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
People who sleep late have more mental stamina and can outperform early risers.
33
Bats sleep 18-20 hours per day.
5
Blue light fends off drowsiness in the middle of the night, which could be useful to people who work at night.
240
The average person falls asleep in seven minutes.
115
Honeybees never sleep.
276