Boldness is affected by recent experience with predation cues and body size in mosquitofish

Adjusting behaviour can be crucial to prey surviving a predator encounter. How any one individual modifies their behaviour in response to predation risk might be affected by their previous experience with danger and their own vulnerability. Using western mosquitofish, we examined how boldness in different contexts was affected by an individual's recent experience with predation risk. Individuals were repeatedly chased by a largemouth bass model and encountered alarm cue to mimic conditions of high risk (cues twice on 2 days), low risk (cues twice on 1 day), or no risk (water only). We then measured boldness and avoidance behaviour under three different contexts: in a novel tank, with a shoal of conspecifics, and with alarm cues and a model predator. We found that how recent experiences influenced boldness in a novel tank depended on body size. Smaller fish from the no and low risk treatments were more likely to emerge from a shelter into a novel environment than larger individuals. When individuals had recently experienced high levels of risk however, this pattern was reversed. We also found that individuals who had experienced any recent risk (low and high) were more likely to leave the safety of a shoal and approach a novel object compared to individuals who had not experienced any recent danger. Avoidance behaviour across the three assays was not affected by recent experiences but was affected by body size to varying degrees. For example, larger fish were more likely to stay in the plants, away from the cues of predation compared to smaller fish. Overall, our results suggest that how recent experiences with risk influence subsequent behaviour can depend on a variety of interacting factors including the intensity of recent experiences, the particular behaviour examined, and an individual's body size.