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Horse
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For other uses, see Horse (disambiguation).
Horse
Two Nokota horses standing in open grassland with rolling hills and trees visible in the background.
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Conservation status
Domesticated
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Genus: Equus
Species: E. ferus
Subspecies: E. f. caballus
Trinomial name
Equus ferus caballus
Linnaeus, 1758 horses 1 horses
Synonyms horses 2 horses
at least 48 published

The horse (Equus ferus caballus) horses 2 horses horses 3 horses is one of two extant subspecies of Equus ferus. It is an odd-toed ungulate mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature, Eohippus, into the large, single-toed animal of today. Humans began domesticating horses around 4000 BC, and their domestication is believed to have been widespread by 3000 BC. Horses in the subspecies caballus are domesticated, although some domesticated populations live in the wild as feral horses. These feral populations are not true wild horses, as this term is used to describe horses that have never been domesticated, such as the endangered Przewalski's horse, a separate subspecies, and the only remaining true wild horse. 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' anatomy enables them to make use of speed to escape predators and they have a well-developed sense of balance and a strong fight-or-flight response. 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, with younger horses tending to sleep significantly more than adults. horses 4 horses 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 more than 300 breeds of horse in the world today, developed for many different uses.

Horses and humans interact in a wide variety of sport competitions and non-competitive recreational pursuits, as well as in working activities such as police work, agriculture, entertainment, and therapy. Horses were historically used in warfare, from which a wide variety of riding and driving techniques 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.

Biology
Main article: Equine anatomy
Diagram of a horse with some parts labeled.
Points of a horse horses 5 horses horses 6 horses
Specific terms and specialized language are used to describe equine anatomy, different life stages, colors and breeds.

Lifespan and life stages
Depending on breed, management and environment, the modern domestic horse has a life expectancy of 25 to 30 years. horses 7 horses Uncommonly, a few animals live into their 40s and, occasionally, beyond. horses 8 horses The oldest verifiable record was "Old Billy", a 19th-century horse that lived to the age of 62. horses 7 horses In modern times, Sugar Puff, who had been listed in Guinness World Records as the world's oldest living pony, died in 2007 at age 56. horses 9 horses

Regardless of a horse or pony's actual birth date, for most competition purposes a year is added to its age each January 1 of each year in the Northern Hemisphere horses 7 horses horses 10 horses and each August 1 in the Southern Hemisphere. horses 11 horses The exception is in endurance riding, where the minimum age to compete is based on the animal's actual calendar age. horses 12 horses

The following terminology is used to describe horses of various ages:

Foal: A foal 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. horses 13 horses Most domesticated foals are weaned at five to seven months of age, although foals can be weaned at four months with no adverse physical effects. horses 14 horses
Yearling: A horse of either sex that is between one and two years old. horses 15 horses
Colt: A male horse under the age of four. horses 16 horses A common terminology error is to call any young horse a "colt", when the term actually only refers to young male horses. horses 17 horses
Filly: A female horse under the age of four. horses 13 horses
Mare: A female horse four years old and older. horses 18 horses
Stallion: A non-castrated male horse four years old and older. horses 19 horses The term "horse" is sometimes used colloquially to refer specifically to a stallion. horses 20 horses
Gelding: A castrated male horse of any age. horses 13 horses
In horse racing, these definitions may differ: For example, in the British Isles, Thoroughbred horse racing defines colts and fillies as less than five years old. horses 21 horses However, Australian Thoroughbred racing defines colts and fillies as less than four years old. horses 22 horses

Size and measurement
The height of horses is usually measured at the highest point of the withers, where the neck meets the back. horses 23 horses This point is used because it is a stable point of the anatomy, unlike the head or neck, which move up and down in relation to the body of the horse.

In English-speaking countries, the height of horses is often stated in units of hands and inches: one hand is equal to 4 inches (101.6 mm). The height is expressed as the number of full hands, followed by a point, then the number of additional inches, and ending with the abbreviation "h" or "hh" (for "hands high"). Thus, a horse described as "15.2 h" is 15 hands plus 2 inches, for a total of 62 inches (157.5 cm) in height. horses 24 horses

A large brown horse is chasing a small horse in a pasture.
Size varies greatly among horse breeds, as with this full-sized horse and small pony.
The size of horses varies by breed, but also is influenced by nutrition. Light riding horses usually range in height from 14 to 16 hands (56 to 64 inches, 142 to 163 cm) and can weigh from 380 to 550 kilograms (840 to 1,210 lb). horses 25 horses Larger riding horses usually start at about 15.2 hands (62 inches, 157 cm) and often are as tall as 17 hands (68 inches, 173 cm), weighing from 500 to 600 kilograms (1,100 to 1,320 lb). horses 26 horses Heavy or draft horses are usually at least 16 hands (64 inches, 163 cm) high and can be as tall as 18 hands (72 inches, 183 cm) high. They can weigh from about 700 to 1,000 kilograms (1,540 to 2,200 lb). horses 27 horses

