Increases in predation favor evolutionary shifts in behavioral plasticity in Trinidadian killifish (Anablepsoides hartii).

Abstract

Behavioral plasticity is expected to be favored in risky environments, such as when prey species coexist with predators, because prey must alternate between fitness related foraging/mating behaviors and antipredator behaviors that enhance survival. We compared behavioral plasticity in Trinidadian killifish that are found in sites with and without predators. We quantified aggressive and antipredator behaviors via a mirror assay in second-generation lab-reared and wild-caught killifish before and after exposure to predator cues. We compared two types of aggression including: overt aggression (ramming, biting, lunging, tail-slapping) and display aggression (spine arching, bending into an s-shape, and opercular flaring). We additionally compared the amount of time the fish spent frozen as a proxy for anti-predator behavior. We show clear differences in plasticity between populations with and without predators. Killifish from sites with predators decreased overt aggression in response to exposure to predator chemical cues. Plastic responses to the predator cue were lower in killifish from sites that lack predators. Interestingly, wild fish from sites without predators did respond to the predator cue by decreasing overt aggression and increasing time spent frozen, though to a lesser degree compared to the fish from sites with predators. Our results support the expectations that development in a risky environment favors evolutionary changes in predator-mediated behavioral plasticity.