Colorado has a wild horse problem. Could its expanded birth control darting program be a model for the West?

SAND WASH BASIN, Colorado — Robin Wadhams reviews the list of wild horses that still need to be darted this summer before she sets up for target practice.

Each mare has a name: Angel, Bisbee, Calamity, Dust Devil, Eeyore, Kamchatka. Next to them are notes on whether the horse needs a first dose of contraceptive, or just a booster.

Some notes offer more specific guidance. For Gretchen: “Hard to dart — not a priority unless opportunity presents.”

About 10 times a year, Robin and her husband, Gary, make the four-hour trip from their home in Hotchkiss to the Sand Wash Basin Herd Management Area in the state’s far-northwest corner. There, in the sagebrush plains and dusty, endless hills roamed by about 400 horses, they set out to dispense fertility treatments via dart gun.

For years, dedicated volunteers like them — and the fertility treatments they administer — have served as a partial solution to an enduring controversy in the West: what to do with the ever-growing population of thousands of wild horses that call the region home.

Only a tiny fraction of the more than 53,000 wild horses roaming the West receive fertility treatments, which are intended to help keep the population numbers below the level the Bureau of Land Management has determined is healthy for the herds and the ecosystem. So the BLM relies heavily on roundups of excess horses and the payment of tens of millions of dollars to keep them in captivity off the range — a drain on the budget for the program that also makes it difficult to address the underlying reproductive problem.

“Seeing new foals used to be so fun and exciting, but now I just cry,” Robin Wadhams, who has been visiting the Sand Wash Basin herd since 2012, said on a recent morning in July while preparing to dart more horses. “I’ve cried more out here than I have in my whole life.”

State and federal leaders in Colorado are trying out a new approach. A series of new state laws comes with an aim of elevating the state’s role in managing the 1,400 wild horses within its borders. The state will pay the federal government to deploy paid, professional darters to supplement the fertility control work long performed by volunteers.

The expanded darting program is intended to help address the root of the herds’ growing population by reducing the number of foals born every year.

“It’s a part of the heritage of the West, so I think it’s important for the state to step up,” said Wayne East, the wildlife programs manager for the Colorado Department of Agriculture.

The new arrangement is a model for states across the West, according to lawmakers, horse advocates and land managers. But it’s unclear where the money to sustain the efforts will come from, especially with the state’s budget in shambles and continued federal cost-cutting by the Trump administration.

“I know there’s a more permanent solution,” said Colorado House Majority Leader Monica Duran, a Jefferson County Democrat who led the legislative effort in recent years. “What that is, we’re going to figure it out. It all revolves around funding.”

* * *

At 10 a.m. during their recent outing, the Wadhamses’ 4Runner has a flat. Robin hears the hissing air first.

She and Gary have already mixed the fertility vaccines and placed them back in a cooler before noticing their new tire problem. The vaccine, called PZP, stimulates female horses’ immune systems to prevent pregnancy but requires an annual booster.

The Wadhamses also have already completed target practice that morning with their air rifles, launching darts into a target shaped like a horse rump that’s tacked to the side of a corral.

To successfully dart a horse, they must be able to get within about 40 yards of the wild animal, then hope it stands still — and keeps its flank visible. They also have to accurately gauge the wind’s effect on the flying dart and hit a target that measures about 2 feet by 2 feet.

The Wadhamses have led the fertility control effort in the management area since 2017, volunteering hundreds of hours. They are some of the most experienced volunteer darters in the state and usually get between three and 10 horses each day they are on the range. As of late July, they had darted at least 50 this year.

Before the Wadhamses dart a horse, however, they have to find the animals on the expansive 250-square-mile range — about 1.5 times the size of Denver and full of gullies, draws and plateaus.

“It’s not a zoo, there are no schedules,” Robin says. “You don’t know where they will be.”

But the search that day will have to wait a bit. They need to drive 30 minutes back to the nearest town, Maybell, and see if the town’s handyman is home to fix their flat.

* * *

About 1,400 wild horses roam the BLM’s four herd management areas in western Colorado — more than the approximately 800 mustangs the federal agency estimates would make for a sustainable population.

Two of the herd management areas — Piceance-East Douglas and Sand Wash Basin — have more horses than the BLM thinks the land can support. Two others have populations within the BLM’s limits: the herds in Little Book Cliffs and Spring Creek Basin.

Where herd numbers outstrip the appropriate management levels determined by the BLM, federal agencies use helicopters or bait to remove horses from the wild. The BLM estimates the West has 47,500 more wild burros and horses than the landscape can support.

