Life history, behaviour and social structure of bottlenose dolphins (Tursiops truncatus) in the Shannon Estuary, Ireland

Abstract

Bottlenose dolphins are a complex intelligent species with great diversity and variability in behaviours and social systems across populations, but site-specific information on many aspects of the bottlenose dolphin population in the Shannon Estuary was previously limited or unavailable. The major objectives of this research were (1) to determine baseline reproductive parameters for bottlenose dolphins in Ireland; (2) to establish a full suite of observed behaviours; (3) to better understand the social structure of the population; and (4) to explore dolphin sociality at an individual level. By combining photo-identification and sightings data with novel data collection methods using focal follows, these questions could be addressed. This thesis is divided into six chapters: an introductory chapter (Chapter 1) outlining the research background, four analytical chapters written as scientific manuscripts, and a discussion which reflects on the results of these studies and outlines proposals for future research. The first data chapter (Chapter 2, Manuscript I) presents female reproductive parameters for the first time, together with new population demographics. Chapter 3 (Manuscript II) presents the first ethogram for dolphins in Ireland, validates its use using a video test, and presents new data on activity states and behavioural events. Chapter 4 (Manuscript III) analyses the social structure of the population, revealing age- and area-related associations and demonstrating the presence of long-term associations. Chapter 5 (Manuscript IV) investigates fine-scale sociality from the first focal follows of dolphins in Ireland, revealing female-male affiliations and the absence of male alliances. The general discussion (Chapter 6) brings together results from Chapters 2-5 to consider their implications and to propose ideas for further research and conservation management. It is essential for understanding diverse complex species that data are gathered and analysed for specific populations. By providing new information and analyses of bottlenose dolphin reproductive rates, behaviour, social structure and sociality in Ireland, this research increases our understanding of bottlenose dolphin populations globally.