The largest horse in recorded history was probably a Shire horse named Mammoth, who was born in 1848. He stood 21.2 1⁄4 hands (86.25 inches, 219 cm) high and his peak weight was estimated at 1,524 kilograms (3,360 lb). horses 28 horses The current record holder for the world's smallest horse is Thumbelina, a fully mature miniature horse affected by dwarfism. She is 17 in (43 cm) tall and weighs 57 lb (26 kg). horses 29 horses

Ponies
Main article: Pony
Ponies are taxonomically the same animals as horses. The distinction between a horse and pony is commonly drawn on the basis of height, especially for competition purposes. However, height alone is not dispositive; the difference between horses and ponies may also include aspects of phenotype, including conformation and temperament.

The traditional standard for height of a horse or a pony at maturity is 14.2 hands (58 inches, 147 cm). An animal 14.2 h or over is usually considered to be a horse and one less than 14.2 h a pony, horses 30 horses but there are many exceptions to the traditional standard. In Australia, ponies are considered to be those under 14 hands (56 inches, 142 cm). horses 31 horses For competition in the Western division of the United States Equestrian Federation, the cutoff is 14.1 hands (57 inches, 145 cm). horses 32 horses The International Federation for Equestrian Sports, the world governing body for horse sport, uses metric measurements and defines a pony as being any horse measuring less than 148 centimetres (58.27 in) at the withers without shoes, which is just over 14.2 h, and 149 centimetres (58.66 in), or just over 14.2½ h, with shoes. horses 33 horses

Height is not the sole criterion for distinguishing horses from ponies. Breed registries for horses that typically produce individuals both under and over 14.2 h consider all animals of that breed to be horses regardless of their height. horses 34 horses 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. horses 35 horses

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 may have calmer temperaments than horses and also a high level of intelligence that may or may not be used to cooperate with human handlers. horses 30 horses Small size, by itself, is not an exclusive determinant. For example, the Shetland pony which averages 10 hands (40 inches, 102 cm), is considered a pony. horses 30 horses Conversely, breeds such as the Falabella and other miniature horses, which can be no taller than 30 inches (76 cm), are classified by their registries as very small horses, not ponies. horses 36 horses

Genetics
Horses have 64 chromosomes. horses 37 horses The horse genome was sequenced in 2007. It contains 2.7 billion DNA base pairs, horses 38 horses which is larger than the dog genome, but smaller than the human genome or the bovine genome. horses 39 horses The map is available to researchers. horses 40 horses

Colors and markings
Two horses in a field. The one on the left is a dark brown with black mane and tail. The one on the right is a light red all over.
Bay (left) and chestnut (sometimes called "sorrel") are two of the most common coat colors, seen in almost all breeds.
Main articles: Equine coat color, Equine coat color genetics, and Horse markings
Horses exhibit a diverse array of coat colors and distinctive markings, described by a specialized vocabulary. Often, a horse is classified first by its coat color, before breed or sex. horses 41 horses Horses of the same color may be distinguished from one another by white markings, horses 42 horses which, along with various spotting patterns, are inherited separately from coat color. horses 43 horses

Many genes that create horse coat colors and patterns have been identified. Current genetic tests can identify at least 13 different alleles influencing coat color, horses 44 horses and research continues to discover new genes linked to specific traits. The basic coat colors of chestnut and black are determined by the gene controlled by the Melanocortin 1 receptor, horses 45 horses also known as the "extension gene" or "red factor," horses 44 horses as its recessive form is "red" (chestnut) and its dominant form is black. horses 46 horses Additional genes control suppression of black color to point coloration that results in a bay, spotting patterns such as pinto or leopard, dilution genes such as palomino or dun, as well as graying, and all the other factors that create the many possible coat colors found in horses. horses 44 horses

Horses that have a white coat color are often mislabeled; a horse that looks "white" is usually a middle-aged or older gray. Grays are born a darker shade, get lighter as they age, but usually keep black skin underneath their white hair coat (with the exception of pink skin under white markings). The only horses properly called white are born with a predominantly white hair coat and pink skin, a fairly rare occurrence. horses 46 horses Different and unrelated genetic factors can produce white coat colors in horses, including several different alleles of dominant white and the sabino-1 gene. horses 47 horses However, there are no "albino" horses, defined as having both pink skin and red eyes. horses 48 horses

Reproduction and development
Main article: Horse breeding
Gestation lasts approximately 340 days, with an average range 320–370 days, horses 49 horses and usually results in one foal; twins are rare. horses 50 horses Horses are a precocial species, and foals are capable of standing and running within a short time following birth. horses 51 horses 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. horses 52 horses Foals are generally weaned from their mothers between four and six months of age. horses 53 horses

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 54 horses 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. horses 55 horses

