Ephemeral Resource Availability Makes Wild Guppies More Social

Abstract

Resource availability and sociality are tightly coupled. Sociality facilitates resource access in a wide range of animal species. Simultaneously, resource availability may change sociality. However, experimental evidence for resource-driven social changes in the wild, beyond local aggregations at the resource, remains scarce. Moreover, it is largely unclear how potential changes in sociality relate to the social foraging benefits obtained by individual group members. Here, we recorded immediate and prolonged changes in social dynamics following ephemeral food availability in 18 mixed-sex Trinidadian guppies (Poecilia reticulata) groups in natural rainforest pools. Using a counter-balanced within-group design, the social associations within each group was observed before, between and after ephemeral patch availability for two consecutive days. We show that groups increased their time spent socially two-fold following ephemeral food patch, but not control (empty) patch, availability. Groups with stronger foraging motivation, measured as the average proportion of fish feeding, showed a stronger increase in sociality. This resource-induced increase in sociality was still detectable the next day. Increase in the time spent socially by a group also positively correlated with the more frequent arrival at detected food patches for individual members of motivated groups, which, in turn, correlated strongly with individual food consumption. Our study causally demonstrates that changes in ephemeral resource availability can induce rapid, substantial, and prolonged changes in the social dynamics of wild fish and that this change positively correlated with individual foraging success. Further research is needed to investigate whether this social change is a cause or consequence of individual foraging success and why some groups respond more strongly than others.