Active tails enhance arboreal acrobatics in geckos

Abstract

Geckos are nature's elite climbers. Their remarkable climbing feats have been attributed to specialized feet with hairy toes that uncurl and peel in milliseconds. Here, we report that the secret to the gecko's arboreal acrobatics includes an active tail. We examine the tail's role during rapid climbing, aerial descent, and gliding. We show that a gecko's tail functions as an emergency fifth leg to prevent falling during rapid climbing. A response initiated by slipping causes the tail tip to push against the vertical surface, thereby preventing pitch-back of the head and upper body. When pitch-back cannot be prevented, geckos avoid falling by placing their tail in a posture similar to a bicycle's kickstand. Should a gecko fall with its back to the ground, a swing of its tail induces the most rapid, zero-angular momentum air-righting response yet measured. Once righted to a sprawled gliding posture, circular tail movements control yaw and pitch as the gecko descends. Our results suggest that large, active tails can function as effective control appendages. These results have provided biological inspiration for the design of an active tail on a climbing robot, and we anticipate their use in small, unmanned gliding vehicles and multisegment spacecraft.

More than a safety line: jump-stabilizing silk of salticids

“…Besides adjusting the centre of mass (CoM) close to the vector of propulsive thrust at take-off to avoid later body rotation [7,8], some jumpers actively use dynamic control for in-air stability. Two mechanisms have previously been proposed to counteract unwanted torque in the air: using the inertia of swinging appendages [9][10][11][12] and aerodynamic forces from flapping wings [6,7]. Take-off mechanisms and stability control that evolved in nature have led to significant progress in bioinspired designs for manoeuvrable jumping robots [11,13].…”

Optimal Angles for Maximal Adhesion in Living Tokay Geckos

“…During the last century, many of the secrets of the gecko adhesion have been explained , although some crucial problems still remain not completely solved [14,19,21,[31][32][33][34]. Such open questions include function, molecular mechanism, morphological characteristics of the nano-hierarchical structures, mechanism of frictional adhesion, tail function during climbing or aerial descent, and interactive effects of size and loading on kinematics.…”

“…Several scientific studies have been developed to establish the value of the angle a from an experimental [12,21,31,32], computational [14,19,31,41,47], or theoretical [19,29,34,41,46,[48][49][50][51][52][53][54][55][56][57][58]] point of view and at different characteristic sizes of the hierarchical adhesive system. From the literature, the angle a of Tokay geckos (Gekko gecko) is equal to $25.5…”

Robust control of a brachiating robot

“…One possible way to approach this problem is to add a tail or a trunk to the two-link model to create an extra channel for energy input into the system. Tails are crucial in maintaining balance in animals as well as robots (see [20] and [21]). Our hypothesis is that a tail may substantially enhance a brachiator's ability to gain momentum while swinging to brachiate upwards with a greater slope.…”