June 30, 2012
They May Not Have 9 Lives, But Lizards Always Land On Their Feet
Lee Rannals for redOrbit.com - Your Universe Online
Cats are not the only species in the animal kingdom that have a knack for always finding a way to land on their feet, lizards have it as well.
According to the research presented at the Society for Experimental Biology meeting Friday, lizards swing their tails one way to rotate their body the other.
The researchers' findings not only explain how large-tailed animals are able to turn themselves right side up while falling, but also could help engineers design air- or land-based robots with better stability.
"It is not immediately obvious which mechanism an animal will use to accomplish aerial righting and recover from falling in an upside-down posture. Depending on body size, morphology and mass distribution there are multiple strategies for animals to execute this behavior," Ardian Jusufi, lead author of the study, said in a statement.
Lizards can encounter many situations in their natural environment where they could find themselves falling, such as when fighting over territory or seeking food. To counter the inevitable fall, lizards developed a way to land safely on their feet.
People have studied for over a century on how cats and other mammals find a way to make themselves turn feet down when falling. Cats twist and bend their torsos to turn upright. However, lizards have a different body makeup, and use strategies researchers have just begun to explore.
The researchers used high-speed videography to dissect the motion of two-common lizards as they fall, starting upside down. The team made observations while watching the lizards right themselves in mid-air, by swinging their tails in one direction, and moving their bodies in the other.
The team also compared the righting movement of two lizards with similar body sizes but different tail lengths during the study. The gecko, which has a shorter tail, has to swing its tail further to the side to right itself, whereas the anole tail is twice as long and doesn't require as much movement, the team said.
"A comparative approach provides useful insights in the study of aerial righting responses and could be beneficial to the design of robots that navigate complex environments," Jusufi commented in a press release.
The scientists not only developed a three-dimensional mathematical model to test their understanding of the lizards' righting movement for the study, but they also designed and built a robot.
The team's "RightingBot" consists of two parts, a body joined to a tail. The RightingBot rights itself in mid-air with a swing of its tail, just like the lizards, showing how useful a tail can be for that purpose, according to the researchers.
Image 2 (below): To turn right-side up when falling, lizards swing their large tails one way to rotate their body the other. Credit: Ardian Jusufi