Effect of Weather on the Winter Activity of Old-field Rodents
B. Gentry and E. P. Odum
Since the establishment of the AEC Savannah River Plant in 1951, extensive
use has been made of the Calhoun trapline technic of sampling small
mammal populations, especially in the study of the abandoned field ecosystem.
Since field rodents (Peromyscus polionotus) being the most
important species) reach a seasonal peak in abundance in winter or early
spring, annual comparisons are best made at this time. However,
weather affects catch at this time and must be considered in estimating
density from trapline data. Warm, cloudy nights result in a larger
catch than cold, clear nights. When the weather remains unchanged
during the 3-night period an “expected” downward trend in
catch occurs, but when the weather changes from clear to cloudy on the
second night, average catch per trapline rises sharply (Fig. 1).
Data from 53 traplines in 41 different fields are graphed to show catch
trends for five major weather conditions. While weather definitely
influenced the 3-night trend and the catch on a given night, the total
catch for the 3-night period was not significantly different under the
five weather conditions; under warm, cloudy conditions the population
was trapped out before the end of the 3-night period, while all three
nights were required to “harvest” the population under cool,
clear conditions. The use of the ratio between first and second
night captures in calculating density, however, is counter-indicated
for the seasonal conditions considered in this paper. Moisture,
as well as temperature and moonlight, may be an important factor in
regulating above-ground activity.
research was supported by Contract AT (07-2)-10 between the University
of Georgia and the U.S. Atomic Energy Commission.
J.B. and E.P. Odum. 1957. The effect of weather on the winter activity
of old-field rodents. Journal of Mammalogy 38:72-77.