Animals don't wear pajamas and they don't have ticking clocks to tell them when it's time to go to sleep But animals do know when it's time to rest
When darkness falls it's time for hummingbirds to sleep They need lots of rest after a full day of darting forwards backwards and sideways During the day these tiny birds flap their wings so fast that the wings seem to disappear All night long they sit perfectly still in a deep sleep They won't move again until sunrise
At night elephants lie down on their sides and go to sleep They often snore But after only two or three hours their big bulging bodies are no longer comfortable on the ground So they wake up and rock themselves back and forth until they are on their feet again If they are still tired the elephants will have to finish their sleep standing up
