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 li zards in an attempt to understand size-dependent variation of locomoto r patterns. Scaling of body dimensions to body mass revealed that axia l measures conformed to geometric similarity, whereas the limb segment s exhibited an allometry which was statistically significantly less th an geometric similarity. Variations in the relationships between strid e lengths, stride frequencies and duty factors (% of the stride that f oot contacts ground) represented locomotor specializations and were no t strictly size-dependent among species. At body length equivalent vel ocities, stride length and stride frequency scaled to body mass(0.40+/ -0.06 and 0.09+/-0.03), respectively. Cost during locomotion at body l ength equivalent velocities could be estimated by the square of the pr oduct 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 ma ss(0.62+/-0.11). An estimate of the mass-specific cost during locomoti on at body length-equivalent velocities scales to mass(-0.38+/-0.11). Because the limbs of these lizards exhibit an allometry less than geom etric similarity, a correction of the estimate of the mass-specific co st during locomotion could be obtained by factoring in the effect of i ncreased locomotor costs associated with relatively shorter pelvic lim bs in larger lizards. The allometrically corrected estimate of the mas s-specific cost during locomotion was proportional to mass(-0.31). Thi s estimated regression, which is the relative cost of transport for a single, morphologically conservative Family of lizards, predicts a slo pe quite close to that derived from studies of oxygen requirements dur ing locomotion in lizards of several families (slope = -0.28, John-Ald er, Garland and Bennett, 1986) and in mammals (slope = -0.32, Taylor, Heglund and Maloiy, 1982).