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Joe Raedle, Getty Images

10 Things You Might Not Know About Grizzly Bears

Joe Raedle, Getty Images
Joe Raedle, Getty Images

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. Standing up to 8 feet tall and weighing 800 pounds, these fierce mammals have captivated—and frightened—humans for centuries. Keep your distance and read up on these facts about their love for munching moths, eating smaller bears, and being polar-curious.

1. THEY’RE ACTUALLY PRETTY LIGHT EATERS.

Grizzlies—more accurately, North American brown bears—are strong enough to make a meal out of whatever they like, including moose, elk, and bison. Despite their reputation for having 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, preparing for winter hibernation by chomping down enough food to gain up to three pounds a day.

2. THEY USE “CPR” TO GET AT YOUR FOOD.

A grizzly bear eats fruit in Madrid, Spain
Dani Pozo, AFP/Getty Images

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 unwanted encounters, 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,” or jumping on a canister with its front legs, in order to make the lid pop off. 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. THEY CAN CLIMB TREES.

It's a myth that grizzlies can't climb trees. Though their weight and long claws make climbing difficult [PDF], and they need support from evenly-spaced branches, grizzlies can travel vertically if they choose to.

4. THEY’LL EAT OTHER BEARS.

Two grizzly bears play in a pool at a zoo in France
Jean-Francois Monier, AFP/Getty Images

In addition to being omnivorous, grizzlies can also be classified as cannibals. They’ve been spotted eating the carcasses of black bears in Canada. Calling it a “bear-eat-bear world,” 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 the menu. Researchers have observed that bears are willing to climb to alpine heights at Montana’s Glacier National Park in order to feast on the flying appetizers. Grizzlies will turn over rocks and spend up to 14 hours in a day devouring in excess of 40,000 moths.

6. A PAIR OF THEM ONCE LIVED ON WHITE HOUSE GROUNDS.

A grizzly bear appears at the Wild Animal Sanctuary in Keenseburg, Colorado
John Moore, Getty Images

In what would be considered an ill-advised decision, explorer Zebulon Pike decided to gift his friend President Thomas Jefferson with 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 them got shot after getting too aggressive with Peale’s family.

7. THEY 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 nearly 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 miles per hour stride (which he can only sustain for a few seconds).

8. THEY MATE WITH POLAR BEARS.

A grizzly bear is shown swimming at a pool in an Illinois zoo
Scott Olson, Getty Images

In parts of Alaska and Canada where grizzlies and polar bears converge, 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. THEY KNOW HOW TO COVER THEIR TRACKS.

When it comes to intellect, grizzlies may not get all 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. THEY’RE NOT OUT OF THE WOODS YET.

A grizzly bear and her cub walk in Yellowstone National Park
Karen Bleier, AFP/Getty Images

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. But overall, the grizzly population is still struggling: Fewer than 2000 remain in the lower 48 states, down from 50,000 two centuries ago.

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Animals
14 Bold Facts About Bald Eagles
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Bald eagles are powerful symbols of America—but there’s a whole lot more to these quirky birds.

1. YOUNG BALD EAGLES AREN'T BALD.

A young bald eagle with a brown head on a beach.
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So obviously adult bald eagles aren't really bald, either—their heads have bright white plumage that contrasts with their dark body feathers, giving them a "bald" look. But young bald eagles have mostly brown heads. In fact, for the first four or five years of their lives, they move through a complicated series of different plumage patterns; in their second year, for instance, they have white bellies.

2. BALD EAGLES SOUND SO SILLY THAT HOLLYWOOD DUBS OVER THEIR VOICES.

A red-tailed hawk.
A red-tailed hawk's screech is usually dubbed over the bald eagle's weaker scream.
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It's a scene you’ve probably seen countless times in movies and on TV: an eagle flies overhead and emits a rough, piercing scream. It's a classic symbol of wilderness and adventure. The only problem? Bald eagles don't make that sound.

Instead, they emit a sort of high-pitched giggle or a weak scream. These noises are so unimpressive that Hollywood sound editors often dub over bald eagle calls with far more impressive sounds: the piercing, earthy screams of a smaller bird, the red-tailed hawk. If you were a fan of The Colbert Report, you might remember the show's iconic CGI eagle from the opener—it, too, is making that red-tailed hawk cry. Listen for yourself and decide who sounds more impressive.

