Evaluating odour and urinary sex preferences in the big brown bat (Eptesicus fuscus)

Olfactory cues provide detailed information to mammals regarding conspecifics. Bats may identify species, colony membership, and individuals using olfaction. Big brown bats (Eptesicus fuscus (Palisot de Beauvois, 1796)) live in mixed-sex colonies and must differentiate between sexes to locate mates. We hypothesized that odour cues convey information about sex. In experiment 1, adult E. fuscus were recorded exploring a Y-maze that contained general body odours sampled from male or female conspecifics. One group of subjects was habituated to the Y-maze prior to experimental trials, whereas a second group was not. Bat exploration and the proportion of time spent near each scent were used as preference indicators for the body odour of a particular sex. Experiment 2 followed similar procedures except the odour cue tested was urine from either male or female conspecifics and without Y-maze habituation. Results found no evidence that E. fuscus prefer the body odours of a given sex, but females did prefer the odour of male urine. Non-habituated animals in experiment 1 were more likely to explore the Y-maze and approach a stimulus scent compared with habituated bats. These findings have important implications for courtship and mating behaviour in bats, as well for designing future behavioural studies.