Twelve wild horses have now died in a Nevada roundup directed by the U.S. Bureau of Land Management, half of them colts and mares.
The BLM on Wednesday said four more animals died or were put down because of dehydration or water intoxication. The agency also announced emergency measures to truck water to large bands of mustangs still on the range in the roundup area.
A federal judge scheduled a hearing for Thursday in Reno on a temporary restraining order sought by animal rights advocates to halt the roundup in northern Elko County.
The BLM suspended the gather over the weekend when seven horses died of dehydration and water intoxication after being herded by helicopter on the first day of the roundup. Another horse broke a leg and was put down.
Two more animals died Monday and two others were euthanized "because of complications related to water starvation and water intoxication," the agency said.
Horse protection groups have voiced outrage, saying the deaths were predictable, given sweltering summer temperatures and the weakened state of colts and mares that recently gave or were about to give birth.
Heather Emmons, a BLM spokeswoman in Reno, said the mustangs otherwise looked healthy and dehydration is difficult to detect. Water intoxication that can cause colic and brain swelling occurs when dehydrated animals drink excessive quantities of water.
The BLM blames the fatal outcome on drought conditions that have weakened the animals, and said aerial surveys showed two large bands of mustangs. One group of about 400 horses congregated around a dry reservoir and made no attempt to move to other water sources.
"BLM considers this an emergency situation," Ron Wenker, BLM state director, said in a statement.
BLM installed six water troughs with a combined capacity of 3,000 gallons near the herd, he said. If the animals don't migrate on their own, the agency will consider using a contracted helicopter to "gently and slowly" push them toward water.
Of the horses that died of dehydration, three were mares, three were colts, and five were studs. The animal put down for a broken leg was a mare. Wenker said the other 216 horses at a temporary holding site have improved, and 129 were trucked Wednesday to a regional adoption facility north of Reno.
A Justice Department lawyer, in a telephone conference with the judge on Tuesday, said the roundup could resume as early as Sunday, and Wenker said the BLM wants to gather the mustangs as quickly as possible after watering.
In the Reno lawsuit, Laura Leigh, a writer, artist and coordinator for The Cloud Foundation, a Colorado-based wild horse group, argued the BLM violated its own policy not to conduct helicopter roundups until at least six weeks after peak foaling season ends.
Mustang advocates contend that would mean after mid-August, but the BLM maintains the restriction ended June 30.
Leigh also argues that the BLM's temporary closure of more than 42 square miles while the gather takes place amounts to prior restraint of free speech and censoring of the press, preventing her from observing the roundup in a watchdog role.
A review team that includes outside experts has been formed to analyze the condition of the range, the horses and roundup operations, Wenker said.
The BLM had said it intends to remove up to 1,200 horses from the area and make them available for adoption or send them to long-term holding facilities in the Midwest.
Horse protection groups were unable to block the removal of nearly 2,000 horses from the Calico mountains north of Reno earlier this year.
The BLM says the roundups are necessary because the wild horse population is growing so rapidly that the animals are running out of food and damaging the range.
The animals are federally protected under the 1971 Wild Horse and Burro Act.
Bureau managers estimate that roughly 38,000 mustangs and burros roam 10 Western states, and half are in Nevada. The agency is in the process of removing about 12,000 animals to bring their numbers down to what it considers an appropriate management level.