Posted: Wednesday, March 16, 2016
A large wolf pack has been picking off yearling cattle in the Hoback River Basin southeast of Jackson, prompting a deadly response from federal wildlife managers.
The Dell Creek Pack, which numbered as many as 16 animals, has repeatedly killed cows grazing on private ranchland north of Bondurant this winter. Gunning from a helicopter has in recent weeks trimmed the pack down to 11 members.
“They were coming in and taking 500-pound calves,” U.S. Fish and Wildlife Service Northern Rocky Mountain Wolf Coordinator Mike Jimenez said Friday. “We’ve taken five wolves out. We took two out last week and took three more out this week.”
Not detected until 2014, the Dell Creek Pack hadn’t taken to eating livestock until this winter. Roaming an area with two elk feedgrounds and lots of prey, the wolves doubled their numbers over the last year — a factor that could have played into their recent behavior, Jimenez said.
“We know these large packs are very problematic,” he said. “There’s a high food requirement. They can down larger prey.”
A branch of the U.S. Department of Agriculture, Wildlife Services, took the lethal action against the wolves.
Using location information from a tracking collar fitted on one pack member, Wildlife Services shot the wolves aerially — most recently when they were actually among cows in a pasture.
A new collar the Dell Creek Pack received in February wasn’t added to create a “Judas wolf” to assist in conflict management, but rather was part of routine monitoring, Jimenez said.
Nonlethal techniques in the Hoback Basin were not attempted to try to get the canines and cows to play nice, Jimenez said.
A long-term plan Wildlife Services’ Wyoming office is still finalizing proposes using a “full range of legal, practical and effective nonlethal and lethal” methods to prevent and reduce wolf conflict.
Techniques like using riders to keep an eye on livestock or guard dogs to protect them were not practical because of the large size of the pasture where the conflict was occurring, Jimenez said. He did not name the ranch involved.
“Where nonlethal has been a reasonable approach has been with smaller numbers of livestock,” Jimenez said, “and in small areas where there’s less acreage involved.”
There are competing schools of thought on the effectiveness of killing wolves to reduce conflicts with livestock.
A 2014 study funded by the Washington Department of Fish and Wildlife found that the odds of depredations increased for both sheep and cattle when suspected livestock-killing wolves were killed at low rates.
The next year, however, Jimenez and other wildlife managers wrote a response that concluded that killing lots of wolves from aggressive packs was an effective deterrent.
“Ultimately, pack size was the best predictor of a recurrent depredation event,” Jimenez and colleagues wrote in the Journal of Wildlife Management. “The probability of a depredation event recurring within five years increased by 7 percent for each animal left in a pack after the management response.”
Wildlife managers will continue monitoring the Dell Creek Pack, which is covering lots of ground and has not settled down near private land where the conflict has occurred, Jimenez said. Hoback Basin ranchers, he said, are starting to calve right about now, which “unfortunately” will result in a young batch of domestic animals that are vulnerable.