Three dead foals were the first sign that something was wrong with the West Douglas herd, mustangs that until eight months ago had roamed dry and rugged rangeland in far western Colorado.
When the third foal died on April 18, following the recent death of another foal and one that was stillborn, the Bureau of Land Management ordered a necropsy.
Five days later, nine horses from West Douglas were found dead in their pasture at the wild horse holding facility in Cañon City, according to documents released by the BLM. More horses have died every day since, with the toll rising to 119 on Monday.
At first, it seemed the horses had neurological issues, but as the deaths continued, veterinarians determined the animals had hypoxia, or low oxygen levels, due to the respiratory illness. Many were coughing and had labored breathing. Some developed pneumonia.
In little more than a week, the outbreak of equine flu has killed more than one-quarter of the 450 West Douglas horses captured last summer, enraging wild horse advocates who already were frustrated by the federal government’s helicopter roundups and holding pens. The horses’ bodies are lifted out of the pasture by a tractor and will end up in a landfill, though the BLM declined to say which one for security and safety reasons.
“It’s definitely exacting a toll on us and exacting a toll on all of the people who care about wild horses,” said Steven Hall, a spokesman for the Bureau of Land Management. The focus now is on “how did we get here” and how to prevent anything like this from ever happening again, he said.
The deaths also have bewildered veterinarians and scientists who are trying to figure out why a fairly common virus is causing West Douglas horses to drop dead but has not killed horses from any other rangeland.
The southern Colorado holding pens, on the grounds of a state prison in Cañon City, also contain hundreds of mustangs from the Sand Wash Basin in northwestern Colorado. That beloved herd, known for its coloring and a famous pinto stallion named Picasso, includes hundreds of horses named by wild horse advocates who traced Picasso’s bloodline and traveled to desolate country near the Wyoming state line to watch the horses herded by a low-flying helicopter last September.
The West Douglas herd is less well-known, mainly because the land where they lived along the Colorado-Utah border was remote, craggy and inaccessible. The BLM deemed it “unsuitable” for wild horses and last summer, announced an emergency roundup of 450 horses and burros after a wildfire burned up what was left of their habitat, Hall said. The land is parched, with little water and not much vegetation to feed the horses, federal officials said.
Now, veterinarians are wondering whether the horses’ exposure to the Oil Springs fire, which burned more than 12,000 acres south of Rangely last June and July, made them more likely to die from equine flu.

The BLM documents on the Cañon City outbreak also noted that many of the West Douglas horses had not yet been vaccinated or were only partially vaccinated for the flu virus, a revelation that has angered national mustang protection groups.
The BLM’s goal is to brand, microchip, de-worm and vaccinate wild horses within 30 days of capture, according to the agency. That timeline was not followed with the West Douglas horses, however. Vaccination is not required to occur within 30 days and its timing can depend on the advice of a veterinarian, based on the horses’ condition. Bureau officials said they plan to release more details in the coming days about why those horses had not yet received their vaccinations.
The morbidity rate among West Douglas horses is as high as 60%, but among other horses, only about 10-20% are showing signs of respiratory illness, and their symptoms are mild, according to a veterinarian report released by federal officials. The West Douglas horses were separated from other horses when the outbreak began, and, the report noted, the outbreak started just five or 10 days after the first group of 50 West Douglas horses received their first dose of flu vaccine.
The veterinary report pointed out the intense wind that blew through the corrals around the start of the outbreak, noting “severe dusty conditions with blowing heavy dirt enough in areas to block visibility.”
The report, by the U.S. Department of Agriculture veterinarian Albert Kane, also found that BLM workers were using the same loader to dispose of horse carcasses and to load hay. Workers changed the head of the machine and sprayed it with bleach between uses, however.
The detail incensed wild horse advocates, who for years have railed against the BLM’s crowded holding facilities that confine in close quarters horses that used to roam free.
The American Wild Horse Campaign is calling for an investigation into the outbreak, including why the horses weren’t vaccinated despite being hauled to the holding pens last summer.
“This is a tragedy for all involved, but especially for the treasured wild horses who just last summer were running free on our public lands and are now dead,” said Scott Wilson, a Denver-based board member of the national group. “We cannot continue to round up wild horses from their native habitats, cram them into holding pens and expect a good outcome for the wild horses or the taxpayers who are funding this broken system.”

Nationwide, the bureau has more than 56,000 wild horses and burros in holding pens or pastures, some awaiting adoption. That includes more than 2,000 horses in Cañon City, where prison inmates care for the animals.
The agency estimates there are about 82,000 wild horses and burros roaming rangeland in 10 western states, but says the land is appropriate for only about 26,000 of them. In Colorado, about 1,800 mustangs remain on range, but the federal goal is 827.
The BLM has plans to round up an additional 19,000 wild horses and burros in the next year, part of a multi-year effort to thin herds in several western states. More than 13,000 horses and burros were captured in 2021, and more than 10,000 were captured in 2020.
The agency’s “adoption incentive program” pays people $1,000 to adopt a wild horse or burro, and they must agree to care for the animals for a year, when they will receive title to the horses. When that year is up, say horse advocates, some horses and burros end up sold in auctions for slaughter.
A Moffat County adoption of Sand Wash Basin horses, in Maybell, has been postponed indefinitely because of the outbreak, said Hall, from the BLM.
Federal law prohibits wild horses from being sold as food, including pet food. Proper disposal of the carcasses is a landfill, Hall said.
At least 15 horse carcasses were sent for necropsies. Further information about the cause of the deaths is expected in a few weeks, the BLM said. “I think we are all curious as to why this particular group of horses is getting so hard hit by the virus,” Hall said.