Meeting Abstract
Colonial or highly social animals may show social stability with animals forming social bonds with the same individuals over multiple years. Often these social associations facilitate reproductive strategies, yet phenomenon of colonial sociality is primarily confined to mammals and birds. Measuring dynamic social associations in wide-ranging marine animals in the wild is a considerable challenge and therefore knowledge of social stability in such animals is largely unknown. We used acoustic telemetry and Gaussian mixture modelling to build social networks for a population of grey reef sharks at a Pacific atoll. Sharks behaved similar to central place foragers, forming daytime groups in small core areas and dispersing over larger areas at night where they increased their activity. Movement networks were used to assign membership of individuals to specific clans which were then shown to be highly socially assorted. Furthermore, the same individuals formed associations over four consecutive years. We built a series of individual based models to determine if social foraging and passive information transfer could drive the formation of such social groups in reef sharks. Models suggest that passive information transfer would provide a large advantage over solitary hunting and that passive information transfer with CPF behavior would be more advantageous than more social foraging without a home range. Our models conform to analyses where we infer social foraging information based on leadership patterns in the acoustic data. We show that ectothermic marine predators can form groups with strong social stability and that potential drivers of group formation may be related to foraging and not reproduction.
