Relations between Individual Size and Mammalian Population Density

Abstract

Regression relations which describe the density of mammalian populations as functions of adult body mass were built using data for carnivores and herbivores from four continents. Global and temperate relations are similar to previous descriptions: herbivores are more abundant than carnivores and population density declines as body size increases. Regressions within biogeographic regions support this pattern but depart in detail. North American species are more abundant than tropical species and species from tropical America and central Africa are more abundant than mammals from East Africa and southern Asia. Within regions, herbivore density is less affected by size and presumably more affected by other factors than the global regressions would suggest. Although the general regressions explain approximately 70% of the variance in animal density, more geographically restricted relations are less successful and none of the regressions are effective tools for the prediction of the abundance of individual populations. However, the mean tendency of population density described by these regressions can be of use in depicting the probable role of different-sized mammals in community structure and dynamics.