March 23, 2008

Bighorns facing smaller habitat

Federal agency wants to reduce protected area by more than 50%

By Mike Lee, Staff Writer

With their chiseled forms, sure-footedness and coiled horns, bighorn sheep have long symbolized the rugged American West. They grace everything from heavy-duty trucks to the helmets of football teams.

But by 1998, bighorns in San Diego, Riverside and Imperial counties had been ravaged so much by disease, harmed by development and preyed on by mountain lions that only 280 remained. They were added to the list of the nation's most imperiled species.

Since then, several public agencies and nonprofit groups have helped bighorn sheep in the Peninsular Ranges of Southern California steadily climb back from the brink of extinction.

Today, about 800 bighorns roam the arid backcountry from the U.S.-Mexico border to the San Jacinto Mountains. Peninsular bighorn sheep also live in Baja California, but they are not included in the population classified as endangered by the U.S. government.

In the spring, visitors to Anza-Borrego Desert State Park can sometimes spot lambs nimbly trailing their mothers across rocky outcroppings in search of water.

But the sheep's recent run of good fortune may be about to end, according to some advocates for bighorn recovery. They are concerned that the U.S. Fish and Wildlife Service has proposed trimming protected sheep habitat by more than 50 percent, from 844,897 acres to 384,410.

“Those of us who have put (the bighorn) recovery plan together are totally shocked. . . . These animals need high-value habitat to make it in this world,” said Mark Jorgensen, superintendent at the desert state park.

In October, Fish and Wildlife Service officials said their 2001 map of the lands considered essential to Peninsular bighorn recovery – classified as “critical habitat” – grossly overstated the core area.

They said their current proposal is based on a revised method for identifying the territory needed for the protection of bighorn sheep. For instance, the agency excluded high-elevation and densely forested areas because federal officials said bighorns typically do not live there.

“We focused on areas that have documented, repeated use by bighorn sheep and contain the specific habitat . . . necessary for bighorn,” said Fish and Wildlife Service spokeswoman Jane Hendron in Carlsbad.

The agency plans to hold public hearings about its sheep-habitat proposal, but has not set dates.

The critical-habitat designation is important because it requires any activities that the federal government undertakes, funds or authorizes to be scrutinized for potential harm to threatened and endangered species.

The Bush administration has dramatically reduced critical habitat for several species. In December, environmentalists filed lawsuits against the Fish and Wildlife Service in U.S. District Court because they said many of the agency's habitat reductions lack scientific justification.

Michael Senatore, a lawyer for the Center for Biological Diversity, which helped bring the lawsuits, said the environmental group is negotiating settlements with federal lawyers.

While those cases play out, bighorn advocates are keeping one eye on whether the Fish and Wildlife Service will adjust its habitat proposal and the other eye on the sheep's well-being in the backcountry.

Jorgensen and others are cautious about proclaiming success for bighorn recovery efforts because of how quickly sheep can succumb to disease. In recent weeks, for example, biologists in Nevada said pneumonia may have wiped out a herd of 110 bighorn sheep in the northwestern part of the state.

“Bighorn (numbers) can plummet a lot quicker than than they can increase,” Jorgensen said. “We need to secure their future before we let our guard down.”

After decades of conservation work and the addition of protective laws, several high-profile species have made big comebacks in recent years. Yellowstone grizzly bears, bald eagles and California brown pelicans have recently made headlines for meeting recovery goals.

Peninsular bighorn sheep are not in that category yet, but they may get there if the overall population holds steady for several years and it increases in some parts of their range.

At the start of the 19th century, as many as 2 million bighorns roamed North America. Today, the Bighorn Institute in Palm Desert puts their numbers at about 70,000.

“They were doing quite well until, unfortunately, humans started throwing some obstacles in their way,” said Randy Rieches, curator of mammals at the Wild Animal Park near Escondido. “This is a species that we owe something.”

As settlers and ranchers spread across the landscape in the 19th and 20th centuries, their domesticated cattle and sheep brought diseases that the wild sheep were not able to fight. Some wildlife experts compare it to the way smallpox and measles decimated American Indians, who lacked immunity to diseases brought to the New World by European explorers.

In 1982, a group of biologists started the Bighorn Institute to help prevent the sheep from dying out in the Peninsular Ranges.

At the time, ewes were producing lambs, but most were dying from bacterial pneumonia, said Jim DeForge, executive director of the institute. He linked pneumonia to diseases such as bluetongue and parainfluenza III that are common in domesticated livestock.

“We couldn't turn the diseases around in the 1980s. All we could do was document it,” DeForge said.

To make matters worse, the building of resorts in the California desert during modern times means that golf courses and homes now cover land that bighorns once roamed. The resorts' lush grass creates what one biologist calls an “attractive nuisance” for the sheep, which may be killed by cars as they enter developed areas.

The reproductive biology of bighorn sheep adds another level of difficulty. Ewes typically have one lamb at a time, which means that populations tend to grow very slowly. The combined result was that the Peninsular bighorn population crashed, from 1,170 sheep in 1971 to 280 in the late 1990s.

At that point, Peninsular bighorns' future was so bleak that they were given federal protections under the Endangered Species Act as a distinct unit of the desert bighorn family.

Within a few years, the sheep's numbers started to rise – to about 400 in 2001 and about 800 today.

Biologists credit the variety of sheep-protection efforts. For instance, the institute started raising bighorn sheep in captivity in Riverside County, releasing them into the wild and then studying them closely to learn details about their health and behavior. To date, 118 bighorns born or rehabilitated at the institute have been added to the Peninsular Ranges.

In addition, land managers started removing livestock from parts of the bighorn sheep's range to control the spread of diseases. In 1987, Anza-Borrego park officials airlifted dozens of wild cattle out of the park.

Those efforts dramatically reduced the disease pressure so that today it is not thought to be a major limiting factor for bighorn recovery.

Despite the gains, biologists note that sheep populations are fragile and swings can be caused by factors as fundamental as rainfall, which dictates how much food the plant-eating animals have in the desert.

On that front, this spring is a good one thanks to a series of winter rainstorms. “We will have a lot of successful reproduction across the desert this year,” said John Wehausen, a bighorn researcher in Bishop for the University of California.


  • Habitat: Steep slopes, canyons and washes in desert regions
  • Diet: Acacia, encelia, sweetbush and other desert plants
  • Range: Parts of Baja California and the Peninsular Ranges of San Diego, Imperial and Riverside counties, including the San Jacinto, Santa Rosa, Vallecito and In-Ko-Pah mountains
  • Threats: Habitat loss, high predation rates and diseases
  • Population in 1998: 280 in the United States
  • Population today: About 800 in the United States
  • Reasons for increase: Captive breeding program, fewer disease outbreaks and habitat protection
SOURCE: Bighorn Institute