Illinois squirrel

that it would prevent all losses attribut- range. able to the killing of pregnant and lactating It goes without sa>ing that, although females. Such a season could hardl}' be- the seasons proposed here will result in ap- gin earlier than October 1, and it would preciable loss due to starvation of young, certainly be opposed by a large number this loss will be materially less than at of hunters. On the other hand, it is present. In time it may be practical to clear that the 1944 season, opening July enact laws establishing seasons that give 15 in the southern zone and August 15 in squirrels greater protection in order still the central and northern zones, is too early, further to reduce juvenile losses. It is and that such a season results in the death not out of place to point out that seasons 528 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

Table 28.—Recommended squirrel hunting seasons in Illinois.

Zone September, 1945 Brown & Yeager: Squirrels in Illinois 529

tionnaire. The writers endorse the limit The ratio varied by zones; being 86.1 fox i of five squirrels per hunter per da). squirrels to 13.9 gray squirrels in the northern zone, 87.4 to 12.6 in the central SUMMARY zone and 49.5 to 50.5 in the southern zone. Species ratios based on other source data 1. This investigation (Illinois Federal and for other years differ somewhat, and Aid Project 14-R) was initiated in fur- indicate that gray squirrels may constitute therance of biologically sound squirrel as much as 35 per cent of the squirrel hunting seasons and progressive squirrel population of this state. management in Illinois. 7. Sex ratios (based mainly on hunt- 2. Field work covered a 4-year period ; ers' kill in 1940 and 1941 and to a small the first 2 years, beginning July 1, 1940, extent on litters and live- and steel-trapped

: were given to a full-time study and the animals) showed a preponderance of males last to part-time study. i 2 years During in both species. The ratio was 143 males the first year, 10 days per month were to 100 females in fox squirrels and 144 spent by the senior author in each of the males to 100 females in gray squirrels. three zones into which the state is divided The actual sex ratios are believed to be for administration of hunting laws; dur- more nearly equal than these figures indi-

; ing the second year, intensive local study cate.

, was pursued by the same author in Pike 8. The best criteria of maturit\ in

County, in the central zone, and in other males (November—July ) are Cow'per's I representative areas inhabited by both fox glands of one-half inch or more in diam- j

' and gray squirrels. Part-time field work, eter and enlarged testes with scrotum de- by the junior author, was carried on void of hair (or nearly so) on entire ven-

mainly in the central zone. tral surface ; for females, large, dark and 3. No completely satisfactory census protruding nipples. Immature males technique was developed. The need for have undeveloped Cowper's glands even such is obvious. Time-area counts of during the mating season and only the animals and nest counts probably give a posterior end of the scrotum devoid of

' rough census. Exhaustive live trapping hair ; immature females have mammae supplies reliable population numbers, but with small nipples nearly hidden by hair.

is too slow and time-consuming for wide- 9. Age class figures for Illinois fox scale use. squirrels, as indicated by several hundred 4. The western fox squirrel (Sciurus animals shot and trapped by the writers, uitjer rufivetiter) inhabits most wooded were as follows: 57.8 per cent adults, 26.7 areas, including small woodlots and hedge- per cent spring juveniles and 15.5 per cent rows, in every Illinois county. The gray summer juveniles; for gray squirrels the squirrel {S. carolinensis leucotis and/or figures were, respectively, 65.4, 22.4 and

5. c. carolinensis) occurs in all Illinois 12.2 per cent. The comparatively low counties except some on the black prairie. kill of summer juveniles is undoubtedly an

It is confined to dense forest stands and is important factor in maintaining s(]uirrel most numerous in those with brushy under- populations. story bluffs bottoms areas, 10. Little or no competition between , in the river and red squirrel {Tamiasciurus hudson- fox and gray squirrels was observed. j The in Illinois by 11. Both species were most active early \ icus loquax) was not found the writers. in the morning, the hour of greatest ac- I 5. Fox squirrel density in the areas tivity being from 6 : 00 to 7 : 00. The I studied varied from 0.02 to 2.23 animals greatest activity hour for the afternoon I per acre. Gray squirrel density, on one was, in fox squirrels, between 4 : 00 and j

squirrels, between 5 : 00 and representative area, w-as 1.49 per acre; 5 : 00 ; in gray the combined density of both species in 6:00. The fox squirrel showed the this area was 2.34 per acre. An average greater tendency to be active during inid- of about one squirrel per acre on good day hours; the gray was active later in likely. the evening. Individuals of both species j Illinois habitat appears active during showers, or I 6. Species ratio (based on hunters' were seen to be

; in both spe- ' kill in the 1940 and 1941 seasons) was soon after, and in deep snow 69.7 fox squirrels and 30.3 gray squirrels. cies, high winds, heavy rains, snow- ,

530 Illinois Natural History Survey Bulletin Vol 23, Art. 5 storms, very high temperatures and also of both species were available each month very low temperatures appeared to reduce from July, 1940, to October, 1942. activity. Other biological and all ecological studies 12. The two types of movements noted were based on these animals, an additional in squirrel populations were daily activity, 2,594 fox squirrels and 1,121 gray squir- mainly associated with feeding, and sea- rels taken mainly by hunters, and more sonal dispersal, perhaps associated with the than 2 years of field observations. annual readjustment of populations, in 19. Both fox and gray squirrels have the late summer and fall. The former two breeding seasons per year, the first in usually involved only a few acres ; the winter and spring and the second in spring latter, probably up to several miles. Mass and summer. Second-season litters appear migration was not observed in either to be confined largely to vigorous females species although it has been reported often over 18 months old. Both spring-born in the gray squirrel. and summer-born animals attain sexual 13. Neither weight nor length of maturity at the age of about 10 to 12 squirrels proved to be a reliable indicator months, and the females produce their of age at all seasons of the year. Adult first young when approximately a year old. fox squirrels taken in a 2-year period av- 20. In Illinois the breeding season of eraged about 1.70 pounds; adult grays, fox squirrels precedes that of gray squir- 1.18 pounds. Spring-born juvenile fox rels by about 10 days or 2 weeks. Be- squirrels weighed 1.61 pounds by No- tween the northern and southern limits of vember; spring-born juvenile gray squir- Illinois there is a difference of about 3 rels, 1.27 pounds by October. Length weeks in the average breeding dates for was found to be probably an even less both species. In the central zone, the reliable age indicator than weight. peak of winter breeding determined for

14. Stub tail was the only deformity fox squirrels was in late December ; in observed; 13.5 per cent of all fox squirrels gray squirrels in early January; summer and 12.3 per cent of all gray squirrels ex- breeding peaks, for fox squirrels, the amined were affected. This deformity, first 2 or 3 weeks in June; for gray squir- probably due to fighting and mating rels, the last half of June or a little later. chases, in no way impeded travel or other Corresponding peaks may be expected ap- activity. proximately a week earlier and later, re- 15. Only six of the squirrels collected spectively, in the southern and northern showed wounds of serious nature. Most zones. badly wounded animals that escape hunters 21. Mating chases, often involving,

are believed to die in dens, nests or other several squirrels, are characteristic of both I retreats. species. In males, enlarged testes and 16. Fox and gray squirrels molt once Cowper's glands are obvious indications' annually, both species undergoing a body of breeding condition, and the scrotal sacn and then a tail phase. Males and spring becomes smooth and stained as the breed-1 juveniles molt before females, usually being season advances. In females, oestrus i fore midsummer. Females that produce is indicated by the swollen and discolored second-season litters molt last, beginning vulva. after lactation is under way. Few color 22. In both species gestation appears types were found in Illinois squirrels. to require about 44 or 45 days. In the 17. Neither parasites nor diseases ap- fox squirrel, pregnancy peaks occurred in peared to be of importance in Illinois early February and late July; lactation squirrel populations. Mange, the most peaks in March and August. In the gray

