How do horses sleep standing up? Horses can doze while standing up. Special tendons and ligaments let a standing horse stay upright without using much muscle effort. Horses are big animals. An adult can weigh from 227 to 900 kilograms and stand 0.9 to 1.7 meters tall.

A horse uses its ears to hear. Ears pointed stiffly forward mean the horse is alert. A horse sees mostly with each eye separately, which gives it a panoramic view. 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 keeps growing. It must be worn or trimmed off. A horse can grow a whole new hoof in a year. Horses also have a mane of coarse hair along the neck.

A mare gives birth to a baby horse called a foal. She carries her foal for about 11 months, which is usually 335 to 342 days. A foal can stand up within about an hour of being born. A mare's first milk is called colostrum. It has antibodies that help protect the foal from infection.

The oldest known horse was Hyracotherium. It was a small, dog-sized animal that lived in forests and ate leaves. It had 4 toes on each front foot and 3 toes on each hind foot. Horses today are grazers that mostly eat grass.

Przewalski's horses live in groups with several mares, a dominant stallion, and their young. They eat mostly grass and some leaves. They disappeared from the wild, and the last were seen in the late 1960s. Later they were reintroduced to Mongolia.

Wild horses live in herds. A herd has one or two stallions, a group of mares, and their foals. 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. People ride horses, and a rider should wear a helmet every time and have a grown-up instructor nearby.

Words to know

• ligaments: strong body bands
• colostrum: first milk
• hoof: toe cover
• herd: horse group
• reintroduced: brought back

The short version

Horses can doze while standing up. Special tendons and ligaments let a standing horse stay upright without using much muscle effort. 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.

Quick facts

• Special tendons and ligaments let a standing horse stay upright without using much muscle effort.
• In a herd, some horses lie down while at least one stays standing to watch for danger.
• A horse stands on a single toe on each foot, and the toe is covered by a hoof.
• A mare carries her foal for about 11 months, which is usually 335 to 342 days.
• The oldest known horse, Hyracotherium, had 4 toes on each front foot and 3 toes on each hind foot.