Being a giant predator during the Pleistocene — from around 2.6 million years to about 11,000 years ago — was no easy feat. From short-faced bears to Ice Age coyotes, American cheetahs, dire wolves, saber-toothed cats, and American lions, competition was a plenty, and staying alive was a daily battle. But yet, this mega-bear was still the apex predator of its time, thriving across North America for millions of years.

“Just in the last 13,000 years, we’ve lost most of the big mammals on the continent,” says Emily L. Lindsey, assistant curator, and excavation site director at the La Brea Tar Pits in Los Angeles, California. “This is the biggest extinction wave since the dinosaurs.” 

The Life of Giant Bears

Standing at 11 feet on its hind legs, the short-faced bear was the most enormous mammalian carnivore ever to live in North America. These were giants compared to the bears we see today. When you compare the skull of a grizzly bear, for example, which is large enough to eat a human, you can see that the short-faced bear skull was much larger, says Lindsey.

Today, its only remaining relative is the spectacled bear (Tremarctos ornatus), which is mostly herbivorous, about the size of a black bear,  and lives in South America.

The short-faced bear would not have had any predators because of its size, but in theory, says Lindsey, a pack of saber-tooth cats or maybe an American lion could have taken on a juvenile short-faced bear, but it certainly wasn’t common. 

Read More: Saber-Tooth Cats and Dire Wolves Had Joint Ailments During the Latter Years of the Ice Age

A Flexible Diet

In terms of the bear’s diet, research published in the journal Scientific Reports found that short-faced bears in the Pacific Northwest were highly carnivorous, but those found in southern California, for example, were more omnivorous, similar to a modern grizzly bear.

Researchers know this because the bears found in Rancho La Brea in the Los Angeles Basin seemed to have more cavities in their teeth, likely the result of eating starches and fruits of the landscape.

However, it’s worth noting, says Alexis Mychajliw, director of the Holocene ecology, diversity, and global extinctions (HEDGE) lab at Middlebury College in Middlebury, Vermont, that these bears covered a wide swath of territory in North America and their diet would have varied depending on their habitat.

Other experts contend that they were big scavengers of carcasses, which would make sense because they were so large and could intimidate any number of predators on the scene.

“These were flexible eaters, which is what we would expect from a bear,” says Mychajliw.

Read More: Giant Armadillo Butchers Push Back Human Arrival Time in South America

Why Did the Short-Faced Bear Go Extinct?

The short-faced bear went extinct around 11,000 years, at the end of the Pleistocene, along with most of the large mammals that lived alongside it, including all the large carnivores listed above, as well as giant ground sloths, mammoths, mastodons, giant beavers, camels, and giant armadillos.

It’s not completely clear why they went extinct or whether a number of factors combined to make life difficult on the continent. The end of the Pleistocene was a period of rapid climate change, with ice melting and temperatures rising. At the very same time, humans made their way to North America around 15,000 years ago, and it’s also possible that human hunting played a role in the demise of large mammals like the short-faced bear.

Other research published this year in the journal Science shows that human-ignited wildfires overtook the California landscape and drove extinction in that part of the world.  

We don’t know exactly what happened to these massive creatures, but now all that is left of them are giant fossils dispersed throughout the continent. Still, we do know that when they were alive, they would have been a sight to see: enormous and intelligent, rivaling any of the predators that have ever called North America home.

Read More: Rare Mummified Saber-Tooth Cat Cub Found in Siberia Still Has Fur

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Sara Novak is a science journalist based in South Carolina. In addition to writing for Discover, her work appears in Scientific American, Popular Science, New Scientist, Sierra Magazine, Astronomy Magazine, and many more. She graduated with a bachelor’s degree in Journalism from the Grady School of Journalism at the University of Georgia. She’s also a candidate for a master’s degree in science writing from Johns Hopkins University, (expected graduation 2023).