Vulnerability and behavioral responses of South Chinese anuran tadpoles to native dragonfly (Pantala flavescens) naiads and introduced western mosquitofish (Gambusia affinis)

Abstract

Alien predator species are a serious threat to amphibian populations. We studied the vulnerability and behavioral defenses of tadpoles of six Chinese anurans in response to the introduced, active foraging predator Gambusia affinis (western mosquitofish) and compared them with the responses to the native ambush predator Pantala flavescens (dragonfly and naiad stage) in laboratory experiments. The tadpoles were Bufo gargarizans, Duttaphrynus (formerly Bufo) melanostictus, Rana zhenhaiensis, Fejervarya multistriata, Microhyla onata, and Hoplobatrachus chinensis from Lishui, Zhejiang, South China. Our data showed that both native P. flavescens and introduced G. affinis could prey on the six tadpole species to different degrees and that the two toad tadpoles (B. gargarizans and D. melanostictus) were significantly less vulnerable to predation than the frog ones. The reduced vulnerability of toad tadpoles to predation may be attributed to their unpalatability and their continuous swimming ability, traits that are adaptive in more permanent habitats. Compared with the ambush predator P. flavescens, tadpoles reduced their activity level and used spatial avoidance measures when encountering G. affinis. Overall, our results suggest that some of the tadpoles in the study area are likely to recognize and respond to the predation threats of G. affinis.