Early-life, but not late-life, exposure to predator cues reduce the lifespan and reproductive output of freshwater snails.

Abstract

Under predation risk, prey face tradeoffs between foraging, reproduction, and predator avoidance. These tradeoffs can affect life history traits, such as growth, reproduction, and lifespan. By increasing the risk of death, predators can cause prey to prioritize current reproduction at the expense of future reproduction, resulting in earlier reproduction, less growth, and reduced lifespan. Alternatively, predators can cause prey to invest energy in defensive morphology or growth at the expense of reproduction, resulting in reduced or delayed reproduction, larger size, and longer lifespan. Finally, responding to predators can be costly to prey. For example, the energetic cost from reduced foraging can potentially reduce growth, reproduction, and lifespan. Exposing prey to predation risk at different parts of the lifespan can disentangle these potential mechanisms. In this experiment, we tested how the timing of predation cues affects the life history of a freshwater snail pond snail (Physa acuta). We exposed the snails to predation cues in early life (post-hatching to 39 days old), late life (39 to 78 days old), or both and measured how predation exposure early and late in life affected growth, age at first reproduction, total reproduction, and life expectancy. We found that exposure to predation during early life led to a delay in first reproduction, lower life expectancy, and lower fecundity, regardless of cue removal later in life. Exposure to predation cues in late life had no effect on growth, life expectancy, or reproduction. These results suggest a developmental window in which predation risk affects life history traits and suggest a potential cost to prey responding to predators early in life.