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Counting sheep: the National Park Service works to reintroduce bighorn to their historic range.

THWHOCK! A sound like a rifle shot echoes off the surrounding cliffs, rippling outward over the sandstone fantasy of Canyonlands National Park. Then, a second and a third distinctive crack follow, splitting the autumn air.

Two rams materialize on the ridge line overhead, their horns spiraling to nearly full curl. They pivot to opposing stances, stand upright, and walk forward, falling into a headlong lunge.

The larger ram powers from a higher stance. His horn plate explodes off the young ram's right curl and blows the challenger backward over a 15-foot cliff. Twisting and writhing, the sheep tumbles upside down and disappears among the ragged boulders. A puff of dust hangs in the air where the two rams met.

Although it seems impossible for the loser to have survived the fall, be scrambles up trembling, eyes wild, and nostrils flared in alarm, ourwardly intact. The triumphant ram poses momentarily before resuming the less majestic ritual of groveling for ewes. From across the basin comes another, more muffled crack. It is late autumn in Canyonlands, and the desert bighorn rut has started.

Images of dueling bighorn strike romantic chords within us all, but shepherding these symbols of the wild toward the 21st century has been a bittersweet effort. Although there are some bright spots, the bighorn's future seems as rocky as the terrain the animals have come to prefer. The challenge for wildlife management agencies, such as the National Park Service, is coming up with the winning formula for sustaining the species.

Desert bighorn do not respond well to the types of techniques used to build the dwindling numbers of many big game species, and intensive efforts, such as reintroducing the animals in certain areas, have merely slowed the decline. Historically, bands of fewer than 50 individuals do not survive more than 50 years, and herds made up of 50 to 90 bighorn typically do not last beyond 70 years. Only populations of more than 100 sheep have historically remained self-sustaining, and most desert bighorn herds are well below that number.

At Zion National Park in Utah, bighorn were introduced to replace a native herd that had disappeared decades earlier. But this herd, introduced 20 years ago, was nearly destroyed by a combination of cougar predation and an exotic cattle disease--a grotesque sinusitis caused by larvae from the botfly, a parasitic nostril fly.

"We wrote the herd off in the mid-'80s," says state biologist Jim Guymon, who has followed the Zion herd since its introduction. "Then, in 1990 the park began receiving reports of sheep sightings, which led to a helicopter overflight last year." Park officials were elated to count a herd of nearly 40 desert sheep, about half of them lambs, although Zion's herd is far from stable.

In an effort to duplicate the results at Zion National Park in a more predictable manner, the Park Service recently began its bighorn initiative. The steps involve taking a census to find out how many bighorn sheep there are; examining what happened to the transplanted herds to determine which techniques succeeded and which did not; performing genetic and mortality studies to establish herd health; doing habitat inventories to determine the best areas for future reintroductions; and eventually restoring wild sheep to historic park habitats. Among the buttes of Canyonlands, biologists working from a helicopter surveyed the Island in the Sky herd this fall. From there, they moved to the Needles herd, and then farther north along the Colorado-Utah border to Dinosaur National Monument.

"We've got lots of small, isolated populations, which typically don't survive long," said Frank Singer, the Park Service research ecologist charged with coordinating the intermountain region's bighorn initiative. "And a lot of our transplanted herds haven't done too well, so we're looking into how we can improve that. Mesa Verde National Monument in Colorado, for example, is down to three or four animals. Our number one priority for the bighorn initiative is interagency cooperation. With three or four exceptions, you can't manage sheep just within national parks; they're not big enough."

Despite problems with poaching, loss of habitat, and diminishing water supplies, the biggest immediate problem facing desert bighorn is livestock diseases for which they have little resistance. These diseases have ravaged bighorn herds throughout their historic range, an area that once supported huge numbers.

The animal's curling horns are the single most prevalent figure in desert rock art, and turn-of-the-century naturalist Ernest Thompson Seton estimated nearly two million desert sheep roamed North America when the conquistador Coronado first penetrated their habitat in 1540. Successive mineral strikes occurred throughout desert bighorn country from 1849 to 1940, bringing with them displacement, loss of water supplies, subsistence hunting, and diseases.