prevalent disorder, was observed in only squirrel, corresponding peaks were about ^ two localities (cities excepted), neither 10 days to 2 weeks later. Lactation in' serious. Predators likewise appeared to the gray squirrel extended into October. cause little loss; adult squirrels are too 23. Squirrels are born both in tree active and alert, and the young are too cavities and in leaf nests, more commonly well protected to be captured easily. in the former. The average number of 18. Breeding studies were based main- young in the litters counted was, in fox ly on 722 fox squirrels and 353 gray squir- squirrels, 2.49 in spring and 2.57 in rels handled in the laboratory. Specimens summer; in gray squirrels, 2.74 in spring September, 1945 Brown & Yeager: Squirrels in Illinois 531 and 2.43 in summer. The eyes of juve- 29. The gnawing of bones, observed nile squirrels open at about 4 weeks; in both squirrel species, may be for the weaning occurs at about 8 to 10 weeks, at purpose of obtaining minerals. which time the hair is well developed. 30. Fox squirrels apparently are able Young squirrels become fully self-sustain- to inhabit range lacking open water, pro- ing when between 3 and 4 months old. vided succulent foods such as green corn, 24. Illinois squirrel habitats are of blackberries or Osage orange fruits are two types, agricultural and woodland. available. Gray squirrels were never The former consist mainly of farm wood- found on areas entirely devoid of open lots, hedgerows and wooded stream water. valleys ; the latter, the more extensive 31. Both fox and gray squirrels use wooded areas, both upland and bottom- cavity and leaf nests, and in both species land in character. The upland and cavities are important as young-rearing bottomland types combined provide rough- sites. Either type of nest appears to meet ly 6,750,000 acres of squirrel range in the the essential requirements of either species, state ; agricultural types provide a much but both types of nests are found in the smaller acreage of habitable range. habitats of highest quality. Squirrels Minor habitat types consist of reforested utilize practically any kind of tree stripmines, estates, parks, college campuses, for nest location, but, because of abun- and many towns and cities. dance and statewide distribution, the oaks 25. During this investigation, a total are by far the most important group. of 76 kinds of food plants for Illinois The oaks, maples, American elm, white squirrels were recorded; these included 56 ash, beech, sweet gum, and, in extreme trees and shrubs, 2 vines, 4 brambles, 6 southern counties, cypress and tupelo gum wild herbs, 7 cultivated crops and various are the chief sources of nest cavities for fungi. Six groups provided most of the Illinois squirrels. staple foods—-hickories (including pecan), 32. Squirrel hunters are mainly farm- oaks, walnuts, elms, mulberry and field ers, laborers and small-town businessmen. corn. In Illinois almost any fruit may be Slightly more than one squirrel killed per important seasonally or locally. Mixed hour was reported by a group of 236 Illi- stands produce the greatest variety and nois hunters in 1940 and 1941. A bag abundance of food. Cultivated crops, figure believed to be more nearly represen- mainly corn, are of far greater importance tative for Illinois is between 0.5 and 1.0 to fox squirrels than to gray squirrels. squirrel per hour. Crippling loss, calcu- No study of the animal food of squirrels lated from hunters' reports, was about 15 was made. Squirrel food shortage ap- per cent of all squirrels known to have peared to be rare on Illinois range. been hit; this figure does not take into 26. Illinois squirrels follow a some- account the loss in squirrels not known to what distinct order of succession in the have been hit. The 12-gauge shotgun utilization of foods. In late winter or was the most popular arm of Illinois spring they feed on the buds and then the hunters, followed by the .22-caliber riHc flowers and seeds of elms, maples and other and the 16-gauge shotgun. hardwoods. Later they make use of mul- 33. The calculated squirrel kill in berries and bramble fruits. The mast Illinois in 1942 was 1,463,305 animals, of season, from July or August through Oc- which 64.7 per cent were fox squirrels and tober, is the period of greatest food abun- 35.3 per cent were gray squirrels. The dance. northern zone produced 11.4 per cent, the 27. Squirrels show definite preferences central zone 29.1 per cent and the southern when several foods are abundant at one zone 50.5 per cent of this kill. A total time. Hickory nuts seem to rank first of about 1,240,000 pounds of high quality with both fox and gray squirrels. meat was produced, practically all of 28. Storing or caching, which seems which was used for human food. to be instinctive in squirrels, is apparently 34. In general, good forest practices, an extension of the morning and afternoon especially the maintenance of mixed, all- feeding periods during the mast season. age stands and protection from fire and The stored foods observed in the present grazing, lend themselves to good squirrel study were mainly nuts and acorns. management. Selective cutting, except 532 Illinois Natural History Survey Bulletin Vol. 23, Art. 5 when a large percentage of the food trees more. Such a season may result in a cal- are removed, may improve the range as culated loss of 31.8 unborn and suckling squirrel habitat by breaking up solid squirrels for each 100 squirrels bagged, stands and promoting shrub, vine and or a total yearly loss of approximately bramble growth in the openings. Only 465,000 unborn and suckling squirrels a few hickories, elms or mulberries, in ad- (hunters' kill, 1942, used as a basis). dition to oaks, beech or maples, are needed 36. The squirrel hunting season re- in a stand to provide all necessary squirrel commended for Illinois is September 15 food. Development of fencerows and to November 15 in the northern and hedgerows greatly improves fox squirrel central zones, and September 1 to October range on the prairie. Den boxes are need- 31 in the southern zone. This season will ed only where cavity shortage actually not prevent all loss in unborn and nursing exists. Winter feeding is unnecessary squirrels, but will materially reduce the except during periods of crusted snow, losses now occurring. Recent severe de- heavy ice or actual food shortage. pletion of the habitat, due to heavy cutting 35. The Illinois squirrel hunting to meet war needs, is an added reason for season is traditionally long and is early in a hunting season based upon serious con- starting; in the past it has usually opened sideration of the life history of the in midsummer and continued 75 days or animals. LITERATURE CITED

Allen, Durward L. 1910. A point on fox squirrel management: Shooting into nests is wasteful hunting. Mich

Cons. 9(12) : 11. 1 fig. 1941. Rose Lake Wildlife Experiment Station; Second aiuuial report. Mich. Dept. Cons. Game Div. 365 pp. (Mimeographed.) 1942. Populations and habits of the fox squirrel in Allegan County, Michigan. Am. Midland

Nat. 27(2) : 338-79. 19 figs. 1943. Michigan fox squirrel management. Mich. Dept. Cons. Game Div. Pub. 100. 404 pp.,

152 figf , index.

Anderson, R. M. 1932. Methods of collecting and preserving vertebrate animals. Can. Natl. Mus. Bui. 69. 141 pp., 46 figs.

Baker, Rollin H. 1944. An ecological study of tree s(iuirrels in eastern Texas. Jour. Mammal. 25 ( 1 ) : 8—24. 5 figs.

Baumgartner, Luther L.

1938. Population studies of the fox squirrel in Ohio. N. Am. Wildlife Conf. Trans. 3, 1937:685-9.

1939rt. Foods of the fox squirrel in Ohio. N. Am. Wildlife Conf. Trans. 4, 1938:579-84.

1939//. Fox squirrel dens. Jour. Mammal. 20(4) : 456— 65. 3 pis. 1940. Trapping, handling, and marking fox squirrels. Jour. Wildlife Mgt. 4(4):444— SO.

1 pi., 16 figs.

1943fl. Fox squirrels in Ohio. Jour. Wildlife Mgt. 7(2) : 193-202. 1 pi.

1943/a Pelage studies of fox squirrel (Sciurus niger rufiventer) . Am. Midland Nat. 29(3): 588-90.

Boulware, Jean T. 1941. Eucalyptus tree utilized by fox squirrel in California. Am. Midland Nat. 26(3): 696-7. 1 fig.

Brooks, Fred E.

1922. Note on a feeding habit of the gray squirrel. Jour. Mammal. 4(4) : 257—8.

Brown, Louis G., and Frank C. Bellrose, Jr. 1943. l^se of nesting boxes for wood ducks by other wildlife. Jour. Wildlife Mgt.

7(3) : 298-306. 1 pi.

Cahalane, Victor H. 1942. Caching and recovery of food by the western fox squirrel. Jour. Wildlife Mgt.

6(4) : 338-52.

Carlson, A. J.

n. s. 1940. Eating of bone by the pregnant and lactating gray squirrel. Sci. 9! (2372) : 573.

Case, H. C. M., and K. H. Myers 1934. Types of farming in Illinois. III. Ag. Exp. Sta. Bui. 403. 226 pp., 40 figs.

Chandler, Asa C. figs. 1942. Helminths of tree squirrels in southeast Texas. Jour. Parasitol. 28(2) : 135-40. 3

Chapman, Floyd B. 1936. Fox squirrels and gray squirrels. Ohio Div. Cons. Bui. 127. 4 pp. (Mimeographed.) 1937. Controlled squirrel and rabbit hunting on state hunting preserves, 1936. Ohio Wild- life Res. Sta. Release 37. 11pp. (Mimeographed.) Ohio Wildlife. Res. Sta. 1938rt. Controlled squirrel hunting on Ohio hunting preserves, 1937. Release 68. 8 pp. (Mimeographed.) Trans. \9ZU. Summary of the Ohio gray squirrel investigation. N. Am. Wildlife Conf. 3, 1937:677-84. southeastern Ohio. U. S. Dept. Ag. 1939. A summary of the gray squirrel investigation in Wildlife Res. and Mgt. Leaf. BS-134. 9 pp. (Mimeographed.) [533] 534 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

Chapman, Floyd B., and Luther L. Baumgartner [1939.] Winter feeding of squirrels. Ohio Div. Cons. Bui. 150. 7 pp., 1 pi.

Cottam, Clarence

1941. How fast can a fox squirrel run? Jour. Mammal. 22(3) : 323.

Coventry, A. F.

1940. The eating of bone by squirrels. Sci. n. s. 92(2380) : 128.

Cross, R. H., Jr. [1942.] Breeding habits and management of the gray squirrel in Virginia. Va. Comm. Game and Inland Fish. 5 pp. (Mimeographed.)

Dambach, Charles A.

1942. Gray squirrel feeding on Crataegus. Jour. Mammal. 23(3) : 337.

Davis, Wni. T.

1907. Insects as the food of squirrels. Can. Ent. 39(1) : 16.

1924. Oak apple galls destroyed by gray squirrels. Brooklyn Ent. Soc. Bui. 19(3) : 91—3. 1 fig.

Deuber, Carl G. 1934. Defoliation activities of gray squirrels in American elm trees. Sci. Monthly 38: 60—3. lUus.

Dice, Lee R.

1931. Methods of indicating abundance of mammals. Jour. Mammal. 12(4) : 376— 81.

1941. Methods for estimating populations of animals. Jour. Wildlife Mgt. 5(4) : 398—407.

Dozier, Herbert L., and Harrold E. Hall 1944. Observations on the Bryant fox squirrel. Md. Cons. 21(1) :2— 6. lllus.

