Vol . 7, No. 9 
Page 5 
6. Rabbit Management J. A. Bailey 
Although the number of rabbits present in early March on the Allerton Park 
4-H Area has varied from year to year (Monthly Wildlife Research Letter, August, 
19^4), we have not been able to detect a statistically significant difference 
among the fall population estimates (Table 3)- There is no significant difference 
among the estimates of fall population density for the first 6 years of this study; 
these are estimates of the population density in early October. Because of a 
change in the census technique, the estimates made in 1962 and 1963 are more 
appropriate for the population density in mid-November and hence can not be compared 
with the earlier estimates. 
The data suggest that the maximum population of rabbits on the 4-H Area is 
about the same each year, despite the fact that overwintering success may vary 
considerably. If this is true, potent density-dependent mechanisms must be 
involved in the natality and/or mortality rates during the summer. Only five rates 
of population gain can be calculated from these data (Table 3)- When graphed over 
the spring population estimates, these points suggest a negative geometric curve 
such as Errington (1957) found in rates of population gain for marsh-dwelling 
muskrats. Errington described density-dependent population phenomena in several 
of his papers on muskrats. It would not be surprising if most of his theories also 
applied to rabbits. 
Of considerable interest in this regard were our recent discussions with 
research workers in Missouri. The Missouri biologists are studying the physiology 
of stress-related mortality of rabbits in high-density populations. It appears 
that some mechanism inherent in the physiological-psychological nature of this 
species can respond to the relationship between habitat quality and population 
density by increasing the mortality rate of at least some segment of the population. 
In this manner, a rather delicate balance between habitat quality and population 
density can be maintained. 
Errington 
Table 3- 
Park 4-H 
, P. L. I 957 . Of population cycles and 
Symposia on Quant. Biol. 22:287 
Estimates of rabbit abundance and rates 
Area. 
unknowns. Cold Spring Harbor 
- 300 . 
of population gain on the Allerton 
Rate of 
Spring Popu 
1 at ion 
Fa 1l Popu 1 
at ion 
Populat ion Gain 
Year 
March 
Early October 
Mid-November 
(Percent) 
1956 
333 
1957 
47 
259 
— 
451 
1958 
31 
324 
— 
945 
1959 
132 
239 
— 
81 
I 960 
56 
309 
— 
452 
1961 
161 
363 
— 
125 
1962 
24 
— 
107 
— 
1963 
61 
— 
1 32 
— 
1964 
58 
— 
— 
— 
