Tadpoles modulate antipredator responses according to the abundance of vegetation experienced during the embryonic stage

Because of the selection pressures imposed by predation and the costs of antipredator responses, prey often exhibit phenotypically plastic behavioural defences that vary with risk level. For anuran larvae, the presence of vegetation is a critical environmental factor that predicts predation risk: in habitats with abundant vegetation, tadpoles are much less likely to be caught by fish and invertebrate predators. Hence, tadpoles might display the ability to match their antipredator behaviour with the amount of vegetation in the environment. I investigated this hypothesis by comparing the acute antipredator responses of tadpoles experimentally raised under high-vegetation and low-vegetation treatment from the egg stage. To address at which developmental stage the behavioural plasticity appeared, I additionally tested two groups of tadpoles that switched from a high- to low-vegetation habitat and vice versa soon after hatching. I observed a stronger antipredator response in tadpoles that experienced the environment with abundant vegetation at the embryonic stage. The environment experienced during the larval stage did not affect the tadpoles' antipredator behaviour. The direction of the observed plasticity aligns with the prediction of the risk allocation model. Therefore, my study seems to support the hypothesis that tadpoles can tune their antipredator behaviour not only based on the direct risk experienced (i.e. the number of predatory attacks) but also based on vegetation, an environmental factor that indirectly predicts predation risk.