The Strategy of Body Size in Mammalian Carnivores

Techniques of statistical analysis are utilized to begin to unravel the causes involved in the evolution of body size clines in mammalian carnivores. Variables included are productivity, temperature, latitude, competitive pressure and size of potential prey. Temperature and latitude are shown to be good predictors of body size in several species. Indeed, they seem to be measures of the same cause, as has long been maintained by those attempting to explain Bergmann's rule. But temperature does no better than latitude at predicting size. Thus temperature is probably not a direct cause of Bergmann's rule in these animals. The measure of total primary productivity used (actual annual evapotranspiration, AE) proved to be one of the better corre- lates, especially at lower productivities. Apparently relatively meager food supplies set upper limits to, body size. Except in a very few cases, the biotic variables of competitive pressure and prey size were only second-rate predictors. Discussion of the patterns that have been shown by this analysis is included.