Vol. 5, No. 3 
Page 3 
Adult hens released on the Neoga area prior to the 1961 breeding season aver¬ 
aged 972 + 14 grams in weight, while adult hens reared on the area weighed less, 
averaging 913 + 18 grams. Average weight of adult hens in South Dakota during 
October and November, 1946, was 965 grams. The differences between the mean weights 
of adult hens released on the Neoga area and adult hens reared on the area were 
significant at the 95 per cent level when tested by Student's t test. These 
differences between the mean weights of adult hens released on the area and those 
reared on the area suggest that (1) adult hens reared on the area may be suffering 
from a nutritional deficiency, (2) survival among smaller hens reared on the area 
may be greater than among larger hens reared on the area, or (3) the differences 
in body weights may be due to the small sample sizes involved. 
4. Rabbit Management Glen C. Sanderson, D. A. Casteel 
The census drives, held March 11 on the Robert Allerton Park study areas, 
showed a population of 24 rabbits on the 4-H area compared to a prehunting season 
population of 363 rabbits. The probability of dying statistics for the 4-H area for 
the past 6 seasons are shown in table 2. 
Table 2.--Probability of dying statistics for the 4-H area, 1956-62. 
Season 
Fall 
Population 
Spring 
Population 
Probability 
of Dying 
1956-57 
333 
47 
.858 
1957-58 
259 
31 
.830 
1958-59 
324 
132 
.592 
1959-60 
239 
56 
.765 
1960-61* 
309 
162 
.475 
1961-62 
363 
24 
.934 
* No hunting during this season. 
The 1961-62 season had the highest probability of dying and the smallest winter 
carry over in the past 6 years. The 1961-62 figures are especially striking when 
compared with those of 1960-61 when hunting was not permitted on the area and the 
lowest probability of dying and highest carry over resulted. During the 1961-62 
season, 46 per cent of the fall rabbit population was bagged by hunters. A previous 
study of crippling losses indicated that at least an additional 10 per cent of the 
fall rabbit crop is lost through crippling. Thus, a mortality rate of approximately 
56 per cent can be attributed to hunting on the 4-H area in 1961-62. Other mor¬ 
tality factors presumably accounted for the remaining 37 per cent of the fall popu¬ 
lation which died prior to the spring census. 
When the 4-H area was closed to hunting during the 1960-61 season, 47.5 per 
cent of the fall population died due to natural causes. Even though the total 
mortality rate for 1961-62 was 93 per cent of the fall population, only 37 per cent 
