Relative brain size and basal metabolic rate in terrestrial vertebrates

Re-examination of brain–body size relationships for large samples of species from three major vertebrate groups now shows that there is no empirical foundation for the concept of scaling to body surface area, and it seems that brain size may be linked to maternal metabolic turnover.

Abstract

Studies of the relationship between brain size and body size in terrestrial verteberates have a long history1–4. Demonstrations of regular relationships between brain and body size across species within selected vertebrate groups serve two purposes: (1) in comparison of species of different body size, empirically recognized 'scaling effects' can be taken into account; (2) empirical relationships may suggest useful working hypotheses regarding functional constraints (although they cannot directly reveal casual connections). It is widely accepted5,6 that brain size is scaled to keep pace with changes in body surface area (rather than volume), and this provides the basis for many interpretations of relative brain size. Re-examination of brain–body size relationships for large samples of species from three major vertebrate groups (mammals, birds, reptiles) now shows that there is no empirical foundation for the concept of scaling to body surface area. Instead, it seems that brain size may be linked to maternal metabolic turnover. This has implications not only for assessment of relative brain size in particular species, but also for pursuing links between brain size and 'life strategies'.