Thinning the herd: 49 Wild Horse Island bighorn sheep relocate to Dillon's Tendoy Mountains

WILD HORSE ISLAND — Life is good for bighorn sheep on Wild Horse Island — that is, until the helicopter comes, and then it’s time to run for the trees.

For the third-straight year, Montana Fish, Wildlife and Parks employed professional helicopter crews to round up and capture about 50 sheep from the Wild Horse herd, which has outgrown its habitat’s carrying capacity. Thursday morning, however, reports from the island said the sheep were sticking to the trees, making the process more difficult than usual.

“It’s the most efficient way to catch them,” FWP spokesman John Fraley said of the net-gunning procedure. “But they may have caught onto us.”

From the air, net-gunning crews can target specific animals effectively. This year, the goal was 40 ewes, five lambs and five rams; they captured all but one lamb in three days. The alternative, or the old way of doing things, was with a drive-capture operation which herded sheep into nets through a corral, but that process was time-consuming, Fraley said, and made it tough to target specific animals.

With this year’s mild winter and relatively no predation from animals or humans on the island, the Wild Horse Island bighorn sheep population is thriving. Before the transfer, there were 230 resident sheep on the island which calls for a management plan of 125 to roam the 2,164-acre site. Fraley estimated that Wild Horse sheep give birth to about 30-40 lambs each year, although he admits it’s not an exact count.

After capture, the sheep were tied to the helicopter and transported to Big Arm State Park where wildlife veterinarians swarmed, taking blood samples to check for viruses, nasal swabs for mycoplasma and mannheimia (associated with pneumonia) and fecal samples to look for intestinal parasites. The process may seem intrusive, but according to Jennifer Ramsey, a wildlife veterinarian from the Wildlife Health Lab in Bozeman, the extensive health tests are routine when moving animals.

“We want to know what parasites we’re moving with them,” she said. “We have a good history with these sheep, we’ve done this several times and we have never found anything.”

Along with the testing, sheep received Vitamin E and selenium supplements for transport, as well as antibiotic and anti-parasitic shots to boost their ability to combat bacteria and parasites they may encounter at their new home.

“It’s always a risk when you move animals, but we take every precaution,” Ramsey said.

Bighorn sheep have been a real management problem in the Rockies. The disease management is very complex, but density is the one thing biologists can manage effectively. Bruce Sterling, a FWP wildlife biologist out of Thompson Falls, said they still have a way to go with thinning the Wild Horse population.

One of the problems is that with herds around the state being devastated by disease and fatal sicknesses like pneumonia, there aren’t many areas in Montana that have been authorized to accept sheep right now.

“This is one of the premiere spots,” Sterling said. “But because of what happened, those areas – like Rock Creek near Missoula – probably won’t receive new sheep in the next four or five years; you just can’t augment populations right after a disease like that hits.”

All 49 of the bighorn sheep captured on Wild Horse Island last week have been safely released in the Tendoy Mountains south of Dillon. The Tendoy herd peaked at around 250 animals before there were pneumonia die-offs in 1993 and 1999. The herd was last augmented in 2002 with sheep from the Sun River area, and the goal is to boost the population to about 200 animals, Dillon biologist Craig Fager said.

“I stepped up after years of monitoring the population,” Fager said. “We decided it was time to get more sheep in there.”

According to Fager, when these populations get below 50, they tend to sputter along, but can’t climb out of that hole on their own.

The sheep capture began last Thursday, when 21 sheep were captured, processed, and then hauled to the Tendoys. On Friday, eight more sheep were captured and transported. The final 20 sheep were captured on the island on Saturday and released in the Tendoys about 10 p.m. that night to complete the project.

According to Sterling, workers caught a total of 50 sheep in the three days. Unfortunately, on Saturday, one 2-year-old ram died on the island from a fractured neck while being netted.

Funding for this project, and other sheep augmentation and conservation projects, come from the annual auction of a single Montana bighorn ram hunting permit. This year the permit went for $300,000 at the Wild Sheep Foundation auction in Reno, Nev.