Diet Selection by Grazing Animals

Abstract

The subject of diet selection by grazing animals is a vast one. Whilst it is widely acceptcd that there may be a set of generalized principles underlying foraging behaviour and diet selection by grazing animals. the current philosophy is to develop appropriate models to describe the grazing behaviour for observed sets of specific food distributions and grazers rather than to attempt to seek a generalized foraging theory. The present paper follows this current philosophy in considering only large vertebrate grazing herbivores, and specifically ruminants, within the context of predominately temperate pastures. The domesticated ruminant animals which have been studied most frequently, i.e. cattle, sheep, deer and goats, have adopted slightly different foraging strategies along the continuum of grazers, mixed grazers/browsers and browsers with cattle considered as grazers and goats being the nearest species to a browser. There are a number of animal variables which influence these foraging strategies and they can be seen as adaptations to particular diets which have arisen over evolutionary time or as a result of selection imposed by man (Gordon & Iason, 1989).