Locomotor kinematics on sand versus vinyl flooring in the sidewinder rattlesnake Crotalus cerastes

Abstract

For terrestrial locomotion of animals and machines, physical characteristics of the substrate can strongly impact kinematics and performance. Snakes are an especially interesting system for studying substrate effects because their gait depends more on the environment than on their speed. We tested sidewinder rattlesnakes (Crotalus cerastes) on two surfaces: sand collected from their natural environment and vinyl tile flooring, an artificial surface often used to elicit sidewinding in laboratory settings. Of ten kinematic variables examined, two differed significantly between the substrates: the body's waveform had an average of ∼17% longer wavelength on vinyl flooring (measured in body lengths), and snakes lifted their bodies an average of ∼40% higher on sand (measured in body lengths). Sidewinding may also differ among substrates in ways we did not measure (e.g. ground reaction forces and energetics), leaving open clear directions for future study.

Functional diversity of snake locomotor behaviors: A review of the biological literature for bioinspiration

“…Several researchers have put forth models of sidewinding locomotion grounded in data from sidewinding snakes, which have allowed snakelike robots to more effectively replicate a range of functions that sidewinding snakes can perform, including ascending slopes, turning, and negotiating obstacles. [17][18][19][20] Additional studies address a variety of additional questions related to sidewinding in living snakes, including muscular mechanisms, 78 maximal performance, 79,80 the exceptionally low energetic cost, 80 among-species kinematic differences, 33,81 within-species kinematic differences, 82 scaling of kinematics with body size, 82 and substrate effects on kinematics 83 (for a systematic review of the literature on sidewinding through 2019, see Ref. 84).…”

“…Some snakes, particularly sidewinding specialists, may successfully negotiate these surfaces because their locomotor strategy for overcoming slipping on sand also mitigates slipping on vinyl or other such artificial surfaces. 83 Lacking the ability to sidewind, many species resort to either flat-surface concertina 33 or lateral undulation 41 when placed on smooth, rigid surfaces. In this latter case, frictional anisotropy and lifting of certain body segments (sinus lifting) may allow some measure of forward progression, 41 though with far more slipping and far less economy of motion than slithering in natural terrain; below a certain level of friction, snakes may simply become stuck.…”

“…Observations of snakes moving despite slippage on roads and polished floors prompted a description of a gait called slide-pushing, 31,32,178 which is no more a natural mode of snake locomotion than ice-skating is a natural mode of human locomotion. While such artificial conditions can be useful experimental perturbations to explore mechanics and control, 41,83,88 the irrelevance to natural behavior means the results of such experiments should be used only with caution during the process of bioinspired design.…”