Whale Cetaceans

• Sleep
Unlike most animals, whales are conscious breathers. All mammals sleep, but whales cannot afford to become unconscious for long because they may drown. It is thought that only one hemisphere of the whale's brain sleeps at a time, so they rest but are never completely asleep.
• Surfacing behavior
Many whales exhibit behaviors such as breaching and tail slapping that expose large parts of their bodies to the air.