Vocal Communication in a Neotropical Treefrog, Hyla Ebraccata: Responses of Females To Advertisement and Aggressive Calls

Abstract

AbstractWe investigated the functions of different elements of the complex vocal repertoire of the Panamanian treefrog Hyla ebraccata by testing the responses of females to synthetic advertisement and aggressive calls in two-choice playback experiments. In tests of single-note advertisement calls presented at different rates, females preferred faster calling rates, regardless of the absolute rate of the stimuli. In tests of single-note advertisement and aggressive calls, females preferred advertisement calls. Addition of secondary click notes to aggressive calls made the calls more attractive to females, but multi-note advertisement calls were preferred over multi-note aggressive calls. When females were given a choice of multi-note advertisement calls and single-note calls of the same total duration, they showed no preference. This suggests that multi-note calls are preferred over normal single-note calls because of their longer total duration. When the same experiment was performed with aggressive calls, females showed a strong preference for multi-note calls. This indicates that long aggressive calls, such as those given by males in close-range encounters, may entail some cost to the male in reduced attractiveness to females. Males apparently reduce the costs of aggressive calling by adding click notes to aggressive calls, by giving aggressive calls only when nearby males do so, and by establishing spatial relationships in the chorus before females begin to choose mates.