Iberian green frog tadpoles may learn to recognize novel predators from chemical alarm cues of conspecifics

Abstract

Many antipredator adaptations are induced by the prey's ability to recognize chemical cues from predators and to act according to the threat level posed by that predator. However, predator recognition often requires learning by prey individuals. We tested the ability of Iberian green frog, Rana perezi, tadpoles to assess the magnitude of predation risk and adjust their behaviour by using perceived cues from a predatory snake, when this stimulus was found alone or associated with chemical alarm cues from conspecific tadpoles. Tadpoles exposed to alarm cues and the predatory snake scent together reduced their movement rates to a greater extent than when the snake scent was found alone, and reduced movement even more in the subsequent exposure to the predator snake scent alone. We also tested whether tadpoles were able to associate novel chemical cues (i.e. from an exotic nonpredatory fish) with predation risk after a simultaneous exposure with conspecific alarm cues. Tadpoles exposed to nonpredatory fish cues and alarm cues together reduced their activity levels, and reduced activity in the subsequent exposure to the fish cue alone, in a similar way as they reduced movement in the presence of predatory snake cues. Therefore, tadpoles learnt to perceive the fish cues as risky when these were previously associated with alarm cues. Predator recognition learning ability may be particularly advantageous for organisms whose environment may have a wide range of types of predators, even new exotic introduced species of predators that can affect the survival of prey.