Edminster, Frank C. 1937. An analysis of the value of refuges for cyclic game species. Jour. Wildlife Mgt. 1(1-2): 37-41.

Goodrum, Phil D,

1938. Squirrel management in east Texas. N. Am. Wildlife Conf. Trans. 3, 1937:670—6. 1940. A population study of the gray squirrel in eastern Texas. Tex. Ag. Exp. Sta. Bui. 591. 34 pp., 5 figs.

Goodwin, George G.

1934. The gray squirrel migration. Nat. Mag. 23(5) : 221—2, 255— 6. 2 photos.

Graham, Edward, and Jacob Uhrich 1943. Animal parasites of the fox squirrel, Sciuriis n'lger rufiventer, in southeastern Kansas.

Jour. Parasitol. 29(2) : 159-60.

Hahn, W. L. 1909. The mammals of Indiana. Ind. Dept. Geol. and Nat. Res. Ann. Rep. 33: 417— 654.

Hamilton, W. J., Jr.

1943. Caterpillars as food of the gray squirrel. Jour. Mammal. 24(1) : 104.

Harkema, Reinard

1936. The parasites of some North Carolina rodents. Ecol. Mono. 6(2) : 153—232.

Hawkins, Arthur S.

1937. Winter feeding at Faville Grove, 1935-36. Am. Midland Nat. 18(3) : 417-25.

Hawkins, Arthur S., and Frank C. Bellrose, Jr.

1941. Wood duck habitat management in Illinois. N. Am. Wildlife Conf. Trans. 5, 1940:392-95. September, 1945 Brown & Yeager: Squirrels in Illinois 535

Haymond, Rufus 1869. Mammals found in Franklin County, Indiana. Ind. Ag. and Geol. Rep. 1869: 203—8.

Hesselschwerdt, Robert E. 1942. Use of den boxes in wildlife restoration in intensively farmed areas. Jour. Wildlife

Mgt. 6(1) : 31-7. 4 pis.

Hibbard, Claude W. 1935. Breeding seasons of gray squirrel flying and squirrel. Jour. Mammal. 16(4) : 325-6.

Hicks, Ellis A.

1942. Some major factors affecting the use of two inventory methods applicable to the western fox squirrel, Sciurus niger rufiventer (Geoffroy). Iowa State Col. Jour. Sci.

16(2) : 299-305.

Hungerford, K. E., and N. G. Wilder Observations on the homing ^ 1941. behavior of the gray squirrel {Sciurus carolinensis) . Jour.

Wildlife Mgt. 5(4) : 558-60.

Jackson, H. H. T. distribution of certain 1910. The Wisconsin mammals. Wis. Nat. Hist. Soc. Kul. 8(2) : 86—90.

1921. A recent migration of the gray squirrel in Wisconsin. Jour. Mammal. 2(2) : 113—4.

Katz, Julius S. 1939. An annotated bibliography of references concerning parasites of squirrels (family Sciuridae). Ohio Wildlife Res. Sta. Release 131. 21pp. (Mimeographed.)

Kennicott, John

1857. The quadrupeds of Illinois, injurious and beneficial to the farmer. U. S. Pat. Off. Rep. Ag. for 1856, pp. 54-67.

Leopold, Aldo 1933. Game management. Charles Scribner's Sons, New York, xxil 481 pp., 35 figs.

Lyon, M. W., Jr. 1936. Mammals of Indiana. Am. Midland Nat. 17(1): 1-384. 112 figs.

Middleton, A. D. 1930. The ecology of the American gray squirrel (Sciurus carolinensis Gmelin) in the British

Isles. London Zool. Soc. Proc, pt. 3, 1930: 809-43. 4 figs., 6 pis.

Mossman, H. W., John W. Lawlah and J. A. Bradley

Aiiat. ( ) : 89— pis., 1932. The male reproductive tract of the Sciuridae. Am. Jour. 51 1 155. 7 16 figs.

Necker, Walter L., and Donald M. Hatfield figs. 1941. Mammals of Illinois. Chicago Acad. Sci. Bui. 6(3) : 17-60. 15

Nichols, John T. 55-7. 1927. Notes on the food of the gray squirrel. Jour. Mammal. 8(1) :

Osgood, Frederick L., Jr.

1938. The mammals of Vermont. Jour. Mammal. 19(4) : 435-41.

Pearce, John 1938. Identifying tooth marks of some northeastern animals on forest vegetation. N. Am Wildlife Conf. Trans. 3, 1937:690-4.

Seton, Ernest T. 82-106. Illus. 1928. Lives of game animals. Literary Guild of Am., Inc., New York. 4: 9-S8 ;

Stoddard, H. L. 122— pi. 1920. Nests of the western fox squirrel. Jour. Mammal. 1 (3) : 3. 1 536 Illinois Natural History Survey Bulletin Vol. 23, Art. 5

U. S. Department of Commerce 1936. United States Census of Agriculture: 1935. Vol.1, xxxix+950 pp.

Terres, J. Kenneth 1939. Gray squirrel utilization of elm. Jour. Wildlife Mgt. 3(4): 358— 9.

Terrill, H. V. 1941. A preliminary study of the western fox squirrel, Sciurus niger rufiventer (Geoffroy), in Missouri. Graduate thesis, University of Missouri. 164 pp.

Whitaker, H. L.

1939. Fox squirrel utilization of Osage orange in Kansas. Jour. Wildlife Mgt. 3(2) : 117. 1 pi.

Woods, Gordon T.

1941. Mid-summer food of gray squirrels. Jour. Mammal. 22(3) : 321.

Yeager, Lee E. 1936. Fox squirrel seriously damages elm tree. Jour. Mammal. 17(4): 417— 8. 1942. Coal-stripped land as a mammal habitat, with special reference to fur animals. Am. Midland Nat. 27(3): 613-35. 8 figs.

Yeatter, Ralph E., and David H. Thompson 1943. Cottontails, tularemia and weather. 111. Cons. 8(4): 6—7, 36. Illus. INDEX

The following index covers Articles 2, 3, 4, and 5 of Volume 23 of the Illinois Natural History Survey Bulletin. An index of Article 1, T/ic Caddis Flies, or Triclioptcra, of Illinois, by Herbert H. Ross, begins on page 313 of this volume.

Arrowhead, 377 Ascarid, 472 Abies, wetwood of, 407 Ascaris, 472 Acer lumbricoides, 472

negundo, 499 ; sec also Box elder Ash, 504 ; see also specific references

rubrum, 498 ; see also Red maple Asimina triloba, 500 saccharinum, 498 498 see also Sugar maple sacchantm, ; B Acorn, 489, 492, 493, 496, 503, 505, 507, 508, 509, 521 Bacteria Acorn weevil, 503 Erwinia, 446 Aesculus glabra, 499 nimipressuralis, 423, 429, 430, 433, 439, Agaricaceae, 501 444, 445, 446 Aix sponsa {see also Wood duck) salicis, 422, 444 kill, 362 Micrococcus dendroportlios, 408 Algae, 377 Phytomonas tumefaciens, 439 Altcrnaria, 444 Pseudomonas lignicola, 422, 423, 444 Amriuriis Bag limit; see Duck, Squirrel jnrlas mclas, 399—400; see also Black bull- Baiting; see Duck head Balaninus, 503 natalis natalis, 399—400; see also Yellow Baldpate {see also Widgeon) bullhead kill, 362

Amelanchier canadensis, 500 ; see also Service- Banding; see Duck berry Bass; see Largemouth bass, Warmouth bass. American elm Yellow bass dieback, 423 Basswood, 499 flux, 423 Beech, 499, 504, 505, 513, 520, 531, 532 leaf drop, 423 Big Muddy River, 492 malachite green tests, 441 Big shellbark, 498, 505 pH range of soil for, 443 Birch, slime flux of, 408 squirrel use of, 498, 513, 531 Bitternut, 498, 505 wetwood, 408, 423, 445 Bittersweet, 493, 500, 503 bacterial isolations, 418, 424 Black bullhead {sec also Bullheads) inoculations, 423 in Onized Lake patch grafting, 423 age, 403 wilt, 407, 417, 423 census (catch, yield), 380, 381, 382, 383, toxicity tests for, 426, 427, 429 399, 404, 406 American golden-eye, 362; see also Golden-eye weight, 380, 381, 382, 383, 399

American lotus, 377, 505 ; see also Lotus Black cherry, 499, 520, 521 ; see also Wild Ampliibolips confluens, 503 cherry Anacharis canadensis, 377 Black crappie, 388-92; see also Crappie Anas in Norris Reservoir platyrhynclios platyrhynchos {see also growth, 390, 392 Mallard) length, 392 kill, 362 in Onized Lake rubripes {see also Black duck) age, 389, 403 kill, 362 census (catch, yield), 380, 381, 382, 383, Anoplura, 472 384, 388, 389, 391, 404, 406 Apple growth, 389, 390, 392 slime flux of, 408 length, 383, 388, 389, 390, 391, 392 as squirrel food, 500, 504, 507, 510 weight, 380, 381, 382, 383 Aquatic plants; see specific references in Reelfoot Lake, growth, 390, 392

Arctium lappa, 501 ; see also Burdock in Tennessee, length, 392 Arkansas, wood duck in, 363 Black duck {see also Black Mallard) Armadillos, 472 banding, 334, 369, 370 [537] — — —

