Bighorn sheep challenges, successes continue through research, experienceWritten by Christy Hemken
A challenge that remains is the static herd size of the Whiskey Mountain group above Dubois, while a success has been the transplant and growth of a herd to Devil’s Canyon on the west slope of the Big Horn Mountains and the first legal sheep tag issued in northeast Wyoming for the 2009 hunting season.
There are 16 herd units identified in Wyoming, although some of them don’t currently support any bighorn sheep.
“Statewide, about 90 percent of bighorns occur in eight core native herds, and the other 10 percent are in seven transplant herds,” says Wyoming Game and Fish Department (WGFD) Bighorn Sheep Coordinator Kevin Hurley, who’s based in Cody. Those eight core native herds occur in the northwestern quadrant of Wyoming.
The statewide aggregate objective for bighorn sheep is 8,735, and the current estimate is just over 6,000 sheep. “We’re about a third under where we’d like to be. Are we ever going to get there? I’m not sure,” says Hurley.
In the Whiskey Mountain herd, which has yet to recover from a die-off in the winter of 1990/1991, the objective is set at twice what the current estimate is.
“That population was our source for multi-state transplants from 1949 through 1995, and we moved about 1,900 bighorns and placed about 1,500 in-state and 400 went to other Western states,” explains Hurley.
Hurley says biologists speculate that a high density of bighorns, particularly on winter range, contributes to die-offs. He adds that one way to control populations is through transplants, but there isn’t always a place to go with extra sheep. To remedy that, the Wyoming Legislature in their last session authorized the Wyoming Game and Fish Commission to offer reduced ewe/lamb licenses under HB 225.
“The Department supported it, and it sailed through,” he says. “It won’t be used for the 2010 season because of the way regulations have to follow legislative timelines, but in 2011 we think there will be application and merit to offer some very limited, focused ewe/lamb licenses in certain areas.”
In addition to population control, ongoing work in Whiskey Basin includes predator control, selenium research and prescribed burns to open up habitat. “There’s still a lot of work underway to get Whiskey Basin back on its feet,” says Hurley.
In the Laramie Peak area the herd objective is 500 in Area 19, while the estimate is half that. “We took a lot of sheep from Whiskey Basin and put them at Laramie Peak over a 30-year period from the 1950s through the 1970s,” explains Hurley. “They’ve persisted, but not grown steadily.”
However, he says in the last decade’s prescribed burns and wildfires have opened more habitat to the bighorns, which seems to be helping the population spread and increase.
Another tactic implemented on Laramie Peak in 2007 is using sheep from areas other than Whiskey Basin to repopulate some of the lower, more arid bighorn sheep habitats.
“I made arrangements with Montana to transplant 42 bighorns that were, in my view, a better match between the source sheep and target habitat,” says Hurley. “We’re trying to do a better job, instead of having Whiskey Basin as our one and only source, of trying something different that would be a better match for the habitat we’re trying to fill.”
The same scenario has taken place in the Devil’s Canyon herd above Lovell in Area 12, where 39 sheep were taken from Whiskey Basin in 1973. “They persisted for 30-plus years, but never really grew. Six years ago we took a look and saw good habitat and potential and instead of repeating 35 years ago we tried a different source better adapted to the habitat,” says Hurley.
Looking for sheep adapted to a dry river canyon or small mountain range in a low precipitation zone and low elevation with a higher percentage of shrubs than grasses for diet, Hurley partnered with Oregon and in December 2004 and moved 20 head from north central Oregon to Devil’s Canyon. Twenty more were moved to the area in January 2006 from the Missouri Breaks area of Montana.
“That herd has grown from 50 or 60 to three times that,” notes Hurley of the transplant success.
Taking the domestic sheep allotments on the Bighorn Mountains into account, Hurley says his agency has worked closely to avoid contact with domestic sheep. “The other thing about our source sheep is they’re known to be sedentary instead of migratory,” he says. “We wanted them to imprint and stay home and not pioneer and get into trouble.”
“We’ve tried for 10 years to do the best job we can of trying to reoccupy historic and still suitable bighorn habitat without forcing or shoving domestic sheep producers on private or public allotments out of the way,” he says of meetings amongst all interested parties.
In the immediate future another supplemental release is planned for the Seminoes. In December, 20 Oregon sheep will be moved in, and five weeks later 40 more from Antelope Island in the Great Salt Lake in Utah, once again matching compatible source sheep to the destination habitat.
Hurley lists some of the main factors in matching sheep to habitat as green-up of vegetation and lambing chronology. “As in domestic sheep, we want the lactating female to be in peak condition when she drops the lamb. What we think happened at the Seminoes before is we’d get high elevation alpine migratory sheep that were used to lambing in late May/early June and move them down to the Seminoes, which are much lower, hotter and dryer. The lambs were probably dropped when peak green-up was over and the ewes had already started on downhill slide when the lamb was born and they couldn’t nurse them adequately, they weaned them earlier and at a lighter weight and they didn’t make it,” he explains. “What we’re trying for with Oregon and Utah are sheep that lamb earlier so we more closely coincide with peak green-up.”
In other issues, biologists are weighing the impacts of beetle kill. While the thinning of the trees will expand bighorn habitat, that also means they’ll roam farther and potentially create more conflicts with domestic sheep.
On a West-wide perspective, there are 14 states with a wild sheep resource, and the issue of contact between domestic and wild sheep is the number one or number two concern in all of them. While Hurley describes Idaho as “ground zero” in separation efforts, the Sierra Nevadas on the Nevada/California border have federally listed the bighorn sheep. That listing comes alongside a multi-generational long-term domestic sheep grazing tradition on the federal lands of the region.