Horses come in many sizes, and people have a special unit to measure them. A horse's height is measured in hands. Each hand is 4 inches, and the height is taken at the withers. An adult horse can stand 0.9 to 1.7 meters tall. Animals of the horse family that are less than 14.2 hands tall at the withers are classified as ponies. The Shetland is a small pony with a maximum height of 46 inches (11.6 hands). Draft horses are heavy horse breeds that stand from 15 to more than 18 hands tall. They can weigh more than 2,000 pounds.
Draft horses were the workhorses used for agriculture and for hauling freight in days gone by. The strength and size of the Shetland pony made it ideal for work in the mines in England and Scotland. Horses have natural gaits, which are the ways they move. These are the walk, trot, canter (or lope), gallop, and back. The gallop looks like a faster canter, but it is a different gait with four beats. 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. It grows about 1/4 to 3/8 of an inch a month, and it must be worn or trimmed off.
Horses are grazers that mostly eat grass, and they naturally graze for 12 to 16 hours a day. Their cheek teeth are tall-crowned and specialized for grazing. 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. It lived from around 55 million years ago to around 45 million years ago. Hyracotherium had 4 toes on each front foot and 3 toes on each hind foot. Over millions of years the ancestors of horses lost toes.
A horse today stands on a single toe on each foot, and the toe is covered by a hoof. The modern horse, Equus caballus, evolved on the North American continent. The Spanish brought horses back to North America in the 1500s. Most wild horses and burros living today descend from animals released or escaped from people such as Spanish explorers. Stray horses became known as mustangs, from the Spanish word mesteno.
Scientists studied the DNA of ancient horses to learn where today's 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 DNA 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. A 2018 DNA study suggested that Przewalski's horses, which live in groups with several mares, a dominant stallion, and their young, 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.
Przewalski's horses went extinct in the wild, and the last were seen in the late 1960s, but they were reintroduced to Mongolia. Wild horses live in herds of one or two stallions, a group of mares, and their foals. Horses are prey animals that depend on running away to stay safe. Horses can doze while standing up, and 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.
Words to know
- withers: top of shoulders
- gaits: ways of moving
- eohippus: dawn horse
- mustangs: stray horses
- domesticated: tamed for people
