Why do Horses sleep standing up? Horses, like human beings, | Curiosity Tea
Why do Horses sleep standing up?
Horses, like human beings, sleep in various degrees of sleep. They can doze or take a nap and experience Slow Wave Sleep (SWS), they also need Rapid Eye Movement (REM) Sleep, the deep sleep in which dreams occur.
Horses can doze or nap in the SWS stage, while standing, this is because of a unique quality of the equine skeletal system, to lock their limbs, specifically their rear knee-caps, allowing the skeleton to hold them upright without engaging the muscles. It is possible because of a special system of tendons and ligaments and is called as the Stay Apparatus in veterinary medicine.
This mechanism has evolved in most prey-animals that live in predator rich regions. Horses due to their straight backs, cannot get up quickly if a predator approaches, before domestication horses sleeping upright gave them a swift advantage of escaping a predator compared to horses lying down to sleep. A horse will never lie down if they do not feel safe.
Horses need REM sleep, from 30 minutes - 3 hours for their healthy functioning, most often these occur post midnight. Experts say that REM sleep occurs in short intervals of 10-20 minutes, a maximum REM cycle in horses is 45-minutes. They prefer to sleep during the day, and if you see a horse lying down or a group of horses lying down, you will also observe one horse standing up, guarding others and keeping an eye out for predators.
Foals spend more time sleeping than adult horses, Older horses might have trouble sleeping because of joint issues as they age, or due to neurological disorder like Narcolepsy (a condition in which a horse suddenly falls asleep), Hypersomnia (excessive sleep or lethargy ) or REM sleep disorder (a horse wakes itself up with excessive body movements during sleep).
Other reasons for horses not lying down to sleep are stress, not enough space to sleep, discomfort of a new place or due to a new horse being introduced to the herd.
