The Sonoran Pronghorn is found in the nearctic region, with a concentration of populations in southwestern Arizona, and some spread into northern Mexico. Although the species Antilocapra americana ranges from southern Canada to northern Mexico, the A. a. sonoriensis subspecies has a very limited range.

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (250-20,000 square km (about 100-8000 square miles)) Formerly throughout southern Arizona and in Mexico south to Guaymas, Sonora; presently in Yuma, Pima, and Maricopa counties, south of the Bill Williams River and west of the Baboquivari Mountains, southwestern Arizona, and in northwestern Sonora (Matthews and Moseley 1990, Hoffmeister 1986). See Hoffmeister (1986) for specific records of occurrence in Arizona.

Historic Range:

U.S.A. (AZ), Mexico

Height: ~0.9 m at the shoulder  The Sonoran Pronghorn has the characteristic artiodactyl body form. This subspecies has a particularly light build, which contributes to its fast speed; Pronghorns are the fastest North American mammals. Females are roughly 10% smaller than males. All pronghorns have a very short, hardly noticeable tail, ears that are proportional in size to the body and with narrow points, no upper canines, and well-developed scent glands. Both males and females have horns that are specialized with a layer of hornskin covering the bony core. The horns are branched at about 2/3 of the distance between the base and the tip. However, bucks' horns are 30.5 centimeters in length, whereas does' horns are shorter than the ears and often misshapen or even absent altogether. The upperparts of the Pronghorn are a warm tan color, and the neck has a short black mane. The underparts, rump, and 2 bands across the neck are white. Less information is available about Sonoran Pronghorns than about other Antilocapra americana subspecies. However, given that A.a.sonoriensis lives in a very arid climate, it is likely that its physiology is somewhat more adapted to extreme conditions. It must endure higher temperatures, exposure to intense solar radiation, and scarcity of water and food resources. All these conditions call for more thermoregulation and a balance in hydration.

Differs from other subspecies in smaller size, narrower skull width and rostrum, unpronounced frontal depression, and relatively small auditory bullae (see data in Hoffmeister 1986); however, the reported differences are based on small sample sizes and need to be confirmed when and if more specimens become available (Hoffmeister 1986).

Type for Antilocapra americana sonoriensis Goldman, 1945
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Female;
Preparation: Skin; Skull
Collector(s): V. Bailey & F. Winthrop
Year Collected: 1932
Locality: Costa Rica Ranch, 40 Mi N, On Rio De Sonora, SW Of Hermosillo, Sonora, Mexico, North America

The Sonoran Pronghorn inhabits dry plains and desert. In southwestern Arizona, this species is found in broad alluvial valleys separated by granite mountains and mesas. These areas experience excessive winter rains followed by a spring drought, and summer rains followed by autumn drought. The dry, sparsely vegetated landscape is due to the arid climate of this region.

Terrestrial Biomes: desert or dune ; savanna or grassland

Comments: Broad alluvial valleys separated by granite mountains and mesas; areas with small-leaf trees (foothill paloverde, mesquite, catclaw, crucifixion thorn, smoketree) and numerous species of cacti (saguaro, barrel cactus, etc.) scattered over rocky hills and coarse-soiled slopes; triangle-leaf bursage or brittle bush almost always present (Matthews and Moseley 1990). Habitat in southwestern Arizona: vegetation includes big galleta grass, six week three-awn, six weeks grama, creosote bush, bursage, and saltbush, similar to habitat in Sonora, where pronghorns occupy areas of stable sand dunes that have meadowlike conditions within or adjacent to them (Hoffmeister 1986). In the U.S., occurs in creosote bush-bursage habitat throughout the year, and utilizes areas containing palo verde-mixed cacti plant associations in spring and summer (Federal Register, 7 September 1994, p. 46266). Availability of free water reportedly is a critical factor (Hoffmeister 1986), but this has not been verified (Federal Register, 7 September 1994). A study of habitat utilization in southwestern Arizona recently was completed by Keith Hughes, University of Arizona (USFWS 1990).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

This species is strictly herbivorous, eating a diet of herbs, cacti, and some desert grasses. Cheek teeth with high crowns are an adaptation to dust-covered, abrasive foods. The Sonoran Pronghorn is a member of the ruminant family, which is characterized by a four-part stomach. This specialized stomach serves as a "fermentation vat": after eating, individuals regurgitate softened cud, which is then chewed again, reswallowed, and finally digested. This digestion system is key in this desert subspecies for a number of reasons. It facilitates the digestion of roughly textured foods such as cacti and desert grasses. It also allows for a high and long retention of both food and water, which is essential in an environment characterized by resource scarcity. Lastly, the stomach lining of ruminant stomachs is highly tolerant of urea, which exists in high concentrations in desert organisms due to highly concentrated urine.

