The sidewinder's sideways trick on loose sand

Engineers who build snake-shaped robots hit a wall: on loose, tilted sand their machines slipped and pitched. The animal they were copying did not. In a 2014 paper in Science, Hamidreza Marvi and colleagues reported that sidewinder rattlesnakes (Crotalus cerastes) move well on inclined sand, and that a robot given the snake’s trick could climb slopes close to the steepest angle the sand can hold.

The trick is how a sidewinder moves: sideways, with only parts of its body touching the ground at any moment. This article explains how that gait works, why loose sand is such a tricky surface, what the snake changes when the slope gets steeper, and what researchers found when they took it off sand altogether. We also meet the animal itself, a small, horned rattlesnake that spends most of its life in burrows. Where two descriptions of the gait differ, we say so. The sidewinder is venomous. This article is not a guide to handling it, and the right way to meet one is from a distance.

Meet the sidewinder

The Animal Diversity Web (ADW), a University of Michigan database, places the sidewinder in warm desert in the southwestern United States, from the Mojave Desert in southern California to the Sonoran Desert in Arizona, plus parts of Baja California and the northern Gulf of California. It uses sandy washes, dunes and open desert, and it concentrates near mammal burrows. The Reptile Database adds southern Nevada and southwestern Utah to the U.S. range. According to ADW, lizards make up over half of the diet and mammals over 40%, with some birds. A sidewinder tracks prey with heat-sensing pits, chemical detection and touch, with sight a lesser sense, a toolkit we explain in our article on the Western diamondback rattlesnake.

Why loose sand is a hard place to travel

Sand looks simple and acts strange. A 2023 paper in Biology Open notes that sand shifts under an animal and behaves partly like a solid and partly like a fluid. Push on it and it gives way. On a slope it gives way more easily. Marvi’s team ran plate-drag experiments and found that sand’s yield stress, which is how much force a pile of grains can take before it gives way, decreases as the incline gets steeper.

Why does the sidewinder’s gait suit this ground? Tingle and colleagues say the gait has a close association with sandy deserts, probably because it lets snakes avoid slipping on granular material like sand. That is their hypothesis, not a measurement of slip. ADW offers a second possible benefit: the gait reduces contact with hot sand. Both ideas can be true, and our sources do not rank them.

How the gait works

In the 2022 paper in the Journal of Experimental Biology, Tingle and colleagues describe sidewinding as a traveling wave with a horizontal part and a vertical part. At any moment some sections of the body stay in static contact with the ground, meaning they are planted and not sliding, while other sections are lifted forward and set down in new contact patches. The snake ends up moving at an angle to the line of its body. It is a snake that is mostly standing still, one patch at a time, while the rest of it goes somewhere.

You will often read that sidewinding is two waves. A Science News report on Marvi’s study says the researchers reduced the gait to a template of two wave-like motions, slightly out of phase, one vertical and one side to side. Tingle’s papers describe a single wave with both parts. These are two ways of describing the same movement, and the sources do not say one is wrong.

How fast is it? Tingle’s team put sidewinders from the Goldwater Range near Yuma, Arizona, in a sandbox about 1.15 meters square, filled with sand 2 centimeters deep, and filmed them at 500 frames per second. Among the 26 snakes they analyzed, mean speeds ranged from 0.07 to 0.61 meters per second, about 1.4 miles per hour at the top. The snakes were prompted only enough to sidewind, so these are routine speeds, not records. Bigger snakes were not faster. How often the wave repeated, its frequency, explained about 83% of the variation in mean speed in the authors’ model.

What changes on a slope

On a steeper slope, a sidewinder does not dig in harder. Science News reports that the snakes increase the share of their body touching the sand in each wriggle, which lowers the risk of slipping. Marvi’s team put the same finding in numbers: snakes increase the length of body in contact with the sand as the incline grows. In Science News’ account, contact reached nearly half the body length at about 20 degrees.

The team tested the snakes at Zoo Atlanta, on a sand slope built in a shed with sand brought from Arizona. Science News says the sidewinder outclimbed 13 other kinds of pit vipers and a robot snake. Twelve of those 13 species failed on inclines of even 10 degrees. A robot given the contact-length rule climbed slopes close to the angle of maximum stability, according to the abstract. That is a lab and robot result, and it says what the snake does, not why the snake evolved it.

What this looks like in practice

The most surprising test removed the sand. Tingle and colleagues filmed 8 sidewinders on vinyl flooring and compared them with 26 sand trials from their earlier study. Four snakes were tested on both surfaces. Only two of ten measured variables differed.

The longer wavelength on vinyl held up in the four snakes tested on both surfaces. The difference in height lifted did not hold up in that small paired test. The authors call the groups unbalanced, say they did not measure slip, forces or energy, and suggest, as speculation, that the animal’s body shape may help it keep similar movements on very different floors.

Common mistakes and myths about sidewinding

Mix-up: the snake slides sideways like a skater. The sources describe planted sections and lifted sections, not a skid.

Mix-up: it is a sand-only trick. The vinyl experiment shows the same sideways gait on a smooth floor, with small changes in shape.

Mix-up: sidewinding is the only way it moves. ADW says it also uses rectilinear movement, where the body moves in a straight line, and lateral undulation, the familiar S-shaped slither.

Mix-up: a sidewinder is a young diamondback. ADW gives an adult sidewinder an average length of about 50 centimeters from snout to vent. It also lists horn-like scales above the eyes. The Western diamondback rattlesnake is a different species, with a body length of about 1.5 meters.

Mix-up: desert animals all solve the same problems. The sidewinder solves a travel problem. The Thorny devil solves a water problem, as we explain in its own article.

Conservation status

The sidewinder is listed as Least Concern on the IUCN Red List of Threatened Species. That is the category as distributed by GBIF, the Global Biodiversity Information Facility, and we checked it on November 9, 2026. Least Concern means the species was evaluated and does not meet the criteria for a threatened or near-threatened category.

Least Concern is not the same as no problems. ADW says no specific conservation efforts are underway, and it cites an estimate that vehicle collisions kill 2,383 to 4,000 sidewinders per year. We cannot say how that estimate was gathered. ADW also notes that the species lives in protected areas, including Joshua Tree and Death Valley National Parks. We have no confirmed population trend, because none of our sources states one.

Categories are reviewed and can change, and the copy GBIF distributes can trail the IUCN website by some months, which is why we print the date we checked. GBIF’s copy does not give the year of the IUCN assessment, so we do not state one.