New Laws Hope To Stop Spread Of Disease Between Bighorn And Domestic Sheep

Mar 13, 2015

Sims sheep grazing on their winter range.
Credit Melodie Edwards

When it comes to the spread of disease from domestic sheep to bighorn sheep, it’s not that different from the arrival of Europeans in the Americas when small pox and other diseases killed millions of indigenous people. Without a built-in immunity, pneumonia can wipe out an entire bighorn sheep herd in no time. And that’s why, last week, the Wyoming legislature passed a pair of historic bills that will effectively keep the two species apart.

Out on the high mountain desert south of Lyman, rancher Shaun Sims calls to his sheep and they call back. It's one of those tricks passed down generations.

“My family history is that John Sims, Sr.,” Sims says, “which is six generations back from me, come to the Evanston area in 1865 and settled there.”

But it hasn’t been easy for the Sims family. Ever since the 1970's, sheep ranching has become almost as endangered as bighorn sheep. New environmental rules barred lethal control of predators and Americans lost their taste for mutton. And that dropped the numbers of sheep from six million at its peak to current numbers of around 300,000. And with so few neighbors raising sheep, ranching is more complicated.

“Slaughter plants for our lambs, the sheering to get the sheep sheered, the trucking industry, the whole infrastructure is shrunk as the sheep industry has shrunk.”

From this ridge, Sims points south at the peaks of the Uinta Range, now dusted in spring snow. It’s here that he moves his herds to fatten his lambs in the summer.

“This is the best summer sheep country in the entire United States, arguably,” he says. “It is a perfect scenario to graze up those mountains and onto those high tops.”

I want to see bighorn sheep. There's a place for the grizzly bear and there's a place for the wolf. But we as humans also need a place here.

The Uintas, however, are in Utah, not Wyoming. He points out a craggy peak.

“The bighorn sheep are east of that. And they range all the way down to Flaming Gorge.”

It’s a herd transplanted there in the 1980's and it’s migrating close to Sims' grazing allotments. The problem is Utah doesn’t allow sheep to mingle with bighorns because of the threat of spreading pneumonia and wiping out the herd. When sheep graze too close, young bighorn rams often go looking for love in all the wrong places and can wander the countryside for miles, spreading the bacteria. But in Wyoming, transplanted herds like this one are allowed to mingle with sheep. Wild Sheep Foundation director Kevin Hurley says it’s protecting native herds at any cost that’s the basic idea behind Wyoming’s sheep plan.  

“In Wyoming, we currently enjoy between six and seven thousand bighorn sheep. The majority of those, 90 percent of those, are in our core native herds in the northwest quadrant of Wyoming,” Hurley says. “And so, ten percent of our bighorns are in other parts of the state in transplant herds.”

For years, the U.S. Forest Service has said if every state would do what Wyoming has done, sheep ranchers and wildlife advocates could resolve their disputes. But Hurley says other states might not have the stamina Wyoming did to reach consensus on some very basic points, like the science behind whether sheep really spread pneumonia to bighorns.

“The science is not absolute,” rancher Shaun Sims says. “There's other stress factors that cause the disease to pronounce itself.”

Hurley disagrees. “The science is real. We've asked for a single peer-reviewed published piece of scientific literature that says they're compatible and they can be fine together. We're not aware of one.”

Chris Iverson is the Deputy Regional Forester for the U.S. Forest Service’s Intermountain Region. He says two of Wyoming’s core native bighorn sheep herds—the Jackson and the Whiskey Mountain herds-- are really struggling.

“Both of these herds declined significantly, about 30 percent or more. And they have not rebounded.”

And he says pneumonia is a likely culprit for their dwindling numbers. In an effort to help bighorn sheep thrive, the U.S. Forest Service is working on a risk assessment study of the Western U.S. that could borrow heavily from Wyoming’s sheep plan. It would protect native herds at any cost and de-emphasize transplanted ones. In fact, last month, Iverson’s office sent a letter to Governor Mead confirming the U.S. Forest Service support. But asked whether it would it work for every state, he says, “each state has to do what’s best for their state under their specific circumstances.”

“Here’s the unfortunate part of that letter,” says Senator Larry Hicks of Baggs who sponsored the bills that put Wyoming’s sheep plan into law. “If the risk assessment came out and even if they used the Wyoming Plan, my anticipation is we will probably still see litigation.”

Hicks says the Wyoming Plan worked perfectly well to keep sheep and bighorns separate for the last decade and he’s disappointed to have to turn what was an old-fashioned Wyoming handshake into law. But he says it’d be worse to see decisions about Wyoming’s wildlife made in the courts.

It’s a sentiment rancher Shaun Sims shares. He says whatever the Forest Service decides about his grazing permits. "I want to see bighorn sheep. There’s a place for the grizzly bear and there’s a place for the wolf. But we as humans also need a place here."

Forester Chris Iverson says the Forest Service plans to complete its bighorn/domestic sheep risk assessment in coming months.