# How Do Horses Sleep? Standing Up, Lying Down, and Sleep Deprivation Horses sleep both standing up and lying down, and they need both. The stay apparatus lets a horse doze upright for short stretches, but rapid eye movement (REM) sleep, the deepest and most restorative phase, requires the horse to lie flat on its side. A healthy adult horse sleeps roughly 3 to 5 hours in a 24 hour period, and only a small fraction of that, well under an hour, is true REM sleep. That small REM window is the part owners most often overlook. A horse that never lies down is not simply a horse with odd habits. It is a horse at risk of sleep deprivation, and severe sleep deprivation can cause uncontrolled collapse. Understanding how horse sleeping works, how long do horses sleep, and why do horses lie down gives you a practical way to judge whether your horse's rest is normal or a warning sign. This article is educational and is not a substitute for veterinary diagnosis or treatment. ## The Short Answer: Standing Dozing Versus Lying Sleep Horse sleeping is polyphasic, meaning horses sleep in multiple short bouts across the day and night rather than in one long block [1]. Sleep divides into two broad phases. Non-rapid eye movement (NREM) sleep can happen while the horse is standing. Rapid eye movement (REM) sleep cannot. The distinction matters because REM sleep is the phase tied to the deepest restoration. Recumbency, lying down, is a prerequisite for a horse to achieve REM sleep and complete a full sleep cycle [2]. So the answer to "do horses sleep standing up" is yes, but only partially. Standing sleep covers light NREM dozing. Lying sleep covers the REM phase the horse cannot get any other way. A practical rule of thumb from equine welfare research is that horses need a minimum of about 30 minutes of recumbency per 24 hours to perform a minimal duration of REM sleep [3]. That is a floor, not a target. Most healthy horses lie down for considerably longer, and the range across individuals is wide. ## How the Stay Apparatus Lets a Horse Doze Standing The reason a horse can sleep standing up at all comes down to anatomy, not willpower. Horses evolved as prey animals on open plains. A horse that had to lie down fully to rest would be vulnerable for long stretches. Instead, horses developed a passive supporting system in the limbs that lets them lock joints in place and rest while upright. This system is commonly called the stay apparatus. It allows the horse to stand with minimal muscular effort. The horse can relax, lower its head, close its eyes, and drift into light sleep without its legs buckling. This is why you can walk past a paddock at night and see horses standing motionless with drooping heads. Standing rest is real rest, and it is the most common resting posture. In one study of stabled horses, standing rest and sternal lying (lying on the chest with legs tucked) did not differ significantly across bedding types, while lateral lying (flat on the side) did [4]. That tells you standing rest is a baseline behavior that horses perform regardless of comfort conditions. It is the easy option. The catch is that the stay apparatus only supports NREM sleep. It cannot deliver REM sleep. When a horse enters REM sleep, the muscles go slack, and a standing horse would collapse. The body solves this by making REM sleep dependent on lying down. The horse must be recumbent, either sternal or lateral, to reach that phase [2][1]. ## Why REM Sleep Requires Lying Down REM sleep is the phase where the brain consolidates memory and where the body does much of its deeper recovery. In horses, as in people, this phase involves muscle atonia, a near-total loss of muscle tone. A standing horse simply cannot hold itself up during REM sleep. Lateral recumbency, lying flat on the side, appears to be the posture most strongly associated with full REM sleep. In the bedding study, lateral lying was the behavior most sensitive to environmental conditions, and it was observed less frequently when sawdust was used as bedding compared with other materials [4]. Sternal lying, by contrast, was more stable across conditions. This suggests lateral lying is the posture horses reserve for the deepest rest and the one they are most selective about. The link between recumbency and REM sleep is not theoretical. It is the basis for using lying time as a welfare indicator. A horse that lies down for very short periods is likely failing to complete sleep cycles, and that failure has measurable consequences [2]. ## How Long Do Horses Sleep? Total sleep in horses is short by human standards. A typical adult horse sleeps about 3 to 5 hours per 24 hours, spread across many short bouts. Of that total, only a small portion is REM sleep, generally well under an hour. Recumbency time, the time actually spent lying down, is the measurable proxy for REM sleep opportunity. In a study of 83 horses at an animal sanctuary, recumbency times ranged from 0 to 319 minutes per day, with an overall mean of about 67 minutes [2]. That is a little