Ranchers say the horses are competing with cattle for feed and water, and the counties are threatening roundups this summer if the BLM doesn't act.
To provide emergency relief in early April, the BLM set up corrals around a water trough on private land, but as of a week ago, not a single horse had been captured.
The BLM wanted to set up four more such "traps," Miller said, and he wasn't sure Tuesday whether the eight were captured in the original trap or a new one.
BLM-Utah spokeswoman Megan Crandall confirmed that the agency's wild horse and burro specialists had "gathered and transported" eight wild horses that had strayed into a corral on private land.
The horses were all in good condition, and eventually will be put up for adoption, she said in a written statement. They're being kept at the BLM corrals in Cedar City.
"Eight horses is so insignificant," Miller said, "that it will not satisfy the concerns we all have."
Meanwhile, wild-horse advocates issued a statement saying the BLM was caving into pressure from ranchers when the majority of Americans favor the horses over cattle on public lands
The American Wild Horse Preservation Campaign also questioned the BLM's latest numbers of horses on the Bible Spring Complex, saying it would be "biologically impossible," given the BLM's 2013 estimates.
"We call on the BLM and the state of Utah to exert leadership to resolve the conflicts with ranchers who view wild horses as competition for cheap grazing on public lands," the statement said.
The BLM Utah office is awaiting word on its requests for money to round up an estimated 1,000 wild horses this summer.
Last week, ranchers in Iron, Beaver and Emery counties sued the BLM, alleging it has failed to do its job in managing the horses.
How to comment
The Bureau of Land Management is seeking public comments on its proposal to gather, remove and give fertility-control treatments to wild horses in the Bible Spring Complex between two to four times during a 10-year period.
Its environmental assessment and maps are online.
Written comments will be accepted by email to firstname.lastname@example.org until May 30, or by letter to BLM Cedar City Field Office, Attn: Cedar City Field Office Manager, 176 E. DL Sargent Drive, Cedar City, UT 84721
Live debate: Managing federal lands in Utah
I On May 14 at 7 p.m., The Tribune's Jennifer Napier-Pearce will moderate an Oxford-style debate between three Utahns in support of current federal lands policy and three in opposition.
Once the two sides have debated, the live audience will choose a winner.
The debate is free and open to the public at the Salt Lake City Main Library, 210 E. 400 South. KCPW 88.3/105.3 FM will broadcast it live, and it also will be streamed live at sltrib.com.