Is a Pronghorn an Antelope? Its Unique Family Explained

What is a pronghorn, then?

The pronghorn (Antilocapra americana) is an even-toed hoofed mammal of the order Artiodactyla, like deer, cattle, antelopes and giraffes. It is a ruminant that chews the cud. Within that group, it is the sole survivor of the family Antilocapridae, a branch that evolved in North America and has never lived anywhere else.

Its scientific name, Antilocapra, means “antelope-goat,” which shows how early naturalists struggled to place it. Lewis and Clark called it a “goat” when they met it in 1804, and the first scientific description, by George Ord in 1815, gave it its own genus.

How are pronghorn horns different from antelope horns?

Horns are the clearest difference. True antelopes, such as gazelles, impalas and wildebeest, have horns with a bony core covered by a sheath of keratin, the same material as fingernails. The sheath is never shed and grows throughout life, and it is never branched.

The pronghorn’s horns are built differently in two ways:

• They are branched. A male’s horn sheath has a forward-pointing prong partway up, which gives the animal its name. No bovid has branched horns.
• The sheath is shed every year. Between about late October and December, after the breeding season, males cast off their black outer sheaths. The bony core stays on the skull, already covered by a new sheath that grows to full size by the next summer.

Pronghorns also lack dewclaws, the small extra toes on the back of the leg that most deer and bovids have, and they have a gallbladder, which deer lack.

Where do true antelopes live?

“Antelope” is not one scientific group but an everyday name for many members of the cattle family, Bovidae, that are not cattle, sheep or goats. There are around 90 species, from the tiny royal antelope of West Africa, which weighs only a few kilograms, to the common eland, which can top 900 kg (2,000 lb).

Almost all of them live in Africa, with a smaller number in Asia, such as the blackbuck of India, the saiga of the Central Asian steppes and the gazelles of the Middle East. None is native to the Americas. So whatever the pronghorn is, its home continent alone sets it apart from every true antelope.

Why do people call it an antelope?

The pronghorn fills the same role on the North American plains that antelopes and gazelles fill in Africa and Asia: a fast, alert grazer and browser of open country, living in herds and relying on sharp eyes and speed to escape predators. Similar lifestyles shaped similar bodies, a process called convergent evolution.

When European settlers spread west, “antelope” was the most natural name, and it stuck in place names such as Antelope Island in Utah and Antelope Valley in California. In everyday American English, “antelope” usually means the pronghorn, but biologists use the name pronghorn to avoid confusion.

What are the pronghorn’s closest relatives?

Most genetic and anatomical studies place the pronghorn’s family among the Pecora, the group of ruminants with headgear that also includes giraffes, deer, bovids and musk deer. Exactly how the branches fit together has been debated, but several studies point to the giraffe family as the closest living relatives, making the okapi and the giraffe the pronghorn’s nearest kin. Whichever arrangement is right, true antelopes are more distant relatives.

The family was once much larger. During the past 20 million years, a dozen or more antilocaprid species lived in North America, many with striking horns. Some had four horns, others had spiraled or very long ones. Several genera were still alive when people first arrived in North America, but only Antilocapra americana survived the extinctions at the end of the last Ice Age.

Other animals that are not what their name says

The pronghorn is not alone in carrying a confusing name. The wildebeest, by contrast, really is an antelope despite its cow-like look, as explained in Is a wildebeest an antelope? The American “buffalo” is a bison, and the “mountain goat” of the Rockies is not a true goat but a goat-antelope.

Names like these usually come from early travelers comparing new animals with ones they already knew. For the pronghorn, the comparison is understandable, but its unique horns, long North American history and endurance speed, covered in How fast is a pronghorn?, make it an animal in a class of its own.