Meeting Abstract
The Mojave Shovel-nosed Snake (C. occipitalis) is a small (~40 cm, ~18 g) desert-dwelling sand specialist which travels on the surface of sand with low slip and high speed using a stereotyped undulatory gait—a traveling wave of sinusoidal body curvature with fixed amplitude and number of waves. These animals also encounter obstacles such as plants and rocks. To test how this behaviorally rigid animal contends with such heterogeneities and if it is helped or hindered by them, we study in the laboratory the locomotion of the snakes (N=8) through a model of twig-like obstacles—a single row of six 0.64 cm diameter stiff rubber pegs 2.3 cm apart oriented perpendicular to the animals’ direction of motion. To enable effective locomotion, we embedded the pegs in a carpet substrate which mimics deformable sand but without complications such as substrate hysteresis. Despite inability to see (the spectacles were painted with non-toxic acrylic), the animals rapidly transited through the pegs (the speed exiting the pegs was ~0.62 to 1.1 times the initial speed). To understand how performance was maintained, we measured the angular distribution of the reaction forces via video observation of small peg deflections. Forces were rarely applied along the direction of motion (forward or backward). This suggests that, unlike generalist snakes, the specialist C. occipitalis does not modify its waveform to use the obstacles, instead relying on substrate deformation. In contrast, force was generated perpendicular to the motion. To determine the origin of this force pattern, we studied the dynamics of a robotic snake transiting an array of posts. We observed a similar force pattern in the robot further supporting the notion that the snake does not drastically modify its neuromechanical control during obstacle interaction.
