The world's oldest recorded black bear may be living in Minnesota, according a bear researcher with the state’s Department of Natural Resources.

Karen Noyce said the female bear, also known as Bear #56, is 39 years old. Scientists were able to determine her age by examining her teeth.

A cross-section of a tooth shows rings — like the rings found in the cross-section of trees — and those rings are counted to determine the bear’s age.

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Scientists can determine a bear's age by examining a tooth. (Supplied by the Minnesota Department of Natural Resources)

"When we trap a new bear, we pull a tooth from it — a very small tooth behind the canine tooth," she said.

"You decalcify it, cut it into sections and stain it. It's quite accurate in younger bears."

As the animal gets older, however, it gets difficult to distinguish the rings, Noyce noted.

The teeth of female bears also reveal other information.

"Not only can you see how many years old they are, but you also can tell when they have had cubs."

Noyce said the sow gave birth to nearly 30 cubs in 11 litters. She had her first litter when she was five years old and had her last litter when she was 25.       

Beating the odds

The sow was first captured in the Chippewa National Forest in 1981 when she was seven years old. She was outfitted with a tracking collar at that time.

Noyce said it is highly unusual for a bear in the woods to survive so long.

"Most bears die at a very young age in hunted populations," Noyce said. "And in all of our studies since 1980, we've only had a couple of bears live into their 20s."

Researchers have collared more than 500 bears.

"Of about 355 that we've been able to follow to their deaths, 14 have died of natural causes," she said.

"[There were] 10 deaths we could not determine the cause of … and all the others were human-related — mostly hunted."

Noyce said the animal has beaten incredible odds to survive so long.