Sprint Sensitivity to Substrate and Ecomorphological Correlates in Six Terrestrial Lizard Species

Sprint performance is important to terrestrial lizards for predator evasion, prey acquisition, and fitness. Because many terrestrial species encounter a variety of substrates during locomotion, relationships between morphology, performance, and habitat use are ripe for research. Results from previous studies suggest increased limb length and sprint speed is correlated with saxicoly. Results from studies on locomotion over compliant surfaces such as sand, however, are less clear despite psammophily likely imposing selective pressure. Sprint sensitivity, or the variation in sprint performance due to differences in habitat or substrate use, has been useful in studies of arboreal lizards. This study measured sprint sensitivity among six terrestrial lizard species that occupy rocky, sandy, and/or semi-arboreal habitats. We quantified maximum velocity as each lizard accelerated from a standstill and ran down a 5 meter runway constructed in the field. Each animal was run three times on each of three substrate types (Runway A – sand (200mm). All runs were videotaped and reviewed to estimate maximal velocity over 5 meters. We infer from our results reduced sprint sensitivity saxicolous lizards. Higher overall velocity, yet greater sprint sensitivity, was observed in lizards that predominately use sand substrates. Here we use our results to discuss the evolutionary implications of differential substrate use in terrestrial lizards including morphology, locomotor capacity, and habitat selection.