MISSOULA – A pneumonia outbreak that killed about half the bighorn sheep around Bonner and Rock Creek this winter has left biologists with much to ponder, hunters with fewer opportunities and scavengers with plenty to eat.
“What was amazing to me was how lethal this outbreak was and how fast it spread,” said Ray Vinkey, a wildlife biologist with the state Department of Fish, Wildlife and Parks, who monitored the outbreak in Rock Creek.
Biologists tried several ways of dealing with outbreaks this winter. FWP wardens and biologists shot 95 sick sheep in the hills north of West Riverside, they let the disease run its course in Rock Creek while in November near Darby, FWP officials killed 77 infected sheep.
Aerial surveys found 50 percent of each herd is still alive, but Vinkey said the agency won’t draw any conclusions about the effectiveness of its culling operation until a few more annual population surveys are done.
“Not all die-offs are the same,” he said. “It can be a really bad bug that will wipe out everyone and be over. Others have bacteria that linger. We don’t know if we lose 50 percent and it’s over, or we lose 50 percent and it lingers. So what we’re really looking to see this spring is what our lamb crop is going to be.”
Lamb survival often plunges for years after a pneumonia outbreak. Baby lambs appear to have immunity while nursing, but lose it soon after they’re weaned. If the bacteria remain present in the herd, it can kill lambs for a long time after the original die-off, he said.
Because of the die-off, FWP spokesman Ron Aasheim said the agency has canceled all bighorn sheep hunting around Rock Creek and Bonner and will issue only one permit near Darby.
The die-off led to easy winter meals for scavengers.
“We’ve got a lot of fat coyotes and golden eagles out there,” Vinkey said, adding that he also spotted mountain lions near sheep carcasses.