Numerical Model of the Slithering Snake Locomotion Based on the Friction Anisotropy of the Ventral Skin

Snakes are able to dynamically change their frictional interactions with a surface by at least three different methods: (1) adjusting the attitude of their scales, (2) redistributing their weight at various points of contact with the substrate, and (3) changing of their winding angles. In the present study, we have observed that snakes change their winding angles, when either friction anisotropy is suppressed by particular roughness of the substrate, or when the external force displacing snake overcomes friction resistance during their locomotion on inclines. In order to understand this behaviour and may be even to predict the specific way of the snake locomotion depending on the interactions between the ventral surface of the snake skin and the substrate, numerical modelling was undertaken. Adaptation of the winding curvature considered in the present study has something to do with an enhancement of friction anisotropy in critical behavioural situations, such as on low-friction substrates or while moving up and down a slope.