Bill Marchel: Let a sleeping bear lie? No way, not with knowledge to be gained

Post date: Mar 8, 2011 2:58:16 PM

Just how black bears survive the hibernation process, and how they are able to do so with minimal physical consequences, is being studied by a team of researchers from the U and Medtronic, in conjunction with the DNR.

By BILL MARCHEL, Special to the Star Tribune

Last update: March 6, 2011 - 2:41 AM

Paul Iaizzo, left, of the University of Minnesota and Medtronic Inc. and Tim Laske of Medtronic monitored various heart functions of a sedated female black bear. Among the goals was to learn more about hibernation.

BRAINERD — Last Thursday, on a snow-covered oak ridge a few miles south of town, a group of onlookers gathered as black bear researchers from the Minnesota DNR and medical professionals from the University of Minnesota and Medtronic Inc. performed a battery of tests on a female black bear.

The bear, roughly 7 or 8 years old, carried a GPS collar adorned with bright pink duct tape. She wore blue and yellow ear tags and was originally collared by the DNR in Camp Ripley. She chose, however, to den just outside the reservation boundaries in what would appear to us to be an unlikely spot. The den was above ground.

The 205-pound female had simply scrapped away a bit of turf beneath the branches of a fallen oak, curled up into a ball and gone to sleep.

A month or so ago, two cubs were born. Exposed the way the hibernating mama bear and cubs were, it's amazing they were able to stave off Old Man Winter.

Initially, the female bear was tranquilized and cubs were passed among various individuals, kept warm by being tucked into partially unzipped jackets. The cubs, the cutest little black balls of fur imaginable, looked on with bright blue eyes, occasionally yawning or bawling out as is they missed Mama. She had been carefully removed from the den and now lay atop a tarp, fully sedated and unaware of her and her cubs' popularity.

The DNR crew did its work first, performing a variety of meticulous measurements and note-taking. Their black bear objectives include mortality sources, range variability, cub production and survival and habitat requirements, among other goals.

Then the team of medical researchers went to work, studying the bear's physiology more closely.

The researchers, led by Paul Iaizzo of the U and Medtronic Visible Heart Laboratory and by Tim Laske, vice president of product development at Medtronic, affixed wires to the bear in various locations for heart ultrasound and EKG tests.

Black bears undergo amazing transformations during their long winter hibernation. Their heart rate and breathing slow dramatically. They do not urinate or defecate. Even during this state of reduction, wounds heal normally. Muscle and bone loss is relatively minimal even though they do not eat or drink.

A human subjected to such conditions would perish.

In December, the medical team had implanted a heart and respiratory monitor under the bear's skin. But the monitor was missing. Somehow the implant was rejected by the bear's immune system. Despite a thorough search of the den site, the implant was not found. A new monitor was implanted.

Implants not rejected by other bears have revealed remarkable data.

During hibernation a black bear's heart rate may be as low as six beats per minute. But when the bear takes a breath -- it takes as few as two per minute -- the heart rate will temporarily speed, helping to circulate oxygen.

How and whether this and other data gathered by the team will ultimately help humans with medical applications has yet to be determined.

Eventually the mama bear was returned to her makeshift den, where she was reunited with her two cubs. Likely she is unaware that as she sleeps away the remaining winter days she is providing data that someday might affect your life and mine.

Bill Marchel, an outdoors columnist and photographer, lives near Brainerd.