Doctor Nicola Hanrahan

Candidature

Graduated PhD 2021

Thesis Title

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

Research Project

The field of acoustic ecology has been dedicated predominantly to the study of vocalisations of birds and cetaceans. Bats, despite evidence that they are capable of producing repertoires of calls comparable to birds, have had research restricted to studies on echolocation. The study of non-echolocation vocalisations is a relatively new area in echolocating bats, and has been restricted to few species focussing mainly on vocalisations used in territoriality and mother-young interactions. Interesting areas of study are beginning to emerge, which so far has received very little attention. These areas include dialect formation, singing, and alarm calling by bats.

The ghost bat (Macroderma gigas) is a large echolocating bat found in tropical and sub-tropical areas of northern Australia. M. gigas lives in caves or disused mine shafts and congregates in large colonies. They are highly social and have a range of vocalisations that we know nothing about. Due to continuing population declines M. gigas was recently added to the threatened species list (EPBC Act). The threatening processes affecting the ghost bat are still unclear and this is due to a lack of knowledge on the social organisation of this species. I aim to address this knowledge gap by studying the social structure, behaviour and movement of M. gigas through their vocalisations produced within the roost and while out foraging.

My study on the acoustic ecology of M. gigas aims to address the following overarching question, 'What is the form and function of non-echolocation vocalisations?' I will categorise vocalisation types according to structure, environmental context and signaller, assess temporal variation within these vocalisation types and investigate if geographical variations occur and if so, how these dialects came about. Finally, using the information collected, I will determine the function of each of the vocalisations using playback and behavioural experiments. In addition, I aim to use the knowledge gained about the form and function of vocalisations to develop better bat monitoring practices based on passive recordings and acoustic lures, and so help improve the conservation management of bats in Australia and beyond.

Publication

Hanrahan N, Dalziell AH, Turbill C, Armstrong KN, Welbergen JA, (2022) 'Ethogram of ghost bat (Macroderma gigas) behaviours and associated social vocalisations', Acta Chiropterologica, vol.24, no.1, pp 195-208

Supervisors

Dr Justin Welbergen, Dr Christopher Turbill, Dr Kyle Armstrong, Dr Anastasia Dalziell