The pronghorn (, ) ( Antilocapra americana) is a species of artiodactyl (even-toed, hoofed) mammal indigenous to interior western and central North America. Though not an antelope, it is known colloquially in North America as the American antelope, prong buck, pronghorn antelope, and prairie antelope, because it closely resembles the antelopes of the Old World and fills a similar ecological niche due to parallel evolution.Farb, Peter (1970). Ecology. Time Life Books. pp. 126, 136 It is the only surviving member of the family Antilocapridae.
During the Pleistocene epoch, about 11 other antilocaprid species existed in North America, many with long or spectacularly twisted horns.Smithsonian Institution. North American Mammals: Pronghorn Antilocapra americana Three other genera ( Capromeryx, Stockoceros and Tetrameryx) existed when humans entered North America but are now extinct.
The pronghorn's closest living relatives are the giraffe and okapi. See Fig. S10 in Supplementary Information. The antilocaprids are part of the infraorder Pecora, making them distant relatives of deer, Bovidae, and Moschidae.
The pronghorn is the fastest land mammal in the Americas, with running speeds of up to . It is the symbol of the American Society of Mammalogists.
The pronghorn was first officially described by American ornithologist George Ord in 1815.
Each horn of the pronghorn is composed of a slender, laterally flattened blade of bone, which is thought to grow from the frontal bones of the skull, or from the subcutaneous tissues of the scalp, forming a permanent core. As in the Giraffidae, skin covers the bony cores, but in the pronghorn, it develops into a sheath which is Moulting and regrown annually. Males have a horn sheath about (average ) long with a prong. Females have smaller horns that range from (average ) and sometimes barely visible; they are straight and very rarely pronged.
Males are further differentiated from females in having a small patch of black hair at the angle of the mandible. Pronghorns have a distinct, odor. Males mark territory with a Preorbital gland on the sides of the head.
Male and female animals have glands that are exposed when the white hair on the rump stands up. 2-Pyrrolidinone, the major compound in the rump gland, has an odor reminiscent of buttered popcorn to humans. The flared rump hair and odor alert adjacent animals of a possible danger.
Pronghorns have well developed glands on each hoof. Like many ungulates, these interdigital (hoof) glands contain chemical compounds that are known to have antimicrobial activity against soil and mammalian pathogens.
Male pronghorns tend to have a higher level of physical activity than females, and apparently also have a greater blood volume relative to body size.
Pronghorns are built for speed, not for jumping. Since their ranges are sometimes affected by sheep ranchers' fences, they can be seen going under fences, sometimes at high speed. For this reason, the Arizona Antelope Foundation and others are in the process of removing the bottom barbed wire from the fences, and/or installing a barbless bottom wire.
The pronghorn has been observed to have at least 13 distinct , including one reaching nearly per stride.
When a pronghorn sees something that alarms it, the white hair on the rump flairs open and exposes two highly odoriferous glands that releases a compound described as having an odour "reminiscent of buttered popcorn." This sends a message to other pronghorns by both sight and smell about a present danger. This scent has been observed by humans 20 to 30 meters downwind from alarmed animals. The major odour compound identified from this gland is 2-pyrrolidinone.
The present-day range of the pronghorn is west of the Mississippi, extending from southern Saskatchewan and Alberta, Canada south into the western United States, primarily in the states of Arizona, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Texas, Utah, Washington and Wyoming, and into Mexico. In extreme Northern California, pronghorn can be found in inland counties, ranging from neighboring Nevada and Oregon, as well as the central coastal grasslands, further south. In Mexico, the Sonoran pronghorn ( A. a. sonoriensis) subspecies may be found from the state of Baja California Sur east through Sonora to San Luis Potosí, in north-central regions of the country, albeit in gradually diminishing populations. They have been extirpated from Iowa and Minnesota in the United States, and from Manitoba in Canada.
Other regional subspecies include the Rocky Mountain pronghorn ( A. a. americana), Mexican pronghorn ( A. a. mexicana), the Oregon pronghorn ( A. a. oregona), and the critically endangered Baja California pronghorn ( A. a. peninsularis).
Pronghorns prefer open terrain at elevations between , with the densest populations in areas receiving around of rainfall per year. They eat a wide variety of plant foods, often including plants unpalatable or toxic to domestic livestock, though they also compete with them for food. In one study, comprised 62% of their diet, 23%, and Poaceae 15%. Another study similarly found forbs comprised 20%,cactus 40%, shrubs 18%, and grass 22%. Pronghorns chew cud (ruminate).
Healthy pronghorn populations tend to stay within of a water source. The majority are found within of a water source.
An ongoing study by the Lava Lake Institute for Science and Conservation and the Wildlife Conservation Society shows an overland migration route that covers more than . The migrating pronghorn start travel from the foothills of the Pioneer Mountains through Craters of the Moon National Monument to the Continental Divide. Dr. Scott Bergen of the Wildlife Conservation Society says "This study shows that pronghorn are the true marathoners of the American West. With these new findings, we can confirm that Idaho supports a major overland mammal migration - an increasingly rare phenomenon in the U.S. and worldwide."
