Do you know all the living things need to sleep? People can sleep in their (house) to keep safe. But to some animals, it's not safe for them
(sleep) sometimes. When they sleep, other animals may hurt or kill them. Animals have to think of many ways to protect (they) so that they can sleep well.
Seals(海豹) need to (breath) air, but that doesn't stop some of them sleeping underwater. They hold their breath and dive deep to sleep. It can help these seals get away from some (danger) animals.
Some ducks sleep with just half of their brains. They often sleep in a line. The ducks at both ends help to keep group safe. They keep one eye open to watch for danger. The ducks sleep deeply the middle with both eyes closed.
Some seabirds sleep while they are flying. These big birds spend most of their lives (fly) over the sea. They are in danger if they are on the water, they'll be safe in the sky. They can fly for many hours without flapping their wings.
Horses often sleep while standing up. Their legs lock (固定)in the place so they don't fall over. A horse can run from danger (quick) if it is already standing. If a horse is lying down, it needs a long time to get up.
