Vermeulen, Els2018-09-182018-07Vermeulen, E. 2018, 'Association patterns of bottlenose dolphins (Tursiops truncatus) in Bahía San Antonio, Argentina', Marine Mammal Science, vol. 34, no. 3, pp. 687-700.0824-0469 (print)1748-7692 (online)10.1111/mms.12481http://hdl.handle.net/2263/66585This study aims to investigate the association patterns of a small and resident population of bottlenose dolphins (Tursiops truncatus) in Bahía San Antonio (Argentina), and assess any seasonal variation in view of the reported seasonal variation in the population's grouping behavior. The estimation of social differentiation (S) was 0.29 (SE = 0.08), suggesting a homogenous society. The half‐weight index (HWI) averaged 0.23 (± 0.06), with evidence of long‐term preferred associations. However, data showed seasonal variation in the association patterns. In winter, when large groups were reported in this population, HWI values averaged 0.30 (± 0.09) with no indication of preferred or avoided associations. However, during summer, when group size was generally small, HWI values averaged 0.14 (± 0.07), with an indication of preferred/avoided associations. This study indicates that the social structure of the bottlenose dolphins in Bahía San Antonio seems relatively homogenous and flexible over time, with the formation of a random social network at times when large aggregations are formed, and a more disconnected network made up of strongly connected components when the cost of grouping is high.en© 2018 Society for Marine Mammalogy. This is the pre-peer reviewed version of the following article : 'Association patterns of bottlenose dolphins (Tursiops truncatus) in Bahía San Antonio, Argentina', Marine Mammal Science, vol. 34, no. 3, pp. 687-700, 2018, doi : 10.1111/mms.12481. The definite version is available at : http://onlinelibrary.wiley.comjournal/10.1111/(ISSN)1748-7692.AssociationsBottlenose dolphin (Tursiops truncatus)Fission–fusion societySeasonalitySocial structure;Postprint Article