An ESS model for divorce strategies in birds

Abstract

We present a theoretical investigation of divorce. Arguments are couched in terms of birds, but should be applicable to other groups of organisms. We model a population in which there is a range of both male and female qualities, and decisions on whether to divorce are made by both members of a breeding pair. The reproductive success of a pair is additive in male and female qualities in the baseline case, but we also consider the effect of quality interactions. The availability of new mates depends on the divorce strategy of all population members. We allow for the possibility that mate choice is associative in quality, although we do not explicitly model the mate choice process. Using a game–theoretical model which incorporates these factors we investigate the following issues: the form of the evolutionary stable strategy, and the implications of this strategy for quality correlations in breeding pairs and for the distribution of qualities among unpaired individuals; divorce rates, reproductive success and mate quality changes over the lifetime of an individual, and the dependence of these qualtities on the individual's quality; mean population divorce rates and their dependence on costs of divorce, longevity and the extent of quality variation in the two sexes; initiators of divorce and reproductive success before and after divorce.