Protecting Colorado’s bighorn sheep herds requires extraordinary effort by Colorado Parks and Wildlife biologists, officers and staff and volunteers

EDITOR’S NOTE: Tag along as Colorado Parks and Wildlife biologists, wildlife officers, a CPW commissioner, other CPW staff and volunteers ascend mighty Pikes Peak in the dark of night to begin daylong hikes circumventing America’s Mountain at various altitudes in search of Colorado’s state mammal, the Rocky Mountain bighorn sheep.

The CPW team makes this grueling expedition twice a year as part of the agency’s intense efforts to perpetuate and expand the state’s bighorn sheep population. A century ago, bighorn sheep were on the brink of extinction due to unchecked hunting pressure from pioneers and miners, habitat loss and from disease-causing pathogens carried by domestic animals.

The Pikes Peak herd, as it’s known, is particularly important as it is one of just a dozen or so historic herds that have spanned the eons without human intervention. CPW is committed to ensuring this herd, and the dozens of others it has helped resurrect statewide, will survive and thrive in the face of Colorado’s exploding human population.

On Aug. 10, I rose groggily from my bed at 2 a.m. to join 43 others –  17 staff and 26 volunteers – at Colorado Parks and Wildlife’s Southeast Region Office in Colorado Springs for the annual bighorn sheep count on Pikes Peak, held on two days every summer for the last 35 years.

But this is no routine biological exercise. Much is at stake for Colorado’s bighorn sheep herds and the Pikes Peak herd, in particular, in the face of increasing pressure from the state’s growing human population and the demands of outdoor recreation.

Bighorn sheep nearly succumbed, a century or so ago, to unregulated market hunting  and from the introduction of domestic animals and the diseases they brought into the state. Keeping a close eye on Colorado’s state mammal (and the proud symbol of CPW) is one of the pillars of the agency’s terrestrial biology work.

Against that backdrop, wildlife officers, staff and volunteers gathered that chilly morning outside the office in the dark, drinking coffee and grabbing the manila folders from CPW Area 14 Wildlife Biologist Ty Woodward. Each packet held trail maps and data collection directions to help them classify the sheep they spotted that day. CPW biologists have established about 10 hiking routes on Pikes Peak designed to offer staff and volunteers the best opportunities to observe most of the summer sheep habitat on the mountain while minimizing duplicate sightings.

“We’re not counting all of the bighorn sheep in the population,” Woodward explained. “We are surveying them and classifying (keeping track of males, females and young) the bighorn we observe. The goal is to observe and classify a representative sample of the whole population. We do count the total number observed for the day.”

It’s an important distinction. It would be simple to just count bighorn. Woodward and his team are doing a more sophisticated survey. They look at demographic ratios that measure the health of a population. They study lamb-to-ewe ratios. They work to establish an age ratio for the herd.

“We look at how many yearlings to ewes we have to see how many individuals were ‘recruited’ into the adult population,” Woodward said. “And the sex ratio, the number of males to females. That tells you how the herd is doing in general.

“And it can clue you in if something is going on. We want to know if we have variables that are causing reductions in the herd and issues with overall herd health.”

Around 3:30 a.m., the CPW caravan left for the mountain. I loaded into an agency Jeep with Woodward, Area 14 Wildlife Manager Tim Kroening, and new CPW Commissioner Jessica Beaulieu.

With Woodward at the wheel, we drove west up U.S. Highway 24, following the same path Native Americans – especially the Ute Indians – used to traverse the pass in the 1800s. Then we headed up the Pikes Peak Highway toward the mountain’s 14,115-foot summit.

gathering on the mountain at dark

We had been assigned the route known as West Beaver Ridge – an approximately 4.5-mile loop route that would give us excellent views of Pikes Peak’s south slope. The route also provides a great view of Wilson and Bighorn reservoirs, the Pikes Peak Highway, Devil’s Playground and an area within it that staff and volunteers have taken to calling “the Nursery” because it’s a place where the lambs and ewes always hang out.

There is a group of ewes (called a “ewe band”) from this area that has been migrating to Dome Rock State Wildlife Area for years – more on them later.

“West Beaver Ridge is a great route because it’s very central,” Kroening said. “And we get a panorama view that gives us a look at a lot of the other hiking routes.

“I like West Beaver because we typically see a fair amount of animals. It’s also a security blanket route. Because it overlaps with other routes, it helps us get a good count before other hikers get in close and maybe spook the bighorn off.”

The CPW team dispersed to find their trailheads. They parked, turned on their headlamps and hiked off into the dark so they’d be in position to see bighorn when the sun pierced the eastern horizon.

Our West Beaver Ridge group waited a few minutes in the cold, watching the fiery sunrise at 13,000 feet, then started our hike.

