Journal of Comparative Physiology B

, Volume 179, Issue 6, pp 691–700 | Cite as

Energetics of arousal episodes in hibernating arctic ground squirrels

  • Shawna A. Karpovich
  • Øivind Tøien
  • C. Loren Buck
  • Brian M. Barnes
Original Paper

Abstract

Arctic ground squirrels overwintering in northern Alaska experience average soil temperature of −10°C. To examine energetic costs of arousing from hibernation under arctic compared to temperate conditions, captive ground squirrels were maintained in ambient temperatures (Ta) of 2, −5 and −12°C. Rates of oxygen consumption and carbon dioxide production were used to estimate metabolic rate and fuel use during the three phases of arousal episodes: rewarming, euthermia, and recooling. Respiratory quotient comparisons suggest exclusive use of lipid during rewarming and mixed fuel use during euthermia. Animals rewarming from torpor at Ta −12°C took longer, consumed more oxygen, and attained higher peak rates of oxygen consumption when compared to 2°C. Ta had no significant effect on cost or duration of the euthermic phase. Animals recooled faster at −12°C than at 2°C, but total oxygen consumption was not different. Ta had no significant effect on the total cost of arousal episodes when all three phases are included. Arousal episodes account for 86% of estimated costs of a complete hibernation cycle including torpor when at 2°C and only 23% at −12°C. Thus, due to the higher costs of steady-state metabolism during torpor, proportional metabolic costs of arousal episodes at Ta characteristic of the Arctic are diminished compared to relative costs of arousals in more temperate conditions.

Keywords

Oxygen consumption Ground squirrel Spermophilus Metabolic rate Arousal Arctic 

Abbreviations

Ta

Ambient temperature

Tb

Body temperature

MR

Metabolic rate

BMR

Basal metabolic rate

RQ

Respiratory quotient

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Shawna A. Karpovich
    • 1
    • 2
  • Øivind Tøien
    • 1
  • C. Loren Buck
    • 3
  • Brian M. Barnes
    • 1
  1. 1.Institute of Arctic BiologyUniversity of Alaska FairbanksFairbanksUSA
  2. 2.Alaska Department of Fish and GameFairbanksUSA
  3. 3.Biological Sciences DepartmentUniversity of Alaska AnchorageAnchorageUSA

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