An estimated 67,000 wild horses and feral donkeys are roaming the ranges of ten western US states, far above the sustainable target of 26,000 as designated by the country’s Bureau of Land Management (BLM). ‘Without active controls, horse populations can become a stress for grazing land,’ says Dr Robert Fonner, an environmental economist at the National Oceanic and Atmospheric Administration.

Not only is the overpopulation difficult for cattle ranchers, who argue that they ruin rangelands, it is also a fraught issue for animal welfare groups. With few natural predators, the horses are predicted to exceed 100,000 in the next four years, starving each other of water and food. They can be rounded up using helicopters, though this has become a somewhat controversial practice as it can cause stress and injury to foals and older animals. There is also the problem of what to do with the horses once they are contained. Already there are around 46,000 horses penned into temporary pastures, of which only 2,500 to 3,000 are moved on for adoption every year.

“Free roaming horses are an enduring icon, but an effective and sustainable population management plan has eluded land managers for decades”

The BLM is faced with the difficult decision of how best to manage the overpopulation, a problem complicated by the disputed ‘wildness’ of the horses. While archeological evidence shows that native horses lived on the continent 12,500 years ago, the mustangs that roam the West today are descended from domestic breeds brought from Spain during the settlement of North America. In 1971, their protection was enshrined with the Wild and Free-Roaming Horses and Burros Act, which stated that the animals are ‘living symbols of the historic and pioneer spirit of the West, which continue to contribute to the diversity of life forms within the Nation and enrich the lives of the American people.’

‘Free roaming horses are an enduring icon,’ says Fonner, ‘but an effective and sustainable population management plan has eluded land managers for decades.’ Indeed, a citizens panel’s advice to slaughter a large number of horses last September was met with national condemnation.

A more popular option than slaughtering is to try and sterilise the animals, however the current drug must be administered annually, which costs resources and time. With present population trends unsustainable, it is likely the BLM will use a hybrid plan of fertility control and gathering to manage wild horses in the coming years.

This was published in the March 2017 edition of Geographical magazine.