Disease die-offs continue to ravage bighorn sheep. Advocates say feds left them ‘high and dry’ on the issue.
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COLORADO SPRINGS, Colo. — The Pikeview Quarry, barely outside of the cul-de-sacs and two-car garages of the Mountain Shadows subdivision, seemed like an odd place to find one of Colorado’s most intrepid species. Bulldozers, excavators and dump trucks crawled the quarry’s terraced slopes, putting the final touches on a mine reclamation effort that began in 2022.
Despite the man-made noise, Colorado Parks and Wildlife (CPW) biologist Ty Woodward spotted a band of eight bighorn sheep grazing the rusty slopes of the quarry.
“Even though you have the machines running around here, there's not a ton of people,” Woodward said.
The quarry — which once provided Colorado Springs with the limestone aggregates needed to make concrete — has become a surprise haven for bighorn sheep, providing the steep slopes, visibility and food they need to survive.
Not all of Colorado’s rocky mountain bighorn sheep have fared this well. Experts estimate that at the start of the 19th century, between 1.5 and 2 million bighorn sheep roamed the mountains of North America. Today, roughly 80,000 remain in the region, with just 7,000 left in Colorado.
Hunting, competition for habitat and diseases carried by domestic sheep and goats decimated the species.
Although Colorado’s bighorn sheep population has stabilized on paper, wildlife officials have failed to “fully restore the species,” said Terry Meyers, the executive director of the Rocky Mountain Bighorn Society.
One of the top threats to the species is a string of respiratory diseases that infect and kill bighorn sheep. Domestic sheep and goats transmit pathogenic bacteria — most notably mycoplasma ovipneumoniae — to bighorns through nose-to-nose contact. While these bacteria are usually innocuous to livestock, they can rapidly develop into deadly cases of pneumonia in wild sheep.
Contact between the two species happens more often than biologists would like. Bighorn sheep are often curious about their domestic cousins and frequently encounter domestic sheep on public grazing allotments that overlap with their habitat.
At least seven bighorn herds suffered from respiratory illnesses in 2023, leading some biologists to declare it the “worst year in over a decade for bighorns in Colorado.” In the past, disease events have wiped out entire herds, and when one band of sheep gets sick, it can be hard to prevent bighorns from infecting other herds.
Although scientists have long dreamed of a vaccine, no such antidote exists.
“The only management strategy to really protect bighorn sheep is separation between bighorn sheep and domestic sheep,” said Meyers. Such separation is easier said than done considering bighorn rams can travel up to 60 miles in search for mates.
State wildlife biologists and researchers who are most familiar with the threat of disease are largely powerless to enact change. Colorado Parks and Wildlife can manipulate hunting licenses, improve habitat or move bighorn sheep, but when it comes to conflicts with domestic sheep on federal grazing lands, it is up to federal agencies to make changes.
According to Meyers, the U.S. Forest Service and Bureau of Land Management, which control grazing permits, have taken a laissez-faire approach to conflicts between bighorn sheep and domestic sheep, rarely completing environmental analyses on grazing allotments.
In many cases, conservation hinges upon individuals and advocacy groups who have pieced together arrangements with ranchers to give up grazing rights in problematic areas and provide more space for bighorns.
Despite the intractability of the problem, wildlife biologists manage and track bighorns as best they can. During a recent field operation at the end of December, Woodward planned to dart and collar a bighorn ewe so that his team can better understand the herd’s movements and behavior.
At the base of the Pikeview Quarry, Woodward and his colleague Corey Adler prepared a carbon-dioxide tranquilizer gun they use to dart the sheep. They must get within 25 to 30 yards for a good shot.
Once the sheep is tranquilized, they secure a GPS tracking collar. Location data from collars help CPW understand bighorn sheep movement and population health. When a collared sheep dies, biologists are more likely to find its body in time to collect tissue samples that scientists can study.
Although the Rampart herd is currently disease-free, CPW regularly monitors the population to ensure it remains healthy. They use this herd to create new herds and bolster ailing herds around the state.
