It’s a wolf eat bison world; we’re just living in it.

In Yellowstone National Park, as in other parts of the West, elk populations have been declining over the past two decades. According to the National Park Service (NPS), winter counts of the northern elk herd declined from nearly 20,000 individuals in the 1990s to less than 5,000 in the 2010s.

The cause for the decline includes the impact of predation from the park’s gray wolf population, which was reintroduced in 1995, as well as other factors such as predation from grizzly bears and mountain lions, climate change, hunting of elk outside of the park, and more. 

Meanwhile, the park’s bison herds have been thriving. And its wolves appear to have caught on. Just last week, a wolf pack downed a bison after an hours-long standoff on the Firehole River. The incident was not isolated. 

In fact, NPS wildlife biologist Dan Stahler recently told the Cowboy State Daily that Yellowstone’s wolves have shifted their diets to include a greater proportion of bison, including those that they actively hunt and those that they just scavenge. 

A wolf pack feeds on a bison carcass in Yellowstone National Park.
Yellowstone’s Wapiti Pack feeds at a bison kill site. Jacob W. Frank via NPS.

“Any wolf packs that are in the park, if they have bison in their territory, they will prey on bison,” he said. “Wolves are persistent. A bison kill is usually a long-lasting event, just because it’s so difficult, and it’s dangerous. We’ve documented wolves getting killed hunting bison over the years.”

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Stahler’s statement confirms an important aspect of wolf biology: The apex predators are considered opportunistic generalists, meaning that what wolves eat varies depending on the food sources available to them. This is why wolves have been known to prey on livestock when the opportunity arises. And in Yellowstone, it appears the species’ persistent opportunism might ensure that park visitors can witness more wildlife interactions like this one in the near future.