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Domestic Horse
Conservation status
Template:StatusDomesticated
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Equidae
Genus:	Equus
Species:	E. caballus
Binomial name
Equus caballus Linnaeus, 1758
Synonyms
Equus ferus caballus (see text) Equus laurentius

The horse (Equus caballus) is a large odd-toed ungulate mammal, one of ten modern species of the family Equidae.

Horses have long been among the most economically important domesticated animals; however their importance has declined with the introduction of mechanization. The horse is a prominent figure in the ideals of religion, mythology, and art, as well as playing an important role in transportation, agriculture, and warfare. Horses also serve as a source of food, fuel, and clothing.

Most breeds of horses are able to perform work such as carrying humans on their backs or be harnessed to pull objects such as carts or plows. However, horse breeds were developed to allow horses to be specialized for certain tasks; lighter horses for racing or riding, heavier horses for farming and other tasks requiring pulling power. Some horses, such as the miniature horse, can be kept as pets. In some societies, horses are a source of food, both meat and milk; in others it is taboo to consume them. In industrialized countries, horses are predominantly kept for leisure and sporting pursuits, while in other parts of the world they are used as working animals.

Because horses and humans have lived and worked together for thousands of years, an extensive specialized vocabulary has arisen to describe virtually every horse behavioral and anatomical characteristic with a high degree of precision.

Biology

Horse anatomy is described by a large number of horse specific terms, as illustrated by the chart to the right. Specific terms also describe horses of various ages, colors and breeds.

Age

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 horses live into their 40s, and, occasionally, beyond. The oldest verifiable record was "Old Billy," a horse that lived in the 19th century 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 then-living pony, died at age 56.

Regardless of a horse's actual birthdate, for most competition purposes, horses are considered a year older on January 1 of each year in the northern hemisphere and August 1 in the southern hemisphere. The exception is endurance riding, where the minimum age to compete is based on the horse's actual calendar age.

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 4-6 months of age.
• Yearling: a horse of either sex that is between one and two years old.
• Colt: a male horse under the age of four.
• 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 stallion which has an undescended testicle. 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 or horse may differ from those given above. In the United Kingdom, Thoroughbred horse racing defines a colt as a male horse less than five years old and a filly as a female horse less than five years old. In the USA, both Thoroughbred racing and harness racing defines colts and fillies as four years old and younger.

A very rough estimate of a horse's age can be made from looking at its teeth.

Size

The English-speaking world measures the height of horses in hands, abbreviated "h" or "hh," and is measured at the highest point of an animal's withers. One hand is 4 Imperial inches, or, as defined in British law, 101.6 mm. 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 hh tall, means it is 15 hands, 2 inches, or 62 inches/1.57 m in height.

The size of horses varies by breed, but can also be influenced by nutrition. The general rule for cutoff in height between what is considered a horse and a pony at maturity is 14.2 hands high. (abbreviated "h" or "hh") (147 cm, 58 inches) as measured at the withers. An animal 14.2h or over is usually considered a horse and one less than 14.2h is a pony.

However, there are exceptions to the general rule. Some smaller horse breeds who typically produce individual horses both under and over 14.2h are considered "horses" regardless of height. Likewise, some pony breeds, such as the Pony of the Americas or the Welsh pony, share some features of horses and individual animals may occasionally mature at over 14.2h, but are still considered ponies.

The difference between a horse and pony is not simply a height difference, but also a difference in phenotype or appearance. There are noticeable differences in 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.

Light riding horses such as Arabians, Morgans, or Quarter Horses usually range in height from 14.0 (142 cm) to 16.0 hands (163 cm) and can weigh from 386 kilograms to about 540 kg (850 to 1200 lb). Larger riding horses such as Thoroughbreds, American Saddlebreds or Warmbloods usually start at about 15.2 hands (157 cm) and often are as tall as 17 hands (172 cm), weighing from 500 kg to 680 kg (1100 lb to 1500 lb). Heavy or draft horses such as the Clydesdale, Belgian, Percheron, and Shire are usually at least 16.0 (163 cm) to 18.0 hands (183 cm) high and can weigh from about 680 kg up to about 900 kg (1500 lb to 2000 lb). Ponies cannot be taller than 14.2h (147 cm), but can be much smaller, down to the Shetland pony at around 10 hands (102 cm), and the Falabella which can be the size of a medium-sized dog. However, while many miniature horse breeds are small as or smaller than a shetland pony, because they are bred to have a horse phenotype (appearance), their breeders and registries classify them as very small horses rather than ponies.

The largest horse in history was a Shire horse named Sampson, later renamed Mammoth, foaled in 1846 in Bedfordshire, England. He stood 21.2½ hands high (i.e. 7 ft 2½ in or 2.20 m ), and his peak weight was estimated at over 3,300 lb (approx 1.5 tonnes). The current record holder for the world's smallest horse is Thumbelina, a fully mature miniature horse affected by dwarfism. She is 17 inches tall and weighs 60 pounds.

Colors and markings

Horses exhibit a diverse array of coat colors and distinctive markings, and a specialized vocabulary has evolved to describe them. Often, one will refer to a horse in the field by its coat color first rather than by breed or by sex. In spite of the adage that "a good horse is never a bad color," flashy or unusual colors are sometimes very popular, as are horses with particularly attractive markings, such as white on all four legs. Horses of the same color may be distinguished from one another by their markings.

