Bear vs bison: Dramatic footage shows Yellowstone grizzly taking down a bison
Host to the largest concentration of big mammals in the conterminous United States Yellowstone National Park is one of the best places in North America to see large carnivores in predatory action.
On the afternoon of May 31, visitors to the park – only recently reopened on a limited basis after COVID-19-related closure – saw predatory action that’s especially rare to witness: a grizzly bear killing a bison. Michael Daus managed to capture cellphone footage of the encounter, which took place along the Firehole River at a trailhead in Yellowstone’s Midway Geyser Basin (Editor’s note: Be prepared for distressing footage and equally distressing, cheesy music):
Initially charged by the young bison, the grizzly ends up grappling its victim from behind, tearing into the bovid’s back as it staggers along. The struggling pair totter across a bridge over the river, then end up in the flow itself. The grizzly ultimately dispatched its hefty quarry along the riverbank. Park staff later moved the carcass on account of its proximity to the parking lot and trail.
According to Daus, the attack unfurled over about 17 minutes. It certainly made an impression. “To have it happen close by and relatively safe for the circumstances we were in,” he told the Billings Gazette, ‘that’s a treat.”
Yellowstone’s grizzlies are among the most carnivorous of North America’s inland brown bears, which partly reflects this Rocky Mountain highland’s great abundance and diversity of large ungulates. Animal protein for the bears, however, also comes in the form of everything from pocket gophers and cutthroat trout to ants and army cutworm moths, which Greater Yellowstone grizzlies seek out on austere talus slopes above timberline in summer.
The two most important big beasts for Yellowstone grizzlies, calories-wise, are elk and bison. These are commonly eaten as scavenged carcasses, an especially critical protein source in spring for lean “silvertips” (as grizzlies are sometimes called) freshly out of their winter dens. The 1990s reintroduction of grey wolves to Yellowstone has translated into a smorgasbord for grizzlies, too, given the infusion of wolf-killed carrion that resulted; grizzlies, especially big males, usually dominate wolves and enthusiastically run them off their kills.
But Yellowstone grizzlies can be capable ungulate predators in their own right. They’re especially adept at hunting elk calves in late spring and early summer: methodically scouring the sagebrush for bedded-down calves, rushing elk herds ambush-style with explosive speed, and sometimes testing herds at a lope in search of lagging youngsters:
In the fall, grizzlies also occasionally take down bull elk that are weakened or wounded from all the exertions of the rut.
The 4,000 to 5,000-odd bison of Yellowstone mainly feed grizzlies as carrion, but – as Daus’s video dramatically proves – they sometimes fall prey to the bears. This can happen, for example, in the spring, when bison weakened by the park’s gnarly winters are more vulnerable. As with elk, bull bison injured or tapped out from the fights and chases of the rut might be taken down by a large grizzly.
Speaking to the Billings Gazette, Yellowstone’s long-serving bear management biologist Kerry Gunther – who reckoned the griz in Daus’s footage was a subadult – said he’s seen a few grizzly attacks on bison, and has found buffalo carcasses with apparent bear bite marks on the spines. “We had a collared bear that would occasionally kill adult bison,” he told the Gazette. “So some bears get somewhat proficient at it.”
Bison, though, are no easy prey: not for a grizzly, not even for a pack of wolves. Huge, remarkably fleet, and well-armed, the bovids also range around in large herds, and may mount communal defence of vulnerable members such as young calves. Bison bulls commonly roam on their lonesome, but are also the biggest of their kind – they may weigh a ton – and can be mighty surly.