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

@article{Tien2011HibernationIB,
  title={Hibernation in Black Bears: Independence of Metabolic Suppression from Body Temperature},
  author={{\O}ivind T{\o}ien and John E. Blake and Dale M. Edgar and Dennis A. Grahn and H. Craig Heller and Brian M. Barnes},
  journal={Science},
  year={2011},
  volume={331},
  pages={906 - 909}
}
Black bears hibernate for 5 to 7 months a year and, during this time, do not eat, drink, urinate, or defecate. [] Key Result 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…
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Life on Low Flame in Hibernation
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Through continuous measurement of oxygen consumption, body temperature, and heart, muscle, and brain activities, the authors show that black bears display unusual patterns of metabolic and thermal regulation during hibernation as well as when they emerge from this resting state in the spring.
Thermoregulation and energetics in hibernating black bears: metabolic rate and the mystery of multi-day body temperature cycles
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Black bears overwintering in outdoor hibernacula in Alaska decrease metabolism to as low as 25 % basal rates, while core body temperature (Tb) decreases from 37 to 38 °C to a mid-hibernation average of 33 ° C, and Tb cycling is effected by control of thermoregulatory heat production and may not be present when hibernating bears use passive thermoreGulation.
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It is suggested that pregnant bears maintain homeothermic conditions and supply nutrients to the fetus by stimulating thermogenesis, gluconeogenesis, and urea recycling during hibernation.
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During entrance into torpor, reductions in metabolic rate begin before body temperatures fall, even when thermogenesis is not active, suggesting active mechanisms of metabolic suppression, rather than passive thermal effects.
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The partial depression of circulating FFA with feeding likely explains the incomplete restoration of insulin sensitivity and other metabolic parameters in hibernating bears and provides a highly controlled model to examine the relationship between nutrient availability and metabolism on the hibernation phenotype in bears.
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Mammalian hibernation has intrigued scientists due to extreme variations in normal seasonal physiological homeostasis and molecular pathways of cardiac muscle plasticity reveal differences between the species in the modification of sarcomeric proteins such as titin and α myosin heavy chain during hibernation.
Underground hibernation in a primate
TLDR
The observation that eastern dwarf lemurs also hibernate, though in self-made underground hibernacula is reported for the first time, showing evidence that a clawless primate is able to bury itself below ground.
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