Some snakes don't need to be on a plane to take flight. The "flying" snake (or paradise tree snake, Chrysopelea paradisi) launches its sleek frame into the ether from precipitously tall trees in Asia and sails downward.
This seemingly strange behavior—particularly for an animal that has no limbs or skin flaps itself—has been long known, if not well described. But it has been a slippery puzzle for physicists, who have struggled to analyze the snakes' take-off and flight patterns.
New analysis of these sailing serpents helps to explain their curious trajectories.
Letting snakes leap from a 15-meter tower, Jake Socha, an assistant professor of engineering science and mechanics at Virginia Tech, and colleagues filmed a sampling of snakes (60 to 74 centimeters long) with four video cameras.
Rather than a smooth, even glide (known as equilibrium gliding, as executed by airborne birds), these snakes seemed to slither frenetically through the air. But all of their thrashing worked to reduce their fall speed (from about six meters per second to four meters per second) and gliding angle (from 32-48 degrees to 18-32 degrees).
"The snake is pushed upward—even though it is moving downward—because the upward component of the aerodynamic force is greater than the snake's weight," Socha said in a prepared statement. The new research suggests that the snakes' soaring might be due to specifically tuned undulations which could create vortex-induced lift, Socha and his colleagues noted in a study, to be published November 24 in Bioinspiration & Biomimetics. The research was also presented Monday at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, Calif.
"Hypothetically, this means that if the snake continued on like this, it would eventually be moving upward in the air—quite an impressive feat for a snake," Socha said. Models show, however, that the unexpected upthrust is only passing—at least in the experimental setting, in which "the snake hits the ground." But in the snakes' native forest habitat, where trees are much higher and distances longer, the oscillating ophidians might remain airborne much longer.
But those with a fear of flying snakes needn't worry unless their travel plans will take them into a South Asian forest—or reruns of the 2006 film starring Samuel L. Jackson.
Watch a gliding snake in flight:
Image courtesy of Jake Socha; video courtesy of Jake Socha/National Geographic Television