Rover: A Strategy for Exploiting Cooperators in a Patchy Environment

We present a computer simulation that examines the dynamics of cooperative behavior in a patchy environment. A new defecting strategy called "ROVER" is introduced, which uses a rule analogous to the "marginal value" theorem to determine how long to stay in a patch. A wide range of parameter values allow ROVERs to invade a metapopulation of tit-for-tat strategists (TFT) and spread either to fixation or to a stable equilibrium in which ROVER is the majority strategy. Our model, along with previous models that invoke different mechanisms, suggests that even guarded forms of cooperation such as TFT are often vulnerable to invasion and that a stable mixture of cooperators and exploiters might be common in nature.