The world's oldest-known wild bear has died of old age in northern Minnesota, quietly coming to her final resting place in a shady spot that a bear would find as a good place for a nap, a leading state researcher said Tuesday.

The decomposed corpse of the female American black bear, known to Minnesota Department of Natural Resources researchers as Bear No. 56, was found last Wednesday by state researcher Karen Noyce in the Chippewa National Forest near Marcell. The bear was 39 ½ years old.

The bear was captured and given a radio collar in July 1981 by DNR scientists during the first summer of a long-term research project on bear population ecology. She was 7 years old and accompanied by three female cubs.

During the next 32 years, she and her many offspring provided an almost uninterrupted record of reproduction, survival, movement and, eventually, aging. The DNR says the information from this bear and her offspring has "contributed significantly to the scientific literature on black bear biology."

In the last few years of her life, Bear No. 56 began to visit bait set by hunters, but they abided by a DNR request not to shoot collared bears.

"We're very fond of that bear," Noyce said. "But it's not like a pet or anything, when you have a relationship."

Noyce said her agency was "hoping she'd make it to 40. … She was having trouble getting around but eating normally. She couldn't see and couldn't hear.

"We're glad to see she died a natural death. … It was a good way to go."

First to die of old age

Noyce said this is the first bear in the DNR's study to die of old age. She estimates that the bear died sometime in July.

"She had left her home range … looking for food, apparently," Noyce said. "I was surprised in her state that she would do that. She was just lying in a wooded spot, next to a little bit of a low area, a shady area. It was a kind of place a bear would lay down and take a midday nap."

State researchers will collect the remains soon.

From 1981 to 1995, Bear No. 56 produced eight litters of cubs and successfully reared 21 of the 22 cubs to 18 months of age.

Bear No. 56 outlived all of the 360 other radio-collared black bears that DNR researchers have followed since 1981 — by 19 years. She also outlived any radio-collared bear of any species in the world. Only a few individual study bears have been reported to reach age 30. The second-oldest was a brown bear in Alaska that lived to 34.

"We know most of the people in the world who have radio-tracked bears for a long time," Noyce said, explaining how her profession settled on No. 56 as the world's oldest.

Good luck and good habits

Researchers suspect that Bear No. 56's longevity was a combination of factors, including a home range with few people or major roads, her predisposition to avoid people and general good luck.

When last handled in March 2010, Bear No. 56 was at a healthy weight, but her teeth showed excessive wear and her eyes were clouding. Since then, her hearing and eyesight had deteriorated.

She had been observed more frequently during the past two summers, foraging along trails and traveling dirt roads, which are easier to navigate than the woods.

The average age of a bear killed by a Minnesota hunter is less than 4 years old, and about 80 percent of No. 56's many cubs died by age 6. Of the hundreds of other bears that have been radio-collared and studied by the DNR in 32 years, the longest any survived was 23 years. Some bears in zoos have made it into their 40s, Noyce said.

Paul Walsh • 612-673-4482