Snakes don't need planes to take off.
Video footage and a new mathematical model explain how five snake species achieve gliding flight.
The snakes stay in the air for up to 79 feet because the upward component of the aerodynamic force is greater than the snake's weight.
Future studies on the snakes and other animal gliders could lead to more energy-efficient flying vehicles.
The worst nightmare of ophidiophobes, people with a phobia of snakes, may have just been realized. Scientists have captured footage of "flying" snakes, explaining how five related snake species stay airborne for up to 79 feet.
The acrobatic arboreal snakes, all in the genus Chrysopelea, use what's known as gliding flight to sail from tree to tree in their Southeast and South Asia habitats.
The new research, presented today at the American Physical Society Division of Fluid Dynamics meeting in Long Beach, explains how the snakes accomplish their seemingly improbable feat.
"The snake isn't defying gravity or doing something out of the blue," project leader Jake Socha told Discovery News. "It's the magnitude of the forces that are somewhat surprising. Given that this is a snake, and its cross-sectional body shape is more like a blunt shape than a typical streamlined wing, we wouldn't have expected such good aerodynamic performance."
Socha, a Virginia Tech biologist, and his team launched the flying snakes from an over 49 foot tower and recorded the snakes' every move to the finest detail.
The scientists, whose work has been accepted for publication in the journal Bioinspiration & Biomimetics, next developed a mathematical model to explain how the snakes use gliding flight to travel over such long distances.
"The snake creates lift using a combination of its flattened cross-sectional shape and the angle that it takes to the oncoming airflow, known as the angle of attack," Socha explained.
To take off from a tree branch, for example, these snakes will drop the front of their bodies to create a "J"-shaped loop before jumping and accelerating upwards. That motion hurls the snake into the air.
The researchers determined that the airborne snakes never reach an "equilibrium gliding" state, when the forces generated by the snakes' undulating bodies exactly counteract the force pulling the animals down. The snakes did not just immediately fall to the ground either.
Instead, "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.
"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," he added. "But our modeling suggests that the effect is only temporary, and eventually the snake hits the ground to end the glide."and
The new model additionally helps to explain the gliding technique of many other species, including certain mammals, frogs, lizards, snakes, ants, fish and squid.
In the future, the research might lead to improved micro-air vehicles, small unmanned and often autonomous flying machines that could duplicate the energy-efficient gliding flight method of the animals.
Greg Byrnes, a postdoctoral fellow in the University of Cincinnati's Department of Biological Sciences, told Discovery News that the study is "likely the most conclusive to date piece of evidence against the long-held idea that animal gliders act much like paper airplanes -- accelerating to an equilibrium and gliding steadily. And (it) confirms some of our work with gliding mammals."
"It's really remarkable that an animal that, at first glance, possesses a body plan that seems so ill-suited to gliding can not only support its body weight with aerodynamic forces, but actually create a surplus of these forces," Byrnes added.
Socha likens a snake to a rope, "and that's a pretty bad starting place to be if you want to design a glider," he said. "Evolution discovers some pretty unusual ways of doing things."