Equus is a genus of mammals in the family Equidae, which includes horses, asses, and zebras. Within Equidae, Equus is the only recognized extant genus, comprising seven living species. The term equine refers to any member of this genus, including horses.
Equines: Wild and Domestic
Like Equidae more broadly, Equus has numerous extinct species known only from fossils. The genus most likely originated in North America and spread quickly to the Old World. Equines are odd-toed ungulates with slender legs, long heads, relatively long necks, manes (erect in most subspecies) and long tails. All species are herbivorous and mostly grazers with simpler digestive systems than ruminants, but able to subsist on lower quality vegetation. The word equus is Latin for “horse”, and is cognate with the Greek “ἵππος” (hippos), “horse,” and Mycenaean Greek i-qo /ikkʷos/ (cf. the alternative development of the Proto-Greek labiovelar in Ionic “ἴκκος” ikkos), the earliest attested variant of the Greek word, written in Linear B syllabic script.
Equines species can crossbreed with each other. The most common hybrid is the mule, a cross between a male donkey and a female horse. With rare exceptions, these hybrids are sterile and cannot reproduce. A related hybrid, a hinny, is a cross between a male horse and a female donkey. Other hybrids include the zorse, a cross between a zebra and a horse, and a zonkey or zedonk, a hybrid of a zebra and a donkey. In areas where Grévy’s zebras are sympatric with plains zebras, fertile hybrids do occur.
Sexual dimorphism is limited in equines. The penis of the male is vascular and lacks a bone (baculum). Equines are adapted for running and for traveling over long distances. Their dentition is adapted for grazing; they have large incisors that clip grass blades and highly crowned, ridged molars well-suited for grinding. Males have spade-shaped canines (“tushes”), which can be used as weapons in fighting. Equines have fairly good senses, particularly their eyesight. Their moderately long, erect ears are movable and can locate the source of a sound.
A dun-colored coat with primitive markings that include a dorsal stripe and often leg-striping and transverse shoulder stripes reflect the wildtype coat and are observed in most wild extant equine species. Only the mountain zebra lacks a dorsal stripe. In domestic horses, dun color and primitive markings exist in some animals across many breeds. The purpose of the bold black-and-white striping of zebras has been a subject of debate among biologists for over a century, but recent (2014) evidence supports the theory that they are a form of protection from biting flies. These insects appear to be less attracted to striped coats and, compared to other wild equines, zebras live in areas with the highest fly activity.
With the exception of the domestic horses, which have long manes that lay over the neck and long tail hair growing from the top of the tailhead or dock, most equines have erect manes and long tails ending in a tuft of hair. The coats of some equine species undergo shedding in certain parts of their range and are thick in the winter.
Extant wild equines have scattered ranges across Africa and Asia. The plains zebra lives in lush grasslands and savannas of Eastern and Southern Africa, while the Mountain zebra inhabits mountainous areas of southwest Africa. The other equine species tend to occupy more arid environments with more scattered vegetation. The Grévy’s zebra is found in thorny scrubland of East Africa, while the African wild ass inhabits rocky deserts of North Africa. The two Asian wild ass species live in the dry deserts of the Near East and Central Asia and the Przwelski’s wild horse’s habitat is the deserts of Mongolia. Only the range of the plains and Grévy’s zebras overlap. In addition to wild populations, domesticated horses and donkeys are widespread thanks to humans. In certain parts of the world, populations of wild horses and donkeys exist, which are descended from domesticated animals that were released or escaped into the wild.
Equines are monogastric hindgut fermenters. They prefer to eat grasses and sedges, but may also consume bark, leaves, buds, fruits and roots if their favored foods are scarce, particularly asses. Compared to ruminants, equines have a simpler and less efficient digestive system. Nevertheless, they can subsist on lower quality vegetation. After food is passed though the stomach, it enters the sac-like cecum. where cellulose is broken down by micro-organisms. Fermentation is quicker in equines than in ruminants; 30–45 hours for a horse compared to 70–100 hours for a cow. Equines may spend 60-80 percent of their time feeding, depending on the availability and quality of vegetation. In the African savannas, the plains zebra is a pioneer grazer; mowing down the upper, less nutritious grass canopy and preparing the way for more specialized grazers like blue wildebeests and Thomson’s gazelles which depend on shorter and more nutritious grasses below.
Wild equines may spend seven hours a day sleeping. During the day, they sleep standing up while at night they lie down. They regularly rub against trees, rocks and other objects and roll in around in dust for protection against flies and irritation. Except the mountain zebra, wild equines can roll over completely.
Equines are social animals with two basic social structures. Horses, plains zebras, and mountain zebras live in stable, closed family groups or harems consisting of one adult male, several females and their offspring. These groups have their own home ranges which overlap and they tend to be nomadic. The stability of the group remains even when the family stallion dies or is displaced. Plains zebra groups gather into large herds and may create temporarily stable subgroups within a herd, allowing individuals to interact with those outside their group. Among harem-holding species, this behavior has only otherwise been observed in primates like the gelada and the hamadryas baboon.
Social grooming (which involves individuals rubbing their heads against each other and nipping with the incisors and lips) is important for easing aggression and maintaining social bonds and status. Young of both sexes leave their natal groups as they mature; females are usually abducted by outside males to be included as permanent members of their harems.
In Grévy’s zebras and the wild ass species, adults have more fluid associations and adult males will establish large territories and monopolize the females that enter them. These species live in habitats with sparser resources and standing water and grazing areas may be separated. Groups of lactating females are able to remain in groups with non-lactating ones and usually gather at foraging areas. The most dominant males establish territories near watering holes, where more sexually receptive females gather. Subdominants have territories farther away, near foraging areas. Mares may wander through several territories but will remain in one when they have young. Staying in a territory offers a female protection from harassment by outside males, as well as access to a renewable resource. Some wild populations of horse exhibit features of both the harem and territorial social systems.
In both equine social systems, excess males gather in bachelor groups. These are typically young males who are not yet ready to establish a harem or territory. With the plains zebra, the males in a bachelor group have strong bonds and have a linear dominance hierarchy. Fights between males usually occur over estrus females and involve biting and kicking.
When meeting for the first time, or after they have separated, individuals may greet each other by rubbing and sniffing their noses followed by rubbing their cheeks, moving their noses along their bodies and sniffing each other’s genitals. They then may rub and press their shoulders against each other and rest their heads on one another. This greeting is usually performed among harem or territorial males or among bachelor males playing.
Equines produce a number of vocalizations and noises. Loud snorting is associated with alarm. Squealing is usually made when in pain, but bachelors will also squeal while play fighting. The contact calls of equines vary from the whinnying and nickering of the horse, the barking of plains zebras, and the braying of asses and Grévy’s zebras. Equines also communicate with visual displays and the flexibility of their lips allows them to make complex facial expressions. Visual displays also incorporate the positions of the head, ears and tail. An equine may signal an intention to kick by laying back its ears and sometimes lashing the tail. Flattened ears, bared teeth and abrupt movement of the heads may be used as threatening gestures, particularly among stallions.
