When it comes to gliding, most snakes do so the same way: straight ahead. But for the snakes that live in deserts, wandering around them can be a challenge.
“As we know from trying to move on sand in the beach or elsewhere, it can be difficult to move on these materials that are produced under you as you advance forward,” said Jennifer Reiser, a professor of physics at Emory University in Atlanta.
That is why sideways slips. Dr. Riser said that although some snakes can move sideways under certain conditions, side snakes – the common name for a group of three closely related snakes found in the deserts of Africa, the Middle East, and North America – have elicited this unique form of movement. To art. The perverted rattlesnake, for example, can travel at 18 miles per hour, making it the fastest snake in the world.
Now a new study by Dr. Razer and her colleagues has found their secret: scales filled with small pits, rather than the tiny nails at the bottom of other snakes. Their research was published Monday in the Proceedings of the National Academy of Sciences.
Dr. Reiser said the microstructure of snakes’ stomachs is important in how they move, because that’s how the animals interact without limbs with the Earth. To examine the microstructure of the lateral scales, her team used an atomic force microscope to scan the skins of naturally falling snakes, which have been provided by institutions such as the Atlanta Zoo. Then they built mathematical models to test how the structures they saw performed under different types of friction.
Although they appear soft to the naked eye, most snakes have microscopic spines directed from head to tail. Dr. Reiser said these create friction between the snake’s body and the ground, helping them to proceed with a familiar head slip.
Snakes from a variety of habitats and environmental roles – including close relatives of the lateral rattlesnake, such as the cotton or back rattlesnakes – have these spikes prominent on their stomachs.
But the skewed species either reduced or eliminated these spikes, and replaced them with perforated belly scales with microscopic pits that can move in any particular direction. That’s because directional friction makes movement in a friction-free environment more difficult, Dr. Reiser suggests: “Imagine a snake trying to move on linoleum or silk.”
Deflection relies instead on lifting large parts of the body in the air as the animal moves. Dr. Reiser said scales that create strong directional friction perform very poorly with this type of movement. But if the gauge’s friction is uniform in all directions, it makes deflection much easier.
The desert-horned snake and the Namib Desert side fodder – which are closely related – have a belly scales with uniform pits and without corrugation. But the perverted rattlesnake, which comes from a different branch of the snake family tree, still has a few burrs in the abdomen in addition to pits.
One possible explanation for this difference is that the deserts in southwestern North America are only 15,000 to 20,000 years old, compared to the North African desert, which is between seven and 10 million years old.
“There was probably less time for American soldiers to develop structures that might aid this type of movement,” said Dr. Reiser.
While the team’s hypothesis about the precise function of microscopic drilling will require additional study, the loss or reduction of these abdominal elevations in the lateral related distal curves suggests that these changes are a direct adaptation of lateral movement, they suggest.
“Since this movement is so necessary for survival, it is reasonable to think that this is part of the reason why this change is taking place,” said Dr. Reiser.