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Multi year social stability and social information use in reef sharks with diel fission-fusion dynamics: Raw acoustic detection

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Oct 22, 2020 version files 107.50 MB

Abstract

Animals across vertebrate taxa form social communities and often exist as fission-fusion societies. Central place foragers (CPF) may form social groups, from which they will predictably disperse to forage, either individually or in smaller groups, before returning to fuse with the larger group. However, the function and stability of social associations in predatory fish acting as CPFs is unknown, as individuals do not need to return to a shelter, yet show fidelity to core areas. Using dynamic social networks generated from acoustic tracking data, we document spatially structured sociality in CPF grey reef sharks at a Pacific Ocean atoll. We show that sharks form stable, social groups over multi-year periods, with some dyadic associations consistent for up to four years. Groups primarily formed during the day, increasing in group size before sharks dispersed from the reef to forage at night. Our simulations suggest that multiple individuals sharing a central place and using social information while foraging (i.e. local enhancement), will outperform non-CPF social foragers. We show multiyear social stability in sharks and suggest that social foraging with information transfer could provide a generalisable mechanism for the emergence of sociality with group central place foraging.