Meeting Abstract

59.3  Friday, Jan. 6  The Effects of Substrate Compliance on Jump Performance in the Cuban Tree Frog (Osteopilus septentrionalis). ASTLEY, H.C.*; HARUTA, A.; ROBERTS, T.J>; Brown University; Brown University; Brown University henry_astley@brown.edu

Animals locomoting in arboreal habitats face a variety of challenges, including moving on compliant substrates such as terminal branches. Compliant substrates yield when subjected to locomotor forces, altering the position and magnitude of the reaction force while simultaneously absorbing mechanical work. Substrate compliance may reduce jumping performance due to the loss of mechanical energy to the perch, as well as causing challenges to balance during locomotion. We compared the performance of six Cuban tree frogs (Osteopilus septentrionalis) jumping from a force plate and from perches with four levels of compliance, including rigid. The motion of the frog and perch were recorded via two high-speed cameras and digitized to measure jump performance metrics including kinetic, potential and total energy and takeoff velocity. In order to determine the energy absorbed by the perch during the jump, we quantified the relationship between perch displacement, displacement angle and force from a uniaxial force sensor and simultaneous kinematics. While up to 50% of total jump energy was absorbed by the perch, neither work done during the jump nor takeoff velocity was affected by compliance. This was largely due to recoil of the perch prior to takeoff, which allowed the animal to recover some or all of the energy previously stored as elastic strain energy in the perch. Although there were large movements of the substrate, all frogs were able to maintain balance throughout the jump. Thus, in spite of the mechanical difficulties of jumping off a compliance substrate, Cuban tree frogs show no significant reduction in jump performance. Supported by NSF grant IOS0642428.