Differential vulnerability of two sympatric tadpoles to an invasive crayfish predator
Many amphibian population declines have been associated with the introduction of alien aquatic predators. Here, we explore the vulnerability of tadpoles of two sympatric Japanese species [Pelophylax nigromaculatus (PN) and Rhacophorus schlegelii (RS)] to the invasive crayfish Procambarus clarkii. We first examined the behavioral responses of the tadpoles to the cues of caged, fed crayfish predator in a controlled laboratory experiment, and subsequently tested their survival when together in the presence of free-ranging predator in outdoor mesocosms that simulated natural ponds. Only PN reduced activity level to the cues of the predator, but this apparent behavioral defense recorded in the laboratory did not result into higher survival in outdoor mesocosms. In mesocosms, PN exhibited higher biomass increment but experienced higher mortality in predator environments. The mechanism mediating mortality remains unclear though. These results indicate that sympatric prey may differentially respond and be disproportionally vulnerable to novel predators. Our study illustrates the possible contribution of a life-history trait influencing risk of predation in newly invaded systems.
KeywordsLife-history trait Procambarus clarkii Predator–prey interactions Novel predator Behavioral defense
The study was supported by the Japanese Society for the Promotion of Science KAKENHI Grant Number 26640137. We are grateful to two anonymous reviewers whose comments greatly improved the manuscript. We thank Koichi Nishimura, Yuka Tamura, and Kosuke Nakanishi for their help in collecting the subjects used in the experiments. Martina Muller provided constructive comments at an earlier draft of the manuscript. The experiments comply with the current laws of Japan concerning the collection, transport, and the use of live animals.
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