Cows can sleep standing up, but they can only dream lying down.
745
Honeybees never sleep.
276
The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
15
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
Some people have a "natural alarm clock" allowing them to wake up when they want. This is actually caused by a burst of the stress hormone adrenocorticotropin.
15
Sleeping on your stomach can induce weirder, scarier, and sexier dreams.
22