The short answer is no...they see many
The way that the eye works in higher mammals
and most higher vertebrates ensures that most
animals see and interpret some sort of color.
In animal eyes, there are two types of cells,
rods and cones. The rods are very
sensitive to light, but cannot detect color
(basically they work as black and white, also
known as "greyscale"). The cones detect
particular ranges of color. We have
three types of cone cells, which birds have
five. This makes birds very sensitive to minor
changes in color compared with humans.
Each nerve cell that sends signals from the
rods and cones to the brain will be associated
with 100-200 rod cells but only 1-5 cone cells.
The effect of this is that animals have very
sensitive greyscale vision that is low definition,
or blurry. They tend to have very insensitive
color vision, but the details in color are very
sharp (high definition).
Evolution determines the balance of rods and
cones in an animal's eye.
Animals that have adapted to living in the dark
(nocturnal animals such as owls) tend to have far
fewer cones, so that they only see in black and
white. Animals which are active in the daytime
(humans or hawks) have many cone cells and can see
well in color.
You may notice that when you try to
see in the dark you cannot focus well on things,
but you "feel" like you can see things around you.
In humans, the majority of rods (greyscale) are
positioned around the outside of the eye, giving
you good black/white peripheral vision. The
majority of cones (color) are positioned at the
center of the eye in an area called the
fovea, so when you focus on things you see
At night, your cones don't work very
well, so you rely very heavily on your
peripheral vision to navigate. The mental
switch from cones to rods when the lights are
suddenly turned off is what forces you to take
time to "adjust" to the dark.
In general, animals that are diurnal (active
in the daytime) tend to have color vision, while
animals that are nocturnal (active at night) tend
to be "colorblind." There are millions of
species of animals, though, so there are many
exceptions to this rule.
It can be hard to measure color
vision, because it's sometimes hard to know what
an animal is seeing. Scientists used to think that
finding out was as simple as looking for "cone
cells" in the animal's eyes. These are the
cells that can sense different colors in light.
It's not that simple, though, because cats have
very few cone cells, and they're normally
nocturnal, but it seems that they can see the
color blue better than scientists expected.
Some animals can see colors that we can't
see. Bees, for example, can
see in ultraviolet. Rattlesnakes can sense
infrared radiation, but I'll leave it up to you
whether or not to call that vision!
This is a really hard question to answer
simply. Animals, from insects to fish to
mammals, have a wide variety of vision types, and
I can't make a good generalization about color
Plus, nobody has gone out and tested every
animal to find out how they see, so we just don't
know about a lot of animals. However, I can tell
you a few things about color vision that will help
you figure out which animals can see multiple
colors and which can't.
In vertebrates, there are two different
types of photoreceptors in the eye: rods and
cones. Rods are very good at seeing motion
and seeing in low light, and cones are very good
at resolving fine detail and seeing in color. A
single cone can only see one color, so to
be able to see all the colors that we see, an
animal needs to have 3 different kinds of cones
(red, green, and blue -- just like the 3 colors
that TV sets use).
Birds have 4 kinds of cones, so they can
see fantastic ranges of color that are hard for us
to imagine. So ideally an animal would have
lots of rods and lots of different kinds of cones
and it could see everything very well. But it
takes a lot of energy to make and maintain all
those receptors and pigments, so an animal is
limited in the number of receptors it can have.
Also, there is a limited amount of space in the
retina for these receptors to fit.
So an animal can have a lot of cones and see
well in low light conditions, or it can have a lot
of cones and see colors very well during the day,
but it can't do both.
So nocturnal animals, like most mammals,
including mice, cats, and dogs (I realize that
your pet cat and dog aren't really nocturnal, but
that's only because they've gotten used to hanging
out during the day because that's when we feed
them and give them attention -- wild cats and dogs
are much more active at dusk and in the night than
during the day) have lots of rods and see really
well when there's not much light, but they don't
have many cones. So they can't see color very
well and also don't have very sharp vision.
Dogs can see some colors, but they only have 2
kinds of cones, not 3, so they can't see as many
colors as us -- it's sort of like they're
colorblind. Humans and most other primates are
more diurnal (we're active during the day) and
often need to be able to see different colors to
survive. For example, fruit-eating monkeys
have to use color to tell which fruits are ripe or
nonpoisonous. So we have a lot of cones and
few rods, and we don't see well at night. Birds
are also usually active during the day and also
need to be able to use color to identify foods, so
they also have lots of cones and good color
However, you can probably think of at least
one well-known nocturnal bird that might have more
rods than cones. Thinking about birds might also
lead you to think of another way we can tell if
animals can see colors. If you think about most
of the birds you know, you'll notice that many of
them have very colorful plumage. Often this
colorful plumage seems to be used in mating --
females choose a male with the brightest colors.
If it seems like animals are making decisions
based on colors, then we know that those
animals must be able to see colors. If an animal
only needs to see one color (it just needs to know
if something is red or not, for example), then it
might just be able to see that one color. So we
can now identify a lot of other animals that must
be able to see multiple colors: colorful
songbirds (they use colors to tell each other
apart, to judge the quality of mates, and to find
food), fish on coral reefs and in tropical
streams (they use colors in ways similar to
birds), and insects that pollinate flowers (they
use colors to find the right flowers). Insects
don't have eyes like we do, so they don't have
rods and cones. Some of them can see colors, but
not as many colors as we can. On the other hand,
some honeybees can see 'colors' that we can't
see, because they can actually see ultraviolet
light. So some flowers that look white to us
are quite colorful to honeybees.
I'm sorry this wasn't a simpler answer, but I
hope it helped you understand how color vision
works and why some animals do it better than
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