Snakeskin Reveals Secrets Behind a Sidewinder’s Twisted Wiggle

Serpent bellies seem smooth, but on a microscopic level, their species-specific scale structures may show how they adapted to their environments

A sidewinder snake lays coiled up in the sand
Sidewinder snakes most likely phased out the spikes along their bellies in favor of a smoother belly that can move with no frictional drag. Rob Felt, Georgia Tech

Sidewinder snakes are venomous predators famously known for their smooth and mesmerizing gait that shifts them across the sandy deserts of North America, the Middle East and Africa. Like the name suggests, sidewinder snakes slither to the side, leading with their bodies, unlike other species of snakes that wiggle forward and lead with their heads.

After looking at sidewinder snakeskin under the microscope, Jennifer Rieser and her team from Emory University in Atlanta found that the snakes' bellies are riddled with microscopic holes and may be the reason they can move across slippery sand with ease, reports Deborah Devis for Cosmos. The study was published this week in Proceedings of the National Academy of Science.

The researchers collected naturally shed snakeskin from three sidewinding snakes: the sidewinder rattlesnake (Crotalus cerastes), native to the U.S. and Mexico, and two North African snakes, the Saharan horned viper (Cerastes cerastes) and the Saharan sand viper (Cerastes vipera). Researchers compared the collected skins to the Mexican lance-headed rattlesnake (Crotalus polystictus), reports Cosmos.

When the various snakeskins were viewed under an atomic force microscope, the researchers observed that the Mexican lance-headed rattlesnake, a snake that moves in a forward slithering motion, had belly scales in the shape of spikes. In contrast, the Saharan sand viper had only tiny uniform pits across its belly, reports Cosmos. To see how the varying belly scales performed under different surfaces of friction, the researcher’s created a mathematical model, reports Asher Elbein for the New York Times.

A micrograph of the smooth, round pits found on sidewinder snakes belly scales that may aid them in movement across slippery sand. Tai-De Li
The Mexican lance-headed rattlesnake (Crotalus polystictus), a snake that moves in a forward slithering motion, had belly scales in the shape of spikes. Tai-De Li

Spikes cause more directional friction against the ground and allow the snakes to push themselves forward, reports the New York Times. On the other hand, sidewinder snakes most likely phased out the spikes in favor of a smoother, frictionless belly that can move in any direction with no frictional drag.

Sidewinders move by simultaneously keeping two parts of their body on the ground while their head thrusts forward, allowing them to skip across sands at a quick 18 miles per hour. Unlike slithering snakes, the sidewinder does not need to push forward to begin moving since they launch themselves upwards, reports Cosmos. If sidewinders had spiky scales, they would not be able to move in a sideways motion and would experience more friction against the sand.

When looking at snakeskin from the sidewinder rattlesnake, the researchers found that it has small holes along its belly scales like their distantly related African counterpart—but also a few spikes. The researchers suggest that this is evidence of desert dwelling sidewinders adapting the smooth bellies for their environment because American deserts are only 15,000 to 20,000 years old while African deserts are between seven to ten million years old, reports the New York Times.

“That may explain why the sidewinder rattlesnake still a few micro spikes have left on its belly, it has not had as much time to evolve specialized locomotion for a sandy environment as the two African species that have already lost all of their spikes,” says Rieser to Cosmos.