The Distribution and Abundance of Animals [antikvár]

CHAPTER 1 The Scope of Ecology In solving ecological problems we are concerned with what animals do in their capacity as whole, living animals, not as dead animals or as a series of parts of animals. We have next to study the circumstances under which they do these things, and, most important of all, the limiting factors which prevent them from doing certain other things. By solving these questions it is possible to discover the reasons for the distribution and numbers of animals in nature. ELTON (1927, p. 34) 1.0 the two sorts or ecology In its full context the quotation which heads this chapter emphasized the difference between the older disciplines of anatomy, histology, taxonomy, physiology, etc., and the newer one of ecology, in which, as Elton said, we have to study the living animal in the circumstances in which it is found in nature. Our purpose, in doing this, is to explain why a certain kind of animal is found in certain areas but not in others; why they are numerous in one place but scarce in another; why they are more numerous this year than they were last; and so on. This problem has been tackled in two very different ways. It was appreciated from the very first that the same, or a similar, group of species is likely to be found in the same sort of "habitat" (see sec. 2.2 for the meaning of "habitat"). So it became popular to study these communities of animals; and to many it has seemed as if this were the very essence of ecology. In order to help with the study of communities, Elton (1927, p. 63) used the term "niche." The best way to indicate briefly the scope of community ecology is to explain the meaning of "niche." In the paragraph in which he used this term Elton said that all communities of plants and animals have a similar ground-plan; they all have their herbivores, carnivores, and scavengers. In a wood there may be certain caterpillars which eat the leaves of trees, foxes which hunt rabbits and mice, beetles which catch springtails, and so on. "It is convenient to have some term to describe the status of an animal in its community, to indicate what it is doing and not merely what it looks like, and the term used is 'niche.' . . . The 'niche' of an animal means its place in the biotic environment, its relations to food and enemies." Thus the caterpillar and the mouse broadly occupy similar niches because they eat plants; the fox and 3