Energy metabolism and body size. I. Is the 0.75 mass exponent of Kleiber's equation a statistical artifact?

The statistical derivation of Kleiber's 0.75 interspecific mass exponent 'b' is based on an assumption that the mass coefficient 'a' is constant irrespective of a mammal's size and/or species. Analysis of covariance, a statistical technique not based on this assumption, reveals that the mass coefficient is not constant in a series of 7 species (Peromyscus m., mice, rats, cats, dogs, sheep, and cattle) but increases threefold with the size of the animal. THe mass coefficient is a power x mass-2/3, the power being expressed in watts and the mass in kg. (Peromyscus m.: a = 1.91 +/- 0.09; cattle: a = 6.06 +/- 0.14). The intragroup mass exponent is equal to 0.67 +/- 0.03 and is significantly different from 0.75. This study shows that the 0.75 interspecific mass exponent in Kleiber's equation is a statistical artifact and suggests that the data from literature are consistent with the theory of biological similitude of Lambert and Teissier.