Bottlenose dolphins (Tursiops spp.) are amongst the best studied cetacean species in the world. Extensive research has been carried out on their vocalisations, which generally fit into three categories: tonal whistles, and broadband burst-pulsed sounds (BPS) and echolocation clicks. Whistles and BPS are predominantly used for communication, while echolocation clicks are principally used during foraging and for orientation. However, despite the wide range of research on whistle use in bottlenose dolphins, the functionality and contextual use of whistles is still poorly understood, particularly in wild populations. There has also been limited research carried out on BPS.

Bottlenose dolphins use individually distinctive whistles known as “signature whistles”, which are developed in the first year of life and stay stable for many years, possibly a lifetime. These are thought to be used for individual identification and group cohesion. It is also likely that signature whistles contain information about an individual’s motivational state and arousal level (flexible information). However, much of the information on signature whistles has come from captive studies, as it is very difficult to identify vocalising individuals in the wild. In addition to signature whistles, dolphins produce non-stereotyped “variant” whistles which are shared between group members, the function of which is poorly understood.

This project aims to build on the current knowledge of bottlenose dolphin acoustic communication using what has been learned from captive studies. The study will also aim to test for the presence of flexible information within the dolphins’ social sounds by identifying changes in vocal parameters in relation to changes in behavioural states.

Since 1992 a group of wild Indo-Pacific bottlenose dolphins (T. aduncus) have regularly been provisioned on a beach at the Tangalooma Island Resort on Moreton Island (Queensland, Australia) as part of a tourist attraction. Currently there are 11 animals in the program, including adults and young calves. Prior to the provisioning, the dolphins spend some time socialising in the shallow water adjacent to a nearby jetty. They arrive at the same time every night allowing for a hydrophone array to be set up in anticipation of their arrival. Using a hydrophone array, the location of the sound can be identified, a process that is very difficult in wild populations. While the dolphins’ vocalisations are being recorded, simultaneous video footage, photo-identification (photo-ID) images and behavioural data are also collected, allowing for identification of vocalising individuals and a comparison with behavioural states.

Boat surveys will be conducted in Moreton Bay to collect behavioural, acoustic and photo-ID data from these 11 dolphins in a non-provisioning context to allow for comparison with the previously collected data. In addition, similar data will be collected from other, non-provisioned free-ranging bottlenose dolphins encountered in Moreton Bay. A custom-built hydrophone array will be deployed around a group of dolphins to attempt to localise whistles and assign them to individual animals while recording behaviours and taking photo-ID images.

Katya Ovsyanikova, who joined the lab in 2016, will describe the repertoire of the 11 individual dolphins and identify each individual's signature whistle. She will investigate the contextual use of these whistles during provisioning and compare it with their use outside of the provisioned setting. Barry McGovern, who joined the lab in 2017, will use the signature whistles to test for the presence of flexible information within the dolphins’ social sounds by comparing whistle parameters during different behavioural states. He will also aim to describe BPS use in different social contexts. He will then take this information and explore whether these results are also evident in the rest of the bottlenose dolphin population in Moreton Bay. Léonie Huijser, who joined the lab in 2018, will establish an overall whistle repertoire for the Moreton Bay population and investigate the use of signature whistles in different behavioural and social contexts as well as the role of variant whistles. She will also assess social structure among the population using photo-ID and interaction data.