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…
Life on Low Flame in Hibernation
TLDR
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.
Pregnancy during hibernation in Japanese black bears: effects on body temperature and blood biochemical profiles
TLDR
It is suggested that pregnant bears maintain homeothermic conditions and supply nutrients to the fetus by stimulating thermogenesis, gluconeogenesis, and urea recycling during hibernation.
nergetics of hibernation and reproductive trade-offs in brown bears laudia
Brown bears give birth and nurture their young for the first 3–5 months while fasting in hibernation. During this period, bears use body reserves to support the energy and protein costs of
Metabolic suppression in mammalian hibernation: the role of mitochondria
TLDR
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.
Can offsetting the energetic cost of hibernation restore an active season phenotype in grizzly bears (Ursus arctos horribilis)?
TLDR
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.
Hibernation and seasonal fasting in bears: the energetic costs and consequences for polar bears
TLDR
A significant reduction in productivity is predicted with even modest increases in global warming for polar bears living in the very southern part of their range and are concerned about more northern populations depending on their ability to accumulate increasing amounts of fat.
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.
Effect of body mass on hibernation strategies of woodchucks (Marmota monax).
TLDR
The hibernation-optimization hypothesis is supported by demonstrating the relationship between body mass and characteristics of torpor and contributing toward a fuller understanding of this concept.
Drivers of hibernation in the brown bear
TLDR
Brown bear hibernation was initiated primarily by environmental cues, but terminated by physiological cues, creating the first chronology of both ecological and physiological events from before the start to the end of hibernation in the field.
...
...

References

SHOWING 1-10 OF 34 REFERENCES
BODY SURFACE TEMPERATURE OF HIBERNATING BLACK BEARS MAY BE RELATED TO PERIODIC MUSCLE ACTIVITY
TLDR
It is suggested that bears engage in bouts of muscle activity during the winter denning period that may result in the retention of muscle strength without elevating their core body temperature and without arousing from torpor.
Suppression of Metabolism during Hibernation in Ground Squirrels (Citellus lateralis)
TLDR
Data from 11 ground squirrels indicate that respiratory acidosis occurs during hibernation but that its role may be limited to suppression of thermoregulatory thermogenesis and not suppression of metabolism below basal levels.
Physiology: Hibernation in a tropical primate
TLDR
These findings indicate that arousals are determined by maximum body temperatures and that hypometabolism in hibernating animals is not necessarily coupled to a low body temperature.
Cardiac function adaptations in hibernating grizzly bears (Ursus arctos horribilis)
TLDR
It is proposed that changes in atrial chamber function constitute a major adaptation during hibernation which allows the myocardium to conserve energy, avoid chamber dilation and remain healthy during a period of extremely low heart rates.
Freeze avoidance in a mammal: body temperatures below 0 degree C in an Arctic hibernator.
TLDR
Hibernating arctic ground squirrels were able to adopt and spontaneously arouse from core body temperatures as low as -2.9 degrees C without freezing and plasma sampled from animals with below 0 degree C body temperatures had normal solute concentrations and showed no evidence of containing antifreeze molecules.
Reduction of metabolism during hibernation and daily torpor in mammals and birds: temperature effect or physiological inhibition?
  • F. Geiser
  • Biology
    Journal of Comparative Physiology B
  • 2004
TLDR
Findings show that the reduction in metabolism during torpor of daily heterotherms and large hibernators can be explained largely by temperature effects, whereas a metabolic inhibition in addition to temperature effects may be used by small hibernator to reduce energy expenditure during torpora.
Body temperature patterns during hibernation in a free-living Alaska marmot (Marmota broweri)
TLDR
At least six animals emerged from the hibernaculum suggesting that communal hibernation may be a strategy to reduce metabolic costs while maintaining above-freezing Tb.
CNS regulation of body temperature in euthermic and hibernating marmots (Marmota flaviventris).
TLDR
It is demonstrated that the hypothalamic regulator of Tb is active throughout hibernation and that there are progressive changes in its thermosensitivity.
Effects of ambient temperature on metabolic rate, respiratory quotient, and torpor in an arctic hibernator.
  • C. Buck, B. Barnes
  • Biology, Environmental Science
    American journal of physiology. Regulatory, integrative and comparative physiology
  • 2000
TLDR
This relationship supports the hypothesis that availability of nonlipid metabolic fuels limits torpor duration in hibernating mammals; for T(a) values >0 degrees C, hypotheses linked to body temperature are supported.
Hibernation versus Daily Torpor in Mammals and Birds: Physiological Variables and Classification of Torpor Patterns
TLDR
Comparisons of several physiological variables appear to justify a distinction between the two torpor patterns, but of all variables tested, only the frequency distributions of maximum torpor bout duration and the minimum V̇o2 showed a clear gap between daily heterotherms and hibernators.
...
...