A Lizard That Can Swim on Dry Land: Study Shows How a Desert Dweller Slithers through Sand

Article excerpt

The sandfish lizard wriggles through desert sands like a sci-fi monster. Now, using computer simulations and bendy robots, researchers at Georgia Tech in Atlanta and Northwestern University in Evanston, Ill., have taken the most complete look yet at the physics of burrowing animals. And, boy, does this reptile wriggle, the team reports online March 4 in the Journal of the Royal Society Interface. "This particular behavior is built for speed," says study coauthor Daniel Goldman, a physicist at Georgia Tech.

Like the deadly sandworms in the Dune science fiction series, a host of animals from scorpions to snakes burrow in desert sands across the planet. It's not easy to study how these creatures careen through their environments, Goldman says. Scientists have a good idea how water behaves in the wake of an undulating eel or how air flows over a bird wing. But shuffling sand grains ping off each other like billiard balls in a wickedly complicated game of pool.

X-ray studies have shown that sandfish lizards (Scincus scincus) navigate such chaos with a wormlike wriggle, Goldman says, tucking in their legs and curling from side to side in S-shaped waves. The creatures can grow to 4 inches long, and a fast sandfish lizard dive covers two body lengths per second. But just how the lizards achieve such speed in a complex sandy environment wasn't clear. For that, Goldman's team turned to a new set of tools.

First, researchers simulated sandfish lizards swimming in a sea of 3-millimeter-wide glass beads. The program--which ate up 20 to 30 desktop PCs and still took days to run--illustrated how every bead bumped and thudded as the virtual lizard passed by. …