Can chameleons see in color, since they can blend in with their surroundings?
-- Brittany Suarez, 10, Rockville
Chameleons can see color and, in fact, they can see better than you.
Most animals see fewer colors than humans can. But some -- including chameleons -- can see the same colors we do plus ultraviolet light, which we cannot see.
To understand this better, let's talk about the basic ability to see in color. Most humans can see versions of three basic colors: blue, green and red.
Most other mammals (dogs, cats, cows and horses, for example) see just two colors, either blue and red or red and green. (And these two colors, they can only just barely make out.) Some people -- we call them color-blind -- are born with only two-color vision.
There also are creatures that see just one kind of light. An octupus, for instance, sees only blue.
Scientists have figured this out partly by doing tests to see what colors the animals respond to, and partly by studying the tiny structures in eyes. Human have three special proteins, called opsins, in their eyes that can detect red, blue and green light. Animals with only two opsins see only two colors.
Animals with more than three opsins (such as shrimp, most birds and many insects and reptiles) can see ultraviolet, or UV, light.
So, what's that like for them?
"They can see a broader range of colors than we can. They can distinguish colors better -- there's often greater contrast," said Richard Payne, a professor of neuroscience at the University of Maryland.
Seeing ultraviolet light helps creatures with a big interest in flowers, such as nectar-seeking bees or hummingbirds or bug-eating birds or reptiles. Flowers reflect a lot of ultraviolet light. A flower that would appear to us a blah white, with yellow pollen in the center, might be glowing with multi-colored patches to a bird or chameleon. The pollen would really stand out -- so would a tasty beetle on a petal.
Another way ultraviolet vision may help an animal is by helping it see others of its kind. Some creatures (certain parakeets, for instance) have patches of feathers that reflect ultraviolet light. Perhaps, Payne speculated, super vision helps chameleons find their camouflaged friends.
UV vision isn't always great for critters, though. Think of those backyard bug zappers baited with ultraviolet light. The insect thinks it's heading toward an interesting flower and instead gets zapped with a lethal jolt of electricity.
-- Fern Shen
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