Linking Predation Risk Models with Behavioral Mechanisms: Identifying Population Bottlenecks

Abstract

A comprehensive understanding of the factors controlling predation risk in natural communities is dependent upon knowledge of both the patchiness of predator and prey populations in nature, and on the outcome of behavioral interactions between predator and prey individuals. While both of these areas of predation ecology are rich in theory and data, there are no models that permit these two fundamental components of predation risk to be combined in a quantitative way. Here a model is developed to combine these density risk and prey vulnerability components of predation. The model is used to estimate the contribution of predator and prey population overlap to predation risk, and to quantify both density risk and prey vulnerability components of predation risk for two planktonic invertebrate predators and five rotifer prey. Behavioral data from the literature are used to interpret the prey vulnerability values and demonstrate the utility of the model. The predation risk value obtained for each prey species also are compared to the intrinsic population growth rates (°max), taken from previous studies. In addition, I test the a priori hypothesis that prey population growth will be negative when predation risk exceeds °max. The results reveal the presence of severe bottleneck periods where predation risk exceeds the °max of four of the five prey species, thus supporting the a priori prediction of negative population growth or extremely how prey populations during these periods.