PREDATORS CHOOSING BETWEEN PATCHES WITH STANDING CROP - THE INFLUENCEOF SWITCHING RULES AND INPUT TYPES

Where prey arriving in a patch are not consumed immediately, they will accumulate. Predators are then presented with a prey density or stand ing crop that increases through further input, and decreases through t he consumption by predators. Firstly, I show that the switching rule o f predators has a significant influence on the expected predator equil ibrium distribution in such a dynamic system. Three rules are compared ; for all rules, analytical solutions are calculated (where possible). To test their plausibility for natural situations, predator distribut ions are simulated given the assumption that each predator obtains ind ividual patch profitability estimates by using a common learning rule. As long as prey arrive in the patches in constant numbers per time un it, the first rule leads to input matching because predators stop swit ching when consumption in the two patches is equal. The other two rule s, where predators continue to sample both patches even in the equilib rium state, lead to predator distributions where the more profitable p atch is underused. The final equilibrium depends on the exact assumpti ons of the switching rule; however, it is independent of interference. But if the input delivered into a patch is a function of the current prey standing crop (for example in a reproducing prey population), pre dator and prey distributions will not reach an equilibrium in most cas es: either standing crops increase indefinitely, or they approach zero , with all predators concentrating on the better patch. Only a small n umber of parameter sets show intermediate crops that are reasonably st able. With this input type, only up to 54% of the simulations reach th e expected distribution. In a system with competition for dynamic stan ding crop, it is therefore essential to know the type of input and the switching-rule used by predators to be able to predict equilibrium pr edator distributions.