SREL Reprint #0007




The Effect of Weather on the Winter Activity of Old-field Rodents


J. 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.

This research was supported by Contract AT (07-2)-10 between the University of Georgia and the U.S. Atomic Energy Commission.



Gentry, 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.




To request a reprint