The Secret of a Snake's Slither (Image 9)
This corn snake is wearing a cloth jacket for an experiment by David Hu, a mechanical engineer at the Georgia Institute of Technology, that showed how snake scales help serpentine movement on flat surfaces.
"Snake scales are smooth in order to decrease their friction going forward but the way they're overlapping on the belly makes them actually quite rough if you rub them in the opposite direction," says Hu. And it's this roughness that's the secret to how scales propel snakes forward. "They [scales] catch in the ground when the snakes pushing to the side or when it's being slid backwards and they have a preferential direction of sliding forwards," adds Hu.
This fundamental design of the snake scale is shared by other things in our daily lives--like wheels and ice skates. When comparing snake scales to ice skates, Hu says "they can go easily forward but as you know, when you're ice skating you can push sideways and they'll catch, so we found the snake scales are a lot like wheels and ice skates in that they slide much easier in one direction than in another."
Previous research had assumed that snakes move by pushing off of the rocks and debris around them, but that didn't explain how they can move in areas where there isn't anything to push on. The necessity of snake scales to locomotion can be shown by putting snakes on smooth surfaces or enveloping their scales in cloth. In both of these cases, snakes are unable to slither forward. This is because their scales cannot gain traction on the ground. For their research, Hu and his team designed a special jacket that keeps the snake's scales from gripping the ground. "If you put this jacket on the snake, there's high friction on the ground but the friction is equal in all directions so the snake can't move," says Hu.
Hu's research was supported by a grant from the National Science Foundation (grant PHY 08-48894). To learn more about this research, see the LiveScience article Study shows how snakes slither. (Date of Image: 2009) [Image 9 of 11 related images. See Image 10.]
Credit: ©Grace Pryor, Mike Shelley and David Hu, Applied Mathematics Laboratory, New York University, and Department of Mechanical Engineering, Georgia Institute of Technology
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