Sea otters hold hands while sleeping so they don’t drift away from each other.
104
The human brain is more active during sleep than during the day.
28
In China, teachers allow children to sleep in class for around 20 minutes to help improve their learning.
13
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
One reason that kittens sleep so much is because a growth hormone is released only during sleep.
212
The record for the longest scientifically documented period without sleep is 264.4 hours (eleven days).
15
Lack of water is the #1 trigger of daytime fatigue.
148
Honeybees never sleep.
276