Although historically desert bighorn used foothill and valley habitat, over time they became a reclusive mountain species. By 1979, biologists estimated only 11,000 to 14,500 desert sheep remained in six Southwestern states. Now, because pressures on the sheep have diminished and management has increased, the population has climbed to 20,000, although no one knows their true numbers with certainty. Desert bighorn are difficult to find and harder to observe. Most live scattered among the mountain ranges of the Southwest deserts in small bands, and most are reintroduced. Many of the sheep used for reintroduction come from herds with higher numbers and healthy populations living on lands administered by either a state agency or the Bureau of Land Management (BLM).

Bighorn reproduction rates are lower than those of most wild ungulates, and their life spans are about ten years. The rutting season is late autumn, and the lambs, which weigh about eight pounds, are born in the most rugged terrain six months after breeding, typically April and May. The average adult bighorn ram weighs 160 to 200 pounds, and ewes, about 105, although the animals' weight can vary 30 percent from summer to winter.

Bighorn range within a radius of about ten to 20 miles and during their travels can come into contact with domestic livestock. Rams' horns provide an unfortunate target for diseases. To limit the weight of rams' horns, which can be as heavy as 30 pounds, bighorn have evolved with numerous hollow sinus cavities honeycombing their skull and horn cores. These sinuses can also form a reservoir for infection, and consequently desert bighorn are susceptible to a variety of sinusitises.

The constant transport of livestock throughout the West has spread disease so efficiently that most wild sheep now carry live organisms, not just the anti-bodies, for a number of ailments: pasteurella, moraxella, bluetongue, bovine sinusoidal respiratory virus, and epizootic hemorrhagic disease. Some of these can be transmitted by flies or gnats, but the original source is domestic livestock. Pasteurella and moraxella, bacterial pneumonias common to domestic sheep, require contact, and stress or poor nutrition may cause these diseases to express themselves.

Sheep seek social contact wherever they can find it, readily mingling with domestic herds, often nuzzling nose-to-nose. Die-offs usually start within ten days after contact with a domestic herd, and bighorn mortality rates of 95 percent are common during the first wave of disease. Surviving adults generally do not show active symptoms, but all of their lambs die before reaching two months of age.

Disease has taken its toll throughout bighorn range. The North and South San Juan herds, which ranged from the Needles District of Canyonlands south to the San Juan River--once the state's largest herd--are gone, virtually exterminated by pasteurella and moraxella. The implications for Rocky Mountain bighorn have been especially pronounced; they remain extinct in huge areas of historic habitat throughout Colorado, Wyoming, Montana, Idaho, Oregon, Washington, and northern Utah where domestic sheep were heavily grazed.

Two subspecies, the California and peninsular bighorns, are listed by the state of California as threatened. The U.S. population of peninsular bighorn was federally listed as a threatened species late last year. Native sheep disappeared from Big Bend in Texas, Colorado National Monument, Arches and Capitol Reef national parks, and Glen Canyon National Recreation Area in Utah. Grand Canyon, Dinosaur National Monument in Utah, Death Valley in California, and Organ Pipe Cactus National Monument in southern Arizona all harbor remnant native populations, which are especially vulnerable to disease.

Aerial counts for the North San Juan herd in the early 1980s regularly turned up 300 desert bighorn. In 1982, shortly after a wild ram was seen mixing with domestic sheep on a BLM grazing allotment near Hatch Point, wild sheep began dying. By 1989, overflights of the North San Juan herd revealed only eight desert bighorn, none of them lambs. Since then, the South San Juan herd and the Needles District Canyonlands herd have followed similar downward spirals. There are no geographical barriers separating sick herds from healthy ones, and bighorn rams are occasionally seen crossing the Green and Colorado Rivers.

Overall, the population of the Colorado corridor herds has climbed, but the potential for a crash similar to the one that obliterated the North San Juan herd is a constant threat. Die-offs related to domestic sheep raged through Death Valley National Monument in 1960 and Lava Beds National Monument in 1980. There is significant danger for any herd when nearby grazing allotments are too close or when vacant allotments are reactivated. Trespass grazing, both intentional and accidental, is relatively common along the edges of remote Southwest parks. Most Bureau of Land Management or U.S. Forest Service sheep allotments bordering bighorn herds have been closed.

