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How do these legless creatures slither, glide, crawl, and climb? Here we discuss multiple different mechanisms of snake locomotion (including flying!).
Serpentine locomotion
Snakes are known to slither. They move by pushing off of rocks, branches, and other surfaces in order to propel forward, but how do snakes travel on flat surfaces? Slithering, called serpentine locomotion, is dependent on the muscles that connect a snake’s skin, spine, and hundreds of ribs and contract to form that familiar S shape.
Snakes use friction with small bumps or uneven surfaces on the ground in order to propel forward. Their scales have hard and polished surfaces, and are layered such that their jagged edges are only exposed in one direction. This directionality means that the friction exists in a single direction, so they can use this resistance to propel forward (but not so effectively backward). For instance, a snake wearing a sock jacket can’t move as effectively as without — even though the friction on the surface of the snake is high, it is equal in all directions, so the snake just wiggles around in place.
As a snake forms an S shape, the scales running perpendicular to their direction of travel (the middle of the “S”) have more friction with the ground; this segmented resistance is key for serpentine locomotion.
Although almost all snakes can utilize serpentine locomotion, there are several other ways snakes can move. One such mechanism is “concertina” (as in “accordion”) locomotion, which resembles a sideways inchworm. Snakes anchor the front of their bodies to a surface, scrunch up the middle of their bodies, then anchor the back, release the front, push forward, and then repeat.
Rectilinear Locomotion
Rectilinear locomotion is characterized by a slow scoot forward in a straight line. Rectilinear motion depends on a wave-like flow of belly muscle contractions that pull and release the snake’s skin. It looks pretty creepy:
Discovered in 2018, rectilinear locomotion is more common in larger snakes like boas, and it is especially prevalent in tunneling snakes — which makes sense, as rectilinear locomotion takes up virtually no lateral space.
Sidewinding Locomotion
Sidewinding is another locomotive mechanism, in which snakes move sideways along smooth surfaces. Out of all locomotive mechanisms discussed so far, sidewinding depends the least on surface friction. Sidewinding involves minimal contact between the snake’s body and the ground, with only two points of contact on the ground at a time (sort of similar to walking). If we think of the snake as an S shape, the middle and top of the S are on the ground, and the two curved sections are raised. Sidewinding snakes leave behind unique J-shaped, parallel “foot”-prints reflecting their sideways movement.
It seems really counterproductive, but sidewinding allows snakes to move extremely fast without sliding — on surfaces without much friction. Sidewinding locomotion is mainly used by desert/sand snakes, such as the sidewinder rattlesnake (also called the horned rattlesnake), which can travel up to 18 miles per hour! (video)
Bonus: Flying?
Below is a beautiful example of a snake that uses rectilinear locomotion to climb up trees, and as it leaps off of branches, it widens its body and glides through the air!
Most snakes are capable of more than one type of locomotion — certain snakes might use rectilinear locomotion when relaxed, but may slither in a serpentine locomotion if trying to flee quickly.
Studying these mechanisms is not only interesting, because snakes are cool and beautiful, but it also has applications in robots and technology. Robots that use these locomotive techniques, evolved over millions of years, may have applications in medicine, nanotechnology, search-and-rescue missions, archeological digs, and much more.
* Here’s a cool example of a modular robot utilizing rectilinear locomotion; each segment of the chassis is contracting in a wave pattern. This modular robot has a rounded body and moves similar to sidewinding; it also can rotate freely and move laterally!
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