Conservation efforts aimed at restoring bighorn sheep population in Nevada, other western states

By Kate Yoshida, New York Times

Sunday, Jan. 12, 2014 | 2 a.m.

BOULDER CITY — The two-way radio crackled to life: “We’re coming in with three ewes and a young ram.”

Two minutes later, a helicopter appeared on the horizon, four large nylon bags slung below its belly. It touched down in a rocky basin, gently so as not to jostle its delicate cargo. A dozen workers and volunteers rushed forward to release the bags, each one holding a blindfolded desert bighorn sheep.

These wild sheep, captured not far from Las Vegas by the Nevada Department of Wildlife, were destined for release in the Grand Staircase-Escalante National Monument in Southern Utah. Relocations like this one are part of a far-reaching conservation plan to help re-establish bighorn sheep in their historic range across the western United States.

Bighorns are descended from wild Siberian sheep that crossed the Bering land bridge to North America about 100,000 years ago. These herds spread southward, diversifying and adapting to local habitats. Bighorn sheep — named for their immense, curling horns, which can weigh up to 30 pounds — inhabit steep, barren terrain that few other species can tolerate.

Thanks to their hardiness, bighorn sheep have long been a symbolic species. Early Native Americans carved their likenesses into rocks, and the first settlers embraced them as symbols of the rugged wilderness of the American West. At their peak, more than 2 million bighorns roamed the West, gracefully cavorting on rocky hillsides from California to Nebraska.

But by the late 19th century, bighorn sheep were in trouble. The domestic sheep industry had taken hold in the West, and wild sheep had no immunity against diseases introduced by European livestock. As millions of domestic sheep inundated the landscape, deadly pathogens such as scabies and pneumonia decimated the bighorn population. Unregulated hunting took a toll on the few wild herds that remained.

By 1940, the bighorn population had plummeted to fewer than 20,000, isolated in tiny enclaves scattered across the Western states.

In recent decades, state wildlife management agencies have undertaken extensive conservation work to help bring bighorn sheep back from the brink. Much of the work focuses on capturing bighorns from successful herds and relocating these sheep to other areas where the species once thrived.

To find those areas, state agencies looked to an array of sources, from archaeological studies of Native American hunting grounds to the expedition notes of Lewis and Clark.

Biologists then carried out surveys to assess whether the areas could still support wild sheep. Highways, housing developments and solar fields now dominate much of the once rugged Western landscape, leaving large areas uninhabitable for bighorns. Elsewhere, mining has polluted water sources needed to sustain big game.

Once wildlife managers pinpointed habitats where bighorns could still thrive, “it was just a matter of organizing our ability to figure out how to successfully and humanely capture those animals,” said Mike Cox, a staff biologist with the Nevada Department of Wildlife.

Biologists found that the most effective and safest way to capture wild sheep was to fire large nets at them from moving helicopters. The bighorns, which can weigh several hundred pounds, are carried in bags beneath the helicopter to a handling area where veterinarians draw blood samples and examine the sheep for injuries and signs of disease. If the sheep are healthy, they are loaded onto a large trailer and transported to their new home.

So far, more than 2,000 sheep have been successfully transplanted in the U.S. and Canada. These transplants “are probably the biggest thing we’ve done” to help increase the bighorn sheep population, said Paul Krausman, a professor of wildlife conservation at the University of Montana.

This type of intensive conservation work has helped increase Nevada’s bighorn population to more than 11,000, from a low of 2,000 in the mid-20th century. The number of desert bighorn sheep, the rarest subspecies, has more than tripled in Nevada since 1967.

But success has brought risks, as well. Booming bighorn populations have increased the possibility of contact with livestock, putting the wild sheep again at risk for disease.

So the Nevada wildlife agency is careful to leave large buffer zones — ideally at least 20 miles — between the transplanted bighorns and the 70,000 domestic sheep scattered across the state.

“We just don’t want to play Russian roulette with wild sheep,” Cox said.

But the movements of wild and domestic sheep are not always predictable, and the spread of disease can be difficult to stop.

“Without a doubt,” said Kevin Hurley, the conservation director of the Wild Sheep Foundation, a nonprofit group, “one of the biggest challenges we have is this whole contact issue between domestic sheep and goats and wild sheep.”

Illnesses transmitted by livestock are threatening several bighorn herds in the Western states. A lethal strain of pneumonia recently ravaged herds near the Old Dad Mountains in California, killing more than 100 wild sheep. In September, a yearling desert bighorn in one of Southern Nevada’s most productive herds tested positive for pneumonia, prompting the wildlife agency to delay some of its relocations.

But state wildlife agencies must contend with politics when it comes to livestock. If the only goal were the conservation of bighorn sheep, the ideal policy would be to limit the size and scope of domestic sheep farms. But that is impractical, given the strong influence of the livestock industry in states such as Nevada.

To limit contact between domestic and wild sheep, the Utah chapter of the Wild Sheep Foundation has spent more than $4 million since 1994 to buy out domestic sheep farms on publicly owned land. Sheep farmers accepting these buyouts must either switch to raising cattle, which do not transmit disease to wild sheep, or retire their grazing rights to the land.

Surprisingly, many of the nonprofit groups that champion the conservation of bighorn sheep, including the Wild Sheep Foundation and the Fraternity of the Desert Bighorn, based in Las Vegas, are made up almost entirely of hunters. Hunting bighorn sheep and other big game is legal in Nevada and other Western states, but hunting opportunities are meted out carefully by state agencies based on annual population estimates.

“It truly is hunters and fishermen that pay the cost of wildlife management,” Hurley said. “It’s a way that they can put something back into the resource that maybe they’ve hunted, maybe they haven’t, maybe they’d like to.”

Beyond financing buyouts of domestic sheep farms, hunting interest groups also sponsor habitat improvement projects and costly conservation efforts carried out by state agencies. An operation to relocate two dozen bighorns can cost $25,000 or more.

A large portion of state wildlife agencies’ budgets also comes from hunting revenue. About half of the financing for Nevada’s wildlife agency, for example, comes from federal taxes on equipment like rifles, ammunition, bows and arrows. Another third comes from the sale of hunting licenses in Nevada.

Although partnerships with hunters have made possible the conservation of bighorn sheep and other big-game species, some experts worry that such heavy reliance on hunters is unsustainable over the long term. If interest in hunting dwindles, these experts warn, conservation projects may need a broader base of financial and logistical support.

“What we need to do is get the public committed,” said Karen Layne, a member of the Nevada Board of Wildlife Commissioners. “It’s the general population’s wildlife, and that general population — the nonhunters — needs to be involved in this process, as well.”

But conservation advocates say there is “a lot of reason to be optimistic and hopeful,” as Hurley put it.

And after the desert bighorn capture in Nevada, there were 25 new reasons: ewes, lambs and rams loaded in a stock trailer bound for Utah. In a matter of hours, these wild sheep would be exploring the steep, craggy hillsides of their new home, helping restore the species to a landscape where it once flourished.