( Puma concolor), Gray wolf ( Canis lupus), ( Canis latrans), ( Ursus arctos horribilis) and ( Lynx rufus) are major predators of pronghorns. ( Aquila chrysaetos) have been reported to prey on fawns and adults. ( Panthera onca) also likely prey on pronghorns in their native range in the southwestern United States and in northern Mexico. In the Pleistocene, jaguars would likely be dangerous to pronghorns as a short-range ambush predator.
Adult males either defend a fixed territory that females may enter, or defend a harem of females. A pronghorn may change mating strategies depending on environmental or demographic conditions. Where precipitation is high, adult males tend to be territorial and maintain their territories with scent marking, vocalizing, and challenging intruders."Pronghorn" in The Encyclopedia of Mammals David MacDonald (ed.) Oxford University Press pp. 528–529 . In these systems, territorial males have access to better resources than bachelor males. Females also employ different mating strategies. "Sampling" females visit several males and remain with each for a short time before switching to the next male at an increasing rate as Estrous cycle approaches. "Inciting" females behave as samplers until estrous, and then incite conflicts between males, watching and then mating with the winners. Before fighting, males try to intimidate each other. If intimidation fails, they lock horns and try to injure each other. "Quiet" females remain with a single male in an isolated area throughout estrous. Females continue this mating behavior for two to three weeks.
When courting an estrous female, a male pronghorn approaches her while softly vocalizingBromley, Peter T., and David W. Kitchen. " Courtship in the pronghorn (Antilocapra americana)." The behaviour of ungulates and its relationship to management (GEIST, V. & WALTHER, F., eds) (1974): 356–364. and waving his head side to side, displaying his cheek patches. The on the pronghorn are on either side of the jaw, between the hooves, and on the rump. A receptive female remains motionless, sniffs his scent gland, and then allows the male to mount her.
Pronghorns have a gestation period of 7–8 months, which is longer than is typical for North American ungulates. They breed in mid-September, and the doe carries her fawn until late May. The gestation period is around six weeks longer than that of the white-tailed deer. Females usually bear within a few days of each other. Twin fawns are common. Newborn pronghorns weigh , most commonly . In their first 21–26 days, fawns spend time hiding in vegetation. Fawns interact with their mothers for 20–25 minutes a day; this continues even when the fawn joins a nursery. The females nurse, groom, and lead their young to food and water, as well as keep predators away from them. Females usually nurse the young about three times a day. Males are Weaning 2–3 weeks earlier than females. Sexual maturity is reached at 15 to 16 months, though males rarely breed until three years old. Their Life expectancy is typically up to 10 years, rarely 15 years.
Merriwether Lewis and William Clark made several other observations on the behavior of the pronghorn and how the local tribes hunted them. They described the animal, which they referred to as the "Antelope" or the "Goat", as follows:
In 1927, Grinnell spearheaded efforts along with the help of T. Gilbert Pearson of Grinnell's National Audubon Society to create the Charles Alexander Sheldon Antelope Refuge in northern Nevada. About 2900 acres of land were jointly purchased by the two organizations and subsequently turned over to the Biological Survey as a pronghorn refuge. This donation was contingent upon the government's adding 30,000 acres of surrounding public lands. On June 20, 1929, United States Herbert Hoover included the required public lands upon request of the Department of Agriculture and the Department of the Interior after learning that the Boone and Crockett Club and the National Audubon Society were underwriting the private land buyout. On January 26, 1931, Hoover signed the executive order for the refuge. On December 31, 1936, President Franklin Roosevelt signed an executive order creating a tract; this was the true beginning for pronghorn recovery in North America.
The protection of habitat and hunting restrictions have allowed pronghorn numbers to recover to an estimated population between 500,000 and 1,000,000 since the 1930s. Some recent decline has occurred in a few localized populations, due to bluetongue disease which is spread from sheep, but the overall trend has been positive.
Pronghorn migration corridors are threatened by habitat fragmentation and the blocking of traditional routes. In a migration study conducted by Lava Lake Institute for Science and Conservation and the Wildlife Conservation Society, at one point, the migration corridor bottlenecks to an area only 200 yards wide. New Long Distance Migration Route for Pronghorn Found in Idaho by WCS and Lava Lake Institute , November 2, 2009
Pronghorns are now quite numerous, and outnumbered people in Wyoming and parts of northern Colorado until just recently. They are legally hunted in western states for purposes of population control and food. No major range-wide threats exist, although localized declines are taking place, particularly to the Sonoran pronghorn, mainly as a result of livestock grazing, the construction of roads, fences, and other barriers that prevent access to historical habitat, illegal hunting, insufficient forage and water, and lack of recruitment.
Three subspecies are considered endangered in all ( A. a. sonoriensis, A. a. peninsularis), or part of their ranges ( A. a. mexicana). The Sonoran pronghorn has an estimated population of fewer than 300 in the United States and 200–500 in Mexico, while there are approximately 200 Peninsula pronghorn in Baja California. Populations of the Sonoran pronghorn in Arizona and Mexico are protected under the Endangered Species Act (since 1967), and a recovery plan for this subspecies has been prepared by U.S. Fish and Wildlife Service. Mexican animals are listed on CITES Appendix I. Pronghorns have game-animal status in all of the western states of the United States, and permits are required to Trapping or hunt pronghorns.
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