Evolution of fighting behaviour: Decision rules and assessment of relative strength

Abstract

A mathematical model of fighting behaviour is developed. The contestants belong to a population with varying fighting abilities and the fights consist of the repetition of one type of interaction. At each interaction in the sequence the opponents acquire some information about the true fighting abilities. The fights are seen as a motion of each opponent through a causal factor space; the current position of an animal in the space represents all information obtained by the animals so far. A decision rule (strategy) is a specification of what action to take at each point in the causal factor space. Evolutionarily stable strategies are calculated numerically and are found to be pure and unique. The distribution of fighting times and the probabilities of winning are calculated for pairs of contestants from a population using the ESS. Expected utilities are also computed and in the situations investigated they are fairly close to the maximum value that would obtain if the contested resource were divided equally between the contestants without any cost. © 1983.