538 Illinois Natural History Survey Bulletin Volume 23

Black duck continued Bluegill continued chronology of flight, 344, 355 in Onized Lake continued feeding habits, 337, 356, 358, 368, 371 length, 383, 392, 393 flocking habits, 337, 355 weight, 380, 381, 382, 383, 392 kill, 354, 358, 362, 366, 367, 369, 370 in Pistakee Lake laws relating to, 354, 355, 356, 358, 371 growth, 394 mortality quotient, 339, 343, 344, 345 length, 394 population, 356, 368, 369 in Senachwine Lake density, influence of, 3 54 growth, 394 shooting pressure, 344, 345, 354, 355, 367 length, 394 quotient, 339, 345 Bluegrass, 501 vulnerability, 337, 354 Blunt-nosed minnow in Onized Lake quotient, 339, 370 age, 403 Black gum, 499 census (catch, yield), 382, 383, 402, 406 Black locust, 499 weight, 383 Black mallard {see also Black duck) Box elder, 499, 504 kill, 351, 362 British Columbia, wood duck in, 363 Black oak, 455, 495, 498, 503, 504, 505, 507, 508 Bryant fox squirrel, 516 Black walnut, 498, 503, 506, 507 Buckeye, 499 Blackberry, 497, 500, 510, 521, 531 Buckwheat; sec Climbing buckwheat Blackjack {see also Ring-necked duck) Bufilehead, 362 kill, 351, 362 laws relating to, 332, 333, 361, 371 vulnerability, 340 shooting pressure on, 361

Blue-winged teal ; see also Teal Bullfrog, 377 banding, 361 Bullheads, 399-400; see also Black bullhead. chronology of flight, 341, 342, 3 55 Yellow bullhead feeding habits, 338 effect on largemouth bass, 385 flocking habits, 338 in Onized Lake kill, 351, 354, 362, 366 age, 399 laws relating to, 332, 355, 370 census (catch, yield), 380, 399, 400 mortality quotient, 339, 343, 344, 345 length, 383, 399, 400 population density, influence of, 351, 354 weight, 380, 399 shooting pressure quotient, 339, 341, 342, 345 Bur oak, 498, 505 vulnerability, 338, 340, 355, 370 Burdock, 501, 505 quotient, 339 Butterball {see also Ruddy duck) Bluebill {see also Lesser scaup) kill, 351, 362 flocking habits, 339 Butternut, 498 kill, 351, 362 vulnerability, 337, 339, 340 Bluegill, 392-5 in Chautauqua Lake Cache River, 492 growth, 394 California, waterfowl hunting regulations in. length, 394 331 in Fork Lake Can {see also Canvasback) growth, 394, 395 kill, 362 length, 394 Canada, waterfowl hunting regulations in, stocking, 395 327, 328 in Grass Lake Canvasback

growth, 394 chronology of flight, 3 55 length, 394 • feeding habits, 339, 340 in Horse Shoe Lake flocking habits, 339 growth, 394 kill, 351, 361, 362, 366 length, 394 laws relating to, 332, 355, 361, 368, 371 in Illinois mortality quotient, 339, 343, 344, 345 growth, 395 shooting pressure, 355, 361 length, 395 quotient, 339, 345, 361 in Onized Lake vulnerability, 339, 370 age, 392, 403 quotient, 339 census (catch, yield), 380, 381, 382, 383, Carp 384, 392, 393, 394, 404, 406 eff^ect on largemouth bass, 385 death of, 381 in Onized Lake growth, 392, 393, 394, 395 age, 403 — —

1944-1945 Index 539

Carp continued Cottontail rabbit, 449, 451; sec also Rabbit in Onized Lake continued Cottonwood, 496, 497, 573 census (catch, yield), 382, 383, 384,402,406 Crane Lake, 364 weight, 382, 383 Crappie {see also Black crappie. White Carya crappie) alha, 498, 505 in Onized Lake cordijormis, 498, 505 census (catch, yield), 404 glabra, 498, 505 death of, 381 laciniosa, 498, 505 stocking, 378 ovalis, 498, 505 Crataegus, 500; sec also Hawthorn ovata, 498, 505 mollis, 497

pecan, 498, 505 ; see also Pecan Crayfish, 385, 388 Catfish, 382; see also Black bullhead, Creeping water primrose, 377 Bullheads, Yellow bullhead Cucumber tree, 499 Cattail, 377 Cucurbita, 501 Cedar, 522; sec also Red cedar Cyperus, 338

Celastrus scandens, 500 ; see also Bittersweet Cypress, 492, 499, 504, 513, 516, 522, 531 Ccltis, 499 Ceratopliyllum dcmersum, 338, 377 D Cercis canadensis, 499 Chaenobryttus gulosus, 395-7; see also Dafila acuta tzitzihoa (see also Pintail) Warmouth bass kill, 362 Charitonetta albeola, 362; sec also Bufflehead Dakota territory, waterfowl hunting regula- Chaitlclasmus strepenis {see also Gad wall) tions in, 332

kill, 362 Decoys, live ; see Duck Chautauqua (Lake), 394 Deer, laws relating to, 340 Chautauqua National Wildlife Refuge, 327, Dermaccntor luiriahilis, 472 367, 369, 370, 466 Dewberry, 500 Chestnut, 503 Dieback; see Elm Chiggers, 472 Diospyros virginiana, 500 Chinquapin oak, 498, 505 Dog Cinnamon teal, laws relating to, 332 as predator of squirrels, 473 Citriillus, 501 use in hunting, 453, 516, 517, 518

Clear Lake, 364 Dogwood ; see Flowering dogwood, Gray Climbing buckwheat, 501, 505 dogwood Committee on Bacteriological Technic, 422, Dothiorella ulmi, 444 437 Dove, 526 Common dog tick, 472 Duck {see also specific references) Common sucker banding, 333, 334, 363, 365, 367, 369 in Onized Lake chronology of flight, 335, 340-51 age, 403 clubs, 333, 343, 353, 354, 356, 362, 364, 365, census (catch, yield), 382, 383, 402, 406 366, 368; see also Duck Island Pre- weight, 382 serve, Waterfowl clubs Coniothyriiim, 444 crippling, 368 Coontail, 338, 377 dabbling Coot shooting pressure on, 345 chronology of flight, 351, 355 vulnerability, 339 kill, 340, 351, 355, 366 diving, 368 laws relating to, 351, 355 feeding habits, 340 popularity, 351 flocking habits, 339, 340 shooting pressure on, 351 laws relating to, 354 vulnerability, 340 shooting pressure on, 345, 354 Copper sulfate injections; sec Elm vulnerability, 339, 340 Corn feeding habits, 336, 337 as duck bait; see Duck flocking habits, 336, 337 as squirrel food, 450, 451, 489, 490, 492, 493, juveniles 497, 501, 502, 503, 504, 505, 506, 507, chronology of flight, 354, 371 510, 521, 523, 524, 531 population density^, influence of, 3 54 Cornus vulnerability, 354, 371 florida, 500 kill, 327-72 paniculata, 500 composition of, 366 Corylus americana, 500; see also Hazelnut rate, 367 — —

540 Illinois Natural History Survey Bulletin Volume 23

Duck continued Elm continued laws relating to, 327—72 diseases 417, 423, 430 bag limit, 327, 328, 331, 332, 359, 368, 370, dieback, 415, 416, 371 flux, 411, 412, 417, 423, 429, 431, 433, 434,

; flux baiting, 327, 328, 331, 333, 356, 358, 364, 445, 446 see also slime 370, 371 leaf drop, 416, 423 California, 331 malachite green tests, 441 Canada, 327, 328 slime flux, 408, 411; see also flux Dakota territory, 332 soil tests, 443 decoys, live, 327, 328, 331, 333, 356, 364, wetwood, 407-48 370, 371 bacterial isolations, 418 England, 328 branch pathology, 414 favoring depleted species, 328, 332, 361, copper sulfate injections, 439, 440, 441, 370, 371 443, 446 history of, 328, 329, 331, 332, 333 distribution, 408 hunting zones, 329, 331, 332, 355, 356, 367 8-hydroxyquinolin sulfate injections, 439, Illinois, 327-71 440, 441, 443, 446 Iowa, 331 Elgetol injections, 441, 443 Kentucky, 331 foliage pathology, 416 Massachusetts, 333 gas analysis, 436 New Jersey, 331 growth associations, 444 Ohio, 331 Helione injections and feeding, 439, 446 Oklahoma, 331 histology, 419 open season, 327, 328, 331, 334, 340, 354, hosts, 408 355, 356, 361, 368, 370, 371 inoculations, 423 Pennsylvania, 331 mercuric chloride injections, 439, 440, possession limit, 331, 370 441, 443, 446 Rhode Island, 328 organism, 420 shell limit, 328, 331, 333, 368, 370, 371 biochemical reaction, 422 shooting hours, 328, 331, 332, 356, 368, 370, cultural characters, 420 371 morphology, 420 South Dakota, 333, 362 taxonomy, 422 territories, 328, 370; sec also Dakota pH of sap, 438 territory {abo've) pressures in affected elms, 410, 430 mortality, 336 root pathology, 413 quotient, 335, 340 sap analysis, 437; see also pH of sap populations, 327—72 {abo've) density, influence of, 351, 356 seed tests, 444 productivity, 361; see also Wood duck silver nitrate injections, 439, 440, 441, shooting pressure on species, 334, 335, 340, 443, 446 341, 361, 369 trunk pathology, 409 shooting pressure index, 358, 359 urea feeding, 439 shooting pressure quotient, 335, 336, 340 wilt, 410, 412, 414, 416, 417, 418, 423, 425, vulnerability of species, 334, 335, 336, 340, 426, 429, 430, 431, 432, 439, 440, 441, 361, 370 444, 445, 446 vulnerability quotient, 334, 335, 340 toxicity tests for, 425 Duck Island Preserve, 327, 351, 354, 355, 359, as source of squirrel food, 465, 466, 489, 490, 360 492, 493, 496, 497, 504, 506, 520, 522, Duck potato, 339 531, 532; see also specific references Ducks Unlimited, 370 Elodea, 377 Embarrass River, 492 E Endomyccs magnusii, 408 Endoparasites, 472 Ectoparasites, 472 England, waterfowl hunting regulations in, 8-hydroxyquinolin sulfate injections; see Elm 328 Elaeagnus, wetwood of, 407 English elm Elgetol injections; see Elm dieback, 423 Elm {see also specific references) flux, 423 bacteria attacking leaf drop, 423 Erwinia nimipressuralis, 423, 429, 430, wetwood, 408, 423, 445 433, 439, 444, 445, 446 bacterial isolations, 418 Pseudomonas lignicola, 422 wilt, 423 —

