Prospects for Further Development of Resource Ecology

This book is about ‘resource ecology’, which we defined in our introductory chapter as “the ecology of trophic interactions between consumers and their resources”. We have chosen to focus on a particular class of consumers, namely, large mammalian placental herbivores. All chapters in this book deal actually with ungulates (in the broad sense, thus including elephant), whether free-ranging or domestic, but we are certain that every chapter is of much use to understand other classes of herbivores, such as marsupials, herbivorous birds or even herbivorous reptiles. In the comment on Chapter 4, the definition of ‘resource’ is given as “usable energy or any biotic or abiotic substance directly exploited by an organism, which includes food, nutrients, water, atmospheric gas compounds, as well as light, and the use of which can lead to the (temporary) exhaustion of that resource”. The essence of the concept of ‘resource’ is that organisms can compete for a resource and that it can be limiting the growth of individual organisms or of populations. In herbivores, the resource that is most interesting from a conceptual point of view, is herbage, because the feedback relations that exist between consumers and this type of resource (see for instance Van de Koppel et al. 2002; Rietkerk et al. 2002a; Van Langevelde et al. 2003). This of course does not deny the fact that other resources, such as water, or environmental conditions, such as temperature, can be very important factors to understand the distribution of herbivores (Bailey and Provenza, Chapter 2; Stein and Georgiadis, Chapter 3). From the consumer's perspective, acquiring sufficient resources, such as energy, nutrients and water, are conditions for life and reproduction. In resource ecology, foraging is the central process because it leads to growth, survival and reproduction of the animal. This book deals with foraging, and it ignores predation or disease and highlights only a restricted set of fitness parameters of the consumer.