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When snakes fly

A gliding snake gets some lift by spreading its ribs

SNAKES IN THE AIR  A paradise flying snake can leap from a tree and, with lots of wriggling, glide for meters, landing unharmed on the ground or in another tree.

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A snake jumping out a window looks nothing like a paper airplane.

Few snakes do anything but fall, but the paradise flying snake widens and flattens its body as if trying to catch some lift. And instead of holding a straight Superman pose, it undulates and whips S-curves in the air in a 3-D motion people don’t have a word for. “Just watch the video,” says biomechanist Jake Socha of Virginia Tech in Blacksburg.

Launching from a 10-meter height, Chrysopelea paradisi can glide outward 10 meters, and Socha has witnessed a champion glide of 21 meters. It’s the most accomplished aerialist of the five Chrysopelea gliding snake species, all from Southern and Southeast Asia.

The paradise glider lives in trees, climbing in easy slithers and jumping off branches to escape predators, and scientists. It really does jump, Socha says. The snake anchors its tail on a branch, and the front of the body first drops down and then shoots back up and out headfirst. It has some power to aim its glides, and Socha suspects it has unusually good vision for a snake. When he worked near Chicago, his gliders would snap heads-up alert and follow the motion of an airplane across the sky.

Yet a resting paradise glider looped over a branch “just looks like a normal snake,” he says. “That’s part of the fascination.”

Most of the time the paradise glider is as sausage-round as any other snake. But during a glide, the flyer splays out its ribs and sucks in its belly. Its round cross section turns into more of a dome, like a sliced mushroom cap — an odd shape for an airfoil.

Socha and his colleagues used 3-D printing to create a snake stand-in with the same cross section and tested fluid flowing around it at various speeds and angles. Contrary to intuition, at many angles the chubby shape could generate much of the lift a gliding snake needs, the team reports in the Feb. 1 Journal of Experimental Biology.

But the domed shape doesn’t account for all the lift the snake actually achieves. Socha is now studying the contributions of its aerial motions. A bicycle racer can catch a boost by drafting behind another racer, so Socha wonders if a long snake whipping its curves might basically be drafting itself.

SAFE LANDING  A paradise flying snake can jump out of a window and glide safely to the ground. The snake accomplishes the feat, at least in part, because it changes the shape of its body to generate lift.

Credit: J. Socha
