Even though the Sonoran pronghorn is the fastest land mammal in North America, capable of speeds up to 60 miles an hour, the endangered animal may not be swift enough to outrun the imminent threat of extinction.
The Sonoran pronghorn, Antilocapra americana sonoriensis, is a desert subspecies. Only about 30 of the animals remain in the United States-and another 350 to 400 in northern Sonora, Mexico. They are found in two areas of the Sonoran Desert of southwestern Arizona and northern Mexico, areas that include Organ Pipe Cactus National Monument and Cabeza Prieta National Wildlife Refuge in Arizona and coastal plains and bajadas in Sonora, Mexico.
For most of the 19th century, the Sonoran population numbered in the thousands. Then, in the late 1800s, as settlers arrived in the Southwest, land was cleared for farms and homes, fences were erected, and habitat and range disappeared. Hunters also killed the animals for food. By 1915, the Sonoran pronghorn population had dwindled to about 1,500. In 1967, the animal was listed as endangered.
Today, factors such as habitat loss and fragmentation, disturbance by human activities such as illegal immigration, smuggling, interdiction efforts, other land uses, and a recent drought continue to keep the animals' numbers low. Unlike white-tailed deer, pronghorns do not jump fences, and fawns also fall prey to coyotes, mountain lions, and bobcats.
The Sonoran pronghorn is one of five subspecies that include the American or common, which is widespread throughout the West, the peninsular, the Chihuahuan or Mexican, and the Oregon. Smaller than a white-tailed deer, the Sonoran pronghorn stands less than three feet at the shoulders. Its overall body length, including the tail, is between 48 and 57 inches. Males can weigh 90 to 130 pounds, and females, 75 to 110 pounds. The upper part of the pronghorn is a rich tan color. Its underpart, rump, and two bands across the neck are white. A short two- to four-inch black mane runs down the back of the neck, and males have a black mask and black cheek patches.
The animals have eyes that are set high on their heads and are very large. They can see something moving as far as four miles away. Pronghorns can sustain a speed of 35 miles an hour for long distances. Their speed and keen eyesight help them to avoid predators, although both Euro-American and American Indian hunters used the animals' natural curiosity to lure them into traps.
Pronghorns live in broad, subtropical desert valleys and rugged mountain ranges. Daytime summer temperatures can exceed 110 degrees, and winter nights can drop close to freezing. Sonorans feed on various plants, including forbs, grasses, shrubs, and cacti.
Despite what may seem like tough odds, the U.S. Fish and Wildlife Service, National Park Service, Arizona Game and Fish Department, U.S. Air Force, U.S. Marine Corps, and Bureau of Land Management are working to rebuild the population. The Fish and Wildlife Service is trying to establish a second Sonoran population that can remain stable for five years. The challenge is that 30 pronghorn are needed from the current population-a substantial number from an already diminished group. The recovery team is trying a semi-captive breeding effort to rear enough pronghorns to repopulate the U.S. range.
Timothy Tibbitts, a wildlife biologist at Organ Pipe Cactus National Monument, says the Sonoran's removal from the endangered list is doubtful in the foreseeable future. Increasing the number of Sonoran pronghorn, Tibbitts says, requires the reduction of human activity in the animal's current range and protecting existing habitat. "Border-related activity is most damaging-illegal immigration, drug smuggling, and related interdiction activities-all while the animals are stressed by a significant drought," he says, adding that even recreation and some military training probably contribute to the problems.
The same threats endangering the pronghorn landed Organ Pipe Cactus on NPCA's list of America's Ten Most Endangered National Parks this year.
Even though recovery will not be easy, Tibbitts sees benefits to reestablishing the animals. "If Organ Pipe can no longer support the species, then [it] can no longer provide the healthy ecosystems and wilderness environment that [it] is charged to provide to the public. It would be like Grand Canyon without all those rocks."
