The significance of sound interception to males of the bicolor damselfish,Pomacentrus partitus, during courtship

Abstract

Playback experiments conducted in the field and the laboratory demonstrated the use of sound interception in bicolor damselfish,Pomacentrus partitus. Two courtship sounds produced by male bicolors: the ‘chirp’ which occurs at the initiation of courting and the ‘grunt’ which occurs near the termination, just prior to spawning, were found to hold different meanings to intercepting male competitors. Males responded to grunt playback with directional swimming towards the sound source and increased courtship behavior. No directional response was observed during chirp playback. The grunt sound appears to indicate that a spawn-ready female is present near the sound source. Males therefore move towards it, likely to interfere with the imminent spawning or to gain a possible spawning partner. Such is not observed in response to chirps, as little advantage would be gained by moving to the source of a sound which is known to serve as an ‘advertisement’ or ‘territorial keep-out’ signal. Thus, upon intercepting a neighbor's chirps, males exhibit courting within their own territory, or directly court a nearby female.