The genetics of horse coat colors has largely been mapped, although discussion continues about some details, particularly those regarding markings, shade variations within a color family and what creates certain variations in shading on a single horse. Essentially, all horse colors begin with a genetic base of "red" (chestnut) or "black," with the addition of alleles for suppression of color, dilution of color, spotting, graying, or other effects acting upon the base colors in various combinations and varying degrees of dominance or recessivity that create the dozens of possible shades of horses.

Reproduction and development

Pregnancy lasts for approximately 335-340 days and usually results in one foal (male: colt, female: filly). Twins are rare. Colts are usually carried 2-7 days longer than fillies. Females 4 years and over are called mares and males are stallions. A castrated male is a gelding. Horses, particularly colts, may sometimes be physically capable of reproduction at approximately 18 months but in practice are rarely allowed to breed until a minimum age of 3 years, especially females. Horses four years old are considered mature, though the skeleton usually finishes developing at the age of six, and the precise time of completion of development also depends on the horse's size (therefore a connection to breed exists), gender, and the quality of care provided by its owner. Also, if the horse is larger, its bones are larger; therefore, not only do the bones take longer to actually form bone tissue (bones are made of cartilage in earlier stages of bone formation), but the epiphyseal plates (plates that fuse a bone into one piece by connecting the bone shaft to the bone ends) are also larger and take longer to convert from cartilage to bone as well. These plates convert after the other parts of the bones do but are crucial to development.

Depending on maturity, breed and the tasks expected, young horses are usually put under saddle and trained to be ridden between the ages of two and four. Although Thoroughbred and American Quarter Horse race horses are put on the track at as young as two years old in some countries (notably the United States), horses specifically bred for sports such as show jumping and dressage are generally not entered into top-level competition until a minimum age of four years old, because their bones and muscles are not solidly developed, nor is their advanced training complete. For endurance riding competition, horses may not compete until they are a full 60 calendar months (5 years) old.

Anatomy

Skeletal system

Horses have, on average, a skeleton of 205 bones. A significant difference in the bones contained in the horse skeleton, as compared to that of a human, is the lack of a collarbone--their front limb system is attached to the spinal column by a powerful set of muscles, tendons and ligaments that attach the shoulder blade to the torso. The horse's legs and hooves are also unique, interesting structures. Their leg bones are proportioned differently from those of a human. For example, the body part that is called a horse's "knee" is actually the carpal bones that correspond to the human wrist. Similarly, the hock, contains the bones equivalent to those in the human ankle and heel. The lower leg bones of a horse correspond to the bones of the human hand or foot, and the fetlock (incorrectly called the "ankle") is actually the proximal sesamoid bones between the cannon bones (a single equivalent to the human metacarpal or metatarsal bones) and the proximal phalanges, located where one finds the "knuckles" of a human. A horse also has no muscles in its legs below the knees and hocks, only skin and hair, bone, tendons, ligaments, cartilage, and the assorted specialized tissues that make up the hoof (see section hooves, below).

Digestion

A horse is a herbivore with a digestive system adapted to a forage diet of grasses and other plant material, consumed regularly throughout the day, and so they have a relatively small stomach but very long intestines to facilitate a steady flow of nutrients. A 1000 pound horse will eat between 15 and 25 pounds (approximately 7-11 kg) of food per day and, under normal use, drink 10 to 12 gallons (about 38-45 litres) of water. Horses are not ruminants, so they have only one stomach, like humans, but unlike humans, they can also digest cellulose from grasses due to the presence of a "hind gut" called the cecum, or "water gut," that food goes through before reaching the large intestine. Unlike humans, horses cannot vomit, so digestion problems can quickly spell trouble, with colic a leading cause of death.

Teeth

Horses are adapted to grazing. In an adult horse, there are 12 incisors (six upper and six lower), adapted to biting off the grass or other vegetation, at the front of the mouth. There are 24 teeth adapted for chewing, the premolars and molars, at the back of the mouth. Stallions and geldings have four additional teeth just behind the incisors, a type of canine teeth that are called "tushes." Some horses, both male and female, will also develop one to four very small vestigial teeth in front of the molars, known as "wolf" teeth, which are generally removed because they can interfere with the bit.

There is an empty interdental space between the incisors and the molars where the bit rests directly on the bars (gums) of the horse's mouth when the horse is bridled.

The incisors show a distinct wear and growth pattern as the horse ages, as well as change in the angle at which the chewing surfaces meet. The teeth continue to erupt throughout life as they are worn down by grazing, and while the diet and veterinary care of the horse can affect the rate of tooth wear, a very rough estimate of the age of a horse can be made by looking at its teeth.

Hooves

The critical importance of the feet and legs is summed up by the traditional adage, "no foot, no horse." The horse hoof begins with the distal phalanges, the equivalent of the human fingertip or tip of the toe, surrounded by cartilage and other specialized, blood-rich soft tissues such as the laminae, with the exterior hoof wall and horn of the sole made essentially of the same material as a human fingernail. The end result is that a horse, weighing on average 1,000 pounds, travels on the same bones as a human on tiptoe. For the protection of the hoof under certain conditions, some horses have horseshoes placed on their feet by a professional farrier. The hoof continually grows, just like a large fingernail, and needs to be trimmed (and horseshoes reset, if used) every six to eight weeks.

