Inducible defense behavior of an anuran tadpole: cue-detection range and cue types used against predator

Inducible behavioral defense in response to predator cue detection is a key phenomenon in predator–prey interactions. The mechanisms by which prey use chemical/visual cues to avoid predation remain little known. We hypothesized that the distance at which prey species detect predator cues would be related to avoiding detection by the predator. To test this hypothesis, we performed laboratory experiments using an anuran tadpole (Hyla japonica) and a predatory dragonfly nymph (Anax parthenope julius). Tadpole activity level was reduced as a function of exposure to chemical cues from the dragonfly predator, but activity levels did not change when tadpoles were exposed to potential visual cues from the dragonfly. The distances over which tadpoles detected predator cues were longer than those over which the dragonfly predator detected tadpoles. The differences in cue-detection ranges between tadpoles and dragonfly predators are related both to predator avoidance by tadpoles and effective foraging strategies by dragonfly predators. Chemical cue detection as a trigger of inducible defense by prey species may shape predator–prey relationships in aquatic habitats.