Sleep is a natural and crucial process that can be observed in many organisms; it plays many important roles in the body. It is a functional state of the central nervous system that periodically appears and disappears according to the diurnal rhythm. There is an abolition of consciousness and immobility. Sleep in horses is necessary to regenerate and repair the brain cells and muscles. During a sleep cycle, the body also produces hormones, such as growth hormone or melatonin, that help the body maintain homeostasis.
Horses have different sleep cycles and degrees of rest – from power naps and light sleep to a slow-wave sleep (SWS) and a rapid eye movement REM sleep. Sleep deprivation can result in numerous sleep disorders in a horse. In this article, you will find 5 of the most interesting facts about the horse’s sleep.
1. How do horses sleep?
Slow wave sleep - deep sleep
There are four different rest stages in horses: inactivity, proper rest, nap, and proper sleep. When resting in a standing position, the horse will rest only one hind leg, with the other hind limb relaxed. How the horse will sleep depends on the situation and external factors. Horses who sleep while standing up is a picture seen frequently in a barn. This method allows a horse to go into a slow-wave sleep (SWS) during which the legs are locked in place, eyes are half closed, ears slightly dropped, and the neck muscles relaxed. A second method of sleep includes lying down; this allows a horse to reach the REM deep sleep state and gives rest to the musculoskeletal and skeletal systems. While lying down, horses have the proper sleep needed for body regeneration.
When do horses sleep standing up and why?
Unlike humans, many horses sleep standing up when they don’t feel safe, or they need to stay alert. Horses are prey species, meaning that in the wild, they are in constant danger of getting attacked by a predator. Thus, sleeping in a standing-up position allows them to react quicker and escape the danger. Sleeping this way means horses can rest without risking their life. In case of loud noises and danger, a vigilant and alarmed horse can alert the whole herd, increasing the chances of escape and in consequence saving its and other herd members' lives.
There are many reasons why horses sleep standing up. The first one is connected with their anatomy and needs. While for us it sounds painful, a horse’s heart and circulatory system are adapted to a standing position; this facilitates blood circulation and has a positive impact on the horse’s body. Additionally, the horse’s skeletal system has a special function that locks the legs, especially the back patella. This amazing body feature allows the horse to sleep while standing up without exerting its muscles. The whole system is called stay apparatus and can be divided into two types:
The front limb stay apparatus – is responsible for keeping the upright position of the front limbs; the body weight shifts toward the head.
The pelvic limb stay apparatus – is responsible for locking the hindlimbs. It contains fewer locking points, which allows a horse to shift its weight from one leg to the other.
When does the horse sleep while laying down and why?
Horses tend to sleep while lying down when they feel safe and have favorable external factors. Every herd has a system that prevents all the horses from sleeping at the same time; while some are sleeping others are keeping a watch. When horses sleep standing, it’s impossible for them to reach the REM sleep state since it requires full muscle relaxation. The laying position allows the horse to fully regenerate its body and relax. Some horses lay down to sunbathe. However, you should be alarmed when a horse is lying down for more than 45 minutes. Lying down for too long might indicate health problems or result in colic and sleep problems in the future.
2. How long do horses sleep?
The duration of sleep depends on the horse’s age, health, and lifestyle. How long do horses sleep? On average, horses sleep from 5 to 7 hours every day, usually between 8 pm and 5 am. An adult horse will sleep less than a foal. Healthy horses spend from 30 minutes to 3 hours sleeping every day, while young horses and foals require a bit longer REM sleep to develop properly and regenerate. Foals, during the first weeks of their lives, sleep almost half a day, while foals up to 3 months spend almost 80% of their day sleeping. This allows them to replenish their energy and gain more strength needed during the most intense growth period. Older horses often sleep more frequently but for shorter periods. This doesn’t affect their overall health.