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. horses 56 horses Although Thoroughbred race horses are put on the track as young as the age of two in some countries, horses 57 horses 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. horses 58 horses For endurance riding competition, horses are not deemed mature enough to compete until they are a full 60 calendar months (five years) old. horses 12 horses

Anatomy
Main articles: Equine anatomy, Muscular system of the horse, Respiratory system of the horse, and Circulatory system of the horse
Skeletal system
Main article: Skeletal system of the horse
Diagram of a horse skeleton with major parts labeled.
The skeletal system of a modern horse
The horse skeleton averages 205 bones. horses 59 horses A significant difference between the horse skeleton and that of a human is the lack of a collarbone—the horse's forelimbs are 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 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 made up of the carpal bones that correspond to the human wrist. Similarly, the hock contains 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, hair, bone, tendons, ligaments, cartilage, and the assorted specialized tissues that make up the hoof. horses 60 horses

Hooves
Main articles: Horse hoof, Horseshoe, and Farrier
The critical importance of the feet and legs is summed up by the traditional adage, "no foot, no horse". horses 61 horses 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. The exterior hoof wall and horn of the sole is made of keratin, the same material as a human fingernail. horses 62 horses The end result is that a horse, weighing on average 500 kilograms (1,100 lb), horses 63 horses travels on the same bones as would a human on tiptoe. horses 64 horses 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, and in most domesticated horses needs to be trimmed (and horseshoes reset, if used) every five to eight weeks, horses 65 horses though the hooves of horses in the wild wear down and regrow at a rate suitable for their terrain.

Teeth
Main article: Horse teeth
Horses are adapted to grazing. In an adult horse, there are 12 incisors at the front of the mouth, adapted to biting off the grass or other vegetation. 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 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 gums, or "bars" of the horse's mouth when the horse is bridled. horses 66 horses

An estimate of a horse's age can be made from looking at its teeth. The teeth continue to erupt throughout life and are worn down by grazing. Therefore, the incisors show changes as the horse ages; they develop a distinct wear pattern, changes in tooth shape, and changes in the angle at which the chewing surfaces meet. This allows a very rough estimate of a horse's age, although diet and veterinary care can also affect the rate of tooth wear. horses 7 horses

Digestion
Main articles: Equine digestive system and Equine nutrition
Horses are herbivores with a digestive system adapted to a forage diet of grasses and other plant material, consumed steadily throughout the day. Therefore, compared to humans, they have a relatively small stomach but very long intestines to facilitate a steady flow of nutrients. A 450-kilogram (990 lb) horse will eat 7 to 11 kilograms (15 to 24 lb) of food per day and, under normal use, drink 38 to 45 litres (8.4 to 9.9 imp gal; 10 to 12 US gal) of water. Horses are not ruminants, they have only one stomach, like humans, but unlike humans, they can utilize cellulose, a major component of grass. Horses are hindgut fermenters. Cellulose fermentation by symbiotic bacteria occurs in the cecum, or "water gut", which food goes through before reaching the large intestine. Horses cannot vomit, so digestion problems can quickly cause colic, a leading cause of death. horses 67 horses

Senses
Close up of a horse eye, with is dark brown with lashes on the top eyelid
A horse's eye
See also: Equine vision
The horses' senses are based on their status as prey animals, where they must be aware of their surroundings at all times. horses 68 horses They have the largest eyes of any land mammal, horses 69 horses and are lateral-eyed, meaning that their eyes are positioned on the sides of their heads. horses 70 horses This means that horses have a range of vision of more than 350°, with approximately 65° of this being binocular vision and the remaining 285° monocular vision. horses 69 horses Horses have excellent day and night vision, but they have two-color, or dichromatic vision; their color vision is somewhat like red-green color blindness in humans, where certain colors, especially red and related colors, appear as a shade of green. horses 71 horses

Their sense of smell, while much better than that of humans, is not quite as good as that of a dog. It is believed to play a key role in the social interactions of horses as well as detecting other key scents in the environment. Horses have two olfactory centers. The first system is in the nostrils and nasal cavity, which analyze a wide range of odors. The second, located under the nasal cavity, are the Vomeronasal organs, also called Jacobson's organs. These have a separate nerve pathway to the brain and appear to primarily analyze pheromones. horses 72 horses

A horse's hearing is good, horses 68 horses and the pinna of each ear can rotate up to 180°, giving the potential for 360° hearing without having to move the head. horses 73 horses Noise impacts the behavior of horses and certain kinds of noise may contribute to stress: A 2013 study in the UK indicated that stabled horses were calmest in a quiet setting, or if listening to country or classical music, but displayed signs of nervousness when listening to jazz or rock music. This study also recommended keeping music under a volume of 21 decibels. horses 74 horses An Australian study found that stabled racehorses listening to talk radio had a higher rate of gastric ulcers than horses listening to music, and racehorses stabled where a radio was played had a higher overall rate of ulceration than horses stabled where there was no radio playing. horses 75 horses

