DIET CHOICE AND PREDATOR-PREY DYNAMICS

We compare the dynamics of predator-prey systems with specialist preda tors or adaptive generalist predators that base diet choice on energy- maximizing criteria. Adaptive predator behaviour leads to functional r esponses that are influenced by the relative abundance of alternate pr ey. This results in the per capita predation risk being positively den sity-dependent near points of diet expansion. For a small set of param eter values, systems with adaptive predators can be locally stable whe reas systems with specialist predators would be unstable. This occurs mainly when alternate prey have low enough profitability that predator s cannot sustain themselves indefinitely when feeding on alternate pre y. Local stability of systems with adaptive predator behaviour is inve rsely related to the goodness of fit to optimal diet choice criteria. Hence, typical patterns of partial prey preference are more stabilizin g than perfect optimal diet selection. Locally stable systems with ada ptive predators are often globally unstable, converging on limit cycle s for many initial population densities. The small range of parameter combinations and initial population densities leading to stable equili bria suggest that adaptive diet selection is unlikely to be a ubiquito us stabilizing factor in trophic interactions.