What are the four main types of snake locomotion?

Snakes have developed four primary methods of locomotion to navigate their environments without limbs:1

• Serpentine locomotion: The most common method, where the snake forms S-shaped horizontal loops and pushes against environmental resistance (such as rocks or twigs) to move forward. This is also the method used for swimming.1
• Concertina locomotion: Used when surface friction is low, the snake anchors its tail and posterior body, extends its head and forebody forward, and then pulls the rear portion up to meet the new anchor point, resembling the movement of an accordion.12
• Rectilinear locomotion: Often used by heavy-bodied snakes, this method involves moving the body in a straight line. The snake uses sequential muscle contractions to lift, anchor, and push against its ventral scales, inching the body forward.13
• Sidewinding: Primarily used in desert environments where sand provides little traction, the snake lifts its body into loops and shifts them laterally, moving sideways rather than forward to minimize contact with hot surfaces.1