Pronghorn antelope are indeed unique animals. Confusion has always surrounded these sagebrush flat animals, coming in part from many people simply calling them antelope. The Lewis and Clark Expedition first listed them as “goat-antelopes,” but they are not goats and no antelopes exist naturally in North America. They are uniquely American, the single species, Antilocapra Americana, in the Antilocapridae family.
These are small mammals, mature bucks standing only 35” high at the shoulder, with bodies no larger than domestic sheep, just carrying longer legs and necks. Mature bucks weigh 120 pounds and does weigh 90 pounds at the most.
They are the second fastest land mammal in the world. The only animals faster than pronghorns are African cheetahs. This makes sense since scientists feel pronghorns developed their speed outrunning American cheetahs thousands of years ago. Pronghorns can run close to 60 miles per hour, not as fast as cheetahs, but pronghorns can sprint for longer distances than cheetahs. The American cheetahs died out but the pronghorns survived. No modern-day predator comes close to the speed required to catch pronghorn.
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Their horns are also unique. Grazing animals usually carry either antlers or horns. The antlers of mule deer and elk are solid bone structures that branch into distinctive forks. Only males typically carry antlers and they shed these antlers each year. The horns of bighorn sheep and mountain goats are keratin structures forming simple hollow tubes. Both sexes typically carry these permanent horns. Then there are pronghorns. They carry horns with short, branching forks. Both sexes carry these horns that are shed each year.
Mature bucks display magnificent horns 13-15” long. The horn bases attach to the skull just above the eyes and slant forward at a debonair angle. Their sharp tips bend backward and curve inward until pointed at the animal’s back. The horn’s fork, or prong, protrudes forward three to four inches and ends in a dull point. Bucks may use this fork to catch and deflect other horns during mating duels. Only about 40 percent of does carry horns. They are usually short, without prongs, and some are misshapen.
The visible horns are actually sheaths that fall off after the fall rut. The shed sheaths look and feel like polished, matted hair. This leaves the animals with conical, bony horn cores barely 3-5” long. A buck’s skull looks slightly evil with these straight horn cores ending in sharp points. As soon as the old horn sheaths are lost, new ones begin growing and by early summer, the new sheath is full-grown.
Their black eyes are also unique. Their eyes are 1-1/2” across and among the largest in the animal kingdom. Pronghorn eyes are the same size as horse eyes and are nearly as large as elephant eyes.
They also make some of the longest migrations of any land mammal. During cold weather, pronghorns congregate in larger winter herds and will migrate to better winter range. In Elko County, they usually migrate less than 50 miles, although they do migrate from Wildhorse Reservoir to areas near Interstate-80, a distance of 65 miles.
In Wyoming, herds migrate 150 miles between the Upper Green River Basin and Grand Teton National Park. In North America, only caribou migrate farther.