The herd at Pikeview Quarry descended from 14 bighorn sheep that were originally destined for Pike Peak. In 1946, a truck carrying the sheep broke down. The drivers released the sheep near Green Mountain Falls thinking they would make their way towards Pikes Peak, instead, the herd colonized a series of canyons and rocky slopes above the Garden of the Gods.
It didn’t take long for bighorn sheep to become a fixture in the area.
Jerry Schnabel, the president of Castle Aggregates, which operated Pikeview Quarry, said that even rough and tough miners soon developed a soft spot for sheep. Miners with names like “Dozer Dave” would haul water to the top of the quarry to help the sheep survive dry spells, he said.
Schnabel even found invoices for hay the miners had ordered from a local rancher to feed the bighorns.
To this day, the peri-urban herd provides easy access for citizens and scientists to observe the species.
Adler and Woodward piled into an off-road vehicle to make the initial ascent up the quarry on a recent research trip. Although the bighorn sheep here have grown accustomed to heavy machinery, they remain highly attuned to predators.
Near the top of the quarry, they parked and continued on foot. The wind carried their scent towards the sheep, but Woodward and Adler thought that if they stayed hidden behind an outcrop, then army-crawled into position, they would be close enough to take a shot.
At the base of the quarry, Brandon Bacon, a terrestrial wildlife technician, tracked the sheep through a spotting scope.
Woodward grew up in Lamar, Colorado. He remembers fishing trips with his grandmother and summers spent catching lizards and snakes. It wasn’t until college, when he worked as a technician for Colorado Parks and Wildlife, that he fell in love with ecology.
“I was a history major until I learned this was a job,” said Woodward.
He and Adler tiptoed through a patch of old snow.
The gun was loaded. The sheep were fewer than a hundred yards away.
Suddenly, a ewe lifted her head. She sniffed the air then paused. The men hunkered at the back of the terrace until the sheep returned to their food.
Woodward and Adler crept along the edge towards a boulder right above the sheep.
But the radio crackled.
“They bolted,” said Bacon.
The sheep bounded up a shelf at the south end of the quarry. They raced into a grove of standing dead trees. They were gone.
“Even though they act a little more accepting towards humans, they're still wild animals, and they're going to do wild things,” said Woodward.
Across the state, winter offers the best window for bighorn sheep research when herds descend to more accessible terrain and cooler weather makes it safer for biologists to handle the animals without harming them.
In addition to ground missions, like the one at Pikeview Quarry, CPW uses small planes and helicopters to conduct annual surveys of bighorn sheep populations. These data help biologists adjust the number of hunting licenses and understand where disease conflicts may exist.
One of the problems researchers face in addressing respiratory diseases is that by the time a disease outbreak becomes apparent, it can be too late to take action. Because bighorn sheep are often visible throughout the Front Range, it’s easy for people to assume that the species is thriving, said Meyers.
“The animals are really good at hiding what's going on so that they don't show signs of weakness to predators,” said Karen Fox, a veterinary pathologist and research scientist at Colorado State University.
“But when I get them on the necropsy floor and I open them up, I find the lesions. Some of these animals are so badly affected that they are coughing. They have mucus pouring out of their noses.”
At times, disease outbreaks have dramatic outcomes, like the Trickle Mountain die-off. Between 1992 and 1993, pneumonia reduced the Saguache County population from 400 bighorn sheep to 200. By 2010, the Trickle Mountain herd had just 35 sheep left.
More recently, disease die-offs have taken a more imperceptible form, striking lambs and leading to a slow decline in a herd’s numbers.
“It's kind of an evil irony. Each year the lambs will be born and the lambs look perfectly healthy. They're sprite. There's a good number of lambs per ewe. As the summer progresses, though, and we get closer and closer to fall, you'll start noticing fewer and fewer lambs with the ewe, and then eventually, we start observing sick lambs on the landscape. It’s heartbreaking,” said Woodward.
Biologists have traced the current die-off among the Pikes Peak bighorn herd to an incident in 2021 when domestic sheep escaped from a small-scale “hobby” farm. Hunters alerted CPW. When they found the domestic sheep, they were corralled in a canyon that happens to be a primary migration corridor for the area’s bighorns.
