Snakes: Do The Locomotion (Part 2)

How do snakes get from place to place without limbs? In Part 1, we learned about the five modes of terrestrial locomotion: lateral undulation, slide-pushing, concertina, rectilinear, and sidewinding. Today, we'll take a look at other modes of locomotion.

Snakes in Water

Swimming resembles terrestrial lateral undulation. There are a few differences, however. Every part of the snake's body exerts force on the water. The entire of the surface of the snake creates drag. Also, instead of horizontal waves that decrease in amplitude, aquatic snakes move in horizontal waves that increase in amplitude.

Many aquatic snakes have modifications that increase their surface area laterally. Some have loose skin and others have flattened tails. In addition, some sea snakes have lungs that extend 84 to 100 percent of the trunk length. This provides buoyancy and keeps the back end of the snake's body from sinking.

Digging Holes

Many scientists believe that fossoriality has favored the evolution of limb reduction, leading to the origin of many limbless animals such as snakes. This theory has not been proven, but limblessness often correlates with fossorial habits.

Many burrowing snakes have pointed reinforced skulls that help in moving through the substrate. These snakes often use the concertina mode of locomotion to make burrows. Rough scales provide additional friction against the soil or sand.

Sand-swimming snakes, which spend extended periods of time moving beneath the desert surface, have very smooth scales. Breathing under sand is very different than breathing under soil. Most snakes exhale by using muscles to compress their ribs, decreasing their diameter. But loose sand would immediately collapse around the snake, making inhalation nearly impossible. Sand-swimmers have adapted by raising and lowering their ventral surface when breathing, preventing the collapse of loose sand.

Getting off the Ground

Saltation, abrupt movement or transition, is the snake form of "hopping" or "jumping". (I use quotations here because, technically, both hopping and jumping require limbs). A rapid extension of the snake's body from front to back lifts it off of the ground. This requires a lot of energy and is limited generally to very small snakes.

Flying Snakes! (No, They Aren't on a Plane)

Unfortunately for all you ophidiophobes (ophidiophobia is the fear of snakes), flying snakes do exist. The term may be a bit misleading, however. "Flying snake" is the common name for snakes of the genus Chrysopelea. But these snakes don't fly - they glide. (So, I suppose there is still a possibility of a snake landing on you out of nowhere.)

The angle of descent of gliding animals ranges between 0 and 45 degrees. Animals that fall at an angle greater than 45 degrees are said to be parachuting. The descent of Chrysopelea can be as shallow as 30 degrees.

The snake hangs at the end of a branch from its tail in the shape of the letter "J". After choosing a landing site, it throws itself forward and up out of the tree. The snake then stabilizes and directs the descent by spreading its ribs widely (this results in a concave ventral surface - resembling the cross-section of a Frisbee) and making the motion of lateral undulation.

For more information on flying snakes, including pictures and videos, please go to Jake Socha's web page here.

Next Time

In Part 1, I mentioned snake anatomy briefly. Next time, I will continue this discussion.

Thanks for reading!

Other Blog Entries

New Animal Attractions
Reptiles: A Scaly Introduction
Snakes: They're All Around
Snakes: A Family Affair (Part 1)
Snakes: A Family Affair (Part 2)
Snakes: Clever And Deadly Behaviors
Snakes: Do The Locomotion (Part 1)