For the past month or so, lethargic black bears across North America have been shaking off their sleep to sniff out the fresh offerings of spring. But Timber and Thorn, a couple of young rescue bears at the Oregon Zoo, have taken it to a whole new level.

On a mild, sunny day in their Black Bear Ridge habitat, the pair took their first dip of the season, and they didn’t hold back — joyfully splashing around in sturdy 300-gallon tub that caregivers had filled with water, playfully sparring with each other and soaking up the sun.

Orphaned in Alaska and too young to survive on their own, the bears were rescued by state wildlife officials in 2023 and taken to the Alaska Zoo in Anchorage for care before coming to Portland. Care staff named the cubs in honor of their forest home and Portland’s major league soccer teams, the Timbers and Thorns.

“They go into torpor in the fall and become more active again in early spring,” said Sarah Plouff, a keeper in the zoo’s Great Northwest area. “They’re playing more now, and their appetites have increased.”

Though most bears experience some form of winter slumber, wildlife biologists say it is not a true hibernation. Unlike bats, woodchucks or the notorious Arctic ground squirrel — which turns nearly frozen and whose brain cells shrink during dormancy — bears’ body temperatures don’t drop so low.

“Their metabolism only falls by half compared to the other mammals,” said Steph Horner, director and president of the American Bear Association.

The reason for this, she explains, stems from the fact that bears’ brains are much more alert throughout torpor.

“During a warm winter especially, bears wake up and move about the den,” she said. “They may even leave in search of food. It’s more like a long, broken nap.”

With black bears particularly, nap length can vary geographically. In the north — where berries, plants and bug larvae die in winter weather — torpor may last around seven months. But where it’s warm and food is abundant year-round, bears may bypass hibernation all together. Here in temperate Oregon, black bear torpor generally lasts five or six months.

To mirror natural conditions, the animal-care team at the zoo reduces the black bears’ winter diets significantly, then ramps them back up for spring.

Black bears are North America’s most common bear species — about 25,000 to 30,000 live in Oregon. Once abundant in nearly all of North America’s forested regions, black bears have lost much of their habitat and were extirpated from great swaths of their former range. But populations have been bouncing back over the past two decades: 60% of U.S. and Canadian states and provinces report growing numbers, according to the International Union for Conservation of Nature, which lists the bears’ current population trend as “increasing.”

Source: Oregon Zoo

Tanner, Laura, & Casey