Bottlenose dolphin vocal communication

: drivers of whistle variation and the utility of identity signals to inform conservation

Abstract

Vocal communication is widespread in the animal kingdom and is of particular importance for long-range signalling in aquatic species due to environmental constraints on other sensory modalities. For species highly reliant on vocal signalling, it is pertinent to understand the natural and anthropogenic pressures exerted on their vocalisations and the potential for vocal adaptations to maintain communication ranges in a changing world. In this thesis, I investigate short and long-term drivers of whistle variation in bottlenose dolphin (Tursiops spp.) populations and the utility of passive acoustics to inform their conservation. Firstly, I examine mechanisms of vocal behavioural plasticity in response to ambient noise and vessel traffic in T. truncatus (Chapter two). I show that dolphins exhibit vocal plasticity of individual whistle types and that individual whistle types are repeated more often when vessel traffic is greater. Secondly, I examine the Acoustic Adaptation Hypothesis (AAH) in T. aduncus in Shark Bay, Western Australia (Chapter three). The AAH posits that vocalisations will be adapted to maximise their transmission in the species’ habitat. In accordance with the AAH, I show that habitat structure leads to heterogeneous sound propagation which, in turn, shapes the structure of whistles in this population. Combined, these chapters illustrate vocal adaptations to the acoustic habitat at multiple scales, through behavioural modification and long-term selection. Finally, I investigate the use of individually distinctive whistles, termed signature whistles, for tracking individual movements of T. truncatus in Cardigan Bay, Wales (Chapter four). I use signature whistles to assess movements of individuals and estimate the size of the population using a protected area. Collectively, my findings illustrate the utility of passive acoustic methods to inform us about natural and anthropogenic drivers of whistle variation and to contribute to the conservation and management of bottlenose dolphins.

Date of Award	4 Feb 2025
Original language	English
Awarding Institution	University of Bristol
Supervisor	Stephanie L King (Supervisor)