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Title: Scaling of running stability and limb posture with body size in galliform birds
Author: Birn-Jeffrey, Aleksandra Victoria
ISNI:       0000 0004 2738 3339
Awarding Body: Royal Veterinary College (University of London)
Current Institution: Royal Veterinary College (University of London)
Date of Award: 2012
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This is the first study of the scaling of stability and the consequences of body size for negotiating uneven terrain. Animals must maintain stability to successfully negotiate these complex environments, but the field lacks established metrics for stability that are appropriate in a biological context. Understanding the neural control, behaviour and mechanical strategies that animals use in uneven terrain locomotion will provide insights into trade-offs and help design better legged robots. In this thesis, I investigate the neuro-mechanical strategies used by birds in uneven terrain, exploring possible trade-offs between stability, robustness to terrain height, and avoidance of injury due to high peak forces. The experimental data is from a runway with a single obstacle, varied in height between 0.1-0.5 relative to leg length. I examine whether ground-dwelling birds (galliforms and ostrich) spanning a 400 fold range of body size employ different strategies for obstacle negotiation. I expected heavier animals to avoid high peak forces to maintain constant muscle and bone stresses. In the process of this investigation, I have also explored possible metrics for stability and robustness. Surprisingly, all birds employ the same strategy for negotiating an obstacle, across species and obstacle heights. Unexpectedly, strategy did not change with body mass and limb posture. Across the 400-fold size range, leg function during obstacle negotiation is consistent with a reductionist leg model including a damper and a linear leg actuator, with work output determined by landing conditions. Robust stability relies on the interplay of swing and stance control; birds adjust the swing leg trajectory to control landing conditions, which combined with intrinsic mechanics explains the variation in stance leg work, allowing birds to negotiate the obstacle while maintaining relatively constant velocity. The findings suggest a universal control policy across a 400-fold size range that shows promise for the control of legged robots.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Birds - Anatomy and physiology, Birds – Locomotion, Galliform birds, Turkeys, Poultry – Behavior, Chickens - Behaviour