Seasonal variation in the metabolic rate and body composition of female grey seals: fat conservation prior to high-cost reproduction in a capital breeder?

Carol E. Sparling, John Roger Speakman, Michael A. Fedak

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Many animals rely on stored energy through periods of high energy demand or low energy availability or both. A variety of mechanisms may be employed to attain and conserve energy for such periods. Wild grey seals demonstrate seasonal patterns of energy storage and foraging behaviour that appear to maximize the allocation of energy to reproduction-a period characterized by both high energy demand and low food availability. We examined seasonal patterns in resting rates of oxygen consumption as a proxy for metabolic rate (RMR) and body composition in female grey seals (four adults and six juveniles), testing the hypothesis that adults would show seasonal changes in RMR related to the reproductive cycle but that juveniles would not. There was significant seasonal variation in rates of resting oxygen consumption of adult females, with rates being highest in the spring and declining through the summer months into autumn. This variation was not related to changes in water temperature. Adults increased in total body mass and in fat content during the same spring to autumn period that RMR declined. RMR of juveniles showed no clear seasonal patterns, but did increase with increasing mass. These data support the hypothesis that seasonal variation in RMR in female grey seals is related to the high costs of breeding.

Original languageEnglish
Pages (from-to)505-512
Number of pages8
JournalJournal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
Issue number6
Publication statusPublished - 2006


  • resting metabolic rate
  • seasonal
  • grey seal
  • body composition
  • Southern elephant seals
  • Halichoerus grypus
  • gray seals
  • Harp seals
  • Phoca groenlandica
  • diving behavior
  • sex differences
  • maternal size
  • harbor seals
  • brown bats

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