The Effect of Quantitative Differences of Predator-Borne and Prey-Borne Cues on Defensive Responses of Dryophytes leopardus Tadpoles

Anuran tadpoles perceive predation risk in the environment from the types of semiochemical cues emitted by both predators and prey, and they perform various defensive responses to reduce encounter probabilities and increase the escape probability after predator attacks. While the impact of simple stimuli, such as the presence or absence of predation risk, on defensive responses has been extensively studied, the influence of quantitative gradients and the interaction of these cues on defensive responses is less understood. In this study, we reared Dryophytes leopardus tadpoles in environments with varying numbers of predatory dragonfly nymphs, Orthetrum albistylum speciosum, and tadpole prey conspecifics to examine how different levels of stimuli affect the defensive responses of tadpoles. The cue from prey consumed by nymphs triggered a decrease in tadpole activity. The two cues interact in a complex way which affects how the tadpole responded. Increased prey-borne cues result in induced increases in total length and tail length in the tadpoles when there was one predator nymph, but no effect was detected when there were two nymphs. Our results indicated that D. leopardus tadpoles perceive quantitative variations in cues of different origins and respond to varying levels of predation risk in a more complex manner than we had expected.