At 39, a Minnesota black bear has lived longer in wild than any other bear known to researchers
By Sam Cook
Forum News Service
NEAR MARCELL — Karen Noyce set the frequency on her radio-telemetry receiver and pointed its antenna into the old pines of Chippewa National Forest near Marcell Monday morning. The temperature was 2 below zero. The woods were blanketed in new snow.
From the telemetry receiver, Noyce heard high-pitched intermittent chirps.
“That’s her,” said Noyce, a wildlife research biologist with the Minnesota Department of Natural Resources in Grand Rapids.
Somewhere just south of us, the oldest known wild bear in the world —39 years old —rested peacefully in her den. Today she was going to have visitors.
In mukluks and canvas coveralls, Noyce plunged into the snow and began walking south. Along with Dave Garshelis, the DNR’s bear project leader, four of us were bound for the den to see the bear that has defied all the odds.
She hasn’t been hit by a car. She hasn’t been taken by a hunter. She hasn’t been shot by a homeowner for wrecking a deck or a raiding a birdfeeder.
“No known bears of any species have lived longer in the wild, based on age estimates from teeth taken from harvested bears,” Garshelis said. “(That includes) more than 60,000 specimens just in Minnesota and at least one million overall. It’s just incredible that we happened to collar a bear that outlived all those bears.”
Several hundred yards from the road, with the telemetry beeps growing stronger, Noyce paused and peered cautiously at a bulge on a south-facing slope. Now in whisper-mode, Noyce signaled that we should circle around to approach the den from the front.
And, there, under an upturned stump with roots dangling from a 15-by15-inch opening, lay the old girl that biologists call No. 56. In the shadowy depths of the den, No. 56 stirred slowly from her winter lethargy. Her pink tongue licked at the air. Her big head rose in slow motion from where it had rested on her black paws. Her sizeable hulk nearly filled the earthen cavity.
She was unlikely to stir more than that. In hibernation, Garshelis said, bears remain drowsy, their body temperature down from a normal 99 to about 90 degrees, their heartbeats slowed and intermittent. A hibernating bear does not drink, and may go the full six months without urinating or defecating.
We could see, in a mound outside the den, where No. 56 had excavated soil to create her den. She had used her claws to pull dried grass onto the floor of the den to insulate her as she rested. The temperature in the den was likely about 10 to 15 degrees warmer than the ambient air temperature, Garshelis said.
Using a flashlight, Garshelis pointed out the bear’s rump and shoulder and legs, which, to a casual observer, appeared as various lumps of black fur in the dark cavern.
“She’s missing part of her right ear tag,” Garshelis whispered to Noyce. “Her eyes look really glazed.”
Four of us recorded video of No. 56 and took photographs for perhaps half an hour. She huffed lightly at times and did some slow-motion jaw popping, both signs of nervousness, no doubt caused by her inquisitive observers. But she never shifted positions or did more than barely raise her head.
Counting tooth rings
Wildlife biologists know that No. 56 is 39 years old because they counted seven rings in a tooth they extracted from her in 1981, when she was first captured and radio-collared. That reliable aging technique told researchers the bear had been born in 1974, likely during the third week of January.
No. 56 was collared as part of a population dynamics study that examines the density, reproduction and mortality of black bears for management purposes, Garshelis said. She has long outlived her purpose for that study, he said, but researchers continue to track her simply because her longevity is so remarkable.
She’s truly a survivor. Since 1981, the DNR has radio-collared and tracked more than 550 black bears. The next-oldest bear in the agency’s studies included two that reached age 23, one of them a granddaughter of No. 56. Another lived to age 20.
In teeth submitted by hunters from more than 60,000 harvested bears, only three lived past age 30, one of them to age 33, based on annual rings counted in those teeth, according to a 2010 DNR report.
“Half the females in Minnesota don’t live past age 4,” Garshelis said. “Only 5 percent make it to age 15.”
A few bears in zoos have reportedly lived to their mid-40s, he said.
How did No. 56 happen to live so long?
“She has stayed away from houses and hunters’ baits,” Garshelis said, “at least until recently. In the past five years, we’ve made a concerted effort to ask people not to shoot her, even if she does come to a bait.”
Doing her part
No. 56 has done her share to perpetuate her species. Over the years, she produced 11 litters and 28 or 29 cubs. She first gave birth at age 5 and last produced a cub at age 25, Garshelis said.
Researchers have to replace her radio collar about every three years when its batteries wear down. In 2001, when one of her collars was replaced, No. 56 weighed 251 pounds and had 38 percent body fat. In 2010, she weighed 192 pounds, with 19 percent body fat, but her teeth had begun to wear away. Since 2007, she has lost a canine tooth, and several incisors are missing or have receded below the gum line, according to a DNR report. She still had her molars and plenty of grinding surface on them, according to biologists.
DNR researchers take care not to treat one bear differently from another. They assign only numbers, not names to radio-collared bears. But it’s clear that Garshelis and Noyce consider No. 56 something special, if only because they have accumulated so much history with her. They know, for instance, that some hunters have passed her up. One, a young, first-year hunter, captured trail-camera photos of No. 56 before bear season opened a few years ago. When he learned the bear’s identity, he chose not to shoot it, although it would have been legal.
“We were really pleased with that,” Noyce said.
When No. 56 eventually dies, that could occur in any of several ways.
“She could come to a hunter’s bait in low light, and they might not see the collar or ear tags,” Garshelis said. “She could get hit by a car. Her hearing is pretty bad. She could die of natural causes, but if she does, we aren’t going to know what she died from.”
Only 14 of more than 350 radio-collared bears that the DNR tracked until their death have died naturally, Garshelis said.
Still, both he and Noyce know how they would like to see No. 56 go.
“We’re hoping she doesn’t die due to a human cause,” Garshelis said.
They left her den quietly on Monday, leaving only a few boot prints in the snow. Noyce will be back in coming weeks to place trail cameras near the den.
Sometime in late March, those cameras likely will capture images of the world’s oldest known bear in the wild, emerging into another Minnesota spring.
Bear hibernation facts
Here are some facts about bear hibernation from Dave Garshelis, bear project leader for the Minnesota Department of Natural Resources.
– Hibernation defined: A physiological state of greatly depressed metabolism used to conserve energy during extended periods of food scarcity and/or cold. Black bears are considered hibernators.
– Minnesota bears enter dens in September and October. They leave dens in late March to mid-April.
– A bear’s body temperature drops from 99 to 91 degrees Fahrenheit. It drops no lower than that because bears, in their easily accessible dens, must be able to defend themselves against predators.
– Heart rate is reduced from 80 beats per minute to less than 20 beats per minute and is timed with breathing. Gaps between beats last up to 14 seconds.
– Metabolism is reduced to one-fourth of summer levels.
– Bears don’t stand during their entire hibernation but do change body positions. Bears do not arouse during hibernation, but females give birth in January and move around to nurse.
– Before hibernating, bears feed heavily. Fat reserves can reach 50 percent of body mass by time of hibernation, but are more commonly about 33 percent.