Animals Sleep Differently

Sleep bends to fit a species' life. Dolphins sleep one brain half at a time, keeping an eye open so they can keep swimming and surfacing to breathe.

Giraffes get by on short bursts adding up to around half an hour a day, while some bats sleep most of the day away. Common swifts can stay airborne for months, grabbing sleep in tiny in-flight bursts. The rule of thumb: the safer your bed, the deeper you can sleep.