Pronghorn

From Wikipedia, the free encyclopedia The pronghorn (Antilocapra americana) is a species of artiodactyl   mammal  endemic to interior western and central  North America. Though not an antelope, it is often known colloquially in North America as the prong buck, pronghorn antelope, or simply antelope,| [3]  as it closely resembles the true antelopes of the  Old World  and fills a similar ecological niche due to  convergent evolution .| [4]  It is the only surviving member of the  family   Antilocapridae .| [5]  During the  Pleistocene  period, 12  antilocaprid  species existed in North America.| [6]  About five existed when humans entered North America[ citation needed ] 13,000 years ago; all but A. americana are now  extinct .| [5] Adult males are 1.3–1.5 m (4 ft 3 in–4 ft 10 in) long from nose to tail, stand 81–104 cm (32–41 in) high at the shoulder, and weigh 36–70 kg (79–150 lb). The females are the same heights as males but weigh 41–50 kg (90–110 lb). The feet have just two hooves, with no  dewclaws. The body temperature is 38 °C (100 °F) .| [5] | [7]  | [8]  | [9] Closeup of headEach "horn" of the pronghorn is composed of a slender, laterally flattened blade of bone that grows from the frontal bones of the skull, forming a permanent core. As in the Giraffidae, skin covers the bony cores, but in the pronghorn it develops into a  keratinous  sheath which is shed and regrown on an annual basis. Unlike the horns of the family Bovidae, the horn sheaths of the pronghorn are branched, each sheath possessing a forward-pointing tine (hence the name pronghorn). The horns of males are well developed.

The orbits (eye sockets) are prominent and sit high on the skull; there is never an antorbital pit. The teeth are hypsodont, and the  dental formula  is: EnlargeMales have a prominent pair of horns  on the top of the head, which are made up of an outer sheath of hairlike substance that grows around a bony core; the outer sheath is shed annually. Males have a horn sheath about 12.5–43 cm (4.9–17 in) (average 25 cm (9.8 in)) long with a prong. Females have smaller horns, ranging from 2.5–15 cm (1–6 in) (average 12 centimetres (4.7 in)) and sometimes barely visible; they are straight and very rarely pronged.| [8] Males are further differentiated from females in that males will have a small patch of black hair at the angle of the mandible. Pronghorns have a distinct, musky odor. Males mark territory with a scent gland  located on the sides of the head.| [5]  They also have very large eyes, with a 320 degree field of vision. Unlike deer, pronghorns possess a  gallbladder .| [10]

It can run exceptionally fast, being built for maximum predator  evasion through running, and is generally accepted to be the fastest land mammal in the Western Hemisphere. The top speed is very hard to measure accurately and varies between individuals; it is variously cited as up to 70 (43),| [7], 86 (53)| [8]  , or 100 km/h (62 mph)| [11]  <sup class="reference" id="cite_ref-11">| [12]  .It is often cited as the second-fastest land animal, second only to the  cheetah .<sup class="reference" id="cite_ref-natgeojan07_12-0">| [13]  It can, however, sustain high speeds longer than cheetahs.<sup class="reference" id="cite_ref-hawes_5-1">| [6]   University of Idaho  zoologist  John Byers  has suggested that the pronghorn evolved its running ability to escape from  extinct  predators such as the  American cheetah , since its speed greatly exceeds that of  extant  North American predators.<sup class="reference" id="cite_ref-hawes_5-2">| [6]  <sup class="reference" id="cite_ref-13">| [14]  It has a very large heart and lungs, and hollow hair. Although built for speed, it is a very poor jumper. Their ranges are often affected by sheep ranchers' fences. However, 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 barb-less bottom wire.<sup class="Template-Fact" style="white-space: nowrap;">[ citation needed ]

The pronghorn has been observed to have at least 13 distinct gaits, including one reaching nearly 7.3 m (8 yards) per stride.<sup class="reference" id="cite_ref-hawes_5-3">| [6]

edit ] Range and ecology
EnlargePronghorns in Fort Rock, Oregon, United States.Pronghorns were brought to scientific notice by the  Lewis and Clark Expedition , which found them in what is now  South Dakota ,  USA. The range extends from southern Saskatchewan  and  Alberta  in  Canada  south through the  United States  (southwestern  Minnesota  and central  Texas  west to coastal southern  California <sup class="reference" id="cite_ref-14">| [15]  <sup class="reference" id="cite_ref-15">| [16]  and northern  Baja California Sur, to  Sonora  and  San Luis Potosí  in northern  Mexico .<sup class="reference" id="cite_ref-smithsonian_4-4">| [5]  <sup class="reference" id="cite_ref-16">| [17]

The subspecies known as the Sonoran pronghorn  (Antilocapra americana sonoriensis) occurs in  Arizona  and  Mexico .<sup class="reference" id="cite_ref-adw_7-3">| [8]  Other subspecies include the  Mexican pronghorn  (A. a. mexicana), the  Oregon pronghorn  (A. a. oregona), and the critically endangered  Baja California Pronghorn  (A. a. peninsularis). EnlargePronghorn herd, Yellowstone National Park Pronghorns live primarily in  grasslands  but also in brushland and  deserts. They eat a wide variety of plant foods, often including plants that are unpalatable or toxic to domestic livestock  ( sheep  and  cattle ) though they also compete with these for food.<sup class="reference" id="cite_ref-texas_6-2">| [7]  In one study  forbs  comprised 62% of the diet,  shrubs  23%, and  grasses  15%,<sup class="reference" id="cite_ref-texas_6-3">| [7]  while in another,  cacti  comprised 40%, grass 22%, forbs 20%, and shrubs 18%.<sup class="reference" id="cite_ref-adw_7-4">| [8]  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 160 miles.<sup class="reference" id="cite_ref-17">| [18]  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 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--something that is becoming increasingly rare in the U.S. and worldwide."<sup class="reference" id="cite_ref-18">| [19]

