Association Patterns of Indo-Pacific Bottlenose Dolphins (Tursiops aduncus) in Waters off the North West Cape, Western Australia

This study examined association patterns, social clustering, and temporal stability of Indo-Pacific bottlenose dolphins off the North West Cape (NWC), Western Australia. Over 6 years, boat-based surveys collected photo-identification data, enabling repeated sampling, sighting history construction, and associate identification. Among the 344 adult dolphins identified, 116 were sighted at least five times and used in association analyses. A strong correlation (r = 0.86 ± 0.01 SE) between true and estimated association indices, along with a high coefficient of variation (S = 1.92 ± 0.9 SE), indicates a highly differentiated society with diverse relationships among individuals. Generalized affiliation indexes, social network metrics, and lagged association rates revealed predominantly loose, short-term associations within a well-connected but non-clustered social network. These fluid association patterns are likely related to the open and transient nature of this population, where individuals move in and out of the study area. These movements provide opportunities for social interactions among different individuals, and members of different groups may fission for varying periods of time. Findings from this study provide a solid baseline for future studies looking at the sociogenetic structure of this population and the environmental and social factors driving their fluid social system.