9 - Energetics

• Published in: Marine Mammals pp. 213 - 236
• Main Authors: Annalisa Berta, James L. Sumich, Kit M. Kovacs, Pieter Arend Folkens, Peter J. Adam
• Format: Book Chapter
• Language: English
• Published: Elsevier Inc 2006
• Edition: Second Edition
• ISBN: 9780120885527; 0120885522
• DOI: 10.1016/B978-012088552-7/50010-2

This chapter focuses on the major patterns of energy expenditures by individuals, including basal metabolism, thermoregulation, swimming, and osmoregulation. Benefits are typically expressed as improved performance or as additional tissue building, either through growth or through reproduction. The field of marine mammal energetics employs a variety of methods to evaluate the energetic costs and benefits of life processes. These processes include the energetic costs of acquiring the needed resources and the manner in which those resources are allocated. Studies of energy allocation in marine mammals help to elucidate the evolution of physiological adaptations of mammals to the challenges imposed by existence in seawater, with its high density, viscosity, and thermal conductivity. The issue of whether marine mammals have higher than expected metabolic rates remains contentious, although it is generally acknowledged that different methods of measurement and the lack of standardized conditions have confounded comparisons. Research on the thermoregulation of seals suggests that ambient air temperatures play an important role in limiting their geographic distribution. Marine mammals also reduce heat loss to the environment by reducing their surface areas. Marine mammals obtain the water they need from the food they eat. The practice of drinking seawater—mariposia—by seals, dolphins, and porpoises has been related to nitrogen excretion and may provide a supplement to water produced oxidatively from metabolizing fat reserves. Among marine mammals, the oldest whales were freshwater animals, indicating that their adaptation to a marine environment occurred later.