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.Abstract
Mean (±95% C.I.) SV on misted substrates subtracted from mean SV on dry substrates (SVD−M in cm/s) are represented on the y-axis. Mean SVD−M values on both glass and acrylic for Chondrodactylus bibronii and Gekko gecko are displayed. Positive values indicate the mean SV was lower on the misted susbstrate compared to the dry substrate. Negative values indicate the mean SV was higher on the misted substrate compared to the dry substrate. Neither species (F1,7 = 1.4925, P = 0.2614), substrate type (F1,7 = 0.9165, P = 0.3703), nor their interaction (F1,7 = 0.8707, P = 0.3818) had a significant effect on SVD−M.
Mean (±SE) frequency of slips for Chondrodactylus bibronii and Gekko gecko on all substrates. Chondrodactylus bibronii slipped significantly more compared to G. gecko (F1,7 = 7.2977, P = 0.0306).
Mean (± SE) frequency of slips on either glass or acrylic for all geckos are displayed. The effect of substrate type on the frequency of slips was not significant (F1,7 = 5, P = 0.0604) but showed a general trend wherein misted glass produced more slips than did acrylic.
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