The state Division of Wildlife Resources wants to capture 175 of the fleet-footed animals and relocate them to sites near Price and Vernal.
"This is the most productive area in the state for [pronghorn] and one of the best in the West," said Doug Messerly, the DWR's southern Utah supervisor, as he watched the action from Jakes Knoll, about 12 miles south of Loa.
The helicopter, on loan from the Utah Department of Public Safety, herded as many as 30 pronghorns at a time up a wash that funneled them into the corrals. Messerly and several other workers drove behind the animals to keep them from turning back into the brown hills in this rugged part of south-central Utah.
Inside the 8-foot-high pens, shrouded in curtains to help calm the animals, DWR "muggers" grabbed hold and hauled them out to waiting trailers.
Plans for Wednesday called for capturing 100 pronghorns at the Jakes Knoll site in the Parker Mountains and an additional 75 animals at a reservoir about seven miles south of Bicknell.
Messerly said the annual roundup has been conducted for the past 15 years using about 100 DWR workers and volunteers from other land and wildlife agencies.
Usually wildlife officials from neighboring states take part to get pronghorns for their programs, but this year all the captured animals were to supplement Utah herds.
Messerly said the Parker Mountain herd is estimated at 2,300. The ideal number is closer to 1,500. Conditions like altitude, good forage and precipitation contribute to a healthy herd, and that translates into a low mortality rate for fawns.
Messerly said 40 bucks for every 100 does - and 60 fawns for 100 does - is the ideal distribution.
He said the primary management tool for controlling numbers is an annual hunt, which this year harvested about 400 bucks and 400 does.
"Hunting success rate is about 80 percent," he said. "Our mortality rate on the roundups is only 2 percent."
Teresa Bonzo, a DWR wildlife-program manager, said if the captured animals were leaving the state or were being transferred to establish a new herd, they would have gone through a more extensive screening process. Their blood would be tested, they would be checked for disease and some would be collared or tagged.
But because the pronghorns captured Wednesday were to just supplement Utah herds, the extra work was not required.
Bonzo said the animals would be on the ground at their new homes by Wednesday night.
Next year's roundup might take on an international flavor. Bonzo said Mexico has expressed interest in getting some of the animals and may be on hand next fall.
These annual roundups are considered an important time in the DWR.
"It's an exciting week at the division," said Bonzo. "There's a lot of camaraderie and hard work."
One DWR volunteer, David Hillier, who works as a fiscal officer in Cedar City, is on his ninth roundup.
"I'm a bean counter," said Hillier, "This gets me out from behind my desk and outside."
He said his mugger technique is to wait for one of the frightened animals to jump, and then "clothesline it, and jump on it."
The animals, which can weigh up to 150 pounds and easily run 35 mph, bawled with fear as they were carried by two or more muggers from the corrals to waiting trailers.
Overall, Messerly said he was happy with Wednesday's roundup, considering that everyone was dealing with a wild animal. "They [pronghorns] don't work on our schedule," he said.