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. BarnesEmail author
Original Paper


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 (T a) 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 T a −12°C took longer, consumed more oxygen, and attained higher peak rates of oxygen consumption when compared to 2°C. T a 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. T a 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 T a characteristic of the Arctic are diminished compared to relative costs of arousals in more temperate conditions.


Oxygen consumption Ground squirrel Spermophilus Metabolic rate Arousal Arctic 



Ambient temperature


Body temperature


Metabolic rate


Basal metabolic rate


Respiratory quotient



This study was supported by grants from the NSF (9819540 and 0732755), the US Army Medical Research (W81XMH-06) and the Institute of Arctic Biology. Animals were maintained according to the Animal Care and Use Committee regulations of the University of Alaska Fairbanks.


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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
    Email author
  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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