THE EFFECT OF TEMPERATURE AND PHOTOPERIOD ON THE YEARLY HIBERNATING BEHAVIOR OF CAPTIVE GOLDEN-MANTLED GROUND SQUIRRELS (CITELLUS LATERALIS TESCORUM)

Abstract

The state of torpidity (hibernation), the food consumption, and the weight of a number of C. lateralis were recorded daily, weekly, and weekly, respectively, for periods up to 2 years. At ambient temperatures of 32° F, 70° F, and 95–100° F and under constant lighting conditions, all animals displayed an approximately 1-year cyclic variation in weight which roughly paralleled the consumption of food. Under these constant conditions of light and temperature the animals subjected to 32° F and 70° F hibernated, i.e., their body temperature dropped nearly to the ambient and they became torpid. The body temperature of animals kept at 95–100° F could not drop and these animals did not become torpid.Hibernation could not be induced by removal of food but was greatly prolonged if food was not present in the cages at the time the whole hibernation period was ending. The onset of hibernation could be changed only slightly by changing the day lengths. Hibernation was possible only at a specific stage of the weight cycle. The length of the weight cycle was shortened by exposure to an ambient temperature of 95–100° F. By manipulation of the length of the exposure to the high temperature it was possible to have animals hibernating in summer and active in winter. It was not possible to produce a similar shift in the phase of the weight cycle, and hence of hibernation, by changing the lighting conditions.