Snakes can slither across flat surfaces without legs because their scales act as friction hooks which catch in rough points on surfaces, a new study shows.

The finding could eventually lead to robotic snakes that move more naturally claims David Hu, a mechanical engineer at Georgia Tech, who has been studying snakes to learn above their movement.

"When I first started studying snakes, we didn't have personal computers or robotics," he said, "But now we have the tools to emulate nature."

Dr Hu has spent decades studying the movement of creatures. As a young researcher he showed how mosquitoes can use their spindly legs to stand on surfaces ranging from walls to water.

Biologists have previously observed the unusual properties of snake scales, but no one had tried to connect them with how snakes move until now.

Some had speculated that snakes needed twigs or rocks to push against, but failed to explain how snakes navigated fairly featureless surfaces such as desert sands.

"We wanted to come up with the simplest possible explanation for how snakes move on flat ground," Hu told LiveScience.

The Georgia Tech researchers first tested the snake scale friction by sliding unconscious snakes across flat surfaces. Snakes slid easily in the forward direction, but their scale friction resisted sliding backwards or sideways.

Next, Hu and his colleagues recorded the movement of the awakened snakes on very smooth fiberboard, and on cloth that provides a relatively rougher surface. The snakes had trouble moving on the smooth fiberboard, but could move more easily on a cloth-covered plank.

However, the snakes ran into movement difficulties again when researchers fitted them with a cloth jacket, which basically eliminated the scale friction.

And a time-lapse camera showed they can also move sidewinding motion, or even scrunch themselves up like an accordion.

"Snakes have a lot of different ways of moving, sort of like a horse that can trot or gallop," Hu said.

The study's model had successfully used the scale friction to predict much of the snake movement, but only accounted for 65 percent of the speed. Something else was missing.

Then the researchers noticed that the snakes were lifting parts of their bodies as they slithered forward on the recorded videos.

Hu described it as "dynamic weight distribution" that allowed snakes to concentrate their weight on a few points and move more quickly.

"That can lead to sidewinding, but they can also more subtly shift their weight," Hu noted. "It will change the speed of snake a great deal."

The study was reported in the journal Proceedings of the National Academy of Sciences.