Steep slopes of recovery.

• Author: Cohn, Jeffrey P.
• Position: Bighorn sheep, Mexico

Alejandro Espinosa was nervous. It was his first time searching for bighorn sheep in the wild. Espinosa, then a graduate student studying wildlife biology at the University of Nuevo Leon in Mexico, was climbing a steep and dangerous mountain known locally in the Sierra del Viejo of Sonora as "the Wall." After more than an hour of difficult hiking, he and his teacher, Luis Tarango, had reached a narrow cliff. A misstep here might have sent either or both of the men tumbling hundreds of feet down the sheer mountain side.

At that moment Espinosa noticed his legs were shaking. That's normal for your first time in bighorn terrain, Tarango told his student as he pointed ahead to a small herd of the wild sheep on a rocky, only slightly more gradual slope. Espinosa picked himself up and slowly, carefully followed Tarango along the cliff toward the animals. Not surprisingly, by the time they reached the slope, the bighorns had disappeared. Undeterred, the two biologists took careful note of the slope's angle, vegetation, and rock cover, as well as the visibility it provided the shy, nervous bighorns.

Experiences such as this one helped prepare Espinosa for his current job as coordinator of bighorn sheep programs at CEMEX, the Mexico-based international cement company. CEMEX is breeding bighorns in captivity with the aim of reintroducing them to the wild in the Maderas del Carmen Protected Area and, later, elsewhere in northern Mexico. Such private initiatives in Mexico, along with government programs and strictly controlled hunting on both sides of the U.S.-Mexican border, are helping a species once feared in danger of extinction to recover.

"This is an opportunity to have desert bighorns again in northeastern Mexico," an optimistic Espinosa says. "It's an opportunity to restore a magnificent animal that has been gone from this region since the 1950s or 1960s. Restoring bighorns to the wild at El Carmen will help us preserve an important emblem of the Chihuahuan Desert."

Few wild animals have captured the attention of scientists, conservationists, hunters, and the general public alike as bighorn sheep (known in Spanish as borrego cimarron). We admire their powerful bodies, huge horns, and ability to scale steep slopes and move nimbly along treacherous ledges and cliffs. A two-inch ledge may be wide enough for a foothold or at least as an intermediate landing and jumping-off point to another, only slightly less narrow ledge twenty feet away. We also respect their ability to survive and even thrive on cold, snow-covered mountaintops and dry, rocky desert hillsides. And the ritual banging of heads and horns--which alone may weigh thirty pounds--by males during the annual breeding season sparks our imagination and fuels soft drink ads.

Most bighorns are divided into two subspecies--Rocky Mountain and desert. Rocky Mountain bighorns range from British Columbia and Alberta in Canada southeast into New Mexico. Desert bighorns occupy mountainous areas from southern California east to Texas and from Utah and Nevada south into Sonora and the Baja Peninsula in northwestern Mexico. Desert bighorns weigh less, are lighter in color, and have smaller horns than their better known Rocky Mountain cousins. Scientists once divided all bighorns into seven different subspecies or races, but more recent DNA analyses and anatomical studies have found few, if any, differences. "There is no basis for distinguishing most of them," says Rob Roy Ramey, an evolutionary biologist who is the Denver Museum of Nature and Science's curator of zoology.

The settlement of the western United States and Canada plus northern Mexico in the nineteenth century decimated bighorn populations. Explorers, miners, and settlers killed bighorns for food, while later, unregulated trophy hunters shot them for their horns. Introduced domestic burros, cattle, sheep, and goats often out-competed bighorns for grazing sites and water holes. More important, domestic sheep often carry diseases, such as Pasteurella pneumonia, that spread easily and fatally to bighorns. Little or no progress has been made on vaccines to protect the wild...