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For decades, wildlife biologists and park rangers at Canyonlands and other Southwest parks have worked to restore desert bighorn. These efforts represent a great success story, although the animals' continued recovery is far from ensured.
By Jeffrey Cohn
Sitting atop a knoll in Canyonlands National Park in southeastern Utah, Bill Sloan glanced down the steep, rocky hillside. There, in a wash, stood a dozen bighorn sheep, gazing up at the human intruder. As Sloan mused on the bighorns and their remote wilderness, the animals quietly disappeared around a hillside—only to reappear a half-hour later on a ridge above him. Sloan, a wildlife technician at Canyonlands, says the normally skittish desert bighorns are curious creatures, and if they perceive no danger, may want to get a closer look.
For decades now, wildlife biologists and park rangers at Canyonlands and other national and state parks in the Southwest have taken a closer look at desert bighorns. Their efforts have led to programs to protect the species and their habitat and to restore these magnificent animals to places where few or none were left. The result has been a gradually increasing bighorn population in much of the desert Southwest. Although the desert bighorns' continued recovery is far from ensured, they now represent a "great success story," says Paul Krausman, professor of wildlife sciences at the University of Arizona.
Preservation efforts have been aided by the appeal of the creatures themselves, because few wild animals capture our attention as dramatically as bighorn sheep.
With their powerful bodies, huge horns, and an ability to quickly scale steep, rocky slopes and move nimbly along treacherous ledges and cliffs, their physical presence commands our respect. So, too, does their ability to survive and even thrive in dry mountain or rocky habitats. And the ritual banging of heads and horns by males during rutting season sparks the imagination and even fuels car ads.
Scientists once recognized seven subspecies or races of bighorns, but more recent DNA analyses and morphological studies have found few if any differences among them.
"There is no basis for distinguishing most of them," says Rob Roy Ramey, an evolutionary biologist and the Denver Museum of Nature and Science's curator of zoology. As a result, most scientists now recognize three subspecies.
Rocky Mountain bighorns, the first subspecies, range from British Columbia and Alberta in Canada south into New Mexico and, at one time, east into the Dakotas and Nebraska. Desert bighorns, the second, occupy mountainous areas from southern California to Texas and from Utah and Nevada to Sonora and the Baja Peninsula in Mexico. They also once extended north into Oregon. And Sierra Nevada bighorns, the third, live in the mountains of eastern California in or adjacent to Yosemite, King's Canyon, and Sequoia national parks. Only scattered populations of all three remain.
For their part, desert bighorns are slightly smaller and lighter in color and have smaller horns than the better-known Rocky Mountain bighorns. Adult males can reach 200 pounds or more; females weigh up to 130 pounds. Desert bighorns also have a longer lambing season, which is tied to the winter rains that generate plant growth to feed newborn young.
Before Columbus' arrival, two million wild sheep (including Dall and Stone's sheep in Alaska and northwestern Canada) were believed to have inhabited North America, but more recent estimates put the number at about 500,000. The settlement of the West in the 19th century decimated bighorn sheep populations. Explorers, miners, and settlers killed the sheep for food, and trophy hunters shot them for their horns. Other miners, ranchers, and farmers introduced into the area domestic burros, cattle, and sheep, which often outcompeted bighorns for grazing sites and water holes. More important, domestic sheep carry diseases, such as some strains of Pasteurella pneumonia, that spread easily and fatally to bighorns. Even today, little or no progress has been made on vaccines to protect the animals.
By the 1950s, the number of all wild sheep in North America had dipped below 100,000, says Ray Lee, executive director of the Foundation for North American Wild Sheep. Bighorn sheep had "made the transition from relative abundance to one of the rarest ungulates in North America," Krausman adds. Desert bighorns, in particular, were gone from Texas and northeastern Mexico and later from New Mexico as well. They were also eliminated from or reduced to remnant populations in southern Utah, northern Arizona, Nevada, California, and Sonora, Mexico.
With efforts in a number of areas, that situation has happily changed. The numerous national and state parks and preserves throughout the Southwest protect bighorn habitat, while private groups have bought out grazing allotments from willing sellers, thus reducing competition from domestic animals. Park officials have banned livestock within their boundaries and created buffer zones between wild and domestic sheep. In some places, artificial water holes have been built to replace natural streams and seeps that had dried up or been fenced off as a result of human activity. In New Mexico and, particularly, California, captive breeding centers have bred desert bighorns or taken in sick or wounded animals and released them or their offspring back to the wild. Hunting bighorns has also been strictly controlled. Today, a once-in-a-lifetime hunting permit costs tens if not hundreds of thousands of dollars, with proceeds devoted to bighorn conservation.
