Linking functional responses and foraging behaviour to population dynamics

Abstract

INTRODUCTION This chapter reviews the connection between large herbivores and their food sources, and asks how the population dynamics of large herbivores are related to their foraging behaviour, diet selection and food intake. Large herbivores are a well‐studied group because they include cattle and sheep, which have been the subjects of a huge amount of agricultural research. Accordingly, much is known, or can be deduced, about their response to resources. It is useful to distinguish the way consumption rate responds to food abundance (i.e. the functional response) from the way the size of the consumer population responds to food consumption (the numerical response). The first two sections in the chapter review the mechanistic approach to describing the functional response, and its implications, and the next section discusses the modelling of the numerical response. The final two sections consider the relationship between large herbivore population dynamics and the selection and consumption of resources. RECENT MODELS OF FUNCTIONAL RESPONSE The functional response describes how a consumer's rate of food intake varies with the abundance of food. It is, therefore, a crucial link in consumer‐resource dynamics, as well as being fundamental to classical foraging models that predict the diet or patch residence time that would maximize intake rate. Hobbs et al . (2003) discuss and distinguish mechanistic models of functional response and more empirical approaches.