Locomotor patterns and costs as related to body size and form in teiid lizards



Stride parameters and gaits were examined in seven species of teiid lizards in an attempt to understand size-dependent variation of locomotor patterns. Scaling of body dimensions to body mass revealed that axial measures conformed to geometric similarity, whereas the limb segments exhibited an allometry which was statistically significantly less than geometric similarity. Variations in the relationships between stride lengths, stride frequencies and duty factors (% of the stride that foot contacts ground) represented locomotor specializations and were not strictly size-dependent among species. At body length equivalent velocities, stride length and stride frequency scaled to body mass0.40±0.06 and 0.09±0.03, respectively. Cost during locomotion at body length equivalent velocities could be estimated by the square of the product of stride length and stride frequency. Plotting the cost during locomotion for geometrically similar lizards against body mass yielded an estimate of the cost during locomotion that was proportional to mass0.62±0.11. An estimate of the mass-specific cost during locomotion at body length-equivalent velocities scales to mass−0.38±0.11. Because the limbs of these lizards exhibit an allometry less than geometric similarity, a correction of the estimate of the mass-specific cost during locomotion could be obtained by factoring in the effect of increased locomotor costs associated with relatively shorter pelvic limbs in larger lizards. The allometrically corrected estimate of the mass-specific cost during locomotion was proportional to mass−0.31. This estimated regression, which is the relatiue cost of transport for a single, morphologically conservative family of lizards, predicts a slope quite close to that derived from studies of oxygen requirements during locomotion in lizards of several families (slope= -0.28, John-Alder, Garland & Bennett, 1986) and in mammals (slope= -0.32, Taylor, Heglund & Maloiy, 1982).