Rocky Mountain bighorn sheep

While the classic image of Rocky Mountain bighorn sheep is of them in craggy ranges of the Rockies, populations thrive east of the Divide into Midwestern states, and in Montana some of the largest populations are found in the Missouri River Breaks.

Scott Hemmer, Fish, Wildlife and Parks Region 6 wildlife biologist, said that hunting district 680 that stretches north of the Missouri River across Chouteau, Blaine and Phillips counties has regular sheep counts of around 450.

"We're generally not counting all the sheep, so we probably have more likely 6, 700 sheep down there," he said.

"It's one of the more productive (herds)," he added. "It's a little bit more recently reintroduced than some places in the state, but now that's probably one of the bigger herds in the state."

South of the Missouri, Fergus County's hunting district 482 has up to about 450 sheep, he said.

The Missouri River Breaks offers plenty of suitable terrain for the bighorn sheep, he said.

"On that steep habitat, how they can not just stand there but also run up and down some of that stuff is pretty impressive," he said. "... Historically, there was sheep in these areas, but they were extirpated at some point historically, there were no longer any sheep in the Breaks."

History

Heavy commercial, unregulated hunting and agricultural encroachment cut the bighorn sheep population in the U.S. to about 20,000 head by 1940, the National Park Service website said, but by the early 1920s the badland bighorn sheep, also called the Audobon bighorn sheep, was extinct from states like North Dakota, South Dakota and Nebraska.

Translocation of Rocky Mountain bighorn sheep started in the 1920s to the northern Badlands of North Dakota, and sometime after that to Black Hills of South Dakota and Panhandle area of Nebraska, each states' websites said. This, coupled with conservation efforts, has rebuilt sheep populations enough to allow for very limited hunting in those three states.

Bighorn sheep have been transplanted into historical ranges in the Breaks and other areas with suitable habitat in the eastern part of the Montana, including a herd the Chippewa Cree Tribe transplanted to and actively monitors on Rocky Boy's Indian Reservation in the Bear Paw Mountains.

Hemmer said bighorn sheep had been transplanted into the Breaks different times in the 1900s, also, but the herds didn't take off until the last introduction sometime around the 1980s. There's no clear reason why the last herd thrived and others didn't, he added, but they may have benefited from sheep left over from earlier transplant efforts with established territory and habits.

The population has remained pretty much disease free, as well, he said, and that helps.

Herd health

As part of an overall sampling in the state, Fish, Wildlife and Parks recently completed a study in which some of the sheep in district 482 had tracking collars attached to collect data on travel patterns, disease risk and causes of mortality. The district 680 population has had some regular captures for health surveys, he added.

"There's a lot of different pathogens, different bugs that can cause pneumonia. That's the big risk in bighorn sheep," Hemmer said. "... Sometimes you may get a bad pneumonia outbreak and you may lose half the population, they die within a year or two, then there's some areas that they don't ever seem to kind of totally kick it. All the animals aren't dying, but the lambs every year, you have very poor lamb production. The lambs don't seem to make it."

Some herds, not necessarily in Montana, have the disease hang on for 10 to 20 years, he said, and management of these populations is one of the big research questions surround bighorn sheep in North America.

In Montana, the Tendoy sheep population near Dillon, devastated by chronic pneumonia, was down to something like 15 to 25 sheep, he said, so FWP held a liberal hunting season and then worked of the next few years getting all of the sheep out of the area. Just last year, the state started reintroducing sheep into the area.

But this isn't a workable solution for areas with sheep populations that can reach into the hundreds.

"What some other states have started doing now is (operate under) the theory that the reason they never fully kick it is that there are some chronically sick ewes that they call super spreaders," Hemmer said, "They don't get really sick but they keep spreading it."

In these areas biologists are capturing and testing several sheep, sometimes multiple times, and if a sheep comes back positive on multiple occasions for one of the pathogens, most likely the Mycoplasma ovipneumoniae bacteria these days, he said, that animal will be removed from the herd. And this testing and culling continues until they herd health becomes stable.

Some of the early research looks promising, he said, with signs of success.

This can be an expensive and labor-intensive management choice, Hemmer said, but there's really no simple solution to this type of problem.

Preservation of large, established sheep populations is a major selling point for solutions because the sheep bring in tourists and the hunting licenses are coveted by residents and non-residents alike.

Hunting

Rocky Mountain bighorn sheep are relatively large among the species. Older rams can exceed 300 pounds with ewes staying about half that weight. The large curled horns of the rams coupled with the challenging hunting terrain make them a coveted prize among hunters.

District 680 offers more bighorn sheep tags than any district in the state, Hemmer said, and it and district 482 are two of the most popular if counting the number of people who apply for the available tags.

District 680 has an annual draw for 25 either sex tags and 80 ewe tags, while 482 offers 20 either sex and 20 ewe tags. Archery-only season in both districts runs Sept. 4-14, and general hunting season from Sept. 15 to Nov. 28.

Hemmer said an average of about 95% of ram tags get filled annually, but generally around 40 to 50% of ewe tags are filled, though these numbers vary a little bit from year to year.

In 2020, the FWP website says, 25 rams and 28 ewes were harvested in district 680 and 20 rams and 15 ewes came from 482.