Effects of temperature on the duration of arousal episodes during hibernation.

The length of time that the ground squirrels Spermophilus beldingi and S. lateralis remained at high body temperatures following periodic arousals from hibernation increased as environmental temperature increased over the range of 5-20 degree C. This trend was evident in comparisons among different animals that hibernated at different temperatures and in individuals that hibernated at different temperatures in successive years. At any one temperature, the duration of these euthermic intervals in S. beldingi was correlated with body size. Large adult males remained at high body temperatures longer than adult females, which in turn remained euthermic longer than small juveniles. In addition, these squirrels spent less time at high body temperatures following bouts of torpor that were interrupted prematurely by environmental disturbances. These results are consistent with an amplify the theory that arousals are initiated by, and necessary for the elimination of, some chemical imbalance, which develops while hibernators metabolize at low body temperatures.