The mechanics of slithering locomotion

TLDR

Previous studies assumed snakes slither by pushing laterally against rocks and branches. The study investigates slithering of snakes on flat surfaces and develops a theoretical model based on kinematics and friction measurements. The authors model slithering locomotion by observing snake kinematics and measuring snakeskin friction coefficients. Predictions of body speed agree with observations, showing that propulsion relies on frictional anisotropy of scales and that weight distribution in lateral undulation is crucial, a principle that also improves limbless locomotion.

Abstract

In this experimental and theoretical study, we investigate the slithering of snakes on flat surfaces. Previous studies of slithering have rested on the assumption that snakes slither by pushing laterally against rocks and branches. In this study, we develop a theoretical model for slithering locomotion by observing snake motion kinematics and experimentally measuring the friction coefficients of snakeskin. Our predictions of body speed show good agreement with observations, demonstrating that snake propulsion on flat ground, and possibly in general, relies critically on the frictional anisotropy of their scales. We have also highlighted the importance of weight distribution in lateral undulation, previously difficult to visualize and hence assumed uniform. The ability to redistribute weight, clearly of importance when appendages are airborne in limbed locomotion, has a much broader generality, as shown by its role in improving limbless locomotion.