Domestic horse

Naming

A truly wild horse is a species or subspecies with no ancestors that were ever domesticated. Therefore, most "wild" horses today are actually feral horses, animals that escaped or were turned loose from domestic herds and the descendants of those animals. Only two never-domesticated subspecies, the Tarpan and the Przewalski's Horse, survived into recorded history and only the latter survives today.

The Przewalski's Horse, named after the Russian explorer Nikolai Przhevalsky, is a rare Asian animal. It is also known as the Mongolian Wild Horse; Mongolian people know it as the "taki", and the Kyrgyz people call it a "kirtag". The subspecies was presumed extinct in the wild between 1969 and 1992, while a small breeding population survived in zoos around the world. In 1992, it was reestablished in the wild due to the conservation efforts of numerous zoos. Today, a small wild breeding population exists in Mongolia. There are additional animals still maintained at zoos throughout the world.

The Tarpan or European Wild Horse was found in Europe and much of Asia. It survived into the historical era, but became extinct in 1909, when the last captive died in a Russian zoo. Thus, the genetic line was lost. Attempts have been made to recreate the Tarpan,...hieroglyph snipped... which resulted in horses with outward physical similarities, but nonetheless descended from domesticated ancestors and not true wild horses.

Periodically, populations of horses in isolated areas are speculated to be relict populations of wild horses, but generally have been proven to be feral or domestic. For example, the Riwoche horse of Tibet was proposed as such, but testing did not reveal genetic differences with domesticated horses. Similarly, the Sorraia of Portugal was proposed as a direct descendant of the Tarpan based on shared characteristics, but genetic studies have shown that the Sorraia is more closely related to other horse breeds and that the outward similarity is an unreliable measure of relatedness.

Distribution

Feral horses are born and live in the wild, but are descended from domesticated animals. Many populations of feral horses exist throughout the world. Studies of feral herds have provided useful insights into the behavior of prehistoric horses, as well as greater understanding of the instincts and behaviors that drive horses that live in domesticated conditions.

There are also semi-feral horses in many parts of the world, such as Dartmoor and the New Forest in the UK, where the animals are all privately owned but live for significant amounts of time in "wild" conditions on undeveloped, often public, lands. Owners of such animals often pay a fee for grazing rights.

Behavior

Specific terms and specialized language are used to describe equine anatomy, different life stages, colors and breeds.Horses are prey animals with a strong fight-or-flight response. Their first reaction to threat is to startle and usually flee, although they will stand their ground and defend themselves when flight is impossible or if their young are threatened. They also tend to be curious; when startled, they will often hesitate an instant to ascertain the cause of their fright, and may not always flee from something that they perceive as non-threatening. Most light horse riding breeds were developed for speed, agility, alertness and endurance; natural qualities that extend from their wild ancestors. However, through selective breeding, some breeds of horses are quite docile, particularly certain draft horses.

Horses are herd animals, with a clear hierarchy of rank, led by a dominant individual, usually a mare. They are also social creatures that are able to form companionship attachments to their own species and to other animals, including humans. They communicate in various ways, including vocalizations such as nickering or whinnying, mutual grooming, and body language. Many horses will become difficult to manage if they are isolated, but with training, horses can learn to accept a human as a companion, and thus be comfortable away from other horses. However, when confined with insufficient companionship, exercise, or stimulation, individuals may develop stable vices, an assortment of bad habits, mostly stereotypies of psychological origin, that include wood chewing, wall kicking, "weaving", and other problems.

Reproduction

Gestation lasts approximately 340 days, with an average range 320–370 days, and usually results in one foal; twins are rare. Horses are a precocial species, and foals are capable of standing and running within a short time following birth. Foals are usually born in the spring. The estrous cycle of a mare occurs roughly every 19–22 days and occurs from early spring into autumn. Most mares enter an "anestrus" period during the winter and thus do not cycle in this period. Foals are generally weaned from their mothers between four and six months of age.

