Meeting Abstract

43.3  Monday, Jan. 5  Gliding Geckos actively use tails for turning. JUSUFI, A*; GAO, P; FULL, RJ; DUDLEY, R; Univ. of California, Berkeley ardianj@berkeley.edu

During free fall geckos reorient from an upside-down to a rightside-up posture by swinging their tail in one direction causing the body to rotate in the other as predicted by the conservation of angular momentum. Upon completion of air-righting, we observed that geckos used tail movements during aerial descent. To test whether active tails play a role, we simulated equilibrium gliding conditions by using a vertical wind tunnel. Geckos, Cosymbotus platyurus, attained terminal velocity at ventral airflows ranging from 4.0 to 7.0 m/s. We observed that turning maneuvers coincided with systematic circular tail movements. Animals that rotated their partially dorsi-flexed tail in a clockwise direction when viewed head-on initiated a clockwise turn to the right in yaw when viewed from above. A clockwise tail rotation when viewed head-on produced an anticlockwise rotation of the tail’s center of mass motion when projected on the plane of the body. Tail rotations in the anticlockwise direction caused an anticlockwise turn in yaw to the left. The sharpest turning maneuvers in yaw occurred when the tail rotated predominately in the plane perpendicular to the gecko’s sprawled torso, thereby projecting the largest circular motion onto the body plane. Moreover, ventral flexion of the tail accompanied pitch-down and dorsal flexion resulted in pitch up. Geckos were capable of actively inducing translation in cranial direction by alternating dorsal and ventral flexion of the tail. Tailless geckos were less effective at maintaining position in the three orthogonal axes of rotation. Reptilian tails can be highly effective appendages for attitude control during aerial locomotion.