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Article
Biomechanics and Energetics in Aquatic and Semiaquatic Mammals: Platypus to Whale
Physiological and Biochemical Zoology
  • Frank E. Fish, West Chester University
Document Type
Article
Publication Date
11-1-2000
Disciplines
Abstract
A variety of mammalian lineages have secondarily invaded the water. To locomote and thermoregulate in the aqueous medium, mammals developed a range of morphological, physiological, and behavioral adaptations. A distinct difference in the suite of adaptations, which affects energetics, is apparent between semiaquatic and fully aquatic mammals. Semiaquatic mammals swim by paddling, which is inefficient compared to the use of oscillating hydrofoils of aquatic mammals. Semiaquatic mammals swim at the water surface and experience a greater resistive force augmented by wave drag than submerged aquatic mammals. A dense, nonwettable fur insulates semiaquatic mammals, whereas aquatic mammals use a layer of blubber. The fur, while providing insulation and positive buoyancy, incurs a high energy demand for maintenance and limits diving depth. Blubber contours the body to reduce drag, is an energy reserve, and suffers no loss in buoyancy with depth. Despite the high energetic costs of a semiaquatic existence, these animals represent modern analogs of evolutionary intermediates between ancestral terrestrial mammals and their fully aquatic descendants. It is these intermediate animals that indicate which potential selection factors and mechanical constraints may have directed the evolution of more derived aquatic forms.
Publisher
University Chicago Press
DOI
10.1086/318108
Comments
© 2000 The University of Chicago Press
Citation Information
Frank E. Fish. "Biomechanics and Energetics in Aquatic and Semiaquatic Mammals: Platypus to Whale" Physiological and Biochemical Zoology Vol. 73 Iss. 6 (2000) p. 683 - 698 ISSN: 1522-2152
Available at: http://works.bepress.com/frank_fish/2/