Rocky Mountain bighorn sheep ravaged by disease

Across the northern Rocky Mountains, bighorn sheep are dying by the hundreds from pneumonia and alarmed wildlife officials are hunting and killing the majestic animals to halt the spread of the disease.

Since winter, nine disease outbreaks across five states in the West have claimed nearly 1,000 bighorns, prized as a game animal for the prominent curled horns of the adult males, or rams. More than 400 bighorn sheep in Nevada, Montana, Utah and Washington have died – or been killed by wildlife officials – this winter, and the death toll is expected to rise in coming weeks.

More than half of the dead sheep were from four herds in western Montana alone, and 79 of the deaths were from two herds in northeastern Nevada.

Eighteen bighorns have died in south-central Washington, and 26 have been killed in eastern Utah to stop the spread of the disease.

Scientists recently confirmed what they long suspected -- the cause of the plague is contact between the wild bighorns and domestic sheep flocks.

Putting the blame on domestic sheep has heightened a furious debate between advocates of the wild bighorns and sheep ranchers -- one skirmish in a bigger war between proponents of economic interests and those seeking protection of remaining wild areas and species in America's West.

The population of bighorns has declined sharply since the settlement of the West. Fewer than 100,000 sheep are believed to roam the rugged mountain slopes today, compared with an estimated 1.2 million head of bighorn at one time.

Episodic outbreaks of disease have thinned bighorn herds for years. A study, "Mortality During Epizootics in Bighorn Sheep: Effects of Initial Population Size and Cause", published in the latest edition (July 2010, Volume 46, Number 3) of the Journal of Wildlife Diseases concluded that domestic sheep were the carrier-culprits behind bighorn pneumonia epidemics.

Led by a team at Washington State University-Pullman, researchers placed an identifying protein into a bacteria culture, then documented how the pathogen moved from domestic sheep to wild ones.

WILD VERSUS DOMESTIC SHEEP

"The study proves what a lot of us suspected all along: that domestic sheep are the biggest management challenge to the restoration of wild sheep," said Kevin Hurley, a bighorn expert for the Wyoming Game and Fish Department and head of an interstate wild sheep task force.

Following the study, the Payette National Forest (right) in western Idaho, where domestic sheep herding is prevalent, announced it was cutting its sheep grazing allotments by nearly 70 percent over the next three years.

Sheep ranchers are angered by the Payette decision. They fear it sets a precedent for public land management that could sound the death knell to an industry, already beset by falling production and competition from meat and wool imports.

Third-generation Idaho sheep rancher Frank Shirts, whose grazing lands on the Payette are targeted for cuts, is skeptical that flocks such as his are infecting the bighorns.

"It's a bunch of baloney," said Shirts, 57. "I bought my first sheep when I was 7, and I've worked my whole life to build this outfit. It's a shame what's going on here. They're going to put the Western sheep industry out of business."

KILLING THEM TO SAVE THEM

To save the bighorn, wildlife agencies in several Western states where the disease has spread are killing not only sick bighorns but healthy animals that make contact with domestic flocks.

"I know it sounds strange that we have to kill bighorns to save them, but we can't allow an atomic ram to go back into the population and infect the rest of the band. It's like gangrene -- you cut off the toe to save the leg," said Wyoming's Hurley.

Tom Keegan, wildlife manager for Idaho Fish and Game, said the disease lowered bighorn lamb production for many years. The current reproduction rate is barely enough to sustain the herds, one reason biologists take extreme measures when an animal appears ill, he said.

The killing of bighorns by wildlife agencies has sparked opposition from some conservation groups that share the same goal of preserving the wild sheep.

"The bighorns should never come into contact with domestic sheep," said John McCarthy of the Wilderness Society, among the environmental groups that have sued to get domestic sheep flocks off the Payette altogether. "We don't need to have punitive measures against the bighorns."

Source:
Reuters, "Rocky Mountain bighorn sheep ravaged by disease", accessed October 2, 2010