Mark Fernandez, age 11, of Shreveport, Louisiana, for his question:
Is it true that a snake uses hairs to crawl?
The snake is a cold blooded reptile and only the warm blooded mammals grow hairs of any sort. It is true that many snakes do have small grippers along their undersides to help with the crawling. But they are not hairs, or even bristles though they are made of similar material. However, these tiny grippers play only a small role in helping the snake to crawl. Most of the snaky motion is performed by smooth teamwork involving the long, supple spine, dozens of ribs and highly specialized muscles, plus a helping hand from the scaly skin.
Few things in nature are more graceful than a slithering snake. Some snakes use slightly different methods of locomotion but every one of them moves with smooth elegance. Many of them swim as efficiently as they glide on land. Some are talented tree climbers. And all this motion is performed without hands or feet, arms or legs. The only handicap to this legless locomotion is a slippery surface. A snake cannot navigate across a sheet of glass and most snakes find it hard to trek across sandy deserts.
If you have never seen him in motion, you may think that a snake arches his body in hills and dales. This is not so. He travels by bending his pliable body in waves from side to side and, except in a few cases, he keeps his entire tummy flat on the ground. The important trick is getting a solid grip on the earth. To help him he has a row of special scales, not hairs, on his underside. They are larger and stiffer than his other scales.
The wavy motion from side to side depends on his long, supple spine, rows of ribs attached to his vertebrae, and ribbons of smooth muscles that control the bones, the body and the scaly skin. A long snake may have 300 to 400 pairs of ribs, each pair attached to a vertebra. They curve around and enfold his body in a tubular cage.
When he makes a U turn, the ribs on the inside of the curve gather together and those on the outside of the curve spread farther apart. As he glides forward, the spreading and closing ribs alternate from side to side in a rippling motion. Meantime the scaly grippers on his underside help to keep him from sliding backward. This however, is not enough. He also makes use of stones, grassy tufts and other bumps on the ground.
His gliding waves use these firm props to push forward instead of sliding backward.
These devices do not help the sidewinder of our southwestern deserts. The sand is too loose for scaly grippers and the stones are too loose for firm props. But this rattlesnake solves the problem in his own extraordinary way. He coils his sturdy body in an S shape with his side loops slightly lifted. Only his chin and tail end touch the ground. Then he uncoils his full length with a forward lunge. The next side windering step is another coiled “S” and another forward lunge.
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