Calling up ghosts: acoustic playback of social vocalisations reveals complex communication in a cryptic bat and provides a promising tool for monitoring disturbance-sensitive species

Abstract

Conservation is particularly challenging for species that are highly sensitive to disturbance and negatively affected by monitoring procedures. Australia’s ecologically and culturally significant ghost bat (Macroderma gigas) has suffered substantial population declines, in part due to disturbance and loss of roost sites. This sensitivity poses impediments to studies of the ghost bat’s ecology and behaviour, which in turn inhibits evidence-based conservation and management of the species. We used full-spectrum acoustic playback, in combination with thermal video recordings and netting, as a novel method to investigate the behavioural ecology of this enigmatic bat. We tested whether ghost bats are responsive to conspecific social vocalisations and, if so, whether responses differ according to signaller and receiver characteristics. Individuals were attracted strongly to two of four vocalisation types, and responses depended on sex, thus providing the first experimental evidence that the ghost bat’s complex vocal repertoire has multiple functions. Responses did not differ with geographic location, indicating that our method can be used across the species’ range. We discuss how full-spectrum acoustic playback helps improve our knowledge of the behavioural ecology of this species and highlight the applicability of our methods for targeting specific conservation needs in bats.