Ephemeral Resource Availability Makes Wild Guppies More Social

AbstractSocial companions can aid animals in discovering novel resources, with socially connected individuals often locating food more quickly. However, increased sociality also heightens the risk of harassment and disease. Animals would thus benefit from flexibly switching between social and solitary states in response to resource fluctuations. Whether wild animals do this strategically and successfully remains unclear. We experimentally studied groups of wild guppies (Poecilia reticulata) in a resource-poor environment to test if they adjust their social state after recent experience with relatively unpredictable and short-lived novel food patches. Using individually marked fish, we found that groups exposed to ephemeral food patches significantly increased their time spent social--doubling it--compared to control conditions. Groups with stronger foraging motivation showed greater increases in sociality, and individuals in such groups were more successful in locating food patches thereby realizing greater food intake. In a second field experiment, we show that wild guppy groups similarly increased sociality in response to food odours, suggesting strategic adjustments of sociality rather than mere satiation-driven changes in activity budgets. Our findings thus provide causal evidence that animals can be active engineers, rather than passive recipients, of social foraging benefits, highlighting the adaptive nature of fission-fusion dynamics.