Energy Expenditure and Conservation in Frugivorous and Mixed-Diet Carnivorans

Rate of metabolism and body temperature of eight species of mammals belonging to the order Carnivora were measured. Five of these species are both arboreal and frugivorous, each of which has a low basal rate of metabolism. These species reduce heat loss and rate of metabolism at low environmental temperatures without a reduction in core body temperature, probably through a reduction in peripheral circulation. Carnivorans that exclusively eat vertebrates have high basal rates and those that mix vertebrates in their diet with fruit (the tayra) or invertebrates (the falanoka) have intermediate basal rates. These data provide further evidence that basal rate in mammals is correlated with food habits independent of phylogeny. In arboreal species, a reduction in rate of metabolism at low environmental temperatures and in basal rate may be required to compensate for the use of foods characterized by a seasonal scarcity (fruit, invertebrates) or a low available nutritional content (fruit, leaves). Reductions in rate of metabolism are greatest in the largest species, which reflects the increase of total energy requirements with mass. These reductions also are associated in arboreal species with sedentary habits and small muscle masses. The combination of a small muscle mass with particular food habits may set basal rate of metabolism in arboreal species. The influences of body mass, food habits, and activity level on basal rate are difficult to separate because of factor interaction.