Among harem-holding species, the adult females mate only with their harem stallion, while in other species, mating is more promiscuous and the males have larger testes for sperm competition. Estrous in female equines lasts 5–10 days; physical signs include frequent urination, flowing muscus, and a swollen, everted labia. In addition, estrous females will stand with their hind legs spread and raise their tails when in the presence of a male. Males assess the female’s reproductive state with the flehmen response and the female will solicit mating by backing in. Length of gestation varies by species, it is roughly 11 to 13 months, and most mares will come into estrus again within a few days after foaling, depending on conditions. Usually, only a single foal is born, which is capable of running within an hour. Within a few weeks, foals will attempt to graze, but may continue to nurse for 8–13 months. Species in arid habitats, like the Grévy’s zebra, have longer nursing intervals and do not drink water until they are three months old.
Among harem-holding species, foals are cared for mostly by their mothers, but if threatened by predators, the entire group works together to protect all the young. The group forms a protective front with the foals in the center and the stallion will rush at predators that come too close. In territory-holding species, mothers may gather into small groups and leave their young in “kindergartens” under the guard of a territorial male while searching for water. Grévy’s zebra stallions may look after a foal in his territory to ensure that the mother stays, even though it may not be his.
The earliest archaeological evidence for the domestication of the horse comes from sites in Ukraine and Kazakhstan, dating to approximately 4000-3500 BC. By 3000 BC, the horse was completely domesticated and by 2000 BC there was a sharp increase in the number of horse bones found in human settlements in northwestern Europe, indicating the spread of domesticated horses throughout the continent. The most recent, but most irrefutable, evidence of domestication comes from sites where horse remains were interred with chariots in graves of the Sintashta and Petrovka cultures c. 2100 BC. Studies of variation in genetic material shows that very few wild stallions, possibly all from a single haplotype, contributed to the domestic horse, while many mares were part of early domesticated herds.
Archaeological, biogeographical, and linguistic evidence suggest that the donkey was first domesticated by nomadic pastoral people in North Africa over 5,000 years ago. The animals were used to help cope with the increased aridity of the Sahara and the Horn of Africa. Genetic evidence finds that the donkey was domesticated twice based on two distinct mitochondrial DNA haplogroups. It also points to a single ancestor, the Nubian wild ass. Attempts to domesticate zebras were largely unsuccessful, though Walter Rothschild trained some to draw a carriage in England.
Humans have had a great impact on the populations of wild equines. Threats to wild equines include habitat destruction and conflicts with local people and livestock. Since the 20th century, wild equines have been decimated over many of their former ranges and their populations scattered. In recent centuries, two subspecies, the quagga and the tarpan, became extinct. Only the plains zebra remains numerous and widespread. The IUCN lists the African wild ass as critically endangered, the Grévy’s zebra, mountain zebra and Przewalski’s horse as endangered, the Onager as vulnerable, the kiang as lower risk and the plains zebra as least concern. The Przewalski’s horse was considered to be extinct in the wild from the 1960s to 1996. However, following successful captive breeding, it has been reintroduced in Mongolia.
Some wild horses vary in degree of protection and generate considerable controversy. For example, in Australia, they are considered a non-native invasive species, often viewed as pests, though are also considered to have some cultural and economic value. In the United States, wild horses and burros are generally considered an introduced species because they are descendants from domestic horses brought to the Americas from Europe. While they are viewed as pests by many livestock producers, conversely, there is also a view that E. ferus caballus is a reintroduced once-native species returned to the Americas that should be granted endangered species protection. At present, certain free-roaming horses and burros have federal protection as “living symbols of the historic and pioneer spirit of the West” under the Wild and Free-Roaming Horses and Burros Act of 1971, and in Kleppe v. New Mexico, the United States Supreme Court ruled that the animals so designated were, as a matter of law, wildlife.
Galleries of the World’s Most Common Wild Horse Breeds
The mustang is a free-roaming horse of the American west that first descended from horses brought to the Americas by the Spanish. The original mustangs were Colonial Spanish horses, but many other breeds and types of horses contributed to the modern mustang, resulting in varying phenotypes. In the 21st century, mustang herds vary in the degree to which they can be traced to original Iberian horses. Some contain a greater genetic mixture of ranch stock and more recent breed releases, while others are relatively unchanged from the original Iberian stock, most strongly represented in the most isolated populations.
In 1971, the United States Congress recognized that “wild free-roaming horses and burros are living symbols of the historic and pioneer spirit of the West, which continue to contribute to the diversity of life forms within the Nation and enrich the lives of the American people.” The free-roaming mustang population is managed and protected by the Bureau of Land Management (BLM). Controversy surrounds the sharing of land and resources by the free-ranging mustangs with the livestock of the ranching industry, and also with the methods with which the federal government manages the wild population numbers. A policy of rounding up excess population and offering these horses for adoption to private owners has been inadequate to address questions of population control, and many animals now live in temporary holding areas, kept in captivity but not adopted to permanent homes. Advocates for mustangs also express concerns that the animals may be sold for horse meat. Additional debate centers on the question of whether mustangs — and horses in general — are a native species or an introduced invasive species. Many methods of population management are used, including the adoption by private individuals of horses taken from the range.
Etymology and Usage
The English word mustang comes from the 16th-century Mexican Spanish word mestengo, defined as “animal that strays.” It is derived from the Spanish word mestengo (variant of mesteño), defined as “wild, stray, ownerless.” The Spanish word in turn may possibly originate from the Latin expression mixta, referring to beasts of uncertain ownership, which were distributed by rancher’s associations called mestas in Spain in the Middle Ages.
“Mustangers” were usually cowboys in the U.S. and vaqueros or mesteñeros in Mexico who caught, broke, and drove free-ranging horses to market in the Spanish and later Mexican, and still later American, territories of what is now Northern Mexico, Texas, New Mexico, and California. They caught the horses that roamed the Great Plains and the San Joaquin Valley of California, and later in the Great Basin, from the 18th century to the early 20th century.
The original mustangs were Colonial Spanish horses, but many other breeds and types of horses contributed to the modern mustang, resulting in varying phenotypes. Mustangs of all body types are described as surefooted and having good endurance. They may be of any coat color. Throughout all the Herd Management Areas (HMAs) managed by the Bureau of Land Management, light riding horse type predominates, though a few horses with draft horse characteristics also exist, mostly kept separate from other mustangs and confined to specific areas. Some herds show the signs of the introduction of Thoroughbred or other light racehorse-types into herds, a process that also led in part to the creation of the American Quarter Horse.
The now-defunct American Mustang Association developed a breed standard for those mustangs that carry morphological traits associated with the early Spanish horses. These include a well-proportioned body with a clean, refined head with wide forehead and small muzzle. The facial profile may be straight or slightly convex. Withers are moderate in height and the shoulder is to be “long and sloping.” The standard considers a very short back, deep girth and muscular coupling over the loins as desirable. The croup is rounded, neither too flat nor goose-rumped. The tail is low-set. The legs are to be straight and sound. Hooves are round and dense. Dun color and primitive markings are particularly common amongst horses of Spanish type. Height varies across the west, but most are small, generally 14 to 15 hands (56 to 60 inches, 142 to 152 cm), and not taller than 16 hands (64 inches, 163 cm), even in herds with draft or Thoroughbred ancestry.
