Geckos are renowned for their ability to scurry up walls, clinging to surfaces with the help of tiny rows of hair on their toes that generate a subtle electrical attraction known as the van der Waals force. But scientists don't know whether the lizard actively controls its clinging ability using fine muscle movements in its feet or whether its feet are just intrinsically sticky. To decide the issue, biologists at the University of California, Riverside, tested the clinging force of five tokay geckos before and immediately after the lizards were sacrificed. The researchers built a device that dragged the geckos’ feet across an acrylic sheet in a controlled manner, allowing them to precisely measure the pulling force on the reptiles’ toes. To the scientists’ surprise, a dead gecko's foot held to the surface just as tightly as a live gecko's foot, they report online today in Biology Letters. The result shows that geckos do not rely on muscle or neural activity to adhere to surfaces, the researchers say. On the other hand, to detach from a surface, a gecko hyperextends its toes, an ability that appears to be unique among lizards with padded feet.
(Credit for linked videos: William Stewart and Timothy Higham)