Pronghorns

The pronghorn, Antilocapra americana, is the only living species in the family Antilocapridae.  All of the animals in this family are native to North America, having diverged from a common ancestor in the giraffe family during the Early Miocene period about 14 million years ago.   During the late 1800s, populations were estimated to be between 50 and 100 million animals, roaming from southern Canada to Arizona and eastern California to the Rocky Mountains.  Fencing of land for ranching and farming severely impacted migration and breeding opportunities.  These restrictions, along with hunting, reduced pronghorn populations to 20,000 by 1925.  Establishing open range areas, including National Park land, and limiting hunting helped the pronghorn population grow back to about a half-million by the late 1900s.

Pronghorns are deer-like mammals with bright white cheeks, bellies, and rumps against a reddish-tan body.  Their short mane stands erect at 3″-4″ high.  Bucks have a black neck patch and a broad black band running from their eyes to a black nose.  Black horns grow to 12″ for females and up to 20″ on males, curving backward and inward with one prong jutting forward.  Their eyes are large and set out  from the skull allowing them to detect movement at distances of up to four miles.  Teeth grow continuously in response to wear from eating rough grasses and brush.  Pronghorns have hollow-core hairs covering their bodies.  When the hair lies flat, it provides excellent insulation for colder temperatures.  The hair can also stand erect, allowing cooler air to circulate next to the skin during summer heat.

Pronghorns live in herds, a lifestyle that has several advantages for non-hunting animals living in flat, open terrain with large predators.  Defense against predators is better when there are more pairs of eyes watching.  More animals together in a herd also means there is the possibility of many fighting back against a predator.  Herds keep males and females in closer contact at breeding time helping to synchronize mating cycles so that all young are born at the same time and can be cared for by many adults.  Pronghorns warn distant herd members of predators by flaring long white hairs on rump patches  that give a flash that is visible over long distances.

Dominant males establish territories early in the spring and defend these using loud snorts, chasing away competitors, and butting with their horns.  Mating takes place in autumn, followed by seven months of gestation, with one or two fawns born in late spring.  Newborn fawns lie quietly in tall grass, while mother feeds some distance away so as not to give away the fawn’s location to predators.  She will visit each fawn several times a day to nurse.  After 7-10 days, the fawns are strong enough to join the herd.  Pronghorns are active night and day, catching snatches of sleep whenever possible while feeding.  Herds migrate annually, following no set path, but going where food sources are available.  While they avoid mud, rivers and streams are easily crossed as they are excellent swimmers.

Pronghorns are a unique native species of North America.  The biggest threats to pronghorn today are oil exploration and strip mining as well as roads and fences across migration routes from spring breeding to winter grazing locations.  They have the longest land migration of any species in the United States.  Pronghorns are the second fastest animal on land, able to run at 70 mph for three to four minute bursts,  while the cheetah is faster for short distances, pronghorns are the long distance champs, able to sustain 30 mph for distances in excess of 15 miles.  You can see them at many zoos across the United States, or keep your eyes open as you travel their favorite range in southwestern Wyoming.