Horse (Equus caballus): Facts, Breeds, Speed and Lifespan

What kind of animal is a horse?

Horses belong to the family Equidae, which also includes donkeys and zebras. All living members are placed in one genus, Equus, and they are odd-toed hoofed mammals (order Perissodactyla), like rhinos and tapirs. Each leg ends in a single toe protected by a hard hoof, the horse’s version of a very large toenail.

Scientists use two names for the domestic horse. Many write Equus caballus, while others treat it as a subspecies of the wild horse, Equus ferus caballus. The only surviving wild relative of the same species group is Przewalski’s horse of Mongolia, covered below.

Evolution: from fox-sized to horse-sized

The horse family has one of the best fossil records of any mammal. The earliest known member, often called Eohippus or Hyracotherium, lived 55 to 45 million years ago and was about the size of a fox, with four toes on its front feet and three on the hind feet. Over millions of years, horses in North America grew larger, their side toes shrank to tiny splint bones and their teeth became tall and ridged for grinding tough grass.

Horses crossed the Bering land bridge into Asia several times. Curiously, they then died out in the Americas around 10,000 years ago, at the end of the last Ice Age, and only returned when Spanish ships brought domestic horses from 1493 onward.

When were horses domesticated?

People hunted wild horses for tens of thousands of years before taming them. Around 5,500 years ago, the Botai culture of what is now Kazakhstan kept and probably milked horses, but ancient DNA shows those animals were ancestors of Przewalski’s horses, not of today’s breeds.

A large ancient-DNA study led by Pablo Librado and Ludovic Orlando, published in Nature in 2021, traced all modern domestic horses to the western Eurasian steppes near the lower Volga and Don rivers. These horses spread across Asia and Europe very quickly from about 2200 BCE, together with spoke-wheeled chariots, and replaced almost every other horse population.

Appearance and senses

A horse has a long head, a long muscular neck with a mane, a deep chest, slender legs and a long tail of coarse hair. Coat colors include bay (brown with a black mane and legs), chestnut, black, gray, palomino, dun and many spotted and white patterns. Gray horses are born dark and turn whiter with age.

Horses are prey animals, and their senses are built to spot danger early:

• Sight: the eyes are among the largest of any land mammal and sit on the sides of the head, giving a field of view of about 350 degrees. Horses see well at night and see blue and yellow tones but not red, as explained in What colors can horses see?.
• Hearing: each ear can swivel independently toward a sound, and ear position is also a key signal to other horses.
• Smell and taste: horses greet each other nose to nose and use the flehmen response, curling back the upper lip, to draw scents toward a special organ in the roof of the mouth.
• Touch: whiskers on the muzzle and sensitive skin let a horse feel a fly land almost anywhere on its body.

How big is a horse?

Horses vary in size more than almost any other domestic animal. Their height is measured at the withers, the top of the shoulders, and in English-speaking countries it is often given in hands: one hand equals 4 inches (10.16 cm).

The tallest and heaviest horse on record was a Shire gelding called Sampson, later renamed Mammoth, born in England in 1846. He stood about 2.19 m (7 ft 2 in) and was estimated to weigh 1,520 kg (3,360 lb). The smallest was Thumbelina, a dwarf miniature horse in Missouri only 43 cm (17 in) tall. Find more in How big is a horse?.

Where do horses live?

Wild horses once roamed grasslands across Europe, northern Asia and North America. Domestic horses now live on every continent except Antarctica, mostly on farms, ranches, stables and pastures. They do best in open, grassy country with fresh water, but hardy breeds cope with Icelandic winters, Mongolian steppe and hot semi-deserts.

Feral horses, descendants of escaped or released domestic animals, live wild in the American West (mustangs), Australia (brumbies), on Sable Island off Nova Scotia and Assateague Island on the US Atlantic coast, in the Namib Desert and elsewhere. Semi-feral ponies graze open moorland and heath in Britain, such as Exmoor, Dartmoor and the New Forest.

Wild horses: tarpan and Przewalski’s horse

Almost every “wild” horse alive today is feral, descended from domestic stock. The tarpan, the wild horse of Europe and western Asia, died out in 1909 when the last captive animal died in Russia. The only population usually treated as truly wild is Przewalski’s horse (Equus ferus przewalskii), which disappeared from the wild in the late 1960s but has been reintroduced to Mongolia from zoo-bred stock since 1992. The IUCN lists it as Endangered.

