Integrative Biomechanics of Marine Mammals; Adaptations for Feeding, Diving, and Hearing in Whales

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We study how animals work from an engineering and physics perspective. New work will focus on marine mammals, principally rorqual baleen whales. After decades of commercial exploitation with countless opportunities for study, details of their anatomy and biomechanics remained obscure until lately. Building on recent successes, our discovery research seeks to further our understanding of anatomical, physiological, and biomechanical adaptations that support their aquatic lifestyle. We will use anatomy, tissue biomechanics, and computer and digital modelling to infer physiological function in four key areas: *** Lunge feeding hydrodynamics, energetics. Hydrodynamic and metabolic models of engulfment will be refined with quantified hydrodynamic performance of flexible, scaled models of rorqual tail flukes, following methods from past studies of fish tails. Combining results with computational fluid dynamics will inform mathematical energy budget models by adding realistic costs of hydrodynamic drag forces for different body sizes and speeds. *** Circulatory system design for rapid pressure changes during swimming and diving. With field measured heart rate data from a collaboration, we will revisit our old hemodynamic model of the central circulation to see how flow is optimized during a dive. We will study the mechanical properties and 3D structure of thoracic and cranial vascular retia from post-mortem cases, and then use mathematical modelling to test hypotheses of how retia protect the brain from flow transients during rapid changes in internal pressures. *** Respiratory system design and lung collapse at depth. We will address how nasal plugs and blowhole protect the upper airway from water incursion and how special pharyngeal structures protect the rorqual upper airway from food during swallowing. We will continue a comparative study of morphology and mechanics of lower airway structures in numerous species, using lung inflations, 3D lung and trachea anatomy from CT scans, and microscopy and composition of alveolae to determine how lungs empty in respiration and collapse at depth. Based on a hyperbaric CT scan, we will create a finite element model of thoracic compression to see how thoracic wall and diaphragm deformation compress the lungs at depth and shift blood volumes between the thorax and the thoracic and cranial retia. *** *Inner ear structure and hearing. We now know how to image cochlea hair cells, and have made the first spatial frequency map of a whale (beluga) cochlea with the aim of linking damage seen in stranded casualties to specific sound sources. We plan similar work on additional species, including rorquals, whose hearing capacities are unknown. ******Our research program on whale biomechanics will produce the most comprehensive and quantitative study of swimming, diving and feeding in the great whales, and their anatomical and physiological adaptations specific to these functions.**