Vol. 6, No. 8 
Page 3 
collected In the more southerly areas than for those from farther north. A sta¬ 
tistical test of these data failed to indicate a high probability of a significant 
difference, but the possibi1ity cannot be ignored. Assuming differences did occur, 
what could have happened? First, it is possible that onset of breeding is par¬ 
tially controlled by temperature and that the warmer average temperatures prevail¬ 
ing in the south trigger the reproductive mechanism earlier there. Second, 
seasonal variation in survival may be responsible for differences in average birth 
dates of the surviving rabbits. Possibly, the late average birth date and lower 
variability in the Allerton collection (Table 2) was a result of a relatively 
high survival of summer litters. Similarly, the comparatively early average birth 
date of rabbits from Jasper County may reflect either low success of summer litters 
or high success of early litters. 
Table 2. Age characteristics of cottontail populations sampled during the fall 
and winter of 1962 - 63 . 
Area 
Numbe r 
of 
Juveniles 
Percent 
Juveniles 
in Sample 
Average Dates 
of Birth of 
Juveniles 
Coefficient of Vari¬ 
ation for Birth 
Date Variance 
(Percent) 
East-central Counties 
83 
91.2 
5/31 + 14 
42.1 
Allerton Sanctuary 
29 
85*3 
6/1 + 19 
33.5 
Neoga Area 
88 
88.9 
5/22 + 12 
41.1 
Jasper County 
45 
83.3 
5/18 + 16 
38.9 
Total 
245 
88.1 
5/26 + 7 
40.5 
