Ryan B. Ross

Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Kevin C Daly

Committee Co-Chair

Andrew Dacks

Committee Member

Sarah M Farris


Animals have evolved mechanical and neural strategies for locomotion in almost every environment, overcoming the complexities of their habitats using specializations in body structure and animal behavior. These specializations are created by neural networks responsible for generating and altering muscle activation. Species specific musculoskeletal anatomy and physiology determine how locomotion is controlled through the transformation of motor patterns into body movements. Furthermore, when these species specific locomotor systems encounter perturbations during running and walking their behavioral and mechanical attributes determine how stability is established during and after the perturbation. It is still not understood how species specific structural and behavioral variables contribute to locomotion in non-uniform environments. To understand how these locomotor properties produce unique gaits and stability strategies we compared three species of brachyuran crabs during normal and perturbed running. Although all crabs ran sideways, morphological and kinematic differences explained how each species produced its unique gait and stability response. Despite the differences in running behavior and perturbation response, animals tended to use locomotor resources that were in abundance during stabilizing responses. Each crab regained stability during the perturbation response by altering leg joint movements or harnessing the body's momentum. These species body designs and running behavior show how slight changes in body structure and joint kinematics can produce locomotor systems with unique mechanical profiles and abilities. Understanding how evolutionary pressures have optimized animals' locomotor ability to successfully move in different environments will provide a deeper understanding of how to mimic these movements through mathematical models and robotics.