The mustang of the modern west has several different breeding populations today which are genetically isolated from one another and thus have distinct traits traceable to particular herds. Genetic contributions to today’s free-roaming mustang herds include assorted ranch horses that escaped to or were turned out on the public lands, and estray horses used by the United States Cavalry. For example, some Herd Management Areas (HMA) in Idaho contain animals with known descent from Thoroughbred and Quarter Horse stallions turned out with wild herds. The herds located in two HMAs in central Nevada produce Curly Horses. Others, such as certain bands in Wyoming, have characteristics consistent with gaited horse breeds.
Several bands have had DNA testing and are verified to have significant Spanish ancestry. These include the Kiger Mustang, the Cerbat Mustang, and the Pryor Mountain Mustang. Horses in several other HMAs retain Spanish horse traits, such as dun coloration and primitive markings. Other genetic herd studies, such as one done in 2002 on the bands in the Challis, Idaho area, show a very mixed blend of Spanish, North American gaited horse, draft horse and pony influences.
Mustangs in Utah
Some breeders of domestic horses consider the mustang herds of the west to be inbred and of inferior quality. However, supporters of the mustang argue that the animals are merely small due to their harsh living conditions and that natural selection has eliminated many traits that lead to weakness or inferiority. In contrast, a few researchers have advanced an argument that mustangs should be legally classified as “wild” rather than “feral”. They argue that, due to the presence of Equus ferus on the North American continent until the end of the Pleistocene era, horses were once a native species and should still be considered as such, defined as “wild” rather than viewed as an introduced species that draws resources and attention away from true native species.
The horse family Equidae and the genus Equus evolved in North America. Fossil evidence dating to the Eocene Studies using ancient DNA as well as DNA of recent individuals shows there once were two closely related horse species in North America, the wild horse (Equus ferus), and Equus francisci or “New World stilt-legged horse” (taxonomically assigned to various names). Horses existed in Canada as recently as 12,000 years ago, and a 1992 study produced evidence that horses existed in the Americas until 8,000–10,000 years ago.
Today, the only extant true “wild horse” is the Przewalski’s horse, native to Mongolia. The genus Equus in North America died out at the end of the last ice age, possibly due to a changing climate or the impact of newly arrived human hunters. Thus at the beginning of the Columbian Exchange, there were no equids in the Americas at all.
Horses first returned to the Americas with the conquistadors, beginning with Columbus, who imported horses from Spain to the West Indies on his second voyage in 1493. Domesticated horses came to the mainland with the arrival of Cortés in 1519. By 1525, Cortés had imported enough horses to create a nucleus of horse-breeding in Mexico.
One hypothesis held that horse populations north of Mexico originated in the mid-1500s with the expeditions of Narváez, de Soto or Coronado, but it has been refuted. Horse breeding in sufficient numbers to establish a self-sustaining population developed in what today is the southwestern United States starting in 1598 when Juan de Oñate founded Santa Fe de Nuevo México. From 75 horses in his original expedition, he expanded his herd to 800, and from there the horse population increased rapidly.
Dispersal of Horses, 1600-1775
While the Spanish also brought horses to Florida in the 16th century, the Choctaw and Chickasaw horses of what is now the southeastern United States are believed to be descended from western mustangs that moved east, and thus Spanish horses in Florida did not influence the mustang.
17th and 18th Century Dispersal
Native American people readily integrated use of the horse into their cultures, and quickly adopted the horse as a primary means of transportation. Horses replaced the dog as a travois puller and greatly improved success in battles, trade, and hunts, particularly bison hunts.
Santa Fe became a major trading center in the 1600s. Although Spanish laws prohibited Native Americans from riding horses, the Spanish used Native people as servants, and some were tasked to care for livestock, thus learning horse-handling skills. Oñates’ colonists also lost many of their horses. Some wandered off because the Spanish generally did not keep them in fenced enclosures, and Native people in the area captured some of these strays. Other horses were traded by Oñates’ settlers for food, women, or other goods. Initially, horses obtained by Native people were simply eaten, along with any cattle that were captured or stolen. But as individuals with horse-handling skills fled Spanish control, sometimes with a few trained horses, the local tribes began using horses for riding and as pack animals. By 1659, settlements reported being raided for horses, and in the 1660s the “Apache” were trading human captives for horses. The Pueblo Revolt of 1680 also resulted in large numbers of horses coming into the hands of Native people, the largest one-time influx in history.
From the Pueblo people, horses were traded to the Apache, Navajo, and Utes. The Comanche acquired horses and provided them to the Shoshone. The Eastern Shoshone and Southern Utes became traders who distributed horses and horse culture from New Mexico to the northern plains. West of the Continental Divide, horses distribution moved north quite rapidly along the western slopes of the Rocky Mountains, skirting desert regions such as the Great Basin and the western Colorado Plateau. Horses reached what today is southern Idaho by 1690. The Northern Shoshone people in the Snake River valley had horses in 1700.
By 1730, they reached the Columbia Basin and were east of the Continental divide in the northern Great Plains. The Blackfeet people of Alberta had horses by 1750. The Nez Perce people in particular became master horse breeders, and developed one of the first distinctly American breeds, the Appaloosa. Most other tribes did not practice extensive amounts of selective breeding, though they sought out desirable horses through acquisition and quickly weeded out those with undesirable traits. By 1769, most Plain Indians had horses.
In this period, Spanish Missions were also a source of estray and stolen livestock, particularly in what today is Texas and California. The Spanish brought horses to California for use at their missions and ranches, where permanent settlements were established in 1769. Horse numbers grew rapidly, with a population of 24,000 horses reported by 1800. By 1805, there were so many horses in California that people began to simply kill unwanted animals to reduce overpopulation. However, due to the barriers presented by mountain ranges and deserts, the California population did not significantly influence horse numbers elsewhere at the time. Horses in California were described as being of “exceptional quality.”
In the upper Mississippi basin and Great Lakes regions, the French were another source of horses. Although horse trading with native people was prohibited, there were individuals willing to indulge in illegal dealing, and as early as 1675, the Illinois people had horses. Animals identified as “Canadian,” “French”, or “Norman” were located in the Great Lakes region, with a 1782 census at Fort Detroit listing over 1000 animals. By 1770, Spanish horses were found in that area, and there was a clear zone from Ontario and Saskatchewan to St. Louis where Canadian-type horses, particularly the smaller varieties, crossbred with mustangs of Spanish ancestry. French-Canadian horses were also allowed to roam freely, and moved west, particularly influencing horse herds in the northern plains and inland northwest.
Although horses were brought from Mexico to Texas as early as 1542, a stable population did not exist until 1686, when Alonso de León’s expedition arrived with 700 horses. From there, later groups brought up thousands more, deliberately leaving some horses and cattle to fend for themselves at various locations, while others strayed. By 1787, these animals had multiplied to the point that a roundup gathered nearly 8,000 “free-roaming mustangs and cattle.” West-central Texas, between the Rio Grande River and Palo Duro Canyon, was said to have the most concentrated population of wild horses in the Americas. Throughout the west, horses escaped human control and formed wild herds, and by the late 1700s, the largest numbers were found in what today are the states of Texas, Oklahoma, Colorado, and New Mexico.
