Juvenile toads avoid chemical cues from snake predators

Chemical senses mediate several anuran behaviours, including predator avoidance by larval frogs. Predation by garter snakes is an important influence on the survival of post-metamorphic, juvenile toads (Bufo sp.). Studies have shown that visual, rather than chemical, cues are important for predator avoidance in post-metamorphic juvenile bufonids. This study investigated the ability of post-metamorphic, juvenile great plains toads, B. cognatus, and southwestern toads, B. microscaphus, to detect and avoid chemical cues from their respective predators, the eastern plains garter snake, Thamnophis radix, and the wandering garter snake, T. elegans. Juvenile B. cognatus collected in South Dakota were observed on unmarked paper towels significantly more than on similar towels treated with chemical cues from T. radix. Similarly, juvenile B. microscaphus from Arizona were observed on unmarked towels significantly more than on towels marked with chemical cues from T. elegans. Toad avoidance of snake odour was apparently not a generalized response to reptile chemical cues: juvenile B. microscaphus continued to avoid snake odours when these were simultaneously presented with odours from sympatric lizards, Sceloporus undulatus. Hence, juvenile B. cognatus and B. microscaphus apparently detect and avoid chemical cues from snake species that prey on them. (C) 1997 The Association for the Study of Animal Behaviour.