American pronghorns

American Pronghorn Facts

Classification:

• Kingdom: Animalia
• Subkingdom: Bilateria
• Phylum: Chordata
• Subphylum: Vertebrata
• Class: Mammalia
• Order: Artiodactyla
• Family: Antilocapridae
• Subfamily: Antilocaprinae
• Genus and species:Antilocapra americana
• Geographical location: Throughout North America
• Habitat: Open grasslands in plains and semideserts
• Gestational period: Eight months
• Life span: Ten years in the wild, up to fourteen years in captivity
• Special anatomy: Back-curving, pronged bone horns over which a black horny covering grows; the covering is shed and renewed every year, and the core is retained

The pronghorn, or American antelope, can sprint sixty miles per hour and run at forty miles per hour. Pronghorns are fast almost from birth. For example, two-day-old pronghorns can outrun humans. Pronghorns are the only living members of the artiodactyl sub-family Antilocapridae, related to antelope. They are not true antelope and reportedly are almost unchanged from ancestors of two million years ago.

Pronghorns inhabit open grasslands in plains and semideserts and depend on keen eyesight to detect enemies (wolves and coyotes) and on speed to escape them. When pronghorns are afraid, their white rump hairs rise and are visible for miles. An endangered pronghorn also emits warning odors from rump scent glands. This gives other pronghorns time to seek safety.

Pronghorns are ruminant herbivores. In the summer they eat herbs, sagebrush, and grasses. During winter, pronghorns dig under the snow for hidden grass and woody plant twigs. When water is scarce, they get needed moisture by eating cacti. Pronghorns are sociable creatures, and their groupings reflect living conditions. In summer, males form single-sex groups, and females live with offspring. In winter, pronghorns form large herds containing both genders.

Physical Characteristics of Pronghorns

Pronghorns are graceful, tan to reddish-brown animals, with solid, chunky bodies, strong but slender legs, and short tails. Their bellies, rump patches, and throat bars are very white. Male pronghorns (bucks) grow to body lengths of 4.5 feet, shoulder heights of 3.5 feet, and weights of 155 pounds. Bucks have back-curving horns with prongs, which is the source of the species name. The horns are up to 1.5 feet long and made of a bone core over which a black horny covering grows. The covering is shed and renewed every year, and horn core is retained. Females have much smaller horns and also shed the coverings. Pronghorns are the only known animals that shed horn covers.

Pronghorns are artiodactyl herbivores (others include cattle, pigs, goats, deer, and antelope), which walk on two toes. Their ancestors had five toes, but evolution removed the first toe, and the second and fifth toes are vestigial. The support toes—the third and fourth toes—each end in a hoof. Many artiodactyls are ruminants that chew and swallow vegetation, which enters the stomach for partial digestion, is regurgitated, chewed again, and reenters the stomach for more digestion.

Bovids, including pronghorns, have true horns (called horns henceforth). They are permanent, hard, pointy skull outgrowths that usually occur only on heads of males. Horns of females, where present, are smaller. All have bone cores, and atop the core is a tough skin layer rich in keratin, a durable covering for underlying bone. In pronghorns, horn coverings are shed and regrown every year, allowing horns to enlarge.

The Life Cycle of Pronghorns

In the spring, pronghorn herds separate according to age and gender. Does live in small herds and bucks live in breeding territories that they mark with scent from glands under their ears. Each buck tries to attract mates and scare away rivals by bellows or charges. Sometimes very violent battles arise over territories.

In August and September, does begin to pass through individual male territories. Some stop and mate with a buck; others move to the next breeding territory. Gestation lasts eight months and usually produces twin offspring (fawns). Fawns weigh 7 to 8.5 pounds at birth. They develop quickly and are weaned in five months. Pronghorns live about ten years in the wild and up to fourteen years in captivity

When North America was settled by Europeans, over fifty million pronghorns lived on the continent. In the early twentieth century, it was estimated that their population was only twenty thousand to twenty-five thousand, due largely to indiscriminate hunting. At that time pronghorns were protected by severely limiting their hunting. This control and careful wildlife management have raised the pronghorn population to 500,000. Wyoming, Montana, and New Mexico permit limited hunting of pronghorns.

Principal Terms

buck: a male pronghorn

doe: a female pronghorn

fawn: a newborn pronghorn

gestation: pregnancy or its length

herbivore: an animal that eats only vegetation

keratin: a tough protein plentiful in hooves and outer coverings of horns

ruminant: a herbivore that chews and swallows food, which enters its stomach, is partly digested, is regurgitated and chewed again, and reenters the stomach for more digestion

Bibliography

Bubenik, George A., and Anthony B. Bubenik, eds. Horns, Pronghorns, and Antlers: Evolution, Morphology, Physiology, and Social Significance. New York: Springer, 1990. Print.

Caton, John Dean. The Antelope and Deer of America. 1877. Reprint. New York: Arno, 1979. Print.

O'Gara, Bart W. Pronghorn: Ecology and Management. Boulder: UP of Colorado, 2004. Print.

Spinage, Clive A. The Natural History of Antelopes. New York: Facts on File, 1986. Print.

Turbak, Gary. Pronghorn: Portrait of the American Antelope. Flagstaff: Northland, 1995. Print.

Yoacum, James D., and Donald E. Spalenger, eds. American Pronghorn Antelope: Articles Published in the Journal of Wildlife Management. Washington, DC: Wildlife Soc., 1979. Print.