Fig. 2.

Log₁₀ field energy expenditures of mammals as a function of log₁₀ body mass. The solid curve is for 79 species as measured by doubly labeled water (11). Data on the energy expenditure of 9 species of cold-water marine mammals indicate that their field expenditures average approximately twice those of terrestrial species. The curve for terrestrial species is extrapolated (dashed line) to the mass of an African elephant and a Paraceratherium, and the curve for marine mammals is extrapolated to the mass of a blue whale.