The Bear Necessities

April 6, 2011, 3:04 a.m.
The Bear Necessities
(ANASTASIA YEE/The Stanford Daily)

What do hibernating bears and space travel have in common?

The answer begins in the frigid Arctic with two intrepid Stanford biologists with a penchant for bears. Sleeping bears, to be exact.

Biologists Dennis Grahn and Craig Heller, along with their co-workers, staked out in the Arctic to observe the hibernation patterns of bears. What they found could redefine the way we think about human sleep and its possibilities.

Hibernation–the ability of animals like bears to sleep through the winter while lowering their body temperature and metabolism to avoid the need for food intake–isn’t a novel idea for scientists, yet surprisingly few in-depth hibernation studies have been conducted because of the lack of appropriate technology that can allow researchers to observe their subjects.

Grahn described the crude former approach as one in which “somebody snuck up on a hibernating bear” and took a reading with a thermometer.

Not now.

Grahn, along with biology professor Craig Heller and Brian Barnes, Director of the Institute of Arctic Biology in Alaska, set out to improve upon this old-school research technique by applying recent advancements in telemetry technology to further our knowledge on bears and the details of their hibernation. They published their findings in “Hibernation in Black Bears: Independence of Metabolic Suppression from Body Temperature.”

Grahn and Heller had previous experience studying smaller animals’ hibernation patterns. Building off of Barnes’ access to bears through his work with the Institute of Arctic Biology and a shared interest in studying what constitutes hibernation in a bear, a group of six intrigued researchers initiated a study in Fairbanks, Alaska, utilizing the latest technology.

“We certainly were the first people to use [new telemetry technology] on hibernation in small animals, and, so out of that, questions about bears came up,” Grahn said.

Each experiment lasted six months and studied two black bears at a time. The bears were set up in large crates made to look and feel as comfortable as their dens would be in the wild to allow for a normal hibernation.

The bears were embedded with transmitters that sent radio signals through antennae in the walls of the bears’ hibernation crates. Each bear was equipped through surgery with an electroencephalogram (EEG) to measure brain waves, electrocardiograph (EKG) to measure heart rate and devices for measuring body temperature.

Through their previous work, Barnes and Grahn knew that the body temperatures of small hibernators drop to the temperature of their surrounding environment and back up again in cycles while the animal is asleep. When body temperatures cool, the animals experience a reduction in metabolic rate. However during this fluctuation, the hibernators do not experience REM sleep.

However, the results of these past experiments did not coincide with the researchers’ recent bear study. Bears, unlike other hibernators, do not lower their temperature as much as would be expected given how drastically their metabolism decreases.

As it turns out, Bears actually shiver to keep their body temperatures from dropping too low while they experience both REM and non-REM sleep. Analysis of bears’ brain activity revealed that they remain aware of their surroundings throughout the hibernation period.

“The really interesting thing was the indication that they have a biochemical suppression of metabolism apart from the temperature effect,” Heller said of the findings. “So their temperature only goes down a few degrees but their metabolism goes down by 75 percent, and you can explain that just from the cooling off of the tissues.”

These discoveries about how bears hibernate could potentially be applied to advance human surgical practices, care for stroke or heart attack victims and even space travel, according to Heller.

“If you want to go to Mars, you might as well sleep more,” he said.

Although many of the potential applications are far from being realized and data analysis still stands to be completed on the hibernation studies, the researchers are determined to continue gleaning new knowledge from their research.

However, for Heller, the critical aspect of the experiment was the fact that the subjects “weren’t golden bears.”




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