Flying Snakes Need to Wriggle Through the Air to Glide
The paradise tree snake flattens its body and swerves in three dimensions to glide through the canopy
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Snakes are well known for their sneaky slithering, but five species are prone to literal flights of fancy. Flying snakes, like the paradise tree snake, get around by launching themselves from treetops and gliding to branches dozens of feet away. While aloft, they wriggle and twist in a sidewinder-like squiggle that begs the question: is that really necessary?
It turns out that yes, it is, according to new research published on June 29 in the journal Nature Physics. Using high-speed photography and a computer model of snakes in flight, researchers at Virginia Tech found that if the snakes didn’t wiggle, they wouldn’t be stable in the air. It takes a combination of side-to-side and vertical motions, along with the snake flattening its body into a triangular, instead of round, shape for a snake to catch enough air to reach its destination.
Or in less scientific terms, flying snakes sort of resemble a “big, wiggly, ribbon thing,” as Virginia Tech biomechanics researcher and co-author Jake Socha describes for the New York Times' David Waldstein.
Socha has been studying flying snakes for almost 25 years. But until now, the reason for the snakes’ mid-air movements was a mystery.
"All snakes undulate when they move. And so on the ground, on a tree, in the water, they are creating these side-to-side waves," Socha tells Nell Greenfieldboyce at NPR. "It's not crazy to think that when the snake jumps into the air, the snake goes, 'Hey, I'm a snake. I undulate. That's what I should be doing.' "
To find the answer, the researchers would have to use seven snakes, infrared reflective tape, high-speed cameras and access to an enclosed, but wide open space. Socha and his colleagues recorded over 150 snake flights in a facility at Virginia Tech called the Cube, a four-story black box arena designed for student projects and arts, science and engineering experiments. The reflective tape allowed the researchers to track where the snake’s body parts were in space during each launch.
To use the Cube, the team had to convince officials that the snakes wouldn’t get hurt during their jumps or escape from the Cube, reports NPR. The space was decked out with foam flooring and fake trees—tall and short—for the snakes to travel between.
The snakes often missed their targets, however, instead landing on the padded floor or even on bystanders. Once, a snake landed on mechanical engineer Isaac Yeaton.
"I was able to put my hands out and catch it. So that was different!" Yeaton tells NPR. A snake’s flight “happens really quickly,” he says. “And it's hard to see all the detail by eye. So that's why we need high speed cameras and high-speed motion capture."
But the team used the data gathered by the high-speed recordings of the reflectively-marked snakes to create 3-D computer models of snakes in flight. It turns out that the snakes’ waves have surprising proportionality—the vertical waves have double the frequency of horizontal waves, “indicating that the body has twice as many vertical bends as lateral bends,” the researchers write in the paper. The snake’s tail also moved up and down for increased stability.
“Other animals undulate for propulsion,” Yeaton tells the New York Times. “We show that flying snakes undulate for stability.”
Georgia Tech physicist Jennifer Rieser, who studies snake slithering, but was not involved in this new study, tells NPR that the research is a “cool” finding. The paper provides evidence that the way the snake moves in the air "actually seems to have a pretty important consequence for their movement,” she says.
Docha tells the New York Times that these insights could help with the creation of snake-inspired robotics. A snakelike shape, ideal for getting through small spaces, could help with search and rescue operations.
“I wouldn’t say all the mysteries are solved,” says Socha to the New York Times, “but we have a big piece of the story filled in.”