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January 3 - Febuary 28, 2021

Meeting Abstract

73-11  Sat Jan 2  Kinematics of running across hard and granular surfaces in specialist and generalist lizards Tucker, EL*; Mantilla, DC; Hsieh, ST; Temple University, Philadelphia, PA; Temple University, Philadelphia, PA; Temple University, Philadelphia, PA

Terrestrial animals routinely encounter granular media, such as sand, dirt, or gravel. Granular media poses unique challenges to locomotion due to their changes between solid and fluid-like states as a response to differences in force application. Despite its ubiquity in the natural environment, it is still not well known how animals may be adapted morphologically or kinematically for running on hard versus granular surfaces. We ran three species of lizards representing a desert generalist (Crotaphytus bicinctores), a desert specialist (Callisaurus draconoides), and a fluid specialist (Basiliscus vittatus) along a 2 m long hard trackway and a fluidizable bed of poppy seeds (“sand”), while filming with a high-speed camera (Photron SA-3, 500 fps). We hypothesized that these lizards would run with similar velocity on the hard-flat trackway, however, desert and fluid specialists would outperform the desert generalists on sand. The sand proved to be a challenge for all three species of lizards. Desert specialists ran at similar speeds to fluid specialists but outperformed desert generalists. Both desert specialists and generalists ran slower on the sand than they did on the hard-flat surface. Failure to successfully compensate on sand resulted in higher duty factors for both species, with lower stride frequencies for the sand specialists and lower stride lengths for the desert generalists. The fluid specialists were able to maintain similar speeds between the two conditions, however, it displayed decreases in duty factor as well as stride length. While alteration of above ground kinematics explains some of the patterns that we are seeing in our results, it remains to be seen how adaptive foot use may be contributing to success across these two surfaces.