Biomechanics and neuromuscular control of maneuvering flight

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The ability of an animal to maneuver can determine its success at avoiding predators, catching food, and other fundamental behaviors that define the margin between life and death. Most research on the biomechanics of animal motion has concerned the initiation or maintenance of ballistic, brief, or steady state movements because these can be studied most readily in the laboratory. Maneuverability is therefore one of the most important but least understood aspects of animal locomotion. Previous research has progressed along two independent tracks: 1) Studies of animal morphology have explained how the size and shape of the body and the limbs influence the efficiency and dynamics of maneuvering. 2) Studies of neuromuscular physiology have revealed the mechanisms that animals use to power particular maneuvers. However, animals with the ability to generate substantial muscle power, such as those that hover or fly slowly, may be able to overcome efficiency costs imposed by suboptimal morphology to generate rapid but inefficient maneuvers. The proposed work will test the hypothesis that the limitations imposed by morphology are strongest when muscle power-generating capacity is low. Research will focus on the remarkable maneuvering flight of hummingbirds because these animals inhabit broad elevational ranges, which provide natural experiments for varying muscle power capacity. Two experimental approaches will be employed. The first is to use a wide field tracking system to study unconstrained flight trajectories. Techniques in computer vision will be used to decompose these complex movements into fundamental units called motion primitives. As a coarse analogy, these elements function like the movements performed in classical ballet such as pirouettes or entrechats, which are strung together to form a complete dance. Motion primitives therefore provide focus for describing the complexities of animal motion. The second approach will examine the biomechanics and neurophysiology underlying the motion primitives. The two approaches are reciprocally informative and will allow for a quantitative description of maneuverability and a mechanistic understanding of its limits.