Bison are the largest land mammals in North America, but it’s not often that you see one challenging the continent’s top apex predator. That’s what happened earlier this year when a bison chased a grizzly bear up a steep hillside in a popular wildlife viewing area in Yellowstone National Park. The encounter was filmed and posted to Youtube by Pete Speer on May 30. See it for yourself below.

The two-minute-long video was shot in the Lamar Valley, which sits near the eastern edge of the 2.2 million-acre park. It starts out with the bison galloping at a steady clip toward a grizzly that’s grazing in a field of grass and sage brush. The bear keeps on going about its business until the charging bison gets so close that it can no longer be ignored.

Related: Watch Two Yellowstone Bison Rescue a Newborn Calf from Attacking Wolves

For a second, the bison stops running and just walks toward the bear. Then, when the bear takes off up the hill, the bison picks up speed again and resumes its chase. “What’s gonna happen here,” someone asks from behind the camera. “Oh my gosh, the bear can go up probably…better than the bison.”

The bear quickly leaves the lumbering bison in its dust. Within a matter of seconds, there’s well over 100 yards between the two animals, and the video cuts out. It’s unclear what sparked the altercation, but it appears that the bison was completely unprovoked in its audacious challenge of the big grizzly.

Read Next: Watch a Young Grizzly Bear Take Down a Bison After a Protracted Battle

While it’s somewhat shocking to see an ungulate running off a large carnivore like a grizzly bear, it might be more common than you think. “I’ve seen multiple cases where small groups of bison have been able to run bears off,” Yellowstone National Park bear management biologist Kerry Gunther told F&S contributor Steven Hill in a 2022 interview. “Often you’ll see big bulls lying in a meadow, and they might not even get up if a grizzly walks by, they’re so confident in their ability [to protect themselves].”