Evolutionarily stable stealing: game theory applied to kleptoparasitism

We present an individual-based model of a group of foraging animals.Individuals can obtain food either by discovering it themselves or by stealing it from others (kleptoparasitism). Given that challenging another individual for a discovered food item costs time (which could otherwise be spent searching for an undiscovered item), attempting to steal from another may not always be efficient. We show that there is generally a unique strategy that maximizes uptake rate-always or never challenging others. For any combination of parameter values, we can identify which strategy is appropraite. As a corollary to this, we predict that small changes in ecological conditions can, under some circumstances, cause a dramatic change in the aggressive behavior of individuals. Further, we investigate situations where searching for undiscovered food and searching for potential opportunities for stealing are mutually exclusive activities (i.e., success at one can only be improved at the expense of the other). Using game theory, we are able to find the evolutionarily stable strategy for investment in these two activities in terms of the ecological parameters of the model.