Horses, particularly colts, sometimes are physically capable of reproduction at about 18 months, but domesticated horses are rarely allowed to breed before the age of three, especially females. Horses four years old are considered mature, although the skeleton normally continues to develop until the age of six; maturation also depends on the horse's size, breed, sex, and quality of care. Larger horses have larger bones; therefore, not only do the bones take longer to form bone tissue, but the epiphyseal plates are larger and take longer to convert from cartilage to bone. These plates convert after the other parts of the bones, and are crucial to development.

Depending on maturity, breed, and work expected, horses are usually put under saddle and trained to be ridden between the ages of two and four. Although Thoroughbred race horses are put on the track as young as the age of two in some countries, horses specifically bred for sports such as dressage are generally not put under saddle until they are three or four years old, because their bones and muscles are not solidly developed. For endurance riding competition, horses are not deemed mature enough to compete until they are a full 60 calendar months old.

Evolution

The horse adapted to survive in areas of wide-open terrain with sparse vegetation, surviving in an ecosystem where other large grazing animals, especially ruminants, could not. Horses and other equids are odd-toed ungulates of the order Perissodactyla, a group of mammals that was dominant during the Tertiary period. In the past, this order contained 14 families, but only three—Equidae, the tapir, and the rhinoceros—have survived to the present day.

The earliest known member of the Equidae family was the "Hyracotherium", which lived between 45 and 55 million years ago, during the Eocene period. It had 4 toes on each front foot, and 3 toes on each back foot. The extra toe on the front feet soon disappeared with the "Mesohippus", which lived 32 to 37 million years ago. Over time, the extra side toes shrank in size until they vanished. All that remains of them in modern horses is a set of small vestigial bones on the leg below the knee, known informally as splint bones. Their legs also lengthened as their toes disappeared until they were a hooved animal capable of running at great speed. By about 5 million years ago, the modern "Equus" had evolved. Equid teeth also evolved from browsing on soft, tropical plants to adapt to browsing of drier plant material, then to grazing of tougher plains grasses. Thus proto-horses changed from leaf-eating forest-dwellers to grass-eating inhabitants of semi-arid regions worldwide, including the steppes of Eurasia and the Great Plains of North America.

By about 15,000 years ago, "Equus ferus" was a widespread holarctic species. Horse bones from this time period, the late Pleistocene, are found in Europe, Eurasia, Beringia, and North America. Yet between 10,000 and 7,600 years ago, the horse became extinct in North America and rare elsewhere. The reasons for this extinction are not fully known, but one theory notes that extinction in North America paralleled human arrival. Another theory points to climate change, noting that approximately 12,500 years ago, the grasses characteristic of a steppe ecosystem gave way to shrub tundra, which was covered with unpalatable plants.

Cultural

Modern horses are often used to reenact many of their historical work purposes. Horses are used, complete with equipment that is authentic or a meticulously recreated replica, in various live action historical reenactments of specific periods of history, especially recreations of famous battles. Horses are also used to preserve cultural traditions and for ceremonial purposes. Countries such as the United Kingdom still use horse-drawn carriages to convey royalty and other VIPs to and from certain culturally significant events. Public exhibitions are another example, such as the Budweiser Clydesdales, seen in parades and other public settings, a team of draft horses that pull a beer wagon similar to that used before the invention of the modern motorized truck.

Horses are frequently seen in television, films and literature. They are sometimes featured as a major character in films about particular animals, but also used as visual elements that assure the accuracy of historical stories. Both live horses and iconic images of horses are used in advertising to promote a variety of products. The horse frequently appears in coats of arms in heraldry, in a variety of poses and equipment. The mythologies of many cultures, including Greco-Roman, Hindu, Islamic, and Norse, include references to both normal horses and those with wings or additional limbs, and multiple myths also call upon the horse to draw the chariots of the Moon and Sun. The horse also appears in the 12-year cycle of animals in the Chinese zodiac related to the Chinese calendar.