Senses

The senses of a horse are generally superior to those of a human. As prey animals, they must be aware of their surroundings at all times. They have very large eyes (among land animals only the ostrich has a larger eye), with excellent day and night vision, though they may have a limited range of color vision. The side positioning of the eyes gives the horse a wide field of vision of about 350°. While not color-blind, studies indicate that they have difficulty distinguishing greens, browns and grays. Their hearing is good, and the pinna of their ears can rotate a full 360 degrees in order to pick up sound from any direction. Their sense of smell, while much better than that of humans, is not their strongest asset; they rely to a greater extent on vision.

A horse's sense of balance is outstanding; the cerebellum of their brain is highly developed and they are very aware of terrain and placement of their feet. Horses' sense of touch is better developed than many people think; they immediately notice when a fly or mosquito lands on them, even before the insect attempts to bite. Their sense of taste is well-developed in order to determine the nature of the plants they are eating, and their prehensile lips can easily sort even the smallest grains. Horses will seldom eat most poisonous plants or spoiled food unless they have no other choices, although a few toxic plants have a chemical structure that appeals to animals, and thus poses a greater risk of being ingested.

Gaits

All horses move naturally with four basic gaits: the walk, trot or jog, canter or lope, and gallop.

Besides these basic gaits, some horses pace, instead of trot. In addition, there are many "ambling" gaits such as the slow gait, rack, fox trot running walk, and tölt. These special gaits are often found in specific breeds, often referred to as "gaited" horses because they naturally possess additional gaits that are approximately the same speed as the trot but smoother to ride. Technically speaking, "gaited horses" replace the standard trot (which is a 2 beat gait) with one of the four beat gaits.

Horse breeds with additional gaits that often occur naturally include: the Tennessee Walking Horse which naturally performs a running walk; the American Saddlebred which can be trained to exhibit a slow gait and the rack; Paso Fino, which has two ambling gaits, the paso corto and paso largo; the Peruvian Paso, which exhibits the paso llano, and sobreandando; and Icelandic horses which are known for the tölt. The fox trot is found in several breeds, most notably the Missouri Foxtrotter. Standardbreds, depending on bloodlines and training, may either pace or trot.

Behavior

Horses are prey animals with a well-developed fight-or-flight instinct. Their first response to threat is to startle and usually flee, although they are known to stand their ground and defend themselves or their offspring in cases where flight is not possible, or when 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. Through selective breeding, some breeds of horses are quite docile, particularly certain large draft horses. However, most light horse riding breeds were developed for speed, agility, alertness and endurance; natural qualities that extend from their wild ancestors.

Horses are herd animals, with a clear hierarchy of rank, led by a dominant animal (usually a mare). Horses are also social creatures who 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. When this behavior occurs while being handled by human, the horse is called "herd-bound". However, through proper training, it is possible to teach any horse to accept a human as a type of companion, and thus be comfortable away from other horses.

When confined with insufficient companionship, exercise or stimulation, horses may develop stable vices, an assortment of bad habits, mostly psychological in origin, that include wood chewing, wall kicking, "weaving" (rocking back and forth) and other problems.

Sleep patterns

Horses are able to sleep both standing up and lying down. They are able to doze and enter light sleep while standing, an adaptation from life as a prey animal in the wild. Lying down makes an animal more vulnerable to predators. Horses are able to sleep standing up because a "stay apparatus" in their legs allows them to relax their muscles and doze without collapsing.

Unlike humans, horses do not sleep in a solid, unbroken period of time. They obtain sleep by means of many short periods of rest. Horses may spend anywhere from four to fifteen hours a day in standing rest, and from a few minutes to several hours lying down. Total sleep time in a day may range from several minutes to a couple of hours. Horses require approximately two and a half hours of sleep, on average, in a 24-hour period. Most of this sleep occurs in many short intervals of about 15 minutes each.

Horses must lie down to reach REM sleep. They only have to lie down for an hour or two every few days to meet their minimum REM sleep requirements. However, if a horse is never allowed to lie down, after several days it will become sleep-deprived, and in rare cases may suddenly collapse as it involuntarily slips into REM sleep while still standing. This condition differs from narcolepsy, though horses may also suffer from that disorder.

Horses sleep better when in groups because some animals will sleep while others stand guard to watch for predators. A horse kept entirely alone will not sleep well because its instincts are to keep a constant eye out for danger.

Temperament

Horses are mammals, and as such are all "warm-blooded" creatures, as opposed to reptiles, which are cold-blooded. However, these words have developed a separate meaning in the context of equine description, used to describe temperament, not body temperature. For example, the "hot-bloods", such as race horses, exhibit more sensitivity and energy, while the "cold-bloods," such as most draft breeds, are quieter, calmer creatures.

"Hot" bloods

The "hot blooded" breeds have a level of sensitivity and intelligence that enables quick learning with the potential for greater communication and cooperation with their riders. However, their intelligence also allows them to learn bad habits as quickly as good ones. Because of this, they also can quickly lose trust in a poor rider and do not tolerate inept or abusive training practices.

"Oriental" breeds such as the Akhal-Teke, Barb, and Arabian horse and the now-extinct Turkoman horse gained the title of "hot bloods" for their temperament, characterized by sensitivity, keen awareness, athleticism, and energy. European breeders wished to infuse these traits into their best racing and light cavalry horses and thus imported a number of oriental horses into Europe. These traits, combined with the dense but more aesthetically refined bone structure of the oriental-type horse, were used as the foundation of the Thoroughbred breed. Other than the oriental breeds and the Thoroughbred, there are no other breeds given the classification "hot blooded" today.

