How horses sleep: What does your horse need to sleep well? Maybe not what you think, say equine-behavior experts.
By Elaine Pascoe - Practical Horseman September, 2000

You're at a show, and it's almost time to warm up for your next class. Butterflies are starting to flap up a storm in your stomach. You glance over at your horse. Is he feeling the excitement?

Nope. He's standing next to you with eyes closed and head hanging. How could he sleep at a time like this?

A comfortable bed, darkness, privacy, and eight hours of peace and quiet-that's what you need to sleep well. But your horse's needs are very different. Knowing about those differences can help you ensure that he gets the rest he needs.

"Horses have sleep patterns typical for prey species that evolved on open plains," says Sue McDonnell, PhD, head of the Equine Behavior Lab at the University of Pennsylvania's School of Veterinary Medicine. There isn't a huge body of research on equine sleep, she notes. But over the past twenty years or so, she's gathered detailed data on the daily behaviors--including sleep patterns--of stabled and feral horses in a wide range of settings throughout the world. Here, she and two other equine-behavior experts will share their insights--so read on to learn your horse's sleep secrets...and what he needs to sleep best.

To Sleep, Perchance to Flee

Not every horse falls asleep waiting around at a show, but all horses can sleep standing up. Your horse has a sort of internal hammock-a system of tendons and ligaments called the stay apparatus. This system lets him lock his legs in position so (unlike you) he can relax his muscles and doze off without keeling over. Even when he's not sleeping, he uses the stay apparatus to rest muscles and reduce fatigue.

Being able to sleep standing up is a great advantage for a prey animal. If a mountain lion comes creeping through the underbrush, the horse can be off and running without wasting precious seconds struggling to his feet. Horses plan for a quick getaway in choosing resting places, too. Out in the open, they go for sheltered areas but position themselves to get out fast--butts to the windbreak, heads pointing toward a likely escape route. "They're like volunteer firemen who back their cars into parking spaces so they can pull out fast," Sue McDonnell says. In many cases, even horses in box stalls rest standing toward the back of the stall, facing the door.

Down Time

Even though they're able to snooze standing, horses apparently need to lie down for rest and sleep at least some of the time. In fact, scientists think horses must lie down to go into deep stages of sleep. Like humans and many other animals, horses experience both slow-wave sleep (SWS) and rapid-eye-movement (REM) deep sleep. (SWS is characterized by slow, synchronized waves of electrical activity in the brain as recorded by electroencephalography. REM sleep is characterized by jerky eye movements and rapid, disorganized brain waves.) REM sleep seems to occur mostly when the horse is stretched out flat on his side, rather than resting on his chest.

People dream during REM sleep, and it seems that horses do, too. Beneath closed lids, their eyes move rapidly back and forth. Sue McDonnell has even seen some horses move their feet as if "trotting" in their dreams. But what horses dream about is anyone's guess.

Power Naps

Studies of herds of wild and semi-wild horses show that horses take "power naps" and use the buddy system to get the rest they need while keeping safe from predators.

If you're like most people, you need a good, solid eight hours of unbroken rest every night. If you don't get it, you drag through the following day dull, drowsy, and sleep-deprived. You might assume that your horse has similar needs. But according to Sue McDonnell, horses do well with far less sleep than people.

Horses typically spend anywhere from four to fifteen hours a day in standing rest, and anywhere from minutes to several hours lying down. Only part of that is actual sleep time, taken in brief naps that last a few minutes each. The daily total sleep time for an adult horse may range from a few minutes to a couple of hours. Foals and young horses, like other youngsters, sleep more, more deeply, and more often than adults.

This pattern is another plus for a prey animal: His sleep can be interrupted repeatedly by predators and false alarms, but he'll still function. Rarely does a horse suffer from true sleep deprivation, says Sue McDonnell. The minimum amount of deep (lying-down) sleep he needs is very small--perhaps an hour in many days. Still, if he doesn't get that minimum, he eventually begins to drift off into what appears to be deep sleep while standing-and buckles at the knees.

Where you want your rest in a solid block of time, horses spread theirs out in scattered periods throughout the day and night. According to Sue McDonnell, "For any horse or group of horses, there is usually a recurrent pattern of rest and other activities," such as grazing. The pattern varies with the weather, the season and what's going on around the horse. Stabled horses, affected by the activity around them, typically get much of their sleep during the evening and early morning hours.

"Horses tend to learn the pattern of the barn," Sue McDonnell says, "and their deepest rest and sleep tend to occur soon after the busy 'people day' ends."

Buddy System

You're probably not surprised to hear that horses sleep best when they feel safe from danger. But the factors that help them feel safe may not be what you think. When you put your horse in his stall and close the door, you know he's protected. But he likely feels isolated and confined-and for a horse, isolation and confinement can be dangerous.

As part of her work at U of P, Sue McDonnell has studied the behavior of a semi-wild herd of ponies over time. She says feral horses actually sleep more than stabled horses. They also get more down time: As members of a herd, they're able to relax because one horse acts as a sentinel, standing guard while the rest snooze. "In feral groups, all individuals tend to rest together, eat together, go to water together. The young may get additional rest and sleep during grazing, with the protection of the adults." The adults share the sentinel duty, so everybody gets to lie down.

Solitary adult horses tend to get less deep sleep than horses in groups--probably because, with no sentinel on guard duty, and no other horses to help deal with danger, the solo horse feels he has to look out for himself at all times. He startles out of sleep at the slightest disturbance. In many cases you'll see horses stabled next to each other rest standing against the two sides of their shared stall wall, Sue McDonnell says--probably to take advantage of the sentinel effect.

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