Meeting Abstract
In the wild, animals encounter substrates varying in material properties and orientation. Feet have been shown to be more sensitive to changes in substrate properties by displaying posture and resilience adjustments on level granular and solid substrates. However, little is known about legged locomotion on inclined granular substrates, such as sand dunes, which fluidize with every step. It would therefore be reasonable to expect sand specialists to have kinematic adaptations for running on granular substrates, and fluid specialists to run well on sand due to its fluidizing properties. Previous results show that although running speeds are similar on the level granular substrate, sand specialist lizards consistently run faster than both generalist and fluid specialist lizards on the incline, with fluid specialists performing the most poorly. Here, we quantify how the kinematics differ among species and between surface angles. We ran a sand specialist (Callisaurus draconoides), a fluid specialist (Basiliscus vittatus), and a generalist (Crotaphytus collaris) along a level and incline (31°) fluidizable bed trackway. Lizards were filmed at 500 fps (Photron SA-3), and videos were analyzed in MATLAB. All three species similarly decreased impact speed on the incline compared to the level (P<.001). Sand and fluid specialists increased their impact angle on the incline (P<.01), whereas generalists did not. These results show that above surface kinematics seem to have little effects on running performance among these species. Instead, subsurface foot interactions and subtle differences in foot morphology may vastly alter force generation and solidification patterns when running on granular substrates.
