Witnessing Neighbors React to Alarm Cues Alters Risk Perception in Mosquitofish

In nature, the risk of encountering a predator is often uncertain. By using information provided by others about predators, individuals can appropriately adjust their behavior without having to encounter a predator themselves.... [ view full abstract ]

In nature, the risk of encountering a predator is often uncertain. By using information provided by others about predators, individuals can appropriately adjust their behavior without having to encounter a predator themselves. Using locally captured mosquitofish (Gambusia affinis), this study examined whether witnessing conspecifics experience risk informs how individuals react to different contexts. Focal individuals witnessed two partner fish experience either a risky stimulus or a control stimulus. After observing the behavior of their partners for 5 minutes, the activity of the focal individual was measured in (1) a novel but safe environment and (2) a risky environment with visual and chemical cues of predation risk. We found that activity of the focal individuals in the safe environment depended on witnessing the experience of their partners. Individuals who had witnessed stressed partners encounter a risky stimulus showed significantly less activity in the novel environment compared to individuals who had witnessed unstressed partners encounter a control stimulus. In the risky environment with cues of predation risk, all focal individuals showed low levels of activity regardless of their partner’s experience. These results suggest that individuals who witnessed stressed partners experience a risky stimulus used this social information to infer a high level of risk and behaved cautiously in the novel environment in response. As the danger of acquiring private information increases, as it would with predation risk, reliance on social information should increase. Our study emphasizes how information transfer between individuals can be surprisingly subtle and arise from simply witnessing the behavioral changes of others. Understanding the fitness costs and benefits of using ambiguous social information about risk would shed light on the conditions under which sensitivity to the behavioral responses of conspecifics might be favored.