Which animals have night vision?
Octopuses, owls, crocodiles and cats all have something in common: special adaptations to see at night.
Read about
nocturnal animals.
Transcript
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NARRATOR: While most
humans are sound asleep,
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many animals have
their eyes wide open.
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And why such late nights?
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Because some of these
animals can see in the dark
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far better than we can.
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So which animals can navigate
by night, and how do they do it?
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For animals like the
tarsier and slow loris,
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it's their large eyes.
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Larger eyes with
larger pupils allow
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more light to be taken in.
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The more light
taken in by an eye,
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the better an animal can see.
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And while the tarsier's
eyes provide greater vision,
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they also have some
minor drawbacks.
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Since their eyes are
fixed in their sockets,
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they must rotate their
heads to look from side
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to side, up to 180 degrees.
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And yet, the tarsier's
head-turning vision is only one
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of a number of animals
with such gifted sight.
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The owl, also with fixed eyes
and excellent night vision,
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can twist its neck
up to 270 degrees
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so it can see in
nearly every direction.
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With 10 times the night
vision capabilities as humans,
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they're experts at
maneuvering through trees
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in search of a midnight meal.
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But birds are far
from the only animals
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to have evolved eyes
for seeing in the dark.
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Many cephalopods,
such as the octopus,
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have proportionally large
eyes that help them search
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for food when light is lacking.
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In fact, it's not only the size,
bought also the shape which
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makes a difference in the dark.
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Though technically colorblind,
the w-shaped pupils
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of the cuttlefish allow
light into the eye
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from many directions,
spreading out the wavelengths
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and possibly allowing
them to determine color.
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Different species even
evolved similar pupils.
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For example, hunters such
as crocodiles and cats
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both have slit pupils that are
vertical instead of horizontal.
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Vertically elongated
pupils are much more common
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in ambush predators
and provide better
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depth perception of prey.
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These animals also share
a thin reflective layer
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behind the retina called
a tapetum lucidum.
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It's this layer that causes eyes
to appear to glow in the dark.
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Found in many species, this
layer acts like a mirror.
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It reflects light
back into the eye
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providing more light
to see and therefore,
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better eyesight in dim light.
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Vision is a complicated process
and one humans are still
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researching, not only to
discover just how differently
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other animals see the world
but to inspire high-tech camera
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design, medical
imaging, and perhaps,
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one day, even synthetic
retinal implants.
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At least for now, while animals
like the owl and tarsier
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are alert at night, we can
rest our eyes so they work
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best when the sun comes up.
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