New research explains how a bizarre species of snake scientifically called Chrysopelea paradisi can glide as much as 30 meters from trees.
The Paradise flying snake, Chrysopelea paradisi. Image credit: © Jake Socha.
Chrysopelea paradisi is commonly known as the Paradise tree snake or Paradise flying snake. The reptile can be found in countries of Southeast Asia such as Singapore, Thailand, Indonesia, Malaysia, Myanmar and the Philippines.
Paradise flying snakes are mildly venomous and well known for their aerodynamic gliding through the air from tree to tree.
The new study, reported in the Journal of Experimental Biology, shows how these snakes generate the lift they require to remain airborne.
“The snakes flex their ribs as they launch to stretch and flatten the body to change their profile from a circle into an arched semi-circle. It looks like someone’s version of a UFO,” said study co-author Dr Jake Socha of Virginia Tech.
To get to grips with the aerodynamic forces generated by the Paradise flying snake‘s body, Dr Socha and his co-authors created a rod with the same cross-section as the reptile’s body and placed it across a tank filled with water that flowed over the snake-shaped bar.
Tilting the snake model at angles of attack ranging from minus 10 to 60 degrees as the water flowed over it at speeds ranging from 20 to 50 cm/s, the scientists measured the lift and drag forces pulling on the model and saw that at most angles the reptile’s unusual body shape generated sufficient lift to account for some of the snake’s impressive gliding performance.
But when they tilted the model at 35 degrees, there was a massive spike in the lift generated by water flowing at higher speeds.
More surprisingly, when the model was held level with the flow, instead of generating upward lift, the fluid pushed the rod down.
And when the team visualized the turbulent water flowing around the model with microscopic reflective beads, they could clearly see a spinning vortex sitting beneath the untilted snake shape, sucking it down.
“Maybe the snake does hold part of its body flat at some point, using it as a mechanism for control, explaining that twisting the body while airborne could allow the snakes to fine tune the forces on their bodies for precise flight control,” Dr Socha said.
“There is much more to the snake’s impressive glide than just its unusual body shape,” he added.
“If you make a rough estimate of the lift to drag ratio for the real animal, it appears to do better than what we got from this study.”
Dr Socha noted: “so even though this shape produced more lift than we were expecting, it doesn’t get us the glide performance that snakes can attain, giving us a hint that there is something in what the animal is doing aerodynamically that is not captured by the cross-sectional shape alone.”
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Daniel Holden et al. 2014. Aerodynamics of the flying snake Chrysopelea paradisi: how a bluff body cross-sectional shape contributes to gliding performance. J Exp Biol, 217, pp. 382-394; doi: 10.1242/jeb.090902
