Meeting Abstract
To move most directly between two locations, arboreal animals often must cross gaps between branches or trees. Arboreal snakes have an impressive ability to cantilever when bridging gaps, anchoring themselves posteriorly while extending the anterior body to cross the gap. Cantilevering is biomechanically constrained by the torque required to support the body, but some snakes can extend their reach using dynamic lunging. The flying snake Chrysopelea paradisi often initiates glides with a “J-loop” take-off, in which the snake forms a hanging curve with the anterior body and rapidly straightens to depart the branch. Such jumping, which is more energetic than lunging, could be employed in gap-bridging. Here, we used a six-camera motion-capture system (Vicon Motion Systems Ltd.) to investigate whether jumping increases the distances flying snakes are able to traverse, and if so, to determine the factors that precipitate the transition from cantilevering to jumping. Preliminary data from 96 trials suggests that C. paradisi uses both lunging and jumping once the snake is unable to cantilever, and that jumping increases the achievable gap distance they can cross. For one snake (mass: 68.7 g, SVL: 72 cm), cantilever failure occurred at 55% SVL, and larger gaps were successfully crossed using either lunges or J-loop jumps. For gaps of 80% SVL and above, the snake used the J-loop jump exclusively, enabling it to cross gaps of at least 100% SVL. In comparison, Boiga irregularis, an excellent arboreal climber, can cross a maximum gap of 64% SVL, indicating that the use of jumping may confer a greater gap-bridging ability to C. paradisi. Hence, jumping in Chrysopelea may serve as a mechanism to increase locomotor effectiveness in patchy arboreal environments, and may have evolved independently of gliding. Supported partially by NSF 1351322.
