Data from: Genetic relatedness delineates the social structure of southern Australian bottlenose dolphins

Social relationships represent an adaptive behavioural strategy that can
provide fitness benefits to individuals. Within mammalian societies,
delphinids are known to form diverse grouping patterns and show a variety
of social systems. However, how ecological and intrinsic factors have
shaped the evolution of such diverse societies is still not well
understood. In this study we used photo-identification data and biopsy
samples collected between March 2013 and October 2015 in Coffin Bay, a
heterogeneous environment in South Australia, to investigate the social
structure of southern Australian bottlenose dolphins (Tursiops cf.
australis). Based on data from 657 groups of dolphins we used generalized
affiliation indices, and applied social network and modularity methods to
study affiliation patterns among individuals and investigate the potential
presence of social communities within the population. In addition, we
investigated genetic relatedness and kinship relationships within and
between the communities identified. Modularity analysis revealed that the
Coffin Bay population is structured into two similar sized, mixed-sex
communities which differed in ranging patterns, affiliation levels and
network metrics. Lagged association rates also indicated that non-random
affiliations persisted over the study period. The genetic analyses
suggested that there was higher relatedness, and a higher proportion of
inferred full-sibs and half-sibs, within than between communities. We
propose that differences in environmental conditions between the bays and
kinship relationships are important factors contributing to the
delineation and maintenance of this social structure.