Energetics of arousal episodes in hibernating arctic ground squirrels |
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Authors: | Shawna A Karpovich Øivind Tøien C Loren Buck Brian M Barnes |
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Institution: | (1) Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, USA;(2) Alaska Department of Fish and Game, Fairbanks, USA;(3) Biological Sciences Department, University of Alaska Anchorage, Anchorage, USA |
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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 (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. |
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Keywords: | Oxygen consumption Ground squirrel Spermophilus Metabolic rate Arousal Arctic |
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