Bison Versus Bear Filmed at Yellowstone National Park

Footage of a bear attacking a bison has been captured by a visitor to Yellowstone National Park. The five-minute film shows the juvenile bison initially charging at the bear, before the bear attacks and appears to kill its opponent on the banks of a river.

The encounter took place near the Grand Prismatic Overlook trail and was shot by Michael Daus, who owns Jackson Hole POP!, in Jackson, Wyoming. The video, shot on an iPhone and posted to YouTube, was taken on May 31. He took it during a day trip to the national park with his family.

In a caption to the video, Daus said he saw the grizzly bear near the road about a mile from where the encounter took place. He and his family carried bear spray and had remained "on the lookout" for it. "We weren't crazy about returning to find the bear so close, just beyond the opposite side of the small parking area," he said. "We didn't even see it until we were at our vehicle. I was particularly relieved that the bear seemed more interested in the bison, so while very close to the car, we simply maintained what felt like a safe distance."

Grizzly bears in Yellowstone are known to prey on bison, which tend to give birth to calves in late April and early May. Bears and wolves are the only large predators of adult bison in Yellowstone, with dead bison also providing an important source of food for scavengers.

According to the National Park Service, elk and bison make up a large portion of a grizzly bear's diet between March and May. Larger male grizzlies will also prey on adult bison in early spring. Travis Wyman, from the Bear Management Office of Yellowstone National Park, described one encounter between the two species in an article published in the International Association for Bear Research and Management in 2002. He said the grizzly bear chased the bison down and attacked it repeatedly over the course of the day, with attacks becoming less frequent over time. Eventually it abandoned the bison and Wyman found it alive but severely wounded, so park managers shot it and removed the carcass.

In another encounter published in 2001, Kerry Gunther and Nathan Varley describe an attack on a juvenile bison by a grizzly bear. While the calf's mother tried to fend off the attack, the bear killed the bison, fed on it, then covered it with dirt. The bear and its two cubs returned to the carcass later to feed.

Populations of both bison and grizzly bears were placed under threat during the 20th century, with their numbers dropping drastically as a result of human activities. Conservation programs have led numbers of both to rebound. There are now an estimated 150 grizzly bears in Yellowstone National Park, and almost 5,000 bison.

yellowstone bear
A bear walks along a road in Yellowstone National Park in 2005. William Campbell/Corbis via Getty Images