“It couldn't have been at a worse time of year. It was right at the beginning of the lambing period, in which those sheep were moving down from Pikes Peak into their lambing area, at the end of this canyon,” said Woodward.
CPW tracked the bighorn lambs born that year.By November, they had observed 16 ewes without lambs.
“We knew at that point that we were seeing a pneumonia related die-off,” said Woodward.
Since then, he and fellow researchers have observed other sick lambs on the peak.
“It’s not easy to watch,” he said, describing the cough as “guttural.”
“You could see it in their stomach. You could see all their muscles contracting. It has a very distinct sound, almost like a metal can being rattled with rocks inside.”
Another problem researchers face is that respiratory diseases stem from many different types of pathogens — which makes the possibility of developing a vaccine more difficult.
Karen Fox began studying respiratory disease in bighorn sheep during her doctorate in 2009. Today, her research seeks to understand the genetics of disease-causing bacteria to see if she can identify patterns that correlate to better or worse outcomes in infected animals.
At the Veterinary Diagnostic Laboratory at Colorado State University, Fox pulls from a freezer with over 800 tissue samples collected from dead bighorn sheep’s lungs, respiratory tract or tonsils.
So far, Fox has analyzed just 200 of the 800 samples, but she hopes this research will offer more accurate predictions of how sick herds will fare.
“If we find that there's certain strains of bacteria that are causing certain diseases in the bighorn sheep populations, then maybe we can use that information to develop tools for management, things like vaccination,” said Fox.
“That hasn't been a super successful approach in bighorn sheep so far, but maybe we just haven't found the right strain to make a vaccine against.”
Despite an abundance of research showing pathogens from domestic sheep and goats can infect and harm bighorn sheep, “there is a lot of denial of the science,” said Meyers, referring to both ranching groups and federal land managers that have minimized the risks of the disease.
According to Meyers, ranchers insist that other animals are to blame or that bighorn sheep have already been exposed, so the risk of disease is nonexistent.
For now, separation between bighorn sheep and domestic sheep and goats is the only surefire way to prevent the spread of disease. But according to Meyers, more than 100 of the state’s roughly 480 domestic sheep grazing allotments that are on forest service or BLM land directly overlap with bighorn sheep herds. Roughly 180 more are within nine miles of a herd.
“We don't have control over what people do on their private lands, but on public lands, we should be able to protect bighorn sheep from the potential for exposure to pathogens,” said Meyers.
In Colorado’s San Juan mountains, glaciers from the last ice age gnawed away at the volcanic debris making way for an ocean of grass. Today, a chorus of “baaas” and bells provide the soundtrack of grazing season.
Ernie Etchart grew up raising sheep in these mountains. His father, originally from the Basque Country of Spain, came to the U.S. as a shepherd in 1947. When a neighboring rancher offered Etchart’s father the opportunity to buy his operation, he leapt at the chance to own his own sheep. In 1986, he turned the business over to his sons. Today Ernie Etchart and his brother George Etchart run roughly 3,200 ewe-lamb pairs.
In 2023, Etchart made headlines when he agreed to relinquish five grazing allotments, totaling over 100,000 acres above Silverton, Colorado in order to protect bighorn sheep in the area.
According to Etchart, before the deal he faced increasing pressure from bighorn sheep advocates. Other challenges, like difficult access and increasing recreation in the area added to the strain.
“We'd been getting pressure from the Bighorn Sheep Society for a number of years. They of course put pressure on the Forest Service and BLM, which in turn would put pressure on us,” said Etchart. “They wanted us to be perfect out there, and sometimes that's pretty tough to be perfect when you're dealing with animals.”
After thorough consideration, Etchart accepted a deal to waive his grazing rights in exchange for an undisclosed sum of money from the National Wildlife Federation. In response, federal agencies agreed not to restock the grazing allotments. Since accepting the deal, Etchart has begun grazing on private land near Norwood and Ridgeway, Colorado.
“It was a hard decision, but there were a lot of issues for us with those permits. We had to make a business decision,” he said.
