page_title: Horse behavior
section_title: Sleep patterns
hierarchical_section_title: Horse behavior / Sleep patterns
caption_attribution_description: Français&#160;: Cheval de race ardennaise, endormi.
context_page_description: Horse behavior is best understood from the view that horses are prey animals with a well-developed fight-or-flight response. Their first reaction to a threat is often to flee, although sometimes they stand their ground and defend themselves or their offspring in cases where flight is untenable, such as when a foal would be threatened.
  Nonetheless, because of their physiology horses are also suited to a number of work and entertainment-related tasks. Humans domesticated horses thousands of years ago, and they have been used by humans ever since. Through selective breeding, some breeds of horses have been bred to be quite docile, particularly certain large draft horses. On the other hand, most light horse riding breeds were developed for speed, agility, alertness, and endurance; building on natural qualities that extended from their wild ancestors.
  Horses' instincts can be used to human advantage to create a bond between human and horse. These techniques vary, but are part of the art of horse training.
context_section_description: Horses can sleep both standing up and lying down. They can doze and enter light sleep while standing, an adaptation from life as a prey animal in the wild.  Lying down makes an animal more vulnerable to predators.  Horses are able to sleep standing up because a "stay apparatus" in their legs allows them to relax their muscles and doze without collapsing.  In the front legs, their equine forelimb anatomy automatically engages the stay apparatus when their muscles relax.  The horse engages the stay apparatus in the hind legs by shifting its hip position to lock the patella in place.  At the stifle joint, a "hook" structure on the inside bottom end of the femur cups the patella and the medial patella ligament, preventing the leg from bending.
  Horses obtain needed sleep by many short periods of rest. This is to be expected of a prey animal, that needs to be ready on a moment's notice to flee from predators.  Horses may spend anywhere from four to fifteen hours a day in standing rest, and from a few minutes to several hours lying down.  However, not all this time is the horse asleep; total sleep time in a day may range from several minutes to two hours.  Horses require approximately two and a half hours of sleep, on average, in a 24-hour period.  Most of this sleep occurs in many short intervals of about 15 minutes each.  These short periods of sleep consist of five minutes of slow-wave sleep, followed by five minutes of rapid eye movement sleep (REM) and then another five minutes of slow-wave sleep.
  Horses must lie down to reach REM sleep.  They only have to lie down for an hour or two every few days to meet their minimum REM sleep requirements. However, if a horse is never allowed to lie down, after several days it will become sleep-deprived, and in rare cases may suddenly collapse as it involuntarily slips into REM sleep while still standing.  This condition differs from narcolepsy, which horses may suffer from.
  Horses sleep better when in groups because some animals will sleep while others stand guard to watch for predators.  A horse kept entirely alone may not sleep well because its instincts are to keep a constant eye out for danger.
caption: A draft horse sleeping while standing up
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