Estimates of when the peak population of mustangs occurred and total numbers vary widely between sources. No comprehensive census of wild horse numbers was ever performed until the time of the Wild and Free-Roaming Horses and Burros Act of 1971 and any earlier estimates, particularly prior to the 20th century, are speculative. Some sources simply state that “millions” of mustangs once roamed western North America. In 1959, geographer Tom L. McKnight suggested that the population peaked in the late 1700s or early 1800s, and the “best guesses apparently lie between two and five million”. Historian J. Frank Dobie hypothesized that the population peaked around the end of the Mexican–American War in 1848, stating, “My own guess is that at no time were there more than a million mustangs in Texas and no more than a million others scattered over the remainder of the West.” J. Edward de Steiger questioned Dobie’s lower guess as still being too high.
In 1839, the numbers of mustangs in Texas had been augmented by animals abandoned by Mexican settlers who had been ordered to leave the Nieces Strip. When the area was finally ceded to the U.S. in 1848, these horses and others in the surrounding areas were rounded up and trailed north and east, resulting in the near elimination of mustangs in that area by 1860.
The first known sighting of a free-roaming horse in the Great Basin was by John Bidwell near the Humboldt Sinks in 1841. Although Fremont noted thousands of horses in California, the only horse sign he spoke of in the Great Basin, which he named, was tracks around Pyramid Lake, and the natives he encountered there were horseless. In 1861, another party saw seven free-roaming horses near the Stillwater Range. For the most part, free-roaming horse herds in the interior of Nevada were established in the latter part of the 1800s from escaped settlers’ horses.
In the early 1900s, thousands of free-roaming horses were rounded up for use in the Spanish–American War and World War I.
By 1920, Bob Brislawn, who was working as a packer for the U.S. government, recognized that the original mustangs were disappearing, and was making an effort to preserve them, ultimately establishing the Spanish Mustang Registry. In 1934, Dobie stated that there were just “a few wild horses in Nevada, Wyoming, and other Western states” and that “only a trace of Spanish blood is left in most of them” remaining. Other sources agree that by that time, only “pockets” of mustangs that retained Colonial Spanish Horse type remained.
By 1930, the vast majority of free-roaming horses were found west of Continental Divide, with an estimated population between 50,000–150,000. They were almost completely confined to the remaining General Land Office (GLO)-administered public lands and National Forest rangelands in the 11 Western States. In 1934, the Taylor Grazing Act established the United States Grazing Service to manage livestock grazing on public lands, and in 1946, the GLO was combined with the Grazing Service to form the Bureau of Land Management (BLM), which, along with the U.S. Forest Service, was committed to removing wild horses from the lands they administered.
By the 1950s, the mustang population dropped to an estimated 25,000 horses. Abuses linked to certain capture methods, including hunting from airplanes and poisoning water holes, led to the first federal free-roaming horse protection law in 1959. This statute, titled “Use of aircraft or motor vehicles to hunt certain wild horses or burros; pollution of watering holes” popularly known as the Wild Horse Annie Act, prohibited the use of motor vehicles for capturing free-roaming horses and burros. Protection was increased further by the Wild and Free-Roaming Horses and Burros Act of 1971.
The Wild and Free-Roaming Horses and Burros Act of 1971 provided for protection of certain previously established herds of horses and burros. It mandated the BLM to oversee the protection and management of free-roaming herds on lands it administered, and gave U.S. Forest Service similar authority on National Forest lands. A few free-ranging horses are also managed by the Fish and Wildlife Service and National Park Service, but for the most part they are not subject to management under the Act. A census completed in conjunction with passage of the Act found that there were approximately 17,300 horses (25,300 combined population of horses and burros) on the BLM-administered lands and 2,039 on National Forests.
As of 2015, some populations of free-roaming horses and burros remain protected under the Act, but others have disappeared from places where there were once established populations. A few hundred free-roaming horses survive in Alberta and British Columbia. The BLM considers roughly 26,000 individuals a manageable number, but it claims that the wild mustang population in February 2010 was 33,700 horses and 4,700 burros. More than half of all mustangs in North America are found in Nevada (which features the horses on its State Quarter in commemoration of this), with other significant populations in California, Oregon, Utah, Montana, and Wyoming. Another 34,000 horses are in holding facilities.
Land Use Controversies
Controversy surrounds the presence of wild mustang herds, particularly on public lands. Supporters argue that mustangs are part of the natural heritage of the American West, whose history predates modern land use practices, and thus the animals have an inherent right of inhabitation. However, others remain vehemently opposed to their presence, arguing that the animals degrade rangeland and compete with livestock and wild species for forage.
The debate as to what degree mustangs and cattle compete for forage is multifaceted. One group of opponents, primarily cattle and sheep ranchers and those who depend on the livestock industry, argue essentially that wild horses degrade rangeland and compete with private livestock for public land forage. The environmentalist community is split over the position of the mustang within the North American ecosystem. This debate centers on the potential classification of mustangs as either an introduced species such as cattle, or as a reintroduced native species due to the prehistoric presence of horses in North America, albeit with a gap of thousands of years between their extinction and reintroduction from European stock.
Researchers note that most current mustang herds live in arid areas which cattle cannot fully utilize due to the lack of water sources. Horses are adapted by evolution to inhabit an ecological niche characterized by poor quality vegetation. They cover vast distances to find food and water. They may range nine times as far from water sources as cattle, traveling as much as 50 miles a day. In addition, horses are “handgun fermenters,” meaning that they digest nutrients by means of the cecum rather than by a multi-chambered stomach. While this means that they extract less energy from a given amount of forage, it also means that they can digest food faster and make up the difference in efficiency by increasing their consumption rate. In practical effect, by eating greater quantities, horses can obtain adequate nutrition from poorer forage than can ruminants such as cattle, surviving in areas where cattle will starve. In addition to consuming more fodder than cattle, horses’ incisors allow them to graze plants much closer to the ground. For these reasons, the BLM claims that the number of horses has to be kept low enough to not exceed the carrying capacity of a given area.
While the BLM rates horses by Animal Unit (AUM) to eat the same amount of forage as a cow-calf pair, 1.0, multiple studies of horse grazing patterns indicate that horses probably consume forage at a rate closer to 1.5 AUM. Modern rangeland management also recommends removing all livestock during the growing season to maximize recovery of the forage. Allowing livestock to graze year-round is not good for the range, and so mismanagement of wild herds can also degrade the range for the wildlife that shares the same area.
Management and Adoption
The Bureau of Land Management (BLM) is tasked with protecting, managing, and controlling wild horses and burros under the authority of the Wild and Free-Roaming Horses and Burros Act of 1971 to ensure that healthy herds thrive on healthy rangelands and as multiple-use mission under the 1976 Federal Land Policy and Management Act. Under the 1971 act, shooting or poisoning mustangs in the wild is illegal, and doing so can be prosecuted as a criminal felony.
