Real-world challenges to, and capabilities of, the gekkotan adhesive system: contrasting the rough and the smooth

Abstract

Many species of gekkotan lizards possess adhesive subdigital pads that allow them to adhere to, and move easily on, a wide variety of surfaces. However, although the mechanism of adhesion and the potential adhesive capacity of this system have been extensively studied, the adaptive value of these structures and their deployment in natural situations have rarely been examined. The maximal adhesive capacity of gekkotan setal fields has been shown to greatly exceed the force needed to support the body. This high adhesive potential is likely an adaptation for movement on the natural surfaces that these lizards encounter in their environment. Natural surfaces may be rough, undulant, and unpredictable, and provide only limited, patchy areas with which adhesive structures can make contact. Here we examine the microtopography of rock surfaces used by a southern African species of gecko of the genus Rhoptropus Peters, 1869, and compare this to the form, configuration, compliance, and functional morphology of the setal fields of this species. Our results demonstrate that the structure and topology of natural surfaces are important factors in understanding the design of subdigital pads, and provide insight into the evolution of the adhesive system of gekkonid lizards and its adaptive value on topographically unpredictable surfaces.