The sleeping habits of horses are quite different than humans. Most human sleep is usually a long, single stretch—about eight hours in a 24-hour day. Horses doze for various periods during the day and have short bouts of deep sleep lying down in the middle of the night. Horse’s sleeping patterns change depending on their age.
Foals lie down for frequent naps and spend about half of their day sleeping until they are about three months old. As the foal gets older, the frequency of the naps becomes less, and they are more likely to stand rather than lie down. Adult horses spend more time dozing while standing up than in deep sleep lying down.
How the Adult Horse Sleeps
Mature horses most frequently rest in a standing position, but this does not provide deep, or REM, sleep. In order to fall into a true deep sleep, all skeletal muscles must be relaxed; this cannot happen when the horse is standing. However, when standing, horses will fall into a deep doze, but can wake up and become alert very quickly. This is a survival mechanism for horses, since they evolved as a prey species. But how can a horse snooze while standing? Horses have a unique anatomical mechanism in their hind legs called the stay apparatus. This allows a horse's knee cap to pop out of place and lock the hind limb in a standing position. Although it sounds painful, in horses, it's no problem at all. When dozing while standing, this stay apparatus will lock in place in only one hind leg; the other hind limb will be relaxed. Often, the horse appears to be leaning on one hip.
Most horses will lie down for deep sleep a few times each night, if they have a comfortable place to do so and feel safe. This is why it's important to provide a dry, sheltered area like a run-in shed or roomy stall, so your horse can stretch out safely for a snooze.
How Long Horses Sleep
Adult horses sleep for about three hours each 24-hour period. The length and type of sleep are affected by diet, temperature, workload, gestation, and gender. The period of each sleep phase is very brief, lasting only a few minutes at a time. Young horses tend to sleep more than mature horses. Senior horses may doze more frequently.
A dozing horse will mostly carry its weight on the two forelegs and one hind leg. One hind leg will relax with the hoof resting up on its toe. The head and neck droop, the ears are relaxed, the eyes are closed and the lower lip may droop or twitch. When horses experience deep sleep lying down, they will stretch flat out on the ground.
Horses will lie down to sun themselves, and it is not unusual for several horses to lie down at the same time for a communal sunbath on a warm spring day. Often while several horses lay down, one or two others will remain standing. This is a natural look-out behavior for the safety of the herd. Horses tend to spend less time lying down in cold snowy conditions, although on a sunny day, some will snooze stretched out in the snow. Each horse has its own sleeping habits. Some will sleep only at night while others sleep during the day as well.