Early-life and parental predation risk shape fear acquisition in adult minnows

Exposure to predation risk can induce a fearful baseline state, as well as fear reactions toward novel situations (i.e., neophobia). Some research indicates that risk exposure during sensitive periods makes adults more prone to acquiring long-term fearful phenotypes. However, chronic risk can also lead to ignoring threats in order to maintain other activities. We sought to assess how a relatively long period of low risk, experienced either early in life or by the previous generation, influences fear behaviour acquired from a short period of high risk as adults. We used fathead minnows as study subjects and simulated predation risk with repeated exposures to conspecific chemical alarm cues. The period of high risk experienced by adults induced typical fear behaviour (baseline freezing and neophobia), whereas the early-life low-risk period 1 year prior caused only a reduction in baseline foraging. We found no evidence that the early-life risk significantly altered the fear acquired from the adult-risk period. However, in a second experiment, a low-risk period during the parental generation interacted with a high-risk period experienced by the adult offspring. The combination of both risk periods heightened baseline freezing despite parental risk having little effect independently. Hence, our study provides evidence that parental risk exposure can lead to an additive intergenerational effect on fear acquisition in minnows.