Aerial undulation helps paradise tree snakes glide through the air.  

Scientists have gained some insight into how snakes fly. Yes, snakes fly—well, sort of.

Researchers at Virginia Tech just published a paper in Nature Physics revealing a new understanding of how the paradise tree snake (Chrysopelea paradise) launches itself through the air, appearing to fly.

The process by which these snakes launch themselves from one high flying tree limb to another is called aerial undulation. In this process, the snake’s body will ripple with waves. The Chrysopelea family is the only known limbless vertebrate that is capable of flight. Scientists have long wondered how the process happens and have never been able to entirely understand it. 

The team at Virginia Tech developed the first-of-its-kind continuous, anatomically-accurate 3D mathematical model of the paradise tree snake in flight. Led by Jake Socha, a professor in Biomedical Engineering and Mechanics, the team also included Shane Ross, a professor of Aerospace and Ocean Engineering, and Isaac Yeaton, lead author and recent doctoral graduate in mechanical engineering.

Socha has worked for over two decades to understand the biomechanics of snake flight and what function undulation serves. He wanted to find out if the snakes used undulation intentionally as a way to maintain stability while gliding through the air. 

After observing, photographing, and analyzing 131 live snake glides, the team developed the 3D model. They used a four-story black box theater, The Cube, located at the Virginia Tech Moss Arts Center, to capture the motion of the snakes as they jumped. Infrared light was used to capture points on the snakes' bodies as they moved. The information was measured and digitized, then used to create the 3D model that reproduced the motion. 

Paradise tree snakes first step of the jump is to curve its body into a J-shape, then spring up and out. As the snake launches, it changes its shape, flattening its body everywhere except for the tail. The body becomes a sort of “morphing wing” that produces lift and drag forces when air flows over it, as the snake’s body accelerates downward. Through the model, the team learned that aerial undulation keeps the snake from tipping over and increases the distances the snake can travel. 

The study also revealed that snakes use two waves when undulating. A "large-amplitude horizontal wave and a newly discovered, smaller-amplitude vertical wave. The waves went side to side and up and down at the same time, and the data showed that the vertical wave went at twice the rate of the horizontal one." Double waves like this have only been seen with one other snake, the sidewinder.

"This is really, really freaky," said Socha of the discovery. 

The team is excited to using that information in new technologies, including robotic snakes, that could be used to help in search-and-rescue operations and disaster monitoring. 

“Studies like this one not only provide insight into how nature works, but lay the groundwork for design inspired by nature. Evolution is the ultimate creative tinkerer, and we’re excited to continue to discover nature’s solutions to problems like this one, extracting flight from a wiggling cylinder,” Socha said on the Virginia Tech website. 

Paradise tree snakes are not native to the United States and they are not known to be harmful to humans.

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