Avoidance of predator chemical cues by bats: an experimental assessment

Abstract

[Predation places selection pressure on the behaviour of organisms, but the effect of predation risk on bat behaviour has gone largely untested. Using a Y-maze, we tested the hypothesis that female big brown bats ( Eptesicus fuscus ) avoid olfactory cues from known predators — raccoons ( Procyon lotor ) and black rat snakes ( Elaphe obsoleta ). These chemical cues are most likely encountered by bats during the assessment of potential roost sites, so avoidance of predator cues could affect roost selection. We found that big brown bats do not avoid cues from raccoon urine and there was a non-significant trend for bats to choose the arm with black rat snake cues. In a second experiment, bats were exposed to olfactory and potentially auditory cues of live black rat snakes. Bats tended to avoid the arm with live snakes, although results were non-significant. This suggests olfactory cues may not be representative of live snakes, or that auditory cues may be more important than olfactory cues for predator recognition. During late spring, female bats often avoid torpor for thermoregulatory or reproductive reasons. Therefore, bats may be alert to the approach of predators and be less responsive to chemical cues compared to other times of the year., Predation places selection pressure on the behaviour of organisms, but the effect of predation risk on bat behaviour has gone largely untested. Using a Y-maze, we tested the hypothesis that female big brown bats ( Eptesicus fuscus ) avoid olfactory cues from known predators — raccoons ( Procyon lotor ) and black rat snakes ( Elaphe obsoleta ). These chemical cues are most likely encountered by bats during the assessment of potential roost sites, so avoidance of predator cues could affect roost selection. We found that big brown bats do not avoid cues from raccoon urine and there was a non-significant trend for bats to choose the arm with black rat snake cues. In a second experiment, bats were exposed to olfactory and potentially auditory cues of live black rat snakes. Bats tended to avoid the arm with live snakes, although results were non-significant. This suggests olfactory cues may not be representative of live snakes, or that auditory cues may be more important than olfactory cues for predator recognition. During late spring, female bats often avoid torpor for thermoregulatory or reproductive reasons. Therefore, bats may be alert to the approach of predators and be less responsive to chemical cues compared to other times of the year.]