Meeting Abstract
Many geckos adhere to surfaces with remarkable strength using toe pads on the bottom of their digits. A single toe pad, consisting of thousands of microscopic and adhesive setae, is capable of supporting a gecko‘s entire body weight. While the micro-mechanics of these setae are well-studied, our understanding of gecko adhesion at the whole-animal level is limited. It remains unclear whether geckos control the clinging strength of their toe pads, or whether the magnitude of adhesion is passively determined. Considering that a complex tendon system connects the toe pads with limb muscles, we tested the hypothesis that geckos use muscle activity to actively control pad position and the resultant loading of setae. This was achieved with experiments that compared the clinging ability of Tokay geckos (Gekko gecko) before and immediately after death. Using a novel device that applied repeatable and steady-increasing pulling forces to the foot in shear, we found that death, surprisingly, did not affect the dynamic adhesive force or motion of a gecko foot when pulled along a vertical surface. Adhesive force was similarly high and variable when the animal was alive (mean±SD = 5.4±1.7 N) and within 30 min after death (5.4±2.1 N). However, kinematic analyses revealed that live geckos are able to control the degree of toe pad engagement and can rapidly stop strong adhesion by hyperextending the toes. These findings suggest that living processes, such as muscle activity, are not required for strong adhesion by geckos.
