Mendon�a, M. T.: Effects of temperature, testosterone, and flutamide on mating in male big brown bats
Male big brown bats exhibit a dissociated pattern of reproduction. They mate in the late fall and throughout the winter upon periodic arousal from hibernation when testosterone (T) is basal and gonads are regressed. In previous experiments, males mated even when gonadectomized (GX) several months before the beginning of the mating season, if they are exposed to an initial period of 5 C for 7 d and then allowed to return to 22 C. However, GX males given flutamide (F) did not mate until the very end of the test period (Mar, 1999). In Jan-March 2000, we continued to examine the interactions of temperature and T on male mating behavior. Males were divided into 5 groups: INTACT, SHAM, GX, GX+T, and GX+F. Males from each group were divided into 3 temperature regimens: constant 22 C (CONSTANT), repeated exposures of 5 C for 7 d (LONG), and repeated exposures to 5 C for 1 d (PULSE) with returns to 22 C for 4 d. Based on previous data, we predicted males not exposed to low temperature (CONSTANT) would not exhibit mating behavior. Contrary to prediction, males of all treatment groups (including GX+F) exhibited mating behavior when exposed to CONSTANT. However, INTACT males exposed to LONG exhibited significantly higher levels of mating behavior than INTACTs exposed to PULSE or CONSTANT conditions. Additionally, when, after 2 months, the CONSTANT group was given LONG exposure, males from all treatment groups exhibited significantly higher levels of mating. This result argues that exposure to low temperatures for a period of time does potentiate mating behavior in males of this species. Especially intriguing was the behavior of the GX+F groups. The CONSTANT GX+F males exhibited significantly much higher mating scores than those in the PULSE and LONG condition. Thus, it appears flutamide is ineffective at blocking mating behavior at higher temperatures but seems effective when animals are exposed to either short or long periods of low temperature with subsequent warming.
