Most animals that live on land rely on their legs or wings to get around. And winged creatures like birds and insects even have legs that help them get from one place to another. But that's not so with snakes. They have no legs to help them move around, so how do they do it?
You probably know snakes slither, but do you know how they slither? It turns out it depends on the snake, the habitat they are in and what is happening around them. Snakes can move in one of four ways: serpentine movement, sidewinding locomotion, rectilinear progression or concertina movement. Most snakes are capable of more than one kind of movement.
All the different kinds of movement are possible because snakes have strong muscles, long and flexible spines and extensive rib cages with many individual rib bones. Some snake species have as many as 400 ribs! Compare that to humans. We have 24 ribs, 12 on each side of our rib cage.
Muscles are attached to their many rib bones. As these muscles contract, it allows the snake to move. These contractions help snakes slither but also swim, climb and fling themselves into the air.
Words to know
Bristly: Having a stiff and prickly texture.
Irregularity: Something that is irregular in form or nature.
Locomotion: Movement or the ability to move from one place to another.
Rectilinear: Moving in a straight line.
Serpentine: To move or lie in a winding path.
The most common form of snake movement is serpentine locomotion. This is what we generally consider to be slithering. This kind of movement is a side-to-side movement created when the snake's body forms S-shaped loops. These loops make contact with irregularities in the ground's surface, like bumps, sticks or rocks. This allows the snake to propel itself forward.
With serpentine movement, the more flat the ground is, the more energy the snake must use to move itself. All those bumps, sticks and rocks are actually helping the snake move more easily.
Sidewinding is a type of motion that allows snakes to move sideways across smooth surfaces. It does not rely on friction as much as other types of movement. With this movement, the snakes have very little contact with the surface, with just two points of contact at any given time.
Sidewinding allows snakes to move quickly, but only over surfaces without a lot of friction. Because of this, it is mostly used by snakes in desert or sandy habitats.
Rectilinear locomotion is commonly used by large snakes like boa constrictors and tunneling snakes. It, too, involves muscle contractions to create movement. These muscle contractions are more like scooting forward in a straight line little by little than slithering.
Concertina movement is similar to rectilinear location, but the S shape is still part of the movement pattern. With this movement, the snake doesn't move in a straight line. A snake will stretch out the front of its body. Then, to move up the rear section, it will bunch its body into an S shape. It continues this pattern to create movement.
Snakes aren't the only legless animals on land. There are also legless lizards, including one right here in Will County. The slender glass lizard looks much like a snake. However, it is classified as a lizard because it has movable eyelids and external ear openings, two things snakes do not have. Legless lizards move like serpentine snakes, slithering using an S-shaped movement.
One more legless creature that might come to mind is the earthworm. They don't slither like snakes, but their movement is somewhat similar to rectilinear locomotion that some snakes use. They extend the front of their body forward then contract to pull their rear part forward. Worms have short, bristly hair called setae on their bodies that point toward their rear, and these hairs help them grip the earth as they move forward. This gripping movement helps prevent them from slipping backward as their rear is pulled forward.
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