UC Irvine

Moving effectively across a wide range of surface conditions is paramount to acquiring food and finding mates while simultaneously avoiding injury and predation. We used the cane toad, Rhinella marina, as a model organism to better understand how the environment shapes our locomotion because of toads’ jumping gait which pushes locomotor forces to relative extremes. Their amphibious nature also ensures they encounter a wide variety of surface conditions in their natural habitat. In Chapter 1, we used high speed videography and a moveable landing platform instrumented with a force transducer to measure landing kinematics and kinetics. We found that toads did not alter their landing behavior when landing on compliant surfaces. In Chapter 2, we examined the toad’s forelimb muscle activity by implanting electrodes in their pectoralis, deltoideus, anconeus, and palmaris longus muscles. Our results paralleled the findings from Chapter 1, were none of the muscle changed their intensity in preparation for or during landing. In Chapter 3, we tested the idea that hindlimb proprioception was informing forelimb landing behavior by performing sciatic nerve reinnervation which allowed motor control to recover while ablating the stretch reflex. We showed that the elbow joint was significantly affected even 6 months following surgery when hindlimb motor function recovered, suggesting the importance of hindlimb proprioception influencing forelimb landing behavior.