over an hour of lying time on average, and it varied enormously between individuals. The same study broke down the daily time budget. Horses spent about 75.6 percent of the day standing and about 19.1 percent in locomotion [2]. Lying filled the remainder. So even a horse that lies down for a full hour is lying for only about 4 percent of its day. Several variables shift these numbers. Age and chronic lameness did not significantly change recumbency times in that sanctuary population [2]. What did change lying behavior was the environment. Space, bedding, and social conditions all influence how long a horse is willing to stay down. ### A Day in the Life: Time Budget at a Glance | Activity | Approximate share of 24 hours | Notes | |--|--|--| | Standing | About 75 percent | Includes standing rest (NREM dozing) and waking activity [2] | | Locomotion | About 19 percent | Walking, turnout movement, exercise [2] | | Lying (recumbency) | Variable, often around 1 hour, range 0 to 319 minutes | Required for REM sleep [2] | | Total sleep | About 3 to 5 hours | Polyphasic, spread across day and night [1] | | REM sleep | Well under 1 hour | Requires recumbency [2][3] | The table shows why lying time is such a small but critical slice of the day. A horse can lose almost all of its REM sleep while still looking like it is resting most of the time. ## Do Horses Lie Down? Normal Recumbency Behavior Yes, horses lie down, and a healthy horse should. Owners sometimes worry when they see a horse flat out on its side, but lateral recumbency is normal and expected. It is the posture that supports the deepest sleep. Recumbency is not evenly distributed. Horses lie down more at night than during the day. In a study of young riding horses, lying duration at night was dramatically longer than during the day, by a factor of more than 11 [5]. The number of lying bouts was somewhat higher during the day, but the total time spent down was concentrated in the overnight period. Sternal lying and lateral lying are both normal. Sternal lying, on the chest, is a lighter posture and is more tolerant of imperfect conditions. Lateral lying, flat on the side, is the deeper posture and is more sensitive to bedding and space [4]. A horse that lies down regularly, gets up easily, and shows no distress is behaving normally. The concern arises when a horse stops lying down, lies down for very short periods, or struggles to rise. ## The Herd Factor: Sentinel Behavior and Social Safety Horses are herd animals, and sleep reflects that. In a group, horses do not all lie down at once. Some remain standing while others are recumbent, effectively acting as sentinels. This staggered pattern means at least one horse is alert while others sleep. This behavior has real consequences for individual horses. A horse that feels socially insecure may be reluctant to lie down, because lying down is when a horse is most vulnerable. Social and spatial environment changes during the day can carry over into the following night's recumbency. In the study of young horses, lying behavior shifted with changes in whether the horse was alone indoors, alone outdoors, or paired outdoors, though not all of these differences reached statistical significance [5]. The practical takeaway is that social stress and environmental insecurity can suppress lying time even when the physical stall is comfortable. A horse that is low in the herd hierarchy, newly introduced to a group, or housed alone may lie down less than a settled horse in a stable group. ## What Affects How Long a Horse Lies Down Lying time is not fixed. It responds to the horse's environment, comfort, and health. The research points to several factors that reliably change how long and how often a horse lies down. ### Bedding Type and Comfort Bedding matters, and it matters most for the deepest sleep posture. In the stabled horse study, lateral lying duration, bout number, and maximum bout length were greater when coconut husk bedding was used compared with sawdust [4]. Standing rest and sternal lying did not differ across bedding types, which means bedding primarily affects the horse's willingness to lie flat out. Horses also show a genuine preference for bedding. In preference testing, horses preferred bedding, especially when lying down [6]. Softness of the lying surface is a measurable property, and objective methods have been developed to assess it, with sawdust among the softest materials tested in a livestock bedding comparison [7]. The relationship between softness and lying comfort is intuitive, and the bedding preference data support it. Bedding also affects air quality, which is a separate welfare concern. So bedding choice is a balance between comfort, hygiene, and respiratory exposure. ### Space Allowance Space is one of the strongest drivers of lying behavior in group-housed horses. In a study of 38 horses across 8 groups, total recumbency per 24 hours increased as the dimensions of the littered lying area increased [3]. When no litter was provided at all, recumbency