Horses have a unique sleep pattern that involves both standing and lying down, reflecting their status as prey animals needing to stay alert.

How Horses Sleep

• Dozing (Light Sleep) While Standing:
  Horses spend a significant portion of their rest time dozing while standing. This is an intermediate state between wakefulness and sleep, during which they remain partially alert to their surroundings. Dozing accounts for about 2 hours daily and allows horses to rest without fully losing muscle tone or readiness to flee from danger

• Slow-Wave (Deep) Sleep:
  Horses enter a deeper sleep phase called slow-wave sleep, which can occur either standing or lying down. This phase lasts about 6 minutes per cycle and involves reduced responsiveness to the environment. It precedes REM sleep

• REM Sleep (Deepest Sleep) While Lying Down:
  The deepest sleep phase, REM (Rapid Eye Movement) sleep, can only happen when horses lie down on their side (lateral recumbency). During REM sleep, horses lose muscle tone completely and are least responsive to their environment. This phase lasts about 4 minutes per cycle and is essential for learning consolidation and overall health. Horses typically need at least 30 minutes of lying down daily to fulfill their REM sleep requirements

Sleep Patterns and Duration

• Horses sleep in multiple short sessions (polyphasic sleep), totaling about 6 hours of rest per day, including dozing and sleep phases. Sleep sessions last 15 to 40 minutes and occur mostly at night (8 p.m. to 5 a.m.) and sometimes midday

• While horses can rest standing up due to a special "stay apparatus" in their legs that locks joints and prevents muscle fatigue, they must lie down periodically to achieve full restorative sleep, especially REM sleep

Importance of Lying Down

• Horses need to lie down in a safe, comfortable environment to get enough REM sleep. Lack of suitable space, social stress, or physical discomfort can reduce lying time and lead to REM sleep deprivation, causing excessive drowsiness and health issues

In summary, horses primarily doze while standing but must lie down briefly each day to enter REM sleep, which is crucial for their well-being. Their sleep is segmented into multiple short cycles throughout the day and night, balancing rest with vigilance against predators