Healthy adult mustangs have few natural predators aside from mountain lions, and to a lesser extent, the grizzly bear and the gray wolf. The mountain lion is well known for predation on wild horses, and the larger members of the species may hunt both horses and moose. They are very effective predators that kill by either leaping onto an animal or chasing it down in a sprint, then grabbing the prey with their front claws and biting the neck, either at the windpipe or the spine.
Where there is natural balance of predators and prey, mustang numbers tend to stay in balance. However, in many areas, natural predators have been eliminated from the ecosystem. Without some form of population control, mustang herd sizes can multiply rapidly, doubling as fast as every four years. To maintain population balance (though some argue the purpose is to make room for cattle) one of the BLM’s key mandates under the 1971 law is to determine an appropriate management level (AML) of wild horses and burros in areas of public rangelands dedicated specifically for them. To maintain population balance, one of the BLM’s key mandates under the 1971 law is to determine an appropriate management level (AML) of wild horses and burros in areas of public rangelands dedicated specifically for them.
Control of the population to within AML is achieved through a capture program. There are strict guidelines for techniques used to round up mustangs. One method uses a tamed horse, called a “Judas horse,” which has been trained to lead wild horses into a pen or corral. Once the mustangs are herded into an area near the holding pen, the Judas horse is released. Its job is then to move to the head of the herd and lead them into a confined area.
Most horses that are captured are offered for adoption to individuals or groups willing and able to provide humane, long-term care after payment of an adoption fee of at least $125. In order to prevent the later sale of mustangs as horse meat, adopted mustangs are still protected under the Act, and cannot be sold in the first year except when certain very specific criteria are met. As of 2010, nearly 225,000 mustangs have been adopted.
In January 2005, a controversial amendment was attached to an appropriation bill before the United States Congress by former Senator Conrad Burns, dubbed the “Burns rider.” This modified the adoption program to allow the sale (with the result usually being slaughter) of captured horses that are “more than 10 years of age”, or that were “offered unsuccessfully for adoption at least three times.”
In 2009, Secretary of the Interior Ken Salazar proposed the creation of federal wild horse preserves in the midwest, where non-reproducing animals would be kept. Another approach to placing excess animals has been advanced by Madeleine A. Pickens, former wife of oil magnate T. Boone Pickens, who sought to create a private sanctuary in northern Nevada. There are also increased efforts to assist with finding appropriate adoption homes. One example is a promotional competition, The Extreme Mustang Makeover, that gives trainers 100 days to gentle and train 100 mustangs, which are then adopted through an auction.
Free-roaming mustangs are freeze-branded on the left side of the neck by the BLM, using the International Alpha Angle System, a system of angles and alpha-symbols that cannot be altered. The brands begin with a symbol indicating the registering organization, in this case the U.S. Government, then two stacked figures indicating the individual horse’s date of birth, then the individual registration number. Mustangs kept in sanctuaries are also marked on the left hip with four inch-high Arabic numerals that are also the last four digits of the freeze brand on the neck.
Learn More About America’s Wild Horses
Are wild horses truly “wild,” as an indigenous species in North America, or are they “feral weeds” – barnyard escapees, far removed genetically from their prehistoric ancestors? The question at …
Modern horses, zebras, and asses belong to the genus Equus, the only surviving genus in a once diverse family, the Equidae. Based on fossil records, the genus appears to have …
The wild mustang, free from the constraints of a saddle and spurs, roaming the great expanse with a wind-swept mane, has long been a powerful symbol of the American West, …
“Horse people,” a guy named Monty in a cowboy hat tells me, “always cry when they leave here.” We are at Mustang Monument, a 900-square-mile luxury eco resort and wild-horse …
The Wild Free-Roaming Horses and Burros Act of 1971 (Public Law 92-195) as written outlines everything the wild horses and burros need. There’s very little wrong with the law. It’s …
History from 1975-2010
By Laura Moretti, The Animals Voice
Fifty million years ago, a small dog-like creature called Eohippus, meaning “dawn horse,” evolved on the North American continent. In fact, …
Przewalski’s horse (pronounced /ʃəˈvælski/ shə-val-skee or /pʃəˈvælski/ pshə-val-skee; Khalkha Mongolian: тахь, takhi; Ak Kaba Tuvan: [daɣə//daɢə] dagy; Polish: [pʂɛˈvalskʲi]; Equus ferus przewalskii) or Dzungarian horse, is a rare and endangered subspecies of wild horse (Equus ferus) native to the steppes of central Asia. At one time extinct in the wild (in Mongolia, the last wild Przewalski’s horses had been seen in 1966), it has been reintroduced to its native habitat in Mongolia at the Khustain Nuruu National Park, Takhin Tal Nature Reserve, and Khomiin Tal. The taxonomic position is still debated, and some taxonomists treat Przewalski’s horse as a species, Equus przewalskii.
Common names for this equine include takhi, Asian wild horse and Mongolian wild horse, The horse is named after the Russian geographer and explorer Nikolay Przhevalsky.
Most “wild” horses today, such as the American Mustang or the Australian Brumby, are actually feral horses descended from domesticated animals that escaped and adapted to life in the wild. In contrast, Przewalski’s horse has never been domesticated and remains the only truly wild horse in the world today. Przewalski’s horse is one of three known subspecies of Equus ferus, the others being the domesticated horse Equus ferus caballus, and the extinct tarpan Equus ferus ferus. There are still a number of other wild equines, including three species of zebra and various subspecies of the African wild ass, onager (including the Mongolian wild ass), and kiang.
Many believe that the Przewalski horse is the closest relative to the domestic horse. DNA sequencing has been done to test whether or not the Przewalski horse is the primogenitor of domestic horses, but it was found that they are not. If Przewalski horses were indeed the ancestors of domesticated horses, those sequences, too would have been found within the Przewalski horse sequences. The DNA was then tested the other way as well; domestic horse sequences were checked for Przewalski horse sequences, and were found to contain none. This puts to rest the theory that Przewalski horses were derived from domestic horses. Studies of the DNA diversity within the Przewalski horses have been done to see how successful their reintroduction into the wild may be. Studies have shown through multidimensional scaling analyses that tight grouping occurs within most horse breeds, close grouping between related breeds, and far less grouping between mixed breeds. The Przewalski horse and the domesticated horse showed a close relationship through pairwise genetic distance and multidimensional scaling analyses showing that the Przewalski horse is very closely related to the domesticated horse.
