Fish experienced with predation take fewer risks and enhance foraging success of naïve conspecifics: a benefit of sociality

Prior experience with predation risk can provide valuable information and influence how prey animals trade-off between food and safety. We examine foraging and refuge use behavior among groups of social goldfish (Carrasius auratus) at risk of predation from little egrets (Egretta garzetta) for groups containing only individuals that previously experienced predators, only naïve individuals, or mixed groups containing both experienced and naïve fish. Groups of all-experienced fish consumed significantly less food than the all-naïve and mixed groups, and spent the least amount of time foraging outside of refuge. Furthermore, within the mixed treatment groups, naïve individuals spent more time foraging compared to experienced group members. In terms of survival, the groups containing all-naïve members experienced the highest mortality, and significantly more naïve fish were captured within the mixed groups. Interestingly, the mixed groups experienced overall mortality rates similar to the less active all-experienced groups, even though the mixed groups foraged more like the all-naïve groups. We found that the mixed groups were able to detect the approaching predator significantly earlier than the all-naïve groups, which may explain this result. Thus, we show that naïve individuals within mixed groups did not reduce foraging activity via social learning from experienced group members, but did benefit from enhanced collective predator detection. This result represents an interesting example of the benefit of sociality and living in groups of individuals with different experiences.