Body Size, Diet, and Population Density of Neotropical Forest Mammals

Abstract

The population densities of Neotropical mammalian species are predictably related to their body masses and diets. In interspecific comparisons, population densities generally declined with increasing body mass, and declined with body mass within each of seven specified dietary categories. In our regression analyses, body mass alone accounted for approximately half of the variation in density in the general case, and a greater proportion of the variation in five of the regressions within dietary categories. Pairwise comparisons using stepwise multiple regression indicated that adding diet as well as body mass significantly increased the proportion of variance explained. Finally, the magnitude of the effect of body mass on population density varied with dietary class. These results indicate that, in general, larger-bodied species occur at lower densities than smaller-bodied species, and species with restricted diets and those at higher trophic levels occur at lower densities than species whose diet allows them access to a greater abundance of food resources. The decline in density with increasing body size is greater within some dietary categories than others. The results broadly support the hypothesis that population densities of species are determined by the potential resources, and ultimately energy, available to them in specified habitats.