6 Surprising Animal Sleep Habits

Great Frigatebirds

Electroencephalographs (EEGs) implanted into the birds’ brains found that they sleep for only around 45 minutes total while mid-air, usually after dark. The birds also often sleep with only one side of their brain at a time while in flight (unihemispheric sleep). They do it not to evade predators, since they don’t have any in the skies, but perhaps to avoid mid-air collisions. The birds do, however, sleep longer when they’re on land, where they may also sleep with both sides of their brains at once.

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