Far North Grizzlies Develop Taste for Muskoxen

One month ago, Badami oilfield worker Royce O'Brien focused his binoculars on a rare Alaska encounter-a grizzly bear standing nose-to-nose with a muskox. Suddenly, the grizzly made its move.

"The brown bear ran up and got behind the muskox like a wrestler would, and got its front leg over the muskox's shoulder," O'Brien said. "It bit into its neck and pulled it to the ground."

The muskox struggled free and got back to its feet to face the bear and its two yearling cubs. The adult bear then flashed past the muskox's horns, duplicated its wrestling move, and pulled the muskox down a second time.

"As soon as it hit the ground, the yearlings were in there," said O'Brien, an environmental technician at Badami oilfield, located on the Beaufort Sea coast about 30 miles east of Prudhoe Bay. O'Brien watched as the bears killed the muskox and began feeding, witnessing an event that was unheard of in Alaska until recently-far-north grizzlies killing muskoxen, sometimes as many as five at a time. Biologists are intrigued by a few instances of "surplus killing," behavior for which grizzlies are not known.

"There's been a dramatic increase in known grizzly bear kills of muskoxen," said Patricia Reynolds, an Arctic National Wildlife Refuge biologist with the U.S. Fish and Wildlife Service. "Sometimes a bear kills more than one animal from a group. Why?"

Since 1982, Reynolds has studied the 300 or so muskoxen that live inside or near the borders of the refuge. Last spring, a U.S. Fish and Wildlife Service pilot saw several muskox carcasses while flying over the Canning River. The pilot, Dave Sowards, thought someone with a rifle must have killed the animals, so he called Curt Bedingfield, an Alaska State Trooper who works in Coldfoot. Bedingfield flew into the site and, from tracks and other sign, found that one bear had killed five muskoxen and another bear had killed two. Reynolds and biologists Dick Shideler and Harry Reynolds have now counted eight incidents of multiple kills of muskoxen by grizzly bears in northern Alaska.

Bears and muskoxen have coexisted in the Arctic National Wildlife Refuge since 1969, when state biologists moved 51 muskoxen to the area from Nunivak Island. Known for their curved horns and shaggy hair that makes them look haystacks on legs, muskoxen have thrived in the refuge and elsewhere in the Arctic, ranging from the Colville River east to Canada's Mackenzie River. Here, their range overlaps with brown bears known as "barren-ground grizzlies," which are smaller than grizzlies from more productive areas but are the same species.

These northern grizzlies are some of the most adaptable creatures on Earth, and they may have just figured out a method of killing muskoxen, Reynolds said. When threatened, muskoxen often position themselves rump-to-rump, in a circle-the-wagons defense that may work well against wolves but not bears. Male bears of the North Slope emerge from their dens in late March and April, when snow still covers the landscape.

"They're hungry critters up there," Reynolds said. "There isn't a lot to eat." The farthest-north grizzlies now preying on muskoxen are among the least productive of brown bears in Alaska; females don't have their first litter until they are seven years old. These bears eat anything, from tubers of spring flowers to whales, and in learning to kill muskoxen they have exposed themselves to a new risk. After two recent encounters, muskoxen's curved horns allowed them to kill one grizzly and seriously wound another.

Why the bears sometimes kill more muskoxen than they can eat is a mystery, Reynolds said. Maybe deep snow, which slows muskoxen to a crawl, is allowing bears opportunities to kill that did not exist before. Maybe, when surrounded by prey, a bear's instincts churn into overdrive, like a weasel killing chickens in a henhouse. Only the bears know for sure.