BIG ARM — The still winter air was whipped into windy chaos as a helicopter roared toward the ground at Big Arm State Park last Wednesday.

But this wasn’t just any routine helicopter landing.

Bound and blindfolded, several bighorn sheep from nearby Wild Horse Island dangled from the chopper like a link of sausages before being gently draped across the ground.

Almost as soon as the live cargo was disengaged, a swarm of wildlife biologists from Montana Fish, Wildlife & Parks (FWP) advanced toward them to administer a series of medical tests before loading them into trucks.

The procedure was all part of an official two-day relocation operation done on an almost annual basis to keep Wild Horse Island’s bighorn population in check while using the captured sheep to augment other herds around the state.

“There are different herds that can use a boost,” said FWP regional spokesman, John Fraley.

For years, FWP has used Wild Horse’s contingent of bighorns as a “nursery herd”. This year’s crop was divided between herds in the Kootenai Wildlife Management Area and Berray Mountain, in the Bull River drainage north of Noxon. In total, the Kootenai herd was the destination for 26 rams and six ewes, while the Berray Mountain subpopulation welcomed 11 rams, 15 ewes and one male lamb. In 2012 - the last year that the roundup was held - a total of 49 sheep were sent to the Tendoy Mountains near Dillon.

Prior to being released in their new habitat, it is essential to ensure that the transplanted sheep are healthy and free of disease.

“It’s a pretty clean herd with a good herd history,” said wildlife biologist Neil Anderson, noting that the inspection process includes throat and nasal swabs for mycoplasma and pasteurella - two ailments tied to pneumonia die-offs that have profoundly impacted the state’s bighorn sheep in the past. Anderson and other FWP biologists also checked blood samples for viruses, fecal samples for parasites and examined the overall body condition of each sheep.

Remarkably, Fraley said that the calm sheep do not need to be sedated prior their aerial abduction or their check-up.

“They just kind of give up,” he said.

Not all of the sheep come quietly, however.

“The big rams were pretty aggressive,” Fraley said.

Besides occasionally provoking some aggression, in rare instances, the capture can also stress the animals, causing their body temperature to rise. For that reason, the cold weather is necessary to conduct the roundup, and biologists stood at the ready with cold water and heaps of snow, in case certain distressed animals required emergency cooling. Despite the safeguards in place, one sheep died in this year’s roundup and another escaped on site.

In addition to boosting the numbers of other herds, the roundup is also beneficial to the Wild Horse Island population, itself.

Bruce Sterling, another FWP biologist on hand, said that although coyotes and mountain lions have been documented on the island, rates of predation are low. Therefore, the roundup is the primary mechanism for regulating the bighorn population, which had significantly exceeded its carrying capacity.

“There’s no big predator that’s playing any kind of a factor out there [on the island],” said Sterling.

A minimum of 155 bighorn sheep had been observed in an aerial survey of the island on Feb. 18. Wildlife managers attempt to keep the number around 100 individuals.

The roundup was conducted in cooperation with the Confederated Salish and Kootenai Tribes, while the capture and flight of the sheep was performed by a helicopter wildlife service contractor. According to FWP, the day’s activities were funded entirely by the “annual auction of a single Montana bighorn ram hunting permit through the Foundation for Wild Sheep.”