The Ideal Free Distribution with Kleptoparasitism

We present a simple mechanistic model describing kleptoparasitic (food stealing) behaviour among a group of foragers. This behavioural model is used to produce an analytic expression for the food uptake rate (functional response) of individual foragers in the presence of kleptoparasitism. The parameters of this functional response can be interpreted in terms of the underlying behavioural model. We define intensity of interference as the rate at which obtained uptake rate, relative to that achieved without competitors, decreases with increasing forager density. The intensity of interference increases with increasing forager density and with decreasing food density. The functional response is used to find analytic expressions for the ideal free distribution of foragers among a range of habitats differing in food density. The model predicts that the proportion of foragers opting to use the richest patch will always be greater than the proportion of food there. The proportion of foragers using a patch depends not only on the proportion of food on that patch but on the distribution of food between the other patches in the system.