February 12, 2010

FeatureScientists Find Friction is Key to Snake Movement

Researchers studying the mechanics of snake movement have discovered that snakes move with the help of friction at the microscopic level. Scientists previously thought that snakes moved by pushing their bodies against objects, David Hu and his colleagues confirmed this idea, but determined that the movement occurs with the help of the snake’s belly scales.

Belly scales are key to a snake's movement. (Photo credit: imagebroker/Alamy)

The scientists studied several individual Pueblan milk snakes. In one experiment, the scientists anesthetized the snakes and measured the force required to move the snake’s body over a surface in a variety of directions. The researchers determined it was easier to move the snake’s body forward than it was to move the snake’s body sideways. They also found it was more difficult to slide the snake’s body backward than it was to move the snake forward. In completing this experiment, the scientists found that the orientation of the snake’s belly scales dictated how well the snake’s body moved over a surface. As the snake moves, its scales get caught on the surface of the ground, creating a frictional force the snake uses to move its body forward.

In another experiment, the scientists placed a snake on a clear surface covered with “photoelastic” gelatin. The scientists then shined a light beneath the surface. Bright regions on the gelatin surface indicated where the snake was applying the largest amount of force. If you have ever watched a snake move, you may have noticed that its body does not touch the ground in all places—instead the curved parts of its body are lifted away from the surface of the ground. The researchers determined that the snakes lift certain portions of their body as they move, putting more pressure where their body touches the ground, helping them to propel their bodies forward.

In a third experiment, the researchers tested the snake’s ability to move when placed in a cloth “straightjacket.” Without the ability to grip the ground surface with their scales, the snakes were unable to move. The scientists also found that the snakes were unable to move when placed on a super-smooth surface, as their belly scales were unable to create the friction necessary for movement.

Understanding how snakes move may have implications in several fields of science. (Photo credit: Ben Molyneux/Alamy)

So what’s the point of these experiments? The scientists point to a number of robotic applications where these results can be used. For example, understanding how snakes move may aid in the development of a frictionless robot that could be used in human surgery. A second use may be in the development of a robot used for search and rescue operations following earthquakes, where a slim, snake-shaped machine would be useful.

Scientists who contributed to this research include David Hu, Jasmine Nirody, Terri Scott, and Michael J. Shelley. The results of their research was published in the June 2009 edition of The Proceedings of the National Academy of Sciences.

More to Explore

• The mechanics of slithering locomotion [abstract]
• Snakes Use Friction And Redistribution Of Their Weight To Slither On Flat Terrain
• PHOTOS: Snakes on Gel, in Jackets Illuminate Slithering

Last updated February 12, 2010 | Comments (5) | Permalink | Feature