Differential antipredator behavioral responses in tadpoles of Duttaphrynus melanostictus (Anura: Bufonidae): an experimental demonstration

Abstract

In aquatic systems, many prey animals including larval anurans predominantly use chemical cues to assess predation risk. In such systems, a variety of predators (e.g., insects or their larvae, sympatric carnivorous/omnivorous tadpoles) can affect the behavioral responses and life history of prey tadpoles. Many anuran tadpoles are able to discriminate chemical cues of different predators and exhibit differential antipredator behavioral responses according to the perceived risk. The behavioral responses of tadpoles of Duttaphrynus melanostictus to different predators (predaceous insects, Lethocerus sp., omnivorous tadpoles of Euphlyctis cyanophlyctis, and carnivorous tadpoles of Hoplobatrachus tigerinus) were studied in the laboratory. The predator’s diet-derived metabolites released in the excreta of the predators after consumption of conspecific (D. melanostictus) prey tadpoles were used to simulate predation threat. The D. melanostictus tadpoles showed antipredator behavioral responses i.e., reduced swimming movements and overall time spent swimming, and had a higher burst speed in response to water-borne cues released from the excreta of all predators that were fed with conspecific prey. Further, D. melanostictus tadpoles showed the strongest antipredator behavioral responses to cues released by carnivorous, active predatory tadpoles, H. tigerinus, moderate responses to the cues of the sit-and-wait carnivorous insect, Lethocerus sp. and low responses to those of omnivorous E. cyanophlyctis tadpoles. The hierarchy of antipredator behavioral responses in D. melanostictus tadpoles to different predators is H. tigerinus > Lethocerus sp. > E. cyanophlyctis > chemical blank solution. The findings of the present study thus show that tadpoles of D. melanostictus appear to modulate the intensity of their defense behavior in accordance with the level of threat posed by each predator.