Tree-climbing snakes could locate control instead of stiffening their entire body
As a long, wiry scrub python makes its way from branch to branch on a tree, it can effortlessly pull itself up to climb to a higher perch. But how does he do it? Without arms or legs to support yourself, how can you not tip over? He only controls the part that matters.
Instead of expending enormous effort to stiffen their entire body in order to stand upright, tree-climbing snakes can concentrate their flexion energy and muscle activity in a small region at their baseresearchers report on February 25 in the Journal of the Royal Society interface. The team’s mathematical analysis suggests that combining such a strategy with whole-body muscular coordination could help snakes stand upright while expending as little energy as possible.
“Snakes are kind of like cords of muscle,” says bioengineer and roboticist David Hu of Georgia Tech in Atlanta, who was not involved in the study. “And they can basically perform magic tricks, flexing their body and preventing [themselves] to fall. »
In an earlier study, zoologist Bruce Jayne of the University of Cincinnati and a colleague showed that as gravity-defying snakes move upward, they activate a muscle along the spine. In the new study, Jayne and colleagues examined how snakes manage this limbless takeoff without bending under their own weight.
The team filmed four snakes – three brown tree snakes (Irregular Boiga) and a scrub python (Similar to amethyst) — crossing vertically the spaces between perches in the laboratory. The images showed that the creatures reliably contorted themselves into an S shape to do this, especially if the gap was large. The snakes were bent as far as possible near where they were perched. Above, they were almost vertical, like a tall straight pole – with little to no tilt, gravity had almost no leverage to topple them.
To understand the forces involved, the physicists mathematically modeled the creature as an active elastic filament – a flexible structure that can sense its own shape and activate muscles in response – and explored two strategies to enable the snake to stand upright. In one, each part of the body responds locally to its own curvature. In the other, muscular activity – although still concentrated downward – coordinates throughout the body to minimize the energy required to stand.
Both approaches reproduced the S shape, with most of the curvature concentrated near the perch. But the global coordination strategy required less force. And in this scenario, the bending force decreased as the snake rose into the air. Since the second approach minimizes both force and energy, the researchers suspect that even real snakes employ a similar strategy to make standing as energy efficient as possible.
The calculations also suggest that although snakes use relatively little force to strike a pose, they expend significantly more energy to remain upright. In the videos, the larger snakes sway slightly from side to side, suggesting that they are actively exercising their muscles to maintain their balance.
The results could help designing snake-like robotswhich can be used in space And underwater explorations and in investigate disaster sites. “It would be interesting to see if these ideas of control and feedback can be used to build robots that you can control more easily or use less electrical energy to give them the shapes you want,” says Ludwig Hoffmann, co-author of the study and an applied mathematician at Harvard University.
