Sometimes horses sleep standing up. Standing-up horses were better able to avoid predators at night. Most horses sleep three hours a day standing up.
Zebras don't sleep like horses. Plains zebras sleep whenever they can, but only in groups to avoid harm. They can pack tighter and avoid danger quickly by standing.
Cows lie down for 14 hours a day, stretching every few hours. Laying down helps a cow digest and produce milk. After a swim, cows often sunbathe on their feet.
Not only mammals sleep this way. Flamingos live on caustic salt flats to avoid predators. These alkaline salt flats harm most animals. There are no pleasant locations to lay down.
Giraffes sleep oddly in the Serengeti. Babies lie on their backs with legs tucked under. Adult Giraffes sleep this manner occasionally, but they normally stand up.
The Elephant sleeps twice as long as the Giraffe. Elephants sleep four to six hours a day in captivity since they don't have to go get food.
Camels sleep like humans. They sleep six hours a night and can survive temperature changes. This is significant because their native desert has hot days and frigid nights.
Most songbirds and ducks sleep upright. Before sleeping, a bird may bend its head, tuck its beak, and pull one leg to its belly. The bird's exposed parts are protected by feathers.