Horses have a great sense of balance, due partly to their ability to feel their footing and partly to highly developed proprioception—the unconscious sense of where the body and limbs are at all times. horses 76 horses A horse's sense of touch is well developed. The most sensitive areas are around the eyes, ears, and nose. horses 77 horses Horses are able to sense contact as subtle as an insect landing anywhere on the body. horses 78 horses

Horses have an advanced sense of taste, which allows them to sort through fodder and choose what they would most like to eat, horses 79 horses and their prehensile lips can easily sort even small grains. Horses generally will not eat poisonous plants, however, there are exceptions; horses will occasionally eat toxic amounts of poisonous plants even when there is adequate healthy food. horses 80 horses

Movement

Walk 5–8 km/h (3.1–5.0 mph)



Trot 8–13 km/h (5.0–8.1 mph)



Pace 8–13 km/h (5.0–8.1 mph)



Canter 16–27 km/h (9.9–16.8 mph)



Gallop 25–30 km/h (16–19 mph), record: 70.76 km/h (43.97 mph) horses 81 horses

Main articles: Horse gait, Trot (horse gait), Canter, and Ambling
All horses move naturally with four basic gaits: the four-beat walk, which averages 6.4 kilometres per hour (4.0 mph); the two-beat trot or jog at 13 to 19 kilometres per hour (8.1 to 11.8 mph) (faster for harness racing horses); the canter or lope, a three-beat gait that is 19 to 24 kilometres per hour (12 to 15 mph); and the gallop. horses 82 horses The gallop averages 40 to 48 kilometres per hour (25 to 30 mph), horses 83 horses but the world record for a horse galloping over a short, sprint distance is 70.76 kilometres per hour (43.97 mph). horses 81 horses Besides these basic gaits, some horses perform a two-beat pace, instead of the trot. horses 84 horses There also are several four-beat "ambling" gaits that are approximately the speed of a trot or pace, though smoother to ride. These include the lateral rack, running walk, and tölt as well as the diagonal fox trot. horses 85 horses Ambling gaits are often genetic in some breeds, known collectively as gaited horses. horses 86 horses Often, gaited horses replace the trot with one of the ambling gaits. horses 87 horses

Behavior
Main articles: Horse behavior and Stable vices
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. horses 88 horses 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 89 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. horses 90 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" (rocking back and forth), and other problems. horses 91 horses

Intelligence and learning
Studies have indicated that horses perform a number of cognitive tasks on a daily basis, meeting mental challenges that include food procurement and identification of individuals within a social system. They also have good spatial discrimination abilities. horses 92 horses They are naturally curious and apt to investigate things they have not seen before. horses 93 horses Studies have assessed equine intelligence in areas such as problem solving, speed of learning, and memory. Horses excel at simple learning, but also are able to use more advanced cognitive abilities that involve categorization and concept learning. They can learn using habituation, desensitization, classical conditioning, and operant conditioning, and positive and negative reinforcement. horses 92 horses One study has indicated that horses can differentiate between "more or less" if the quantity involved is less than four. horses 94 horses

Domesticated horses may face greater mental challenges than wild horses, because they live in artificial environments that prevent instinctive behavior whilst also learning tasks that are not natural. horses 92 horses Horses are animals of habit that respond well to regimentation, and respond best when the same routines and techniques are used consistently. One trainer believes that "intelligent" horses are reflections of intelligent trainers who effectively use response conditioning techniques and positive reinforcement to train in the style that best fits with an individual animal's natural inclinations. horses 95 horses

Temperament
Main articles: Draft horse, Warmblood, and Oriental horse
Horses are mammals, and as such are warm-blooded, or endothermic creatures, as opposed to cold-blooded, or poikilothermic animals. However, these words have developed a separate meaning in the context of equine terminology, used to describe temperament, not body temperature. For example, the "hot-bloods", such as many race horses, exhibit more sensitivity and energy, horses 96 horses while the "cold-bloods", such as most draft breeds, are quieter and calmer. horses 97 horses Sometimes "hot-bloods" are classified as "light horses" or "riding horses", horses 98 horses with the "cold-bloods" classified as "draft horses" or "work horses". horses 99 horses

a sepia-toned engraving from an old book, showing 11 horses of different breeds and sizes in nine different illustrations
Illustration of assorted breeds; slim, light hotbloods, medium-sized warmbloods and draft and pony-type coldblood breeds
"Hot blooded" breeds include "oriental horses" such as the Akhal-Teke, Arabian horse, Barb and now-extinct Turkoman horse, as well as the Thoroughbred, a breed developed in England from the older oriental breeds. horses 96 horses Hot bloods tend to be spirited, bold, and learn quickly. They are bred for agility and speed. horses 100 horses They tend to be physically refined—thin-skinned, slim, and long-legged. horses 101 horses The original oriental breeds were brought to Europe from the Middle East and North Africa when European breeders wished to infuse these traits into racing and light cavalry horses. horses 102 horses horses 103 horses