occurred only rarely, and most horses lay down for less than 30 minutes per 24 hours [3]. A separate study compared lying halls with 8, 15, and 18 square meters per horse. Horses spent longer in sternal and lateral recumbency in the hall with 18 square meters per horse than in the hall with 8 square meters per horse, and they used the larger lying hall more overall [9]. More space translated into more lying. The message for owners is direct. Cramped or litter-free lying areas suppress recumbency, and suppressed recumbency means suppressed REM sleep. ### Pain and Lameness Pain can interfere with lying down, even when the physical environment is adequate. Difficulty lying down or getting up is a recognized warning sign. In a large survey of Nordic horse owners, difficulties lying down or getting up were strongly associated with suspected sleep disturbances, with an adjusted odds ratio of 16.33 [10]. Current illness or injury was also associated with suspected sleep disturbances [10]. Interestingly, the sanctuary study found that chronic lameness due to orthopedic disease did not significantly reduce recumbency times in that population [2]. This does not mean pain is irrelevant. It means the relationship is more complex than a simple rule, and some horses with chronic conditions still lie down normally while others do not. ### Social and Environmental Stress Social stress, housing changes, and insecurity can all reduce lying time. The young horse study showed that recumbency patterns shifted with the social and spatial conditions the horses experienced during the day [5]. Environmental factors reported by owners, including hard and dry lying surfaces, were associated with suspected sleep disturbances [10]. A horse that feels unsafe, whether because of herd dynamics, a new environment, or a hard surface, is less likely to commit to the deep lateral recumbency that REM sleep requires. ## Sleep Deprivation in Horses: What Happens Sleep deprivation is the consequence of insufficient recumbency. When a horse cannot or will not lie down long enough, it cannot complete REM sleep cycles, and the deficit accumulates. The clearest sign of severe sleep deprivation is collapse. A horse that has been deprived of REM sleep can become so sleep-deprived that it collapses uncontrollably, which carries a real risk of injury [5]. This is sometimes described as REM-deficiency collapse. The horse may suddenly buckle and go down, often during a period when it would normally sleep. The cognitive effects are also measurable. In a controlled study of ten Lusitano dressage horses, researchers deprived the horses of REM sleep by preventing sternal or lateral recumbency for three consecutive days, a total of 72 hours [1]. The sleep-deprived group showed a tendency toward needing more time to solve spatial memory tasks, with a p-value of 0.0839 [1]. That is a trend rather than a definitive result, but it points toward a real cognitive cost. The welfare implications are serious. Inability to lie down due to environmental insecurity or pain results in REM sleep deficiency, which can cause substantial impairment of welfare and health [2]. Sleep deprivation is not a minor inconvenience. It is a welfare problem with physical and behavioral consequences. ## REM-Deficiency Collapse Versus Narcolepsy Collapse in a horse has several possible causes, and two of them are easy to confuse. REM-deficiency collapse results from sleep deprivation. Narcolepsy is a neurological disorder. They can look similar to an owner watching from a distance, but the underlying mechanisms differ. REM-deficiency collapse happens because the horse has not been able to achieve REM sleep for long enough. The brain eventually forces the transition, and the horse goes down involuntarily. The horse is typically trying to sleep and simply cannot stay upright. The fix is to identify and remove the barrier to recumbency, whether that is pain, an uncomfortable surface, insufficient space, or social stress. Narcolepsy is a disorder of sleep-wake regulation in which the horse may collapse or become suddenly drowsy without the same recumbency deficit. A veterinarian distinguishes these conditions through history, examination, and observation. The distinction matters because the management is different. Sleep deprivation is addressed by fixing the environment and any underlying pain. Narcolepsy is a medical condition that requires veterinary diagnosis and management. Owners who see a horse collapse should treat it as a veterinary concern. The history of how often the horse lies down, whether it has been unable to lie down, and whether it shows daytime drowsiness all help the veterinarian sort out the cause. ## Recognizing Sleep Problems: Warning Signs Several signs in the owner survey were strongly associated with suspected sleep disturbances [10]. These are practical things an owner can watch for. - The horse is not seen lying down. - Nightly injuries of unknown origin. - Loss of balance or unexpected falls. - Daytime drowsiness. - Difficulties