In spite of the agreement, Etchart remains skeptical about the risk domestic sheep pose to bighorns.
“There's a lot to be known about the risk of disease transmission between domestic sheep and bighorn sheep,” he said.
He points to the success of the San Juan west herd — one of the state’s healthiest — in spite of long-term grazing in the area, along with the availability of bighorn sheep tags in Colorado as evidence that the species is thriving (in 2024 CPW issued 336 bighorn tags to hunters).
“Just because we haven't had a die-off in 20 or 30 years in a particular herd, doesn't mean it's not going to happen,” said Meyers. “When we look around the state and we look around the West, these die-offs are happening every single year. It's just a matter of time before the next exposure happens that causes a die-off in the herd.”
Despite the success of voluntary permit waivers like Etchart’s, Meyers, who has helped to facilitate four other such deals with Colorado ranchers, sees the tool as a temporary solution.
“There is not enough money with NGOs to fix all of these problems. And while compensated permit waivers are very appealing to the federal agencies because it gets them off the hook without making a decision, we can't do it all. There's only enough money available for us to undertake one of these agreements every year or year and a half,” he said.
Meyers attributes the lack of change at a government level to several factors.
First, wildlife biologists who monitor bighorn sheep have few management tools to resolve disease conflicts. CPW can repopulate herds with healthy sheep, change the number of hunting licenses or work on habitat restoration, but when it comes to conflict with ranchers, it is ultimately up to federal agencies who oversee grazing permits to make changes.
In 2009, Colorado Parks and Wildlife, the Colorado Wool Growers Association, the BLM and U.S. Forest Service signed an agreement “that the wildlife agency would not advocate for closure of domestic sheep allotments based solely on the risk to bighorn sheep,” said Meyers.
Although the agreement was not re-signed in 2019, it remains up to federal agencies to respond to management suggestions made by CPW.
“Federal agencies are responsible for managing the land, and they're in large part not responding to all of those comments in a way that's favorable to bighorn sheep. They continue to manage the lands to the detriment of bighorn sheep in many areas,” said Meyers.
In theory, federal agencies are supposed to reevaluate grazing permits every 10 years when the permits expire.
Lacking resources to analyze every permit, federal agencies turned to Congress to ask for additional time to complete the requisite environmental assessments of grazing allotments.
In 2015, Congress passed a rider provision alongside the National Defense Authorization Act. The measure required federal agencies to renew permits under the existing terms and conditions.
“It essentially took the agencies off the hook of ever doing National Environmental Policy Act analysis on grazing allotments,” said Meyers. “They still do what they can, but they don't undertake the difficult ones with challenging resource conflicts like bighorn sheep, because those are very time consuming and costly.”
“Federal agencies are leaving us high and dry. They've abandoned us on this issue. They and Congress really need to step up and help us all solve this problem,” said Meyers.
Despite a lack of promising solutions, bighorn sheep advocates see glimmers of hope. Meyers points to decisions like Vail’s recent settlement that will protect winter range for bighorn sheep as evidence that people do care about the species, especially when they understand the problem bighorns are facing.
Later this year, Woodward and his team plan to relocate a portion of the Rampart Herd to a wildfire burn zone west of Pueblo, Colorado. The fire thinned vegetation, creating new habitat for the species.
Meyers sees education as a key stepping stone towards future conservation. He pointed to the success of other wildlife campaigns like “Be Bear Aware.” Moving forward he hopes to collaborate with CPW and the Department of Agriculture to develop a similar education program focused on bighorn sheep.
“Then, maybe when people are out mountain biking on national forest lands and they encounter a big herd of domestic sheep, it will make them stop and wonder about why those sheep are there and what potential impacts they might be having on bighorn sheep,” said Meyers.
It’s unlikely that bighorn sheep will ever recover to the pre-colonization numbers — in fact, populations that are too dense could make disease transmission more likely. But for bighorn sheep advocates, the fight to protect the species is driven by a desire not just to protect nature, but to save a symbol that has come to embody wildness itself.
“We're stewards of the ecosystem. We're stewards of the country and where we live. And it's our obligation to protect wild species,” said Meyers.
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