Discover the phenomenon known as asymmetrical sleep, where parts of an animal's brain are asleep while other areas remain active. -- Many animals need sleep. But all of the threats and demands animals face don’t just go away when it’s t...

Discover the phenomenon known as asymmetrical sleep, where parts of an animal's brain are asleep while other areas remain active. -- Many animals need sleep. But all of the threats and demands animals face don’t just go away when it’s t...