Do You Need to Worry About Bears in Winter?

In summer, bear country comes with familiar rules: carry bear spray, store food in bear canisters, and know how to handle an encounter. But should you worry about bears in winter? Do bears attack more often when the snow is down? The research turned up a few things that may surprise you.

Are bears active in winter? Depending on the time of year, type of bear, and location, bears may be active during winter. In some locations, bears are active year-round, while bears in other locations are not.

Do bears really hibernate or not?

Most people assume bears hibernate the way a ground squirrel does. The science says it's more interesting than that, and bears aren't typical hibernators.

Bears go into a winter state of torpor, which is a more active form of hibernation but not the textbook version. Their body temperature doesn't drop as low as it does in smaller mammals that hibernate, and that gap is what causes so much confusion about what "hibernation" actually means. If you want the general background on the terms, Wikipedia's hibernation article covers the basics.

Bears are now often classed as hibernators, sometimes called "super hibernators". What researchers have learned about them has changed how biologists define hibernation in the first place.

New knowledge of hibernation processes has led biologists to redefine mammalian hibernation simply as specialized, seasonal reduction of metabolism in response to the concurrent pressures of food unavailability and low environmental temperatures.

Bear Center Conducts Hibernation Study by Lynn Rogers

Here's the part that still amazes me. Smaller hibernators have to wake every few days and warm their bodies up to urinate and defecate. Bears do not. They can sleep for months without eating, drinking, urinating, or defecating, and they essentially recycle their own waste.

The catch for anyone heading outdoors is that not all bears hibernate, and those that do don't all hibernate for the same length of time. That variation is what decides whether you might actually meet one in January.

How long do bears hibernate for?

We are still learning a lot about bears. Researchers have studied various bears and how long they stay denned in different locations, and the results differ more than most people expect.

Check out the chart below to see how long bears hibernate in different states (source).

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In general, the further south, the less time bears spend hibernating. There are sometimes other factors that come into play, and there are exceptions. Treat the chart as a pattern, not a promise.

Black bear hibernation becomes much more complex in southern regions. Weather, food availability and vegetation could all play a part, but nobody knows for sure.

The relative roles that food availability, weather, physical condition, functional adaptation to local climate, and evolved physiology play in this behavior remain a matter of speculation.

DAVID M. GRABER, National Park Service

That honest admission of uncertainty is worth remembering. If the people who study this can't pin down why a southern bear stays up, you shouldn't assume a bear in warm country is asleep just because the calendar says winter.

Where bears in winter stay active

In some regions, bears can be active during winter. In Arizona, for example, it's been reported that bears are sometimes active on warm days. In Southern California and Virginia, bears have been known to be active all winter (source).

The logic is simple. Torpor is a response to two pressures at once: no food and cold temperatures. Where food stays available or mild spells keep returning, the pressure eases and bears have less reason to shut down for long.

In spring, bears in North America typically wake from hibernation near the beginning of April, and as early as mid-March. But in lower climates or unusually warm winters, bears can wake as soon as January or February.

For planning, that means "winter" is not a safe window by default. A shoulder-season trip, a warm snap, or a low-elevation route can all put you in country where a bear is awake and hungry. Our piece on when shoulder season becomes winter covers how to notice that shift in time.

Do bears attack in winter?

If bears are active, it's possible they may attack in winter, though bear attacks are rare and bear attacks in winter are even rarer.

Bear attacks are a lot less of a worry compared with other outdoor risks, and their danger is probably exaggerated, by a lot.

While it may be argued that human beings have an innate fear of bears, much of our reaction is based on myth, ignorance, exaggeration, and sensationalism.

Timothy Floyd, MD, FACS - Bear-inflicted human injury and fatality

During winter, there are a lot more dangers to worry about than bears: cold, wet clothing, short days, and poor route choices among them. By the numbers, about 10 bear injuries happen per year, with 1 death, but it's still a good idea to stay alert.

And just because a bear is denning for the winter doesn't mean it isn't aware of its surroundings. Skiers, snowboarders, and hikers could unknowingly pass by a bear den and alert a bear, causing it to wake and defend itself.

Bears usually den in rock cavities, brush piles, and hollow trees, which makes them harder to notice. Under snow, a den entrance can be close to invisible, so the practical rule is to keep your distance from anything that looks like a sheltered hollow.

