Temporal and Spatial Effects of Predator Chemical and Visual Cues on the Behavioral Responses of Rana japonica Tadpoles

A laboratory experiment was conducted to evaluate temporal and spatial effects of predator chemicals and visual stimuli on the behavioral responses of the Rana japonica tadpoles. Nymphs of the dragonfly Anax parthenope Julius were used as the predator model. Tadpoles exhibited defensive responses by reducing tail movement time associated with their activity when exposed to chemicals from the nymphs. These responses tended to be quicker and stronger as distance from the nymphs decreased. Tadpoles exposed to visual stimuli from the nymphs also exhibited similar but weaker behavioral responses. Our results suggest that in a short distance encounter defensive responses of the R. japonica tadpole are induced more quickly by chemical cues of the predator than by its visual cues. For the tadpole, detecting the dragonfly nymph by chemical cues may function as a trigger for effective predator-avoidance strategy in tadpole-dragonfly nymph interactions.