Ethogram of Ghost Bat (Macroderma gigas) Behaviours and Associated Social Vocalisations

Abstract

The ghost bat (Macroderma gigas) is a carnivorous species of bat endemic to northern Australia that roosts in colonies of up to 1,500 individuals. The ghost bat produces a number of social vocalisations, but little is known about the species' behaviour and what role social vocalisations play in interactions between conspecifics. The aim of this study was to construct an ethogram of ghost bat behaviours and to determine the associations between behaviours and social vocalisations. To achieve our aims, we filmed the behaviour of a captive ghost bat colony (one male, five females) using four trail cameras installed within the enclosure over a six-week period, coinciding with the estimated mating season. Video recordings were examined by eye, and solitary and social behaviours were catalogued into distinct behavioural units (e.g. hang-alert, chew, wing-groom, etc.) along with social context and associated social vocalisations, if applicable. To assess the associations between behavioural interactions and social vocalisation types, we combined each of the catalogued social behavioural units into six behavioural classes (eating, grooming, mating, huddling, flying, and fighting) and used generalised linear models to determine which social behavioural classes significantly predicted the production of each vocalisation. There was a strong association between flight behaviour by a member of the colony and the production of the ‘Chirp-trill’ vocalisation by the male member of the colony, suggesting a territorial or mate attraction function. There was also a strong association between fighting behaviour and the production of the ‘Squabble’, ‘Rasp’ and ‘Grumble’ vocalisations, with the Squabble and Rasp likely representing levels of agonistic vocalisations produced by aggressive bats during altercations. The Grumble, on the other hand, was produced by the target of the aggressor and so may function as an appeasement call. The ethogram with its associated social vocalisations provides a formal basis for future behavioural studies in this species and can serve as a template for such studies in other echolocating bats. Our study revealed an unexpected degree of complexity in the behaviour and associated vocalisations in this species and highlights the need for studies of this kind in other bats.