Cougars, wolves,  coyotes  and  bobcats  are the major  predators. Golden Eagles have been reported to prey on fawns.

edit ] Social behavior and reproduction
EnlargeHerd of pronghornsPronghorns form mixed-sex herds in the winter. In early spring the herds break up with young males forming bachelor groups, females forming their groups and adult males living a solitary life.<sup class="reference" id="cite_ref-Byers_1997_19-0">| [20] There are female bands which share the same summer range and bachelor male bands form between spring and fall. Females form dominance hierarchies with few circular relationships.<sup class="reference" id="cite_ref-20">| [21] Dominant females will aggressively displace other females from feeding sites. EnlargeJuvenile ("fawn") in New Mexico .Adult male pronghorns employ two different mating strategies during the breeding season. A pronghorn male will defend a fixed territory that females may enter or it might defend a harem of females. A pronghorn may change mating strategies depending on environmental or demographic conditions.<sup class="reference" id="cite_ref-Byers_1997_19-1">| [20] In areas that have high precipitation, adult male pronghorn tend to be territorial and maintain their territories with scent marking, vocalizing and challenging intruders.<sup class="reference" id="cite_ref-MacDonald_21-0">| [22]  In these systems, territorial males have access to better resources than bachelor males.<sup class="reference" id="cite_ref-MacDonald_21-1">| [22]  Females also employ different mating strategies. "Sampling" females will visit several males and remain with each for a short time before switching to the next male, at an increasing rate as oestrus approaches. "Inciting" females will behave as samplers until oestrus and then incite conflicts between males. The females watch and then mate with the winners. "Quiet" females will remain with a single male in an isolated area throughout oestrus.<sup class="reference" id="cite_ref-Byers_1994_22-0">| [23]

When courting an estrous female, a male pronghorn will approach her while softly vocalizing<sup class="reference" id="cite_ref-Byers_1997_19-2">| [20] and waving his head side to side, displaying his cheek patches.<sup class="reference" id="cite_ref-23">| [24]  A receptive female will remain motionless and sniff his scent gland and then allow the male to mount her.<sup class="reference" id="cite_ref-Byers_1997_19-3">| [20]  Pronghorns have a gestation period of 235 days, longer than is typical for North American ungulates. They breed in mid-September, and the doe carries her fawn until late May. This is around six weeks longer than the white-tailed deer. Newborn pronghorns weigh 2–4 kg, most commonly 3 kg. In their first 21–26 days, a fawn spends time hiding in vegetation.<sup class="reference" id="cite_ref-MacDonald_21-2">| [22] Fawns interact with their mothers for 20–25 minutes a day and this continues even when the fawn joins a nursery.<sup class="reference" id="cite_ref-MacDonald_21-3">| [22]  The females nurse, groom, and lead their young to food and water as well as keep predators away from them.<sup class="reference" id="cite_ref-MacDonald_21-4">| [22]  Males are weaned 2–3 weeks earlier than females.<sup class="reference" id="cite_ref-MacDonald_21-5">| [22]  Sexual maturity is reached at 15 to 16 months, though males rarely breed until 3 years old. The longevity is typically up to 10 years, rarely 15 years.<sup class="reference" id="cite_ref-texas_6-4">| [7] <sup class="reference" id="cite_ref-adw_7-5">| [8]  <sup class="reference" id="cite_ref-age_8-1">| [9]

edit ] Population and conservation
EnlargePronghorns in Montana, United StatesBy the 1920s, hunting pressure had reduced the pronghorn population to about 13,000.<sup class="reference" id="cite_ref-hawes_5-4">| [6]  Protection of habitat and hunting restrictions have allowed their numbers to recover to an estimated population of between 500,000 and 1,000,000.<sup class="reference" id="cite_ref-24">| [25]  There has been some recent decline in a few localized populations,<sup class="reference" id="cite_ref-texas_6-5">| [7]  due to  blue tongue disease  which is spread from sheep; however the overall trend has been positive since conservation measures were put in place.

Pronghorn migration corridors are threatened by habitat fragmentation and the blocking of traditional migration 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.<sup class="reference" id="cite_ref-25">| [26]

Pronghorns are now quite numerous and outnumbered people in Wyoming  and parts of northern  Colorado  until just recently. It is legally hunted in western states for purposes of population control and food; the meat is rich and lean. There are no major range-wide threats, although localized declines are taking place, particularly to the Sonoran pronghorn, mainly as a result of, among others, 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.<sup class="reference" id="cite_ref-icun_0-1">| [1]

Three subspecies are considered endangered in all ( A. a. sonoriensis ,  A. a. peninsularis ), or part of their ranges (A. a. mexicana). Populations of the Sonoran pronghorn in Arizona and Mexico are protected under the US Endangered Species Act (since 1967), and a recovery plan for this subspecies has been prepared by USFWS (U.S. Fish and Wildlife Service 1998).<sup class="reference" id="cite_ref-icun_0-2">| [1] 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 trap or shoot pronghorns.<sup class="reference" id="cite_ref-icun_0-3">| [1]