Snakes are vertebrates (like humans) and have a lot of them. A snake’s skeleton is primarily a skull, a jaw, and a very long, flexible backbone (vertebral column) made of hundreds of bones called vertebrae. Some snakes can have over 400!
Attached to most of these vertebrae are pairs of ribs. The key is what they don’t have:
- They don’t have limbs (arms or legs).
- They don’t have a sternum (breastbone).
This lack of a breastbone is what allows their ribs to move so freely and gives them incredible flexibility.
How They Actually Move (Using Their Bones)
The secret to a snake’s movement isn’t a lack of bones, but the unique way their bones, muscles, and scales work together. They move by using powerful, intricate muscles that connect their vertebrae and ribs to their skin.
Their underside is covered in wide, tough belly scales (called scutes). These scales act like the tread on a tire, gripping the ground.
The snake essentially “walks” on its ribs. Muscles lift a section of the belly, move the ribs forward, and then plant the scales down to grip the earth. They do this in waves along their body, which pushes them forward.
Main Types of Snake Movement
Snakes use this basic system of bones, muscles, and scales to move in four main ways, depending on the surface and their speed:
- Lateral Undulation (Serpentine): This is the classic “S”-shaped slithering. The snake pushes off of uneven surfaces (like rocks, sticks, or clumps of dirt) to propel itself forward.
- Rectilinear (Caterpillar): This is the “rib-walking” motion described above. The snake moves mostly in a straight line, like a caterpillar. It’s slow and stealthy, often used by large snakes like pythons and boas when stalking prey.
- Concertina (Accordion): The snake bunches up the middle of its body (like an accordion) to get a grip, then extends its front end forward. This is very common for climbing or moving through narrow tunnels.
- Sidewinding: This is a fast and efficient method used on loose, slippery surfaces like sand or mud. The snake throws loops of its body sideways, keeping only two or three points of its body on the hot or unstable ground at any one time.