GREEN RIVER -- A massive, ongoing wild horse roundup in southwest Wyoming is getting bigger.
Federal cowboys will gather an additional 157 wild horses on top of the nearly 2,000 excess animals the agency originally targeted for removal from two large herd management areas in eastern Sweetwater County.
Bureau of Land Management officials said Monday overflights of the Adobe Town and Salt Wells Creek herd management areas showed there were more wild horses than previously thought.
Wild horse advocates in Wyoming decried the move and said the BLM's population counts can't be trusted.
BLM wranglers have gathered 1,360 wild horses since the roundup began Oct. 10, according to the agency's website. The helicopter-aided roundups have been helped by the unusually mild fall weather in the region.
BLM officials say overpopulated wild horse herds overuse the rangeland, threatening their own health and the health of native wildlife and plants and damaging water resources and reducing water quality.
BLM officials initially estimated that 1,950 wild horses would need to be gathered from the Adobe Town and Salt Wells Creek management areas to bring herd populations down to appropriate management levels.
During a September census flight, however, specialists found there were more wild horses in the area than previously estimated.
The agency now expects to remove about 1,737 excess wild horses from the area, which would bring down the population level to around 860 wild horses -- the low end of the BLM's appropriate management level.
Under the gathering plan, 100 mares will be treated with fertility control vaccines, then released into the wild.
The Adobe Town and Salt Wells Creek roundups are part of a larger BLM effort to removed thousands of wild horses from public rangeland across the West and in Wyoming.
An estimated 35,000 wild horses live on ranges in 10 Western states, according to federal figures.
The BLM says more than 5,000 wild horses are scattered across 16 herd management units in Wyoming. Most of Wyoming's wild horse herds are located in the southwest.
Horses in Wyoming are gathered under a "consent decree" reached with the state in 2003, which dictates that the agency meet Wyoming's wild horse population objectives with roundups.
The BLM's statewide population objective is between 2,700 and 3,700 wild horses.
Horses removed from the range are taken to temporary holding facilities in Rock Springs, then either put up for adoption under the agency's wild horse and burro program or placed in long-term holding pastures
The Adobe Town and Salt Wells Creek wild horse herds roam about 2.5 million acres of public, state and private land in Sweetwater and Carbon counties.
The BLM manages approximately 1.7 million acres across the two management areas located south of Wamsutter and Interstate 80. There are 22 livestock grazing allotments within the two herd management units.
The wild horses are descendants of introduced Spanish horses, local ranch horses and cavalry mounts.
BLM researchers contend wild horses have no natural predators and with annual reproduction rates of between 15 and 20 percent, the excess animals must be periodically removed from public land.
BLM officials determined the appropriate management level for both the Adobe Town and Salt Wells Creek areas ranges from 861 to 1,165 animals.
BLM specialists estimated the wild horse population in the two herd management areas at 2,438 wild horses this summer. The estimate was based on July 2009 census flights that were adjusted for one year's foal crop.
Pat Fazio, statewide coordinator for the Cody-based Wyoming Wild Horse Coalition, questioned the need for gathering additional wild horses. She said aerial counts, whether by fixed-wing aircraft or helicopter, have always been suspect.
"It's quite obvious that an objective, accurate methodology is not yet in place," she said in an e-mail Monday.
"If the first count was inaccurate, how do they know that the follow-up count was accurate ... or a potential third, or fourth or fifth count?" she said. "In small herds, one can do ground counts simply by walking around the area and counting bands and band members, but in these huge (herd management areas), they do need a different way."
The BLM conducted several roundups in the two herd units over the past decade.
Wild horses were last removed from the management areas in January 2007 when wranglers were able to gather approximately 900 wild horses before bad weather shut down operations.
A roundup in August 2007 removed another 171 horses from the units.
The current Adobe Town and Salt Wells Creek roundup met with stiff resistance from wild horse advocates around the region when the BLM released its environmental study for public review in July.
In August, noted wildlife photographer, author and American Wild Horse Preservation Campaign supporter Carol Walker hand-delivered approximately 3,500 letters to Rock Springs BLM officials from people opposing the roundup.
Opponents have criticized the use of helicopters in the roundups, saying they can traumatize, injure or in some cases kill the animals.
BLM data shows three horses have been killed during the three-week Adobe Town and Salt Wells Creek roundup.
On Oct. 11, an approximately 20-year-old horse died from what veterinarians believe was caused by a combination of strain and old age.
On Oct. 15, another horse died during roundup operations. Veterinarians said the cause of death was also related to the strain of the gather.
Necropsies were performed on both horses, and the reports are pending.
On Saturday, one horse was destroyed after veterinarians determined it was blind.
Contact southwest Wyoming bureau reporter Jeff Gearino at (307) 875-5359 or firstname.lastname@example.org