"Cold" bloods

Muscular and heavy draft horses are known as "cold bloods," as they have been bred, not only for strength, but also to have the calm, steady, patient temperament needed to pull a plow or a heavy carriage full of people. They are sometimes nicknamed "gentle giants" because of their placid dispositions.

There are well over a dozen well-known draft breeds, and many more rarer breeds developed in various regions of the world that were adapted to local conditions. Some breeds are lighter and livelier, developed to pull carriages or to plow large fields in drier climates. Others are slower and more powerful, bred to plow fields with heavy, clay-based soils. One of the most common draft breeds is the Belgian. The largest is the Shire. Clydesdales, with their common coloration of a bay or black coat, with white legs and long-haired, "feathered" fetlocks, are one of the most easily recognized.

Warmbloods

The term "warmblood" has two different meanings today, the more common modern meaning refers to a specific subset of horse breeds, and the other, older meaning refers simply to horses of a moderate temperament. The term "warm blood," up through approximately the 1970s, originally referred to any cross of "cold blooded" draft horses on "hot blooded" Thoroughbreds or Arabians. Examples included breeds such as the Irish Draught horse or the Cleveland Bay, and sometimes also referred to the "Baroque horses" used for classical dressage, such as the Lipizzan or Andalusian. Sometimes the term was even used to refer to breeds of light riding horse other than Thoroughbreds or Arabians, such as the Morgan horse.

But today, the term "warmblood" usually refers to a group of sport horse breeds that have dominated the Olympic Games and World Equestrian Games in Dressage and Show Jumping since the 1950s. The "Warmblood" breeds began when European carriage and war horses were crossed with oriental horses or Thoroughbreds, producing a tall riding horse with more refinement than a draft horse, but greater size and more phlegmatic temperament than a lighter breed. These breeds include the Hanoverian, Oldenburg, Trakehner, Holsteiner, Swedish Warmblood, and Dutch Warmblood.

Breeds

Horses come in a wide range of heights, weights, and body types. Different breeds were developed with a specific "form" adapted to a particular "function" or type of work. For example, in terms of height, the largest members of some draft breeds can top 19 hands (2 metres, 76 inches), while the smallest miniature horses stand as low as 5.2 hands (0.56 metres, 22 inches), not significantly larger than a large dog. But height alone does not dictate function; a 17 hand Thoroughbred has a lean slim body type, weighing around 1,200 pounds, with a "hot" temperament, suitable for horse racing. In contrast, a 17 hand Shire has a heavy body, can weigh 2,000 pounds, has a very mild or "cold" temperament, and is suitable for farm work.

Origin of horse breeds

Different schools of thought exist to explain how this range of size and shape came about. One school, which some refer to as the "Four Foundations", (see Domestication of the horse and surviving wild species, above), suggests that the modern horse evolved from multiple types of early wild pony and horse prototypes, each adapted to a given habitat, and the differences between these types account for some of the differences in type of the modern breeds. A second school - the "Single Foundation" - holds only one type of wild horse underwent domestication, and it diverged in form after domestication through human selective breeding (or in the case of feral horses, through ecological pressures). This question will most likely only be resolved once geneticists have finished evaluating the horse genome, analyzing DNA and mitochondrial DNA to construct family trees.

In either case, modern horse breeds developed in response to the need for "form to function"; that is, the necessity to develop certain physical characteristics necessary to perform a certain type of work. Thus, light, refined horses such as the Arabian horse or the Akhal-Teke developed in dry climates to be fast and with great endurance over long distances, while heavy draft horse such as the Belgian developed out of a need to pull plows and perform other farm work. Ponies of all breeds developed out of a dual need to create mounts suitable for children as well as for work in small places like mine shafts or in areas where there was insufficient forage to support larger draft animals. In between these extremes, horses were bred to be particularly suitable for tasks that included pulling carriages, carrying heavily-armored knights, jumping, racing, herding other animals, and packing supplies.

Purebreds and registries

Selective breeding of horses has occurred as long as humans have domesticated them. However, the concept of purebred bloodstock and a controlled breed registry has only gained wide importance in modern times.

The Bedouin people had a reputation for breeding their prize Arabian mares to only the most worthy stallions, and kept extensive pedigrees of their "asil" (purebred) horses. Though these pedigrees were primarily 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, themselves forbidden to ride, 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, a process that started in 1791, and traced back to the foundation sires for that breed. These sires were Arabians, brought to England from the Middle East.

The modern landscape of breed designation presents a complicated picture. Some breeds have closed studbooks. For example, a registered Thoroughbred or Arabian must have two registered parents of the same breed, and no other criteria for registration apply. Other breeds tolerate limited 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 and must also exhibit spotted coloration to gain full registration. 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. Still other breeds, such as most of the warmblood sport horses, require individual judging of an individual animal's quality and conformation before registration or breeding approval, but also allow outside bloodlines in if the horses meet the standard. A few "registries," particularly some color breed registries, will allow membership of any horse that meets a certain criteria, such as coat color, 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 (live cover in horse parlance). A foal born of two Thoroughbred parents, but by means of artificial insemination or embryo transfer is barred from the Thoroughbred studbook. Any Thoroughbred bred outside of these constraints can, however, become part of the Performance Horse Registry.