In 1964, when Canyonlands National Park was established, a remnant herd of 75-100 desert bighorns remained within the park's boundaries, Sloan says. An equal number of bighorns probably lived on adjacent federal and state lands, some of which moved in and out of Canyonlands depending on the season, number of human visitors, and availability of food. With careful management, the herds in the park as well as on the adjacent federal and state lands increased to about 600 by 1990.
Beginning in the early 1980s, Park Service and Utah wildlife biologists began capturing desert bighorns at Canyonlands and relocating them to other parts of the park and elsewhere in the state. In all, nearly 200 bighorns have been moved to start new herds in nearby Arches and Capitol Reef national parks, and to augment a few remaining bighorn sheep in the San Raphael Swell, a badlands-like area northwest of Canyonlands. Animals have also been relocated from Lake Mead National Recreation Area to bolster the herds at Grand Staircase-Escalante National Monument and Glen Canyon National Recreation Area in southern Utah.
These and other relocations have helped desert bighorn numbers rebound in southern Utah. James Karpowitz, the Utah Division of Wildlife Resources' bighorn program coordinator, estimates there are 800-900 bighorns in the San Raphael Swell, now the state's largest herd, and 550 in Grand Staircase-Escalante National Monument. In all, Karpowitz thinks Utah now holds nearly 3,000 bighorns, up from maybe as few as 1,000 in 1975 and well on the way to the stated goal of 3,800 by 2005. Smaller gains have been made in New Mexico and Texas, where bighorns have been reintroduced after their extirpation.
Nevertheless, the desert bighorn story is not one of unmitigated success. Bighorn numbers have dropped precipitously in some areas in recent years, and the animals have disappeared from others. Even where healthy populations still exist, wildlife biologists worry that human development prevents bighorn herds from using all of their traditional habitat and individual sheep from moving from mountain to mountain, thus limiting gene flow between populations.
Indeed, a cyclic decline in population in southeastern Utah has negated some of the previous gains. Canyonlands supports about 350 bighorn sheep, with separate herds in each of the park's districts. Some of the herds have suffered losses. In the Needles section of the park and adjacent lands to the south, bighorn numbers dropped from 200 to 60. Nobody knows why the numbers declined, although Craig Hauke, the park's natural resources specialist, thinks global warming and drought may be at least partly to blame.
Others, however, suspect that increased tourism is forcing desert bighorns to abandon parts of their habitat. The number of visitors at Canyonlands alone has risen from 282,000 in 1990 to 401,000 in 2000. Brigham Young University wildlife biologist Jerran Flinders would like to work with scientists from the Bureau of Land Management and Utah state agencies on a two-year study of whether and to what extent bighorn habitat use is altered by human activities. The Park Service did its own recently published study on similar issues.
Although the bighorns in and near Canyonlands are doing fairly well, the animals are not faring so well in Arizona and California.
No bighorns have been seen in the Santa Catalina Mountains north of Tucson since 1998, Krausman says. In fact, the only bighorns remaining in the Tucson area are 35-50 animals in the Silverbell Mountains to the northwest. That herd is threatened by copper mining in the new Ironwood National Monument. Krausman blames the disappearance of the Santa Catalina bighorns on several factors: housing, road, and shopping mall developments built right up to the borders of Coronado National Forest; increased use of trails by hikers and their dogs; and U.S. Forest Service policies to put out forest fires. Lack of fire encourages the growth of woody shrubs and small trees, which provide hiding places for mountain lions and other predators. Bighorns prefer grassy areas where they can see long distances.
Increased human activity along with habitat fragmentation and a growing mountain lion population in southern California may also be causing a decline in desert bighorns in the San Jacinto, Santa Rosa, and Vallecito Mountains. Listed as endangered by the U.S. Fish and Wildlife Service in 1998 at the urging of NPCA and other groups, these desert bighorns living in the peninsular ranges number about 400, down from 1,200 in 1979, says James De Forge, executive director of the Bighorn Institute in Palm Desert, California.
Despite the challenges, gains have been made. Twenty bighorns were relocated from the San Raphael Swell in 2000 to start a new herd along the Dolores River in southwestern Colorado. Sierra Nevada bighorns now total 250, up from 100 in 1995. And a Center for Biological Diversity lawsuit forced the Forest Service to designate 850,000 acres of critical habitat for desert bighorns in southern California. These challenges underscore the importance of the work by the Park Service and other federal agencies in Canyonlands as well as other Southwestern parks.
For his part, the National Park Service's Sloan remains confident of the desert bighorn's future. "There's still a lot of unoccupied bighorn habitat in Utah and elsewhere," he says. "Our goal is to fill up those areas." Sloan points to the San Raphael Swell herd as a reservoir for further relocations and proudly states: "Those animals may be a step removed from here, but the genes of that herd came from Canyonlands."
