To escape danger, some small snakes no longer crawl: they roll and race away at more than 13 km/h.
The spectacle is surprising. The animal bends its body, lifts part of itself and launches into a succession of rolls. This behavior has already been observed in small snakes from Southeast Asia, but researchers did not really know how they managed to move so quickly without losing control.
A specimen of Pseudorabdion longiceps photographed in Bang Lang National Park, Thailand.
Photo or document: Rushen / Thai National Parks, CC BY-SA 2.0. Source information.
Japanese researchers filmed snakes of the genus Pseudorabdion from several angles. They then studied their movements frame by frame to understand how their bodies fold, turn and regain contact with the ground.
The measured speed is impressive for such a small animal. During the rolls, some snakes briefly reached 3.69 meters per second, or just over 13 km/h. That is about four times their maximum speed when moving by normal undulation.
Yet their bodies do not rotate perfectly regularly, like a bicycle wheel. They alternately bend and straighten. One part makes contact with the ground and pushes the animal forward, then another takes over. This succession of movements allows them to chain together their rolls.
Kinematics of rolling locomotion.
The most astonishing detail concerns the head. While the rest of the body rotates rapidly, it remains relatively stable. The researchers believe that this separation of movements helps the snake maintain its orientation and avoid losing control of its trajectory.
And it seems to work. During the experiments, the snakes were able to follow a corridor only 20 centimeters wide. They were therefore not simply rolling randomly, even at a speed unusual for their size.
This technique could be useful for quickly escaping a predator. But the study does not prove that it is always more effective than the usual escape method in every environment. Above all, it explains how a legless animal can adopt such a different way of moving.
This discovery shows that snakes are not limited to crawling or swimming. By using the flexibility of their bodies and the stability of their heads, some have developed a genuine acrobatic escape technique.