Pronghorn

The pronghorn (Antilocapra americana) is a unique mammal native to the interior western and central regions of North America.

While many people call it the "American antelope," it is not actually an antelope. It is the only surviving member of its own biological family, Antilocapridae. During the Pleistocene epoch, about 11 other species in this family lived in North America. Many of those extinct relatives had long or very twisted horns. The pronghorn's closest living relatives are the giraffe and the okapi. It belongs to the infraorder Pecora, which makes it a distant relative of deer and bovids.

One of the most remarkable things about the pronghorn is its specialized anatomy for running. It is the fastest land mammal in the Western Hemisphere. It can reach speeds of up to 55 miles per hour. While the African cheetah is faster in short bursts, the pronghorn can sustain high speeds for much longer.

This ability likely evolved to help it escape extinct predators like the American cheetah. To support this extreme movement, the pronghorn has a very large windpipe and heart. It also possesses high blood volume and many erythrocytes, which are red blood cells. These features allow the animal to take in massive amounts of oxygen while sprinting. Its light bone structure and hollow hair also reduce weight to aid speed.

The pronghorn's horns are distinct from the horns found in the ox family, Bovidae. Each horn consists of a permanent, slender bone core. A keratinous sheath, which is the same material as fingernails, grows over this bony core. Unlike the bone, this sheath is shed and regrown every year. Adult males typically have horns about 13 inches long with a forward-pointing branch called a tine. Females have much smaller horns that range from 2 to 6 inches. These female horns are usually straight and rarely have a prong. Males can also be identified by a small patch of black hair near the jaw.

European explorers first saw pronghorns in the 16th century. However, the species was not formally scrutinized until the expedition of Captain Meriwether Lewis and William Clark from 1804 to 1806. They encountered the animals near the mouth of the Niobrara River in present-day Nebraska. Following this, the ornithologist George Ord officially described the species in 1815. These early encounters helped scientists begin to categorize the unique biology of the pronghorn.

Pronghorns use a sophisticated chemical alarm system to warn others of danger. When a pronghorn is alarmed, the white hair on its rump flares open. This action exposes specialized scent glands that release a compound called 2-pyrrolidinone. This chemical has a distinct odor that humans describe as being like buttered popcorn.

This scent can be detected by humans between 65 and 100 feet downwind. This serves as both a visual and a chemical signal to the rest of the herd. Additionally, they have interdigital glands on their hooves that contain compounds with antimicrobial activity to fight pathogens in the soil.

The current range of the pronghorn extends from southern Canada through the western United States and into Mexico. They prefer open terrain at elevations between 3,000 and 7,000 feet. They are highly dependent on water, with most populations staying within 15 miles of a water source. Their diet is varied, consisting of forbs, shrubs, cacti, and grasses. In one study, forbs made up 62% of their diet, while shrubs accounted for 23%. They are also ruminants, meaning they chew cud to digest their food.

Socially, pronghorns change their behavior based on the season. In the winter, they form mixed-sex herds. In the spring, these groups break into bachelor groups of males and harems of females.

Females may use different mating strategies, such as "sampling" multiple males or "inciting" conflicts between them. Males may defend a specific territory or a group of females. This complex social structure helps ensure the survival of the species across the vast American prairies.