Friday, March 13, 2009

How Snakes Move : Musculature and Locomotion

The muscles of the snake are utilized both to move ingested prey internally and for general body movement, or locomotion. There are four basic types of locomotion in snakes:

Serpentine or lateral progression: This form of locomotion is the undulating crawl, commonly called 'slithering,' and the most common form of movement amongst snakes. It allows the snake to reach maximum speeds and is employed by all water snakes to swim.

Rectilinear or Caterpillar Movement: Large and heavy snakes use the caterpillar movement or "inchworm", keeping their bodies in a fairly straight position while successive groups of belly scales are erected, angled forward, then pressed back against the ground. This functions as a lever to move the snake smoothly along. Large size boas, pythons, and vipers use this type of movement because their weight gives them a better grip on the ground.

Sidewinding: Snakes that live in hot deserts on loose sand use this type of adaptive locomotion, hurling their bodies in a sideways looping motion, called "sidewinding." Basically, to achieve the least body contact with hot ground at one point of time. So, the main thrust is sideways rather than backwards. Only three parts of a sidewinder's body are in contact with the ground at any one time. This prevents the snake's belly from resting on the desert sand long enough to become painfully hot. Sidewinding snakes will leave an "S" trail in the sand. photo

Concertina: Some snakes apply the concertina technique when climbing trees. The body bunches up forming horizontal loops and then the head moves forward and the body straightens, similar to an accordion or spring. A "concertina" movement is also used in narrow tunnels, vertical pipes in buildings or burrows. In this movement the snake wedges his coils against the sides of the tunnel and extends the rest of his body.
A snake's flexibility depends upon its many muscles. These are long chains of muscles along the vertebrae, connecting the vertebra, from rib to rib, and from rib to vertebrae. Their skin muscles allow the ribs to pull scales forward and backward, which help the snake to move. Snakes are incapable of significantly lengthening and shortening their total body length because they do not have a hydrostatic skeleton. They get the same effect by throwing their bodies into coils. The wider the coils, the faster they move.

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