Female choice of sites versus mates in a coral reef fish,Thalassoma bifasciatum

To understand the dynamics of sexual selection, one needs to identify the basis of female choice in mating. Daily censuses showed that most spawns of individual female bluehead wrasses, Thalassoma bifasciatum, occurred at one of several available mating sites, either in a group-spawning aggregation of small males or with a large territorial male. Most females were not located near their principal mating site during the non-spawning period of the day. Females were thus exposed to other males and sites and should have had the opportunity for choice. When a resident territorial male disappeared or was removed experimentally from a mating site, females did not alter their fidelity to that site. Furthermore, manipulations showed that when a territorial male changed the location of his mating activity to an adjacent site, females did not follow him but continued to mate at their customary site. Thus mating sites, rather than the males occupying them, appeared to be the objects of female choice. The bright coloration and courtship behaviour of larger males may demonstrate the safety of a particular site rather than indicating some aspect of male quality.