Hearing is not necessarily believing in nocturnal anurans

Abstract

The recent discovery of the use of visual cues for mate choice by nocturnal acoustic species raises the important, and to date unaddressed, question of how these signals affect the outcome of mate choice predicted by female preference for male calls. In order to address this question, we presented female Hyla arborea tree frogs with a series of choices between combinations of acoustic and visual cues of varying quality in nocturnal conditions. While females exhibited the expected preference for a combination of attractive values for visual and acoustic signals over combinations of unattractive values for both signals, when presented with conflicting acoustic and visual cues, they equally adopted one of two strategies, preferring either attractive calls or intense vocal sac coloration. This constitutes novel evidence that the outcome of mate choice, as predicted on the basis of male calling quality, can be drastically different when additional communication modalities--in this case vision--are taken into account. These results also highlight the possible existence of individual variation in female rules for cue prioritization. The implications of these results for the study of mate choice in nocturnal acoustic species are discussed.

Figure 1.

Female preference for attractive (black bars) versus unattractive (grey bars) male calls when (a) attractive calls were associated with attractive vocal sac coloration and unattractive calls were associated with unattractive vocal sac coloration, and (b) attractive calls were associated with unattractive vocal sac coloration and unattractive calls were associated with attractive vocal sac coloration. Differences were tested using two-tailed binomial tests (**p < 0.01).