The Zoogeography of Mammalian Basal Metabolic Rate

Zoogeographical effects on the basal metabolic rate (BMR) of 487 mammal species were analyzed using conventional and phylogenetically independent ANCOVA. Minimal BMR variance occurred at a "constrained body mass" of 358 g, whereas maximum variance occurred at the smallest and largest body masses. Significant differences in BMR were identified for similar-sized mammals from the six terrestrial zoogeographical zones (Afrotropical, Australasian, Indomalayan, Nearctic, Neotropical, and Palearctic). Nearctic and Palearctic mammals had higher basal rates than their Afrotropical, Australasian, Indomalayan, and Neotropical counterparts. Desert mammals had lower basal rates than mesic mammals. The patterns were interpreted with a conceptual model describing geographical BMR variance in terms of the influence of latitudinal and zonal climate variability. Low and high basal rates were explained in unpredictable and predictable environments, respectively, especially in small mammals. The BMR of large mammals may be influenced in addition by mobility and predation constraints. Highly mobile mammals tend to have high BMRs that may somehow facilitate fast running speeds, whereas less mobile mammals are generally dietary specialists and are often armored. The model thus integrates physiological and ecological criteria and makes predictions concerning body size and life-history evolution, island effects, and locomotor energetics.