Updated

Advocates for wild horses have sought an injunction to stop researchers from surgically sterilizing more than 200 wild mares at a facility in Hines, Oregon.

The U.S. Bureau of Land Management has said the research slated to begin this summer would help determine whether the three methods to be studies are safe, effective options for controlling the wild horse population.

But the nonprofit group Front Range Equine Rescue describes the procedures as unnecessary and barbaric.

Group President Hilary Wood said in a statement that performing unproven surgeries is contrary to the Bureau of Land Management's congressional mandate to care for wild horses, especially when an existing vaccine works as effective birth control.

The Bureau of Land Management, which has said the vaccine isn't effective enough, did not have an immediate response to the lawsuit, which was filed Monday in Washington, D.C.

Of the three methods, the advocates are most concerned about a procedure that involves removing ovaries from sedated, pregnant mares in various gestational stages. The veterinarian reaches into the mare's abdomen through the vagina to sever and remove the ovaries.

"BLM's intention to engage in the blind excision of mares' ovaries, with the hope that they get it right, is dangerous, inhumane, potentially fatal, and arbitrary and capricious," the lawsuit states.

The decision to carry out the research comes on the heels of the Bureau of Land Management's latest annual population estimate that shows about 67,000 wild horses and burros roaming public lands in 10 Western states.

The agency says that's more than double what it considers healthy for the animals and the rangeland.