What Animals Sleep Standing Up? - List Of Examples - AnimalWised

Each type of animal that can sleep standing up is able to do so due to various anatomical mechanisms. One of the main factors is the ability to remain upright while being asleep. Many animals, including humans, cannot sleep standing up because their muscles relax when their mind is at rest.

Horses are able to maintain a standing position while asleep due to their ability to lock their stifle joint. This is the joint which connects the femur, tibia and kneecap in certain quadruped animals. When this joint locks, it helps the horse to support its weight, even if the muscles are more relaxed. Our article on how horses sleep will help explain in more detail.

Many birds belonging to the order Passeriformes (encompassing more than half of the world's bird species), such as canaries, pigeons, quail and crows, have a flexor tendon. This is located in the posterior area of the leg which stretches and tenses when the animal bends it to perch somewhere, giving the necessary rigidity for the stabilization of the body. When this mechanism is activated, the bird is able to hold their position firmly without falling when asleep. A particular aspect of these species is that they have control over this mechanism, being able to control it at will.

Other birds, such as flamingos and storks, can also sleep standing up. Even more impressive is their ability to do so standing on only one leg. The anatomical mechanism which allows them to do so is due to their legs which are effectively locked in place when situated at the center of their body weight, aided by bony articulations in the joints. Some studies suggest this ability means it takes less energy to sleep on one leg than on two[1].

This ability may appear to help the flamingo to reduce caloric expenditure during low temperatures. In higher temperatures, they are seen to be sleeping using both legs. When sleeping standing up on one leg, it is difficult for them to take flight. This suggests it to do with protecting themselves against low temperatures, not as an alert mechanism, as was believed for a long time.

So far, we have only discussed terrestrial animals. If you want to know more about animal behavior, we explain how fish are able to sleep in this AnimalWised article.