Where Do Grizzlies Go in Winter? Inside Yellowstone’s Bear Denning Season

As the temperatures drop and snow begins to cover the valleys of Yellowstone and Grand Teton National Parks, one question comes to mind: where do all the grizzly bears go?

After spending the warmer months searching for food, raising cubs, and roaming the landscape, grizzlies begin preparing for one of the most important seasons of the year. Winter denning is a remarkable part of their annual cycle, and there’s a lot more happening than simply finding a place to sleep!

When Do Grizzly Bears Go Into Their Dens?

Grizzly bears don't all disappear at once. The timing depends on the individual bear, whether a female is expecting cubs, and the conditions of the season.

In the Greater Yellowstone Ecosystem, some bears begin entering their dens as early as September or October, while others remain active into November or December. Pregnant females generally den earlier than males and other females.

Before settling in, grizzlies enter a period called hyperphagia. This is when bears spend much of their time eating and building up the fat reserves they'll rely on throughout the winter. During this period, a bear can gain several pounds in a single day!

Fall is an important time for wildlife viewing in Yellowstone because bears are particularly focused on finding food. If you'd like to learn more about what else is happening across the parks during this season, check out our guide to fall wildlife in Yellowstone and Grand Teton.

What Does a Grizzly Bear Den Look Like?

Forget the idea of a cozy cave with a big entrance. Most grizzly bears in the Greater Yellowstone Ecosystem dig their own dens, often on sloped hillsides where the surrounding terrain and snow help insulate them from the cold.

Many dens are dug into sandy soil on north-facing slopes, where drifting snow provides an extra layer of insulation. Bears typically create a small entrance, a short tunnel, and a chamber just large enough to settle into.

And here's an incredible fact: excavating a den can take just three to seven days, and a bear may move up to one ton of soil in the process!

Some bears occasionally reuse natural shelters or existing dens, but most excavated dens collapse over time as snow melts and spring runoff moves through the soil.

You can learn more about the science behind bear dens in the National Park Service's Bear Ecology guide.

Do Grizzly Bears Really Hibernate All Winter?

Yes, but bear hibernation isn't quite the same as the deep hibernation we see in some smaller mammals.

During winter denning, a grizzly's heart rate and breathing slow considerably, and its body uses stored fat to supply energy. Unlike many small hibernating animals, bears don't need to lower their body temperature dramatically to conserve energy.

They generally don't eat, drink, urinate, or defecate during this period. Their bodies have an extraordinary ability to recycle waste products and preserve muscle tissue while relying on stored fat.

Even more fascinating? Bears can sometimes wake up or leave their dens during winter. Denning isn't necessarily one uninterrupted stretch of sleep.

Researchers have studied this seasonal behavior for decades. The U.S. Geological Survey's research on grizzly bear denning chronology and movements in the Greater Yellowstone Ecosystem provides a closer look at when bears enter and emerge from their dens.

What Happens to Grizzly Cubs During Winter?

Winter is also the season when an extraordinary event takes place inside a female grizzly's den: cubs are born.

Pregnant females give birth during the winter, typically in January or February. Newborn cubs are tiny compared with the adults they'll eventually become, and they depend entirely on their mother for warmth, protection, and milk.

The mother remains in the den with her cubs while they grow. By the time spring arrives, the cubs are ready to begin exploring the world alongside her.

This is one reason female grizzlies with newborn cubs often emerge later than males. Their winter denning period is longer, giving their young time to develop before venturing into the landscape.

When Do Grizzlies Come Out of Their Dens?

As winter begins to loosen its grip, grizzlies gradually return to the landscape.

In the Greater Yellowstone Ecosystem, some males emerge as early as February, while many females emerge later in March or April. Females with newborn cubs may remain in their dens into April or early May.

Once they're out, bears begin searching for food. Early spring meals can include winter-killed animals, grasses, roots, and other vegetation as it becomes available.

Spring is also an exciting time for wildlife watchers. In fact, we recently shared what it's like when the first bears begin appearing on the landscape in our spring update on grizzlies waking up from hibernation.

From the first spring sightings to the last bears preparing for winter, every season brings a different glimpse into the lives of Yellowstone's wildlife.

Can You See Grizzlies in Yellowstone During Winter?

Winter wildlife viewing looks different from the busy summer season. Snow-covered landscapes, changing road access, and seasonal wildlife movements all influence what visitors can experience. 

Wildlife viewing in Jackson Hole is AMAZING in the Winter!  As the temperatures drop, snow falls and bears retreat to their dens to hibernate; many species move to lower elevations, and sightings become more common. Elk, moose, bighorn sheep, and wolves congregate in the valleys, making for incredible wildlife encounters amidst beautiful, snowy landscapes. Our guides will take guests on an incredible winter adventure through the open areas of Grand Teton National Park and the National Elk Refuge. 

At Yellowstone Day Tours, we love helping visitors understand not just what they're seeing, but the remarkable behaviors behind it. From grizzlies preparing for winter to mothers introducing their cubs to the world in spring, these seasonal changes are part of what makes Yellowstone so special.

Every visit offers something different, and there's always more to discover in America's first national park.