Theory: the numbers of animals in natural populations

Abstract

Animals are usually distributed patchily. Even when one arbitrarily selects what seems to be a uniform small area one finds that the animals are not distributed uniformly or even randomly over it; they tend to occur in ‘clumps’. This may be partly explained by accidents in the history of the population, by the behaviour of the animals (e.g. gre- gariousness) or by the heterogeneity of the terrain (section 10.3). The last-named cause becomes increasingly important as the area becomes large. In large areas, of the order that we usually choose for a practical ecological investigation, irregularities of terrain are pronounced and this, in itself, leads to ‘colonial’ or ‘clumped’ distributions of the animals in the area (Elton, 1949). For a description of an extremely colonial distribution see the passages quoted from Cockerell in section 3.12 and Flanders in section 10.44. See also section 10.45.