How Do Horses Sleep Standing Up?
Horses have a unique system of interlocking ligaments and bones in their legs, which serve as a sling to suspend their body weight without strain while their muscles are completely relaxed. Thus, horses don’t have to extent any energy consciously to remain standing-their legs are locked in the proper position during sleep.
Most horses do most of their sleeping while standing, but patterns differ. Veterinarians said it was not unusual for horses to stand continuously for as long as a month, or more. Because horses are heavy but have relatively fragile bones, lying in one position for a long time can cause muscle cramps.
While one can only speculate about why the horse’s body evolved in this fashion, most experts believe that wild horses slept while standing for defensive purposes.
Wayne O. Kester, D.V.M., executive director of the American Association of Equine Practitioners, said that in the wild, the horse’s chief means of protection and escape from predators was its speed. “They were much less vulnerable while standing and much less apt to be caught by surprise than when lying down”.
Horses can get a lot of sleep while standing up, but they lie down when they require REM sleep. Typically, the amount of REM sleep they require is very small, so they don’t need to lie down often. However, many horses lie down just because they feel comfortable or want to do so. The method by which horses stand while sleeping is called the “stay apparatus,” and it’s a system of ligaments and tendons that keep them upright with relative ease.
Horses also like using the buddy system for sleeping, where one horse watches over the others while they’re sleeping. The role of watch-horse will rotate as each member of the herd gets the sleep they need, including lying down for necessary REM sleep. Many horses adopt this kind of rotation when they’re in their home barn setting, either in a paddock or in a stall next to their regular neighbors.