PRONGHORN: Antilocapridae

PHYSICAL CHARACTERISTICS

Pronghorn measure 52.1 to 58.8 inches (132.3 to 149.4 centimeters) long and have a shoulder height of 32.7 to 37 inches (83.1 to 94 centimeters). They weigh 87 to 129 pounds (40 to 59 kilograms). These long-legged runners have stocky bodies, and their coat is various shades of brown on top, with sides and underparts creamy white. Males have brownish black patches from below the ears and downward 3 to 4 inches (7.6 to 10.2 centimeters). Pronghorn have a short mane on the back of the neck, and their tails are short (4 inches, or 10.2 centimeters). The rump is covered by two patches of white hair. This animal is able to regulate the amount of insulation provided by its coat by erecting or flattening its hairs.

Both sexes have horns covered in keratin (KARE-ah-tin; protective material that makes up hair and fingernails). There are two branches, or prongs, one curving forward and another, shorter one pointing directly back. Males shed their horns every year; females shed them irregularly. Pronghorn have superb vision. Researchers believe that the placement of their eyes high on top of their skulls allows for them to keep a watch for predators while continuing to feed on lower-elevated grounds.

GEOGRAPHIC RANGE

Found in western North America.

HABITAT

Pronghorn can be found in abundant numbers in short-grass prairies where shrubs are readily available even with snow cover. Steppes (vegetation zones characterized by shrubs, grasses, and few trees) are also popular habitats, and deserts are home to less than 1 percent of the population.

Pronghorn are usually found on treeless, flat terrain between altitudes of 3,000 to 8,000 feet (914 to 2,438 meters).

PRONGHORN IN COLORADO

According to NationalGeographic.com, one of the earliest mentions of the pronghorn is in the expedition diaries of explorers Meriwether Lewis and William Clark. As often happens today, they compared the pronghorn to goats, antelopes, and gazelles.

The pronghorn population has taken a rollercoaster ride in terms of numbers. From an estimated thirty to sixty million in the early 1800s, they declined to less than 15,000 by 1915. As of 2004, there are an estimated one million on the plains of North America.

According to Colorado Division of Wildlife biologist Mark Vieira, the number of pronghorn in that state fell to around 2,000 at the end of the twentieth century but has grown to a steady 55,000 as of 2004. He explained to Rocky Mountain News reporter Gary Gerhardt that pronghorn thrive in this region because they don't compete with cattle. The two animals eat different plants, so all have enough to eat.

Winter months have proven particularly harsh for the Colorado pronghorn population on the Pawnee National Grasslands, however. During the winter, the animals create herds of about 100 individuals. Because Colorado has suffered serious drought in the twenty-first century, there isn't enough food to go around. Vieira reported, "Our usual fawn production was fifty to sixty fawns per one hundred does. Now it's fallen to eighteen per one hundred." In addition to starvation, the lack of vegetation is prohibiting pronghorn from manufacturing antibodies necessary for warding off disease.

"We are really desperate for moisture now. If we could get two good years, we could bring the population back," Viera said. Most pronghorn live in Montana and Wyoming.

DIET

Pronghorn prefer succulent (water-based) forbs (drought-resistant herbs with broader leaves than grasses) over other food. During droughts and snowy months, pronghorn rely on shrubs to supplement their diet. They walk while they eat and seem to find food using smell as well as sight. They use their muscled

lips to grab hold of plants and vegetation, bring it to their mouths, then rip the plant apart with their teeth. Pronghorn will drink water if available, but pronghorn get most of their water from succulents, plants that contain a lot of water.

BEHAVIOR AND REPRODUCTION

Pronghorn are among the fastest land animals, able to reach speeds of 53.7 miles per hour (86.5 kilometers per hour) and maintain that pace for several miles (kilometers) before exhaustion sets in. They run with their mouths open to increase oxygen intake. Pronghorn are also strong swimmers.

Pronghorn are vocal animals, and make snorting and "sneezing" sounds when sensing something unfamiliar in their habitat. Fawns make soft bleating sounds (similar to lambs) that help parents locate hidden offspring. Adult females grunt or click when approaching hidden fawns or when being pursued by bucks. Bucks roar when chasing does or other bucks. During courtship, bucks smack their lips and flick their tongues, both of which create a low sucking sound.

Pronghorn live in herds, sometimes loosely scattered, but always highly organized. When threatened, they'll raise their white rump hairs and snort, alerting other herd members to gather together more closely. They are active during daylight and nighttime, with peak activity occurring just after sunrise and before sunset. They spend most of their time feeding or sleeping, the latter of which they do in short spurts and frequently throughout the day.

Home ranges vary greatly and are dependent on quality of habitat, group size, season, and history of land use. Winter and summer ranges may be as far apart as 100 miles (160 kilometers). Bucks will mark their territory with urine and feces.

Pronghorn are polygynous (puh-LIH-juh-nus; one male has several female mates), and mating occurs between July and early October. Pregnancy lasts eight and a half months; a single fawn is born in the spring if this is the doe's first birth. Successive births usually result in twins, rarely triplets. By day four, fawns are able to outrun humans. Fawns nurse (drink mother's milk) until around four weeks of age, at which time they join their mothers on feeding trips.

Pronghorn are sexually mature at sixteen to seventeen months. Primary predators, animals that hunt them for food, include coyotes, wolves, and bobcats. Lifespan is seven to ten years.

PRONGHORN AND PEOPLE

Pronghorn have a long history with Native Americans. Many Indian myths involved this animal, and it was considered the personification of peace, good fortune, and speed. Pronghorn often appeared on prehistoric pottery and walls.

Late in the nineteenth century, pronghorn were slaughtered for their skins. Canada and the United States opened hunting seasons in the mid-1900s, and by the end of 2002, almost five million pronghorn had been legally harvested. This hunting season provides tons of meat and millions of dollars in profit for businesses located in pronghorn country.

Pronghorn are known to damage crops, sometimes extensively.

CONSERVATION STATUS

Pronghorn are not threatened.

FOR MORE INFORMATION

Books:

Byers, John A. Built for Speed: A Year in the Life of Pronghorn. Cambridge, MA: Harvard University Press, 2003.

Frisch, Aaron. Pronghorn Antelope. North Mankato, MN: Smart Apple Media, 2002.

Nowak, Ronald M. "Pronghorn." Walker's Mammals of the World Online 5.1. Baltimore: Johns Hopkins University Press, 1997. http://www.press.jhu.edu/books/walkers_mammals_of_the_world/artiodactyla/artiodactyla.antilocapridae.antilocapra.html (accessed on July 8, 2004).

O'Gara, Bart, Jim D. Yoakum, and Richard E. McCabe. Pronghorn: Ecology and Management. Boulder, CO: University Press of Colorado, 2004.

Periodicals:

Gerhardt, Gary. "Unique Pronghorn are a Sight to Behold; Speedy Animals Often Overlooked in Wildlife." Rocky Mountain News (May 1, 2004).

Tabor, Thomas C. "The Pronghorn: Back from the Edge of Oblivion." Countryside & Small Stock Journal (May 1, 2004).

Web sites:

"The Pronghorn." Desert USA. http://www.desertusa.com/mag99/may/papr/pronghorn.html (accessed on July 8, 2004).

"Pronghorn." Great Plains Nature Center. http://www.gpnc.org/pronghor.htm (accessed on July 8, 2004).