Kleptoparasitic bear steals wolves’ kill in filmed Yellowstone drama

National Parks Service describes rare incident in which sneaky grizzly joined chase with the Junction Butte pack

Wildlife officials in Yellowstone national park captured the “unusual” sight of a cheeky grizzly bear tagging along with a pack of hunting wolves, then making off with their kill.

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The enthralling video, posted to the National Parks Service Facebook page, shows the October incident in which the wolves from the Junction Butte pack in northern Yellowstone were joined by a lumbering grizzly as they hunted a herd of elk.

After the wolves take down an elk, the bear moves in and steals the carcass: a phenomenon known as kleptoparasitism, or parasitism by theft, in which one species steals resources, most usually food, from another.

The Yellowstone incident was unusual, the NPS said, because wolves and bears usually compete for food and hunt separately. While bears stealing food wolves have captured is not uncommon, in this case the bear decided its best interests were served by actively joining the hunt.

“From the bear’s perspective, it takes a lot of energy to follow a wolf pack around, but the reward is high if it successfully takes over a carcass,” the NPS said.

“A fresh elk carcass is a wonderful source of fat and protein for a grizzly bear preparing for hibernation. This bear seems to have figured out that following the wolves in the morning will increase its chances of encountering a high-calorie meal.”

The wolves were forced to wait until the bear had finished its meal before taking advantage of their own kill.

“Typically, wolves will yield to incoming bears,” the NPS said. “Since hunting is dangerous and often unsuccessful, it’s better for wolves to wait their turn at a carcass that has been usurped by a bear than it is for them to continue hunting.”

Previous videos from Yellowstone show wolves and bears confronting each other. In one episode, filmed in 2019, a tour guide captured close-up images of a grizzly defending itself from a pack of wolves trying to reclaim an elk carcass.

Yellowstone is home to about 123 gray wolves, the NPS says, with 90% of their winter diet consisting of elk. The park, spanning parts of Idaho, Montana and Wyoming, also has about 150 grizzly bears, listed as a threatened species in 1975.

A federal judge restored protections for grizzlies in the greater Yellowstone ecosystem in September 2018, after the US Fish and Wildlife Service, claiming a “remarkable recovery”, delisted the species a year earlier.