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The horse (Equus ferus caballus) is a hoofed (ungulate) mammal, a subspecies of one of seven living species of the family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today. Humans began to domesticate horses around 4500 BC, and their domestication is believed to have been widespread by 3000 BC; by 2000 BC the use of domesticated horses had spread throughout the Eurasian continent. Although most horses today are domesticated, there are still endangered populations of the Przewalski's Horse, the only remaining true wild horse, as well as more common feral horses which live in the wild but are descended from domesticated ancestors.
There is an extensive, specialized vocabulary used to describe equine-related concepts, covering everything from anatomy to life stages, size, colors, markings, breeds, locomotion, and behavior. Horses are anatomically designed to use speed to escape predators, and have a well-developed sense of balance and a strong fight-or-flight instinct. Related to this need to flee from predators in the wild is an unusual trait: horses are able to sleep both standing up and lying down. Female horses, called mares, carry their young for approximately 11 months, and a young horse, called a foal, can stand and run shortly following birth. Most domesticated horses begin training under saddle or in harness between the ages of two and four. They reach full adult development by age five, and have an average lifespan of between 25 and 30 years.
Horse breeds are loosely divided into three categories based on general temperament: spirited "hot bloods" with speed and endurance; "cold bloods," such as draft horses and some ponies, suitable for slow, heavy work; and "warmbloods," developed from crosses between hot bloods and cold bloods, often focusing on creating breeds for specific riding purposes, particularly in Europe. There are over 300 breeds of horses in the world today, developed for many different uses.
Horses and humans interact in many ways, not only in a wide variety of sport competitions and non-competitive recreational pursuits, but also in working activities including police work, agriculture, entertainment, assisted learning and therapy. Horses were historically used in warfare. A wide variety of riding and driving techniques have been developed, using many different styles of equipment and methods of control. Many products are derived from horses, including meat, milk, hide, hair, bone, and pharmaceuticals extracted from the urine of pregnant mares. Humans provide domesticated horses with food, water and shelter, as well as attention from specialists such as veterinarians and farriers.
Depending on breed, management and environment, the domestic horse today has a life expectancy of 25 to 30 years. It is uncommon, but a few animals live into their 40s and, occasionally, beyond. The oldest verifiable record was "Old Billy," a 19th-century horse that lived to the age of 62. In modern times, Sugar Puff, who had been listed in the Guinness Book of World Records as the world's oldest living pony, died in 2007, aged 56.
Regardless of a horse's actual birth date, for most competition purposes an animal is considered a year older on January 1 of each year in the northern hemisphere and August 1 in the southern hemisphere. The exception is in endurance riding, where the minimum age to compete is based on the animal's calendar age. A very rough estimate of a horse's age can be made from looking at its teeth.
The following terminology is used to describe horses of various ages:
Foal: a horse of either sex less than one year old. A nursing foal is sometimes called a suckling and a foal that has been weaned is called a weanling. Most domesticated foals are weaned at 5 to 7 months of age, although foals can be weaned at 4 months with no adverse effects.
Yearling: a horse of either sex that is between one and two years old.
Colt: a male horse under the age of four. A common terminology error is to call any young horse a "colt," when the term actually only refers to young male horses.
Filly: a female horse under the age of four.
Mare: a female horse four years old and older.
Stallion: a non-castrated male horse four years old and older. Some people, particularly in the UK, refer to a stallion as a "horse".
A ridgling or "rig" is a male horse which has an undescended testicle or is improperly castrated. If both testicles are not descended, the horse may appear to be a gelding, but will still behave like a stallion.
Gelding: a castrated male horse of any age, though for convenience sake, many people also refer to a young gelding under the age of four as a "colt".
In horse racing, the definitions of colt, filly, mare, and stallion may differ from those given above. In the UK, Thoroughbred horse racing defines a colt as a male less than five years old, and a filly as a female less than five years old. In the USA, both Thoroughbred racing and harness racing defines colts and fillies as four years old and younger.
