Abstract
Within-species variation in social structure has attracted interest recently because of the potential to explore phenotypic plasticity and, specifically, how demographic and ecological variation influence social structure. Populations of bottlenose dolphins (Tursiops spp.) vary in male alliance formation, from no alliances to simple pairs to, in Shark Bay, Western Australia, the most complex nested alliances known outside of humans. Examination of ecological contributions to this variation is complicated by differences among populations in other potentially explanatory traits, such as phylogenetic distance, as well as female reproductive schedules, sexual size dimorphism, and body size. Here, we report our discovery of systematic spatial variation in alliance structure, seasonal movements and access to mates within a single continuous social network in the Shark Bay population. Participation in male trios (versus pairs), the sizes of seasonal range shifts and consortship rates all decrease from north to south along the 50 km length of the study area. The southern habitat, characterised by shallow banks and channels, may be marginal relative to the open northern habitat. The discovery of variation in alliance behaviour along a spatial axis within a single population is unprecedented and demonstrates that alliance complexity has an ecological component.
Highlights
Within-species variation in social structure has attracted interest recently because of the potential to explore phenotypic plasticity and, how demographic and ecological variation influence social structure
We have shown that 1st-order alliance size, consortship rate and seasonal ranging of male bottlenose dolphins vary systematically along the Peron Peninsula in the eastern gulf of Shark Bay
We know of no model of random demographic or cultural variation that could yield systematic spatial variation in alliance structure and the rate that males consort females and, assume a model based on the economics of male mate acquisition and defence under varying ecological conditions
Summary
Within-species variation in social structure has attracted interest recently because of the potential to explore phenotypic plasticity and, how demographic and ecological variation influence social structure. We report our discovery of systematic spatial variation in alliance structure, seasonal movements and access to mates within a single continuous social network in the Shark Bay population. The strength of phylogenetic signals in such comparative analyses[4,5] refocused attention on intraspecific variation in social systems, which cannot be attributed to phylogeny[6,7,8,9,10]. While intraspecific variation in social systems is found in a range of taxa, mammals are especially attractive subjects because of their ‘extremely broad range of social systems, behavioural flexibility, brain size and cognitive abilities’[9]. Unexamined, is how variation in ecology impacts the complexity of social relationships, such as alliance formation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