Eighty percent of desert bighorn habitat is administered by the Bureau of Land Management, mostly in southern California, southern Nevada, Arizona, and southern Utah. Some of this land is proposed as part of the 1.5-million-acre Mojave National Monument in the California Desert Protection Act. Wildlife refuges, military reservations, Park Service lands, and larger state parks like California's Anza-Borrego account for much of the remainder of the animal's habitat. Although most of the habitat is administered by BLM, much of the land in the Death Valley region of California and along the Colorado River corridor from Canyonlands south through Glen and Grand canyons to Lake Mead is administered by the Park Service.

In some ranges, particularly where mule deer have expanded, cougar predation can be a serious limiting factor. In Nevada's BLM country, 66 percent of all radio-collared bighorn died from lion predation over the course of a decade. Where small, often unwary, bighorn herds are reintroduced into historic habitats, this can be a temporary but troublesome obstacle.

Coming up with money for programs such as the bighorn initiative is not easy. At the same time that Congress appropriated $4.5 million to expand the new visitor center in the Needles District of Canyonlands, biologists with BLM, NPS, and the state were forced to pool their funds like kids buying a skateboard magazine to get $7,400 to pay for the helicopter time needed to count sheep in Potash and Canyonlands. This example further illustrates a shortcoming of the Park Service, which was the focus of a recent report by the Interior Department's inspector general. The report criticized the Park Service for spending too much money on visitor accommodations while ignoring the resources. But in fairness to the Park Service, although the agency may seek money to pay for research, these programs are not always approved by Congress.

Although NPS may have trouble getting funds for bighorn research, some private groups have made the sheep a priority. The Friends of North American Wild Sheep, a sportsman's group, will underwrite a study of the San Juan/Needles epidemic, including blood tests on Island, Potash, and Lockhart Basin sheep to see if the problem is spreading.

Restricted funding is a problem throughout desert bighorn management. In Grand Canyon no one has any idea how many sheep lie tucked among the terraces of the 300-mile canyon. "We've had no funding for any sheep work for some time," says Grand Canyon biologist Johnny Ray. "We're requested it, but nothing has come through. When it comes to sheep, even our field technicians have been laid off." Their limited funds are tekan by species listed as threatened or endangered, such as the bald eagle, Mexican spotted owl, southern willow flycatcher, and hump-back chub, an endangered Colorado River fish.

Although the situation sounds dismal, the picture is more hopeful than it at first seem, and evidence suggests that the decline of the desert bighorn has been halted. In the sizable refuge of Canyonlands National Park, the Island in the Sky herd and its satellites (the Colorado Plateau's largest contiguous population) are doing well. The BLM Potash herd to the north, the Lockhart Basin transplant to the east, and the Canyonlands Maze District herd transplanted west of the Green River are all thriving, Colorado, New Mexico, and Texas each have populations of about 300. Twenty five sheep introduced into Arches National Park in the mid-1980s have grown to more than 50. Perhaps 800 desert bighorn populate the Colorado River herds. To the north, herds introduced to the San Rafael Swell, a BLM area recommended for park designation by NPCA, now total more than 300 sheep. The huge bombing ranges and military reservations of California's Mojave Desert also include large expanses of bighorn habitat where visitation, grazing, and development are negligible, and water sources can be improved for sheep. All of these lands combine with Park Service, state, and BLM lands to form a huge habitat network. The biggest limiting factor to bighorn expansion, in California as throughout much of their range, is lack of water. Their biggest competitors are the abundant feral burros, which denude range and compete for critical water holes.

In the cactus and alkali hardpan of southern California, more than 3,900 Nelson's, another subspecies, and 600 peninsular bighorn inhabit the Sonoran and Mojave zones by incorporating jojoba and barrel cactus into their diet. In Joshua Tree National Monument, the surveys have identified one tenuous population in the Cockscomb Mountains. Bighorn south of Joshua Tree are considered peninsular sheep.

Native sheep are beginning their long climb back to a secure niche in North America's deserts. Unlike the large carnivores, desert bighorn are fairly undemanding in their habitat requirements They need adequate forage, accessible escape terrain, reliable water supplies, and a reasonable level of solitude.

Throughout the Southwest, nearly two-thirds of appropriate bighorn habitat is vacant. "Glen Canyon [National Recreation Area] looks to be one of our most promising areas for expansion," says the bighorn initiative's Singer. With firm segregation from domestic livestock and a well-managed program of reintroductions to their historic range, these magnificent symbols of the desert will continue to grace our Southwest skylines.
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Author:Howe, Steve
Publication:National Parks
Date:Mar 1, 1993
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