Calculated risk-taking by predators as a factor in Batesian mimicry

Abstract

A simulation model is constructed from a set of disc equations (Holling 1959b) incorporating a probability term which represents calculated risk-taking by the predator, and determines the proportion of encountered models and their perfect Batesian mimics which are sampled by the predator. The risk-taking parameter (R) is assumed to be a function of both mode:mimic ratio (the higher the ratio, the lower R) and availability of alternate prey (the greater the availability, the lower R).The model was tested with an artificial predator–prey system in the laboratory, and was able to predict mimic mortality under most conditions. Computer simulation experiments were then conducted to explore a variety of relationships, including the functional response to mimic density, the effect of alternate prey density on mimic mortality, and the effect of proportion of models on the effectiveness of mimicry as an anti-predator strategy. Despite its simplicity the model makes predictions qualitatively similar to those of more complex models, and to the results of various empirical studies of mimicry. The importance of considering the alternate prey to be an integral component of any mimetic system is discussed.