A horse uses its ears to hear, and ears pointed stiffly forward mean the horse is alert. Horses can hear sounds from 14 Hz to 25 kHz, while the human range is 20 Hz to 20 kHz. A horse sees mostly with each eye separately, which gives it a panoramic view, and it has blind spots directly in front of it and directly behind it. Horses see color, but fewer colors than people do. A horse stands on a single toe on each foot, and the toe is covered by a hoof. The hoof wall does not contain blood vessels or nerves, and it keeps growing and must be worn or trimmed off, at about 1/4 to 3/8 of an inch a month.
Horses are grazers that mostly eat grass, and they naturally graze for 12 to 16 hours a day. A horse's cheek teeth erupt continuously during its life to make up for wear of 3 to 4 mm per year, and they are tall-crowned and specialized for grazing. A mare gives birth to a baby horse called a foal, and the normal gestation length of mares ranges from 320 to 380 days, with an average of 338 to 345 days. A foal can stand up within about an hour of being born, and a mare's first milk, called colostrum, has antibodies that help protect the foal from infection.
The oldest known horse, Hyracotherium, is better known as eohippus, which means the dawn horse. It was a small, dog-sized animal that lived in forests and ate leaves, from around 55 million years ago to around 45 million years ago. It had 4 toes on each front foot and 3 toes on each hind foot. Over millions of years the ancestors of horses lost toes. The modern horse, Equus caballus, evolved on the North American continent. The Spanish brought horses back to North America in the 1500s. Stray horses became known as mustangs, from the Spanish word mesteno. The Bureau of Land Management estimated 85,466 wild horses and burros on its lands nationwide as of March 1, 2026.
Scientists use DNA to work out where horses came from. A 2021 ancient-DNA study found that today's domestic horses were first domesticated in the Pontic-Caspian steppes, northern Caucasus, around 2200 years BCE. The study analysed the genomes of 273 horses that lived between 50,000 and 200 years BC. DNA showed that the 5,500-year-old horses from Botai, Central Asia, were not the ancestors of modern domestic horses. Przewalski's horses live in groups with several mares, a dominant stallion, and their young. They disappeared from the wild, and the last were seen in the late 1960s. Later they were reintroduced to Mongolia. A 2018 DNA study suggested that Przewalski's horses descend from early domestic Botai herds that escaped, rather than from horses that were never tamed. People ride horses, and a rider should wear a helmet every time and have a grown-up instructor nearby.
Horses can doze while standing up, and the figures show how much they do it. Horses spend about 80% of their time standing, even during light sleep, and adult horses sleep only 2.5 to 5 hours a day, with 80% of that sleep in a standing position. Horses are big animals, since an adult can weigh from 227 to 900 kg and stand 0.9 to 1.7 meters tall. Special tendons and ligaments let a standing horse stay upright without using much muscle effort. Wild horses live in herds of one or two stallions, a group of mares, and their foals, and horses are prey animals that depend on running away to stay safe. In a herd, some horses lie down while at least one stays standing to watch for danger.
Words to know
- gestation: pregnancy length
- colostrum: first milk
- alert: ready to act
- genomes: full DNA sets
- mustangs: stray horses
