The pronghorn is a species of artiodactyl mammal endemic to interior western and central North America. Though not an antelope, it is often known in North America as the prong buck, pronghorn antelope, or simply antelope, as it closely resembles the true antelopes of the Old World.
The pronghorn can run exceptionally fast, being built for maximum predator evasion through running, and is generally accepted to be the fastest land mammal in the Western Hemisphere.
The top speed is very hard to measure accurately and varies between individuals; it can run 35 mph for 4 mi (56 km/h for 6 km), 42 mph for 1 mi (67 km/h for 1.6 km); and 55 mph for .5 mi (88.5 km/h for .8 km).
It is often cited as the second-fastest land animal, second only to the cheetah. It can, however, sustain high speeds longer than cheetahs.
University of Idaho zoologist John Byers has suggested that the pronghorn evolved its running ability to escape from extinct predators such as the American cheetah, since its speed greatly exceeds that of extant North American predators.
It has a very large heart and lungs, and hollow hair. Although built for speed, it is a very poor jumper.