Name: Tom F Ihde
How do sharks pass the time if they never sleep?
First off, we don't know whether sharks sleep or not.
Many shark species (there are over 350 different kinds!)
need to constantly swim in order to breathe (or respire)
but this does not necessarily mean that they don't "sleep".
Many animals can shut down part of their brains for a short
time, while keeping other parts "awake" or alert, and watching
for predators; other animals merely slow their brain function
for a certain amount of time each day; sharks may do these things
as well, even though they keep swimming. Its also possible that
they don't sleep at all. The only way for us to find out for
sure is to catch them and measure their brain activity all the
It's also important for us to realize that their brains are
made and organized very differently from our own, and though
sleep is very important for humans, it may not be for other
animals like the shark.
Most shark species spend most of their time just swimming or sitting
on the bottom (those that don't need to constantly swim) waiting for
a meal to swim past.
Finding answers to questions about what animals do, is what an
"ethologist" does. "Ethology" is the study of animal behavior.
Sharks that swim all the time would be almost impossible to study
if you didn't have aquariums and zoos to study them in.
Tom F Ihde
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Update: June 2012