Muscular, heavy draft horses are known as "cold bloods", as they are bred not only for strength, but also to have the calm, patient temperament needed to pull a plow or a heavy carriage full of people. horses 97 horses They are sometimes nicknamed "gentle giants". horses 104 horses Well-known draft breeds include the Belgian and the Clydesdale. horses 104 horses Some, like the Percheron, are lighter and livelier, developed to pull carriages or to plow large fields in drier climates. horses 105 horses Others, such as the Shire, are slower and more powerful, bred to plow fields with heavy, clay-based soils. horses 106 horses The cold-blooded group also includes some pony breeds. horses 107 horses

"Warmblood" breeds, such as the Trakehner or Hanoverian, developed when European carriage and war horses were crossed with Arabians or Thoroughbreds, producing a riding horse with more refinement than a draft horse, but greater size and milder temperament than a lighter breed. horses 108 horses Certain pony breeds with warmblood characteristics have been developed for smaller riders. horses 109 horses Warmbloods are considered a "light horse" or "riding horse". horses 98 horses

Today, the term "Warmblood" refers to a specific subset of sport horse breeds that are used for competition in dressage and show jumping. horses 110 horses Strictly speaking, the term "warm blood" refers to any cross between cold-blooded and hot-blooded breeds. horses 111 horses Examples include breeds such as the Irish Draught or the Cleveland Bay. The term was once used to refer to breeds of light riding horse other than Thoroughbreds or Arabians, such as the Morgan horse. horses 100 horses

Sleep patterns
See also: Horse sleep patterns and Sleep in non-humans
Two horses in a pasture, one is standing beside the other that is laying down.
When horses lie down to sleep, others in the herd remain standing, awake or in a light doze, keeping watch.
Horses are able to sleep both standing up and lying down. In an adaptation from life in the wild, horses are able to enter light sleep by using a "stay apparatus" in their legs, allowing them to doze without collapsing. horses 112 horses Horses sleep better when in groups because some animals will sleep while others stand guard to watch for predators. A horse kept alone will not sleep well because its instincts are to keep a constant eye out for danger. horses 113 horses

Unlike humans, horses do not sleep in a solid, unbroken period of time, but take many short periods of rest. Horses spend four to fifteen hours a day in standing rest, and from a few minutes to several hours lying down. Total sleep time in a 24-hour period may range from several minutes to a couple of hours, horses 113 horses mostly in short intervals of about 15 minutes each. horses 114 horses The average sleep time of a domestic horse is said to be 2.9 hours per day. horses 115 horses

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. horses 113 horses 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. horses 116 horses This condition differs from narcolepsy, although horses may also suffer from that disorder. horses 117 horses

Taxonomy and evolution

From left to right: Size development, biometrical changes in the cranium, reduction of toes (left forefoot)
Main articles: Evolution of the horse, Equus (genus), and Equidae
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 118 horses 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 horse and related species), Tapiridae (the tapir), and Rhinocerotidae (the rhinoceroses)—have survived to the present day. horses 119 horses

The earliest known member of the family Equidae 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. horses 120 horses The extra toe on the front feet soon disappeared with the Mesohippus, which lived 32 to 37 million years ago. horses 121 horses 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, horses 122 horses known informally as splint bones. horses 123 horses Their legs also lengthened as their toes disappeared until they were a hooved animal capable of running at great speed. horses 122 horses By about 5 million years ago, the modern Equus had evolved. horses 124 horses 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. horses 125 horses Yet between 10,000 and 7,600 years ago, the horse became extinct in North America and rare elsewhere. horses 126 horses horses 127 horses horses 128 horses The reasons for this extinction are not fully known, but one theory notes that extinction in North America paralleled human arrival. horses 129 horses 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. horses 130 horses

Wild species surviving into modern times
Three tan colored horses with upright manes. Two horses nip and paw at each other, while the third moves towards the camera. They stand in open, rocky grassland, with forests in the distance.
A small herd of Przewalski's Horses
Main article: Wild horse
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. horses 131 horses 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 (Equus ferus przewalskii), 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. horses 132 horses Today, a small wild breeding population exists in Mongolia. horses 133 horses horses 134 horses There are additional animals still maintained at zoos throughout the world.

