Summary

Studies of contests among amphibians are heavily biased towards acoustic contests in frogs: in these, males compete to be attractive to females or to defend territories required for some aspect of reproduction. While the calls of frogs are species-specific and appear to be highly stereotyped, these studies have revealed a high degree of plasticity that enables males to vary their calls in response to their immediate circumstances. Because calling is energetically expensive, males must face trade-offs between increasing their immediate calling effort and conserving energy for future mating opportunities. In some species, they also trade-off between repelling rival males and attracting females; this is because females are averse to aggressive calls. There is a great deal less known about contests among salamanders and caecilians, primarily because these animals are much harder to observe and because their primary means of communication, olfaction, is harder to manipulate experimentally than the acoustic signals of frogs. Despite many unanswered questions, a great deal has been learned about aggressive behaviour in amphibians, and these studies have made important contributions towards a general understanding of animal contests. This chapter discusses the diversity of issues related to contest behaviour in amphibians and highlights how these organisms remain fruitful subjects for future studies of animal contests.

Introduction

Compared with birds and mammals, amphibians are still a poorly known group of animals with one or two new species still being described each week: 20 years ago, 5399 species were listed (Halliday & Adler 2002) with the number currently exceeding 7000 (AmphibiaWeb). In part, this reflects the fact that amphibians are typically small animals that lead secretive lives and engage in observable behaviour for limited periods of time. As a result, our knowledge of the social behaviour of amphibians is fragmentary, with only a few species studied intensively. An encyclopaedic overview of amphibian behaviour is provided by Wells (2007).