Discover the Largest Bear to Ever Exist (Up to 4X the Size of a Grizzly!)

Written by Colby Maxwell
Updated: August 30, 2023
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Bears are among the foremost predators on earth today. Although the planet is currently home to some massive bears, prehistoric bears used to be much, much, bigger. Polar bears and grizzlies may be one thing, but the largest bear to ever live dwarfed them.

Today, we will discover the largest bear to ever exist and learn what happened to this massive beast. Let’s get started!

Arctotherium angustidens, the Largest Bear to Ever Live

"Largest" Infographic for the Biggest Bear to Ever Exist.
Some scientists think that a Buenos Aires fossil indicates an A. angustidens that weighed 2167-4502 lbs.!

Arctotherium angustidens was an ancient species of bear that belonged to the Arctotherium genus. Although all members from this genus are extinct, this group of bears was the largest to have ever lived. Of this group of megafauna, one bear was the largest: Arctotherium angustidens.

This bear was the earliest and largest member of the entire genus and by far the largest bear to have ever lived.

Size

Homo sapiens VS Arctotherium angustidens size comparison

©Di (they-them) / CC BY-SA 4.0 – License

A. angustidens is estimated to have weighed between 900 and 2,645 pounds and stood between 11 and 14 feet tall. Besides being the largest bear in history, its sheer size would have put it in contention for the largest carnivorous land mammal to have ever lived.

One particularly large individual was discovered in Buenos Aires and had an unusually large humerus bone. Using this new fossil as an estimate, some scientists argue that A. angustidens could have weighed between 2,167 and 4,502 pounds, although our previous figures are a bit more conservative.

Distribution

Southern cone

A climate map that depicts the area of South America called the Southern Cone.

©Nicolas Almeida de Paula Ilha / CC BY-SA 4.0 – License

A. angustidens fossils were first discovered in South America. The ancient ancestors of the species likely crossed the Isthmus of Panama during a period of time known as the Great American Interchange.

Within the continent of South America, these bears seem to have stayed within a region known as the Southern Cone. The Southern Cone encompasses the southern countries south of the Tropic of Capricorn.

The highest concentrations of A. angustidens were likely found in Argentina, especially in the Buenos Aires Province.

When Did the Arctotherium angustidens Live?

Discover the Largest Bear to Ever Exist (Up to 4X The Size of a Grizzly!)
A

.

angustidens

went extinct around 700,000 years ago.

©Daniel Eskridge/Shutterstock.com

A. angustidens belonged to a temporal range between the Pleistocene and Holocene. The first members of the Arctotherium genus likely lived around 2 million years ago before dying out 10,000 years ago, spanning a period of nearly 1.99 million years. A. angustidens likely died out before then, probably around 700,000 years ago.

This migration and eventual evolution of A. angustidens was likely encouraged by the extinction of the metatherian sparassodont carnivores (marsupial-like mammals) in South America. With little competition, the migrating carnivores would have thrived as they expanded into the region.

Although A. angustidens was likely the first member of the Arctotherium genus, other members evolved soon after. Other members of the genus include A. vetustum, A. bonariense, A. tarijense, and A. wingei.

Why Did Arctotherium angustidens Become Extinct?

Arctotherium sketch

The Arctotherium, seen here in a sketch drawing, was found largely in South America. Image: Robert Bruce Horsfall, Public domain, via Wikimedia Commons

© Robert Bruce Horsfall (1869–1948) / public domain – License

The last member of the Arctotherium genus likely lived until around 10,000 years ago. The genus likely went extinct as the large prey they hunted became extinct while competition increased from other predators, notably humans.

What Is the Largest Bear Currently Alive?

Discover the Largest Bear to Ever Exist (Up to 4X The Size of a Grizzly!)

The polar bear is the largest living species of bear.

©Vaclav Sebek/Shutterstock.com

Although it’s a pretty close competition, polar bears are usually recognized as the largest bears in the world. Males (larger than females) usually weigh up to 990 pounds and can stand up to 10 feet tall. The largest polar bear ever recorded was a male killed in Alaska in 1960. This individual weighed 2,209 pounds and stood 11 feet 1 inch tall on its hind legs.

Grizzly bears, specifically Kodiak grizzly bears, are a close second. These grizzlies live in the Kodiak Archipelago in southwest Alaska. At their largest, Kodiak bears can grow to 1,500 pounds and stand over 10 feet on their hind legs.

Other Large Bears in the World

Large Kodiak bear

The Kodiak bear is the second largest bear species on Earth.

©Lisa Stoorza/Shutterstock.com

Following polar bears and Kodiaks in size are Kamchatka brown bears, the largest subspecies of brown bear in Eurasia. They can weigh up to 1,430 pounds and stand up to 9 feet, 9 inches tall on their hind legs. They are named after the Kamchatka Peninsula, where the majority of its population lives.

Also large is the Ussuri brown bear, known as the black grizzly bear or Ezo brown bear. Males can grow up to 1,210 pounds and usually are 6-9 feet in length. These bears can be found mainly in eastern Russia and its surrounding islands, as well as the Korean Peninsula, northeast China, and northern Japan.

Check out our full list of the top 10 largest bears in the world here.   

The Closest Modern Relative of Arctotherium angustidens

Discover the Largest Bear to Ever Exist (Up to 4X The Size of a Grizzly!)

The spectacled bear is the closest living relative of

Arctotherium angustidens

, who lived in South America during the Pleistocene period.

©Andrei Preda/Shutterstock.com

Although no members from the Arctotherium genus are still around, there are closely related species currently alive today. The South American spectacled bear is a relative of the genus and belongs to the Tremarctinae subfamily, just like Arctotherium.

Spectacled bears are also known as Andean bears, Andean short-faced bears, or mountain bears, and they live along the Andean Mountain range in South America. These bears generally weigh 220-440 pounds and stand 6-7 feet tall when on their hind legs.

The photo featured at the top of this post is © Daniel Eskridge/Shutterstock.com


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About the Author

Colby is a writer at A-Z Animals primarily covering outdoors, unique animal stories, and science news. Colby has been writing about science news and animals for five years and holds a bachelor's degree from SEU. A resident of NYC, you can find him camping, exploring, and telling everyone about what birds he saw at his local birdfeeder.

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