YELLOWSTONE NATIONAL PARK, Wyo. - The largest wolf pack in Yellowstone National Park may be growing too large to sustain itself, the leader of the park's wolf recovery project said.
The Druid Peak pack has 26 wolves, compared to the average packs that have about 10 wolves.
Twenty of the Druid Peak wolves were born last spring in a record litter.
Now the pack is showing signs of stress, said Doug Smith, park leader for wolf recovery. Two of four pregnant wolves apparently lost their pups and the surviving pups are underweight.
"They were among the lightest pups we've seen in six years," Smith said.
To feed its members, the pack expanded its territory. It dominates the Lamar Valley in northern Yellowstone National Park.
Problems for the pack could increase this summer as elk and other ungulates grow stronger and become less vulnerable to wolf attacks than they were during the winter.
Also, the social dynamics start to break down when a pack has too many wolves, Smith said.
"Something has got to give," he said. "The pups last year are now yearlings, and I think some of those yearlings are going to disperse, and I think some of them are going to die."
The alpha male and alpha female of a pack typically produce the only litter each year, but the Druid alpha male bred with two other females besides the alpha female.
Another pack, known as the Rose Creek pack, once dominated northern Yellowstone with 24 wolves, but the pack's numbers dropped to 10 and the group divided.
As the Rose Creek population declined, so did its authority among other wolf packs. The Druids moved west and took over a healthy swath of Rose Creek territory.
"I think that' s a good prototype example for what is going to happen to Druid Peak," Smith said.