There are roughly 6,000 bighorn sheep in Montana and wildlife officials fear that nearly 700 of them could be dead by the time a pneumonia outbreak runs its course.
And Montana isn’t alone. Bighorn sheep pneumonia cases have been reported in Utah, Washington and Nevada. Biologists say such a widespread outbreak is rare and the cause is still unknown, though pneumonia in wild bighorn sheep has often been linked to contact with domestic sheep.
State biologists hope that research stemming from the outbreak will help them better understand how bighorn sheep get pneumonia, how it affects them and what can be done to discourage future incidents. All of the affected sheep in Montana have been found in four herds in west-central Montana surrounding Missoula.
Mike Thompson, wildlife manager for FWP’s Region 2, said the infected sheep that have been harvested by his agency are being studied.
“It may be an unprecedented sampling,” Thompson said.
Since last November, Montana Fish, Wildlife and Parks has documented 220 bighorn sheep deaths – either caused by pneumonia or killed by FWP because they were infected – in the West Riverside herd around Bonner and the East Fork of the Bitterroot herd near Darby.
Officials from FWP removed sickened sheep from those herds in an effort stop the illness from spreading. Thompson believes the rest of those herds should be in good shape.
“We can only hope about the future, but as it appears right now it appears to be contained,” Thompson said.
But herds in the Upper Rock Creek and Lower Creek areas, which number 340 and 200, respectively, have been left alone to let nature run its course. Pneumonia can kill up to 80-90 percent of infected bighorn sheep and they often die within days.
“There are untold animals dying at Rock Creek,” Thompson said.
Montana’s bighorn sheep populations have been hit hard by pneumonia before, including in 2008 when an estimated 200 sheep – or about 90 percent of the herd – died in the Elkhorn Mountains near Helena.
In the early to mid-90s, herds around Butte and Anaconda were stricken with pneumonia, said Jim Weatherly, executive director of the Montana Wild Sheep Foundation. The “highland herd” near Butte, Weatherly said, was decimated and never came back.
The recent outbreak and its accompanying death toll, however, appear to be unprecedented for Missoula and its surrounding regions.
“Never seen this in this region,” Thompson said. “It’s the largest event we’ve had in west-central Montana ever that anyone’s recorded.”
But Northwest Montana has so far “dodged that bullet,” said FWP Region 1 biologist John Vore. And it appears the region should continue to dodge that bullet, according to Neil Anderson, a lab supervisor for FWP.
Because of distances, the herds in Sanders County, Lake County and elsewhere in the region don’t have contact with the infected herds. Also, Vore points out, there aren’t a lot of domestic sheep in the region, except for hobby farmers.
At his Bozeman lab, Anderson has been busy examining blood and tissue samples from sheep harvested by FWP. He hasn’t determined if contact with domestic livestock is the cause – domestic sheep have built-in immunities, but wild sheep are ravaged by pneumonia. Anderson said pneumonia can spread from nose-to-nose contact or simply by close proximity. Bighorn sheep have been known to mingle with domestic sheep.
“We’re looking at contact with domestic sheep and evaluating if that’s the cause,” Anderson said. “If not, then we’ll determine if pathogens were present before this outbreak.”
“(Pneumonia) has the potential to decimate a whole herd of bighorn sheep,” he added.
Samples were also taken from 41 sheep that were transported on Feb. 26-27 from Wild Horse Island on Flathead Lake to locations in Sanders and Lincoln counties. But the sheep transportation had nothing to do with pneumonia and, on the contrary, everything to do with how healthy that sheep population is.
The Wild Horse herd is considered one of the most unique and robust sheep populations in Montana and beyond. More than a half-century ago, sheep were planted on the island, Vore said. In recent years, in the absence of consistent predators, the herd has boomed to more than 200. Seventy-five to 100 is optimal, Vore said.
To bring down the population, FWP transported sheep off the island in 2008, then again in February and will do so again next year. Wild Horse Island is a state park.
Wild Horse Island’s herd has been used as a nursery herd to supplement other populations in the past. While FWP officials say it could be used to replenish the stricken herds of west-central Montana, that wouldn’t happen for years down the road.
“We’re looking at perhaps the possibility of supplementing, but we have to wait to see if the (pneumonia) carriers who have survived aren’t still around so they don’t infect others,” Thompson said. “We can’t do it anytime soon.”
According to FWP’s Bighorn Sheep Conservation Strategy, approved in January, there are roughly 5,700 wild sheep in Montana excluding Yellowstone and Glacier national parks. That total is divided into 45 identifiable populations, 36 of which have limited hunting allowed.
Weatherly, of the Montana Wild Sheep Foundation, said Montana has one of the largest bighorn sheep populations in the nation, along with Wyoming and Nevada. Weatherly’s organization promotes wild sheep management and education and worked with FWP to transport the Wild Horse Island sheep.
The sheep foundation encourages hunting as a management tool and closely monitors poaching. With a limited number of sheep licenses available each year, Weatherly said “there a lot of problems with poaching.” His organization offers up to $1,000 for information about poaching.
“We are strong about wildlife management through hunting,” Weatherly said. “Hunters’ dollars fund management traditionally.”
Sheep hunting will be virtually nonexistent in the Missoula area when the season opens up in September, Thompson said. Region 2 is divided into four hunting districts. In the past, each district has offered about five to 10 either-sex sheep licenses and 10-20 ewe licenses, he said.
This year, three of the four districts will be closed to hunting, while one either-sex license will be allowed in the East Fork of the Bitterroot, Thompson said.
“Bighorn sheep hunting is big here,” Thompson added.
In any case, Weatherly sees a bright side to it all. He said the rapid response to the East Bitterroot herd in November salvaged much of the population.
“I don’t know at what point you define success,” Weatherly said. “But if you save half a herd, based on past experience, I would definitely say it’s a success.”