The English-speaking world measures the height of horses in hands, abbreviated "h" or "hh," for "hands high," measured at the highest point of an animal's withers, where the neck meets the back, chosen as a stable point of the anatomy, unlike the head or neck, which move up and down; one hand is 4 inches (10 cm). Intermediate heights are defined by hands and inches, rounding to the lower measurement in hands, followed by a decimal point and the number of additional inches between 1 and 3. Thus a horse described as "15.2 h," is 15 hands, 2 inches (62 in/160 cm) in height. The size of horses varies by breed, but can also be influenced by nutrition.
Size varies greatly among horse breeds, as with this full-sized horse and a miniature horse.The general rule for cutoff in height between what is considered a horse and a pony at maturity is 14.2 hands (58 in/150 cm). An animal 14.2 h or over is usually considered to be a horse and one less than 14.2 h a pony. However, there are exceptions to the general rule. Some breeds which typically produce individuals both under and over 14.2 h are considered horses regardless of their height. Conversely, some pony breeds may have features in common with horses, and individual animals may occasionally mature at over 14.2 h, but are still considered to be ponies.
The distinction between a horse and pony is not simply a difference in height, but takes account of other aspects of phenotype or appearance, such as conformation and temperament. Ponies often exhibit thicker manes, tails and overall coat. They also have proportionally shorter legs, wider barrels, heavier bone, shorter and thicker necks, and short heads with broad foreheads. They often have calmer temperaments than horses and also a high level of equine intelligence that may or may not be used to cooperate with human handlers. In fact, small size, by itself, is sometimes not a factor at all. While the Shetland pony stands on average 10 hands high (40 in/100 cm), the Falabella and other miniature horses, which can be no taller than 30 inches (76 cm), the size of a medium-sized dog, are classified by their respective registries as very small horses rather than as ponies.
Light riding horses such as Arabians, Morgans, or Quarter Horses usually range in height from 14 to 16 hands (56 to 64 in/140 to 160 cm) and can weigh from 850 to 1,200 pounds (390 to 540 kg). Larger riding horses such as Thoroughbreds, American Saddlebreds or Warmbloods usually start at about 15.2 hands (62 in/160 cm) and often are as tall as 17 hands (68 in/170 cm), weighing from 1,100 to 1,500 pounds (500 to 680 kg). Heavy or draft horses such as the Clydesdale, Belgian, Percheron, and Shire are usually at least 16 to 18 hands (64 to 72 in/160 to 180 cm) high and can weigh from about 1,500 to 2,000 pounds (680 to 910 kg).
The largest horse in recorded history was probably a Shire horse named Sampson, who lived during the late 1800s. He stood 21.2½ hands high (86.5 in/220 cm), and his peak weight was estimated at 3,360 pounds (1,520 kg). The current record holder for the world's smallest horse is Thumbelina, a fully mature miniature horse affected by dwarfism. She is 17 inches (43 cm) tall and weighs 60 pounds (27 kg).
Main articles: Equine coat color, Equine coat color genetics, and Horse markings
Bay (left) and chestnut (sometimes called "sorrel") are two of the most common coat colors, seen in almost all breeds.Horses exhibit a diverse array of coat colors and distinctive markings, described with a specialized vocabulary. Often, a horse is classified first by its coat color, before breed or sex. Flashy or unusual colors are sometimes very popular, as are horses with particularly attractive markings. Horses of the same color may be distinguished from one another by their markings.
The genetics that create many horse coat colors have been identified, although research continues on specific genes and mutations that result in specific color traits. Essentially, all horse colors begin with a genetic base of "red" (chestnut) or "black," with the addition of alleles for spotting, graying, suppression or dilution of color, or other effects acting upon the base colors to create the dozens of possible coat colors found in horses.
Horses which are light in color are often misnamed as being "white" horses. A horse that looks pure white is, in most cases, actually a middle-aged or older gray. Grays have black skin underneath their white hair coat (with the exception of small amounts of pink skin under white markings). The only horses properly called white are those with pink skin under a white hair coat, a fairly rare occurrence. There are no truly albino horses, with pink skin and red eyes, as albinism is a lethal condition in horses.