The tarpan or European wild horse (Equus ferus ferus) 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. horses 135 horses Thus, the genetic line was lost. Attempts have been made to recreate the tarpan, horses 135 horses horses 136 horses horses 137 horses 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, horses 134 horses but testing did not reveal genetic differences from domesticated horses. horses 138 horses Similarly, the Sorraia of Portugal was proposed as a direct descendant of the Tarpan based on shared characteristics, horses 139 horses horses 140 horses 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. horses 139 horses horses 141 horses

Other modern equids
Main article: Equus (genus)
Besides the horse, there are six other species of genus Equus in the Equidae family. These are the ass or donkey, Equus asinus; the mountain zebra, Equus zebra; plains zebra, Equus quagga; Grévy's zebra, Equus grevyi; the kiang, Equus kiang; and the onager, Equus hemionus. horses 142 horses

Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). horses 143 horses Other hybrids include the zorse, a cross between a zebra and a horse. horses 144 horses With rare exceptions, most hybrids are sterile and cannot reproduce. horses 145 horses

Domestication
Main articles: History of horse domestication theories and Domestication of the horse

Bhimbetka rock painting showing man riding on horse, India
Domestication of the horse most likely took place in central Asia prior to 3500 BC. Two major sources of information are used to determine where and when the horse was first domesticated and how the domesticated horse spread around the world. The first source is based on palaeological and archaeological discoveries; the second source is a comparison of DNA obtained from modern horses to that from bones and teeth of ancient horse remains.

The earliest archaeological evidence for the domestication of the horse comes from sites in Ukraine and Kazakhstan, dating to approximately 3500–4000 BC. horses 146 horses horses 147 horses horses 148 horses 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. horses 149 horses 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. horses 150 horses

Domestication is also studied by using the genetic material of present-day horses and comparing it with the genetic material present in the bones and teeth of horse remains found in archaeological and palaeological excavations. The variation in the genetic material shows that very few wild stallions contributed to the domestic horse, horses 151 horses horses 152 horses while many mares were part of early domesticated herds. horses 141 horses horses 153 horses horses 154 horses This is reflected in the difference in genetic variation between the DNA that is passed on along the paternal, or sire line (Y-chromosome) versus that passed on along the maternal, or dam line (mitochondrial DNA). There are very low levels of Y-chromosome variability, horses 151 horses horses 152 horses but a great deal of genetic variation in mitochondrial DNA. horses 141 horses horses 153 horses horses 154 horses There is also regional variation in mitochondrial DNA due to the inclusion of wild mares in domestic herds. horses 141 horses horses 153 horses horses 154 horses horses 155 horses Another characteristic of domestication is an increase in coat color variation. horses 156 horses In horses, this increased dramatically between 5000 and 3000 BC. horses 157 horses

Before the availability of DNA techniques to resolve the questions related to the domestication of the horse, various hypotheses were proposed. One classification was based on body types and conformation, suggesting the presence of four basic prototypes that had adapted to their environment prior to domestication. horses 107 horses Another hypothesis held that the four prototypes originated from a single wild species and that all different body types were entirely a result of selective breeding after domestication. horses 158 horses However, the lack of a detectable substructure in the horse has resulted in a rejection of both hypotheses.

Feral populations
Main article: Feral horse
Feral horses are born and live in the wild, but are descended from domesticated animals. horses 131 horses Many populations of feral horses exist throughout the world. horses 159 horses horses 160 horses Studies of feral herds have provided useful insights into the behavior of prehistoric horses, horses 161 horses as well as greater understanding of the instincts and behaviors that drive horses that live in domesticated conditions. horses 162 horses

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. horses 163 horses horses 164 horses

Breeds
Main articles: Horse breed, List of horse breeds, and Horse breeding
The concept of purebred bloodstock and a controlled, written breed registry has come to be particularly significant and important in modern times. Sometimes purebred horses are incorrectly or inaccurately called "thoroughbreds". 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. horses 165 horses 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 result from a combination of natural crosses and artificial selection methods. Horses have been selectively bred since their domestication. An early example of people who practiced selective horse breeding were the Bedouin, who had a reputation for careful practices, keeping extensive pedigrees of their Arabian horses and placing great value upon pure bloodlines. horses 166 horses These pedigrees were originally transmitted via an oral tradition. horses 167 horses In the 14th century, Carthusian monks of southern Spain kept meticulous pedigrees of bloodstock lineages still found today in the Andalusian horse. horses 168 horses

Breeds developed due to a need for "form to function", the necessity to develop certain characteristics in order to perform a particular type of work. horses 169 horses Thus, a powerful but refined breed such as the Andalusian developed as riding horses with an aptitude for dressage. horses 169 horses Heavy draft horses developed out of a need to perform demanding farm work and pull heavy wagons. horses 170 horses Other horse breeds developed specifically for light agricultural work, carriage and road work, various sport disciplines, or simply as pets. horses 171 horses Some breeds developed through centuries of crossing other breeds, while others descended from a single foundation sire, or other limited or restricted foundation bloodstock. One of the earliest formal registries was General Stud Book for Thoroughbreds, which began in 1791 and traced back to the foundation bloodstock for the breed. horses 172 horses There are more than 300 horse breeds in the world today. horses 173 horses