3. THEY EAT TRASH AND STOLEN FOOD.

Two bald eagles guard their prey against two magpies on a snowy field.
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Picture a majestic bald eagle swooping low over a lake and catching a fish in its powerful claws. Yes, bald eagles eat a lot of fish—but they don't always catch it themselves. They've perfected the art of stealing fish from other birds such as ospreys, chasing them down until they drop their prey.

Bald eagles will also snack on gulls, ducks, rabbits, crabs, amphibians, and more. They'll scavenge in dumpsters, feed on waste from fish processing plants, and even gorge on carrion (dead, decaying animals).

4. BALD EAGLES USUALLY MATE FOR LIFE.

Two bald eagles perched on a tree.
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Trash and carrion aside, they're pretty romantic animals. Bald eagles tend to pair up for life, and they share parenting duties: the male and the female take turns incubating the eggs, and they both feed their young.

5. … AND THEY LIVE PRETTY LONG LIVES.

Two bald eagles sitting on a rock.
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Those romantic partnerships are even more impressive because bald eagles can survive for decades. In 2015, a wild eagle in Henrietta, New York, died at the record age of 38. Considering that these birds pair up at 4 or 5 years of age, that's a lot of Valentine's Days.

6. THEY HOLD THE RECORD FOR THE LARGEST BIRD'S NEST.

Two bald eagles in their large nest.
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Bald eagles build enormous nests high in the treetops. The male and female work on the nest together, and this quality time helps them cement their lifelong bond. Their cozy nurseries consist of a framework of sticks lined with softer stuff such as grass and feathers. If the nest serves them well during the breeding season, they'll keep using it year after year. And, like all homeowners, they can't resist the thought of renovating and adding to their abode. Every year, they'll spruce it up with a whopping foot or two of new material.

On average, bald eagle nests are 2-4 feet deep and 4-5 feet wide. But one pair of eagles near St. Petersburg, Florida, earned the Guinness World Record for largest bird’s nest: 20 feet deep and 9.5 feet wide. The nest weighed over two tons.

7. FEMALES ARE LARGER THAN MALES.

Two bald eagles in their large nest.
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In many animal species, males are (on average) larger than females. Male gorillas, for example, dwarf their female counterparts. But for most birds of prey, it's the opposite. Male bald eagles weight about 25 percent less than females.

Scientists aren't sure why there's such a size difference. One reason might be the way they divide up their nesting duties. Females take the lead in arranging the nesting material, so being bigger might help them take charge. Also, they spend longer incubating the eggs than males, so their size could intimidate would-be egg thieves.

If you're trying to tell male and female eagles apart, this size difference may help you—especially since both sexes have the same plumage patterns.

8. TO IDENTIFY THEM, LOOK AT THE WINGS.

A bald eagle flies across the water.
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People often get excited about a big soaring bird and yell "It's an eagle!” just before it swoops closer and … oops, it's a vulture. Here's a handy identification tip. Bald eagles usually soar with their wings almost flat. On the other hand, the turkey vulture—another dark, soaring bird—holds its wings up in a shallow V shape called a dihedral. A lot of large hawks also soar with slightly raised wings.

9. THEY'RE COMEBACK KIDS.

Baby eagle chicks in a nest.
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Before European settlers arrived, bald eagles were abundant across the U.S. But with settlement came habitat destruction, and the settlers viewed the eagles as competition for game and as a threat to livestock. So many eagles were killed that in 1940 Congress passed an act to protect the birds.

Unfortunately, another threat rose up at about that time. Starting after World War II, farmers and public health officials used an insecticide called DDT. The chemical worked well to eradicate mosquitos and agricultural pests—but as it traveled up the food chain, it began to heavily affect birds of prey. DDT made eagle eggshells too thin and caused the eggs to break. A 1963 survey found just 471 bald eagle pairs in the lower 48 states.

