Meeting Abstract
Leaping is common in small-bodied arboreal tetrapods, where acrobatic locomotion is often required to move among the three-dimensional substrates of the canopy. However, the narrow diameters of arboreal substrates may constrain leaping performance by comprising mechanical work production during the push-off phase of the leap – i.e., the period prior to aerial take-off when the animal is accelerating the center of mass (CoM) by pushing against the substrate. We used high-speed video and force platforms to investigate the mechanics of three squirrels (Sciurus carolinensis) leaping vertically from flat substrates and poles 9.1, 4.9, and 3.5cm in diameter. Contrary to our hypothesis, leaping performance was not compromised by substrate diameter. Projected leap height (calculated using ballistic equations) did not significantly differ among substrates (p=0.18). However, squirrels used different mechanical strategies to produce the mechanical work required to accelerate the CoM on flat and cylindrical substrates. For a given level of performance (i.e., terminal CoM velocity at the end of push-off), squirrels emphasized greater force production on flat substrates versus increased CoM displacement on cylindrical substrates (all p≤0.001). Our results have implications for understanding leaping adaptations in arboreal animals, suggesting that adaptations to maximize CoM displacement (e.g., greater hindlimb lengths) maybe be more critical for increasing performance than adaptations to maximize force production (e.g., increased hindlimb muscle mass). Future work should investigate how other aspects of arboreal substrate variation, such as angular orientation and compliance, affect mechanical work production during leaping. Supported by NSF BCS-1126790 and NEOMED
