A model on female breeding dispersion and the reproductive systems of pinnipeds.

Because most mammalian mating systems ultimately depend on female dispersion, the study of habitat selection by breeding females will help in understanding the ecology of mating systems. I developed a cost-benefit model of breeding dispersion of females that is based on the concept of 'ideal free' distribution. The currency of the model is the probability of offspring survival. The cost of female grouping is the increment of female-female competition for resources, and the benefit is the reduction of male harassment. The maximal benefit depends on the resource quality of the breeding sites. I tested the qualitative predictions of the model on the female dispersion and mating system of pinnipeds. The model predicted the main differences observed between taxonomic groups of pinnipeds: higher female aggregation and polygyny in Otariidae than in Phocidae, in Otariinae than in Arctocephalinae, and in Mirounga spp. and Halichoerus sp. than in the rest of the phocids. My approach emphasises the importance of male harassment for the evolution of mammalian mating systems. I propose that the classical view of a unidirectional approach to the ecology of mammalian mating system (resource dispersion-->female dispersion-->male dispersion), should be modified to incorporate a feedback from male dispersion to the factors that regulate female dispersion.