Przewalski’s horses are stocky, dun-colored and about 1.2–1.4 m (48–56 in) tall, with an upright mane, and they have 66 chromosomes instead of the domestic horse’s 64. Their “wild” status has been debated since a 2018 study in Science linked them to the early horses of the Botai culture.

Diet: what do horses eat?

Horses are grazers. In the wild or at pasture they eat mainly grasses, plus herbs, sedges and some leaves and bark. Feral horses spend more than half of each day feeding, taking small amounts almost continuously rather than a few large meals.

A horse’s front teeth snip off grass, and its large cheek teeth grind it down. These cheek teeth are very tall and keep erupting from the jaw throughout adult life as their surfaces wear away. Food is then digested mainly in a huge hindgut, where microbes in the cecum and colon break down plant fiber. This system handles large amounts of low-quality forage but makes the horse very sensitive to sudden changes in food.

Gaits and speed

Horses have four natural gaits. The walk averages about 6.4 km/h (4 mph), the trot about 13–19 km/h (8–12 mph), the canter about 19–24 km/h (12–15 mph), and the gallop typically 40–48 km/h (25–30 mph). Some breeds have extra gaits, such as the four-beat tölt of the Icelandic horse or the pace of harness-racing Standardbreds.

The fastest officially timed horse was a Thoroughbred filly named Winning Brew, clocked at 70.76 km/h (43.97 mph) over a short sprint in Pennsylvania in 2008. Quarter Horses, bred for quarter-mile races, are the quickest over very short distances. Horses are also endurance athletes: top endurance horses cover 160 km (100 miles) in a single day. Full details are in How fast can a horse run?.

Behavior and herd life

Horses are deeply social. In feral herds, the basic unit is a band of one stallion (sometimes two or three), several mares and their young. Young males leave and join bachelor groups until they can win mares of their own. Within a band, horses have a clear but usually peaceful pecking order, and an experienced mare often leads the group to water and grazing.

Horses keep friendships through mutual grooming, nibbling each other’s necks and withers. They communicate with ear and tail positions, facial expressions and sounds such as the loud whinny, the soft nicker of greeting and the sharp squeal of protest. When frightened, a horse’s first instinct is to flee, and a whole herd can bolt within a second.

Being prey animals affects how horses rest. They can doze standing up thanks to a locking system of tendons and ligaments in their legs, but they must lie down for deep REM sleep. Herd members take turns to stand watch, as explained in Can horses sleep standing up?.

Reproduction and life cycle

Mares come into season every three weeks or so from spring to autumn. Pregnancy lasts about 11 months, roughly 340 days on average, with a normal range of about 320–370 days. A mare usually has one foal, and twins are rare.

Foals are born well developed. Most stand within an hour of birth, nurse soon after and can follow their mother within a few hours. A domestic foal weighs around 40 kg (90 lb) at birth, about a tenth of its mother’s weight, and is usually weaned at four to six months. Wild foals may nurse for a year or more. Horses are considered mature at about four or five years, though their skeleton keeps developing until around six.

How long do horses live?

The average lifespan of a domestic horse is about 25–30 years, and many ponies and small horses reach their 30s. The oldest reliably recorded horse was Old Billy, an English canal barge horse who lived from 1760 to 1822 and died at 62. Feral horses generally live shorter lives because of harsh weather, predators and worn-out teeth. Read more in How long do horses live?.

Horses and people

No other animal reshaped human history quite like the horse. Horses made it possible to travel, trade and wage war over long distances, carried mail and settlers, pulled plows, carriages and trams, and powered farms until tractors took over in the 20th century. Words such as “horsepower” still record that role.

Today most horses in Europe and North America are kept for riding, sport and leisure: racing, show jumping, dressage, eventing, endurance and rodeo. Mounted police and working ranch horses remain in use, and in many poorer regions horses, donkeys and mules still do daily farm and transport work. Horse milk is fermented into kumis in Central Asia, and horsehair is used for violin bows.

Myths and facts

Myth: horses only sleep standing up. Horses doze on their feet, but they must lie down, often flat on their side, to get REM sleep.

Myth: horses see the world in black and white. They have two-color vision, similar to a person with red-green color blindness, and see blues and yellows clearly.

Fact: horses cannot normally vomit or breathe through their mouths. A tight valve at the stomach entrance prevents vomiting, and a horse breathes through its nose except in rare cases.

Fact: horses are closely related to zebras and donkeys. All can interbreed, though the hybrids, such as the mule of a donkey father and a horse mother, are almost always sterile.