Main articles: List of horse breeds, Horse breeding, and Selective breeding
Horse breeds are groups of horses with distinctive characteristics that are transmitted consistently to their offspring, such as conformation, color, performance ability, or disposition. These inherited traits are usually the result of a combination of natural crosses and artificial selection methods aimed at producing horses for specific tasks. Certain breeds are known for certain talents. For example, Standardbreds are known for their speed in harness racing. Some breeds have been developed through centuries of crossings with other breeds, while others, such as Tennessee Walking Horses and Morgans, developed from a single sire from which all current breed members descend. There are more than 300 horse breeds in the world today.
See also: Domestication of the horse
Modern horse breeds developed in response to a need for "form to function", the necessity to develop certain physical characteristics in order to perform a certain type of work. Thus, powerful but refined breeds such as the Andalusian or the Lusitano developed in the Iberian peninsula as riding horses that also had a great aptitude for dressage, while heavy draft horses such as the Clydesdale and the Shire developed out of a need to perform demanding farm work and pull heavy wagons. Ponies of all breeds originally developed mainly from the need for a working animal that could fulfill specific local draft and transportation needs while surviving in harsh environments. However, by the 20th century, many pony breeds had Arabian and other blood added to make a more refined pony suitable for riding. Other horse breeds developed specifically for light agricultural work, heavy and light carriage and road work, various equestrian disciplines, or simply as pets.
Purebreds and registries
Main articles: Breed registry and Purebred
Horses have been selectively bred since their domestication. Today, there are over 300 breeds of horses in the world. However, the concept of purebred bloodstock and a controlled, written breed registry only became of significant importance in modern times. Today, the standards for defining and registration of different breeds vary. Sometimes purebred horses are called Thoroughbreds, which is incorrect; "Thoroughbred" is a specific breed of horse, while a "purebred" is a horse (or any other animal) with a defined pedigree recognized by a breed registry.
An early example of people who practiced selective horse breeding were the Bedouin, who had a reputation for careful breeding practices, keeping extensive pedigrees of their Arabian horses and placing great value upon pure bloodlines. Though these pedigrees were originally transmitted via an oral tradition, written pedigrees of Arabian horses can be found that date to the 14th century. In the same period of the early Renaissance, the Carthusian monks of southern Spain bred horses and kept meticulous pedigrees of the best bloodstock; the lineage survives to this day in the Andalusian horse. One of the earliest formal registries was General Stud Book for Thoroughbreds, which began in 1791 and traced back to the Arabian stallions imported to England from the Middle East that became the foundation stallions for the breed.
Some breed registries have a closed stud book, where registration is based on pedigree, and no outside animals can gain admittance. For example, a registered Thoroughbred or Arabian must have two registered parents of the same breed. Other breeds have a partially closed stud book but still allow certain infusions from other breeds. For example, the modern Appaloosa must have at least one Appaloosa parent, but may also have a Quarter Horse, Thoroughbred, or Arabian parent so long as the offspring exhibits appropriate color characteristics. The Quarter Horse normally requires both parents to be registered Quarter Horses, but allows "Appendix" registration of horses with one Thoroughbred parent, and the horse may earn its way to full registration by completing certain performance requirements.
Others, such as most of the warmblood breeds used in sport horse disciplines, have open stud books to varying degrees. While pedigree is considered, outside bloodlines are admitted to the registry if the horses meet the set standard for the registry. These registries usually require a studbook selection process involving judging of an individual animal's quality, performance, and conformation before registration is finalized. A few "registries," particularly some color breed registries, are very open and will allow membership of all horses that meet limited criteria, such as coat color and species, regardless of pedigree or conformation.
Breed registries also differ as to their acceptance or rejection of breeding technology. For example, all Jockey Club Thoroughbred registries require that a registered Thoroughbred be a product of a natural mating, so called "live cover". A foal born of two Thoroughbred parents, but by means of artificial insemination or embryo transfer, cannot be registered in the Thoroughbred studbook. On the other hand, since the advent of DNA testing to verify parentage, most breed registries now allow artificial insemination (AI), embryo transfer (ET), or both. The high value of stallions has helped with the acceptance of these techniques because they allow a stallion to breed more mares with each "collection," and greatly reduce the risk of injury during mating. Cloning of horses is highly controversial, and at the present time most mainstream breed registries will not accept cloned horses, though several cloned horses and mules have been produced.
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