Pronghorn

## Description

The pronghorn (Antilocapra americana) is a species of even-toed mammal native to 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. The pronghorn's closest living relatives are the giraffe and okapi. It is the symbol of the American Society of Mammalogists.

## Appearance

The pronghorn is tan to reddish-brown in color. Its cheeks, belly, chest, rump, and the insides of its legs are white. Males have a wide black mask running from their eyes to their noses, black parches on their necks, and pronged black horns. The horns of the male are shaped like a lyre, curving in towards each other. Females don’t have black markings, and the horns are generally straight short spikes. The pronghorn possesses horns, not antlers, and is the only animal with branched horns and the only animal that each year sheds its horns. The outer sheath falls off in the autumn and grows back every summer.

## Distribution

Pronghorns are found from southern Saskatchewan and Alberta in Canada south into the United States through Montana, Idaho, Utah, Nevada, Arizona, Nebraska, Wyoming, Colorado, New Mexico, Washington, and central Texas west to coastal southern California and northern Baja California Sur, to Sonora and San Luis Potosí in northern Mexico. Pronghorns migrate more than 260 km (160 mi) starting their travel from the foothills of the Pioneer Mountains through Craters of the Moon National Monument to the Continental Divide. These animals prefer to live in open, expansive terrain and tend to stay within 5-6.5 km (3-4 mi) of a water source. They are typically found in grasslands, chaparral, sage scrub, and desert. The southern part of their range consists mostly of open prairies and arid grasslands.

## Behavior

Pronghorns are active day and night, alternating snatches of sleep with focused feeding. They form mixed-gender herds in winter. In early spring, the herds break up, with young males forming bachelor groups, females forming harems, and adult males living solitarily. Some female bands share the same summer range, and bachelor male bands form between spring and fall. Females form dominance hierarchies with few circular relationships. Dominant females aggressively displace other females from feeding sites. Being the fastest land mammal in the Western Hemisphere, the pronghorn is built for maximum predator evasion through running. The top speed is dependent upon the length of time over which it is measured. It can run 56 km/h (35 mph) for 6.5 km (4 mi), 68 km/h (42 mph) for 1.5 km (1 mi), and 88.5 km/h (55 mph) for 800 m (1⁄2 mi). Although it is slower than the African cheetah, the pronghorn can sustain top speeds much longer than cheetahs. Pronghorns may have evolved their running ability to escape from now-extinct predators such as the American cheetah since their speed greatly exceeds that of all extant North American predators. Also have at least 13 distinct gaits, including one reaching nearly 7.3 m (23 ft 11 in) per stride.

## Diet

Pronghorns are herbivorous (graminivorous, folivorous) animals. In summer, they graze on grasses, cacti, and forbs, while in winter, they eat sagebrush and other plants that are available.

## Reproduction

Pronghorns are polygynous and don't form pairs. Late in summer or in early fall, adult males either defend a fixed territory that females may enter, or defend a harem of females. Where precipitation is high, adult males tend to be territorial and maintain their territories with scent marking, vocalizing, and challenging intruders. 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. "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. Pronghorns breed in -mid-September, and after the gestation period of 7-8 months, the female carries her fawn until late May. Twin fawns are common. Newborn pronghorns weigh 2-4 kg (4-9 lb), most commonly 3 kg (7 lb). In their first 21-26 days, fawns spend time hiding in vegetation. They 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 weaned 2-3 weeks earlier than females. Reproductive maturity is reached at 15 to 16 months, though males rarely breed until 3 years old.

## Population

### Population threats

Today, there are some localized declines taking place, especially to the Sonoran Pronghorn, mostly as a result of livestock grazing, new roads, and fences, and other barriers to historical habitat, insufficient food and water, illegal hunting (especially in Mexico), and lack of recruitment.

### Population number

According to the IUCN Red List, the total pronghorn population size is around 1 million individuals. Specific populations of this species have been estimated in such areas: fewer than 300 individuals of Sonoran pronghorn in the United States; 200-500 individuals in Mexico; around 200 Peninsular pronghorn in and around breeding centers in Baja California. Overall, currently, pronghorns are classified as Least Concern (LC) and their numbers today remain stable.

### Ecological niche

Throughout their range, these animals live alongside cattle, sheep, bison, and horses. Pronghorns improve rangeland quality for other species by eating invasive plants and noxious weeds. Introduced livestock may overgraze in areas shared with pronghorn, reducing cover and the amount of food. Reduction of cover may cause more deaths amongst the young through predation.

## Fun Facts

The pronghorn is the fastest land mammal in North America, reaching top speed of 60 mph (97 Km/h) in good conditions, and top speed of 50 mph (80 Km/h) normally.

The pronghorn is the world's fastest animal over long distances; it can run 56 km/h for 6 km (35 mph for 4 mi), 67 km/h for 1.6 km (42 mph for 1 mi), and 88.5 km/h for 0.8 km (55 mph for 0.5 mi).

Pronghorns are built for speed, not for jumping. If there was a fence, they wouldn’t jump over it, they would most likely climb under it.

Pronghorns have great eyesight; they can pick up movement from 3 miles (4.8 km) away.

Pronghorns can change the position of hairs on the skin. Straight up hairs ensure circulation of the air near the skin and the elimination of excess body heat during hot days. During the cold nights, hairs lie flat, close to the body to prevent loss of body heat.

Pronghorns are able to return food from their stomach back to the mouth and chew it several times before it becomes ready for intestinal digestion.