The Przewalski’s horse was described in 1881 by L. S. Poliakov. The taxonomic position of Przewalski’s horse has always been problematic and no consensus exists whether it is a full species (Equus przewalskii), a subspecies of the wild horse (Equus ferus przewalskii), or even a sub-population of the domestic horse (Equus ferus caballus). Studies using DNA have been inconclusive, in part due to crossing domestic horses into the Przewalski’s horse as well as the limited genetic variation present in the founder population of the Przewalski’s horse. A 2009 molecular study using ancient DNA recovered from archaeological finds like bones and teeth places the Przewalski’s horse in the middle of the domesticated horses, but 2011 mitochondrial DNA analysis suggests that the Przewalski and the modern domestic horse diverged some 160,000 years ago. An analysis based on whole genome sequencing and calibration with DNA from old horse bones gave a divergence date of 38–72 thousand years ago. The karyotype of the domestic horse differs from that of Przewalski’s horse by an extra chromosome pair either because of the ﬁssion of domestic horse chromosome 5 in Przewalski’s horse or fusion of Przewalski’s horse chromosomes 23 and 24 in the domestic horse. In comparison, the chromosomal differences between domestic horses and zebras include numerous translocations, fusions, and inversions. Przewalski’s horse is known to have the highest diploid chromosome number among all equine species. Przewalski’s horse can interbreed with the domestic horse and produce fertile offspring (65 chromosomes).
Every Przewalski horse presently living is descended from 9 of the 13 horses captured in 1945. Two of these were hybrids, one sired from a wild horse stallion and domestic mare and the other from a wild stallion and a tarpan mare. These 13 horses were descended in turn from approximately 15 captured around 1900. A cooperative venture between the Zoological Society of London and Mongolian scientists has resulted in successful reintroduction of these horses from zoos into their natural habitat in Mongolia; and as of 2011 there is an estimated free-ranging population of over 300 in the wild. From a population of 13 horses held in captivity in 1945, the total number by the early 1990s was over 1,500.
A population introduced in 1998 now exists in the Chernobyl Exclusion Zone protected from the interference by humans.
Przewalski females are able to give birth at the age of three and have a gestation period of about 11 to 12 months. Their reproduction process is seasonal and in Mongolia the season is towards the end of either May, June, or July. Mating stallions do not start looking for mating partners until the age of five. Instinctively, the stallion will look to create his own group of mares or else wander until he finds a group with its own leader. If the stallion finds a group of mares with its own leader, the stallion will usually fight the other leader stallion of the group. The mares will adjust and follow the victor. After birth, the foal can stand almost immediately (only taking about an hour or so) and can walk on its own. The foals drink milk from the mother mare.
Przewalski’s horse is stockily built in comparison to domesticated horses, with shorter legs. Typical height is about 12–14 hands (48–56 inches, 122–142 cm), length is about 2.1 m (6 ft 11 in). They weigh around 300 kilograms (660 lb). The coat is generally dun in color with pangaré features, varying from dark brown around the mane (which stands erect) to pale brown on the flanks and yellowish-white on the belly and around the muzzle. The legs of Przewalski’s horse are often faintly striped, also typical of primitive markings. The tail is about 90 cm (35.43 in) long, with a longer dock and shorter hair than seen in domesticated horses.
The hooves of the Przewalski’s horse are longer in the back and have significantly thicker sole horn than feral horses. This is beneficial as it improves the performance of the hooves.
The Przewalski’s horse has 66 chromosomes, compared to 64 in all other horse species.
In the wild, Przewalski’s horses live in small, permanent family groups consisting of one adult stallion, one to three mares, and their common offspring. Offspring stay in the family group until they are no longer dependent, usually at two or three years old. Bachelor stallions, and sometimes old stallions, join bachelor groups. Family groups can join together to form a herd that moves together.
The patterns of their daily lives exhibit horse behavior similar to that of feral horse herds. Stallions herd, drive and defend all members of their family, while the mare often displays leadership in the family. Stallions and mares stay with their preferred partner for years. While behavioral synchronization is high among mares, stallions other than the main harem stallion are generally less stable in this respect.
Horses maintain visual contact with their family and herd at all times and have a host of ways to communicate with one another, including vocalizations, scent marking, and a wide range of visual and tactile signals. Each kick, groom, tilt of the ear, or other contact with another horse is a means of communicating. This constant communication leads to complex social behaviors among Przewalski’s horses.
The Przewalski horse’s diet consists mostly of vegetation. There are many plant species in a typical Przewalski horse environment including: Elymus repens, Carex spp., Fabaceae and Asteraceae. While the horses eat a variety of different plant species, they tend to favor one species during a specific time of the year. In other words, the Przewalski horses have seasonal food preferences. In the springtime, Przewalski horses favor Elymus repens, Corynephorus canescens, Festuca valesiaca and Chenopodium album. In early summer they favor Dactylis glomerata and Trifolium and in late summer, they gravitate towards Elymus repens and Vicia cracca. In winter, for example, the horses eat Salix spp., Pyrus communis, Malus sylvatica, Pinus sylvestris, Rosa spp., and Alnus spp. Additionally, Przewalski horses may dig for Festuca spp., Bromus inermis and Elymus repens that grow beneath the ice and snow. The Przewalski horse’s winter diet is very similar to the diet of domestic horses. Studies have suggested that in the wintertime, Przewalski horses experience hypodermis. Hypodermis is a condition in which one’s metabolic rate slows down. This means that in the winter time, Przewalski horse’s process their food more slowly than they do during other times of the year. Looking at the species diet overall, however, Przewalski horses most often eat Elymus repens, Trifolium pratense, Vicia cracca, Poa trivialis, Dactylis glomerata, and Bromus inermis.
In the 15th century, Johann Schiltberger recorded one of the first European sightings of the horses in the journal of his trip to Mongolia as a prisoner of the Mongol Khan. The horse is named after the Russian colonel Nikolai Przhevalsky (1839–1888) (the name is of Polish origin and “Przewalski” is the Polish spelling). He was the explorer and naturalist who first described the horse in 1881, after having gone on an expedition to find it, based on rumors of its existence. Many of these horses were captured around 1900 by Carl Hagenbeck and placed in zoos. As noted above, about twelve to fifteen reproduced and formed today’s population.
The native population declined in the 20th century due to a combination of factors, with the wild population in Mongolia dying out in the 1960s. The last herd was sighted in 1967 and the last individual horse in 1969. Expeditions after this failed to locate any horses, and the species had been designated “extinct in the wild” for over 30 years.
After 1945 only two captive populations in zoos remained, in Munich and in Prague. The most valuable group, in Askania Nova, Ukraine, was shot by German soldiers during World War II occupation, and the group in the United States had died out. Competition with livestock, hunting, capture of foals for zoological collections, military activities, and harsh winters recorded in 1945, 1948 and 1956 are considered to be the main causes of the decline in the Przewalski’s horse population. By the end of the 1950s, only 12 individual Przewalski’s horses were left in the world.
In 1977, the Foundation for the Preservation and Protection of the Przewalski horse was founded in Rotterdam, the Netherlands, by Jan and Inge Bouman. The Foundation started a program of exchange between captive populations in zoos throughout the world to reduce inbreeding, and later began a breeding program of its own. As a result of such efforts, the extant herd has retained a far greater genetic diversity than its genetic bottleneck made likely.
In 1992, sixteen horses were released into the wild in Mongolia, followed by additional animals later on. One of the areas to which they were reintroduced became Khustain Nuruu National Park in 1998. Another reintroduction site is Great Gobi B Strictly Protected Area, located at the fringes of the Gobi desert. Lastly, in 2004 and 2005, 22 horses were released by the Association Takh to a third reintroduction site in the buffer zone of the Khar Us Nuur National Park, in the northern edge of the Gobi ecoregion. In the winter of 2009-2010, one of the worst “dzud” or snowy winter conditions ever hit Mongolia. The population of the Prezewalski’s horse in the Great Gobi B SPA was drastically affected, providing clear evidence of the risks associated with reintroducing small and sequestered species in unpredictable and unfamiliar environments.
