SALT LAKE CITY — The federal agency charged with managing wild horses and burros that roam freely across 11 Western states should consider sterilizing some mares to control booming mustang populations and protect ranges, a citizen advisory panel recommended Tuesday.
The Bureau of Land Management has long struggled with how to manage growing horse herds on public lands, which can double naturally within five years if left unchecked. Horses have been injected with drugs and vaccines to slow reproduction and rounded up for adoption, but the agency has more horses in captivity than are left roaming the range, forcing the emphasis to shift to population control rather than roundups.
Nearly 60 percent of the agency’s entire budget for the wild horse program is spent on housing horses.
Drugs used to slow reproduction in wild horse herds must be readministered regularly because they work for only about a year, and drugs that work longer have not yet been approved for use on wild horses, said Dr. Boyd Spratling, a veterinarian from Deeth, Nev., and chairman of the bureau’s Wild Horse and Burro Advisory Board.
Instead, spaying horses — or surgically removing the ovaries of older mares — eliminates the need for frequent roundups for adoption or to administer drugs, he said. Younger mares could still foal, allowing for genetic diversity in herds.
It is not a permanent solution, Spratling said, but a tool the land management bureau should have available for use in its effort to control herd sizes.
‘‘Surgery is never 100 percent safe, but this is considered to be effective and relatively safe and has long been used in the racehorse industry,’’ he said.
The bureau estimates there are 37,000 horses on public lands in the West. An additional 47,000 horses have been removed from the range and are being cared for in short-term or long-term holding areas.