A snake that moves across a loose substrate, such as sand or mud, by throwing its body in a looping motion so that it progresses approximately at right angles to its body axis. Several species use this method of locomotion including the sidewinder rattlesnake (Crotalus cerastes) of the south-western USA, and the horned adder (Bitis caudalis) and Peringuey’s adder (B. peringuey) of south-western Africa. All are small, venomous snakes.