Geckos go the Distance: Water's Effect on the Speed of Adhesive Locomotion in Geckos

The gecko adhesive system has been subject to widespread investigation for many decades, but relatively few studies explore environmentally relevant conditions that geckos likely face in their natural habitat. Recent evidence suggests that after Gekko gecko take more than three steps on wet glass, their shear adhesion is significantly lower than adhesion on dry substrates. Such an observation is intriguing because many species of geckos are indigenous to the tropics and must commonly navigate wet substrates. Here we report the locomotor performance of two gecko species, G. gecko and Chondrodactylus bibronii, measured on wet vertical glass and acrylic substrates over a distance of 2 m. We found that neither water nor substrate type had a significant effect on the mean sprint velocity of either species. Mean sprint velocity was unaffected despite variation in frequencies of slipping between species, where C. bibronii slipped significantly more than did G. gecko. Interestingly, the substrate effect on the frequency of slipping was nonsignificant, but misted glass showed a general trend of producing more slips than did misted acrylic. Our results suggest that geckos can sustain adhesive locomotion for at least 2 m on wet substrates.