Meeting Abstract
42.3 Saturday, Jan. 5 Tail-induced Air-righting Maneuver Reorients Geckos. JUSUFI, A.**; REVZEN, S.; FULL, R.J.; Univ. of California, Berkeley ardianj@berkeley.edu
Despite morphological and behavioral adaptations to enhance stability during climbing (Jusufi et al., 2007), falls occur frequently among arboreal reptiles. We observed that rapidly climbing geckos (Cosymbotus platyurus) that fell or jumped off the wall always landed with the ventral side facing the ground independent of the initial posture at take-off. To examine how geckos executed rapid air-righting reactions, we placed them upside-down (supine position) on a light, loosely-mounted platform. Upon loss of foothold, geckos immediately spread their feet out laterally and fell in a supine posture (average latency 45 ± 5 ms, n=16). Next, the tail pitched into a position perpendicular to the longitudinal axis of the torso, while the head pitched back toward the ground. A cyclic rotation of the tail about the longitudinal axis produced a counter-rotation of the body. As the geckos attained prone posture, tail rotation stopped, thus terminating the zero angular momentum air-righting response (average reorientation time 106 ± 6 ms, n=16). In nearly 70% of the trials, the tail alone generated air-righting without head-shoulder or shoulder-pelvis rotations. All geckos that induced reorientation with their tails recovered from a supine posture to attain a near prone posture (approximately 140° – 180° of rotation). Fully prone posture was attained in half the trials within 23 cm from the take-off location. By contrast, none of the tailless attained a fully prone posture within the same vertical falling distance (n=19). In approximately half the trials, tailless geckos rotated only 90° (half way) toward the prone position by twisting. Moment of inertia ratios predicted by a model were not significantly different from our direct kinematic measurements of rotation (n=6), thus suggesting that the gecko�s tail is capable of generating sufficient rotational impulse moments to account for a reorientation of its body.
