Evolutionarily stable strategies in competition for resource intake rate maximization

Summary

Many animals exploit resources distributed in separate patches. It is commonly assumed that the aim of individuals travelling between patches and exploiting them is to maximize their rate of resource intake, and that the costs of searching for resources are one obvious constraint in fitness maximization. This paper also takes into account some asymmetries between competitors. Conflicts between individuals take the form of either competition by exploitation or of overt contests for resource items. A simple model is developed to answer the question: Which animal should withdraw and when (thereby leaving his opponent within a patch)? It was found that evolutionarily stable strategies (ESS's) are based not only on existing asymmetries but also on current population density. It is possible for conventional and paradoxical ESS's to occur when a patch exists for a sufficiently long period of time in relation to the time of travelling between patches. These strategies can be expected when resources are not overcrowded or when the costs associated with joint exploitation of patches are high. This result is compared with the existing models of animal conflicts for distinct indivisible resources. Some topics concerning optimal foraging and migration decisions are discussed, and empirical evidence is examined.