Ursus arctos horribilis is better known by the more casual term of grizzly bear. These massive, brown-haired predators have a reputation as one of nature’s most formidable killing machines. Up to 8 feet from nose to tail and weighing up to 800 pounds, these fierce animals have captivated—and terrified—humans for centuries. Keep a safe distance and read about their love for munching moths, eating smaller bears, and being polar-curious.
1. Grizzly bears are actually pretty light eaters.
Grizzlies—a subspecies of brown bear (Ursos arctos) native to North America—are strong enough to make a meal out of whatever they like, including moose, elk, and bison. Despite their reputation for having only carnivorous appetites, their diet also consists of nuts, berries, fruits, and leaves. They’ll even eat mice. The gluttony doesn’t kick in until they begin to exhibit hyperphagia, a phase of preparing for winter hibernation by chomping down enough food to gain up to three pounds a day.
2. Grizzlies use "CPR" to get at your food.
More than 700 grizzlies live in or near Yellowstone National Park, which forces officials to constantly monitor how park visitors and the bears can peacefully co-exist. Because bears rummaging in food containers can lead to human-bear conflict, the park’s Grizzly & Wolf Discovery Center tests trash cans and coolers to see if they’re bear-resistant. (Nothing is truly bear-proof.) Often, a bear will use “CPR": jumping on a canister with its front legs to make the lid pop off, similar in appearance to a person giving someone CPR. Containers that can last at least 60 minutes before being opened can be advertised by their manufacturers as being appropriate for bear-inhabited environments.
3. Grizzly bears can climb trees.
It's a myth that grizzlies can't climb trees. Though their weight and long claws make climbing difficult, and they need support from evenly spaced branches, grizzlies can travel vertically if they choose to.
4. They'll eat other bears.
In addition to being omnivorous, grizzlies can also be classified as cannibals. They’ve been spotted eating the carcasses of black bears in Canada. Officials at Banff National Park in Alberta said the grizzlies are “opportunistic” and more than willing to devour black bears—sometimes just one-fifth their size—if the occasion calls for it. And it’s not just black bears: One study on bear eating habits published in 2017 recorded a 10-year-old male eating a 6-year-old female brown bear.
5. They love moths.
Although grizzlies enjoy eating many insects, moths are at the top of their menu. Researchers have observed that bears are willing to climb to alpine heights at Montana’s Glacier National Park to feast on the flying appetizers. Grizzlies will turn over rocks and spend up to 14 hours in a day devouring an excess of 40,000 moths.
6. A pair of grizzly bears once lived on the White House grounds.
In what would be considered an ill-advised decision today, explorer Zebulon Pike decided to give his friend President Thomas Jefferson two grizzly cubs in 1807. Jefferson reluctantly accepted them and kept them in a cage near the north entrance to the White House, and later re-gifted the cubs to museum operator Charles Willson Peale. Sadly, one of the cubs was shot after getting too aggressive with Peale’s family.
7. Grizzlies can run faster than Usain Bolt.
The bears we see in fiction or lazing about in the wild tend to look cumbersome and slow, as most anything weighing a half-ton would. But in a land race, even Olympic champions would be on the losing end. Grizzlies can reportedly run 35 mph, and sustain speeds of up to 28 mph for two miles, faster than Usain Bolt’s 27.78 mph stride (which he can only sustain for a few seconds).
8. They can mate with polar bears.
In parts of Alaska and Canada where grizzly and polar bear ranges overlap, there are sometimes rare sightings of what observers call “grolar bears” or “pizzlies.” With large heads and light-colored fur, they’re a hybrid superbear birthed from some interspecies mating. Typically, it’s male grizzlies who roam into those territories, finding female polar bears to cozy up with. Researchers believe climate change is one reason the two are getting together.
9. Grizzly bears know how to cover their tracks.
When it comes to intelligence, grizzlies may not get the same publicity that birds and whales do, but they’re still pretty clever. The bears can remember hotspots for food even if it’s been 10 years since they last visited the area; some have been observed covering tracks or obscuring themselves with rocks and trees to avoid detection by hunters.
10. Grizzlies aren't out of the woods yet.
For 42 years, grizzlies at Yellowstone occupied the endangered species list. That ended in 2017, when the U.S. Fish and Wildlife Service declared that a rise in numbers—from 150 in the 1970s to more than 700 today—meant that conservation efforts had been successful. The move was controversial and opposed by conservationists and many Native American tribes. And overall, the grizzly population is still listed as threatened. Conservationists estimate that fewer than 2000 grizzlies remain in the lower 48 states, down from 50,000 two centuries ago.
A version of this article ran in 2018; it has been updated for 2022.