The acoustic ecology of the Ghost Bat (Macroderma gigas) : form, function and applied uses of vocalisations

Abstract

The ghost bat (Macroderma gigas) is a large, carnivorous echolocating bat endemic to Northern Australia. The species resembles no other bat in the world, weighing 150 g with distinctive pale fur, large ears and noseleaf, and translucent wings, measuring 60 cm across, that inspired its common name. The ghost bat's population is in decline, likely as a result of roost disturbance by human visitors and destruction of roost habitats by mining. Little is known about ghost bat ecology and behaviour, and this lack of information hinders the application of effective conservation management actions. Studies of the ghost bat are complicated by the species' extreme sensitivity to roost visitation, which can readily cause roost abandonment and mortality. The ghost bat is a highly vocal species with a number of documented social vocalisations of unknown function. I hypothesised that the ecology and behaviour of the ghost bat could be studied through the medium of their social vocalisations. For my thesis, I collected acoustic and behavioural data from across the ghost bat's range in the Northern Territory, Australia, over a period of three years. I conducted playback experiments, phylogenetic analysis, and captive species observations to investigate the acoustic ecology of the ghost bat and examine how the species' acoustic behaviour could be used to help conserve this threatened bat. My thesis provides the most in-depth insight into the acoustic ecology of the ghost bat to date, with the creation of a permanent database of the ghost bat's complex vocal repertoire and an ethogram of solitary and social behaviours with associated vocalisations, demonstrating the functional complexity of the ghost bat's communication system. In particular, I provide the first evidence of song in the repertoire of the ghost bat and the first record of mobbing behaviour in this species. My study adds to the depauperate knowledge on dialects in bats, demonstrating how geographic isolation can result in structural changes of social vocalisations due to drift. Importantly, I trialled and demonstrated the applicability of social vocalisations as proxies for non- vocal behaviour and the use of acoustic playback to study and capture ghost bats away from the roost. I hope that the insights in this thesis positively affect the conservation outcome for the ghost bat and enable the collection of the necessary information to design effective conservation plans without causing further detrimental impacts to at-risk colonies.

Date of Award	2020
Original language	English