Since 2011, Prague Zoo has transported twelve horses to Mongolia in three rounds, in cooperation with partners (Czech Air Force, European Breeding Programme for Przewalski’s Horses, Association pour de cheval du Przewalski : Takh, Czech Development Agency, Czech Embassy in Mongolia and others) and it plans to continue to return horses to the wild in the future. In the framework of the project Return of the Wild Horses it sustains its activities by supporting local inhabitants. The Zoo has the longest uninterrupted history of breeding of Przewalski’s horses in the world and keeps the studbook of this species.
The reintroduced horses successfully reproduced, and the status of the animal was changed from “extinct in the wild” to “endangered” in 2005. On the IUCN Red List, they were reclassified from “extinct in the wild” to “critically endangered” after a reassessment in 2008 and from “critically endangered” to “endangered” after a 2011 reassessment.
While dozens of zoos worldwide have Przewalski’s horses in small numbers, there are also specialized reserves dedicated primarily to the species. The world’s largest captive breeding program for Przewalski’s horses is at the Askania Nova preserve in Ukraine. Several dozen Przewalski’s horses were also released in the area evacuated after the Chernobyl accident, which now serves as a deserted de facto nature reserve. In Chernobyl, the population reproduced at a high rate, reaching up to 200 individuals until poachers decreased their number to just 60 in recent years. As of 2011, it was estimated that only 30–40 individuals remained. An intensely researched population of free-ranging animals was also introduced to the Hortobágy National Park puszta in Hungary; data on social structure, behavior and diseases gathered from these animals is used to improve the Mongolian conservation effort.
Several American zoos also collaborated in breeding Equus ferus przewalskii from 1979 to 1982. Recent advances in equine reproductive science in the United States also have potential to further preserve and expand the gene pool. In October 2007, scientists at the Smithsonian Institution’s National Zoo successfully reversed a vasectomy on a Przewalski’s horse — the first operation of its kind on this species and possibly the first ever on any endangered species. While normally a vasectomy may be performed on an endangered animal under limited circumstances, particularly if an individual has already produced many offspring and its genes are overrepresented in the population, scientists realized the animal in question was one of the most genetically valuable Przewalski’s horses in the North American breeding program. The first birth by artificial insemination occurred on July 27, 2013, at the Smithsonian Conservation Biology Institute.
Le Villaret, located in the Cevennes National Park in southern France and run by the Association Takh, is a breeding site for Przewalski’s horses that was created to allow the free expression of natural Przewalski’s horse behaviors. Eleven zoo-born horses were brought to Le Villaret in 1993. Horses born there are adapted to life in the wild: they are free to choose their own mates and must forage on their own. Such a unique breeding site was necessary to produce the individuals that were reintroduced to Mongolia in 2004 and 2005. In 2012 there were 39 individuals at Le Villaret.
The Przewalski’s Horse Reintroduction Project of China was initiated in 1985 when 11 wild horses were imported from overseas. After more than two decades of effort, the Xinjiang Wild Horse Breeding Centre has bred a large number of the horses, of which 55 were released into the Kalamely Mountain area. The animals quickly adapted to their new environment. In 1988, six foals were born and survived, and by 2001 there were over 100 horses at the centre. As of 2013, the center hosted 127 horses divided into 13 breeding herds and three bachelor herds.
Reintroductions organized by western European countries started in 1990s. These were later stopped, mostly for financial reasons. Prague Zoo started a new cycle of transporting horses to the wild, which, with the support of public and many strategic partners, continues today.
Learn More About Przewalski’s Horse
There are only about 2,000 Przewalski horses left in the world, but in October six endangered members of this species arrived in Russia. Scientists hope to restore them in the …
Przewalski’s horses are the last surviving subspecies of wild horse. First described scientifically in the late 19th century by Russian explorer N. M. Przewalski, for whom the horse is named, …
In 1880, Russian explorer Nikolai Przewalski encountered a small population of wild horses while traversing central Asia. The horses were compact, with heavy limbs and strong necks. They had dun …
The first thing you should know about Przewalski’s horse is how to say it. Przewalski is a Polish word, and it belongs to Nikolai Przhevalsky. But we’re getting ahead of …
An animal reserve in Kent in Britain has welcomed a newborn Przewalski’s horse foal to its herd. The filly foal was born at , one of Kent’s most popular visitor …
Przewalski’s horses are the only breed which was never domesticated. They were once common across Russia’s and Mongolia’s steppes, but were slowly hunted down. Now, coming back from the brink …
The Grévy’s zebra (Equus grevyi), also known as the imperial zebra, is the largest extant wild equid and the largest and most threatened of the three species of zebra, the other two being the plains zebra and the mountain zebra. Named after Jules Grévy, it is the sole extant member of the subgenus Dolichohippus. The Grévy’s zebra is found in Kenya and Ethiopia. Compared with other zebras, it is tall, has large ears, and its stripes are narrower.
The Grévy’s zebra lives in semi-arid grasslands where it feeds on grasses, legumes, and browse; it can survive up to five days without water. It differs from the other zebra species in that it does not live in harems and has few long-lasting social bonds. Male territoriality and mother–foal relationships form the basis of the social system of the Grévy’s zebra. This zebra is considered to be endangered. Its population has declined from 15,000 to 3,000 since the 1970s. However, as of 2008, the population is stable.
Taxonomy and Naming
The Grévy’s zebra was first described by French naturalist Émile Oustalet in 1882. He named it after Jules Grévy, then president of France, who, in the 1880s, was given one by the government of Abyssinia. Traditionally, this species was classified in the subgenus Dolichohippus with plains zebra and mountain zebra in Hippotigris.
Fossils of zebra-like equids have been found throughout Africa and Asia in the Pliocene and Pleistocene deposits. Notable examples include E. sanmeniensis from China, E. cautleyi from India, E. valeriani from central Asia, and E. oldowayensis from East Africa. The latter, in particular, is very similar to the Grévy’s zebra and may have been its ancestor.
The Grévy’s zebra is the largest of all wild equines. It is 2.5–2.75 m (8.2–9.0 ft) from head to tail with a 55–75 cm (22–30 in) tail, and stands 1.45–1.6 m (4.8–5.2 ft) high at the shoulder. These zebras weigh 350–450 kg (770–990 lb). Grévy’s zebra differs from the other two zebras in its more primitive characteristics. It is particularly mule-like in appearance; the head is large, long, and narrow with elongated nostril openings; the ears are very large, rounded, and conical and the neck is short but thick. The zebra’s muzzle is ash-grey to black in colour with the lips having whiskers. The mane is tall and erect; juveniles have a mane that extends to the length of the back and shortens as they reach adulthood.
