Snake locomotion may seem simple compared to walking or galloping. But in reality, it's no easy task to move without legs. Previous research has assumed that snakes move by pushing off of rocks and debris around them. But a study published this week in the Proceedings of the National Academy of Sciences says that it's all in their design--specifically, their scales.
Overlapping belly scales provide friction with the ground that gives snakes a preferred direction of motion, like the motion of wheels or ice skates. Like wheels and ice skates, sliding forward for snakes takes less work than sliding sideways.
In addition, snakes aren't lying completely flat against the ground as they slither. They redistribute their weight as they move, concentrating it in areas where their bodies can get the most friction with the ground and therefore maximize thrust. In this way, snake slithering is not unlike human walking--we, too, shift our weight from left to right to enable us to move.
Source: National Science Foundation