Black bears could hold a secret that could take people to the stars, say researchers who have for the first time examined their hibernation patterns in detail.
The Alaska Department of Fish and Game has found, surprisingly, that although black bears only reduce their body temperatures slightly during hibernation, their metabolic activity drops dramatically, slowing by about three-quarters.
This was unexpected, as generally metabolism slows by about 50 percent for each 10 degree Celsius drop in body temperature.
In addition, the black bears' metabolism remained significantly suppressed for several weeks after waking.
Øivind Tøien and a group from the Institute of Arctic Biology at the University of Alaska Fairbanks, along with colleagues from Stanford University, implanted radio transmitters into each bear to record its body temperature, heart beats and muscle activity. The bears were kept in structures mimicking dens, away from human disturbance, and monitored via infrared cameras.
"We measured the bears' metabolism by continuously measuring the oxygen and carbon dioxide concentrations of the air entering and leaving the den. The transmitters inside each bear told us that the bear's body temperature was not stable, but varied over the winter in slow cycles each lasting several days," says Tøien.
"Such large, multi-day fluctuations in core body temperature are unlike those observed in any other mammal before. This detail was missed by past studies, and may have caused overestimation of metabolic rate because bears periodically shiver when they increase their body temperature," Tøien said.
Since some form of hibernation has been observed in nine orders of mammals, says the team, it's likely that the genetic basis for this ability is ancient and widespread - and could perhaps be exploited in humans.
One prime example, says Tøien , is the possibility of inducing hibernation in human beings, making deep space travel more feasible.
"We simply need to learn how to turn things on and off to induce states that take advantage of the different levels of hibernation," he says.
And, says Brian Barnes, senior author of the study, there are important medical implications too.
"If we could discover the genetic and molecular basis for this protection, and for the mechanisms that underlie the reduction in metabolic demand, there is the possibility that we could derive new therapies and medicines to use on humans to prevent osteoporosis, disuse atrophy of muscle, or even to place injured people in a type of suspended or reduced animation until they can be delivered to advanced medical care – extending the golden hour to a golden day or a golden week," he says.