YELLOWSTONE NATIONAL PARK (AP) - Wolf No. 42, one of the 28 transplanted Canadian wolves that brought the species back to Yellowstone National Park, was killed over the weekend in a battle with other wolves.

"She was truly part of history," said Doug Smith, leader of the Yellowstone Wolf Project. "We're looking at one of the wolves that had a significant impact on wolves in Yellowstone."

She was 8 years old, well beyond the average of 5 or 6, and the only one of the original 28 that remained in the park.

Her sister, No. 41, is now the only survivor from that original group brought to the park in 1995 and 1996. She lives outside the park in the Sunlight Basin north of Cody.

No. 42, the alpha female of the Druid Peak pack, appears to have been killed by Mollie's pack, a neighboring group of wolves that were once displaced by the Druids and have been poking around the old territory ever since. The rivalry goes back to 1996, Smith said.

"We're 100 percent sure she got killed by other wolves, and I'm 80 to 90 percent sure it was the Mollies," he said.

The two packs probably clashed late Saturday or early Sunday, and No. 42 and the Druid pack's alpha male, No. 21, probably were targets in the attack, Smith said.

"It's not uncommon in wolf warfare … to go for the alphas," Smith said. "It's like taking out a general as opposed to a corporal or a private."

On Sunday, aerial crews spotted No. 42's carcass on Specimen Ridge. Her radio collar was putting out a "mortality signal," which is activated when a wolf stops moving.

On Tuesday, Smith and a group of biologists trekked about four miles through the snow to get to No. 42's carcass. By then, eagles, ravens and coyotes were already feeding.

Park officials removed No. 42's head and left the body to be eaten. Smith said he's hoping No. 42's skull can eventually be displayed for visitors.

"For Yellowstone, which of all national parks in the United States is steeped in history, we had to bring back that skull," Smith said.