lying down or getting up. - Current illness or injury. - Hard and dry lying surfaces in the environment. The strongest single association was loss of balance or unexpected falls, followed by not being seen to lie down and difficulties lying down or getting up [10]. Age and withers height were also associated with suspected sleep disturbances, meaning older and taller horses were somewhat more likely to be affected in that survey population [10]. The survey found that about 5 percent of respondents suspected their horse had sleep disturbances [10]. That is a meaningful minority, and it suggests sleep problems are underrecognized rather than rare. ## Practical Management for Better Horse Sleeping Improving horse sleeping comes down to removing the barriers to recumbency. The research supports several concrete steps. ### Provide a Comfortable, Deep Lying Surface Bedding type affects lateral lying, the deepest sleep posture [4]. Horses prefer bedding when lying down [6], and surface softness is a measurable property that can be assessed objectively [7]. A deep, supportive, clean lying surface encourages the horse to commit to recumbency. Keep in mind that bedding also affects air quality. Wood shavings were associated with higher ammonia, dust, endotoxin, and fungal levels than biocompost in one comparison, while biocompost had higher counts of certain bacteria and actinomycetes [8]. Balance comfort against respiratory hygiene, and keep bedding clean and dry. ### Give Enough Space to Lie Down Space allowance directly changes lying time. More littered lying area increased total recumbency in group-housed horses [3], and larger lying halls increased both recumbency and overall use of the lying area [9]. When no litter was provided, most horses lay down for less than 30 minutes per day, which is below the minimum needed for even minimal REM sleep [3]. For group-housed horses, the lying area is a limited resource. Make sure it is generous enough that lower-ranking horses can still find a spot. ### Address Pain and Lameness Difficulty lying down or getting up is a strong warning sign [10]. If your horse struggles to rise, shows reluctance to lie down, or has a current injury, that needs veterinary attention. Pain that interferes with recumbency will interfere with REM sleep. ### Reduce Social and Environmental Stress Social and spatial conditions during the day carry into the night's recumbency [5]. A horse that feels secure in its group and its environment is more likely to lie down fully. Pay attention to herd dynamics, introductions, and housing changes, and give horses time to settle. ### Watch the Night Because most lying happens at night [5], owners who only see their horses during the day may miss the problem entirely. Consider how you can observe nighttime behavior, whether through cameras, sensor technology, or careful morning checks for signs of injury or bedding disturbance. Wearable sensor technology can identify horses with low recumbency times who are at risk for REM sleep deficiency [2]. ## What Is Still Uncertain Equine sleep research is still developing. Several questions remain open. The total recumbency time in the Lusitano study was lower than previously reported in horses, which suggests that normal ranges may vary by population, management, and measurement method [1]. A 48 hour recording period appeared long enough to characterize the sleep patterns of stalled horses in that study, but the authors noted that future work could deepen understanding of sleep requirements and how environmental changes affect them [1]. The relationship between chronic pain and recumbency is not fully resolved. The sanctuary study found that chronic orthopedic disease did not significantly reduce recumbency times, which was unexpected [2]. More work is needed to understand which painful conditions actually suppress lying and which do not. The cognitive effects of sleep deprivation are suggested but not firmly established. The spatial memory finding was a statistical trend rather than a definitive result [1]. Larger and longer studies would help clarify how much sleep loss a horse can tolerate before performance and welfare suffer. ## Limitations and When to Contact a Veterinarian This article covers general principles of horse sleeping. Individual horses vary, and a veterinarian who examines your horse is the right person to judge its specific situation. Contact a veterinarian if your horse is not seen lying down, shows daytime drowsiness, has unexplained injuries or falls, has difficulty lying down or getting up, or collapses. Collapse is always a veterinary concern, whether it stems from sleep deprivation or another cause. Seek veterinary care promptly if your horse has a current illness or injury that seems to be interfering with rest. If you suspect a sleep problem, gather useful information before the visit. Note how often the horse lies down, whether it lies flat on its side or only on its chest, how easily it rises, and what the lying surface and space are