GREGORY, M L*; CLAUSSEN, D L; Miami University; Miami University: Scaling of speed with body mass in terrestrial chelonians

Although scaling can reveal some interesting correlates between body size and locomotor performance, only a few turtle species have heretofore been examined. We recorded maximal speeds of 17 species of adult terrestrial chelonians (N=77) and evaluated these in relation to body size. Absolute speeds tended to increase overall as mass increased, whereas relative (size-adjusted) speeds decreased. The fastest absolute speeds were observed in mid to large-bodied species (>5 kg) and the fastest relative speeds in small-bodied species (<5 kg). Aldabran giant tortoises (Geochelone gigantea) exhibited absolute speeds averaging 0.11 meters per second and relative speeds averaging 0.10 body lengths per second, whereas the corresponding speeds for the tiny Clemmys and Glyptemys were 0.15 meters per second and 1.22 body lengths per second. Both absolute and relative speeds of individuals tended to decrease with increasing mass within large-bodied species, but not within mid- and small-bodied species. These patterns may result from differential predation pressures: small genera are subject to intense predation during all life stages, whereas, given their great size and rapid growth, giant tortoises have little need to move quickly.