Figure 1 shows an adult Ceratotherium galloping at 6.1 m/s. Other sequences (also of adults) show speeds up to 7.5 m/s. This is slightly above the maximum speed of 7.0 m/s recorded for butfalo (Syncerus cafferr) by Alexander, Langman & Jayes (1977), but well below the 11 m/s which they recorded for giraffe. The highest speed shown for Loxodonta in the film analysed by Alexander, Maloiy et al. (1979) was only 4-5 m/s, but this may not have been a maxmum speed. Other records of elephant speeds seem to be subjective estimates rather than measurements (Garland, 1983). Previous analysis of our film by Alexander & Jayes (1983) showed that Ceratotherium change from trotting to galloping at about the same Froude number (a dimensionless speed parameter) as other cursorial mammals. At any particular Froude number they use about the same duty factor and relative stride length as other cursorial mammals. They are restricted to fairly low Froude numbers but, within the range available to them, move very much like smaller mammals.
Ceratotherium simum - 2 year old female in zoo. We were unable to weigh the carcass on account of its size, but the zoo staff who had attended the animal estimated her mass as 700-800 kg. The following argument tends to confirm their estimate. The unskinned carcass was 2.76 m long from the upper lip to the base of the tail, measured along the midline of the back. The foreleg was 1.55 m long from the withers to the sole of the foot, measured along the surface of the skin. We made the corresponding measurements on plastic models of rhinoceroses, manufactured by Britain's Ltd., and calculated the ratios of carcass dimensions to model dimensions. The cubes of these ratios gave estimated ratios of volumes, and since we had determined the volumnes of the models (by measuring the upthrust that acted on them, when they were submerged in water) we were able to estimate the volume of the animal. From this the mass was calculated, assuming a density of 1000 kg/m3. Unfortunately, no model of Ceratotherium was available, so we had to use models of Diceros and of Rhinoceros unicornis. The mass estimates derived from these were 630 and 890 kg, respectively. Diceros seems to be more slender than Ceratotherium and Rhinoceros more portly, so we estimate the mass of the Ceratotherium as 750 kg, in excellent agreement with the subjective estimate. As a check on the method, we used the Diceros model to estimate the masses of 3 of the Diceros listed by Mcinertzhagen (1938), from the linear dimensions given by him. The estimates were 1.02, 0.91 and 0.96 times the actual masses.
