Researchers hope that learning the secrets of hibernation will provide benefits for medicine and space travel
HIBERNATING BLACK bears neither eat nor drink for up to seven months and yet emerge from their winter slumbers almost unchanged. Scientists hope that learning the secret of this feat will allow doctors to put ill patients into suspended animation for later care or help astronauts survive for years in space.
Researchers in Alaska were given an opportunity to study hibernation in a collection of “nuisance bears” found too close to human communities.
It allowed them to monitor breathing, heart rate, temperature and a range of other measures, watching in fine detail what happened while the bears were sleeping. Details of their research were presented yesterday in one of the opening sessions of the American Association for the Advancement of Science’s annual meeting, and are also published this morning in the journal Science. Aside from the discovery that the bears are exceptionally good snorers, the researchers were able to show for the first time that unlike other hibernators, the bears’ body temperature did not fall significantly. Instead it fluctuated between a cool 30 degrees and 36 degrees in a regular week-long cycle. Once body temperature hit the lower figure the bears began to shiver, with the slight muscular activity able to bring body temperature back up to normal.
The team at the Institute of Arctic Biology in the University of Alaska, Fairbanks, and colleagues at Stanford University in California were also able to show that heart rate plummeted, slowing from about 55 beats a minute to just 14. As much as 20 seconds could go by between beats, they said.
Their metabolic rate – the rate at which chemical reactions take place in the cells – also hit the floor, tumbling by 75 per cent compared to summertime activity. This could be what allows the bears (Ursus americanus) to survive all winter neither drinking nor eating, defecating nor urinating.
The researchers found that it took several weeks for the bears’ metabolism to rise to normal levels once they left their wintertime dens. Yet despite this they emerged more or less the same as when they went to sleep, with virtually no muscle or bone loss despite the inactivity.
The researchers, led by Prof Ovind Toien, believe learning how the bears do this could be used to sustain seriously ill patients, greatly increasing the time available to treat them. It could also be used for space travel.