Your turn
Each lab is one step from the video. Change things and see what happens.
Each lab isolates one part of the story. The models are simplified to show the idea.
Tap the buttons and see what the horses do.
Switch the horse between awake and dozing. Which clues change?
Compare an alert horse with a dozing one: head, eyes, lip and hind legs.
Tap Awake, then Dozing. Where is the head?
Tap a knee to lock or open the latch, then swap the resting leg. What happens to muscle effort?
Engage the patellar lock and shift the weight. Watch muscle effort when the stifle is locked.
Tap Lock. Then tap Swap!
A simplified side view: the far leg is drawn spread apart so you can see both.
Snap a twig. Which horse gets away first, and why?
Compare a standing start with the three-step get-up from lying down.
Tap Snap. Who runs first?
Race speeds are just for show; the order of the getting-up steps is the real part.
Pick a pose. Which kinds of sleep can the horse get?
Which sleep states does each posture allow? Note the partial REM when lying on the chest.
Tap each pose. Which one lets the horse dream?
Switch days, then tap a nap on the inner ring to see what kind it is.
Compare fragmented horse sleep with a consolidated human night; tap a bout for its posture and REM.
An example day: nap times are made up, but the totals match the study averages.
Choose how many horses share the field. Who dares to lie down?
Vary herd size: with company, horses take turns lying down while one stands guard.
Tap 1 horse, then 4 horses. Who lies down?
Horses can sleep standing up! They also lie down to sleep. They need to lie down for REM sleep, the deepest, busiest-brain kind.
A sleepy horse stands very still. Its head hangs low. Its eyes are nearly shut, and its lip droops. One back foot is lifted, with just the tip on the ground.
Horses have strong straps inside their legs. In a back leg, a little bone slides up and hooks on, like a latch on a gate. Click! The leg stays straight, and it holds the horse up. The other back leg rests. Then they swap.
Long ago, wolves hunted horses. Getting up from the ground takes a horse a long time. A standing horse can run away right away.
When a horse dreams, its body goes all floppy, like a teddy bear. A floppy horse would fall over. So to dream, it lies down, flat on its side or on its tummy.
Horses are much more likely to lie down when they feel safe. Friends take turns: some lie down, and one stays standing to keep watch. A horse all alone might not lie down, and then it gets very, very sleepy.
Want more? See why sleep is important and why cats sleep so much. ← More explainers
Horses sleep both standing up and lying down. On their feet they doze in light sleep and can even get slow-wave (deep, dreamless) sleep, because a system of tendons and ligaments called the stay apparatus holds their legs straight with hardly any muscle effort.23 But for REM sleep, the stage when the brain is busy and the muscles go slack, a horse has to lie down.12
Altogether, horses sleep only about 3 to 4 hours a day, in lots of short naps, and they usually spend just one to three hours a day lying down.14
standing: light + deep sleep · lying down: light + deep + REM
Yes, for a lot of their sleep. A dozing horse usually stands very still with its head and neck low, its eyes half closed, its ears relaxed and its lower lip drooping. The biggest clue is in the back legs: one leg is straight and carries the weight, while the other is bent, with only the tip of the hoof resting on the ground.45
That doesn't mean the horse is fully "switched off". Standing horses get light sleep and slow-wave sleep, but never full REM sleep.2 In one brain-wave study of seven horses, the share of sleep done standing ranged from about a quarter to about two-thirds, depending on the horse.1
The stay apparatus is a set of tough tendons (which join muscle to bone) and ligaments (which join bone to bone) in all four legs. When the horse relaxes its muscles, these tissues act like tight straps that keep the joints from folding, so the horse can stay upright with very little muscle effort.256
The back legs have an extra trick: a locking kneecap.
In the player above, the leg in chapter 2 is a simple diagram, not an exact anatomical drawing: bones as sticks, tendons as red straps, the kneecap as a small gold oval.
Because they are prey animals. Wild horses were hunted by predators such as wolves and big cats, and a horse's first instinct when it's scared is to run.7 A horse is big and heavy, and getting up off the ground takes time and effort: it first rolls onto its chest, then pushes up with its front legs, and then heaves up its back end. A horse dozing on its feet skips all that. As one equine specialist at Michigan State University put it, standing gives horses "a literal jump on predators".2
Horses aren't the only ones. Zebras and elephants can also sleep standing up.2 The race in chapter 3 shows the order of the getting-up steps; its speeds are just for show, not measured times.
