Environmental, social and reproductive factors influence the risk–reward trade-off in a group-living fish

Animals are faced with a fundamental risk-reward trade-off when making decisions about foraging in the presence of predation, yet little is known about how social, reproductive and environmental factors mediate this trade-off. In the marine environment, anemonefishes provide a model system for investigating the determinants of risk–reward trade-offs, because they live in size- and sex-structured groups within protective sea anemones tentacles, yet feed predominantly in the water column where they are at risk of predation. Furthermore, exposure to changing tides means the availability of planktonic food covaries with their risk of predation. Therefore, we examined how tide, sex and status, and the presence of eggs influenced the time that Amphiprion mccullochi spent at different distances from their anemone, a proxy for foraging effort and predation risk. We found that individuals significantly adjusted their time spent far and close to the anemone depending on the tide, status and the presence of eggs, and that these adjustments can be explained in light of threat sensitive behaviour. This study illustrates the relative importance of environmental and social factors on intraspecific variation in foraging and antipredator behaviour and bolsters our understanding of the decision’s individuals make to balance the costs and benefits of foraging over temporal and spatial scales.