How good is a shark's vision?
Do they see as well as humans?
I'm Jonathan Bird and this is Shark Academy!
Since sharks have so many keen senses, like
smell and their electrosensory system, for
a long time it was assumed that sharks were
making up for having bad vision.
Well, turns out that's just not true.
The shark eye is remarkably similar to the
human eye.
It has the same basic structure, with a cornea,
lens, pupil and an iris.
It also has rods and cones in the retina,
which means the shark can see in color.
But we have no idea what kind of color it
can see in a blue environment.
It can also open and close the pupil, in response
to available light, just like humans.
And most fish can't do this.
The shark has a reflective layer behind the
retina called the tapetum lucidum.
Its purpose is to reflect light back through
the retina a second time.
It's very similar to the eye of a cat.
If you look into a shark's eye at night with
a light, it will actually reflect back at
you, just like a cat's eye.
This increases the low-light sensitivity of
a shark's eye.
They can see amazingly well in light that,
to us, would just look…dark.
Some estimates say that the shark's eye is
ten times more sensitive in low light than
human eyes.
And get this!
Sharks also have eyelids!
They're the only fish with eyelids.
They're called nictitating membranes, and
they close them when they are attacking prey
at close range to protect their eyes.
Sometimes when the sharks come really close
to our video cameras to investigate what they
are, we'll see the nictitating membranes close.
This is one of the reasons that people think
that sometimes sharks bite people by accident—because
when they get really close to the prey, they
actually close their eyes, and they can't
see what they're doing!
Well, I hope that all makes sense and now
you can see why sharks are out of sight!
I'm Jonathan Bird.
Until next time, this is Shark Academy!
And, don't forget to check out our other shark-related
videos on our channel!
