Pronghorn Facts

Adults run 4 to 5 feet long, stand 32 to 41 inches at the shoulder, and weigh 90 to 150 pounds, bucks heavier than does. The coat is tawny with a white belly, rump patch, and throat bands that flash in flight, and bucks grow branched horns with a forward-pointing "prong" — uniquely among horned mammals, pronghorns shed the outer keratin sheath each year and regrow it over a permanent bony core. The body is a running machine: huge eyes give nearly panoramic vision, and oversized lungs, a large trachea, a strong heart, and light limbs support bursts near 55 mph and, more importantly, sustained high cruising speeds few predators can match — an endurance biologists link (plausibly, if not provably) to now-extinct American cheetahs that once hunted them. It is the only living antilocaprid; its nearest relatives are other giraffoid ruminants, not the Old World antelopes it resembles by convergence. Tellingly, faced with a fence a pronghorn looks to crawl under rather than leap.

Pronghorn favour open grassland, shortgrass prairie, and sagebrush steppe where they can see far — dense forest blocks their whole defense of early detection and escape. Once ranging across much of western and central North America, they hold strong populations today in the western U.S., southern Canada, and parts of northern Mexico. Some herds still migrate tens or hundreds of miles between seasonal ranges, and because pronghorn duck under fences rather than jump them, those routes funnel through narrow bottlenecks where dense fencing or construction can cut a herd off from otherwise ample habitat. Summer ranges supply nutritious forbs for does and fawns; winter ranges need shrubs standing above shallow snow, since deep crusted snow blocks both movement and food.

Pronghorn are selective browsers more than grazers, eating sagebrush, forbs (broadleaf wildflowers), shrubs, and tender grasses, plus cactus and other plants in dry country, and fermenting the fibre in a four-chambered ruminant stomach. Rather than cropping short grass like the American bison, they pick nutritious, higher-protein bites as they move, which lets them thrive on land that looks sparse. Sagebrush is especially valuable in winter because its leaves stay available when annual plants dry off or snow covers low forage, and water comes from pools, snow, and plant moisture — so concentrating livestock or development around limited water can displace herds even where forage is intact.

Outside breeding, pronghorn form loose mixed herds that scan the horizon together, sharing vigilance so each animal spends less time watching and more time feeding; alarmed, they flare the white rump hairs into a conspicuous flash that spreads through the herd and signals a predator it's been spotted, then flee in a bounding rush. They rely on vision, numbers, and speed rather than the pack tactics of canids. In the late-summer or autumn rut, bucks mark vegetation with scent glands and either defend a territory or guard a group of does, testing rivals through posture and sparring.

Breeding is in autumn, and after a long gestation of about 250 days does birth one or two fawns in spring as green forage returns. Twins are common in well-nourished mature females; the doe separates the newborns and visits each hiding spot to nurse, so one predator is less likely to find both. Nearly scentless and still, fawns lie hidden for the first days, then grow fast on rich milk and join nursery groups, running nearly as fast as adults by late summer — though coyotes, bobcats, golden eagles, and severe weather still cause heavy early loss. Wild pronghorn often live 10 to 15 years.

The pronghorn is Least Concern overall, many western populations stable after strong recoveries from near-collapse in the early 20th century — but that category hides regional differences, and desert subspecies like the Sonoran and peninsular pronghorn remain rare and dependent on active management. The pressing threats are habitat fragmentation, highways, impermeable fencing, energy development, and drought. Conservation works directly on movement: wildlife-friendly fences with a smooth, raised bottom wire that lets animals pass beneath, removal of obsolete fences, overpasses and underpasses on busy highways placed at established routes, and protection of large blocks of native grassland and sagebrush for winter forage and fawn cover.

• IUCN Red List of Threatened Species: Antilocapra americana
• National Park Service: Pronghorn
• U.S. Fish & Wildlife Service: Pronghorn
• Smithsonian's National Zoo: Pronghorn