MENDON�A, , M.T.: Effects of temperature on mating discrimination in male big brown bats

Previous experiments in our laboratory have explored the role of temperature in stimulating mating in male big brown bats. Changes in temperature have been found to modulate the frequency of mating behavior. Although males will continue to mate even when kept at constant 22 C during the mating season (Dec-Feb), mating frequency increases threefold if these animals are exposed to 5 C for 7 d and then returned to 22 C. While exposing males to differing regimens, we noted that intact males occasionally mounted other males as well as females and the frequency of this occurring varied with temperature regimen. In Jan-Mar 2000, intact males were divided into 3 temperature regimens: constant 22 C (CONSTANT), repeated exposures of 5 C for 7 d (LONG) or 5 C for 1 d (PULSE) with intervals of 22 C for 4 d. We recorded the sex of the bat a male mounted and then catagorized males as Female only/Female predominant mounters (>60% of mounts were of a female), Equal Predominance mounters (40-60% of mounts female), or Male Predominant mounters (<40% of mounts female). Significantly more LONG males mounted females than had equal preference (80 vs 20%). No male in the LONG treatment predominately mounted males. Significantly more PULSE males mounted females but some were found predominately mounting males (10%). CONSTANT males tended to mount males predominately (55%, p=0.061). Only 20% of CONSTANT males mounted females predominately. In Jan-Feb, 2001, we again had similar temperature manipulations and found similar patterns (e.g. males kept at repeated exposures to 5 C for 10 d - VERY LONG - were all scored as Female only/predominately female mounters). These data will be discussed in light of possible pheromonal or hormonal differences caused by temperature.