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 take away the risk of injury during mating. However, cloning of horses is highly controversial, and at the present time, no mainstream breed registry will accept cloned horses, though several cloned horses and mules have been produced.

Regional specialization

Some countries specialize in breeding horses suitable for particular activities. For example, Australia, the United States, and the Patagonia region of South America are known for breeding horses particularly suitable for working cattle and other livestock. Germany produces many Warmblood breeds that are used for dressage. Ireland is recognized for breeding hunters and jumpers. Spain and Portugal are known for the Iberian horse breeds used in high school dressage and bullfighting. Austria is known worldwide for its Lipizzaner horses, used for dressage and high school work in the famous Spanish Riding School in Vienna. The United Kingdom breeds an array of heavy draft horses and several breeds of hardy ponies. Both the United States and Great Britain are noted for breeding Thoroughbred race horses. Russia takes great pride in breeding harness racing horses, a tradition dating back to the development of the Orlov Trotter in the 18th century.

Horse care

Horses are animals that were evolved to graze. They eat grass or hay, sometimes supplemented with grain. They require a plentiful supply of clean water, a minimum of 10 to 12 gallons per day. Although horses are adapted to live outside, they require shelter from the wind and precipitation, which can range from a simple shed or shelter to an elaborate stable.

Horses require annual vaccinations to protect against various diseases, need routine hoof care by a farrier, and regular dental examinations from a veterinarian or a specialized equine dentist. If horses are kept inside in a barn, they require regular daily exercise for their physical health and mental well-being. When turned outside, they require well-maintained, sturdy fences to be safely contained. Regular grooming is also helpful to help the horse maintain good health of the hair coat and underlying skin.

Evolution

The horse as it is known today adapted by evolution 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 relatively ancient group of browsing and grazing animals that first arose less than 10 million years after the dinosaurs became extinct. In the past, this order contained twelve families, but only three families— Equidae (the horse and related species), the tapir and the rhinoceros—have survived to the present day. The earliest equids known as Hyracotherium developed approximately 54 million years ago, during the Eocene period. One of the first true horse species, it had 4 toes on each front foot, and 3 toes on each back foot. the extra toe on the front feet soon disappeared, and by the Pleistocene era, as the horse adapted to a drier, prairie environment, the 2nd and 4th toes disappeared on all feet, and horses became bigger. These side toes first shrunk in size until they have vanished in modern horses. All that remains are a set of small vestigial bones on either side of the cannon (metacarpal or metatarsal) bone, known informally as splint bones, which are a frequent source of splints, a common injury in the modern horse. Their legs also lengthened as their toes disappeared and until they were a hoofed animal capable of running at great speed.

Over millions of years, equid teeth also evolved from browsing on soft, tropical plants to adapt to browsing of drier plant material, and grazing of tougher plains grasses. Thus the 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. For reasons not fully understood, Equus caballus disappeared from North America around 10,000 years ago, at the end of the last Ice Age.

Domestication and surviving wild species

Competing theories exist as to the time and place of initial domestication. The earliest evidence for the domestication of the horse comes from Central Asia and dates to approximately 4,500 BC. Archaeological finds such as the Sintashta chariot burials provided unequivocal evidence that the horse was definitely domesticated by 2000 BC.

Wild prototypes and modern species

Most "wild" horses today are actually feral horses (see feral horses, below), animals that had domesticated ancestors but were themselves born and live in the wild, often for generations. However, there are also some truly wild horses whose ancestors were never successfully domesticated.

The "Four Foundations" theory

There is a theory that there were four basic "proto" horses that developed with adaptations to their environment prior to domestication. There are competing theories, some arguing that the prototypes were separate species, others suggesting that the prototypes were physically different manifestations of the same species. Either way, the most common theories of historical wild species from which other types are thought to have developed suggests the following base prototypes:

• The "Warmblood" subspecies or "Forest Horse": (Equus ferus silvaticus, also called the Diluvial Horse) thought to have evolved into Equus ferus germanicus, and which may have contributed to the development of the warmblood horses of northern Europe, as well as older "heavy horses" such as the Ardennais
• The "Draft" subspecies: a small, sturdy, heavyset animal with a heavy hair coat, arising in northern Europe, adapted to cold, damp climates, somewhat resembling today's draft horse and even the Shetland pony
• The "Oriental" subspecies: a taller, slim, refined and agile animal arising in western Asia, adapted to hot, dry climates, thought to be the progenitor of the modern Arabian horse and Akhal-Teke
• The "Tarpan" subspecies: dun-colored, sturdy animal, the size of a large pony, adapted to the cold, dry climates of northern Asia, the predecessor to the Tarpan and Przewalski's Horse as well as the domesticated Mongolian horse

Wild species surviving into modern times

The tarpan, Equus ferus ferus, survived into the historical era, but became extinct in 1879. Its genetic line is lost, but its phenotype has been recreated by a "breeding back" process, in which living domesticated horses with primitive features were repeatedly interbred. Thanks to the efforts of the brothers Lutz Heck (director of the Berlin zoo) and Heinz Heck (director of Munich Tierpark Hellabrunn), the resulting Heck horse together with the Konik resembles the tarpan more closely than any other living horse.

