Ten species of ungulate were filmed, galloping in their natural habitat. They ranged in size from Thomson's gazelle (about 20 kg) to giraffe (about 1000 kg). They were pursued to make them run as fast as possible. The films have been analysed to determine speed, stride frequency, stride and step lengths, and duty factors. The dependence of these quantities on body size is discussed. Summary: Fast locomotion of zebra, giraffe, warthog and seven species of Bovidae has been studied. The animals were filmed from a pursuing vehicle while galloping in their natural habitat. Stride frequency was more closely correlated with limb length (represented by hip height) than with body mass. Mean stride frequency was proportional to (hip height)‐0·51 and maximum stride frequency to (hip height) ‐0·63. Maximum speed was between 10 and 14 m s ‐1 for all species except buffalo (7 m s ‐1). It was not significantly correlated with body mass. Since the small species ran at least as fast as the large ones they attained higher Froude numbers. Relative stride length was approximately 1·8 (Froude number)0·39 for all species, irrespective of size. Relative step length was approximately 0·65 (Froude number)0·2, both for the fore feet and for the hind ones. The vertical forces exerted by the feet are proportional to (body weight)×(Froude number)0·2 so the forces at maximum speed are larger multiples of body weight for small species than for large ones.

SUMMARYBody mass is the primary determinant of an animalʼs energy requirements. At their optimum walking speed, large animals have lower mass-specific energy requirements for locomotion than small ones. In animals ranging in size from 0.8g (roach) to 260kg (zebu steer), the minimum cost of transport (COT min ) decreases with increasing body size roughly as COT min ϰbody mass (M b ) -0.316±0.023 (95% CI). Typically, the variation of COT min with body mass is weaker at the intraspecific level as a result of physiological and geometric similarity within closely related species. The interspecific relationship estimates that an adult elephant, with twice the body mass of a mid-sized elephant, should be able to move its body approximately 23% cheaper than the smaller elephant. We sought to determine whether adult Asian and sub-adult African elephants follow a single quasi-intraspecific relationship, and extend the interspecific relationship between COT min and body mass to 12-fold larger animals. Physiological and possibly geometric similarity between adult Asian elephants and sub-adult African elephants caused body mass to have a no effect on COT min (COT min ϰM b 0.007±0.455). The COT min in elephants occurred at walking speeds between 1.3 and ~1.5ms . The quasi-intraspecific relationship between body mass and COT min among elephants caused the interspecific relationship to underestimate COT min in larger elephants.

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