How do animals sleep standing up?
Horses have to lie down to enter deep sleep, but they can snooze standing up so they’re ready to run if a predator is detected. A series of tendons and ligaments in their legs work together to ‘lock’ the joints and keep the horse balanced with little effort. The system, called the stay apparatus, engages when the animal relaxes its muscles.
Flamingos are famous for resting while balanced on one leg. By studying dead flamingos, scientists found that a musculoskeletal mechanism works in a similar way to the horse’s stay apparatus and ‘snaps’ all the joints into place when one foot is placed directly under the body and the other leg is folded away.
Sleeping like this is easier than standing on two legs and, as demonstrated by the fact that a dead bird will still balance perfectly, staying upright takes no effort at all.
It’s easier for a flamingo to sleep on one leg than balance on two