Why do horses sleep standing up?
Horses can doze standing up thanks to a special locking system in their legs called the stay apparatus. It lets them rest without falling and run away quickly if a predator appears.
The stay apparatus is a system of tendons and ligaments that lets a horse lock the joints in its legs, especially one hind leg at a time, with little muscle effort. This allows horses to relax and enter light sleep while standing. As prey animals, being able to flee quickly from danger was important for their survival in the wild.
However, horses must lie down to get deep, rapid eye movement, or REM, sleep, because their muscles relax completely during this stage. They usually lie down for short periods, often adding up to less than an hour of REM sleep a day. In a herd, some horses stay standing to keep watch while others lie down.
Sleep needs
Adult horses typically sleep only about two to three hours in a 24-hour period, in short naps. Horses that cannot lie down because of pain or stress may become sleep-deprived and suddenly stumble or collapse.
Did You Know?
Foals spend much more time lying down and sleeping than adult horses, often stretched out flat in the sun.