Colorado’s iconic bighorn sheep face pressure from disease, drought and habitat loss, wildlife officials told the Colorado Parks and Wildlife Commission Thursday.
CPW Big-Game Manager Andy Holland and veterinarian Peach Van Wick briefed commissioners on the status of Rocky Mountain and desert bighorn sheep, outlining decades of conservation work and future challenges.
“We are currently monitoring all age die-offs in this whole northern front range. There’s currently co-infection with three pathogens there,” Holland said. He pointed to stretches near Estes Park and Loveland and west to Clear Creek County.
In northern Colorado, CPW-funded work shows a strain causing deaths across all age classes, while a different strain southeast of that area mainly affects lamb survival and leads to poor recruitment.
Later, commissioners considered changes to hunting regulations and quotas in response to disease impacts.
The agency has hundreds of staff monitoring sheep habitat, herd health, research and harvest management. For desert bighorn sheep, hunting is tightly controlled, with only about 15 ram licenses issued statewide each year. About 225 Rocky Mountain bighorn ram licenses were issued this season.
“Bighorn sheep are a species of greatest conservation need in our SWAP, which is our state wildlife action plan, and Rocky Mountain bighorn sheep are on CPW’s logo, our seal, our patch,” Holland told the commissioners.
“These are all for good reason. Rocky Mountain bighorn sheep are a majestic symbol of the Rocky Mountains themselves,” he said.
The separate species of desert bighorn sheep live primarily in deserts and canyons, breed in summer and lamb in winter. The agency has a management plan for those roaming the Dolores River Canyon, reintroduced in the mid-1980s.
Last year’s post-hunt numbers show 185 desert bighorn sheep in the river corridor across Montezuma, San Miguel and Dolores counties – about 10 more than 2019 estimates. Roughly 500 desert bighorns occupy canyon regions in Southwest Colorado, and Holland said these populations are stable.
All bighorn sheep are managed by local plans similar to other big-game species.
Rocky Mountain bighorn populations hover around 7,000 to 7,500 animals but face threats from extreme weather, selenium deficiencies and, most concerning, respiratory infections linked to bacteria.
“These animals are still fighting an uphill battle due to land disturbances, invasive grasses, climate change and disease. While all these issues are equally important, disease has the potential to have a large, negative impact in a short period of time,” Van Wick said.
Van Wick said one respiratory disease has researchers and conservationists particularly concerned: Mycoplasma ovipneumoniae, whose pneumonia-causing agents can lead to immediate mortality and lasting effects.
“I feel like I was placed on the agenda after lunch for a reason. You probably can’t have a wildlife vet come speak to you without showing pictures of sometimes not pleasant things,” she said, thumbing through photos of ear infections, sores and skin diseases that she said are incredibly painful and sometimes stop animals from nursing or eating.
She continued, saying respiratory diseases in bighorn sheep have evolved among several pathogens, and there’s likely to be “more and newer, and bigger, and badder” ones in the future.
“The last one, Mycoplasma ovipneumoniae, is a different beast altogether. It causes pneumonia. What happens especially whenever an adult continues to carry this pathogen and shed that bacteria, they continue to infect lambs. So, this is a bacteria that is really hard on lamb populations,” she said.
Van Wick said respiratory diseases are likely the biggest threat to bighorn sheep, but not the only one.
Other health concerns include invasive grasses that reduce nutritious forage, skin diseases such as mange and contagious ecthyma, gastrointestinal illnesses like Johne’s disease and hemorrhagic viruses.
Holland added that contact with domestic sheep and goats on federal grazing land on the Western Slope, small private flocks and pack goats remain key pathways for pathogen transmission. When respiratory disease enters a wild herd, it can spread between neighboring groups and persist for decades.
“Once the genie is out of the bottle, these pathogens move through herds. The larger the herd becomes, the more likely it is to come in contact with other herds or domestics,” Holland said.
Commissioners asked whether vaccines or treatments are available. Van Wick said no effective vaccine exists yet for Mycoplasma for domestic or wild sheep, and while one oral antibiotic helped treat and clear infection in captive animals, the weeks-long dosing schedule is not feasible for free-ranging herds.
To fund research, monitoring and habitat work, CPW relies heavily on revenue from two statewide bighorn ram licenses auctioned and raffled each year, which generated about $1.3 million for bighorn projects in 2025 and is matched by nearly equal outside funding.
“We rely heavily on helicopter capture and GPS collaring for a variety of research and management needs with bighorns. These are extremely expensive; they cost several thousand dollars per animal. That’s why these funds are important,” Holland said.
Helicopters run about $1,500 to $2,000 an hour, with “costs just continuing to go up,” he added.
