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Leaping lizards give technology a nudge
Red-headed agamas are put through their paces in a lab to see whether their agility could be replicated.
Last Modified: 07 Jan 2012 17:40
How the Rock Agama lizard, native to sub-Saharan Africa, moves might be key to building safer cars [GALLO/GETTY]

When fantasising about cars that move like animals, a muscular mustang or a sleek cheetah might be the images that come to mind.

But how about a car that moves like a lizard? Don't be so quick to judge.

Jumping lizards adjust the position of their tails in mid-air to ensure a smooth landing, and certain agile dinosaurs probably did likewise, so say a team of biomechanics who put some red-headed agama lizards (the Agama agama) through their paces in a laboratory.

The scientists filmed the African reptiles as they jumped from a horizontal platform to a vertical wall.

Slow-motion footage showed that if a lizard had to hoist the front part of its body in order to land correctly, it bent its long, slender tail upwards. By curling its tail, the lizard provided a clockwise movement that gave an anticlockwise tilt to the front of its trunk. This enabled the critter to land safely, paws-first, onto the wall.

Tailbot and lizard, side by side [UC Berkely News Centre]
 

Few lizards may have known this, but they were upholding the principle of conservation of angular momentum by exploiting the moment of inertia.

Tightrope walkers, too, use this principle. They correct their balance by using a long pole. It is tilted to make the body lean in the opposite direction to the tilt.

The team, led by Robert Full of the University of California at Berkeley, built a lizard-sized robot car, complete with a tail controlled by gyroscopes, to see whether the lizard's agility could be replicated by technology.

The Poly-PEDAL lab (PEDAL is an acronym for performance enerergetics dynamic animal locomotion) at UC Berkley, researchers study the movement several creatures - from carpenter ants to fidddler crabs, in order to best understand the principles of locomotion, building different robotic models to represent what they see in nature.

When the lizard car jumped off the ramp, it started to fall nose-first, but this angle was smartly corrected by a movement of the tail, and the toy vehicle - named "Tailbot" - landed on its wheels. The lab has already created a Mecho-gecki, which can climb walls and ceilings.

Previous research has suggested there are several species of animals that use their tail to harness the moment of inertia, including lemurs, cats and kangaroo rats.

The paper speculates that small, two-footed carnivorous dinosaurs, including the velociraptor made notorious by the movie Jurassic Park, may also have done the same trick.

Larger dinos, though, are unlikely to have jumped far, if calculations of their bone-to-muscle ratio are right.

Source:
Al Jazeera and agencies
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