Range conditions deteriorate in places where too many horses roam, said Doug Vilsack, the BLM’s Colorado state director. The horses — the descendants of escaped domestic horses and not a species native to the West — have no natural predators and their populations can expand rapidly. That degrades vegetation and water sources relied upon by other wildlife and livestock that graze the public lands.

“The fundamental challenge that we deal with is biology and ecology,” he said.

Once captured, the BLM moves horses to short-term holding facilities — like the 3,000-horse holding area on the Colorado Department of Corrections’ campus in Cañon City — and makes them available for adoption. Those that aren’t adopted or aren’t suitable for adoption are sent for life to long-term holding facilities in the Midwest.

Nationwide, more wild horses are now held in federal facilities than are free-roaming in the West.

“It’s a tragic kind of failure of the system,” said Scott Wilson, the Colorado-based director of strategy and awareness for American Wild Horse Conservation, an advocacy group for the equines.

The costs of keeping those horses off the range eats up two-thirds of the BLM’s spending, leaving little money to address the underlying issue. More than 60,000 horses sit in holding facilities, which cost taxpayers more than $100 million a year.

Funding for fertility treatments, in contrast, is limited to no more than $11 million a year.

“The BLM is faced with rising costs in off-range animal care, meaning the share of the program’s budget dedicated to off-range corrals and pastures will increase at the expense of other vital program operations, such as conducting removals to more immediately address overpopulation on the range,” agency leaders wrote in a budget request for the 2025 fiscal year, which ends Sept. 30.

Nearly everyone involved in wild horse management in Colorado wants to minimize the use of roundups and long-term holding.

Wild horse advocates say helicopter roundups stress horses as they are chased for long distances, and the activity can lead to serious injuries or death as they flee. It also can split up family structures. Land managers, for their part, are wary of the controversy the roundups draw.

“The fewer horses that are coming off the range, the better outcomes for holding and adoptions,” East said.

Colorado’s new strategy aims to “break the cycle” of roundups by implementing more robust fertility darting, Vilsack said. Darting is something that can work, he said. The Spring Creek Basin herd outside Norwood — the smallest of Colorado’s herds — has not needed a roundup for 20 years because of dedicated and effective darting by volunteers, he said.

The addition of paid darters will put more boots on the ground and will add consistency to the state’s darting program as volunteers come and go.

“It’s really been on the shoulders of these volunteers for many, many years,” Vilsack said.

* * *

About noon, after an hour-long detour to get the flat tire fixed, the Wadhamses are back on the dirt roads of the herd management area. They’ve been driving for more than an hour without any evidence of the horses, except for piles of excrement and a sign at a pullout that explains to visitors the problem with horse overpopulation.

As a massive dirt devil blasts grit in their eyes, the couple checks nearby water sources to make sure they’re still full. The area’s natural ponds have long since dried in the sun, leaving pits of cracked mud behind. Instead, the horses rely on well water drawn from the ground by solar-powered pumps paid for by the BLM.

It’s difficult to find other volunteers willing to spend their days darting horses, Robin says. It can take months to improve one’s accuracy with the dart gun and years to learn all the horses. Darting means long, hot days of dusty, difficult work.

At times, she and Gary have been the only active volunteers in the basin.

Gary recently retired from his work in the lumber industry, and the couple is now wondering what’s next for them — and how darting will fit into this next phase of life.

“We’ve always known that we needed help,” she says. “We can’t be here every day.”

* * *

Colorado’s recent progress on the wild horse problem accelerated when Sandra Hagen Solin and her mom visited Sand Wash Basin in 2021 and saw wild horses running across the sagebrush.

Solin, a Colorado lobbyist for 30 years, had heard about the roundups. After seeing the horses on the range, she went to work to find out what could be done to make herd sizes more sustainable and minimize the roundups.

“Quite often, the response is that it’s a federal issue (and) ‘I can’t do anything about it,’ ” said Wilson of American Wild Horse Conservation. “Credit to the governor for actually saying, no, these are federal horses in our state — and the state cares about these horses and their well-being.”

Behind-the-scenes conversations with lawmakers, wild horse advocates and Gov. Jared Polis’ office in 2023 resulted in a bipartisan law. It created a working group that examined potential long-term solutions and set aside $1.5 million for the issue. The members’ task: to recommend ways to better manage horses once they are taken off the range and to improve fertility control.

Localizing the group’s efforts to Colorado was the key to making tangible progress on a highly controversial and emotional issue, said Solin, who served on the working group. It showed that old, deeply entrenched divides between wild horse advocates, agricultural interests, the BLM and state leaders could be bridged.

Lawmakers enacted the working group’s recommendations in May with a second bill. Wild horse advocates said it established Colorado as a leader in the arena.

