The pronghorn is a unique North American native. It is a mistake to call them "antelope," as the pronghorn's resemblance to those Old World members of the cow family is rather superficial. No mammal other than the pronghorn has branched horns over a bony core. Males usually shed the outer sheath of the horn after breeding, and then grow a new one.
Pronghorn are reddish tan in color, with a prominent white rump patch. Colorado's smallest ungulates (hoofed mammals), they are only four to five feet long (with a four to eight inch tail), and less than three feet tall at the shoulder. Weights range between 85 and 100 pounds.
In spring and summer, the older, more dominant bucks are solitary and the younger males form bachelor bands of up to 12 individuals. Does with young form small herds. In the winter, there are large herds of mixed sex and age classes. The Pronghorn is extraordinarily fast and can run up to 60 miles per hour. It is considered the fastest animal in the Western Hemisphere.
Just after the turn of the 20th Century, pronghorns were nearly extinct because of unregulated hunting. Today the pronghorn is a big game animal, with annual licensed harvest of about 8,000 animals, from a total Coloradan population of about 50,000.
Range: The pronghorn is endemic to North America. In Colorado, the best places to view a pronghorn are on the eastern plains, in the larger mountain parks and valleys, and on shrublands west of the mountains.
Habitat: Pronghorn generally live in grasslands and semidesert shrublands on rolling topography that affords good visibility. They are most abundant in shortgrass or midgrass prairies.
Diet: Pronghorns are largely browsers, subsisting on sagebrush, supplemented by leafy forage in summer. These food habits allow them to persist alongside cattle (and once alongside bison) with little competition. Mostly they feed in early morning and late afternoon, often lying to rest and ruminate at midday.
Reproduction: Pronghorns mate in the fall from mid-September to mid-October, and give birth in late May to mid-June. Does usually give birth to two fawns. Pronghorns have a lifespan of seven to 10 years.
For more information, see the Natural Diversity Information Source species profile.
By David M. Armstrong
Department of Ecology & Evolutionary Biology
Environmental Studies Program, University Museum of Natural History
University of Colorado-Bouldermausmann@aol.com