Abstract: Snakes propel themselves over land using a variety of techniques, including sidewinding, lateral sinuous slithering and a
unidirectional accordion-like mode. We explore these friction-based propulsion mechanisms through a combined experimental and theoretical investigation. Particular attention is given to classifying the gaits of snakes according to Froude number and the relative magnitudes of the frictional forces in the tangential and normal directions. Using mathematical modeling, we prescribe the waveform of the snake and calculate its motion as required by the torque and force balances on its body. A key feature of our model is the rationalization of snake motion on the basis of frictional properties of the snake’s belly scales. The prospect of building synthetic snake scales for robotic applications is discussed.