Do Horses Sleep Standing Up or Lying Down?

We have already found out that horses can sleep both standing up and lying down. The reason for this is because they have different states of sleep that provide different benefits. It is also related to the fact they are a prey animal. Prey animals are most vulnerable when sleeping, so being able to enter different types of sleep can provide an advantage in terms of survival in the wild.

How do horses sleep standing up?

Horses use an anatomical mechanism which is known as the stay apparatus. This is a passive stance which is afforded by the arrangement of muscles, ligaments and tendons working together to keep a horse in a standing position. By these body parts locking together, the horse can enter a light sleep while standing without the risk of falling over.

When sleeping standing up, horses only enter a phase of light sleep or dozing. While they are resting and conserving energy, they are not completely shut off from their surroundings. They may have their eyes closed, but their ears and other sensory organs are able to detect various stimuli. This allows them to make a quick evasion if they detect a predator approaching or if another horse gives them a warning.

How do horses sleep lying down?

Although horses can rest standing up for much of the day, they need to lie down to achieve deep sleep. This is a phase known as REM (rapid eye movement). It is a more restorative sleep stage and requires their muscles to relax completely, something which cannot happen even with the stay apparatus system. They usually look for a comfortable and safe space to lay down, such as on the hay floor of their stable.

When sleeping lying down, horses tend to group together. Some horses can stay more alert and keep watch while others enter the more vulnerable stage of REM sleep. Horses do not sleep for long periods of time. They alternate periods of short rest with activity, doing so night and day. For this reason, they are not considered diurnal or nocturnal, although they will generally maintain a certain behavioral pattern.

How do horses sleep in captivity?

Horses will have differences in sleep quality and duration depending on whether they live in the wild or captivity:

• Duration: wild horses tend to sleep around 2 hours a day, but they will do so in bursts of around 15 minutes. This may be longer when entering REM sleep. Captive horses do not have the same threats, so they may sleep for longer bursts, but also longer overall.
• Position: due to being more vulnerable in the wild, horses will often reduce the amount of time spent lying down. Horses in captivity may spend more time sleeping lying down because they feel more secure.
• Location: wild horses have more options of where to sleep. A captive horse with unsuitable flooring or limited space may find it difficult to lay down.
• Group dynamics: wild horses will often take turns entering REM sleep, with other members of the herd standing guard. In captivity, horses may be separated. This can complicate their sleep pattern, potentially making them have less deep sleep if they feel too vulnerable.

While the amount may differ, all horses will need some amount of deep sleep. They may not enter REM sleep every day, but they will need to do so every couple of days to meet their sleep requirements. If they are unable to do this, they run the risk of collapsing due to extreme tiredness.

Discover more about how another large herbivorous mammal rests with our article asking how do elephants sleep?

As we have seen, the type of sleep will determine whether a horse sleeps lying down or standing up. Generally speaking, horses are polyphasic animals. This means they sleep in different phases throughout the day, rather than in one continuous block like we humans do. This pattern includes specific phases that serve different functions:

• Light drowsiness: this can last from a few minutes to about half an hour. Horses rest standing upright in this phase of sleep with their legs locked thanks to the passive stay apparatus. During this phase, the brain slows down, but the senses remain active. The eyes may be open, half-open or closed. The ears will move in the direction of nearby sounds. This phase is more a state of relaxation than deep sleep.
• Non-REM deep sleep: this usually lasts between 30 and 60 minutes a day, divided into several bursts. A horse may sleep standing up or lying down during this phase. The horse enters a deeper state of rest, which allows for physical recovery. Although they are not completely disconnected from the environment, brain and muscle activity decreases significantly.
• REM (rapid eye movement) sleep: this only takes up about 20-40 minutes a day. This is the most restorative phase. The brain is highly active while the body remains completely relaxed. It can only occur when the horse is lying down, as the muscles need to be free of tension. During this phase, horses may move slightly, flapping their ears or moving legs. They will show eye movements under closed eyelids. REM sleep is crucial for a horse’s memory, mental recovery and general well-being. Without this phase, they may experience stress and health problems.

We can learn more about how horse behavior affects their survival with our article asking how do horses mate?

Compared to other mammals, horses require relatively little total sleep time. Their average daily rest period varies between 3 and 5 hours, divided into multiple short periods distributed throughout the day and night.

Factors that influence the sleep time of horses are the following:

• Age: foals and young horses sleep more than adults, resting up to 12 hours a day. As they age, the amount of sleep decreases. Learn more about the life cycle of a horse in our article asking how long do horses live?
• Environment: horses in a safe and comfortable environment (such as a quiet stable) tend to sleep longer lying down and experience longer REM sleep phases. In environments where they perceive greater danger, they tend to sleep standing up more than lying and do so for shorter periods.
• Health status: horses with pain, stress or illness tend to rest less, something which can affect their overall well-being.
• Sleep distribution: horses do not sleep continuously. Their rest is alternated with periods of activity, allowing them to maintain a balance between rest and alertness. Although not technically diurnal, most of their deep sleep occurs at night, although they may take brief naps during the day.

Now we know that a horse sleeps both standing up and lying down, we may want to know about the sleep patterns, positions and more in other animals. Do so with our articles asking how do otters sleep and do giraffes sleep standing up?

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