Duration of REM sleep - deep sleep
REM (rapid eye movement) is one of the sleep stages that is observable in most mammals including humans and horses. During the REM sleep state, the brain becomes more active, the eyes move rapidly while the control of muscles disappears. It’s an extremely important sleep stage for the proper development and health of a horse. Because of this, foals require more REM sleep than adult horses.
Adult horses are in REM sleep state for about 20% of their whole sleep time and it lasts from a few minutes to half an hour. Its short time is connected with the anatomy of the animal. In this state of sleep, horses lay down. However, they can lie down only for a maximum of 45 minutes. Lying down too long will stop the blood flow to all the important organs. During the REM sleep stage, horses often present signs of agitation such as ear movements, blinking, or bouncing. So don’t worry, all those behaviors are typical for this deep sleep stage.
The deep sleep stage (REM) is extremely important for the proper functioning of the body because it affects the regeneration and repair of brain cells; the process of memory consolidation also takes place during this stage. During this sleep stage, horses reinforce all the newly acquired information. A horse that cannot fall into REM sleep might have problems with learning new things, concentrating, and have a worsened mental state.
What if a horse doesn’t sleep a lot?
If a horse won’t have enough sleep, especially enough REM sleep, then it might show signs of tiredness such as sluggishness, excessive daytime drowsiness, and reduced responsiveness to the environment. Some horses become easily irritable, aggressive, or apathetic due to sleep deprivation. Additionally, a horse might have an increased susceptibility to diseases such as respiratory infections or gastrointestinal disorders. That’s why it is so important to allow a horse enough time for a good sleep; this will keep a horse happy and healthy.
Sleep deprivation might be a result of many things. The most common cause is stress, isolation from the herd, change of environment, pain, or lack of adequate sleeping space and sense of security.
3. Do horses sleep with their eyes open?
Whether a horse sleeps with its eyes closed or open depends on the sleep stage. When a horse sleeps while standing up, it goes into the SWS stage during which the eyes are half closed. This is possible, thanks to the third eyelid that protects the horse’s eye from injuries and drying up. This allows them to be alert and react quickly in case of danger. When a sleeping horse lies down, it goes into the REM sleep stage, during which its eyes are completely closed, the body fully relaxed, and the animal gets the deepest rest.
4. Do horses dream?
Horses can experience dreams during the REM sleep stage when they are lying down. This is rather unlikely in horses that rest standing. Studies that observed horses’ eye movements and brain activity during sleep concluded that horses can create dreams from their imagination and recreate events that happened in their lives.
5. Where do horses sleep?
When a horse chooses a place for a nap, it’s never random. Studies have shown that horses kept in a pasture sleep more than horses kept in a barn. A sleeping place is always chosen strategically. Usually, it’s an open space that allows a quick escape and good visibility of the surroundings. The feeling of safety is a key factor for a sleepy horse.
Horses are herd animals, so they feel the best when they are among other horses. In a herd, there is never a case that all members sleep at the same time – there is always one that keeps watch over the herd and alerts them in case of danger. Foals are another example of how important a sense of security is for horses. They can sleep half a day because either their mother or another herd member watches over them.
Most horses rest on hard surfaces that are free of moisture and mud. This is especially true for older and sick horses, as well as those that have problems with lying down and standing up. Because of that, it is extremely important to ensure your horse has a place with dry bedding, good sunlight, and proper ventilation.
Summary
Proper sleep hygiene is crucial for a horse’s health. Horses sleep standing or lying down. A horse goes through a few stages of sleep divided into REM and NREM. During sleep, the body goes through various processes such as regeneration and repairment of cells, hormone production, memory consolidation, and many others. Lack of sleep, or worse, sleep deprivation might lead to numerous negative consequences, so it’s crucial to supply your horse with proper resting conditions and the opportunity to sleep an adequate number of hours.
Proper sleep is extremely important for the horse’s health, but do not forget about an adequate diet. Visit our section: HORSE FEED & SUPPLEMENTS.
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