Przewalski's Horse (Equus ferus przewalskii), a rare Asian species, is the only true wild horse alive today. Also known as the Mongolian Wild Horse, Mongolians know it as the taki, while the Kyrgyz people call it a kirtag. Small wild breeding populations of this animal, named after the Russian explorer Przewalski, exist in Mongolia. There are also small populations maintained at zoos throughout the world. After a battle against extinction, the Przewalksi's Horse is finally flourishing in the wild once again.

Other truly wild equids alive today include the zebra and the onager.

Feral horses

Feral animals, who had domesticated ancestors but were born and live in the wild, are distinct from wild animals, whose ancestors have never undergone domestication. Several populations of feral horses exist, including those in the western United States and Canada (often called "mustangs"), and in parts of Australia ("brumbies") and New Zealand ("Kaimanawa horses"). Isolated feral populations are often named for their geographic location: Namibia has its Namib Desert Horses; the Sorraia lives in Spain and Portugal; Sable Island Horses reside in Nova Scotia, Canada; and New Forest ponies have been part of Hampshire, England for a thousand years.

Studies of feral horses have provided useful insights into the behavior of ancestral wild horses, as well as greater understanding of the instincts and behaviours that drive horses.

Other modern equids

Other members of the horse family include zebras, donkeys, and onagers. The Donkey, Burro or Domestic Ass, Equus asinus, like the horse, has many breeds. A mule is a hybrid of a male ass (jack) and a mare, and is usually infertile. A hinny is the less common hybrid of a female ass (jenny) and a stallion. Breeders have also tried crossing various species of zebra with mares or female asses to produce "zebra mules" (zorses, and zonkeys (also called zedonks or zebroids)). This will probably remain a novelty hybrid as these individuals tend to inherit some of the undomesticated nature of their zebra parent, but they may inherit the zebra's resistance to nagana pest.

Horses within the human economy

Around the world, horses play a role within human economies. Horses can be used for leisure activities, sports, and working purposes. To cite one example, the American Horse Council estimates that horse-related activities have a direct impact on the economy of the United States of over $39 billion, and when indirect spending is considered, the impact is over $102 billion.

In wealthier First World industrialized economies, horses are primarily used in recreational pursuits and competitive sports, though they also have practical uses in police work, cattle ranching, search and rescue, and other duties where terrain or conditions preclude use of motorized vehicles. In poorer Third World economies, they may also be used for recreational purposes by the elite population, but may serve a much wider role in working pursuits including farming, ranching and as a means of transportation. To a very limited extent, they are also still used in warfare, particularly in regions of extremely rugged terrain.

Sport

Horses are trained to be ridden or driven in many different sporting events and competitions. Examples include horse shows, gymkhana and O-Mok-See, rodeos, endurance riding, fox hunting, and Olympic-level events such as three-day eventing, combined driving, dressage, and show jumping. Although scoring varies by event, most emphasize the horse's speed, maneuverability, obedience and/or precision. Sometimes the equitation, the style and ability of the rider, is also considered.

Sports such as polo and horseball do not judge the horse itself, but rather use the horse as a partner for human competitors as a necessary part of the game. Although the horse assists this process and requires specialized training to do so, the details of its performance are not judged, only the result of the rider's actions -- be it getting a ball through a goal or some other achievement. Examples of these sports of partnership between human and animal also include jousting (reenacting the skills used by medieval knights), where the main goal is for one rider to dismount the other, and buzkashi, a team game played throughout Central Asia, the aim being to capture a goat carcass while on horseback.

The most widely known use of horses for sport is horse racing, seen in almost every nation in the world. There are three types: "flat" racing; steeplechasing, i.e. racing over jumps; and harness racing, where horses trot or pace while pulling a driver in a small, light cart known as a sulky. Most race horses in the developed world are Thoroughbreds, a breed which can reach speeds up to 40 mph/70 km/h. In the case of a specialized sprinting breed, the American Quarter Horse, speeds over 50 mph have been clocked. In harness racing, performed by Standardbred horses, speeds over 30 mph have been measured. A major part of the economic importance of horse racing, as for many sports, lies in the gambling associated with it.

Work

There are certain jobs that horses do very well, and no amount of technology appears able to supersede. Mounted police horses are still effective for crowd control. Cattle ranches still require riders on horseback to round up cattle that are scattered across remote, rugged terrain. Search and rescue organizations in some countries depend upon mounted teams to locate people, particularly hikers and hunters, who are lost in remote areas.

Some land management practices such as cultivating and logging can be efficiently performed with horses. In agriculture less use of fossil fuels, reduced soil compaction and degrading of soil structure can be seen over time with the use of draft animals such as horses. In forestry, logging can be done with horses and can result in reduced damage to soil structure and less damage to trees due to more selective logging.

Horses can also be used in other areas where it is necessary to avoid vehicular disruption to delicate soil. Examples include areas such as a nature reserve. They may also be the only form of transport allowed in wilderness areas. They are also quieter than motorized vehicles. Peace officers such as rangers or game wardens may use horses for patrols, and horses may also be used for clearing trails or other work in areas of rough terrain where vehicles are less effective.

In less affluent countries such as Romania, Kyrgyzstan, and many parts of the Third World, horses, donkeys and mules are routinely used for transport and agriculture. In areas where roads are poor or non-existent and fossil fuels are scarce or the terrain rugged, riding horseback is still the most efficient way to get from place to place.

Entertainment and culture

Modern horses are often used to re-enact their historical work purpose. One famous example is the Budweiser Clydesdales. This team of draft horses pull a beer wagon in a manner similar to that used prior to the invention of the modern motorized truck.

