Scientists study tree frog 'stickiness'

GLASGOW, Scotland, April 2 (UPI) -- Scottish scientists have determined how tree frogs can stick to smooth surfaces even when completely upside down, yet can easily walk or jump.

"The toe pads of tree frogs are coated with a thin mucus which adhere to surfaces by wet adhesion, like wet tissue paper sticking to glass," said lead researcher Jon Barnes of the University of Glasgow. "The process by which they detach their toe pads is called peeling and is akin to us removing a sticking plaster from ourselves."

The scientists measured adhesive and frictional forces simultaneously on individual toe pads of White's tree frogs while varying the surface angle. It was found the change from adhesion to peeling is a gradual process, with adhesive forces weakening at angles above 90 degrees. Thus, said the researchers, frogs maintain a grip by keeping the angle of their toes with respect to a surface at a low value, and detach when this angle increases beyond 90 degrees.

The study was presented Monday in Glasgow during the annual meeting of the Society for Experimental Biology.