How do Horses Sleep Standing Up?
Every horse owner has seen their horse standing in his stable or field, head hanging, lip flapping, eyes closed. But is your horse asleep, and if so, how come he doesn’t fall over?
In this article, we answer some of the most commonly asked questions about the sleeping habits of your equine companion.
Be warned; some of the information you’ll read here is somewhat surprising!
How do horses sleep while standing up?
Well, for a start, let’s bust the urban myth that horses can sleep standing up.
In truth, horses can only snooze standing up, and there’s a big difference between snoozing and sleeping.
Like all land mammals, horses need good quality, deep sleep to function properly physically and mentally. However, horses are prey animals whose natural defense against danger is to flee. So, falling into a deep sleep could spell curtains for a wild horse that lives in an environment where he is surrounded by potential predators.
So, how do horses get the quality sleep they need?
If you watch your horse in the field, you’ll notice that, between bouts of grazing and socializing with his field mates, he spends much of his time dozing in a standing position.
How come your horse doesn’t fall over while he’s snoozing?
Horses are able to take a power nap without laying down thanks to a cool aspect of their anatomy called the “stay apparatus.” It’s thought that the stay apparatus evolved to enable early species of wild horses to survive attacks from predators.
While standing at rest, the horse is able to lock his kneecaps with tendons and ligaments that keep the joints aligned. Those soft tissues effectively lock the bones of the joint together, meaning that no additional muscular exertion is required. That allows the horse to rest while he’s standing up.
If a predator approaches or the horse is startled, he’s ready to go directly into flight mode without wasting valuable time getting to his feet. In a wild horse, that ability might just save his life!
When out in the open, horses choose their resting places carefully. Generally, wild or feral horses will select sheltered spots, standing with their backs into the wind and their heads facing toward a clear escape route. Chances are, you’ll find your domesticated dressage horse dozing with his back to the wall in his stable, facing the door.
Even when your horse isn’t sleeping, he uses his stay apparatus to rest his muscles and reduce fatigue. Some horses even doze when traveling between shows, either in your lorry, or even while on an international flight or train journey.
What about deep sleep?
So, horses can doze while standing up, but how does your horse get that really deep sleep that he needs?
Horses cannot enjoy deep sleep while they are standing. That can only be achieved when the horse is lying down. So, horses do lay down to sleep properly, although they don’t do so for very long. Why is that?
Well, first of all, horses will only lay down to sleep if they feel safe and secure in their environment. So, although your horse is unlikely to be attacked in his field or stable by a pack of wolves or a mountain lion, if he feels stressed, he will not lay down to sleep.
Consequently, if your horse’s home barn is always full of hustle and bustle, or if his paddock is right next to a noisy, busy road, or his stable is very small, he won’t feel comfortable laying down, and so he won’t get the deep sleep that he needs.
What’s the result of sleep deprivation in your domesticated dressage horse?
Horses that are unable to enjoy deep sleep for a period of weeks or even months will suffer in terms of their physical performance.
Your horse may even become irritable and resistant when he’s handled and ridden.
Your horse’s sleep patterns
In a deep sleep, horses experience similar sleep patterns to humans. Like many other mammals, including humans, horses experience slow-wave sleep (SWS) and REM (rapid-eye-movement) deep sleep.
In SWS, slow, synchronized waves of electrical brain activity occur, as recorded by electroencephalography. REM sleep produces jerky eye movements accompanied by disorganized, rapid brain waves and occurs mainly when the horse is lying stretched out flat on his side, rather than propped on his chest.
REM is the phase of sleep during which people dream, and scientists think that horses dream too. You may have seen your horse apparently trotting in his sleep, and some horses even whinny and snort, despite being deeply asleep.
Interestingly, if you observe a group of horses in a field, you’ll often see all of them lying down sleeping, bar one. As in wild horses, one animal always stays alert and on all four feet, keeping a lookout for danger while his companions get some valuable shut-eye.
Compared with the average human sleep requirement of seven or eight hours per night, a horse only needs two to three hours of deep sleep per night.
In fact, horses break up their sleep time throughout a 24-hour period. So, your horse may doze, standing up for a few minutes at a time, and then lay down for an hour or two. Added together, those sleep periods may add up to anything from a couple of hours to over 12 hours a day, depending on whether the horse is stabled, turned out, in work or not.
In general, young horses, including colts and fillies, tend to sleep for more hours than adult or aged animals. In stabled horses, the behavior of their wild cousins can be seen mimicked when animals in neighboring boxes share the same sleep patterns. Sometimes, in a barn of ten horses, nine can be seen sleeping flat out in their stables, while one horse remains awake and watchful.
There are other physiological reasons why horses do not lay down to sleep for long periods.
The longer a horse lays down, the more prone the animal is to a condition called “reperfusion injury.” Reperfusion injury occurs because horses are very large animals, and their body weight can interrupt the blood flow to certain areas of their body. That causes problems when the horse tries to stand again, and the blood flow attempts to return to normal.
As well as reperfusion injury, the muscles and nerves on the downside of the horse can be damaged due to the excessive pressure exerted by his body weight. Also, because of the effects of gravity, excess blood can pool in the horse’s lung on the downside.
That’s why the discovery of a cast horse should always be treated as an emergency situation, especially as there’s usually no way of knowing how long the animal has been down if he is not discovered until the morning.
Over millennia, the horse developed the ability to snooze while standing up, thanks to the stay apparatus, a locking mechanism comprised of ligaments and tendons that prevents the horse’s knee joints from collapsing involuntarily.
Horses also enjoy SWS and REM sleep, but this always happens when the horse is lying down flat on his side.
How often does your horse doze while he’s standing up? Does your horse dream? Share your story with us in the comments section below.
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