How do geckos do it? How do the cute little lizards keep their footing when scurrying up and down wet, slippery tree trunks and leaves in their rainforest habitat?
Well, it's all about hairs -- not on the geckos' bodies but on the bottoms of their toes. These tiny flat-tipped filaments give gecko toes a tenacious grip on wet as well as dry surfaces -- and, new research shows, even when the little guys are completely submerged underwater.
"The major finding in the study really is that we found that geckos can stick underwater," study co-author Alyssa Stark, a doctoral candidate at the University of Akron, told The Huffington Post. "So on certain surfaces they really suffer no loss in adhesion, and for us that’s really interesting."
Gecko toes include different rows of these small hairs, creating many points of surface contact for adhesion in which the gecko may grip -- so there is no special chemical glue involved here.
"And with the gecko, they’re able to reuse their adhesive system," Stark said. "In this case, geckos can walk underwater so they’re reusing their adhesive system over and over again."
The researchers tested the grip of six geckos, which they outfitted with harnesses, by tugging gently as the lizards clung to surfaces in wet and dry conditions.
They found that water only impacts geckos' adhesion on glass and other surfaces with high "wettability," meaning the surface attracts water molecules. Geckos still stick to wet surfaces that are hydrophobic, meaning the surface repels water. Think waxy tree leaves.
“The geckos stuck just as well under water as they did on a dry surface, as long as the surface was hydrophobic,” Stark said in a written statement. “We believe this is how geckos stick to wet leaves and tree trunks in their natural environment.”
The study, "Surface Wettability Plays a Significant Role in Gecko Adhesion Underwater," was published Monday in Proceedings of the National Academy of Sciences.