Costly interactions between the sexes: combined effects of male sexual harassment and female choice?

Male and female interests can differ profoundly regarding quality and quantity of mates. Especially in promiscuous mating systems, males often inflict costs on females that may precipitate in negative fitness consequences. In reality, however, discerning between female costs arising from a sexual conflict and costs arising from female mate choice is not trivial. In livebearing fishes, for example, costs of male sexual harassment are often quantified as female feeding time reductions, but female feeding times may also be affected by competitive interactions and the willingness of females to interact with a particular mate (i.e., mate choice). Using the tropical live-bearer Poecilia mexicana as a model, we manipulated male and female nutritional state and measured focal females' feeding times in presence of another female as well as in presence of males of varying quality. Consistent with other studies quantifying effects of male harassment, female feeding times were negatively affected by sexually active males. Also, females were feeding more in presence of starved males than in presence of well-fed males. In subsequent dichotomous choice tests, females preferred to associate with well-fed females. These results are not consistent with the sexual conflict hypothesis: If the reduced female feeding time in presence of a well-fed male were solely a cost imposed by the male, females would be expected to avoid such males in a choice situation. Consequently, our study suggests that both male sexual harassment and active female choice simultaneously affect female feeding times in livebearing fishes.