Sunrise from Pikes Peak
Sunrise from Pikes Peak

Woodward and Kroening were excellent hosts as they taught us how to classify bighorn (ram, ewe or lamb) and how to size the curl ratio on rams (full, three-quarters, half, etc.). They also helped us find the bighorn hiding in plain sight on the mountainsides. They blended in so well with the Pikes Peak granite outcroppings and high alpine tundra.

They also explained all the moving parts behind the scenes of the annual bighorn sheep count. It requires cooperation with multiple partner agencies: the U.S. Forest Service, Colorado Springs Utilities, the City of Colorado Springs, the Pikes Peak Highway, the Cog Railway and The Broadmoor, the City of Cripple Creek and the City of Victor.

They all contribute to the success CPW has on the mountain each year. Perhaps because of all the interests and entities at play on America’s Mountain, the day was full of adventure, and there were many small moments that seemed to encapsulate the challenges of balancing conservation and recreation in Colorado:

  • Woodward left our group for a few minutes to talk with some young adults who were out on the mountain early. He wanted to make sure they were aware of where they were hiking and nearby private land boundaries.
  • Woodward told a funny story about an earlier survey this summer when he was charged by a marmot, which, he suspected, “might have been looking for Cheetos. I highly doubt that he hasn’t had a Cheeto before.”
  • Another group spotted a bear near the Pikes Peak Summit House; the animal was likely trying to get a human food reward.
  • An employee of the Pikes Peak Highway had to chase off people who were approaching a group of five bighorn sheep at the side of the highway.

At the end of the day, our group had seen about 50 bighorn, including one large group of 32 spread out on the slope beneath the highway.

But other CPW hikers weren’t so lucky. Many only saw a handful of bighorn. In all, the team reported viewing fewer than half the approximately 100 bighorn that are normally seen on this count.

That lack of visibility concerns Woodward. And there are bigger issues on the mountain that trouble CPW experts.

“I’ve done that count every year since I was a local DWM in Teller County in 2015,” Kroening said. “I’ve been on just about every single route, many of them multiple times. The fact is, we’re just seeing fewer lambs and recruitment into that population, especially this year.”

Fewer lambs signals big trouble.

Lambs are the Key

bighorn sheep

“We’re keeping track of lambs, seen and observed,” said CPW Terrestrial Section Manager Brian Dreher. “In the bighorn sheep realm, lamb survival is very much an indication of health or disease-related issues. Lamb productivity gives us some overall picture of herd health.

“When disease outbreaks occur in these populations, we see a loss of lambs throughout the summer months. In some counts, we’ve seen lambs on their deathbeds.”

Where CPW finds the bighorn on the mountain – their distribution – also is important data, Dreher said.

Bighorns face a variety of threats (increased recreation pressure, habitat fragmentation, etc), but the primary threat to bighorns in Colorado are respiratory pathogens that can result in pneumonia outbreaks in wild bighorns. One source of pathogen transmission can be through commingling with domestic livestock. Pneumonia infections can result in acute all-age die-offs in bighorns, or more frequently, chronic low-lamb survival, as the adults can often survive it but the lambs cannot.

CPW biologists have had an eye on the Pikes Peak herd and have been closely monitoring for disease. The migratory behavior of the ewe band from Devil’s Playground that migrates down every year to “lamb” (give birth and raise their young) on Dome Rock State Wildlife Area also creates concerns for disease transmission.

Woodward said monitoring the population of the Pikes Peak herd has provided good lessons in how fragile populations are.

Ty Woodward, Commissioner Jess Beaulieu and Tim Kroening scan the landscape looking for bighorn sheep.
Ty Woodward, Commissioner Jess Beaulieu and Tim Kroening scan the landscape looking for bighorn sheep.

“We historically had numbers much higher than we have today,” Woodward said. “Portions of that population have seen significant decline over the years. Until recently it had a pretty stable population on Pikes Peak proper. That herd includes an historically migratory section of the population. We don’t see that a ton anymore, where some of the herd migrates annually for reproductive purposes. That segment of the population used to be much stronger and there used to be many more sheep in that group. In the past decade, that group has been on a decline where there’s not too many sheep left that do that still. The concern on my end: once we lose that migratory behavior in the herd, then it’s gone forever. We won’t be doing like we do with geese where we teach them to migrate.”

“The migratory behavior is really unique,” Kroening said. “We don’t know exactly why they started it. Maybe life is a little easier down there. But when they go down, they’re more likely to come into contact with domestic sheep or goats. We have a lot of different hobby and small-flock farms and ranches in the area. The concern is that our wild sheep can actually get bacteria from domestic sheep or goats. That happens during a nose-to-nose interaction or if the domestics sneeze, it can infect another animal that way. But it’s from their intermingling.”