Horses are used, complete with equipment that is authentic or a meticulously recreated replica, in various historical reenactments of specific periods of history, and especially famous battles. Popular subjects include American Revolutionary War and Civil War reenactments, as well as battles of the 19th century between the U.S. Cavalry and Native Americans, such as the Battle of the Little Bighorn.

Horses also are used preserve cultural traditions and for ceremonial purposes. Examples include the use of horses at tourist destinations such as Colonial Williamsburg or the presence of cavalry horses at significant funerals of military figures and heads of state. Countries such as the United Kingdom still use horse-drawn carriages to convey royalty and VIPs to and from certain culturally significant events.

Horses are frequently used in television and motion pictures to add authenticity to historical dramas as well as adding charm to films set in modern-day, or even futuristic science fiction settings.

Assisted learning and therapeutic purposes

People with disabilities obtain beneficial results from association with horses. The movement of a horse strengthens muscles throughout a rider's body and promotes better overall health. In many cases, riding has also led to increased mobility for the rider. Horses also provide psychological benefits to people whether they actually ride or not. The benefits of equestrian activity for people with disabilities has also been recognized with the addition of equestrian events to the Paralympic Games and recognition of para-equestrian events by the FEI.

Hippotherapy and therapeutic horseback riding are names for different physical, occupational and speech therapy treatment strategies that utilize equine movement. In the hippotherapy environment, a therapist uses the horse's movement to provide carefully graded sensory input, whereas therapeutic horseback riding uses specific riding skills.

"Equine-assisted" or "equine-facilitated" psychotherapy uses horses as companion animals to assist people with psychological problems. Actual practices vary widely due to the newness of the field; some programs include Therapeutic Horseback Riding and hippotherapy. Non-riding therapies simply encourage a person to touch, speak to and otherwise interact with the horse. People appear to benefit from being able to be around a horse; horses are very sensitive to non-verbal communication and are an ideal resource for working with individuals who have "tuned out" human therapists.

Equine Assisted Learning (EAL), Equine guided education, or equine assisted professional development, is another relatively new field of experiential learning for corporate, professional and personal development. There also have been experimental programs using horses in prison settings. Exposure to horses appears to improve the behavior of inmates in a prison setting and help reduce recidivism when they leave. A correctional facility in Nevada has a successful program where inmates learn to train young mustangs captured off the range in order to make it more likely that these horses will find adoptive homes. Both adult and juvenile prisons in New York, Florida, and Kentucky work in cooperation with the Thoroughbred Retirement Foundation to re-train former racehorses as pleasure mounts and find them new homes. Horses are also used in camps and programs for young people with emotional difficulties.

Warfare

Horses in warfare have been seen for most of recorded history, dating back at least to the 19th century B.C.. While mechanization has largely replaced the horse as a weapon of war, horses are still seen today in limited military uses, mostly for ceremonial purposes, or for reconnaissance and transport activities in areas of rough terrain where motorized vehicles are ineffective. Horses have been used in the 21st century by the Janjaweed militias in the Darfur conflict in attacks against unarmed civilians.

Distribution

The FAO reports that in 2003, China had the largest number of horses in the world with over 8 million horses, followed by Mexico (6,260,000), Brazil (5,900,500), the United States (5,300,000), and Argentina (3,655,000).

Products

• Horse meat has been used as food for animals and humans throughout the ages. It is eaten in many parts of the world and is an export industry in the United States and other countries. Bills have been introduced in both the House and the Senate which would put an end to this practice in the United States. Horse consumption is taboo in some cultures.
• Mare's milk is used by people with large horse-herds, such as the Mongols. They may let it ferment to produce kumis. Mares produce a lower yield of milk than cows, but more than goats and sheep.
• Horse blood was also used as food by the Mongols and other nomadic tribes. The Mongols found this food source especially convenient when riding for long periods of time. Drinking their own horse's blood allowed the Mongols to ride for extended periods of time without stopping to eat.
• Premarin is a mixture of female hormones (estrogens) extracted from the urine of pregnant mares (pregnant mares' urine). It is a widely used drug for hormone replacement therapy. This horse product is very controversial.
• The tail hair of the horse can be used for making bows for stringed instruments such as the violin, viola, cello, and double bass.
• Horsehide leather has been used for boots, gloves, jackets, baseballs, and baseball gloves. The saba is a horsehide vessel used in the production of kumis. Horsehide can also be used to produce animal glue.
• Horse hooves can be used to produce hoof glue.
• Horse bones can be used to make implements. Specifically, in Italian cuisine, the horse tibia is sharpened into a probe called a spinto, which is used to test the readiness of a (pig) ham as it cures.

Riding methods and equipment

Saddling and mounting

Horse are usually ridden with a saddle on their backs to assist the rider with balance, and a bridle on their heads to assist the rider in maintaining control. However, many riders ride on occasion without a saddle and some horses can be trained to perform without a bridle or other headgear. When a horse is prepared for a ride, it is first groomed to remove dirt, particularly from the areas where the saddle and bridle will be, and has its hooves cleaned out to remove rocks or other debris that could lead to injury or lameness.

