You Have Been Wrong All These Years: Colorado Bears Don’t Hibernate

Those bears we’re seeing on social media because of their early mischief are waking up after a long winter’s nap, not emerging from hibernation, as you have believed all these years.

Colorado bears don’t hibernate. Instead, they enter a period of “torpor.” It is similar to hibernation but not as deep.

True hibernators such as ground squirrels are almost “frozen” with a greatly reduced body temperature, Colorado Parks and Wildlife’s carnivore and furbearer program manager Mark Vieira explains in an educational video about Colorado bear hibernation.

Bears sleep in torpor, some for more than 100 days. The large mammals, however, experience a very small body temperature drop.

And they can and do awaken.

More Facts About Colorado Bear Hibernation

Fact or Fiction: Bears innately know when winter is coming to hibernate.

Fiction.

Bears don’t prepare to hunker down by temperature. Instead, it’s all about the food. If food is available, they might stay out longer than usual.

Temperature clues help, experts say, but food accessibility drives their torpor timing. And, in some cases, location, as they have been known to make their den closer to humans, including under vacation home decks.

Get our free mobile app

Ultimately, though, they lie down for survival: Their food sources are unavailable. This also explains why bears at the Cheyenne Mountain Zoo and Denver Zoo do not hibernate.

Fact or Fiction: Bears sleep all winter.

Fiction.

Like the “hibernation” misnomer itself, hibernation doesn’t mean sleeping the whole time. It just means bears don’t eat and drink and nor use the facilities, so to speak.

Bears wake up and move around inside their dens, shifting postures and finding warmer positions, according to Sean Farley, a research biologist and bear specialist.

They may even leave their dens, particularly when damage occurs, such as flooding.

Females also wake up from torpor to give birth. And then they go back to sleep.

Fact or Fiction: Bears hunker down in the nearest cave when winter hits.

Fact and fiction.

First, read above about the clues it is time to “hibernate.” Then, after they have foraged their fill, Colorado bears tend to look for rocky areas with a 20% to 40% grade slope, often pulling in pine needles or grass to create a bed – under big rock piles, Vieira says.

According to the National Park Service, bears can also make their dens by digging under the root structure of an overturned tree or entering a hollow tree.

In some environments, they dig a dirt cave for themselves, and snow provides an insulating layer.

Fact or Fiction: Wake up when spring hits.

Fact and fiction.

Colorado bears can start coming out of their dens as early as early March, but they are most active from mid-March to early November/

Moms and cubs come out in later April.

Fact or Fiction: Bears “wake up” hungry.

Fact.

According to Colorado Parks and Wildlife, after losing 20% to 70% of their body weight while wintering in their dens, they emerge and look for food immediately. They need to replace that weight to live a full life during the summer and prepare for next winter’s torpor.

Fact or Fiction: Ball up and play dead if a bear attacks.

Fiction.

Be calm. Talk to the bear and move slowly. If it attacks, fight back, aiming for its head and ears. (Here’s more about protecting yourself from Colorado’s deadliest animals.)