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Anyone who's seen a gecko crawling up the wall must have wondered how the lizards stick so well. The answer is, of course, the tiny folds and structures on their toes allow them to grip sheer surfaces, but until recently scientists didn't know whether geckos have to exert themselves to stick to things or if it takes no effort at all. Researchers from the University of California, Riverside, have shown that it's the latter.

The underside of a gecko's foot, which is covered in millions of hairlike "setae" that grip the surface.Emily Kane / UC Riverside

They tested the amount of weight a live gecko foot can bear before slipping, then did the same with a dead one. In both cases they performed almost exactly the same, taking about 5.4 newtons of force before losing their grip. This means geckos don't have to waste energy holding on the way a human would have to if one were, for example, hanging from a bar. Geckos can, however, change the amount of grip if they choose to by stretching or retracting their toes, allowing them to slide or drop from a position quickly. The study, by William Stewart and Timothy Higham, appeared in the December issue of Biology Letters.



—Devin Coldewey