Staking out survival for Sonoran pronghorns: racing against extinction, the fastest land mammal in North America is the focus of new recovery efforts on both sides of the U.S.-Mexico border.

• Author: Ikenson, Ben

At the U.S.-Mexico border in southwestern Arizona, the old Peligroso/Danger signs dangling from the barbed wire do little to stop a furtive flood of foot traffic through the desert, despite its unforgiving conditions. In fact, this was the grim scene where fourteen undocumented Mexican immigrants tragically perished in May 2001, and where more than two hundred have since perished in the searing heat.

But while people are ill-equipped to survive the harsh conditions of the Sonoran Desert, a subspecies that has inhabited the region since well before human history, the Sonoran pronghorn, may be even less able to handle the modern, widespread consequences of human activity there. In conjunction with recent extended periods of low rainfall during hot summer months, range fragmentation and habitat degradation are presenting serious problems for the Sonoran pronghorn, which was listed as an endangered species in 1967.

A goatlike animal often mistaken for a relative of the African antelope, the Sonoran pronghorn is one of five subspecies within the unique Antilocapridae family. The species descended from prehistoric antilocaprids, who roamed North America during the Eocene epoch some thirty million years ago. By the end of the Pleistocene, all were extinct but one: the pronghorn (Antilocapra americana).

The fastest land mammal in North America, and possibly the second fastest in the world after the African cheetah, pronghorn can reach speeds of up to sixty miles per hour. Unlike the cheetah, who tires after a quarter-mile burst of energy, the pronghorn can maintain its top speed for about four minutes, and clip along steadily at thirty miles per hour for up to five miles.

Scientists believe the Sonoran pronghorn developed its extraordinary speed and stamina millions of years ago, when the continent was populated with swift, large carnivores, including saber-toothed cats, lions, and two species of American cheetah. These have since gone extinct, leaving healthy adult pronghorn free from all but the craftiest predators.

In more recent times, pronghorn became a regular component of the human diet for nomadic Native Americans such as the Shoshoni, the Bannock, the Ute, the Paiute, and the Gostiute. These tribes came together annually for three weeks to partake in a great pronghorn drive, forming a large circle and closing it inward until the prey could be harvested. Beyond mere sustenance though, the hunt functioned as a cultural celebration whereby cross-tribal marriages were arranged and spiritual rites were conducted.

A Blackfeet legend tells how the pronghorn came to inhabit the prairie: When the Creator turned the animal loose on the slopes of the Rockies, its great speed was not suited to the tricky terrain, where it stumbled and fell. The pragmatic Creator hastily relocated the pronghorn to the prairie where it flourished, at least for a while.

But by the turn of the twentieth century, the entire pronghorn species, which had numbered as high as forty million, was reduced to twenty thousand. Evidently, nothing in nature could prepare the pronghorn for the introduction of a relatively modern human invention: the rifle. Hunting in the nineteenth and twentieth centuries greatly contributed to the rapid decline of the entire species. Market hunters slaughtered millions of pronghorn and continued to do so even after the value of the meat diminished because it was so plentiful. Often, carcasses were simply left; to rot wherever bullets brought them down.

As settlers cleared land and staked fences, pronghorn, which unlike deer, will not jump fences, were finding less forage and less room to roam. Also, many ranchers shot pronghorn, believing, falsely, that they competed with livestock for forage...