1944-1945 Index 541

Erismatura jamalcensis ruhida (sre also Fox squirrel continued Ruddy duck) weights, 460, 467, 530 kill, 362 wounds, 470; see also crippling [above) Erivinia, 446 young rearing, 486, 530 nimipressuralis, 423, 429, 430, 433, 439, 444, Fraxinus 445, 446 americana, 499; see also White ash salicis, 422, 444 profunda, 499 Eucalyptus, 497 Fungi Alternaria, 444 Coniothyrium, 444 Dotliiorella ulnii, 444 Fagus (/randifol'ta, 499; see also Beech Endomyces maynusii, 408 Fish; see specific references, Lake management / erticillium, 444 Fleas, 472 albo-atrum, 444 Flood, effect on wood duck, 363 Flowering dogwood, 500

Flux ; see Elm Fork Lake, 394, 395 Gadwall Fox, 451 banding, 361 Fox squirrel, 449—536; sre also Bryant fox chronology of flight, 343 squirrel feeding habits, 338 activity, 464, 529 kill, 343, 351, 362, 366 age classes, 460, 529 laws relating to, 332, 371 breeding, 473, 530 mortality quotient, 339, 343, 344, 345 mating chase, 481 shooting pressure, 343 physiological aspects, 481 quotient, 339, 345 seasons, 474 vulnerability, 338, 370 color, 471 quotient, 339 competition, 463, 467, 529 Game [see also specific references) crippling, 518; see also wounds (heloiu) code, Illinois, 333 deformities, 470, 530 laws; see Deer, Sejuirrel, Upland game. den boxes, 522 Waterfowl diseases, 471 Glaucionetta clantjula americana, 362; see also dispersal, 467 Golden-eye

Gleditsia triacantlios, 499 ; see also Honey foods and feeding, 496, 531 ; see also management {beloiv) locust

habitats; see Illinois habitats {heloic) CJolden-eye ; see also Glaucionetta clanc/ula hunting, 455, 516; see also kill [below) americana methods, 516 kill, 351 seasons, 524 Golden shiner, 400-2 Illinois habitats, 455, 490 in Huron River (Michigan) importance, 449 age, 401, 402 kill, 519, 531 growth, 402 length, 470, 530 length, 401 litter size, 489 in Onized Lake local movements, 466 age, 401, 403 management, 520 census (catch, yield), 380, 381, 382, 383, migration, 466 384, 400, 401, 406 mineral requirements, 510 growth, 400, 401, 402 molt, 471, 530 length, 383, 400, 401 nesting, 510, 531; see also den boxes (al/oiw) stocking, 402 parasites, 471 weight, 380, 381, 382, 383, 400 populations, 454 Gooseberry, 500 Wild grape cycle, 45 5 Grape, 504; see also density, 454, 455, 529 Grass Lake, 340, 351, 394 distribution, 454 Gray dogwood, 500 predation on, 473 Gray duck [see also Gadwall, Widgeon) seasonal movements, 465 feeding habits, 338 sex ratio, 451, 458, 529 kill, 362 449-536 species ratio, 451, 455, 529 Gray squirrel, storing habits, 508 activity, 464, 529 water requirements, 510 age classes, 460, 529 — —

542 Illinois Natural History Survey Bulletin Volume 23

Gray squirrel continued Green-winged teal continued breeding, 451, 473, 530 kill, 351, 354, 362, 366 mating chase, 481 laws relating to, 332, 355, 371 physiological aspects, 481 mortality quotient, 339, 343, 344, 345 seasons, 474 population density, influence of, 3 54 color, 471 shooting pressure, 342 competition, 464, 529 quotient, 339, 345 crippling, 518; see also wounds {below) vulnerability, 338, 355, 370 deformities, 470, 530 quotient, 339 den boxes, 522 Gymnocladus dioicus, 499 diseases, 471 dispersal, 467 H foods and feeding, 496, 531; see also management {beloiv) Hackberry, 499 habitats; see Illinois habitats {beloiv) Half-wing geometer, 503 hunting, 455, 516; see also kill {beloiv) Hawk, 473 methods, 516 Hawthorn, 497, 500, 520 seasons, 524 Hazelnut, 500, 504, 505, 507 Illinois habitats, 455, 490 Helione injections and feeding; see Elm importance, 449 Helminth worms, 471 kill, 519, 531 Hepatic coccidiosis, 473 length, 470, 530 Hickory, 455, 464, 465, 466, 489, 490, 492, 493, litter size, 489 496, 497, 505, 507, 508, 509, 513, 520, local movements, 466 522, 523, 525, 531, 532; see also specific management, 520 references migration, 466 Honey locust, 499, 504 mineral requirements, 510 Hoplopleura sciuricola, 472 molt, 471, 530 Horse chestnut, slime flux of, 408 nesting, 510, 531; see also den boxes {above) Horse Shoe Lake, 394 parasites, 471 Horse Shoe Lake Game Refuge, 509 populations, 454, 495 Hudson River, 466 cycle, 455 Hunting density, 451, 455, 529 illegal, 358 distribution, 454 public, 368 predation on, 473 regulations; see Squirrel, Upland game, seasonal movements, 465 Waterfowl sex ratio, 451, 458, 529 seasons

species ratio, 451, 455, 529 on ducks ; see Duck storing habits, 508 on squirrels; see Squirrel water requirements, 510 zones weights, 460, 467, 530 for squirrels; see Squirrel

wounds, 470 ; see also crippling losses for waterfowl; see Waterfowl {above) Huro salmoides, 385-8; see also Largemouth young rearing, 486, 530 bass Great Britain, squirrel investigations in, 466 Huron River (Michigan), 401, 402 Greater scaup, laws relating to, 332 Green sunfish, 397—8; see also Sunfish in Michigan growth, 398 Illinois stunting, 398 game code, 333 in Onized Lake squirrel hunting regulations in, 525 age, 397, 403 waterfowl hunting regulations in, 327—72 census (catch, yield), 380, 381, 382, 383, wood duck in, 362, 363, 364 384, 397, 398, 406 Illinois River, 328, 333, 339, 357, 362, 364, 365, growth, 397, 398 492, 505 length, 383, 397, 398 valley, 333, 338, 339, 342, 343, 351, 353, 355, weight, 380, 381, 382, 383, 397 356, 362, 363, 365, 366, 368, 369, 371 Green-winged teal {see also Teal) Illinois State Department of Conservation, banding, 361 333, 365, 367, 449, 454, 519 chronology of flight, 342, 355 Impalaia, 472 feeding habits, 338 Indiana flocking habits, 338 black squirrels in, 471 — —

1944-1945 Index 543

Indiana continued Largemouth bass continued squirrel hunting regulations in, 525 in Wisconsin, growth, 387

Iowa Leaf drop ; see Elm squirrel hunting regulations in, 525 Lepomis squirrel investigations in, 454 cyanellus, 397-8; see also Green sunfish waterfowl hunting regulations in, 331 macrocliirus, 392-5; sec also Bluegill wood duck in, 362, 363 Lesser scaup {see also Bluebill) Ironwood, 499 banding, 361 Ixodoidea, 472 chronology of flight, 355 flocking habits, 339, 340 kill, 362, 366 laws relating to, 332, 355, 371 Jack Lake, 364 mortality quotient, 339, 343, 344, 345 Juglans shooting pressure, 351, 355 c'lncrea, 498 quotient, 339, 345

nigra, 498 ; sec also Black walnut vulnerability, 339, 340, 370 Juniperus 'virg'ni'iana, 499; sec also Red cedar quotient, 339 Jussiaea diffusa, 111 Lice, 471, 472 Lirjuidambar styraciflua, 499, 509; see also K Sweet gum Liriodendron tulipifera, 499 Kansas, squirrel investigations in, 471 Littleford elm Kaskaskia River, 492 dieback, 423 Kentucky flux, 423 squirrel hunting regulations in, 524, 525 leaf drop, 423 squirrel investigations in, 475 wetwood, 408, 423, 445 waterfowl hunting regulations in, 331 bacterial isolations, 418 Kentucky coffee tree, 499 wilt, 417 Locust; sec Black locust, Honey locust