Woodward said the migratory behavior does create disease concerns for the herd.

“Around Pikes Peak we do have a lot of small-scale farms that have a handful of sheep or goats, but they’re not so large that they get noticed. That creates a problem because they’re a hidden problem we can’t see and we don’t know it exists. We only find out about it when one of our officers is out there driving around and sees those animals. That’s a problem. It’s a little bit harder from a risk management standpoint to address those issues than large grazing allotments you see in some areas.”

The Pikes Peak herd is no stranger to disease. The first documented disease related die-off in the Pikes Peak herd began in the fall of 1952 and took a heavy toll during that winter and spring, when “verminous pneumonia” (the lung nematode Protostrongylus stilesi) was found to be the culprit. Wildlife biologists monitor the herd closely. Biologists have detected pneumonia a couple different times more recently in the herd. One was from a sheep hit by a car and killed on the highway.

“The other one we had to euthanize last year on the sheep count when we saw that it was sick,” Kroening said. “That sheep was from the ewe band and typically hangs out on Devil’s Playground. Our pathologist documented pneumonia in her tissues after she died. It does definitely seem like we’ve had an increased amount of pneumonia in this population. They can spread it to each other, so it’s possible that the whole herd on Pikes Peak is passing this back and forth.”

Kroening said there have been small victories during his tenure with CPW, which started back in 2014. While still a DWM in Teller County, Kroening worked with the Rocky Mountain Bighorn Sheep Society to get a $10,000 grant for a secondary fence that would create a 5 – 10 foot buffer between wild sheep and domestic goats.

“That was a big area where that landowner worked with us,” Kroening said. “Kudos to him on being conservation minded and wanting to protect the bighorn sheep to allow us to put up a secondary fence on that property.”

“When our wildlife managers identify problem spots, they work with landowners to create separation,” Woodward said. “That’s the best thing we can do. We don’t have vaccines that work at the efficacy rates that would be necessary. Separation is the best thing that we can do.”


bighorn rams
The Pikes Peak herd, as it’s known, is particularly important as it is one of just a dozen or so historic bighorn sheep herds that have spanned the eons without human intervention.

Despite its iconic status and current prominence, the bighorn sheep was near extinction at the turn of the century. Unregulated hunting and diseases introduced through European livestock had decimated populations throughout the West, and only a smal​​​​​l number of​​ the native bighorn sheep remained in Colorado in the early 1900s.

CPW has led the effort to restore bighorn in Colorado, along with its partners. In cooperation with organizations like the Rocky Mountain Bighorn Society, CPW has spent decades rebuilding bighorn populations through trapping and relocation efforts.

CPW conducted the first bighorn sheep transplants in the 1940s, including planting bighorns between Georgetown and Silver Plume. Known simply as the “Georgetown Herd,” this population of 250-350 sheep is one of the largest herds in the state and the area has become one of the most popular bighorn viewing sites in the nation.

Since Colorado’s restoration efforts began, CPW has completed more than 100 bighorn sheep transplants, most of which took place in the 1970s and 1980s.

Gore Canyon in northwest Colorado is one of the most recent transplant locations.

CPW closely monitors bighorn sheep herds and maintains healthy populations through controlled hunting and ongoing trapping and relocation. Thanks to decades of dedicated conservation efforts, Colorado’s iconic bighorn sheep are once again abundant with an estimated statewide population of 7,000 animals, although bighorn populations are not at the levels they were before European expansion.

That’s why the work CPW does isn’t just about transplanting animals.

“There’s no doubt that bighorns are not at the numbers that were here when settlement occurred,” Dreher said. “It’s one of the only big game animals we haven’t been able to recover to the population levels we’d like. It is an extremely complicated issue because of disease.”

Andy Holland, CPW’s Big Game Manager, said it’s not as simple as growing bighorn sheep herds to a stable level.

“We have robust bighorn sheep management, research and disease programs and our hunting licenses are extremely regulated and get more scrutiny per license than any other species in the state,” Holland said. “The conundrum with bighorn sheep is: the larger a  population gets, the more likely it is to have a disease event.

“This is because as populations get larger, they are more likely to come into contact with domestic sheep and goats and densities of bighorns are higher so respiratory pathogens spread more quickly.”

Holland said the most important factor in bighorn sheep health is to maintain separation between bighorn sheep and domestic sheep and goats on the landscape.

“It doesn’t mean that people can’t have grazing allotments or private flocks,” Holland said. “But the idea is to not have them together in the same place with wild bighorns.”


Concern about infectious disease transmitted to bighorn sheep was echoed by CPW Wildlife Health Program Supervisor Mary Wood.

