Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

Up in the air (Image: Jake Socha)

Species: Chrysopelea paradisi

Habitat: tropical rainforests of South Asia, gliding up to 100 metres from the tops of trees

Why crawl when you can fly? While their relatives slither on the ground, a few snakes take to the air, gliding from tree to tree. The most skilled of them all is the paradise tree snake, and we may finally have worked out why. It gets an aerodynamic lift by shifting its body into an unconventional, yet strangely familiar, form.

There are five species of flying snake, all native to south-east Asia. The five are reasonably average in the looks department – at least, until they begin to move. These snakes slither up trees before launching themselves from branches high in the canopy, undulating their bodies from side to side as they glide elegantly – at speeds of about 10 metres per second – to their destination.


Most studies into the snakes’ gliding skills have focused on these wave-like body undulations, but Jake Socha of Virginia Tech in Blacksburg and his colleagues decided to focus on another factor.

Shape-shifter

It is clear that, once airborne, the snakes flatten their cylindrical bodies by splaying out their ribs. Slice a snake open, and the cross-sectional shape the body makes is reminiscent of a UFO from the classic Space Invaders arcade game. It’s not a shape conventionally regarded as aerodynamic – but the biologists decided to investigate its properties anyway.

Video: Flying snake gets lift from UFO cross section

Socha’s team recreated a 2D model of a mid-body snake slice, and then placed it in a tank filled with flowing water – a technique that allowed them to model how air would flow around it. It was much more aerodynamic than Socha expected, producing forces that, in air, would allow it to maintain near-maximum lift. “The forces are what allow it to move forward in the air and not fall down,” he says.

In fact, the UFO shape outperformed more conventional aerofoil designs, like those used to construct the aircraft wings.

Scale is everything

Does that imply the aircraft industry could improve its designs? Probably not, says Socha. The trouble is, the UFO design works better than our conventional designs only for small objects gliding relatively slowly. An object about the size of a snake, in fact. Scale the design up to the size and speed of a jumbo jet, and the airflow no longer provides good lift. “If you tried to scale it up to make the wing of a passenger plane, it would be a terrible idea,” says Socha.

The snakes’ unusual cross-section will be a factor in their gliding ability that works with the body undulations, says Socha. His team’s model suggests that the amount of lift the UFO shape provides varies depending on its orientation in the air, so the body movements may help the snake to carefully control the amount of lift while airborne.

The tip of the snake’s tail, meanwhile, does not flatten out during flight and might be acting as a rudder. “One of the snakes I worked with had a naturally paralysed tail, it could glide well but it could never turn,” Socha notes.

Together, these factors come together to produce a surprisingly effective little glider. Based on glide performance, Socha says their aerodynamics are pretty similar to flying squirrels.

Not bad for an animal with no limbs.

See more animals aloft in our gallery: “Animal aviators: Unusual creatures take to the skies“

Journal reference: Journal of Experimental Biology DOI: 10.1242/jeb.090902