Are leaders good mates? A study of call timing and male quality in a chorus situation

Within insect and anuran choruses, females are exposed to many male sexual signals overlapping in time. In many species, male call timing influences mate choice, with females preferentially orienting towards males that succeed in calling just before their opponents. The mechanisms through which males actively regulate their call timing to achieve this have been the focus of much interest. However, no study has addressed the problem of the reliability of call leadership as an indicator of male quality, which is crucial to females, since basing their choice of mate on an unreliable criterion could lead them to engage in suboptimal matings, with detrimental effects to their fitness. Addressing this question in the European treefrog, Hyla arborea, we first ascertained that females preferentially orient towards the first of two identical overlapping conspecific calls. We then found that within experimental choruses the males with the highest proportion of leading calls had significantly higher total calling times, a call characteristic encompassing two indicators of signal costliness: call duration and call rate. Although we failed to find a link between call leadership and male body condition, this study provides novel evidence that female preference for leading calls leads to the selection of the males with the highest energetic investment in their sexual display. The handicap principle predicts that this form of female preference should increase the fitness of females by guaranteeing that they select high-quality mates.