Hibernation in Black Bears: Independence of Metabolic Suppression from Body Temperature

• Published in: Science (American Association for the Advancement of Science) Vol. 331; no. 6019; pp. 906 - 909
• Main Authors: Tøien, Øivind, Blake, John, Edgar, Dale M, Grahn, Dennis A, Heller, H. Craig, Barnes, Brian M
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 18.02.2011; The American Association for the Advancement of Science
• Subjects: Animals; Arrhythmia; Basal Metabolism; Bears; Biological and medical sciences; Black bears; Body Temperature; Brown bears; Climate; Dens; Drinks; Electrocardiography; Energy Metabolism; Female; Fundamental and applied biological sciences. Psychology; Heart Rate; Hibernation; High temperature; Humans; Male; Metabolism; Oxygen Consumption; Reduction; Thermoregulation. Hibernation. Estivation. Ecophysiology and environmental effects; Time Factors; Torpor; Ursidae - metabolism; Ursidae - physiology; Ursus; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Fissipedia; Carnivora; Vertebrata; Mammalia; Hibernation; Body temperature; Ursus americanus; Metabolism
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.1199435

Black bears hibernate for 5 to 7 months a year and, during this time, do not eat, drink, urinate, or defecate. We measured metabolic rate and body temperature in hibernating black bears and found that they suppress metabolism to 25% of basal rates while regulating body temperature from 30° to 36°C, in multiday cycles. Heart rates were reduced from 55 to as few as 9 beats per minute, with profound sinus arrhythmia. After returning to normal body temperature and emerging from dens, bears maintained a reduced metabolic rate for up to 3 weeks. The pronounced reduction and delayed recovery of metabolic rate in hibernating bears suggest that the majority of metabolic suppression during hibernation is independent of lowered body temperature.