Meeting Abstract
In natural environments, animals must negotiate variable terrain and recover from unexpected perturbations. At present, we know little about the control strategies that animals use in the face of perturbations, but proprioceptive feedback from muscle spindles and golgi tendon organs plausibly play a role in helping animals maintain stability and prevent catastrophic falls. Interestingly, birds and mammals have convergently evolved derived proprioceptive sensory systems compared to other tetrapods. The functional consequences of this variation in proprioceptive sensory systems remain unknown, but it is possible that birds and mammals may be better equipped than other tetrapods to maintain dynamic stability during an unexpected perturbation. In this study, we perturb the running of tufted capuchin monkeys and Savannah monitors with an unexpected drop in substrate height. From these trials, we assess the extent that animals maintain body weight support and spring-like body dynamics in the perturbed step. We compare these data to previously published trials collected from guinea fowl. Our results demonstrate that, despite a great deal of variability in the response, birds and mammals are quite successful in maintaining dynamic stability. The response strategies used by birds and mammals occur across a continuum with varying degrees of body weight support and actuation by the limb related to the magnitude and direction of the ground reaction force impulse. In contrast, during an unexpected fall Savannah monitors stumbled more frequently and revealed no predictable response strategy for maintaining stability based on patterns of ground reaction force impulse. Taken together, these results demonstrate performance consequences associated with differing proprioceptive sensory systems in tetrapods.