The common European practice and tradition of saddling and mounting the horse from the left hand side is widely believed to originate from the practice of right-handed fighters carrying their sheathed sword on their left hip, making it easier to throw their right leg over the horse when mounting. To correctly mount a saddled horse, the rider gathers the reins in the left hand, resting it on the horse's withers, places his or her left foot into the left stirrup, grabs onto the saddle with the right hand (the pommel if in an equitation competitition, more often the cantle in actual practice) and uses the stirrup as leverage to spring up from the ground, swing the right leg over the horse and sit into the saddlee, placing the right foot into the right stirrup. Horses can be mounted bareback with a vault from the ground, by grabbing the mane to provide leverage as a rider makes a small jump and uses the momentum of the leg to swing up in a single, smooth motion, or by "bellying over", a technique which involves placing both hands side by side on the horse's back, jumping up so that the rider lays belly down on the horse's back, and swinging the leg over to sit astride.

In actual practice, especially if the horse is tall, many riders use a fence, mounting block, or other object which can be stood upon to be able to simply slide onto the horse's back. This method, when available, is convenient for both horse and rider, as the horse is more comfortable not being accidentally jabbed by the legs and arms of the rider. However, as such objects are not always available, being able to mount from the ground is considered a standard riding skill necessary for most riders to learn.

Control of the horse

Riders communicate with the horse through commands called aids. The main natural aids of the rider are the legs, the seat, the hands (through the reins) and the voice. The rider's legs generally tell the horse to move forward or to turn. The hands help to guide the horse in the direction of the turn, and ask the horse to either slow his tempo or to slow from a faster gait to a slower one. The seat is the most difficult aid to develop, and can communicate to the horse not only to speed up, but also to turn and slow down. The voice is used less when mounted than when on the ground, but may be used to reinforce the hands, seat and legs to speed up or slow down the horse.

Correct position allows for the rider to communicate effectively without getting in the way of the horse. Though the position appears to be slightly modified according to the type of riding that is being performed, the fundamental need to remain balanced over the horse at any given speed or discipline. Like most arts, riding takes years of practice to become competent, as the riders work to refine their aids and position, and learn "feel" - the sense of what the horse is doing underneath them.

Types of riding

From the time the horse was domesticated, a wide variety of riding methods or styles have developed, all of which balance the need to allow the horse freedom of movement in activities such as horse racing or show jumping and the need for security and comfort for the rider, precision of commands, and overall control. Activities such as dressage and reining require high levels of control, while horse racing or show jumping require that a horse have considerable freedom of movement. Worldwide, the most common modern riding style is referred to in the United States as English riding, which is a broad style that encompasses most Olympic Equestrian competition, and includes such specific styles as dressage, hunt seat, show jumping and saddle seat, among many others. Western riding is a popular style seen in North America, derived from the traditions of Spain, modified to fit the needs of cattle ranchers. A similar riding style is seen with the Stockman of Australia.

Miscellaneous

Heraldry

The horse frequently occurs as a charge in heraldry. The horse can be in the "attitude" (position) "courant" (running), and when so depicted has both his fore and hind legs together, even though the position is impossible for the natural horse.

Zodiac

The horse features in the 12-year cycle of animals which appear in the Chinese zodiac related to the Chinese calendar. According to Chinese folklore, each animal is associated with certain personality traits, and those born in the year of the horse are: intelligent, independent and free-spirited. See: Horse (Zodiac).

Popularity

In a poll conducted by Animal Planet, the horse was voted World's 4th Favourite Animal. More than 50000 viewers from 73 countries voted in the poll. The tiger received 21 percent of the vote, the dog 20, the dolphin 13, the horse 10, the lion 9, the snake 8, followed by the elephant, the chimp, the orangutan and the whale.

Common myths and terminology errors

• A young horse is a foal, not necessarily a "colt." A colt refers only to a young male horse.
• A "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.
• 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). This is how a gray horse can be distinguished from a white horse. The only horses properly called white are those with pink skin under a white hair coat, a far more rare occurrence.
  • There are no truly albino horses (white skin and pink eyes). True albinism is a lethal gene in horses.

See also

• Equestrianism
• Horse care
• Equine nutrition
• Horse tack
• Horse training
• Horse breeding
• List of horse breeds
• Horses in art

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Bibliography

• Book of Horses: A Complete Medical Reference Guide for Horses and Foals, edited by Mordecai Siegal. (By members of the faculty and staff, University of California, Davis, School of Veterinary Medicine.) Harper Collins, 1996.
• Illustrated Atlas of Clinical Equine Anatomy and Common Disorders of the Horse, by Ronald J. Riegal, D.V.M. and Susan E. Hakola, B.S., R.N., C.M.I. Equistar Publications, Ltd., 1996.
• International Commission on Zoological Nomenclature. 2003. Opinion 2027 (Case 3010). Usage of 17 specific names based on wild species which are pre-dated by or contemporary with those based on domestic animals (Lepidoptera, Osteichthyes, Mammalia): conserved. Bull. Zool.Nomencl., 60:81-84.
• Bennett, Deb. Conquerors: The Roots of New World Horsemanship. Amigo Publications Inc; 1st edition 1998. ISBN 0-9658533-0-6
• Budiansky, Stephen. The Nature of Horses. Free Press, 1997. ISBN 0-684-82768-9
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• Ensminger, M. E. Horses and Tack Revised Edition Boston: Houghton Mifflin 1991 ISBN 0-395-54413-0

External links

• Cooperative Extension System eXtension Horse Site
  • "Horse breeds database". Oklahoma State University. Retrieved 2006-09-14.

• Live Horse Cam

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