Behavioural responses of Iberian midwife toad tadpoles (Alytes cisternasii) to chemical stimulus of native (Natrix maura and Squalius pyrenaicus) and exotic (Procambarus clarkii) predators

Abstract

Predation can be an important force of selection, resulting in the evolution or learning of antipredator defences in amphibian larvae. In the laboratory, we compared the behavioural responses of the tadpoles of Alytes cisternasii subjected to the chemical stimulus of an exotic predator, Procambarus clarkii, with the responses to the chemical stimuli of two of its native predators, the snake Natrix maura and the fish Squalius pyrenaicus, which employ different predation strategies. Tadpoles reacted more intensely to N. maura and then to P. clarkii, with no significant responses to S. pyrenaicus. The alteration in the use of the vertical axis of the aquaria was the antipredator behaviour more frequently used towards both native and exotic predators, and the adopted behaviour was adequate to the activity period and predation strategy of each predator. Alytes cisternasii tadpoles reacted to P. clarkii, a predator introduced about 20 years ago in the study area. These reactions may result from a micro-evolutionary process, but may also be a fortuitous response to a non-familiar cue. We can also not discard the possibility of learning by tadpoles since, due to the reproductive characteristics of this species, it was not possible to collect egg masses before their release in the aquatic environment.