Meeting Abstract
Snakes can traverse heterogeneous terrain composed of rocks, foliage, soil and/or sand. Previous research elucidated how rigid obstacles influence snake locomotion by studying a model heterogeneous terrain—symmetric lattices of obstacles placed in hard ground. We want to understand the benefits and tradeoffs of different substrate-body interaction modes during transit of substrates composed of rigid obstacles and flowable (granular) substrates in desert-adapted snakes. We hypothesize that, due to these snakes’ ability to utilize granular resistive forces, introducing a granular medium (GM) to a peg lattice will improve performance (in terms of snake speed) compared to that in the same lattice on a hard substrate. We tested Chionactis occipitalis, the Mojave shovel-nosed snake, in a square lattice of 0.64 cm diameter obstacles arrayed on both a hard, slick substrate and in a GM of 270±4 μm diameter glass particles (comparable in size to natural sand). We challenged the snakes to move through lattices of different densities such that nearest-neighbor spacing ranged from slightly wider than the body diameter to larger than the snakes’ natural amplitude. Increasing obstacle density in the GM lattices resulted in a decrease in mean forward speed above a critical density. Below this density, speed was constant and comparable to that on open GM. In lattices on hard substrates, density did not affect speed; the speed in the densest lattice was comparable to that on open hard ground. This speed was a factor of two lower than the speed on open sand (P=0.98). Kinematics were similar for both substrates but depended on lattice density: at low density, undulatory locomotion was typically used while at high density a more complicated time-dependent body shape emerged.
