Optimal divorce and re-mating strategies for monogamous female birds: a simulation model

Although the extensive variation in divorce rates among monogamous bird species has stimulated several theoretical accounts, the mechanisms underlying divorce strategies remain poorly understood. Here, we use an individual-based simulation model to investigate the adaptiveness of mechanisms of mate choice in the context of remating. Our model compares the fitness of females that choose a mate during each breeding season using one of two different decision rules; best-of-n females sample n potential partners and then select the male with the highest quality, whereas better option females choose a mate whose quality is maximal among the non-mated individuals they sampled the season before. It is assumed in the model that best-of-n females have no a priori information about the quality of potential partners and systematically decide to divorce at the beginning of each breeding season before searching for a new mate. Conversely, better option females use the information they gained the season before, and may retain their previous partner if they have no opportunity to mate with an individual of better quality. Results from simulations indicate that the best-of-n decision rule should be favoured when there is a large variation in male quality and low costs of mate sampling. On the other hand, the probability that the better option rule may invade the population is predicted to increase with male survival rate. However, changes in male mortality had no marked influence on the expected proportion of divorcing pairs, contrary to previous theoretical expectations.Communicated by H. Kokko