Across America, Some Black Bears are No Longer Hibernating During Winter

by Jon D. B.

As the climate continues to warm and black bears further habituate to human food sources, some are no longer hibernating through the winter.

“We’re tampering with Mother Nature,” offers Ann Bryant, leader of California’s Tahoe area BEAR League. “Just in the 25 years that I’ve had serious eyes on [black bears], 24/7, I’ve seen enormous changes in bear behavior based on human activity and it’s pretty frightening.”

After two-and-a-half decades monitoring Tahoe black bears, Bryant’s great worry is evident in her words. The problem she cites is a new one. It is wholly modern. And the rate of change is becoming more and more rapid.

When Bryant first began her work with California black bears, boars and sows would enter hyperphagia, then a torpor state leading to hibernation in November. Then, as West Coast bears had for millennia, they wouldn’t emerge again until April or as late as May.

In recent years, however, Bryant tells SF Gate this “window of hibernation” has shortened on both ends. Local bears don’t hibernate until late December. And now they’re emerging from their dens well before spring.

Perhaps most concerning of all, she says about 20% of Tahoe’s black bears aren’t hibernating at all.

“What I think is happening in Tahoe is human interference in providing unnatural food sources year-round.” – Ann Bryant, BEAR League

According to Bryant and many of her CA colleagues, human interference is to blame. And it’s the same story across America.

A black bear looks up from stairs leading down to an apartment in downtown Aspen. A high number of bears are in the town of Aspen as they hunt for food in resident’s trash. The bear are keeping local police busy with dozens of calls each night. RJ Sangosti/ The Denver Post (Photo By RJ Sangosti/The Denver Post via Getty Images)

“It’s not good. It’s not normal. And it’s not natural,” she continues. “Once they don’t go in [to hibernation], then they have to continue eating. So they’re just maniacally driven to find food year-round and that puts a lot of pressure on them. It tampers on their biological systems. It’s not good.”

California Department of Fish and Wildlife (CDFW) agrees. “In Lake Tahoe, especially, we notice that not all bears hibernate,” adds CDFW spokesperson Peter Tira. 

Human food sources, like bird feeders, pet foods, and especially garbage and food waste, have become so plentiful that bears no longer need to hibernate through winter. Typically, bears do so in order to “wait out” the winter’s dead-zone of little-to-no available food sources in nature.

But as the climate continues to warm and human settlements expand, winter is no longer a dead-zone.

“With access to year-round food and alternative food sources, the body may not trigger them to go into that deep sleep,” Tira continues. “They’ll just skip it altogether.”

“It’s blatant and it’s very, very worrisome,” Bryant decrees. “What are we doing? What are we doing to our bears? And what are we doing to our planet? How will both of these things endure? These are just the tiny things I’m witnessing. What else is going on?”

Some East Coast Black Bears Aren’t Hibernating, Either

While working on Outsider’s National Parks Journal this March, speaking to Great Smoky Mountains National Park’s (GRSM) lead wildlife biologist and black bear expert, Bill Stiver, reveals the same for East Coast bears, too.

“It’s no longer unusual to have a bear sighting here or there during the course of the winter,” Stiver begins. ” I got a call maybe a week or so ago that a bear was laying out and sunning itself.”

In Stiver’s GRSM case, however, the bear did eventually go back into its den. “But we now get calls concerning black bears in the winter. It’s not a big issue for us, though. Down in Florida, however, it’s a big concern.”

And the more black bears remain active, the more human-bear conflicts rise; something Stiver spearheads for GRSM. His studies have found a steady increase in human-bear conflicts in the past decades, as well. This is also due to a population boom for black bears across most of America. But this population increase, too, is due to food availability and a warming climate (a big factor in Florida’s non-hibernating bears). It’s all directly connected to us.

Perhaps the most plainly-stated fallout of these changes came from an extensive 2017 study published by the British Ecological Study (BES). Analyzing black bears in the U.S., the report defines hibernation as “a state of inactivity that enables animals to conserve energy during seasonal food shortages or severe weather… A need that may decline in response to changing environmental conditions.”

BES’ study holds the same conclusions as Bill Stiver’s GRSM work, too. All of the above leads to a great increase in human-bear conflicts. For us humans, the fallout ranges from property damage to public safety concerns.

But for black bears, the result is “high mortality.”

And unfortunately, BEAR League’s Ann Bryant sees no signs of these changes slowing. “It’s ongoing, ongoing. It’s inadvertent or deliberate feeding of bears.”

For information on how to live in or travel bear country responsibly, visit out National Parks Journal series next.