Social and Behavioural Characteristics of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in northern New South Wales, Australia.

Abstract

Bottlenose dolphins (Tursiops spp.) are one of the most common genera of cetacea encountered throughout the world?s tropical and temperate regions. However, there is relatively little knowledge on the populations of bottlenose dolphins in Australia. The present study assessed the pod characteristics, behaviour, movement patterns and social structure of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in coastal inshore waters off northern New South Wales, Australia, using vessel-based and land-based surveys. Dolphins spent most time travelling (38%), followed by milling (31%), feeding (19%), and socialising (12%). The mean pod size of dolphins in Byron Bay was 13 (S.D. = 12). The social foundation of this population was characterised by sexual segregation. Significant variations were found between the mean size of mother-calf pods (21; S.D. = 15) and adult-only pods (5; S.D. = 5). Two ?resident? groups of females were identified that occupied adjacent territories of between 177 km² and 320 km². ?Resident? females appeared to maintain loose associations with other ?resident? females (HWI = 0.28; S.D. = 0.66). Despite the large differences in environmental conditions, habitats and prey species, it appeared that the social organisation, movement patterns and behaviour of T. aduncus populations in coastal regions is similar. The Byron Bay population of dolphins is not presently heavily impacted by interactions with humans, compared to populations with regular commercial dolphin-watching operations. This means the population may provide important base-line data for assessment of potential human impacts on dolphin populations.