Yes, every day, and they need to. During REM sleep the body loses muscle tone, a normal state scientists call REM atonia.1 A floppy horse can't stay on its feet, so REM only happens when the horse lies down: stretched out flat on its side, or lying on its chest while leaning heavily against something.4
| Position | Light sleep | Slow-wave (deep) sleep | REM (dreaming) sleep |
|---|---|---|---|
| Standing | Yes | Yes | No |
| Lying on the chest (sternal) | Yes | Yes, mostly | A little, if it leans on something |
| Flat on the side (lateral) | Yes | Yes | Yes |
Sources: 124. A horse lying flat usually stays down only around 15 to 20 minutes at a time.4 Foals are different: they sleep more and lie down much more than adults, and this slowly drops as they grow up.47
Much less than you. A 2022 review that pooled the horse sleep studies found an average of about 231 minutes of sleep in 24 hours, a bit under 4 hours. Studies that measured brain waves found averages between about 172 and 262 minutes (roughly 3 to 4½ hours). A typical adult human sleeps about 430 minutes, so horses sleep roughly half as much as we do.1 You'll see other figures online too: Britannica says horses lie down in short spells adding up to about 2 to 3 hours a day,3 and a Scientific American / Live Science article says adult horses can get by on as little as 5 hours of sleep.2 These figures don't all measure the same thing: time spent lying down is not the same as total sleep time.1
The 24-hour clock in chapter 5 is an example day: the nap times are made up, but its totals are set to match the study averages above.
Only a little, but it can't skip it. Across studies, horses average about 40 minutes of REM a day, around 17% of their sleep, which is a similar share to people.1 It comes in short bursts averaging under 4 minutes each, about ten of them per sleep period.1 An equine specialist at Colorado State University says a well-rested horse needs at least about 25 minutes of REM a day,2 and a veterinarian writing for The Horse puts the total at only about an hour a day.4 Want to know what REM sleep is like in people? See how dreams work.
Often, yes. Lying down means letting your guard down, so horses are much more likely to do it when they feel safe. In a herd, horses swap between lying and standing in what scientists describe as a kind of rota of lookouts.1 When several horses in a wild group lie down for REM sleep, at least one usually stays standing, probably watching for danger.2
A horse that is alone, or somewhere new or scary, is less likely to lie down at all.27
It becomes sleep-deprived, especially of REM sleep. A horse that can't or won't lie down still dozes on its feet, but it gets extremely drowsy. It may buckle at the knees or even suddenly collapse while dozing, which can cause injuries.12 This has sometimes been mistaken for narcolepsy, a sleep disorder.27 Scientists say there's still a lot to learn about how much missed sleep a horse can cope with.1
If you visit horses, go with an adult and watch from behind the fence (never stand behind a horse). Look for a resting back hoof, tipped up on its toe, often with a low head and droopy eyelids and lips: that horse is resting and may well be dozing.45 A horse lying flat and very still, maybe twitching a little, may be in REM sleep. Let it rest!
| You | Horse | |
|---|---|---|
| Total sleep | About 7 hours (adults; kids need 9–12) | About 3–4 hours |
| Pattern | One long night | Many short naps |
| Sleep cycle | About 2 hours | About 40 minutes |
| REM (dreaming) sleep | About 73 minutes | About 40 minutes, lying down only |
| Can sleep standing? | No | Yes (light + deep sleep) |
Figures from the 2022 review of horse and human sleep studies.1 Other animals have their own tricks: see how whales sleep, why cats sleep so much and why sleep is important for us.
Yes, partly. Horses can doze and even get slow-wave (deep, dreamless) sleep while standing, because a system of tendons and ligaments called the stay apparatus holds their legs straight with very little muscle effort. But they can't get REM sleep standing up, so they also need to lie down every day.
Yes. Horses lie down for their deepest rest and for REM sleep, when the muscles go slack. They lie on their chest with their legs folded, or stretched out flat on their side. Most horses spend about one to three hours a day lying down in total, in short spells.
Much less than people. A 2022 review that pooled horse sleep studies found an average of about 231 minutes, roughly 3 to 4 hours in 24 hours, with brain-wave studies ranging from about 172 to 262 minutes. It comes in many short naps, mostly at night, not one long block.
Not much, but it matters. Studies average around 40 minutes of REM a day, split into bursts of just a few minutes each. Equine specialists say a well-rested horse needs at least about 25 to 30 minutes, and REM can only happen when the horse lies down.
A dozing horse usually stands still with its head and neck low, eyes half closed or shut, ears relaxed, lower lip drooping, and one back leg bent with just the tip of the hoof resting on the ground. A horse lying flat and still, sometimes twitching its legs, eyelids or lips, may be in REM sleep.
Horses are prey animals. A big, heavy horse needs time and effort to get up off the ground, so dozing on its feet lets it run away from danger straight away. That's why horses tend to lie down only when they feel safe, often while another horse in the herd stays standing.
Not in the way we do, because the stay apparatus lets the bones, tendons and ligaments carry the weight instead of the muscles, and the horse switches which back leg it rests. But a horse that never lies down misses REM sleep, becomes sleep-deprived, and may buckle or collapse while dozing.