Energetics of arousal episodes in hibernating arctic ground squirrels

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Vol. 179; no. 6; pp. 691 - 700
• Main Authors: Karpovich, Shawna A., Tøien, Øivind, Buck, C. Loren, Barnes, Brian M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.08.2009; Springer Nature B.V
• Subjects: Activity Cycles; Alaska; Ambient temperature; Animal Physiology; Animals; Arousal - physiology; Biochemistry; Biomedical and Life Sciences; Biomedicine; Body Temperature; Carbon dioxide; Carbon Dioxide - physiology; Cold Temperature; Costs; Energy Metabolism - physiology; Female; Hibernation; Hibernation - physiology; Human Physiology; Implants, Experimental; Life Sciences; Male; Metabolism; Motor Activity; Original Paper; Overwintering; Oxygen; Oxygen consumption; Oxygen Consumption - physiology; Random Allocation; Rodents; Sciuridae - physiology; Signal Processing, Computer-Assisted; Soil temperature; Zoology; Alaska; United States > US; Arctic region; Metabolic rate; Oxygen consumption; Arctic; Arousal; Ground squirrel
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s00360-009-0350-8

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.