Interaction with humans

Equine hospital in the United Kingdom
Worldwide, horses play a role within human cultures and have done so for millennia. The genetic makeup of the human population in a geographical area is affected by the presence or absence of horses (more variation in Africa, less in Eurasian steppes). Societies where horse riding is an integral part of life have developed traditional attires specially suited for horse riding such as tightly wrapping waistbands or Cummerbunds giving wide support useful for protecting the spine during long journeys, and voluminous headgear such as turban to protect the skull during falls from the horse. Horses are used for leisure activities, sports, and working purposes. The Food and Agriculture Organization (FAO) estimates that in 2008, there were almost 59,000,000 horses in the world, with around 33,500,000 in the Americas, 13,800,000 in Asia and 6,300,000 in Europe and smaller portions in Africa and Oceania. There are estimated to be 9,500,000 horses in the United States alone. horses 174 horses 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. horses 175 horses In a 2004 "poll" conducted by Animal Planet, more than 50,000 viewers from 73 countries voted for the horse as the world's 4th favorite animal. horses 176 horses

Communication between human and horse is paramount in any equestrian activity; horses 177 horses to aid this process horses are usually ridden with a saddle on their backs to assist the rider with balance and positioning, and a bridle or related headgear to assist the rider in maintaining control. horses 178 horses Sometimes horses are ridden without a saddle, horses 179 horses and occasionally, horses are trained to perform without a bridle or other headgear. horses 180 horses Many horses are also driven, which requires a harness, bridle, and some type of vehicle. horses 181 horses

Sport
A chestnut (reddish-brown) horse being ridden by a rider in a black coat and top hat. They are stopped in a riding arena with the rider tipping his hat.
A horse and rider in dressage competition at the Olympics
Main articles: Equestrianism, Horse racing, Horse training, and Horse tack
Historically, equestrians honed their skills through games and races. Equestrian sports provided entertainment for crowds and honed the excellent horsemanship that was needed in battle. Many sports, such as dressage, eventing and show jumping, have origins in military training, which were focused on control and balance of both horse and rider. Other sports, such as rodeo, developed from practical skills such as those needed on working ranches and stations. Sport hunting from horseback evolved from earlier practical hunting techniques. horses 177 horses Horse racing of all types evolved from impromptu competitions between riders or drivers. All forms of competition, requiring demanding and specialized skills from both horse and rider, resulted in the systematic development of specialized breeds and equipment for each sport. The popularity of equestrian sports through the centuries has resulted in the preservation of skills that would otherwise have disappeared after horses stopped being used in combat. horses 177 horses

Horses are trained to be ridden or driven in a variety of sporting competitions. Examples include show jumping, dressage, three-day eventing, competitive driving, endurance riding, gymkhana, rodeos, and fox hunting. horses 182 horses Horse shows, which have their origins in medieval European fairs, are held around the world. They host a huge range of classes, covering all of the mounted and harness disciplines, as well as "In-hand" classes where the horses are led, rather than ridden, to be evaluated on their conformation. The method of judging varies with the discipline, but winning usually depends on style and ability of both horse and rider. horses 183 horses Sports such as polo 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 requires specialized training to participate, 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 task. horses 184 horses Examples of these sports of partnership between human and horse include jousting, in which the main goal is for one rider to unseat the other, horses 185 horses and buzkashi, a team game played throughout Central Asia, the aim being to capture a goat carcass while on horseback. horses 184 horses

Horse racing is an equestrian sport and major international industry, watched in almost every nation of 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. horses 186 horses A major part of horse racing's economic importance lies in the gambling associated with it. horses 187 horses

Work
A mounted man in a blue uniform on a dark brown horse
A mounted police officer in Poland
There are certain jobs that horses do very well, and no technology has yet developed to fully replace them. For example, mounted police horses are still effective for certain types of patrol duties and crowd control. horses 188 horses Cattle ranches still require riders on horseback to round up cattle that are scattered across remote, rugged terrain. horses 189 horses Search and rescue organizations in some countries depend upon mounted teams to locate people, particularly hikers and children, and to provide disaster relief assistance. horses 190 horses Horses can also be used in areas where it is necessary to avoid vehicular disruption to delicate soil, such as nature reserves. They may also be the only form of transport allowed in wilderness areas. Horses are quieter than motorized vehicles. Law enforcement officers such as park rangers or game wardens may use horses for patrols, and horses or mules may also be used for clearing trails or other work in areas of rough terrain where vehicles are less effective. horses 191 horses


Tanga (carriage) at Darbhanga Bihar
Although machinery has replaced horses in many parts of the world, an estimated 100 million horses, donkeys and mules are still used for agriculture and transportation in less developed areas. This number includes around 27 million working animals in Africa alone. horses 192 horses Some land management practices such as cultivating and logging can be efficiently performed with horses. In agriculture, less fossil fuel is used and increased environmental conservation occurs over time with the use of draft animals such as horses. horses 193 horses horses 194 horses Logging with horses can result in reduced damage to soil structure and less damage to trees due to more selective logging. horses 195 horses

Warfare
Main article: Horses in warfare
Black and white photo of mounted soldiers with middle eastern headwraps, carrying rifles, walking down a road away from the camera
Turkish cavalry, 1917

