Horses are known for their ability to sleep standing up, but, like all equids, they can also rest sitting or lying on their side, especially on fresh, clean straw, which they love to roll around in.

There are two main reasons, one anatomical and the other neurological, that explain why equids can sleep standing up.

From an anatomical point of view, horses, having four legs, maintain their balance with less effort than bipedal beings. Furthermore, thanks to special ligaments that stabilise the joints in a fixed position, they are able to lock their legs, further reducing the muscular effort required to stand. This position is therefore comfortable and easily sustainable.

However, when they lie down, they cannot maintain that position for too long, as their body mass and the compression of their viscera on the diaphragm make breathing difficult.

From a neurological point of view, horses have a special ability to maintain control of their limbs even while sleeping. This is an evolutionary advantage that, in the wild, allows them to remain ready to flee from potential dangers at all times.

Furthermore, horses never enter deep sleep. Even when resting, they maintain a certain muscle tone and only reach the REM sleep phase, which is light sleep.