Doctoral Dissertation Research: Descent Locomotion Behavior in Primates

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Primates are distinguished from other mammals by their grasping hands and feet, and nails instead of claws. These anatomical features are thought to have helped the earliest primates to navigate thin terminal branches of trees. However, the lack of claws may also have led to different locomotor (movement) behaviors for navigating large trees that could not be grasped. This doctoral dissertation project will study different primate and non-primate mammalian species to better understand locomotor changes with age, and in response to changing environments. These findings can help elucidate broader patterns of interaction between locomotor evolution and life history in the primate lineage. This project will support student training and mentoring at the K-12 through graduate levels. Data generated by this project will be used in an outreach lesson plan demonstrating how animal motion can be understood as simple machines for a STEM education program for elementary to middle school age girls in Durham, NC through Duke University, and for all ages attending annual public outreach days at the Duke Lemur Center. The goal of this project is to understand primate locomotor tradeoffs between selection for or maintenance of morphological specialization for movement in specific places (e.g. thin branches), while still needing to move through and between more general (e.g. trees, the ground) environments. Through comparative analysis of descending locomotion and mechanics in eight primate species, and three non-primate mammals, this project examines behavioral shifts in response to changing environmental conditions by experimentally modifying support orientation and size. Animals are filmed crossing increasingly steep and thick supports, and it is predicted that primates will abandon headfirst walking in favor of alternative behaviors, such as leaping, sliding, and rear-first descending in response to the biomechanical challenges of these supports, while non-primate mammals will continue to move headfirst with the aid of their claws. The comparative sample features species from a wide range of body sizes (0.06 to 3.5 kg), limb proportions, and behavioral specializations. Within each species, individuals of different ages are compared to assess how aging affects arboreal locomotion, which would have been a key challenge incurred during the evolution of increasingly long lifespans in the primate lineage.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.