Equine Rest: How Horses Sleep

Understanding how horses sleep can seem like a mystery. Fortunately, there has been a wealth of research in this area that I’ve discovered, so the mystery of equine sleep can be put to rest.

How do horses sleep? Horses need between 3 and 6 hours of sleep per day, and most of that rest will be done from a standing position courtesy of their unique ability to lock their limbs in place while their muscles relax. Horses also require daily REM sleep, which can only be achieved while lying down. This means that horses will sleep while both standing up and while lying down.

Horses, like humans, can suffer serious repercussions when sleep-deprived, and we humans should learn what we can about their sleep needs so that we can provide excellent care to our equine friends.

Keep reading to learn about why horses sleep the way they do, what allows them to sleep without using their muscles to hold up their bodies, and how to help our horses feel safe enough to lie down and get the deeper rest they need.

Do Horses Sleep While Standing Up or Lying Down?

You may have heard that horses sleep while standing up, and while that is true for the majority of their rest, that isn’t the only way that they sleep. Horses cannot get the quality of sleep that is necessary for their well-being unless they spend some of this rest time with their feet up.

Horses must lie down to get REM sleep. REM stands for “rapid eye movement” because during this stage of sleep, you may notice the eyes moving (rapidly). This is one of the stages of sleep and is when your brain is the most active.

Due to this brain activity, this is also the stage of sleep in which dreams occur. During REM sleep, important memory processing and consolidation occur. It is a vital process to brain development and the process of emotion.

Because dreaming occurs during this stage, your muscles enter a type of paralysis so that you don’t “act out” your dreams while sleeping. Therefore, if a horse were to enter into REM sleep while standing, he would likely collapse.

So while a large portion of a horse’s sleep cycle is achieved while standing, horses must lie down every day for REM sleep.

How Can A Horse Sleep While Standing?

Horses have the unique ability to remain upright while sleeping due to an arrangement of muscles, tendons, and ligaments known as the “stay apparatus,” which works together to allow an animal to remain standing with almost no muscle engagement.

This stay apparatus engages without effort on the animal’s part when the muscles begin to relax. The first fossilized evidence of this system was in the Dinohippus, an ancient ancestor of the modern horse. 

In the front legs, the stay apparatus works by turning the ligaments into “tension bands” that stabilize the knees and fetlocks. The mechanics of this system on the hind legs are slightly different, though they achieve the same result. The medial patellar ligament locks the hind kneecaps in place, preventing flexion in the stifles and hocks. 

Generally, a horse will hold their weight on three of their legs while sleeping, allowing the fourth leg to rest. Periodically, they will shift their weight unconsciously so that each leg is able to get an equal amount of downtime. 

Why Do Horses Sleep In A Standing Position?

Most animals sleep while lying down, but horses are one of the few animals that have the stay apparatus, which allows them to remain standing while sleeping. There are two important reasons for this.

Horses have evolved to have the stay apparatus because it helps to protect them from predators. It takes a lot of energy for an animal as large as a horse to rise from a recumbent position.

While they may be able to go from lying down to standing in mere seconds, those few seconds can mean the difference between life and death if there is a large predator stalking the herd. To be able to sleep while standing allows a horse to immediately bolt if there is a danger present. 

The other reason horses sleep in a standing position is because their bodies are so heavy that their blood flow is dangerously restricted in a recumbent position, and their lungs are prevented from fully inflating.

Both of these problems can quickly turn life-threatening, which is the reason that one of the first steps in aiding a downed horse, whether fallen from injury or illness, is to get the horse back into a standing position.

Horses will only lie down for up to an hour or two at a time. If your horse has been lying down longer than a couple of hours, and that is unusual for him, you’ll want to get him up. If you’re not able to get him up and alert, you will need to call your vet right away. 

How Much Sleep Does a Horse Need?

The amount of sleep a horse requires will depend on the individual. Like humans, some horses will need more sleep in order to function at the same level as other horses that may need fewer hours of sleep to thrive. The required amount of sleep an average horse needs will vary between three and six hours per 24-hour period.

The sum of a horse’s sleeping hours is not spent in one large chunk of time. Horses will nap throughout the day and night, with most of their sleep hours occurring from sundown to sunrise. Most of a horse’s daily sleep hours will occur while standing up, but at least 30-60 minutes per day need to be spent lying down for that crucial REM sleep. 

How To Help A Sleep-Deprived Horse

If your horse is not getting an adequate amount of REM sleep, he can experience both physical and cognitive exhaustion and will eventually collapse. It’s important to ensure that your horse is getting enough sleep both while standing and while lying down. 

In the wild, horses will rotate their REM sleep – a portion of the herd will lie down to sleep while one or more horses remain standing and alert to predators. Taking turns allows a horse to alert the rest of his herd to danger so that everyone can get back on their feet before the threat is close enough to cause harm. 

Domestic horses have that same need for felt safety through companionship. Even if your pasture is as impenetrable as Fort Knox, your horse may not feel comfortable enough to lie down without having a herd mate watch his back – this is especially true for horses that are new to your property.

Horses are social animals and should always have a companion, whether a pony, a donkey, or even another kind of livestock with which a particular horse may bond. A horse may also feel safer in an enclosed space to sleep – whether that be a run-in that has three sides or a barn stall.

Like you and I, horses also like to be comfortable. Horses don’t like to lie down on hard surfaces and prefer stalls with deep bedding.

While they are comfortable on both straw and shavings, it’s been shown that a horse will lie down on his side for a longer period of time, getting more sleep, on a deep bed of straw than over other material. 

If using a stall, your horse will also need enough space to feel comfortable enough to lie down. Veterinarians have documented observations of horses refusing to lie down in stalls, causing them to collapse while sleeping in a standing position, only for them to lie down and sleep comfortably once the stall walls were let out and more space was provided.

If a horse doesn’t feel he can safely and quickly rise to a standing position in a tight space, he will be reluctant to lie down.

The Unique (or Not-So-Unique?) Sleep Habits of Horses

Horses may seem unique in their ability to sleep while both standing and lying down, but they are not the only animals that boast the stay apparatus that allows them to do this. Elephants, giraffes, and cattle all have the ability to sleep while in a standing position, but like horses, they must lie down to achieve REM sleep (though elephants only need to enter into REM sleep every few days).

Flamingoes also have the stay apparatus, sleeping on not two legs, but one. I know a couple of chicken keepers who claim some of their birds stand while sleeping, but I’ve personally never seen evidence of this.

So while the ability to sleep while standing may seem foreign to us, it’s a survival mechanism that has been given to a handful of animals. Isn’t nature amazing?