What Happens When Geckos Get Wet Feet

Geckos seem to be equally at home on dry walls in people’s houses as they are on damp trees in tropical rainforests, but a new U.S. study shows these lizards don’t grip so well once their feet get wet.

“A lot of work is done on geckos that looks at the very small adhesive structures on their toes to really understand how the system works at the most basic level,” said study co-author Alyssa Stark at the University of Akron in a press release. However, few studies have looked at the wet conditions relevant to geckos’ natural habitats.

Microscopic hairs on the soles of gecko’s feet contact the surface closely enough to form van der Waals forces between atoms, but the lizards still slide down wet glass after several steps.

Firstly, the researchers looked at the strength of geckos’ grip on glass with dry feet. Using a tiny harness attached to a motor, they found it takes a force of about 20N, or 20 times the gecko’s body weight to unstick it from a glass plate.

Next, they sprayed the glass lightly with a water mister and found the lizards were less able to hold on whenever they took a step. Even though their toes repel water, the water around their feet prevented them from bonding to the surface.

Then, the team tested how well the geckos stuck to dry glass after their feet had been soaked for 1.5 hours. They discovered the lizards had trouble holding on, detaching when pulled with a force roughly equal to their weight.

“That might be the sliding behavior that we see when the geckos climb vertically up misted glass,” says Stark.

So it seems geckos can only walk on wet surfaces if their feet are fairly dry. The researchers aim to find out how long it takes geckos’ toes to work again after drenching.

The study was published in the Journal of Experimental Biology on Aug. 9.

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