A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Bats sleep 18-20 hours per day.
5
Termites work 24 hours per day and they do not sleep.
57
Cows can sleep standing up, but they can only dream lying down.
745
The harder you concentrate on falling asleep, the less likely you are to fall asleep.
34
Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
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
People who sleep late have more mental stamina and can outperform early risers.
33