Baker County’s biggest herd of bighorn sheep is getting, well, bigger.

The burgeoning herd of Rocky Mountain bighorns, which roams the eastern part of the Lookout Mountain unit near the Idaho border, is a bright spot for a species that is struggling in some other parts of the state.

Fatal pneumonia, which bighorns can easily contract when they mingle with domestic sheep or goats, has affected herds of both types of bighorns that live in Oregon — Rocky Mountain and California (or desert).

And once the bacteria that causes pneumonia has infected a herd of bighorns, the sheep can spread the disease to other bighorn herds.

California bighorns, which is the smaller subspecies, generally live in Southeastern, Central and North-Central Oregon. There are about 3,500 of the animals in the state.

Rocky Mountain bighorns, which number about 800 in Oregon, are confined to the northeastern corner of the state, with the Lookout Mountain herd the most southerly.

That herd also is the state’s largest and healthiest bunch of Rocky Mountain bighorns, said Justin Primus, assistant district wildlife biologist at the Oregon Department of Fish and Wildlife (ODFW) office in Baker City.

“The herd has been growing each year,” Primus said.

Based on a helicopter survey that Brian Ratliff, district wildlife biologist at the Baker City office, did in November, the Lookout Mountain herd totals 247 sheep, including about 50 rams.

That’s up from 228 sheep the year before.

That growth has happened in part because the herd, so far as biologists can tell, has not been exposed to domestic animals that can spread pneumonia to bighorns.

Nor have the Lookout Mountain bighorns been infected by other bighorns.

The herd of Rocky Mountain bighorns nearest Lookout Mountain lives near Hells Canyon Reservoir, said Pat Matthews, district wildlife biologist at ODFW’s Enterprise office.

The bacteria that causes pneumonia has been found in bighorns from that herd in Hells Canyon, Matthews said.

The bighorn herd closest to Lookout Mountain is also in Baker County. That’s the California bighorn herd in the Burnt River Canyon near Durkee, which numbers about 100 sheep, Ratliff said.

The Burnt River Canyon herd is free of the pneumonia-causing bacteria, he said.

A more proximate threat to the Lookout Mountain bighorns was eradicated several years ago when ODFW killed the few bighorns that had not yet died from an outbreak of pneumonia in a Rocky Mountain herd that lived near Oxbow, Ratliff said.

Those sheep might well have infected the Lookout Mountain herd, he said.

ODFW has decided not to reintroduce bighorns to the Oxbow area, at least for now, to create a “buffer” for the Lookout Mountain bighorns, Ratliff said.

Pneumonia can rapidly ravage even a large bighorn herd, said Matthews, who has seen that happen to herds across Wallowa County over the past decade or so.

The bacteria has been detected in each of the county’s six herds of Rocky Mountain bighorns, the largest of which, along the lower Imnaha River, numbers about 100 sheep, Matthews said.

“Once they have this bacteria in the herd, they usually continue to have it,” he said.

Although adult bighorns often will survive a bout with pneumonia, the disease can decimate each year’s crop of lambs, Matthews said.

Lookout Mountain herd history

ODFW started the herd during the winter of 1994, when the agency released 24 bighorns along Fox Creek about 16 miles north of Huntington.

Those sheep had been trapped in Montana.

During the ensuing two decades the sheep, even as the population has grown more than tenfold, have not expanded their range substantially, Primus said.

Generally the bighorns still hang around within several miles of that original release site along Fox Creek — mainly from Hibbard Creek north to Quicksand Creek.

Based on the movements of the bighorns fitted with GPS or radio tracking collars, the sheep stay east of Lookout Mountain Road, preferring the steeper country between the road and Brownlee Reservoir, Primus said.

The animals will migrate to lower elevations if the snow gets deep, and they prefer higher, cooler areas during summer heat.

“Sheep in general don’t want to wander very much,” Primus said.

About 20 bighorns from the Lookout Mountain herd are wearing tracking collars. That’s a relatively high number for the size of the herd, but Primus said ODFW officials want to track the herd closely because it could be a key source of Rocky Mountain bighorns to supplant herds that have suffered from pneumonia.

In January 2016, ODFW captured seven bighorns from the Lookout Mountain unit and trucked the animals to the Wenaha area of Washington state, just across the Oregon border, as part of the Hells Canyon Initiative, a project involving state and federal agencies and hunting groups designed to restore bighorn herds in that area.

The Lookout Mountain herd is a coveted hunting area, as well. ODFW issues three ram tags each year, and the two hunters who win the state’s raffle almost always choose to hunt for rams in that unit, Primus said.

The Confederated Tribes of the Umatilla Indian Reservation also hunt bighorns in the unit, typically taking three animals to match the ODFW’s tag count.

Because hunters typically target the biggest rams, the number of those is likely to decline over the next several years, Primus said.

But the current hunting pressure poses no threat to the vitality of the herd as a whole, he said.

Predators

Nor does it seem that predation is a major problem for the Lookout Mountain herd.

A single male wolf has lived in that area for most of the past year, Primus said, but biologists have found no evidence that the wolf has killed any bighorns.

The tracking collar on that wolf failed in June 2016. But ODFW biologists, responding to a citizen’s report, found tracks from a single wolf — likely the same male — last week along the Lookout Mountain Road not far from Interstate 84, Primus said.

He encourages residents who see a wolf in that area to call the Baker City ODFW office at 541-523-5832.

Biologists would like to capture the wolf and replace its tracking collar this winter, Primus said.

Cougars are the main predator preying on bighorns, he said.