A pronghorn's sprint speed of nearly 60 miles per hour is bested only by that of a cheetah, but unlike a cheetah it can keep up a fast pace for miles. This ability interested Stan Lindstedt, an animal physiologist at Northern Arizona University. By studying two orphaned young on treadmills, he found that pronghorn simply maximize the capabilities other mammals share. They have more red blood cells, allowing faster transport of oxygen to muscles. They have virtually no extra baggage in the form of fat.
Pronghorn run so superbly that biologists have questioned what they're designed to run from .
Before the devastation of predators that accompanied European settlement of the West, they had to contend with lengthy pursuits by packs of wolves, but even wolves can't run as fast as pronghorn. Byers postulates that pronghorn, whose lineage goes back 20 million years in North America, evolved as the prey of now-extinct predators. As a result, says Byers, pronghorn evolved the ability to sprint and run long distances. Modern predators are not too slow to catch pronghorn fawns, however. Adult females bear twins in the spring, just when coyotes, bobcats and golden eagles have young of their own to feed.