Perception Channels: tactile ; chemical
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
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.
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.
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.
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
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.
Other Physical Features: endothermic ; bilateral symmetry
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.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual
The Sonoran Pronghorn (Antilocapra americana sonoriensis), the only existing modern species to the family Antilocapridae, is a mammal found in the Sonoran Desert of North America, ranging from southwestern Arizona to North of Mexico4. Though commonly referred to as an antelope, it is actually not an “antelope”, with the giraffe being its closest living relative1. It is the fastest known mammal to inhabit North America and has been nicknamed the “prairie ghost”3.
The Pronghorn is 3 foot tall at shoulder height and 4.3-4.8 foot from head to tail, and is a red brown deer look-alike5. It has light brown/tan to white spots on its undersides and neck; with males having black spots on its face and neck3. Typically, Pronghorn weigh an estimated 75 to 100 lbs with females being about 10% smaller in body size than males3. In addition, males have large black pronged horns in comparison to females which have short black horns3. The Pronghorn have a short tail that’s hardly noticeable.It is a shy and curious mammal with a speed of 60 mph, well-developed scent glands and keen eyesight to avoid predators1. It is also known to be elusive, detecting movement from several miles away, avoiding contact with humans as its habitat has been intruded2.
As its name implies, the Sonoran pronghorn thrives in the desert, hot arid climate areas, though drought has driven this species to become endangered. It is a herbivore, its diet consisting of cacti, herbs and desert grasses and is part of the ruminant family4. As a mammal inhabiting in the desert, the pronghorn can erect their bristle body hair in some parts of their body in order to release body heat4. The pronghornphysiology is known to be adapted to hot arid climate, however specifically how its physiology works has yet to be well studied.
The pronghorn have high reproductive rates, with does ready to mate at the age of 16 months and bucks at the age of 1 year3. Females leave herds in order to give birth, and gestation lasts for about 250 days, with females having an offspring of 1 fawn or twins during the times food is abundant4. Offspring are kept hidden and due to their negligible scent, they are far less detectable by predators4. Pronghorn have a lifespan of 10 to 12 years3.
The Pronghorn was listed as an endangered species in the later half of the 20th century, leading conservation groups towards creating programs aiming towards conserving and protecting this species. Though drought has become a major cause of its endangerment, habitat destruction has also led the Pronghorn to change its course of habitat range and migration4. With conservation efforts, it is estimated there is currently a total of 160 Pronghorn in the United States and 240 in Northern Mexico3.
The Sonoran pronghorn (Antilocapra americana sonoriensis) is an endangered subspecies of pronghorn that is endemic to the Sonoran Desert.[2]
Around 200 animals currently are believed to exist in Arizona in the United States, up from an estimated 21 individuals in 2002.[3] The number of individuals in Mexico is estimated to be even lower. It is considered extirpated from California.
In 2012, announcements of two reintroductions were published in the Federal Register. One of the reintroductions was to take place at the Barry M. Goldwater Air Force Range (BMGR) in Yuma, Arizona, and the second was to be at Kofa National Wildlife Refuge.[4]
Numerous and ongoing threats exist to the survival of the Sonoran pronghorn. Not the least of these threats is the fact that much of their habitat is occupied by the BMGR, which is an active United States Air Force bombing range.[5]
Adjacent to the BMGR is the Cabeza Prieta National Wildlife Refuge (CPNWR), also a critical breeding area for this species. Parts of the CPNWR are off limits to visitors between mid-March and mid-July, during the fawning season, so as to minimize disturbance to herds with fawns, which can result in the loss of fawns.[6] Despite this fact, this area too is subject to constant environmental pressure. The accompaniments of illegal trafficking of people and drugs from Mexico (such as the construction of illegal roads and trails, reckless disposal of trash, destruction of vegetation, and contamination of water sources) have significantly degraded the habitat. The response from law enforcement agencies (such as the U.S. Customs and Border Protection and the Drug Enforcement Administration) has also exacerbated this problem.[7][8]
Living in open areas, pronghorns in general must rely on their eyesight to avoid predators, and with population numbers so low, the Sonoran pronghorn must avoid mortality at all costs. Sources of mortality come from predators, drought, and lack of feed; these sources usually affect fawns most often, and adult mortality also occurs in drought situations. Controlling this situation is very difficult because drought is at the hand of the weather. Things that can be done are predator control on coyotes and bobcats, but this is yet to be studied with enough detail to be proven effective.[9]
The Sonoran pronghorn is endemic to the Sonoran Desert. They live in open spaces and primarily forage grasses and shrubs for food. Desert pronghorn are more adapted to desert conditions, and can go longer without water.
Sign along the El Camino Del Diablo at the eastern entrance to Cabeza Prieta National Wildlife Refuge, providing information about the animal The Sonoran pronghorn (Antilocapra americana sonoriensis) is an endangered subspecies of pronghorn that is endemic to the Sonoran Desert.
