Sonoran Pronghorn

Antilocapra americana sonoriensis

Description

The Sonoran pronghorn is a desert sub-species of the much more widely distributed pronghorn antelope. It has dark brown hair on its back and sides, and is lighter-colored on the belly, throat, and rump. The male has black cheek patches, black 12-inch (30-cm) horns that are shed each year, and can weigh 100-130 pounds (45-59 kg). The female weighs 75-100 pounds (34-45 kg), and may develop horns as long as her ears. The Sonoran pronghorn has long, slender, strong legs and feet that lack dewclaws. The eyes are large, protrude somewhat from the sides of the head, and provide wide-angle vision for spotting predators.

Behavior

The Sonoran pronghorn is an extremely fast runner, and can reach a speed of about 60 miles per hour (96 km/hr). Pronghorn antelopes are highly social, and are found in family groups or large wintering herds. They may wander over a large area to find forage when grazing is poor. They can erect patches of bristle-like body hair to expose the skin beneath, allowing an increased release of body heat during the hot summer. Erectile patches of white hair on the rump are also used to signal the possibility of approaching danger. Like other herding animals, sentinels stand guard while other animals are grasses, forbs (herbaceous dicotyledonous plants), shrubs, and cacti. They typically live for 9-10 years in the wild, and 12 years in captivity. They become sexually mature at about 16-17 months of age. The does usually gives birth to twin fawns in early June after a gestation period of about 250 days.

Habitat

The Sonoran pronghorn inhabits arid flatlands of semi-desert and desert regions.

Distribution

The Sonoran pronghorn is an endemic subspecies of the Sonoran Desert of southwestern Arizona and adjacent Mexico.

Threats

Initially, the most important threat to the Sonoran pronghorn was excessive hunting. More recently, however, the greatest threats have been habitat damage caused by overgrazing by domestic livestock, drought, the damming and diversion of rivers, road-killing, and perhaps harassment associated with military training exercises and aerial border patrols in the region. In Mexico, poaching is also a threat. In the 1990s, the surviving population was estimated to be only about 120-180 animals in Arizona, and 220 in Mexico.

Conservation and Recovery

Most of the habitat of the Sonoran pronghorn in Arizona is on federally owned land, primarily in the Barry M. Goldwater Range, Organ Pipe Cactus National Monument, and Cabeza Prieta National Wildlife Refuge. Although the ecological factors presently limiting this antelope are not well understood, they likely include a lack of available surface water for drinking, mortality caused by coyotes, habitat loss and fragmentation, and poaching in the Mexican range. Conservation of this rare antelope requires that it be strictly protected from hunting throughout its range, measures to reduce mortality from vehicular collisions, and habitat improvement through the provision of drinking water and other management benefits. In 1998, the Defenders of Wildlife sued the Federal Government for multiple violations of the Endangered Species Act based on an alleged failure to protect the endangered Sonoran pronghorn in southwestern Arizona.

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
P.O. Box 1306
Albuquerque, New Mexico 87103-1306
Telephone: (505) 248-6911
Fax: (505) 248-6915
http://southwest.fws.gov/

References

Defenders of Wildlife. 2000. "Sonoran Pronghorn (Antilocapra americana sonoriensis )." Defenders of Wildlife. (http://www.defenders.org/spha.html). Date Accessed: July 6, 2000.

New Mexico Department of Game & Fish. 2000.Sonoran Pronghorn. http://www.fw.vt.edu/fishex/nmex_main/species/050584.html