Pneumonia chips away at bighorns

Sun., Nov. 14, 2010

Bighorns don’t mix
with domestic sheep

Pneumonia is like the bird flu of the bighorn sheep world, and domestic sheep are prominent disease carriers, according to a recently published study by Washington State University researchers.

The study confirmed what many experts already believed: Domestic sheep, which aren’t as susceptible to M. haemolytica bacteria, transfer the bacteria when they come in contact with bighorn sheep, which then often die from it.

Wildlife managers knew bighorns tended to die from pneumonia after contacting domestic sheep, but some ranchers denied sheep were the cause.

The study’s results provide more fuel for critics who argue that domestic sheep should not be allowed to graze on public lands where they could come into contact with bighorns.

Pneumonia continues to bedevil Montana’s bighorn sheep, with a herd near Anaconda becoming the latest victim of the epidemic.

More than 300 wild bighorns lived in a 133-square-mile area of the Flint, Anaconda and Pintler mountains. Motorists frequently saw them along Highway 1 between Anaconda and Georgetown Lake.

But only a third of the herd is likely to survive the winter, said Ray Vinkey, Montana Fish, Wildlife and Parks biologist.

“It’s a real shame,” Vinkey said on Tuesday. “We had hoped Anaconda was going to be able to dodge that bullet.”

The contagious respiratory disease is almost always fatal to the animal that catches it. It also tends to kill the lambs of surviving herd members for years after an outbreak.

Pneumonia outbreaks occurred in other states last winter, including the Yakima area of Washington.

The Anaconda herd had similar die-offs in 1991 to 1992, when 54 percent of the animals died. Another 19 percent were lost in 1993, and lamb counts were far below normal in 1994 and 1995.

FWP had some success last year when a similar outbreak ran through bighorns in the East Fork of the Bitterroot by aggressively culling 77 sick sheep before they could spread the infection to others. Vinkey said that strategy was attempted in the Anaconda area, but the different terrain frustrated the effort.

The first sick Anaconda sheep was reported on Aug. 20. At that time, the herds were high in the mountains and hard to find. Nevertheless, FWP agents were able to cull 44 sick animals and found three more already dead.

But by the time the herd moved to its more accessible winter range, Vinkey said the disease was too widespread for culling to be effective.

Pneumonia outbreaks in the Rock Creek drainage and north of Bonner last winter killed about two-thirds of those herds. FWP culled almost 100 of the Bonner sheep. A similar plan was considered for the Rock Creek area, but dropped because there was no way to separate healthy and unhealthy bands.

FWP Region 2 wildlife manager Mike Thompson said culling remains a good tool, but one that requires special circumstances to work.

Pneumonia chips away at bighorns

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