A hippo sleeping underwater automatically rises to the surface every ~4 minutes and breathes without waking.
23
The average cat sleeps about 2/3 of the day.
203
One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
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
Honeybees never sleep.
276