Body Size, Brain Size and Feeding Strategies

Abstract

The concept of allometry (non-linear scaling of individual biological parameters to body size) has been applied repeatedly, if somewhat intermittently, to morphological characteristics for almost a century. Particular interest has focused on brain size, beginning with the studies of Snell (1892) and Dubois (1897) and culminating in Jerison’s landmark treatise (1973), in which allometric analysis provided the foundation for consideration of the evolution of the brain throughout the vertebrates. Only relatively recently, however, has body size been taken into account explicitly as a factor involved in the behavioural/ecological relationships of vertebrates. For mammals, McNab (1963) was the first to examine home range size in relation to body size according to well-defined allometric principles. Subsequently, this and other aspects of ranging behaviour have been subjected to detailed allometric analysis by several authors, notably with respect to the primates (e.g. Milton and May, 1976; Clutton-Brock and Harvey, 1977a, 1977b; Martin, 1981a; Harvey and Clutton-Brock, 1981; Gittleman and Harvey, 1982; Mace and Harvey, 1982). Further, there have been a number of recent studies suggesting a link between brain size (relative to body size) and specific aspects of behavioural ecology in primates and other mammals, particularly with respect to feeding behaviour (e.g. Pirlot and Stephan, 1970; Eisenberg and Wilson, 1978, 1981; Clutton-Brock and Harvey, 1980; Harvey et al., 1980; Mace et al., 1981; Mace and Eisenberg, 1982). All of these studies together have helped to place comparative studies of primate behavioural ecology on a more secure footing; but there are a number of inherent problems involved in the interpretation of the results of such allometric analyses. One of the main aims of this paper is to outline those problems and to discuss some of their implications.