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The Pronghorn

Antilocapra americana

Pronghorn

Entirely unique on this planet, the Pronghorn's scientific name, Antilocapra americana, means "American antelope goat." But the deer-like Pronghorn is neither antelope nor goat -- it is the sole surviving member of an ancient family dating back 20 million years.

The Pronghorn is the only animal in the world with branched horns (not antlers) and the only animal in the world to shed its horns, as if they were antlers. The Pronghorn, like sheep and goats, has a gall bladder, and like giraffes, lacks dewclaws. If that weren't enough, the Pronghorn is the fastest animal in the western hemisphere, running in 20-foot bounds at up to 60 miles per hour. Unlike the Cheetah, speedburner of the African plains, the Pronghorn can run for hours at quite a fast pace.

Range

Throughout all 4 deserts of the American Southwest, from Saskatchewan, Canada south to Mexico.

Habitat

Grasslands, brushlands, bunch-grass and sagebrush areas of open plains and deserts.

Description

This North American hoofed mammal is the sole surviving member of the family Antilocapridae (order Artiodactyla). It is also called the Prongbuck, Pronghorned Antelope and American Antelope. It is not related to the Old World antelopes. The slender, graceful, Pronghorn has a deer-like body weighs between 90 and 125 pounds, and stands about 3 1/2 feet at the shoulder. It has large, protruding eyes and a white or buff, 4-inch tail.

The upper body and outside of the legs are tan to brown. The cheeks, lower jaw, chest, belly, inner legs and rump are usually white. The male has a broad, black band down the snout to a black nose and black neck patch, together with black horns.

Not an antler, the horn is a hollow sheath over a bony core arising from the skull directly over the eyes. Horns are lyre-shaped, with the female not exceeding 3 or 4 inches. Male horns may grow to 20 inches with a short prong jutting forward and upward halfway from the base. Unlike any other animal, however, the Pronghorn sheds its horn

Behavior

The Pronghorn inhabits open plains and semi-deserts, living alone or in small bands in summer and Pronghornforming large herds in winter. Being highly mobile, the Pronghorn may cover a large area during the year. Pronghorn can survive a temperature range of 180 degrees, from 130 in the deserts to 50 below zero.

This high-strung animal is active night and day, combining alternate snatches of sleep with vigilant feeding. Pronghorn are selective, opportunistic foragers. They feed on forbs, shrubs, grasses, juniper, chamiso and sometimes cacti and domestic crops. In winter, desert populations are said to favor Sagebrush.

Because Pronghorn inhabit open terrain, they rely on defense mechanisms of speed and keen eyesight,; Pronghorn can detect movement up to 4 miles away. When alerted to danger, they contract their rump muscles causing their white rump hairs to stand on end, which other Pronghorn may detect from 2 miles away. At the same time, they exude a musky odor, which can be detected for more than a mile.

Life Cycle

In late summer or early Fall, the male gathers a harem of about 3 or 4 does. Horns are shed a month after breeding. Pronghorns have been known to breed as fawns but they usually breed for the first time when they are 16 to 17 months old. The does usually produce twin fawns in early June after a gestation period of about 250 days.

The young are born in May or June weighing anywhere from 4 to 12 pounds, according to various sources; about 60% of the births being twins. At birth, fawns lack the spots that are characteristic of deer and elk fawns. The newborns do not have an odor and instinctively lie motionless for hours. This is their main defense from predators such as bobcats, eagles and coyotes.

The young are born in May or June, weighing anywhere from 4 to 12 pounds, according to various sources. Within a day or two, the 16-inch-tall fawn will be able to sprint at speeds up to 25 mph. But for the first few days after birth, the fawns lie quietly in tall grass while the mother grazes

After a week of nursing, the does and fawns rejoin the herd. The greatest losses occur during the first two months of life. Only about 40 percent of the fawns born in June live until mid-July. Pronghorn longevity is estimated at 9 to 10 years in the wild, and 12 years in captivity.

Current Status

Pronghorn cannot leap fences, like deer can do, so fenced rangeland has hampered their migration and survival in the past century. It is estimated that in the mid-1800s, Pronghorn numbered in the many million, second only to the American Bison. By the 1920s, the U.S. population had been reduced to about 20,000.

Since then, efforts to preserve the Pronghorn have helped revitalize the general population. Pronghorn are still a highly prized game animal, and limited hunting is permitted in some prairie states.

There are 5 Pronghorn subspecies:

  • Antilocapra americana anteflexa
  • A.a. oregona
  • A.a. mexicana
  • A.a. peninsularis
  • A.a. sonoriensis

mexicana, peninsularis, sonoriensis are endangered and protected.

The Sonoran Pronghorn is found exclusively in the Sonoran Desert of Arizona and Mexico. Its population has been reduced by habitat loss due to livestock overgrazing, drought and the damming and diversion of rivers. Strangely enough, it,s largest population is found on the Goldwater Bombing Range in Southern Arizona where it apparently does quite well. In Mexico, where it is also imperiled by habitat loss, poaching is still a threat. The Sonoran Pronghorn are protected by the Endangered Species Act. Current estimates place the U.S. population at 256 with another 220 in Mexico.

The Peninuslar Pronghorn is a protected sub-species living only in the Vizcaíno Desert of Baja, California Less than 150 individuals are suspected to exist in the wild. There are some in captivity, captive breeding is a part of the recovery plan.

American Pronghorn were native to the Arizona Strip and were reported as common by early residents. They were apparently eliminated from the Strip in the early 1900s. They were reintroduced to the area beginning in 1961 and continue today. At present, the Clayhole Pronghorn population is estimated at between 250 and 290 animals.

Pronghorns inhabit and can be seen (with a pair of good binoculars) in a number desert locations:

  • Cabeza Prieta Wildlife Refuge
  • Fort Peck Wildlife Refuge
  • Organ Pipe Cactus National Monument
  • Sheldon National Antelope Refuge
  • On the Arizona Strip, Pronghorn are found on 756,000 federally managed acres in the Clayhole, Mainstreet, Hurricane and House Rock areas.

 

Some of the best places to see Pronghorn are just south of Marfa, Texas and between Alpine and Fort Davis, Texas. There is a resident population that lives just south of Marfa and a more mobile population that can often be seen grazing alongside cattle on the plains north of Alpine on both sides of the road leading to Fort Davis.

-- A.R. Royo

 


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