Horses sleep while standing up.
Horses can sleep while standing because their bodies are completely relaxed. In fact it is better off for them to stand up than lying down. Horses have delicate bones and their body weighs a lot; they can get injured if they lay down for too long.
5 more interesting animal facts:
Hummingbirds are the only birds that can fly backwards.
Polar bears have black skin and their fur is not white.
Only the female mosquito bites.
Giraffes can clean their ears with its tongue.
Crocodiles can’t stick their tongues out, as it is attached by a membrane to the bottom of its mouth.