The North American pronghorn (Antilocapra americana) is the surviving member of a group of animals that evolved in North America during the past 20 million years. It is not a true antelope, which is found in Africa and southeast Asia. The use of the term “antelope” seems to have originated when the first written description of the animal was made during the 1804–1806 Lewis and Clark Expedition.
Spring migration of Pronghorn herd heading back to Yellowstone
Males (bucks) weigh 100–125 pounds and females (does) weigh 90–110 pounds. Adults are about 45–55 inches in length and 35–40 inches tall at the shoulder. Pronghorns have distinct white fur on their rumps, sides, breasts, bellies, and across their throats. Both sexes of pronghorn have antlers, with the males being significantly larger. The horns develop a keratinous sheath which is shed and regrown on an annual basis. The horn sheaths of the pronghorn are branched, each sheath possessing a forward-pointing tine (hence the name pronghorn). Males have a horn sheath about 4.9–16.9 inches (with the average of 9.8 inches) long with a prong. Females have smaller horns that range from just 1–6 inches (with average being 4.7 inches) and are sometimes barely visible. Female horns are straight and very rarely pronged. Males are further differentiated from females in having a small patch of black hair at the angle of the mandible (jaw).
Pronghorn buck in Lamar Valley
Pronghorn have an average life span of 7–10 years. They have a distinct, musky odor. Adult males either defend a fixed territory that females may enter, or defend a harem of females. A pronghorn may change mating strategies depending on environmental or demographic conditions. The doe gives birth to their young (fawns) in late May–June and usually has 1-2 fawns. They form mixed sex groups in the winter. In early spring, the herds break up, with young males forming bachelor groups, females forming their nursery groups, and adult males living in solitaire. Pronghorn are the fastest land mammal in North America and can run for sustained sprints at 45–50 mph.
Pronghorn doe cleaning her new fawn near Yellowstone’s North Entrance Gate
Pronghorns prefer open, expansive terrain, usually grasslands. They are most often found in elevations varying between 3,000 and 5,900 feet elevation, with the densest populations in areas receiving around 9.8–15.7 inches of rainfall per year. They eat sagebrush, other shrubs, forbs, and some grasses. There are an estimated 350-400 Pronghorn in the park. Cougars, wolves, coyotes, and bobcats are their major predators. Golden eagles have been reported to prey on fawns and adults.
Pronghorn buck in Lamar Valley, note male distinguishing black line of fur at jaw
Where to find Pronghorn in Yellowstone:
- Summer: Lamar Valley; some may be near the North Entrance near Gardiner, Montana.
- Winter: between the North Entrance and Reese Creek.
Pronghorn can be viewed outside of the park, where they migrate to lower grasslands each winter. I’ve also viewed Pronghorn in the meadows of Grand Teton National Park (Wyoming), National Bison Range (Montana), Custer State Park (South Dakota) and Wind Cave & Badlands National Parks (South Dakota). They are commonly seen across Wyoming, Idaho, Southern Montana, and Northern Colorado.
