Evolutionarily stable stealing: game theory applied to kleptoparasitism.

We present an individual-ba sed 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 ecolgical 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 (Le., success at one can only be improved at the expense of the odier). 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. Key words: evolutionarily stable strategy, food contests, foraging behavior, functional response, inter- ference, game theory. (Bthav Ecoi 9:397-403 (1998))