J. Zoo!., Lond. (1983) 199, 157-170 The relation between maximal running speed and body mass in terrestrial mammals THEODORE GARLAND, JR. Department of Ecology and Evolutionary Biology, University of California, Irvine, Irvine, CA 92717, U.S.A. (Accepted 8 June 1982) (With 3 figures in the text) The available data on maximal running speeds of mammals are presented, and the relation- ship between speed and body mass is considered. For all mammals (n = I 06), maximal run- ning speed scales as (body mass)o- 11 ; however, the largest mammals are not the fastest, and an optimal size with regards to running ability is suggested ( = 119 kg). Maximal running speeds are, on the average, somewhat more than twice maximal aerobic speeds. Within the Artiodactyla, Carnivora or Rodentia, maximal running speed is mass indepen- dent, in agreement with theoretical expectations for geometrically similar animals (Thomp- son, 1917; Hill, 1950). McMahon's (1975b) model for elastic similarity is therefore not supported by the available data on maximal running speeds, and there appears to be no necessary correspondence between scaling of limb bone proportions and running ability. Introduction .. The data Statistical analyses .. Results and discussion Scaling of maximal running speed Contents Comparisons of running ability among groups .. Maximal running speed versus maximal aerobic speed .. Comparisons with theoretical expectations Summary References .. Introduction Page 157 158 159 159 159 165 166 167 168 168 It would not be surprising if animals of different sizes could attain different maximal running speeds. Exactly how running ability should scale with body mass (M) is not, how- ever, obvious, and four competing theories offer different predictions. The reader is referred to Gunther (1975) and McMahon (l 975b) for discussions of the assumptions involved in each theory. Thompson (1917) and Hill (1950) conclude that maximal running speed (MRS) should be mass independent among geometrically similar animals (cf. Gunther's, 1975 "kinematic similarity"). McMahon (1975b), however, argues that animals should be designed so as to meet the criteria of elastic similarity. Elastic similarity predicts that the speed at which animals will be running at their natural frequency will be proportional to 157 0022-5460/83/020157 + 14 $03.00/0 © 1983 The Zoological Society of London