Washington, March 18 : In a new research, biologists have determined that geckos rely on their tails to keep from falling off vertical surfaces and doing aerial maneuvers, which is already helping engineers design better climbing robots and may aid in the design of unmanned gliding vehicles or spacecraft.
University of California (UC) Berkeley biologists carried out the research.
According to senior author Robert J. Full, professor of integrative biology at UC Berkeley, previous experiments on geckos have focused on their unique toes as the key to running up a wall and hanging onto ceilings.
Full discovered six years ago that, while claws help geckos climb rough surfaces, millions of microscopic toe hairs make it possible for them to climb smooth ones.
Only when engineers began building gecko-like robots, such as Boston Dynamics Inc.'s RiSE (Robot in Scansorial Environment), the University of Pennsylvania's DynaClimber and Stanford University robots Spinybot and Stickybot - all inspired by Full's findings - did they discover that a tail might be necessary to prevent the robot from pitching backward and falling when it slips on a vertical surface.
When Full and UC Berkeley graduate student Ardian Jusufi went back to the lab to look at how geckos, specifically the flat-tailed house gecko, Cosymbotus platyurus, of Southeast Asia, use their tails, they discovered that the tail is critical for dealing with slippery surfaces.
"When we ran all of our geckos on perfect surfaces, they never slipped, and they didn't use their tails. But when we put in a slippery patch, we found that they have an active tail that functions like a fifth leg to keep them from tipping backward," said Full.
"This is an undiscovered function for tails that tells us a lot about how active tails could affect the performance of vertebrates," he added.
With the help of high-speed video, the researchers discovered that when a gecko loses traction with one leg, it taps its tail on the surface to prevent pitch-back until the toes can grab hold again.
"If a gecko loses traction with more than one foot, the researchers found, it will often flatten its tail to the surface to prevent a fall in a move that has the effect of a bicycle kickstand," said Full.
Using either the tail-tapping or tail-flattening technique, nearly all geckos were able to navigate across slippery patches on a vertical wall.
"We were really surprised to see that they could pitch back up to 60 degrees, return to the vertical surface and still traverse the slippery patches," said Jusufi.
The engineers with whom Full collaborates are now devising active tails for their robots to replicate these moves, which in a gecko are probably reflexive.