GRILLIOT, ME; BURNETT, SC; MENDONCA, MT; Auburn University, Auburn AL; Clayton College and State University, Morrow, GA: Sex and Seasonal Differences in the Echolocation Signals of Eptesicus fuscus

Ultrasound is a widely used acoustical method for social communication, as well as for navigation and foraging. Although bats are well known for their use of ultrasound for the latter functions, there is presently limited evidence for its use in the former function. Studies have investigated the possibility for sex differences in the echolocation calls of bats. However, there are no studies that have explored its use during courtship and mating. We have a captive colony of big brown bats housed in environmental chambers that allow us to alter temperature and photoperiod in order to mimic seasonal changes and induce mating behavior. This offers us a unique opportunity to investigate potential sex and seasonal differences in the echolocation calls of big brown bats. We recorded the echolocation calls of 17 adult female and 16 adult male big brown bats before and during the mating season. For each bat, I recorded a minimum of 200 calls. I averaged those calls for eight variables (duration, h1start, mid and end, h1maxa, tcmax, curvature, and f10ub) to get a single measure of each variable for each bat. These variables were analyzed for seasonal differences, sex differences, and individual distinctiveness. We found that there were significant differences in call characteristics in males and females between seasons. In addition, we found call duration to significantly differ between the sexes in the mating season. These results suggest there may be seasonal alteration in echolocation signals and this alteration might play a role in sex recognition during mating.