Prey death rates and rate of increase of arthropod predator populations

Abstract

CENTRAL to our understanding of predator–prey dynamics is the relationship between the death rate imposed on the prey by the predators and the rate of increase, or numerical response, of the predator population. Most of the familiar mathematical models of predator–prey systems involve the assumption that there is a simple linear relationship between the number of prey killed and predator reproduction^1–4. Although this assumption is valid for most insect host–parasitoid systems², the rate of increase of other predatory arthropods is a more complex function of the prey consumed. For successful reproduction, each instar must find and eat several prey to complete development. Thus the predator rate of increase will depend on the duration of, and the survival rate within each instar and the fecundity of the adults. Where models for the predator rate of increase have incorporated more complex nonlinear relationships^5,6, these relationships are of too abstract a character to allow simple experimental corroboratiqn or refutation. In this paper we propose models that characterise the effect of prey consumption on the components of the predator rate of increase that are specifically designed to relate our hypotheses to field or laboratory data.