Outdoors Blog

Idaho Fish & Game nets bighorns, collects data to improve herds

Bighorns inhabit some of Idaho’s most remote and rugged terrain, and Idaho Fish and Game crews recently captured bighorns in the Challis area and the Owyhee Desert so they can learn more about these important and elusive animals.

It’s challenging work that requires a large, coordinated team. A Fish and Game crew in a helicopter spots bighorns from the air, then a biologist fires a net over a fleeing animal. The helicopter chase is short, or it’s called off.

“If we don’t get the animal fairly quickly, we back off so we don’t over stress it,” helicopter pilot Tony Herby said.

After the bighorn is netted, the helicopter lands and F&G “muggers” blindfold the animal so it won’t panic, hobble its legs, untangle it from the net and carefully place it into a large mesh sack attached to a cable. The cable is hooked to the belly of the helicopter, and the bighorn is flown to a nearby processing area.

After the pilot carefully lowers the bighorn, or a pair of them, to the ground, a team of Fish and Game biologists, technicians and volunteers remove them from the bags and transport them on stretchers to the processing site.

In a flurry of coordinated activity, blood samples are drawn, noses and throats swabbed for cultures and DNA testing for respiratory bacteria. The animals are scanned with an ultrasound machine to check for pregnancy and body condition. Various measurements are taken, including horn length and circumference of the neck.

Ears are checked for any signs of parasites or disease, and biologists fit GPS collars on the animals, along with numbered ear tags. Each bighorn is given several shots to help prevent disease and parasites, and another shot to help them recover from the stress of being captured. During the whole process, the sheep’s body temperature is monitored to ensure it doesn’t overheat.

Each bighorn is carried to a release spot, carefully unhobbled and its facemask removed. The animal pauses to orient itself, then scampers up a steep slope. Some run until they disappear into the terrain, and a few stop and look back, then casually wander away.

From the time they’re netted to when they’re released, it’s typically less than 30 minutes thanks to the experience, efficiency and expertise of their handlers.

All the data derived from each animal is recorded and provides important information about not only the health of the individual, but the status of the herd and even the population.

Where are ewe?

Crews captured and collared 24 ewes and 11 rams in the Challis area near the East Fork of the Salmon River, and another nine rams and a ewe in the nearby Morgan Creek area.

GPS collars transmit the sheep’s location to a satellite. Some will provide two locations per day for four years and others will provide 12 locations per day for two years.

If a sheep dies, the collar emits a mortality signal and location so a biologist can quickly locate the animal and try to determine the cause of death.

It’s similar to Fish and Game’s monitoring of deer and elk because biologists hope to gain a better understanding of bighorn habits and also learn what could be limiting their population.

Most of the collared sheep are females, and knowing their locations will help biologists monitor them during lambing season in late spring. The first few months of a lamb’s life are critical because that’s when they’re most susceptible to disease and predation. Biologists know the ewes were pregnant when they were collared. With locations provided by the GPS collars, biologists can find and observe ewes to see if they give birth to live lambs, and if those lambs survive those critical early months.

“If those numbers are low, that’s a red flag that we may have disease issues,” said Hollie Miyasaki, Fish and Game’s wildlife biologist leading the project.

Biologists are especially interested in sheep that inhabit that East Fork of the Salmon River. Herds there totaled about 200 animals until the early 1990s when disease cut them back to about 90 animals.

“They still haven’t recovered since that crash,” said Greg Painter, wildlife manager for the Salmon Region. “We really need information about what’s driving these herds. If we can come up with answers, it will apply to other herds in the area.”

Fish and Game biologist Bret Stansberry will be tracking and observing the East Fork herd.

“We know they spend winter here, but after that, we’re not sure; it’s anybody’s guess,” he said.

There was similar work done with bighorns in the Beaverhead and Lemhi mountain ranges, he said, and it “really nailed down their seasonal ranges.”

A precarious population

Fish and Game’s historical data on bighorns, archaeological evidence and reports from early explorers indicate bighorn sheep were widely distributed and abundant in Idaho until the late 1800s. Drastic population declines throughout the West followed the arrival of homesteaders and settlers in the late 1800s and early 1900s. It’s believed declines were caused by a combination of unregulated hunting, competition with livestock for forage and disease transmission between domestic and wild sheep.

