ON THE INTERPLAY OF PREDATOR SWITCHING AND PREY EVASION IN DETERMINING THE STABILITY OF PREDATOR-PREY DYNAMICS

Abstract

Traditionally, predator switching has been assumed to be a stabilizing force in ecological systems. Recent work, however, has shown that predator switching can be either stabilizing or destabilizing. Most models of predator switching, to date, assume that prey are behaviorally passive and do not respond to predators. We allowed prey to respond behaviorally to predators, so as to avoid capture, in order to explore how this ecologically realistic addition modified the impact of predator switching upon population stability and persistence. We used an individual-based, spatially explicit model that described local interactions between predators and prey, with a probability that prey would "sense" predators in adjacent cells and move away from the predators. We compared the individual-based model to a simple difference equation model. We found that intermediate prey sensitivity in the individual-based model allowed the highest probability of persistence of the predator- prey system. By allowing prey sensitivity, and the prey density threshold at which predators switch between prey, to evolve, we found that the evolution of sensitivity acted to stabilize the predator-prey system. We also found that at large prey growth rates, polymorphism in switching strategies can be stable in the predator population. These results suggest that prey behavior, coupled with predator switching, can have a large impact on the stability, persistence, and heterogeneity of predator-prey systems.