Are cows and horses the only animals that sleep standing up?

Cows and horses are not the only animals that sleep standing up. Other animals that can sleep standing up include elephants, giraffes, camels, and some species of deer and antelope. These animals have special adaptations that allow them to rest in this position without falling over. For example, cows and horses have a strong sense of balance and a locking mechanism in their legs that keeps them from collapsing. Giraffes have long legs and a flexible neck that allow them to reach the ground while their head is held up high.