PORTLAND, ORE. — Wild horse advocates are calling for a stop to one of the largest roundups of wild mustangs in Oregon history.
The U.S. Bureau of Land Management on Monday began preparations to gather up to 1,500 wild horses roaming freely on about 625 square miles of the Beatys Butte herd management area east of Lakeview in southern Oregon.
Officials say the mustangs will be rounded up by helicopter. The roundup's aim is to reduce the population to 100 and remove the rest.
It's the first roundup since a federal investigation in October determined a Colorado livestock hauler repeatedly lied to officials and sold nearly 1,800 wild horses to buyers who took them to slaughterhouses in Mexico.
The hauler bought the mustangs through the BLM program that's supposed to provide wild horses with good homes.
Wild horses are protected under federal law, and selling them for slaughter is illegal. The BLM said it has taken additional steps to "prevent this type of situation from happening."
Officials say the large population of mustangs in southern Oregon damages the environment and wildlife, a problem compounded by the area's drought that has stressed forage and water availability.
"Horses have overgrazed sagebrush and other plants to the extent that plants and soils are being lost entirely," BLM spokeswoman Larisa Bogardus said in a statement.
But horse advocates say conflicts with livestock, which share the land with the mustangs, are driving the roundup. Deniz Bolbol with American Wild Horse Preservation Campaign said thousands of cattle are permitted by the federal government to graze in the area.
"It's the ranchers versus the wild horses," Bolbol said. "The horses eat the same food as the cows."
Federal officials say ranchers have voluntarily reduced grazing in the area by approximately 70 percent.
Wild horse advocates are also asking the government to implement a program to suppress population growth — with the use of a fertility control vaccine that's currently administered to a small number of horses.
But BLM says that vaccine's effectiveness is limited to one or two years and must be hand-injected or deployed via ground-darting, making it difficult to administer to wild horses on a large scale. The agency is currently researching other fertility controls, including sterilization — something mustang advocates say would be cruel and would change wild mustangs' natural behavior
According to BLM data, there are an estimated 47,000 wild horses and 10,000 wild burros living freely on the range throughout the U.S.
In Oregon, an estimated 4,300 wild horses and 50 burros roam freely.
BLM says it must round up horses, because mustangs have no natural predators and their herd sizes can double every four years. From 2012 to 2014, the agency removed about 13,000 wild horses from the range throughout the West.
Few of the animals are actually adopted or sold. Instead, many wind up in BLM's long-term facilities. Currently, 46,000 wild horses are held in off-range corrals, pastures and eco-sanctuaries — including about 550 mustangs in a facility in Burns, Oregon. The cost of feeding and housing the horses: $49 million a year.
Beatys Butte has the largest number of mustangs in the state: 1,287, according to the most recent census count last June. The agency estimates a 20 percent annual population growth, so up to 1,500 could be present, but a recent survey estimated 1,255 horses.
During the roundup, which could take up to a month depending on weather, about 100 horses will be captured daily. They will be checked by a veterinarian and transported by truck and livestock trailer to the Burns holding facility. Once capacity is reached, the remaining horses will be transported to Palomino Valley, Nevada or other holding facilities.
All gathered horses will be offered up for adoption later this year.