As with all zebra species, the Grevy’s zebra’s pelage has a black and white striping pattern. The stripes are narrow and close-set, being broader on the neck, and they extend to the hooves. The belly and the area around the base of the tail lack stripes which is unique to the Grevy’s zebra. Foals are born with brown and white striping, with the brown stripes darkening as they grow older. Embryological evidence has shown that the zebra’s background colour is dark and the white is an addition. The stripes of the zebra may serve to make it look bigger than it actually is or disrupt its outline. It appears that a stationary zebra can be inconspicuous at night or in shade. Experiments have suggested that the stripes polarize light in such a way that it discourages biting horse-flies in a manner not shown with other coat patterns. Other studies suggest that, when moving, the stripes may confuse observers, such as mammalian predators and biting insects, via two visual illusions, the wagon wheel effect, where the perceived motion is inverted, and the barber pole illusion, where the perceived motion is in a wrong direction.
The Grévy’s zebra largely inhabits northern Kenya, with some isolated populations in Ethiopia. It was extirpated from Somalia and Djibouti and its status in South Sudan is uncertain. It lives in Acacia-Commiphora bushlands and barren plains. Ecologically, this species is intermediate between the arid-living African wild ass and the water-dependent plains zebra. Lactating females and non-territorial males use areas with green, short grass and medium, dense bush more often than non-lactating females and territorial males.
Grévy’s zebras rely on grasses, legumes, and browse for nutrition. They commonly browse when grasses are not plentiful. Their hindgut fermentation digestive system allows them to subsist on diets of lower nutritional quality than that necessary for ruminant herbivores. Grevy’s zebras can survive up to five days without water, but will drink daily when it is plentiful. They often migrate to better watered highlands during the dry season. Females require significantly more water when they are lactating. During droughts, the zebras will dig water holes and defend them. Grévy’s zebras are preyed on by lions, hyenas, wild dogs, cheetahs and leopards. In addition, they are susceptible to various gastro-intestinal parasites, notably of the Trichostrongylus genus.
Adult males mostly live in territories during the wet seasons, but some may stay in them year-ound if there’s enough water left. Stallions that are unable to establish territories are free-ranging and are known as bachelors. Females, young and non-territorial males wander through large home ranges. The females will wander from territory to territory preferring the ones with the highest-quality food and water sources. Up to nine males may compete for a female outside of a territory.
Territorial stallions will tolerate other stallions who wander in their territory; however, when an oestrous female is present, the territorial stallion keeps other males at bay. Non-territorial males may avoid territorial ones because of harassment. When females are not around, a territorial stallion will seek the company of other stallions. The stallion shows his dominance with an arched neck and a high-stepping gait and the least dominant stallions submit by extending their tail, lowering their heads and nuzzling their superior’s chest or groin. The call of the Grévy’s zebra has been described as “something like a hippo’s grunt combined with a donkey’s wheeze”. To get rid of flies or parasites, they roll in dust, water or mud or, in the case of flies, twitch their skin. They also rub against trees, rocks and other objects to get rid of irritations like itchy skin, hair or parasites. Although Grévy’s zebras do not perform mutual grooming, they do sometimes rub against a conspecific.
Grévy’s zebras can mate and give birth year-round, but most mating takes place in the early rainy seasons and births mostly take place in August or September after the long rains. An oestrous mare may visit though as many as four territories a day and will mate with the stallions in them. Among territorial stallions, the most dominant ones control territories near water sources, which mostly attract mares with dependant foals, while more subordinate stallions control territories away from water with greater amounts of vegetation, which mostly attract mares without dependant foals.
The resident stallions of territories will try to subdue the entering mares with dominance rituals and then continue with courtship and copulation. Grévy’s zebra stallions have large testicles and can ejaculate a large amount of semen to replace the sperm of other males. This is a useful adaptation for a species whose females mate polyandrously. Bachelors or outside territorial stallions sometimes “sneak” copulation of mares in another stallion’s territory. While female associations with individual males are brief and mating is promiscuous, females who have just given birth will reside with one male for long periods and mate exclusively with that male. Lactating females are harassed by males more often than non-lactating ones and thus associating with one male and his territory provides an advantage as he will guard against other males.
Gestation of the Grévy’s zebra normally lasts 390 days, with a single foal being born. A newborn zebra will follow anything that moves, so new mothers prevent other mares from approaching their foals while imprinting their own striping pattern, scent and vocalisation on them. Females with young foals may gather into small groups. Mares may leave their foals in “kindergartens” while searching for water. The foals will not hide, so they can be vulnerable to predators. However, kindergartens tend to be protected by an adult, usually a territorial male. A female with a foal stays with one dominant territorial male who has exclusive mating rights to her. While the foal will not likely be his, the stallion will look after it to ensure that the female stays in his territory. To adapt to a semi-arid environment, Grévy’s zebra foals have longer nursing intervals and wait until they are three months old before they start drinking water. Although offspring became less dependant on their mothers after half a year, associations with them continue for up to three years.
The Grévy’s zebra was known to the Europeans in antiquity and was used by the Romans in circuses. It was subsequently forgotten in the Western world for a thousand years. In the seventeenth century, the king of Shoa (now central Ethiopia) exported two zebras; one to the Sultan of Turkey and another to the Dutch governor of Jakarta. A century later, in 1882, the government of Abyssinia sent one to French president Jules Grévy. It was at that time that the animal was recognised as its own species and named in Grévy’s honor.
Status and Conservation
The Grévy’s zebra is considered endangered. Its population was estimated to be 15,000 in the 1970s and by the early 21st century the population was lower than 3,500, a 75% decline. It is estimated that there are less than 2,500 Grévy’s zebras still living in the wild. There are also an estimated 600 Grévy’s zebras in captivity. Captive herds have been known to thrive, like at White Oak Conservation in Yulee, Florida, United States, where more than 70 foals have been born. There, research is underway in partnership with the Conservation Centers for Species Survival on semen collection and freezing and on artificial insemination. The Grévy’s zebra population trend is considered stable as of 2008.
The Grévy’s zebra is legally protected in Ethiopia. In Kenya, it is protected by the hunting ban of 1977. In the past, Grévy’s zebras were threatened mainly by hunting for their skins which fetched a high price on the world market. However, hunting has declined and the main threat to the zebra is habitat loss and competition with livestock. Cattle gather around watering holes and the Grévy’s zebras are fenced from those areas. Community-based conservation efforts have shown to the most effective in preserving Grévy’s zebras and their habitat. Less than 0.5% of the range of the Grévy’s zebra is in protected areas. In Ethiopia, the protected areas include Alledeghi Wildlife Reserve, Yabelo Wildlife Sanctuary, Borana Controlled Hunting Area, and Chalbi Sanctuary. In Kenya, important protected areas include the Buffalo Springs, Samburu, and Shaba National Reserves, and the private and community land wildlife conservancies in Isiolo, Samburu, and the Laikipia Plateau.
The Mesquite plant was introduced into Ethiopia around 1997 and is endangering the zebra’s food supply. The Mesquite plant is an invasive species replacing the two grass species, Cenchrus ciliaris and Chrysopogon plumulosus, which the zebra’s eat for most of their food.
Learn More About Zebras
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