Geckos are remarkable little creatures, clinging to almost any dry surface, and Alyssa Stark, from the University of Akron, USA, explains that they appear to be equally happy scampering through tropical rainforest canopies as they are in urban settings. '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', says Stark. She adds that the animals grip surfaces with microscopic hairs on the soles of their feet that make close enough contact to be attracted to the surface by the minute van der Waals forces between atoms. However, she and her colleagues Timothy Sullivan and Peter Niewiarowski were curious about how the lizards cope on surfaces in their natural habitat.
Explaining that previous studies had focused on the reptiles clinging to artificial dry surfaces, Stark says 'We know they are in tropical environments that probably have a lot of rain and it's not like the geckos fall out of the trees when it's wet'. Yet, the animals do seem to have trouble getting a grip on smooth wet surfaces, sliding down wet vertical glass after a several steps even though minute patches of the animal's adhesive structures do not slip under humid conditions on moist glass. The team decided to find out how Tokay geckos with wet feet cope on wet and dry surfaces, and publish their discovery that geckos struggle to remain attached as their feet get wetter in The Journal of Experimental Biology at http://jeb.biologists.org.
But first they had to find out how well their geckos clung onto glass with dry feet. Fitting a tiny harness around the lizard's pelvis and gently lowering the animal onto a plate of smooth glass, Stark and Sullivan allowed the animal to become well attached before connecting the harness to a tiny motor and gently pull the lizard until it came unstuck. The geckos hung on tenaci
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The Company of Biologists