Fig. 1. Kleiber's original 1932 plot of the basal metabolic rate of mammals and birds (in kcal/day) plotted against mass (M_b in kg) on a log-log scale (Kleiber, 1975). The slope of the best straight-line fit is 0.74, illustrating the scaling of metabolic rate as M_b^3/4. The diameters of the circles represent his estimated errors of 10% in the data.