Meeting Abstract

25.1  Saturday, Jan. 4 13:30  How Do they Do That? Understanding how Plethodontid Salamanders get Lift Off . HESSEL, A.L.*; NISHIKAWA, K.C.; Northern Arizona University, Flagstaff alh385@nau.edu

Plethodontids have been observed to jump using a unique mechanism in which they bend and unbend their torsos laterally with such force that they hurl themselves into the air. Although the take off, performance and some kinematic data have been described elsewhere, no work to date has been done to fully understand how this behavior leads to propulsion. We have attempted to understand this mechanism by performing a more detailed biomechanical analysis and using a conservation of energy analysis to estimate total useful energy outputs. We further used the engineering application of cantilever beam techniques to find the relative static stiffness of the salamander’s torso in bending and work contribution thereof to the jumping mechanism. We used this knowledge to model the salamander jump. Preliminary results show that energy stored in the torso is directed to the hips, which rotate. The inside hind-limb is anchored before the salamander begins to unbend its body. As the hips rotate and pull against the planted limb, the hips move towards and over the planted limb, catapulting the salamander into the air. Our work has shown that understanding the dynamic center of mass, which changes drastically throughout the bend cycle, is critical to fully understand the mechanical efficiency of this unorthodox jumping mechanism. Further, static stiffness of the salamander’s lateral bend has a major influence on the total work output of the jump mechanism. The jump mechanism may be a link between fish axial stiffness and jumping/walking mechanics of reptiles and mammals, as components from both are visible. Therefore, we encourage further comparative studies. The salamander data has allowed us to build a jumping model based on catapult mechanics and testing of this model against the available data will be pursued.