Meeting Abstract
Impact dynamics underlie many biological motions including prey capture and locomotion. Oftentimes, the size and time scale of these impacts allow for measurement with force transducers, strain gauges, or accelerometers. However, motions like the ultrafast mandible strikes of a trap jaw ant occur at incredibly small scales placing them outside the range of traditional sensors. Furthermore, these strikes have many uses (from prey capture to mandible powered jumps) against diverse biotic and abiotic materials. When measuring these strikes, we must consider the material properties of the struck target, whether or not the target is fixed, and the contact duration. Here we measure energy transfer from a trap jaw ant into a target with a novel two-pendulum device. The device consists of two separate pendulums with an ant affixed to the end of one pendulum and a target affixed to the end of another. We tested impacts on two target materials: spring steel and polyurethane. We hypothesized that impacts on spring steel would yield higher energy outputs than the more compliant polyurethane. Each target material was tested by positioning the ant close to either a freely-swinging target or a fixed target to provoke a strike. Our data supported the hypothesis that, due to differences in energy absorption, impacts with polyurethane yield lower average energy of pendulum motion (6.3 μJ) than with spring steel (22 μJ). Fixing the targets did not significantly affect measured energy. Contact duration was a key predictor of energy across all treatments. Longer contact durations led to lower measured energy, which is a fundamentally different dynamic of these small impact systems compared to larger jumping animals that maximize ground contact time to enhance energy exchange during impact.
