Social structure of Indo-Pacific bottlenose dolphins (Tursiops aduncus) off the south coast of Zanzibar
(English)Manuscript (preprint) (Other academic)
The social structure of Indo-Pacific bottlenose dolphins (Tursiops aduncus) resident in Menai Bay, Zanzibar, east Africa, was investigated using group characteristics and association records collected 1999-2002. On average, groups were large compared to those reported from other bottlenose dolphin studies. Groups were also significantly larger when the dolphins exhibited socializing behavior or when calves were present, indicating that large groups could be attributed to social benefits related to reproduction and caring for calves. To investigate relationships between identified individuals, an association analysis was performed using half-weight association indices (HWIs), calculated for 67 well-marked individuals sighted 9 or more times. While the overall distribution of HWIs was skewed towards lower values, relationships were stronger and more long-term than would be expected if dolphins were associating at random. A temporal analysis, performed to model the stability of associations, suggested that these relationships may last for as long as 7 years. Multidimensional scaling and cluster analysis revealed two female clusters and a male pair that had high HWIs across all years of sampling. These preferred relationships may be formed to obtain reproductive benefits as well as safety against predators and other threats. For example, the dolphins in Menai Bay are subject to anthropogenic threats from fishing and tourism activities in the area. Unless kept at a sustainable level, such threats could ultimately disrupt the long-term relationships observed in the present study and adversely influence the health of the population.
social structure, group characteristics, association indices, bottlenose dolphins, Tursiops aduncus
Research subject Animal Ecology
IdentifiersURN: urn:nbn:se:su:diva-60530OAI: oai:DiVA.org:su-60530DiVA: diva2:435671