Synchronous and Alternating Choruses in Insects and Anurans: Common Mechanisms and Diverse Functions

SYNOPSIS. Neighboring males in rhythmically calling insects and anurans often chorus in a synchronizing or alternating fashion. Neuroethological investigations of chorusing species reveal that their rhythms are maintained by pacemakers and that a basic interactive algorithm, common to many species, yields the collective synchrony or alternation observed. Traditionally, synchrony has been viewed as a cooperative event. However, recent evidence suggests that a collective synchronous display can also be an incidental outcome of signal “jamming” activities between neighboring males competing to attract females. This arises when female phonotaxis is influenced by a precedence effect in which the first of two or more closely synchronized calls is preferred. Under such circumstances, males are selected to adopt a timing mechanism averting following calls. If males happen to call at comparable rates, the adopted mechanism can yield synchrony as a by-product. Alternation, too, may be produced by a similar mechanism and also represent an epiphenomenon. That alternation, as opposed to synchrony, results may be a mere artefact of the species' solo calling rate, but perceptual constraints may select specifically for alternation in some species.