Horses can sleep standing up, though they lie down for the deepest stages.

The longer version

A stay apparatus of ligaments and tendons lets a horse lock its legs and doze upright with minimal muscle work, an arrangement that suits an animal built to flee quickly. Light sleep happens easily in this posture. The mechanism involves the stifle and hock, letting the animal rest its weight on tendons rather than muscle.

Deep slow-wave sleep still requires lying down, and a horse denied the chance to do so will miss it. Because a large body resting on one side risks circulation problems, those recumbent periods are relatively short and spread through the day. Herd animals also benefit from having some members standing while others lie down, since a resting group stays easier to defend.

Where this entry sits

This collection gathers curious details about sleeping and dreaming, from nightly brain stages and body clocks to naps, yawns and unusual animal habits. It also covers how bedtime customs have changed across centuries, without offering any advice. The full list sits on the Sleep and Dreams page, where every entry is listed in order.