RESPONSES OF BATS FROM TEMPERATE REGIONS TO CHANGES IN AMBIENT TEMPERATURE

Abstract

1. Responses to upward and downward changes in ambient temperature from 5° C. were studied in dormant bats of the species E. fuscus, P. subflavus, M. sodalis, M. lucifugus and L. borealis. Rectal temperatures and heart rates were recorded. 2. Except for L. borealis which did not arouse until ambient temperature reached about 20° C., all species responded by arousal from dormancy when the temperature was increased to 15° C. 3. The effects of decreasing ambient temperature varied considerably among species. E. fuscus invariably aroused from dormancy. L. borealis never aroused but showed a thermoregulatory response by increasing its metabolism to compensate for the increase in heat loss. The responses of the other species depended upon the abruptness of the temperature change. Abrupt lowering of ambient temperature tended to induce arousal in M. lucifugus and M. sodalis, whereas these species responded similarly to L. borealis when exposed to gradually decreasing temperature. P. subflavus usually aroused in response to a gradual decrease in ambient temperature, but seemed unable to arouse in response to abrupt lowering of temperature. 4. Bats of the species L. borealis, M. lucifugus and M. sodalis supercooled to -5° C. showed cessation of breathing, but slow heart beats continued for several hours. Passive rewarming was necessary for survival. 5. Many of the known differences in the ecology of the studied species of bats are reflected as differences in their response to changes in ambient temperature in the laboratory.