Lotus, 501 ; sec also American lotus Louisiana, largemouth bass in, 387 Lake management artificial propagation, 374 M censusing (catch, yield), 374, 378, 379, 380, 381, 382, 383, 384, 385, 386, 387, 388, Magnolia acuminata, 499 389, 391, 392, 393, 394, 395, 396, 397, Maine, wood duck in, 363 398, 399, 400, 401, 402, 403, 404, 405, Mallard 406 banding, 334, 361, 369, 370 cropping, 392 chronology of flight, 344, 355 fertility, 377 feeding habits, 337, 356, 357, 358, 359, 368, interspecific competition, 374 371 Onized Lake, 373-406 flocking habits, 337, 355 overfishing, 373 —1-06 kill, 351, 354, 358, 362, 366, 367, 369 overpopulation, 374, 378 laws relating to, 331, 332, 354, 355, 356, 357, pollution, 378 358, 368, 371 stocking, 374, 378, 395, 399, 402, 405 mortality quotient, 339, 343, 344, 345 stunting, 374, 388, 398, 406 population, 356, 366, 368, 369 Largemouth bass, 385—8 population density, influence of, 351, 354 in Louisiana, growth, 387 shooting pressure, 344, 345, 354, 355, 358, in Onized Lake 367 age, 385, 386, 403, 406 quotient, 339, 345 census (catch, yield), 380, 381, 382, 383, vulnerability, 337, 338, 354, 370 384, 385, 386, 387, 406 quotient, 339

growth, 385, 386, 387, 388 Malus, 500 ; see also Apple length, 383, 385, 386, 387 Mange, 471, 472, 473, 530 stocking, 378 Maple (see also specific references) survival, 403 slime flux of, 408 weight, 380, 381, 382, 383, 385 squirrel use of, 465, 466, 490, 492, 493, 496, in Sportsmen's Lake 497, 504, 520, 521, 522, 531 growth, 386, 387 Mareca americana (see also Widgeon) length, 386 kill, 362 weight, 387 Mason County State Forest, 487 23 544 Illinois Natural History Survey Bulletin Volume

Massachusetts, wood duck in, 333, 362 New England Mercuric chloride injections; see Elm gray squirrel migration, 466 Mescistocirrcus, 472 squirrel investigations in, 455 Michigan New Jersey, waterfowl regulations in, 331 duck in, 363 black squirrels in, 471 New York, wood Reservoir, 392 golden shiner in, 401, 402 Norris 390, Carolina, squirrel investigations in, 471 green sunfish in, 398 North squirrel) Lake, 333 Northern gray squirrel {see also Gray squirrel hunting regulations in, 449, 524, 525 distribution, 454 squirrel investigations in, 449, 453, 466, 467, Notemigonus crysoleucas auratus, 400-2; see shiner 503, 505, 509, 518 also Golden upland game regulations in, 340 Nutgrass, 338 wood duck in, 363 Nyroca, 340 Micrococcus dendroporthos, 408 affinis {see also Lesser scaup, Bluebill) Migratory Bird Act, 328, 329, 332, 361, 370 kill, 362 Migratory Bird Treaty Act, 328, 329, 332, 361, americana {see also Redhead) 370 kill, 362 Migratory waterfowl; sec Waterfowl, Duck, collaris {see also Ring-necked duck. Black- specific references jack) Minnesota kill, 362 gray squirrel migration, 466 'valisineria {see also Canvasback) squirrel hunting regulations in, 525 kill, 362 Minnow {see also Blunt-nosed minnow) Nyssa as bait, 383 aqiiatica, 499 ; see also Tupelo gum census (catch, yield), 405 syl'vaiica, 499 Mississippi River, 351, 357, 362, 466, 492, 502, 505, 508 O Missouri squirrel hunting regulations in, 524, 525 Oak {see also specific references) squirrel investigations in, 510 slime flux of, 408 wood duck in, 363 squirrel use of, 455, 464, 465, 466, 490, 492, Mites, 471, 472 493, 504, 509, 513, 515, 520, 521, 522, Mockernut, 498, 505 523, 525, 528, 531, 532; see also Acorn Moline elm Oak apple galls, 503 dieback, 423 Oats, 507 flux, 423 Ohio leaf drop, 423 squirrel hunting regulations in, 449, 525 wetwood, 408, 445 squirrel investigations in, 449, 453, 471, 475 bacterial isolations, 418 waterfowl hunting regulations in, 331 wilt, 423 Ohio River, 466, 492 More Game Birds in America, 329, 331 Oklahoma, waterfowl regulations in, 331 Morone internipta, 398-9; see also Yellow Onized Lake, 373-406 bass aquatic plants in, 377 Mortality quotient; sec Duck census (catch, yield), 374, 378, 379, 380, 381, Morus 382, 383, 384, 385, 386, 387, 388, 389, rubra, 499 391, 392, 393, 394, 395, 396, 397, 398, wetwood of, 407 399, 400, 401, 402, 403, 404, 405, 406 Mud hen {see also Coot) characteristics, 375, 400 shooting pressure on, 3 51 cropping, 392 Mulberry, 466, 497, 504, 507, 510, 520, 521, 531, fertility, 377

532 ; see also Red mulberry fish population Munuscong Waterfowl Refuge, 370 age distribution of, 402 analysis of, 382 N black bullhead {see also bullheads, beloiv) age, 403 Nelumbo census (catch, yield), 380, 381, 382, 383,

lutea, 377, 501 ; see also Lotus 399, 404, 406

pcntapetala, 377, 501 ; see also Lotus weight, 380, 381, 382, 383, 399 Nematodes, 472 black crappie {see also crappie, beloiv) Nettion carolinensc {see also Green-winged age, 389, 403 teal) census (catch, yield), 380, 381, 382, 383, kill, 362 384, 388, 389, 391, 404, 406 — —— — —

1944-1945 Index 545

Onized Lake continurd Onized Lake continued fish population continued fish population continued black crappie continued minnow {see also blunt-nosed minnow, growth, 389, 390, 392 above) length, 383, 388, 389, 390, 391, 392 as bait, 383 weight, 380, 381, 382, 383 census (catch, yield), +05 bluegill warmouth bass age, 392, 403 age, 395, 396, 403 census (catch, yield), 380, 381, 382, 383, census (catch, yield), 380, 381, 382, 383, 38+, 392, 393, 39+, +0+, +06 384, 395, 396, 397, 406 death of, 381 growth, 395, 396, 397, 404 growth, 392, 393, 39+, 395 length, 383, 395, 396, 397 length, 383, 392, 393 weight, 380, 381, 382, 383, 395 weight, 380, 381, 382, 383, 392 3'ellow bass blunt-nosed minnow age, 399, 403 age, +03 census (catch, yield), 380, 381, 382, 383, census (catch, yield), 382, 383, +02, +06 384, 398, 399, 404, 406 weight, 383 growth, 399 bullheads {see also black bullhead, abo-ve, length, 383, 398, 399 yellow bullhead, belo-xv) stocking, 399 age, 399 weight, 380, 381, 382, 383, 398, 399 census (catch, yield), 380, 399, +00 yellow bullhead {see also bullheads, above) length, 383, 399, 400 age, 400, 403 weight, 380, 399 census (catch, yield), 380, 381, 382, 383, carp 384, 399, 400 age, +03 length, 399, 400 census (catch, yield), 382, 383, 38+, +02. weight, 380, 381, 382, 383 +06 overfishing, 373-406 weight, 382, 383 overpopulation, 378 common sucker pollution, 378 age, +03 stocking, 378, 399, 402, 405 census (catch, yield), 382, 383, +02, +06 stunting, 378, 406 weight, 382 Open season ; see Duck crappie {sec also black crappie, above, Opossum, 451 white crappie, beloiv) Orcliopeas

census, +0+ /iO'ivardii, 472 • death of, 381 nepos, 472 stocking, 378 Osage orange, 465, 473, 490, 492, 497, 499, 504, golden shiner 506, 508, 510, 511, 513, 516, 521, 522, age, +01, +03 531 census (catch, yield), 380, 381, 382, 383, Oscillatoria, 111 38+, +00, 401, 406 Ostrya virginiana, +99 growth, 400, 401, 402 Overfishing; see Onized Lake length, 383, 400, 401 Owl, +73, 513 stocking, 402 weight, 380, 381, 382, 383, 400 green sunfish {see also sunfish, beloiv) age, 397, 403 Parasites of squirrel; sec squirrel census (catch, yield), 380, 381, 382, 383, Parasitoidea, +72 384, 397, 398, 406 Pawpaw, 500 growth, 397, 398 Peanuts, as squirrel food, 523 length, 383, 397, 398 Pecan, +66, +92, +93, +97, +98, 503, 50+, 505, weight, 380, 381, 382, 383, 397 506, 509, 522, 531 largemouth bass Pennsylvania, waterfowl hunting regulations age, 385, 386, 403, 406 in, 331 census (catch, yield), 380, 381, 382, 383, Persimmon, 500 384, 385, 386, 387, 406 Pheasant, 520 growth, 385, 386, 387, 388 Pliiyalia titea, 503 length, 383, 385, 386, 387 Phytolacca decandra, 501 ; see also Pokeberries stocking, 378 Phytomonas tumefacicns, +39 survival, +03 Pickerelweed, 377 weight, 380, 381, 382, 383, 385 Pignut, +98, 505 546 Illinois Natural History Survey Bulletin Volume 23

