How Snakes Move in a Straight Line

Sidewinding: Snakes bend in waves both side to side and in a vertical plane to lift the body to form just a few contact points with the ground. This helps rattlesnakes traverse hot sand or climb dunes.
Rectilinear: Specialized muscles move the belly skin of a snake, propelling it forward in a straight line. This allows snakes to slip through burrows not much bigger than they are.

A Colorado Desert sidewinder demonstrates sidewinding motion.
Credit:  Wikimedia Commons

Jayne’s snake lab in UC’s Rieveschl Hall is home to a menagerie of species from around the world, from a jumbo Burmese python that is crowd-pleaser at the professor’s public talks to incredibly skinny vine snakes with camouflage so perfect they can disappear even in their glass exhibits. He keeps the lab a toasty 80 degrees in winter.

He pulled a small python from its terrarium and cradled the animal with the casual expertise that comes from years of practice. He has been catching and studying snakes since he was a child growing up in Chicago.

“This is a baby reticulated python,” he said. “A lot of hobbyists get very wound up about partial albinos, but I like this natural color. Their cryptic coloration really breaks up their outline.”

While most biology labs study many individuals of the same species, Jayne keeps a variety of snakes for his locomotion and vision studies: carpet pythons and corn snakes and boa constrictors and even an Asian flying snake that can glide from tree to tree.

“Their belly isn’t just flat; it’s concave. They make an S-shape in mid-air and it acts as an airfoil so they can get lift,” he said. “They contort their body to steer to a particular branch.”

Credit: Joseph Fuqua II/UC Creative Services

UC biology professor Bruce Jayne holds a mildly venomous brown tree snake in his lab. These climbing snakes are notorious for decimating wild bird populations in Guam. Understanding how they climb is key to helping wildlife managers come up with better barriers to protect vulnerable species.

His lab has several brown tree snakes, a notoriously invasive species not commonly found in American herpetology collections. Brown tree snakes have decimated wild bird populations in places like the American territory of Guam, where they are believed to have stowed away on planes or cargo ships after World War II. Wildlife officials worldwide are taking extreme steps to prevent the tree snakes from invading new territory as stowaways.

“They trap them in Guam. But their numbers are so staggering that it’s just a finger in the dam,” Jayne said. “The biggest priority is to make sure they don’t get introduced anywhere else. One of the more promising preventive measures is to train dogs to sniff them out in cargo areas.”

Jayne used a snake hook to remove a 5-foot-long brown tree snake from its glass enclosure. The rear-fanged snakes are mildly venomous but pose little threat to people. The snake, which is actually olive-colored, was solid, strong and shockingly big for an arboreal animal. Jayne’s locomotion studies have found that tree snakes can reach branches as far as 90 percent the length of their bodies. And they can climb virtually anything.

“There’s a key muscle that supports the back of snakes like boa constrictors that typically spans about 14 vertebrae. But in the brown tree snake, that same muscle spans 30 vertebrae,” Jayne said. “That is advantageous for supporting their weight while crossing gaps.”

He let the snake dangle from one hand and watched as its prehensile tail wrapped around his wrist. Undeterred, the snake began to explore its vertical world, extending its body parallel to the ground to try to reach countertops.

It was easy to see how a snake so nimble and big could wreak havoc on an ecosystem that evolved without natural defenses to climbing snakes. Wildlife officials have a keen interest in understanding their abilities, Jayne said.

“Once you figure out what they can do, you can try to exploit what they can’t do,” he said.

Jayne’s lifelong interest in snakes has given science keen insights into many previously undocumented behaviors. He studied crab-eating snakes in Malaysia and is testing the acuity of snake vision in his own makeshift optical lab at UC.

“Brown tree snakes are really good at stretching out. But the funny thing is the boas and pythons are pretty darned good, too, because they’re so muscular. They use brute force while the other snakes finesse it,” Jayne said. “There are statistically significant differences in the movement of these species, but it’s a lot less than I expected.”

A vine snake has cryptic camouflage and bizarre eyes that give it peripheral and binocular vision.

Credit: Joseph Fuqua II/UC Creative Services

Jayne expertly removed a green vine snake from its enclosure. These snakes from southeast Asia have beautiful green, black and white scales in an interlocking pattern like a climbing rope and alien-looking infinity-symbol-shaped eyes that provide excellent binocular and peripheral vision.

“They’re a bit nippy. I don’t want him to give me a little kiss,” Jayne said.


“Unlike vipers that bite their prey and release it, these snakes bite and hold on,” he said. “They have really subdued but cryptic coloring. Believe me, in natural vegetation they’re hard to spot. I really love them.”

By testing the limits of its mobility, Jayne can learn more about the snake’s complex motor controls. This can shed light on how humans can execute coordinated movements.

“What allows them to go in all these different directions and deal with all of that three-dimensional complexity is they have a diversity or plasticity of neural control of the muscles,” Jayne said. “Even if the animal had the physical strength to do something, it wouldn’t necessarily have the neural control.”

Jayne wants to learn more about how this refined motor control contributes to a snake’s amazing contortions.

“They move in so many fascinating ways. Is that because they have such an incredible diversity of motor patterns that the nervous system can generate?” he said.

“Even though all snakes have the same body plan, there are fully aquatic snakes, snakes that move on flat surfaces, snakes that move in a horizontal plane, snakes that climb. They go everywhere,” he said. “And the reason they can go everywhere is they have so many different ways of controlling their muscles. That’s pretty intriguing.”