Physics: Undulation stabilizes flying snakes

Undulation stabilizes and propels flying snakes as they glide through the air, according to a modelling paper published in Nature Physics.

Many animals undulate in order to move themselves forward in water, on rough surfaces or on sand. Flying snakes (Chrysopelea), the only known limbless vertebrates capable of flight, use undulation when they glide through air. During this process, the shape of the snake’s body changes continuously as horizontal and vertical waves move through it.

Isaac Yeaton and colleagues analysed how undulation affects the motion of flying snakes by tracking their glides with high-speed cameras. They identified the presence of a vertical wave during gliding behaviour through air, suggesting that flying snakes use undulation for more than just horizontal movements in the air. The authors then built a computational model that simulated snake flight with and without undulation. Without undulation, the anatomically correct modelled snakes pitched and rolled in the air and glided a short distance. However, when undulation was included, a majority of the simulations showed stable glides, indicating that undulation in snakes may enhance stability. This contrasts with other animals that use undulation to only propel themselves.

The authors suggest these findings could be aid the design of bioinspired flying robots that can glide using aerial undulation.