Thresholds and escalation of antipredator responses in the Chinese salamander Cynops cyanurus: inter- and intra-individual variation

Abstract

Aspects of the control of antipredator behavior, including short- and long-term response modifications, were examined for the Chinese salamander Cynops cyanurus. Salamanders were tested for their antipredator behavior following repeated contact with the flicking tongue of a predatory snake. In a given trial, a salamander was contacted ten times by the snake and within-trial escalation or reduction in response was monitored. For each salamander, trials were repeated 6 times at 21-day intervals to test for long-term changes in response threshold and extent of escalation, and to identify consistent differences in behavior among individuals. The salamanders were found to escalate their antipredator responses over the ten stimuli within trials. They were significantly more responsive to tongue contacts late in a given trial than to the initial stimuli. They also showed long-term, among-trial decreases in the threshold to initial response and increases in the mean responses to the first tongue contacts. However, there was no significant long-term change in maximum response threshold or in the mean responses to the final tongue contacts. Variation among individuals in thresholds and responses was considerable and was consistent over trials.