A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
Cows can sleep standing up, but they can only dream lying down.
745
Dieters who sleep more take off more fat that those who sleep less.
159
Sea otters hold hands while sleeping so they don’t drift away from each other.
104
People who sleep late have more mental stamina and can outperform early risers.
33