Meeting Abstract
Snakes inhabit and move successfully within a wide range of environments, from sandy to rocky substrates, forest floors to tree trunks and branches, swampy areas to aquatic environments, and environmental interactions are mediated solely through skin contact. We performed atomic force microscopy (AFM) measurements to characterize the microscopic structures on the shed skins of a variety of viperid snakes that inhabit a diversity of environments. We find that, while most snakes have microfibrils oriented from head-to-tail, a few distantly-related snake species have convergently lost this structure in favor of a more isotropic morphology. We hypothesize that these microstructures affect the frictional interaction with the substrate and we use resistive force theory to model the effects of isotropic and anisotropic frictional interactions on snake locomotion. For lateral undulation, we find that an anisotropic frictional interaction in which craniad, or foreward, movement is favored over side-to-side movement is predicted to improve performance (measured in distance traveled per cycle), and that larger anisotropies yield larger displacements. In sidewinding locomotion, however, we see the opposite trend: more isotropic frictional interactions are predicted to improve performance. These predictions are consistent with our observations of microscopic structures on snake skins and provide a hypothesis for why sidewinding species of vipers share an evolutionarily convergence in morphology that is structurally distinct from other viperids examined.