Pin oak, 472, 498, 502, 505, 508 Quercus—co ntinued

Pine, 504 vclutina, 498, 505 ; see also Black oak Pintail wetwood of, 407 banding, 334, 361, 369 Querquedula discors (see also Blue-winged chronology of flight, 342 teal) feeding habits, 337, 368, 371 kill, 362 kill, 351, 354, 362, 366, 369 laws relating to, 331, 332, 354, 368, 371 R mortality quotient, 339, 343, 344, 345 population, 366, 369 Rabbit, 472, 516; see also Cottontail rabbit density, influence of, 351, 354 Raccoon, 363, 449, 513 shooting pressure, 342, 354 Rana catesbeiana, 111 quotient, 339, 345 Raspberry, 500, 521 vulnerability, 337, 338, 339, 354, 370 Red cedar, 499, 522 quotient, 335, 339 Red fox, 473 Pistakee Lake, 394 Red gum, 499 ; see also Sweet gum Plataniis Red maple, 466, 498 acerifolia, wetwood of, 408, 412, 419 Red mulberry, 499; see also Mulberry wetwood of, 407 Red oak, 498, 505 Plum {see also Wild plum) Red squirrel, distribution of, 454, 529 slime flux of, 408 Red-tailed haw^k, 473 squirrel use of, 510 Redbud, 499 Poa pratensis, 501 Redhead Pokeberries, 504; see also Pokeweed banding, 361

Pokeweed, 501 ; sec also Pokeberries feeding habits, 340

Polygonum, 338, 501 ; sec also Smartweeds flocking habits, 340

scandens, 501 ; see also Climbing buckwheat kill, 351, 362 Pomoxis laws relating to, 332, 333, 361, 368, 371 annularis, 388 mortality quotient, 345 nigro-maculatus, 388—92; sec also Black shooting pressure on, 361 crappie vulnerability, 340 Pond lily, 377 Reelfoot Lake, 390, 392, 395, 397 Pontederia cordata, 111 Rhode Island, waterfowl hunting regulations Poplar, slime flux of, 408 in, 328 Populus Rhus, 500 nigra italica, wetwood of, 407 Ribes, 500 wetwood of, 407 Ring-necked duck Possession limit; see Duck banding, 361 Prairie chicken, laws relating to, 340 chronology of flight, 355 Predator of wood duck; see Squirrel feeding habits, 340 Prosopis, wetwood of, 407 kill, 362, 366 Primus laws relating to, 332, 355, 368, 371 americana, 500; see also Wild Plum mortality quotient, 339, 344, 345 serotina, 499; see also Black cherry. Wild shooting pressure, 355 cherry quotient, 339, 345 Prunus, wetwood of, 407 vulnerability, 340, 370 Pseudomonas lignicola, 422, 423, 444 quotient, 339 Public shooting grounds, 368 River bulrush, 338 Pumpkin, 501 Robinia pseudoacacia, 499 Pumpkin ash, 499 Rock River, 492 Round worm, 471

Q Rubus, 500 ; see also Blackberry, Raspberry

Ruddy duck ; sec also Butterball

Quail, 520 chronology of flight, 3 55 Quercus kill, 362, 366 alba, 498, 505 laws relating to, 332, 355, 361, 371 bicolor, 498, 505 mortality quotient, 339, 343, 344, 345 borealis maxima, 498, 505 shooting pressure, 345, 361 imbricaria, 498, 505 quotient, 339, 345, 361 macro carpa, 498, 505 vulnerability, 339, 340, 355, 370 Muhlenbergii, 498, 505 quotient, 339 palustris, 498, 505 Rye, 501, 503 —

1944-1945 Index 547

Slime flux continued of poplar, 408 Sagittaria, 111 Slippery elm, 498 latifolia, 339 flux, 423 Salix, wetwood of, 407 leaf drop, 423 Sangamon River, 333, 358, 364, 365, 368 wetwood, 408, 423, 445 Sarcoples, 471 bacterial isolations, 418 Sassafras, 500 wilt, 423 Sassafras officinale, 500 Small pignut, 498, 505 Scaup [see also Greater scaup, Lesser scaup) Smartweeds, 338, 501, 504 laws relating to, 368 Society of American Bacteriologists, 422, 437 Scirpus flitviatilis, 338 Soja max, 501 ; sec also Soy bean Sciurus South Dakota, wood duck in, 333, 362 carolinensis Southern gray squirrel {see also Gray squirrel)

carolinensis, 454, 529 ; see also Gray distribution, 454 squirrel Soy bean, 490, 501, 507 leucotis, 454, 529; see also Gray squirrel Sparland Public Shooting Ground, 340 nigcr rufiventer, 454, 529 ; see also Fox Spatula clypcata {see also Shoveler) squirrel kill, 362

Secole, 501 ; see also Rye Spoonbill {sec also Shoveler) Senachwine Lake, 394 feeding habits, 339 Seney National Wildlife Refuge, 370 kill, 351, 362 Serviceberry, 500, 521 vulnerability, 338, 339 Shagbark, 498, 505 Sportsmen's Lake, 386, 387 Shingle oak, 498, 505 Sprig {see also Pintail) Shooting hours; see Duck kill, 362

Shooting pressure index ; sec Duck Squash, 501 Shooting pressure quotient; sec i^uck Squirrel {see also Bryant fox sejuirrel, Fox Shooting pressure on species; sec Duck squirrel. Gray squirrel, Red squirrel) Shoveler (see also Spoonbill) bag limit, 528 banding, 361 breeding, 449, 450, 451, 452 chronology of flight, 342, 355 competition, 463, 464, 467, 529

feeding habits, 339 crippling, 518, 531 ; see also wounds {bcloiu) kill, 354, 362, 366 diseases, 530 laws relating to, 332, 354, 355, 371 dispersal, 530 mortality quotient, 339, 343, 344, 345 foods and feeding, 531 population density, influence of, 354 habitats; see Illinois habitats {bcloiu) shooting pressure, 354 hunters, 516, 531 quotient, 339, 342, 345 hunting, 450, 516 {see also kill, beloiv) vulnerability, 338, 354, 355, 370 methods, 516 quotient, 339 regulations, 449, 524 Siberian elm seasons, 449, 451, 452, 529, 532 dieback, 423 zones, 450, 475, 477, 516, 517, 518, 519, flux, 423 526, 529, 532 leaf drop, 423 Illinois habitats, 531 wetwood, 408, 423, 445 kill, 519, 531 inoculations, 424 management, 449, 450, 520, 524, 531 bacterial isolations, 418, 424, 425 parasites, 530 wilt, 423 populations toxicity tests for, 424 censusing, 452, 453, 529 Silver maple, 498 trends, 452, 453 Silver nitrate injections; sec Elm as predator of wood duck, 363 Siphonaptera, 472 predation on, 473 Skunk, 451, 472 species ratios, 451, 455, 529 Slime flux, 407, 408, 411 trapping, 450, 451, 453 of apple, 408 wounds, 530; sec also crippling {above) of birch, 408 young rearing, 530 of elm, 408, 411 Stripmines, 496 of horse chestnut, 408 Sugar maple, 498, 504 of maple, 408 Sumach, 500 of oak, 408 Sunfish isee also Green sunflsh) of plum, 408 eff^ect on largemouth bass, 385 548 Illinois Natural History Survey Bulletin Volume 23

Swamp white oak, 498, 505 Vert'icillium, 444 Swan, laws relating to, 332 albo-atrum, 444 Sweet gum, 504, 509, 513, 531; see also Red Vitis, 500; see also Wild grape gum Vulnerability quotient; see Duck Sycamore, 490, 496 W

Wabash River, 492 Taenia pisiformis, 472 Walnut, squirrel use of, 490, 492, 493, 497, 505, Tamiasciurus liiidsonicus loquax, 454, 529 508, 509, 520, 521, 522, 523, 528, 531 Tapeworm, 471 Warmouth bass, 395-7 in Onized Lake Taxodium distkhum, 499 ; see also Cypress Teal {see also Blue-winged teal. Green-winged age, 395, 396, 403 teal) census (catch, yield), 380, 381, 382, 383, laws relating to, 3 54 384, 395, 396, 397, 406 shooting pressure on, 354 growth, 395, 396, 397, 404 vulnerability, 338, 339, 354 length, 383, 395, 396, 397 Tennessee, black crappie in, 392 weight, 380, 381, 382, 383, 395 Territories, waterfowl regulations, 328, 370; in Reelfoot Lake, growth, 395, 397 see also Dakota Territory Waterfowl (see also Duck, specific references) Texas, squirrel investigations in, 453, 471, 475, hunting regulations, 327—72 481, 487, 503 bag limit, 327, 328, 331, 332, 359, 368, 370, Thompson Lake drainage district, 358 371 Ticks, 472 baiting, 327, 328, 331, 333, 356, 358, 364, Tilia glabra, 499 370, 371 Toxylon pomifcrum, 499; see also Osage California, 331 orange Canada, 327, 328

Tritlcum, 501 ; see also Wheat Dakota Territory, 332 Trombicula, 472 decoys, live, 327, 328, 331, 333, 356, 364, Tsuga, wetwood of, 407 370, 371 Tularemia, 449, 473 England, 328 Tulip poplar, 499 favoring depleted species, 328, 332, 361, Tung, slime flux of, 408 370, 371 Tupelo gum, 492, 499, 504, 513, 516, 531 federal, 328, 370 Turtle, 385, 388 history of, 328, 329, 331, 332, 333 Typha latifolia, 377 hunting zones, 329, 331, 332, 355, 356, 367 Illinois, 327-72 U Iowa, 331 Kentucky, 331