By 1920, about 1,000 bighorns remained in Idaho, but after restoration efforts, such as strict hunting regulations, habitat protection and translocations of bighorn sheep to historic habitat, the population grew to about 5,000. Then in the late 1980s through the 1990s, disease caused bighorns to die off. By 2010, the statewide population had dwindled to about 2,900 bighorns. It has since grown to about 3,100 animals in 2015.

Fish and Game officials believe there’s potential for more bighorns because only about a third of Idaho’s potential habitat has sheep, and existing populations are low in many areas, like the East Fork. But bighorn management is a tricky proposition. Fish and Game doesn’t just want more sheep, it wants more bighorns in the right places because expanding herds that commingle with domestic sheep could lead to disease outbreaks and die-offs.

The herds in the Challis area are also important because they’re part of Central Idaho’s core bighorn population that stretches through the Salmon River drainage.

“We really want to get a current picture of what’s going on in the East Fork,” Miyasaki said.

The pros and cons of connectivity

Most big-game populations, such as deer and elk, are widely distributed over large geographic areas. If something catastrophic happens to a local herd, other animals can fill the void.

Some bighorn herds are isolated populations, which can pose problems, such as inbreeding. Migration between herds is typically beneficial to maintain genetic diversity and restore herds where a die-off occurred.

But organisms carried by healthy domestic sheep and goats can cause pneumonia in bighorn sheep. Once the disease is transmitted, there is no effective treatment for bighorns. Disease can persist in bighorn herds long after the initial die-off, which can cause lower lamb survival and recruitment for years.

With sheep wearing GPS collars, biologists can track where they roam, especially rams that are known to strike out on long walkabouts.

“They are typically the long-distance wanderers,” Stansberry said.

Ewes, lambs and juvenile rams tend to band together in herds, and older rams usually roam in groups separate from the ewes, except during breeding season.

Knowing where sheep migrate helps biologists know where animals live at different times of year, whether there’s interchange between herds and whether herds or wandering rams were likely to encounter domestic sheep or goats during their travels.

Miyasaki noted it’s also important to get information about the bighorn sheep in the Owyhees because they’ve been relatively disease free, but disease has been found in adjacent herds in Oregon.

Crews captured and collared 28 sheep in the Owyhees, which not only provides locations of the bighorns, it also provides Fish and Game with a baseline medical history on those sheep.

While it’s widely accepted that pneumonia can cause die-offs in bighorn herds, disease issues are not completely understood because some herds recover from an outbreak, while it tends to linger in other herds for years.

More research is also being done to determine the exact causes of diseases that affect bighorns.

“Bighorn sheep respiratory disease is a really complex issue,” Miyasaki said.

Big attractions

Bighorns are important animals that are valued by wildlife watchers and highly sought after by hunters. Hunting tags are limited and valuable. Idaho Fish and Game will offer 91 bighorn tags this year, 89 available through controlled hunt applications and one special lottery tag. Fish and Game also auctioned one tag that sold for $90,000 in January. The application period for controlled sheep hunts is April 1-30, and people can get hunt information at http://fishandgame.idaho.gov/ under the hunting tab.

Bighorns are also popular with wildlife watchers, partially because of their scarcity and the rugged, picturesque terrain they inhabit.

Sheep hunters are dedicated and relentless. Many apply for years and never draw a tag. If a hunter draws a coveted tag, there’s pressure to make the most of the hunt because each hunter is limited to two Idaho sheep in a lifetime , one Rocky Mountain bighorn and one California bighorn.

Jim Warner of Blackfoot is a Fish and Game volunteer and board member of the Idaho Wild Sheep Foundation, which helped with the capture-and-collar project near Challis.

“I’m passionate about wild sheep,” he said. “And I like seeing the work Fish and Game does. This team is awesome.”

Warner drew a sheep tag in 1997, and after passing on several animals, never filled his tag, but he’s still “got the fever.”

Since then, he’s harvested three of the four species of wild sheep that constitute the “Grand Slam” of sheep hunting.

“Bighorns are a unique animal, and there’s something about them that will test your will,” he said.

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