“Respiratory disease is one of the biggest challenges to growing bighorn populations in much of the West,” Wood said. “It’s a challenge across all of their range.”

CPW actively surveys for respiratory disease in Colorado’s bighorn populations in a number of ways. CPW biologists test bighorn sheep during capture and collaring efforts, and they also test bighorn when they find one that has died.

“Our biologists on the ground make bighorn sheep surveillance a priority,” Wood said. “And if a bighorn is hit by a car, they’ll try and collect samples for us. They send them to us at our Wildlife Health Lab in Fort Collins where we can run tests for a number of those pathogens. A lot of our diagnostic tests were developed in our own laboratory.”

Wood said CPW is constantly monitoring for the occurrence of multiple pathogens and much more.

“We do a lot of research on bighorn sheep and respiratory disease,” she said. “We’ve looked at vaccines, bacterial targets for management applications, nutrition and parasites.”

And CPW will keep researching until successful management strategies are found.

“We don’t have any golden ticket so we are developing tools for management of disease,” she said. “Unfortunately it’s terribly complicated; there are multiple pathogens involved in the respiratory disease complex – we call it polymicrobial.”

Other factors influencing bighorn respiratory disease could include habitat, predation and climate.

“That’s the real struggle with bighorn sheep,” Wood said. “There are multiple bugs and multiple other things going on. It makes trying to find one clear-cut management strategy a pretty big challenge. We hope to eventually have multiple tools to address it, but there’s not likely to be a one-size-fits-all solution.”

A Tough Problem

As Wood and her team work in the lab, people like CPW’s Kroening try to protect bighorn sheep by patrolling local domestic animals and talking with “hobby farmers and ranchers” about the critical importance of maintaining control of their goats and sheep.

“It’s frustrating because we just can’t get to them all,” Kroening said. “There are so many other landowners who may have a few domestic goats or sheep. And they get out of their pens. We need these folks to understand that a domestic animal mingling with wild bighorn sheep can easily transmit pathogens and wipe out a legacy herd like the bighorn on Pikes Peak.”

It’s a problem common across the West. Many different state wildlife agencies and organizations like the Bighorn Society are working to see what’s the best solution to this issue.

“We all want to figure out how to prevent disease-causing pathogens from spreading and killing an entire population of bighorn sheep,” Kroening said. “The solution will be working together and collaborating on the issue.”

Recreation and tourism present a similar challenge that requires a delicate balance.

“Each year there are more and more people in the mountains recreating,” Woodward said. “Pikes Peak is a great example. They have the highway and the train. We routinely encounter people hiking, often off trail, on our dawn survey hikes. There are more mountain bikers and off-trail use. It’s becoming a really big issue up there.

“Besides educating ranchers, we need to educate the public, the tourists, just how critical it is for them to help us protect the bighorn,” Woodward said. “We must find a way to co-exist or future visitors may not have a bighorn sheep herd to observe here.”

What is CPW doing?

viewing bighorns through spotting scope

Besides all the research by Wood and her team, the intense biological surveys and management in the field by Dreher’s team and Holland’s focus on regulated hunting, CPW is attacking the issue in a variety of other ways, too.

  • CPW has been working with the Western Association of Fish and Wildlife Association’s Wild Sheep Initiative for more than 20 years. This working group brings together 24 state fish and wildlife agency directors and organizations.
  • CPW is heavily involved in commenting on federal land management. CPW recognizes the increasing desire for outdoor recreation, but advocates for ways that minimize the impact to the natural resources, including wildlife.
  • On the education front, CPW is working to identify private property small flock operators to talk to them about the issue of respiratory disease transmission. The lack of separation between wild and domestic sheep is the biggest issue.
  • Habitat development is another critical area to improve bighorn sheep range. The agency is thinning forests or using prescribed fire to create the open landscapes bighorn sheep need to avoid predation. If an area is too timbered, bighorn can more easily be ambushed by mountain lions.
  • Finally, CPW engages in intensive Herd Management Planning projects using the coordinated ground surveys and extensive helicopter inventory flights.


Despite all the concern, there is optimism within CPW that the multi-pronged approach will pay off in healthy bighorn sheep herds protected from disease and offering hunters and wildlife watchers recreation opportunities well into the future.

“I firmly believe in our strategy and everyone here is committed to perpetuating our beloved bighorn sheep,” Dreher said. “We just need everyone to help us. And I’ve seen Coloradans come together to protect our wildlife.”

Additional bighorn sheep resources can be found on the Colorado Parks and Wildlife website:

Video: ‘Livin’ the Wildlife’ – Bighorn Sheep in Colorado

Travis Duncan

Written by Travis Duncan. Travis is a public information officer for Colorado Parks and Wildlife in Denver. He has lived in Colorado for nearly 20 years and loves the outdoors.