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
You burn more calories sleeping than you do watching television.
348
Cows can sleep standing up, but they can only dream lying down.
745
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
Termites work 24 hours per day and they do not sleep.
57
The human brain is more active during sleep than during the day.
28
"Dysania" is the state of finding it hard getting up out of bed in the morning.
33