You may have heard that horses only sleep standing up and think when you see a horse down that there is something wrong with it, so how do horses sleep? Is it really true that they only sleep standing up?
Horses have a unique body system called the stay apparatus, which allows them to sleep standing up. The stay apparatus is a sort of hammock of multiple ligaments and tendons that allows the horse to lock his legs.
In the wild, a horse will choose a sheltered area to sleep. This offers some form of extra protection from predators. They will position themselves so that their haunches face into the oncoming wind or rain.
Sometimes very relaxed horses in adjoining paddocks will all lay down to sleep at the same time. This is slightly unusual, but a nice sign as well. These horses are clearly comfortable in their surroundings and safe to do this without a lookout.