For the first two hours of the bone-jarring drive into the Pryor Mountains you do not see much but rocks, scrubland and tree stumps charred by a recent forest fire.

It is only when you reach the subalpine meadows at 8,000ft (2,400m) looking over the vast, red rock deserts of Wyoming below that the creatures begin to emerge slowly. They are a magnificent sight: wild horses, their lineage unbroken from the horses that arrived with Spanish conquistadors about 500 years earlier.

This particular herd has even greater historical significance: its ancestors were tamed by the pioneering Lewis and Clark Expedition across the West but were stolen by the Crow tribe, who set them free.

They have been living in almost complete isolation ever since, protected by a 1971 Act of Congress which declared that wild horses, or mustangs, be “living symbols of the historic and pioneer spirit of the West”.

Last week, however, the US federal government’s Bureau of Land Management began to round up the horses using a helicopter in an effort to reduce their numbers.

It is part of a scheme that has resulted in 33,000 mustangs being caught, with only about 26,000 left to roam. Some of the horses will be put up for adoption. Others will be released, but only after the mares have been given contraceptives.

What happens to the rest, especially the older ones, is not clear, although one thing is for sure: with budgets being cut because of the recession, feeding and housing captured mustangs is not a priority.

Planning documents obtained by a request under the Freedom of Information Act suggest that a mass cull has been considered, including a proposal to offer vets counselling to cope with the number of animals that would have to be put down.

Another option is for the horses to be sold, although this could result in them being slaughtered for meat.

“Since wild horses were protected by Congress in 1971, the Land Bureau has taken away 19.4 million acres of their land,” Ginger Kathrens, a wildlife film-maker, said as she watched a mare and her lame foal make their way to a watering hole on Pryor Mountain. The horses were among those that escaped the round-up but the foal was injured in the process.

The remaining herd of 120 or so horses left on Pryor Mountain is now genetically non-viable, she said. “People get paid to manage, rather than leaving things up to natural selection,” she said. “They say the land’s not suitable for mustangs, then they end up leasing it to cattle ranchers for just $1.35 per cow, per month.”

Ms Kathrens said that this was “welfare ranching” to reward politically connected farmers.

Land officials said that the Pryor Mountain meadows have been overgrazed by the horses, which they described as feral rather than wild.

They said that if the herd was not managed its population would double or triple within a few years, resulting in many of the horses starving to death. “And you know who’d get the blame for that, don’t you?” said one official, who did not want to be named. “We can’t win either way. Meanwhile, Ginger Kathrens is making a lot of money by giving these horses romantic names and making films about them.”

Ms Kathrens appears to be winning political support: a new law named the Restore Our American Mustangs Act, which would outlaw the sale and slaughter of wild horses, has been passed by Congress and is expected to get through the Senate.

Wild and free

— The ancestors of today’s horses lived in North America, four million years ago, where the genus Equus originated

— Horses died out in North America between 13,000 and 11,000 years ago but by then had spread to Asia, Europe and Africa

— In the 16th Century Spanish conquerors reintroduced horses to the Americas. By then they had been domesticated, but escaped horses returned to the wild and spread throughout the Great Plains

— The controversial process of mustanging — hunting wild horses from cars or airplanes or by poisoning — was outlawed by the Wild Horse Annie Act of 1959

— Mustangs gave rise to cultural icons such as the Ford Mustang and the 1965 song Mustang Sally, sung by Mack Rice

— In 1971 Congress adopted the Wild Free-Roaming Horse and Burro Act, giving the horses federal protection to preserve “a living symbol of the historic and pioneer spirit of the West”

Sources: Bureau of Land Management, Natural History magazine; Times database

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