Geckos running with dynamic adhesion: towards integration of ecology, energetics and biomechanics

Integrating biomechanics, energetics and ecology perspectives in locomotion

Scientific fields evolve a culture and vocabulary that create a group identity but may result in reduced understanding by people in apparently adjacent but different fields. Here, a series of articles written by scientists active in biomechanics, energetics and ecology relevant to locomotion forms the basis of researchers striving to bridge those divides and providing a common language and perspective.

Frictional adhesion of geckos predicts maximum running performance in nature

Despite the myriad studies examining the diversity and mechanisms of gecko adhesion in the lab, we have a poor understanding of how this translates to locomotion in nature. It has long been assumed that greater adhesive strength should translate to superior performance in nature. Using 13 individuals of Bradfield's Namib day gecko (Rhoptropus bradfieldi) in Namibia, I tested the hypothesis that maximum running performance in nature (speed and acceleration) is driven by maximum frictional adhesive strength. Specifically, those individuals with greater frictional adhesion should escape with faster speed and acceleration because of increased contact with the surface from which to apply propulsive forces. I tested this prediction by quantifying laboratory adhesive performance and then releasing the geckos into the field while simultaneously recording the escape using high-speed videography. Additional measurements included how this species modulates maximum running speed (stride length and/or stride frequency) and how temperature influences field performance. I found that maximum acceleration was significantly correlated with maximum frictional adhesive strength, whereas maximum sprinting speed was only correlated with increases in stride frequency (not stride length) and temperature. Thus, different measures of performance (acceleration and speed) are limited by very different variables. Acceleration is key for rapidly escaping predation and, given their correlation, maximum frictional adhesion likely plays a key role in fitness.