One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
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
You forget 90% of your dreams.
256
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
Staying awake for 17 hours is the same for your body as drinking 2 glasses of wine.
193