526 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 5 



young too immature to be self-providing. 

 Cross (1942) found 100 per cent preg- 

 nancy during the period September 1—15 

 in a sample of 39 adult squirrel females in 

 Virginia. 



The calculated degree of loss in unborn 

 and immature squirrels resulting from an 

 early hunting season in Illinois is given in 

 table 27. The calculations in this table 

 are from data given in tables 2, 3, 15 and 

 20. The dates of the period included in 

 table 27 (July 16-October 31) were 

 chosen because they are a compromise 

 between the 1944 hunting seasons in the 

 central and southern zones, where most of 

 the squirrel kill was made and where 

 most of the data in tables 15 and 20 were 

 gathered in the years of this study. Table 

 3 indicates that of each 100 squirrels 

 bagged during the period July 16— October 

 31 (the kill during the period of Novem- 

 ber 1-15 in the northern zone is negligible, 

 while the kill during the period July 15^31 

 in the southern zone is appreciable), ap- 

 proximately 70 per cent were fox squirrels 

 and 30 per cent were gray squirrels. In 

 each 100 animals, there was an average of 

 12.8 mature and therefore potentially 

 breeding fox squirrel females and 7.7 po- 

 tentially breeding gray squirrel females 

 (figures derived from table 15). Preg- 

 nant among these mature females was an 

 average of 3.7 fox squirrels and 2.9 gray 

 squirrels, and lactating among them was 

 an average of 3.7 fox squirrels and 2.4 

 gray squirrels. 



The average number of young per lit- 

 ter during the second season, as determined 

 in the Illinois study, was 2.57 in fox squir- 

 rels and 2.43 in gray squirrels, table 20. 

 Calculations based on these data give, for 

 each bag of 100 squirrels, a loss of 9.5 

 unborn young and 9.5 suckling young of 

 the fox squirrel, and 7.0 unborn young and 

 5.8 suckling young of the gray squirrel. 

 Only females showing unmistakable evi- 

 dence of lactation were classified as lac- 

 tating; additional losses in young may 

 have resulted through killing of mothers 

 in the last stages of lactation or those still 

 exercising parental care over young. The 

 losses in unborn and suckling young were 

 in addition to squirrels bagged and fatally 

 hit by hunters in the period beginning July 

 16 and ending October 31, table 23. 



For each 100 squirrels bagged, 31.8 

 unborn and suckling animals, table 27, as 



well as the squirrels fatally wounded and 

 not recovered, must be added to the kill 

 in order to obtain the total theoretical loss. 

 The net loss might be somewhat less due 

 to the fact that squirrels suffer some mor- 

 tality during the post-natal and juvenile 

 periods. This loss, although not known, 

 is probably low, since the young are rela- 

 tively free from predation and usually are 

 well protected against the elements. 



A calculation of the total loss of unborn 

 and suckling young may be made by ap- 

 plying the findings in table 27 to the total 

 kill, which, as discussed under the heading 

 "Kill," was calculated for 1942 at 1,463,- 

 305 animals. The ratio of 31.8 young 

 lost for every 100 squirrels bagged applied 

 to this kill figure gives 465,331 as the cal- 

 culated number of young lost in an Illinois 

 season that begins early, July 16, and con- 

 tinues through October. 



Recommended Seasons. — The one 

 change needed in current Illinois laws to 

 provide a biologically sound squirrel hunt- 

 ing season is a later opening date in each 

 zone. In recommending this change, how- 

 ever, the writers have not forgotten that 

 early seasons are traditional in the state, 

 and that there are thousands of hunters 

 who sincerely believe in summer squirrel 

 hunting. That these hunters argue with 

 some logic is indicated by the fact that, 

 despite early hunting seasons in the past, 

 in many parts of the state there is still 

 good squirrel hunting. However, abun- 

 dance of squirrels in certain areas may be 

 the result of one or more of a number of 

 conditions, some of them local, that favor 

 squirrel survival. In some parts of the 

 state hunting is comparatively rare early 

 in the season and is intensive only through 

 the peak of the mast season, roughly 

 August 15 to September 15. In many 

 places, late in the season, when squirrels 

 are scarcer and the population becomes 

 scattered, interest in squirrel hunting de- 

 creases. In some agricultural communi- 

 ties the fall farm harvest requires the at- 

 tention of a large number of potential 

 hunters. In many counties, the advent 

 of the dove, waterfowl and upland game 

 seasons further reduces the number of 

 squirrel hunters. It is probable that the 

 76- to 93-day season in Illinois results 

 in only a slightly larger kill than would 

 a 45-day season coming during the 

 main mast season. However, a season be- 