A bloated dead horse on the ground in front of Napoleon and Poniatowski at the Battle of Leipzig, painted by January Suchodolski
Horses have been used in warfare for most of recorded history. The first archaeological evidence of horses used in warfare dates to between 4000 and 3000 BC, horses 196 horses and the use of horses in warfare was widespread by the end of the Bronze Age. horses 197 horses horses 198 horses Although 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 War in Darfur. horses 199 horses

Entertainment and culture

The horse-headed deity in Hinduism, Hayagriva
See also: Horses in art and Horse worship
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 200 horses 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. horses 201 horses 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 202 horses

Horses are frequently used 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. horses 203 horses Both live horses and iconic images of horses are used in advertising to promote a variety of products. horses 204 horses The horse frequently appears in coats of arms in heraldry, in a variety of poses and equipment. horses 205 horses 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. horses 206 horses The horse also appears in the 12-year cycle of animals in the Chinese zodiac related to the Chinese calendar. horses 207 horses

Therapeutic use
See also: Hippotherapy and Therapeutic horseback riding
People of all ages with physical and mental disabilities obtain beneficial results from association with horses. Therapeutic riding is used to mentally and physically stimulate disabled persons and help them improve their lives through improved balance and coordination, increased self-confidence, and a greater feeling of freedom and independence. horses 208 horses 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 International Federation for Equestrian Sports (FEI). horses 209 horses Hippotherapy and therapeutic horseback riding are names for different physical, occupational, and speech therapy treatment strategies that utilize equine movement. In hippotherapy, a therapist uses the horse's movement to improve their patient's cognitive, coordination, balance, and fine motor skills, whereas therapeutic horseback riding uses specific riding skills. horses 210 horses

Horses also provide psychological benefits to people whether they actually ride or not. "Equine-assisted" or "equine-facilitated" therapy is a form of experiential psychotherapy that uses horses as companion animals to assist people with mental illness, including anxiety disorders, psychotic disorders, mood disorders, behavioral difficulties, and those who are going through major life changes. horses 211 horses There are also experimental programs using horses in prison settings. Exposure to horses appears to improve the behavior of inmates and help reduce recidivism when they leave. horses 212 horses

Products
Horses are raw material for many products made by humans throughout history, including byproducts from the slaughter of horses as well as materials collected from living horses.

Products collected from living horses include mare's milk, used by people with large horse herds, such as the Mongols, who let it ferment to produce kumis. horses 213 horses Horse blood was once used as food by the Mongols and other nomadic tribes, who found it a convenient source of nutrition when traveling. Drinking their own horses' blood allowed the Mongols to ride for extended periods of time without stopping to eat. horses 213 horses The drug Premarin is a mixture of estrogens extracted from the urine of pregnant mares (pregnant mares' urine), and was previously a widely used drug for hormone replacement therapy. horses 214 horses The tail hair of horses can be used for making bows for string instruments such as the violin, viola, cello, and double bass. horses 215 horses

Horse meat has been used as food for humans and carnivorous animals throughout the ages. It is eaten in many parts of the world, though consumption is taboo in some cultures, horses 216 horses and a subject of political controversy in others. horses 217 horses Horsehide leather has been used for boots, gloves, jackets, horses 218 horses baseballs, horses 219 horses and baseball gloves. Horse hooves can also be used to produce animal glue. horses 220 horses Horse bones can be used to make implements. horses 221 horses 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. horses 222 horses In Asia, the saba is a horsehide vessel used in the production of kumis. horses 223 horses

Care
Main article: Horse care
See also: Equine nutrition, Horse grooming, Veterinary medicine, and Farrier
A young man in US military clothing examines the teeth of a bay (dark brown) horse, while another person in military work clothing, partially obscured, holds the horse. Several other people are partially visible in the background.
Checking teeth and other physical examinations are an important part of horse care.
Horses are grazing animals, and their major source of nutrients is good-quality forage from hay or pasture. horses 224 horses They can consume approximately 2% to 2.5% of their body weight in dry feed each day. Therefore, a 450-kilogram (990 lb) adult horse could eat up to 11 kilograms (24 lb) of food. horses 225 horses Sometimes, concentrated feed such as grain is fed in addition to pasture or hay, especially when the animal is very active. horses 226 horses When grain is fed, equine nutritionists recommend that 50% or more of the animal's diet by weight should still be forage. horses 227 horses

Horses require a plentiful supply of clean water, a minimum of 10 US gallons (38 L) to 12 US gallons (45 L) per day. horses 228 horses 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 229 horses

Horses require routine hoof care from a farrier, as well as vaccinations to protect against various diseases, and dental examinations from a veterinarian or a specialized equine dentist. horses 230 horses If horses are kept inside in a barn, they require regular daily exercise for their physical health and mental well-being. horses 231 horses When turned outside, they require well-maintained, sturdy fences to be safely contained. horses 232 horses Regular grooming is also helpful to help the horse maintain good health of the hair coat and underlying skin. horses 233 horses