Abstract

Animal societies organised as colonies gain a variety of fitness benefits, and consequently colonial behaviour has evolved amongst avian, mammalian and invertebrates species, but far less is known for fish. Using dynamic social networks, we document highly structured sociality in central place foraging grey reef sharks at a Pacific atoll, with sharks forming stable, social groups over multi-year periods. Individuals were highly assorted by their patterns of space use, with specific paired dyadic associations consistent across years. We demonstrate high within-colony reciprocity of leadership roles in departure times of dyads from core areas, relative to between colony dyadic associations. We provide evidence of colonial behaviour in elasmobranch fishes, underpinned by conditions under which we would expect foraging via social or public information exchange to persist. Our models also suggest that social foraging with information transfer could drive central place foraging and colonial behaviour without the requirement for reproductive mechanisms.