The distribution of 66 spcies of mammalian primary consumers in a Gabon rain forest is analysed by broad categories of habitat, height, activity cycle, diet and body weight. Aa few species are restricted to waterside habita; most inhabit dry-land forest. Species are almost equally divided between the roles of arboreal and terrestrial, diurnal and nocturnal, but there are five times as many frugivores as folivores. Terrestriality, large body size, and folivory are correlated with mixed diurnal-nocturnal activity. Frugivores ahve a wider range of ecological roles than folivores. Different taxa have radiated in similare patterns, suggesting similar ecologcical constraints on the diversification of different families.