U I mils Massachusetts, 333 alata, 498 New Jersey, 331

americana, 498 ; see also American elm Ohio, 331 wetwood of, 408, 423, 445 Oklahoma, 331 ftilva, 498 open season, 327, 328, 331, 334, 340, 354, wetwood of, 408, 423, 445 355, 356, 361, 368, 370, 371 procera, wetwood of, 408, 423, 445 Pennsylvania, 331 pumila, wetwood of, 408, 423, 424, 445 possession limit, 331, 370

wetwood of, 407 ; see also Elm Rhode Island, 328 U. S. Bureau of Biological Survey, 331 shell limit, 328, 331, 333, 368, 370, 371 U. S. Fish and Wildlife Service, 327, 333 shooting hours, 328, 331, 332, 356, 368, 370, U. S. Weather Bureau, 329, 331 371 Upland game hunting regulations, Michigan, South Dakota, 333, 362 340 in territories, 328, 370; see also Dakota Urbana Township Wildlife Area, 510 Territory Urea feeding; sec Elm Waterfowl clubs, 333, 368, 371 ; see also Duck clubs, Duck Island Preserve Watermelon, 501 Waterweed, 377 f'allisneria spiralis, 339 Weasel, 473 Vermont West Virginia, squirrel investigations in, 503 gray squirrel migration, 467 Western fox squirrel {see also Fox squirrel) wood duck in, 363 distribution, 454, 529 1944-1945 Index 549

Wetwood Wisconsin of Abies, 407 gray squirrel migration, 466 of Elaeayniis, 407 largemouth bass in, 387 of Moras, 407 squirrel hunting regulations in, 525 of Plataniis, 407 squirrel investigations in, 515 acerifolia, 408, 412, 419 wood duck in, 363 of Poptiltis, 407 Woodchuck, 451 nigra italic a, 407 Wood duck of Prosopis. 407 in Arkansas, 363 of Prutuis, 407 banding, 361, 363 of Qua (US, 407 in British Columbia, 363 of Sulix, 407 efl^ect of floods on, 363 of Tsuya, 407 in Illinois, 362, 363, 364

of Ulmus, 407 ; jr? rt/io Elm in Iowa. 362, 363

americana, 408, 423, 445 ; .wv also kill, 362, 363, 371 American elm laws relating to, 332, 333, 361, 362, 363, 371

ful'Va, 403, 423, 445 ; see also Slippery elm in Maine, 363 in proccra, 408, 423, 445 ; sec also English Massachusetts, 362 elm in Michigan, 363 in purnila, 408, 423, 424, 445 ; sec also Missouri, 363 Siberian elm in New York, 363 Wheat, 490, 501, 507 population, 363

Whistler, 362 ; see also Golden-eye predators of, 363 White ash, 490, 499, 513, 531 productivity, 363 White crappie in Illinois shooting pressure on, 364 census (catch, yield), 388 in South Dakota, 362 stunting, 388 in Vermont, 363 White oak, 498, 505 in Wisconsin, 363 Widgeon banding, 361

chronology of flight, 342, 343, 3 55 feeding habitj, 338 Yellow bass, 398-9 in Onized Lake hunting pressure on, 343 ; see also shooting pressure (helo-Lv) age, 399, 403

kill, 343, 351, 354, 362, 366 census (catch, yield), 380, 381, 382, 383, laws relating to, 331, 332, 354, 355, 371 384, 398, 399, 404, 406 mortality quotient, 339, 343, 344, 345 growth, 399 population density, influence of, 354 length, 383, 398, 399 shooting pressure, 342, 345, 354; sec also stocking, 399 hunting pressure (aho-vc) weight, 380, 381, 382, 383, 398, 399 (}uotient, 339, 345; see also hunting pres- Yellow bullhead [sec also Bullheads) sure, shooting pressure (above) in Onized Lake vulnerability, 338, 354, 355, 370 age, 400, 403 quotient, 339 census (catch, yield), 380, 381, 382, 383, Wild celery, 339 384, 399, 400 Wild cherry, 504; see also Black cherry length, 399, 400

Wild fowl ; see Waterfowl weight, 380, 381, 382, 383 Wild grape, 493, 497, 500, 503, 504, 510, 520 Yellow poplar, 521 Wild plum, 497, 500, 504, 510, 520, 521 Wild strawberries, 496, 504 Willow, 496, 497

Winged elm, 498 Zea mays, 501 ; see also Corn ^W'

Recent Publications A.—ILLINOIS NATURAL HISTORY SURVEY BULLETIN. Volume 21, Article 6.—Preliminary Investigation of Oak Diseases in Illinois. By J. Cedric Carter. June, 1941. 36 pp., frontis. + 51 figs., bibliog. (Bound with Article 7.) Volume 2l! Article 7.—A Needle Blight of Austrian Pine. By Robert L. Hulbary. June, 1941. 6 pp., frontis. + 3 figs., bibliog. (Bound with Article 6.) Volume 21, Article 8.—Duck Food Plants of the Illinois River Valley. By Frank C. Bellrose, Jr. August, 1941. 44 pp., frontis. + 35 figs., bibliog., appendix. Volume 22, Article 1.—The Plant Bugs, or Miridae, of Illinois. By Harry H. Knight. September, 1941. 234 pp., frontis. + 181 figs., bibliog., index. $1.25. Volume 22, Article 2.—Studies of North American Plecoptera, with special reference to the fauna of Illinois. By T. H. Frison. September, 1942. 122 pp., frontis. + 126 figs., bibliog., index. $1.00. Volume 22, Article 3.—Management of Small Artificial Lakes: a summary of fisheries investigations, 1938-1942. By George W. Bennett. February, 1943. 20 pp., frontis. + 7 figs., bibliog. Volume 22, Article 4.—The Prairie Chicken in Illinois. By Ralph E. Yeatter. May, 1943. 40 pp., frontis. -f 18 figs., bibliog. (Bound with Article.5.) Volume 22, Article 5.—Preferential Rating of Duck Food Plants. By Frank C. Bell- rose, Jr., and Harry G. Anderson. May, 1943. 16 pp., frontis. -|- 16 figs., bibliog. (Bound with Article 4.) Volume 22, Article 6.—Survey of the Illinois Fur Resource. By Louis G. Brown and Lee E. Yeager. September, 1943. 70 pp., frontis. + 33 figs., bibliog. (Bound with Article 7.) Volume 22, Article 7.—Illinois Furbearer Distribution and Income. By Carl 0. Mohr. September, 1943. 33 pp., frontis. + 24 figs., bibliog. (Bound with Article 6.) Volume 23, Article 1.—^The Caddis Flies, or Trichoptera, of Illinois. By Herbert H. Ross. August, 1944. 326 pp., frontis. -f- 961 figs., bibliog., index. $1.50. Volume 23, Article 2.—Duck Populations and Kill. By Frank C. Bellrose, Jr. Novem- ber, 1944. 46 pp., frontis. + 27 figs., bibliog. Volume 23, Article 3.—Overfishing in a Small Artificial Lake; Onized Lake near Alton, Illinois. By George W. Bennett. May, 1945. 34 pp., frontis. + 15 figs., bibliog. Volume 23, Article 4.—Wetwood of Elms. By J. Cedric Carter. August, 1945. 42 pp., frontis. + 30 figs., bibliog. B.—ILLINOIS NATURAL HISTORY SURVEY CIRCULAR. 32.—Pleasure .With Plants. By L. R. Tehon. November, 1942. (Second printing. with revisions.) 32 pp., frontis. + 9 figs. 33.—Controlling Peach Insects in Illinois. By S. C. Chandler and W. P. Flint. August, 1939. 40 pp., frontis. + 32 figs. 34.—Rout the Weeds! Why, When and How. By L. R. Tehon. August, 1943. (Third printing.) 47 pp., color frontis. + 13 figs. 35.—^Diseases of Small Grain Crops in Illinois. By G. H. Boewe. September, 1939. 130 pp., frontis. + 47 figs. 36.—Planting and Care of Shade Trees. By J. E. Davis. March, 1941. 23 pp., frontis. -1- 16 figs. 37.—Outwitting Termites in Illinois. By W. E. McCauley and W. P. Flint. August, 1942. (Second printing.) 23 pp., frontis. -f- 19»figs. 38.—Windbreaks for Illinois Farmsteads. By J. E. Davis. February, 1942. (Second printing.) 24 pp., frontis. -f 19 figs. 39.—How to Collect and Preserve Insects. By H. H. Ross. May, 1944. (Second printing, with additions.) 55 pp., frontis. + 63 figs. 40.—Control of Roundheaded Apple Tree Borer. By S. C. Chandler and W. P. Flint. April, 1942. 8 pp., 6 figs. C—ILLINOIS NATURAL HISTORY SURVEY MANUAL. l._Fieldbook of Illinois Wild Flowers. By the staff. March, 1936. 406 pp., color frontis. + 349 figs., index. $1.50. 2.—Fieldbook of Illinois Land Snails. By Frank Collins Baker. August, 1939. 166 pp., color frontis. + 170 figs., 8 pis. $1.00. 3.—Fieldbook of Native Illinois Shrubs. By Leo R. Tehon. December, 1942. 307 pp., 4 color pis. + 72 figs., glossary, index. $1.25.

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