But the Idaho Department of Fish and Game isn't releasing the exact location of the site.
"We don't want people flocking to the area to view the wolves," said Dave Parrish, Magic Valley regional supervisor for Fish and Game.
Confirmation of the den's existence follows a number of recent reports from valley residents who sighted both gray- and black-phase wolves north of Ketchum.
Parrish said breeding wolf pairs have ventured into the Wood River Valley from adjacent ranges at times in the past, but those pairs have always located their dens outside the valley.
Due to the confirmed wolf activity, at least one local livestock grazer—Hailey-based Lava Lake Land and Livestock—is working with officials from the Sawtooth National Forest to modify its sheep-grazing patterns this summer. Lava Lake's grazing rights include the North Fork-Boulder grazing allotment.
Ketchum District Ranger Kurt Nelson said the company had intended to begin grazing one of its ewe-lamb bands in the vicinity of the den this week. However, he said, due to the recent development, it will graze the band farther south on the Indian Creek and Cove Creek allotments. The joint Forest Service-U.S. Bureau of Land Management allotments are east of Highway 75 between Ketchum and Hailey in the low-elevation sections of the Pioneer Mountains.
In conjunction with Fish and Game personnel, the Sawtooth National Forest will monitor wolf activity in the northern Wood River Valley to determine if grazing may be appropriate in the area later this summer, Nelson said.
Once pups are large enough to begin traveling—this happens during the summer—packs leave their den sites and begin using a much larger territory. The home ranges for Idaho wolf packs typically encompass between 250 and 350 square miles, wolf experts say.
Nelson said the Sawtooth National Forest has always had to manage livestock grazing with the realization that predation does occur.
"You've got mountain lions, you've got black bears," he said.
He said the addition of wolves to the mix just means the agency has another predator to consider when managing grazing on the forest.
"The question is how do we manage it intelligently," he said.
Recently, wolves from another pack west of the Wood River Valley in the Smoky Mountains attacked and injured a sheep guard dog, Parrish said.
"It was severely injured," he said.
He said the same wolves also killed a number of sheep in the band.
On Thursday, Mike Stevens, president of Lava Lake Land and Livestock, confirmed that his company is working closely with the Forest Service, Fish and Game and the U.S. Department of Agriculture's Wildlife Services to understand where the wolves are and what they're doing.
"Because of the den with pups up there we have delayed the arrival of sheep onto that allotment," Stevens said. "We are going to watch the situation as it unfolds over the course of the season."
He said that shifting grazing areas in response to natural factors such as the arrival of a wolf pack is consistent with Lava Lake's long-term grazing plan. The livestock company won't move sheep into the North Fork-Boulder allotment until biologists verify the wolves have moved on to wider ranges, Stevens said.
Stevens said Lava Lake has a history of using similar proactive measures on other allotments. The company's ranch and many of its grazing allotments are northeast of Carey in the southern Pioneer Mountains.
This story first appeared in the Idaho Mountain Express on June 22, 2007.