The law created a wild horse program inside the Colorado Department of Agriculture and established a permanent advisory committee in the department.

The 2025 law also earmarked part of the $1.5 million to help pay for workers from the U.S. Department of Agriculture’s Wildlife Services program to supplement volunteer efforts to dart horses.

The BLM could not say how many wild horses the USDA team had darted this season. It said the volunteers and the federal workers, combined, had darted 172 horses across the state this fiscal year.

“(The state partnership) has given us a little more resources and a little more flexibility to set us on a path to solving the problem here in Colorado, rather than just keeping our heads above water,” Vilsack said.

But how the state will pay for the program in the long term is unclear.

“Finding funding sources is first and foremost, without having to rely on state funding — because, frankly, we don’t have it,” said Duran, the state lawmaker.

* * *

At 12:45 p.m., Robin Wadhams hops out of the 4Runner, quickly rattling off the names of the seven horses she sees staring back at them. Chewie is the stallion of this band, but the lead mare is wary of humans and is quick to drive the group away.

“She knows the darting game,” Robin says.

Gary tries anyway — three of the mares in the band need to be darted. As soon as he moves toward them, however, they move.

The couple hops back in the car. About an hour later, they find two more bands of horses — both of them equally difficult to approach.

Gary and Robin walk out into the sagebrush, their boots crunching on dry grass, in hopes of pushing the two groups closer together. Maybe the horses will be so busy paying attention to one another that they won’t pay as much attention to the approaching people.

The horses move, and they don’t allow the couple near. One of the bands canters down a ridge and out of sight.

“They don’t like us very much,” Robin jokes, getting back in the SUV to continue the search.

* * *

So far, the efforts of lawmakers and wild horse advocates have not been enough to fully curb the use of roundups in Colorado.

Since the legislature passed the first wild horse law in 2023, the BLM has completed three roundups in the state.

The BLM used helicopters to round up an entire herd of 122 horses in Rio Blanco County in 2023. In 2024 — while the working group was meeting — the agency sent a helicopter to capture 140 horses from the Little Book Cliffs Wild Horse Range outside Grand Junction. The helicopters chase the horses into chutes and then into corrals, where they are then loaded into trailers for transport.

One mare was euthanized after severely injuring her leg during the roundup

The BLM also used a bait-and-trap method in the Sand Wash Basin to remove 10 horses in 2024, and another 42 last month. In bait-and-trap operations, BLM workers lure horses into corrals with food and water, then close the gates.

Another roundup will likely be needed at the Piceance-East Douglas Herd Management Area, Vilsack said, but he hoped that could be the last one for a while — if government leaders and local volunteers can stick the landing with the birth control program.

“We’re not out of the woods yet, but the goal is a world — at least here in Colorado — where we can spend more time celebrating wild horses as opposed to sending letters back and forth about challenges we have,” he said.

But both the state program and the money for the professional darting are limited.

The state program has no dedicated staff, East said, though he will oversee the advisory committee when it begins next year. He oversees the program, along with three other programs in the state Department of Agriculture.

The state has an $800,000 contract with the USDA’s Wildlife Services for darting in 2025 and another $300,000 earmarked to continue that work through 2028, to augment the volunteer efforts.

East said he had a little bit of money left to support the advisory committee created by the 2025 law, but “otherwise the money is pretty much all been spent.”

“I would love to see down the road, when the state’s finances get better, a staffed wild horse program at CDA with dedicated staff,” he said.

If Colorado can achieve and maintain herd populations below the BLM’s limit, it would serve as an example to other states across the West that fertility control is effective and possible, Wilson said.

“That’s such a brilliant goal for this program for Colorado,” he said, “and would actually prove to other states around the nation that this is the model.”

* * *

At 2:45 p.m. under a hot sun, the breeze has the effect of a hair dryer as the Wadhamses look down into a gully at two horses at a watering hole. The horses don’t seem to mind their presence, but they are both males.

Another band stares down at the couple from a nearby ridge, refusing to come to the water until the couple leaves.

After a four-hour drive from home and more than seven hours in the basin, no mares have been darted. The horses are more scattered this time of year, Robin says, as they seek shade and cooler weather.

The Wadhamses would’ve given up years ago if they didn’t love the land and the horses, she says. The first time the couple came to the basin, they saw more than 100 horses galloping across the fields. They were hooked.

“We go through this sometimes,” she says. “Then we laugh about it and come back out the next day.”

Before returning to town, the Wadhamses will drive a few more hours to the northern edge of the herd management area, near the Wyoming border.

They want to know where the horses are and set themselves up for better luck the next day.