DDT was banned in the early 1970s, and conservationists began to breed bald eagles in captivity and reintroduce them in places across America. Luckily, this species made a spectacular recovery. Now the lower 48 states boast over 9700 nesting pairs.

10. THEY'RE UNIQUELY NORTH AMERICAN.

An African fish eagle flies over the water.
The African fish eagle is a relative of the North American bald eagle.
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You've probably heard of America's other eagle: the golden eagle. This bird lives throughout much of the northern hemisphere. But the bald eagle is only found in North America. It lives across much of Canada and the U.S., as well as northern parts of Mexico.

Though it may be North American, the bald eagle has seven close relatives that are found throughout the world. They all belong to the genus Haliaeetus, which comes—pretty unimaginatively—from the Latin words for "sea" and "eagle." One relative, the African fish eagle, is a powerful symbol in its own right. It represents several countries; for example, it's the national symbol of Zambia, and graces the South Sudanese, Malawian, and Namibian coats of arms.

11. THEY'RE AERIAL DAREDEVILS.

A bald eagle carries a fish off in its talons.
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It seems too weird to be true: While flying, bald eagles sometimes grab each other's feet and spin while plummeting to the Earth. Scientists aren't sure why they do this—perhaps it's a courtship ritual or a territorial battle. Usually, the pair will separate before hitting the ground (as seen in this remarkable set of photographs). But sometimes they hold tight and don't let go. These two male bald eagles locked talons and hit the ground with their feet still connected. One subsequently escaped and the other was treated for talon wounds.

12. THEIR EYES ARE AMAZING.

Close-up of a bald eagle's face.
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What if you could close your eyes and still see? Besides the usual pair of eyelids, bald eagles have a see-through eyelid called a nictitating membrane. They can close this membrane to protect their eyes while their main eyelids remain open. The membrane also helps moisten and clean their eyes.

Eagles also have sharper vision than people, and their field of vision is wider. Plus, they can see ultraviolet light. Both of those things mean the expression "eagle eye" is spot-on.

13. THEY MIGRATE … SORT OF.

A bald eagle sits in a snowy tree.
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If you're a bald eagle that nests in northern Canada, you'll probably head south for the winter to avoid the punishing cold. Many eagles fly south for the winter and return north for the summer—as do plenty of other bird species (and retired Canadians). But not all bald eagles migrate. Some of them, including individuals in New England and Canada's Maritime provinces, stick around all year. Whether or not a bird migrates depends on how old it is and how much food is available.

14. THEY CAN SWIM … SORT OF.

A bald eagle
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There are several videos online—like the one above—that show a bald eagle swimming in the sea, rowing itself to shore with its huge wings. Eagles have hollow bones and fluffy down, so they can float pretty well. But why swim instead of soar? Sometimes, an eagle will swoop down and grab an especially weighty fish, then paddle it to shore to eat.

Note that the announcer in the video above says that the eagle's talons are "locked" on a fish that's too heavy to carry. In fact, those lockable talons are an urban legend.

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How Bats Protect Rare Books at This Portuguese Library
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Visit the Joanina Library at the University of Coimbra in Portugal at night and you might think the building has a bat problem. It's true that common pipistrelle bats live there, occupying the space behind the bookshelves by day and swooping beneath the arched ceilings and in and out of windows once the sun goes down, but they're not a problem. As Smithsonian reports, the bats play a vital role in preserving the institution's manuscripts, so librarians are in no hurry to get rid of them.

The bats that live in the library don't damage the books and, because they're nocturnal, they usually don't bother the human guests. The much bigger danger to the collection is the insect population. Many bug species are known to gnaw on paper, which could be disastrous for the library's rare items that date from before the 19th century. The bats act as a natural form of pest control: At night, they feast on the insects that would otherwise feast on library books.

The Joanina Library is famous for being one of the most architecturally stunning libraries on earth. It was constructed before 1725, but when exactly the bats arrived is unknown. Librarians can say for sure they've been flapping around the halls since at least the 1800s.

Though bats have no reason to go after the materials, there is one threat they pose to the interior: falling feces. Librarians protect against this by covering their 18th-century tables with fabric made from animal skin at night and cleaning the floors of guano every morning.

[h/t Smithsonian]

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