Bears encountered suddenly are the primary reason for attacks. Studies of bear attacks in Yellowstone National Park found that 99% of injuries from bears resulted from sudden encounters.

And it's not just hikers who need to be alert. Snowboarders and skiers in the mountains around March and April can come across bears as they begin to emerge from their winter sleep.

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Why bear attacks happen

The likelihood of an attack depends on the situation, the type of bear, and the sex of the bear.

In most instances, black bears will run away when encountered.

A bear's reaction to a sudden encounter with human beings depends on the bear's species and sex. Black bears of both sexes, including females with cubs, generally run away from humans as soon as the latter are detected.

Timothy Floyd, MD, FACS - Bear-inflicted human injury and fatality

A brown bear with cubs is a different story, because mothers will aggressively attack intruders. Studies show 70-80% of all brown bear encounters occur with females with cubs (source).

Look at the data further and there are more black bear attacks than brown bear attacks, even though brown bears are the more aggressive of the two. The reason is numbers: there are simply more black bears than brown bears.

The two most common reasons bears attack are sudden encounters and provocation.

Sudden encounters happen when a bear doesn't realize you're there until you are close by. This happens more often with backcountry hikers, particularly in thick brush, near loud water, or in wind that carries your scent away. A good rule of thumb is to stay on established roads and trails, where bears expect traffic.

Provocation can happen innocently enough. There have been unfortunate events where photographers were killed by bears after getting too close. It's advised that hikers stay at least a quarter mile away from bears. For the sound side of this, see our look at whether a whistle will scare a bear.

Bear safety tips for winter trips

If you're camping or hiking in the winter, it's still a good idea to practice good bear safety. There are a lot of other animals to look out for besides bears, such as raccoons, coyotes, and small rodents.

Here are some general tips for bear safety in winter:

• Carry bear spray (like this brand), not just for bears, but other animals too. Keep in mind, spray range is reduced in cold weather.
• Use a bear canister in areas with bear activity.
• Bear bag or lock up your food. Bear bagging is the practice of hanging your food from a tree.
• In Alaska, foghorns seem to have eliminated bear encounters.
• Bear bells may work, though there are conflicting opinions about their effectiveness and dangers.
• Watch the ground and trees for bear activity, such as tracks and fresh scat.
• Keep campsites clean and food stored in airtight storage containers outside of tents
• Travel in groups. Bear attacks are drastically reduced when hiking in numbers.

Food storage is where most winter campers slip. Cold makes people lazy about it, because frozen food seems like it can't smell. It can, and a hungry bear in a mild spell will still investigate. Our ranking of bear canisters and our notes on keeping food from freezing are worth reading together. If your route runs through Alaska, bear safety in Alaska goes deeper.

The best tip for dealing with bears is to call the local agencies and ask. Speaking with experienced staff will tell you about bear activity in the area and other dangers to look out for. The National Park Service and Parks Canada both publish park-level conditions and bear information.

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Do you need bear spray in winter?

A question hikers often ask is whether they need to carry bear spray in winter, and whether it will actually work in the cold.

If you're hiking in the backcountry, it might not be a bad idea to carry it. In my view it's cheap insurance, especially since there are many other animals, like cougars and elk, who can attack humans. One very popular brand is SABRE. Check out SABRE Bear Spray on Amazon.

Bear spray will work in the cold. It does not freeze, but its effectiveness (spray range) will be reduced, particularly around freezing temperatures. Cold lowers the pressure in the canister, which is why range suffers. In cold weather, it's best to carry your bear spray close to your body inside your winter layers to help keep it warm.

Carry it where you can reach it with a gloved hand, not buried in a pack. A canister you can't grab quickly is no use in a sudden encounter, and sudden encounters are exactly what causes most attacks. Bulky mitts make this harder than people expect, so practise the draw before you need it, and see our picks of the best gloves for winter camping if your current pair is clumsy.

One handy tip for travelers who can't carry bear spray on planes: call local hotels and outdoor stores and ask whether you can buy left-behind bear spray cheaply. Visitors often know they can't fly with it, so they leave it behind. Check that the canister is in date and undamaged before you rely on it.

Whether the ground is white or green, the habits are the same. For the wider picture of cold-season trips, our guide to winter hiking and camping is a good next stop.