Comments: Eats various grasses and forbs, browses on shrubs.

1 - 1000 individuals

Comments: Population in Arizona was probably 50-150 in the late 1980s; probably less than 350 in Mexico (Matthews and Moseley 1990).

Comments: Daily activity pattern varies seasonally. Alternating periods of feeding and rest occur throughout the day, with fairly continuous feeding in the early morning and late afternoon, and longer rest periods at night (Davis 1974).

Pronghorns have high reproductive rates. This is an adaptation for a short life span of 7 to 10 years, although individuals rarely exceed 9 years. The complex and rigid territoriality systems of bucks break down only during the breeding season. Dominant males court estrus females by offering a sniff of the scent glands located under patches of black hair below the ears. When it comes time to mate, dominant males disappear into hiding places with the estrus females. The male may circle the female with exaggerated steps, alternately flashing the black patches on his right and left cheeks. During this time, younger males move into the herds of non-breeding females.  The gestation period for Pronghorns is 250 days. Females often leave their herd to give birth, and will give birth to 1 to 2 young, each of which weighs between 2.25 kg and 3 kg. The young lay hidden; if twins are born, they are kept separately. Young are further protected from predators by their negligible scent; this makes them virtually undetectable in their hiding places. Young Pronghorns are weaned at 4 to 5 months, and reach adult size at 6 months. Sexual maturity occurs at 2 years. At the conclusion of the breeding season, termed the "rut," males shed their horn sheaths and look very similar to females. As they rejoin the female herd, the camouflage of blending in compensates for their post-breeding exhaustion and vulnerability.

Breeds in summer and early fall (around late July to early October), probably mainly in late summer. Gestation probably lasts around 210-225 days. Births occur in mid-spring. Females give birth usually to twins (single fawns mainly from young females). Young are weaned by four months, but continue to follow mother during first winter. Some begin breeding at 1 year.

The Sonoran subspecies of pronghorn antelope was listed as endangered on June 2, 1970. Primary threats are habitat destruction due to overgrazing and damming and diversion of rivers. Pronghorn antelope are an endemic American species, whose numbers were severely threatened with the arrival of European settlers. Within 100 years, populations fell from several million to 19,000 animals. Pronghorn antelope are easy prey due to their curiosity. In the winter of 1868-1869, antelope (most likely from the subspecies A. a. americana, found throughout the northern great plains) were transported to various cities by the wagon load between Denver and Cheyenne; 3 to 4 pronghorn were sold as food at prices as low as $.25 (Grzimek 1990). Conservation efforts began at the beginning of the 20th century. When the sale of game meat was outlawed, numbers rose to about 600,000.

US Federal List: endangered

CITES: no special status

United States

Rounded National Status Rank: N1 - Critically Imperiled

Rounded Global Status Rank: T1 - Critically Imperiled

Reasons: Small, reduced range in Arizona and Sonora (Mexico); major threats include habitat loss due to human activities and (in Mexico) probably poaching.

Current Listing Status Summary

Status: Endangered
Date Listed: 03/11/1967
Lead Region:   Southwest Region (Region 2)   
Where Listed: Entire

Status: Experimental Population, Non-Essential
Date Listed: 05/05/2011
Lead Region:   Southwest Region (Region 2)   
Where Listed: Experimental Population Sonoran Pronghorn


Population detail:

Population location: U.S.A. (AZ), Mexico In Arizona, an area north of Interstate 8 and south of Interstate 10, bounded by the Colorado River on the west and Interstate 10 on the east; and an area south of Interstate 8, bounded by Highway 85 on the west, Interstates 10 and 19 on the east, and the U.S.- Mexico border on the south.
Listing status: EXPN

Population location: Entire, except where listed as an experimental population.
Listing status: E

For most current information and documents related to the conservation status and management of Antilocapra americana sonoriensis , see its USFWS Species Profile

Global Short Term Trend: Decline of 10-30%

Comments: USFWS (1990) categorized the status as "declining."

Comments: Low population size probably is due to loss of essential habitat though water diversions and dams, livestock grazing, and agriculture; in Mexico, poaching is one of the suspected causes of decline (Matthews and Moseley 1990).

Needs: A recovery plan is available (1982); draft revised recovery plan became available in 1994.

Pronghorns move into urban areas and browse on hedges and gardens.

Sonoran Pronghorns were an abundant and accessible food and trophy source for many years.

Comments: The distinctiveness of this subspecies remains to be ascertained (Hoffmeister 1986).