like. This history helps the veterinarian distinguish sleep deprivation from other conditions and identify the barrier to recumbency. ## Frequently Asked Questions ### Can horses sleep standing up? Yes, horses can sleep standing up, but only for light NREM sleep. The stay apparatus locks the limbs so the horse can doze upright without its legs collapsing. REM sleep, the deepest phase, requires the horse to lie down because the muscles go slack [2][1]. ### How long do horses sleep? Horses sleep about 3 to 5 hours per 24 hours, spread across many short bouts. Only a small fraction of that is REM sleep, generally well under an hour. Recumbency time in one large study averaged about 67 minutes per day, with a range from 0 to 319 minutes [2]. ### Do horses lie down to sleep? Yes, horses lie down to achieve REM sleep. Recumbency is a prerequisite for REM sleep and for completing a full sleep cycle [2]. Horses need a minimum of about 30 minutes of recumbency per 24 hours for even minimal REM sleep, and most healthy horses lie down for longer [3]. ### Why do horses sleep standing up? Horses evolved as prey animals, and standing rest lets them stay ready to flee while still getting light sleep. The stay apparatus supports the body with minimal muscular effort, so the horse can relax upright. This works for NREM sleep but not for REM sleep [2]. ### What happens if a horse does not lie down? A horse that cannot lie down will develop REM sleep deficiency. Severe sleep deprivation can cause the horse to collapse uncontrollably, which risks injury [5]. REM sleep deficiency can also cause substantial impairment of welfare and health [2]. ### How can I tell if my horse is sleep deprived? Warning signs include not being seen lying down, daytime drowsiness, unexplained injuries, loss of balance or falls, and difficulty lying down or getting up [10]. A horse that collapses may be severely sleep deprived. These signs warrant veterinary evaluation. ### Does bedding affect how well a horse sleeps? Yes. Lateral lying, the deepest sleep posture, was greater with some bedding materials than others, and horses preferred bedding when lying down [4][6]. Hard and dry surfaces were associated with suspected sleep disturbances in an owner survey [10]. ### How much space does a horse need to lie down comfortably? More space supports more lying. Total recumbency increased as the littered lying area increased, and horses spent longer lying in a hall with 18 square meters per horse than one with 8 [3][9]. When no litter was provided, most horses lay down for less than 30 minutes per day [3]. ## Related Articles - [How Long Do Horses Live? Lifespan and Senior Care](/knowledge/veterinary-medicine/equine-care/horse-lifespan) - [Miniature Horse Care Guide](/knowledge/veterinary-medicine/equine-care/miniature-horse-care) - [Horse Blanketing: When and How](/knowledge/veterinary-medicine/equine-care/horse-blanketing-guide) - [Senior Horse Care Guide](/knowledge/veterinary-medicine/equine-care/senior-horse-care) - [How To Groom A Sensitive Horse](/knowledge/veterinary-medicine/behavior/how-to-groom-a-sensitive-horse) - [Horse Trailering Stress](/knowledge/veterinary-medicine/equine-care/horse-trailering-stress) - [What Is a Group of Horses Called? Herds, Bands, and Horse Society](/knowledge/veterinary-medicine/equine-care/what-is-a-group-of-horses-called) - [Thoroughbred Horse: Traits, Off-Track Care, and Health Problems](/knowledge/veterinary-medicine/equine-care/thoroughbred-horse-breed-guide) - [Roan Horse: Red, Blue, and Bay Roan Color and Genetics](/knowledge/veterinary-medicine/equine-care/roan-horse-color-genetics-and-care) ## Sources 1. [Sleep Pattern Interference in the Cognitive Performance of Lusitano Horses.](https://pubmed.ncbi.nlm.nih.gov/38275793/) 2. [Recumbency as an Equine Welfare Indicator in Geriatric Horses and Horses with Chronic Orthopaedic Disease.](https://pubmed.ncbi.nlm.nih.gov/34827921/) 3. [Space Allowance of the Littered Area Affects Lying Behavior in Group-Housed Horses.](https://pubmed.ncbi.nlm.nih.gov/28326309/) 4. [Effects of bedding material on the lying behavior in stabled horses.](https://pubmed.ncbi.nlm.nih.gov/24833955/) 5. [Comparing lying behaviour of young riding horses on days in an individual indoor box, on an outdoor paddock alone, or in pairs and in the following night.](https://pubmed.ncbi.nlm.nih.gov/38163442/) 6. [Animal behavior and animal welfare.](https://pubmed.ncbi.nlm.nih.gov/2061151/) 7. [Evaluation of an Accelerometer-Based Device for Testing the Softness of Bedding Materials Used for Livestock.](https://pubmed.ncbi.nlm.nih.gov/36433509/) 8. [Suitability of biocompost as a bedding material for stabled horses: respiratory hygiene and management practicalities.](https://pubmed.ncbi.nlm.nih.gov/17378441/) 9. [Horses' Use of Lying Halls and Time Budget in Relation to Available Lying Area.](https://pubmed.ncbi.nlm.nih.gov/34827946/) 10. [Risk factors associated with owner-reported sleep disturbances in Nordic horses.](https://pubmed.ncbi.nlm.nih.gov/40704824/)