BEYOND THE IDEAL FREE DISTRIBUTION - MORE GENERAL-MODELS OF PREDATOR DISTRIBUTION

The ideal free distribution model which relates the spatial distributi on of mobile consumers to that of their resource is shown to be a limi ting case of a more general model which we develop using simple concep ts of diffusion. We show how the ideal free distribution model can be derived from a more general model and extended by incorporating simple models of social influences on predator spacing. First, a free distri bution model based on patch switching rules, with a power-law interfer ence term, which represents instantaneous biased diffusion is derived. A social bias term is then introduced to represent the effect of pred ator aggregation on predator fitness, separate from any effects which act through intake rate. The social bias term is expanded to express a n optimum spacing for predators and example solutions of the resulting biased diffusion models are shown. The model demonstrates how an empi rical interference coefficient, derived from measurements of predator and prey densities, may include factors expressing the impact of socia l spacing behaviour on fitness. We conclude that empirical values of l og predator/log prey ratio may contain information about more than the relationship between consumer and resource densities. Unlike many pre vious models, the model shown here applies to conditions without conti nual input. (C) 1997 Academic Press Limited.