Bottlenose Dolphin Social Structure in the Shannon Estuary, Ireland, Is
MARINE MAMMAL MAMMAL SCIENCE, SCIENCE, **(*): 34(2): ***–*** 458–487 (*** (April 2017) 2018) V©C 2017 Society Society for for Marine Marine Mammalogy Mammalogy DOI: 10.1111/mms.12462 10.1111/mms.12462 Bottlenose dolphin (Tursiops truncatus) social structure in the Shannon Estuary, Ireland, is distinguished by age- and area-related associations ISABEL BAKER1 and JOANNE O’BRIEN , Marine and Freshwater Research Centre, Galway-Mayo Institute of Technology, Dublin Road, Galway H91 T8NW, Ireland and Shannon Dolphin and Wildlife Foundation, Merchants Quay, Kilrush V15 E762, County Clare, Ireland; KATHERINE MCHUGH , Sarasota Dolphin Research Program, Chicago Zoological Society, ℅ Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, Florida 34236, U.S.A.; SIMON N. INGRAM2 ,School of Biological, Earth and Environmental Sciences, University College Cork, Cork, Ire- land; SIMON BERROW , Marine and Freshwater Research Centre, Galway-Mayo Institute of Technology, Dublin Road, Galway H91 T8NW, Ireland and Shannon Dolphin and Wildlife Foundation, Merchants Quay, Kilrush V15 E762, County Clare, Ireland. Abstract Social and network analyses that incorporate information on individuals within a population enhance our knowledge of complex species. In this study, the social struc- ture of wild bottlenose dolphins in the Shannon Estuary, Ireland, was analyzed by examining the dynamics of the whole population and then of individuals classed by sex, age, and area. One hundred and twenty-one dolphins were identified during 522 sightings between 2012 and 2015. The mean half-weight association index (HWI) of the population was 0.07 Æ 0.02. The highest HWIs for individuals of known sex were for female-male pairs. Mean within-class HWI was significantly higher than mean between-class HWI for both age and area classes.
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