Sleep is a constant among all animals, but not all animals sleep the same way. As it turns out, most four-legged land herbivores are capable of dozing lightly on their feet thanks to something called a “stay apparatus”, which are joints that lock in place while the creature is standing. This evolved so they could more quickly run away from predators that would try to ambush them while sleeping. To explore this strange phenomenon, here’s a list of animals that sleep standing up and why they do this.
8 Types of animals that sleep standing up
While horses are capable of sleeping standing up, they don’t do it all the time. This practice evolved because horses that could sleep standing up were better able to run away from predators in the night than those who had to get to their feet before taking off. Most horses can do the “slow wave” type of sleep standing up, and only require about three hours of sleep in 24 hours.
A horse technically needs to lay down to sleep to achieve Rapid Eye Movement (REM) sleep. During REM sleep, the horse loses all muscle tone and will collapse if they’re standing. The total REM time a horse needs is only about 30-40 minutes in 24 hours. Even though that may seem like an insignificant number, a horse that isn’t getting enough REM sleep will be tired and sleepy during the day.
A Zebra is a hoofed mammal that belongs to the horse family that can be found in the savannahs of Africa. Zebra and Horse are closely related, and even able to interbreed, but their offspring are always sterile.
Zebras also sleep standing up, but it’s believed to be for a slightly different reason than the Horse. A typical plains zebra will take the opportunity to sleep whenever it can, but they’ll only sleep when in large groups so they can be alerted of danger. By standing up, they’re able to pack closer to one another as well as quickly escape from danger.
Cows need their sleep to stay healthy, just as other animals do. However, they actually sleep far less than most, including humans. Overall, they only need about 4 hours of sleep a day with the rest of the time dedicated to eating and relaxing. It’s a common misconception that cows don’t lie down to rest at all, although they may doze off for a few minutes at a time while standing up.
Cows will actually lie down for up to 14 hours per day, standing up every few hours, stretching, and then laying back down again. A cow that’s laying down can properly digest their food and it increases blood circulation to help with milk production.
Still, it’s common to see a cow sleeping on its feet when in the sunlight, especially after going for a dip in the water. This helps them to conserve energy and is also believed to be from contentment, just like a cat can doze in a sunbeam.
Mammals aren’t the only ones with this unique sleeping position. The Flamingo makes its home on caustic salt flats which allow them to remain safe from predators. These salt flats are extremely alkaline and can damage most every other animal. However, this also means there aren’t any other comfortable places to lay down.
The Flamingo eventually evolved to stand on only one leg at rest, and this was a strategic choice. This position allows them to conserve body heat and, better yet, only have one foot in the salty marsh. By sleeping standing up, they minimize contact with the clumpy salt while exerting less effort by using a passive locking mechanism in their knee.
Giraffes may be the strangest sleepers in the Serengeti. As babies, they lay down with their legs tucked beneath their bodies and they rest their heads on their own back. Adult Giraffes will occasionally sleep like this as well, but more often they sleep fully standing – albeit, in short bursts.
In a day, an adult Giraffe will get on by just 30 minutes of sleep total. Many prey animals have evolved to require less sleep, and especially a large animal like the Giraffe. An animal that big laying down in the middle of the plains is simply too tempting a feast for nearby predators, so they make to on as little as possible. They’ll often experience a half-sleeping period while fully standing in which the eyes remain half-open and the animal remains fully upright.
Research has already shown that larger mammals tend to sleep less than smaller mammals, so it stands to reason the African Elephant shouldn’t sleep much. On average though, the Elephant sleeps for two hours a day, nearly four times as much as the Giraffe. In captivity, Elephants will sleep between four to six hours a day due to not having to go out and find the food they need to keep their large bodies going.
Most of their sleep is while standing, but they’ll lay down to sleep every third or fourth day to achieve REM sleep. Sometimes they’ll then go entire nights without sleep, instead choosing to wait for the proper environmental cues to ensure good sleep. It’s thought that if we study this further, we can adjust human sleep environments to get ourselves a better night’s sleep.
Camels have a sleep cycle that’s a little more familiar to humans. They sleep approximately six hours per night and can withstand major temperature changes without being woken up. This is important as their native environment of the desert fluctuates from sweltering heat in the day and freezing cold in the nights.
Like most of the prey animals on this list, they evolved this ability to be able to run away from predators at a moment’s notice. They’re able to do this consecutively at night as the majority of their predators are hiding from the cold. Camels are notoriously stubborn, and have been known to simply lay down every time they feel like resting or having REM sleep and cannot be forced to get up before they want to.
8. Other birds
Many species of bird may sleep while standing up, including ducks, geese, and most species of songbird. When in a standing position, a bird may turn its head around, tuck its beak into its back feathers, and pull one leg up to its belly before falling asleep. Tucking these bare parts under the feathers will give the bird added protection against cold temperatures.
Small songbirds must keep off the ground to better protect themselves from ground predators, but it’s also necessary to stay hidden. Nocturnal birds of prey are always a threat, so they’ve adapted to find brush and foliage as cover while sleeping. When sleeping while perched upright, these birds have tendons in their legs that involuntarily cause the feet to clasp. They’ll keep the feet tightly gripping the perch until the bird awakens and straightens its legs.
There are many reasons for an animal to evolve the ability to sleep upright. The most common is to be able to escape from predators, such as the hoofed mammals. Others do it to minimize contact with caustic surfaces that keep them safe like the Flamingo, and still others to preserve warmth like many other birds. Either way, it’s amazing to see how these animals have adapted to less sleep, and gives plenty of ideas as to how humans can do the same.