The ideal free distribution with unequal competitors: the effects of modelling methods

We examine two methods of allocating animals between sites of different resource input rate in the context of the ideal free distribution. The basic models are of individuals of two classes of competitive weight distributing themselves between two sites. The importance of arrival sequence and the subsequent movements of animals between sites are investigated. When all the good competitors arrive before the poor competitors, the distribution of each class conforms to the input matching rule. When competitors arrive in a random sequence, poor competitors switch between patches. Resulting distributions are compared with predictions from the ideal free distribution with unequal competitors and from statistical mechanics. The comparisons show fewer animals using the site with the highest resource than predicted by the input matching rule, that is, undermatching is found. The effect of each animal having a unique competitive ability is then examined. We discuss the application of ideal free distribution models to areas of behavioural ecology other than foraging, together with alternative rules to the standard instantaneous intake rates rule. Copyright 1998 The Association for the Study of Animal Behaviour.