SCV Outdoor Report: Serpentine Slithering
By Wendy Langhans
When I first learned to ice skate, I used the toe-picks on my blades to push myself forward. I soon discovered, however, that it was not the most effective method. Maybe I should have paid closer attention to how snakes slither.
One of the ways snakes move is through an S-shaped serpentine slither known as lateral undulation. We used to think they did this by pushing laterally against objects on the ground such that, “the lateral force vectors cancel each other, leaving a resultant vector that propels the snake forward”. But new research is causing scientists to re-think their assumptions. Recently I learned that ice skating and slithering snakes may have something in common.
Researchers from New York University and the Georgia Institute of Technology took a closer look at the movement of snakes on a smooth surface. Snakes have overlapping ventral scales on their bellies. Researchers discovered that, “snakes use both friction generated by their scales and redistribution of their weight to slither along flat surfaces”. According to one report, “friction between the scales and a flat surface makes it twice as hard for the snake to slide sideways than forward”.
The force derived from friction “accounts for about 65 percent of the forward movement”. There is a second mechanism that accounts for the other 35 per cent. Researches also noticed that as snakes slither, they lift parts of their body off the surface as they push. (To see what they saw, click here and scroll down to Figure 8.) This redistribution of weight accounts for the rest of the forward movement.
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Ice skaters also use friction-generated force to propel themselves forward. But rather than using ventral scales, skaters derive this force from the side edges of their blades as they stroke backwards AND sideways (laterally). Just like snakes, skaters also redistribute their body weight (from one foot to another). And if skaters want to “slither” around a corner, they perform a maneuver known as a “crossover”, shifting and distributing their weight between the inside edge of the blade on one foot and the outside edge of the blade on the other foot. Watch this video of speedskaters in action, paying special attention to their feet, and you’ll see what I mean.
But even though ice skaters and snakes may share a common mechanism for movement, there’s one critical difference. Have you ever seen a snake wearing chiffon and sequins or carrying a hockey stick? Me neither.
Upcoming Outdoor Events:
Trail Maintenance Schedule. Come join our volunteers as they help maintain our trails. Contact Steve at firstname.lastname@example.org for time and place.
Wednesday mornings, November 2, 9, 16, 23 & 30.
Saturday mornings, November 12 & 26.
Saturday, November 19, 8-10 AM. Autumn in Bird Country. Towsley Canyon. We think autumn is one of the best times to be out and about in the park. The weather is idyllic, the colors are exceptional, and of course the birds are busy preparing for winter. Beginning birds are welcome. Binoculars optional. Meet at the front parking lot. For a map and directions, click here.
Saturday, November 26, 8-10 AM. Where does all the water go? Whitney Canyon. Follow the trail, the water trail, that is, to learn more about our local watershed. If you are not sure why you should care, then come find out. We may just “wet” your appetite for more about this precious resource. Meet in the parking area at Whitney Canyon. For a map and directions, click here.
You can listen to stories like this every Friday morning at 7:10 a.m. on "The SCV Outdoor Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
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