Human eyes respond to light only in the
visible region of the electromagnetic spectrum, however, many animals have eyes that
respond in different ways. Some animals see no colour. Others are able to detect infra-red or
ultraviolet light.
• The red squirrel and the guinea pig have only one type of
retinal cell (no cones) and are totally colour-blind.
• Bullfighters often use red
capes to infuriate the bull. The bull is probably responding to the movement of the cape not
its colour, since there are no cones in the eyes of cattle.
• Cats have very poor
colour vision, but under good conditions can distinguish blue-green colors from orange-red
ones.
• Many birds and fish have excellent colour vision. The Australian
bowerbird decorates its nest with various blue objects such as scraps of paper, juice from
blueberries, and feathers from smaller birds.
• Three types of cone cells have
been found in hens and pigeons, who have color vision similar to humans. Owls, however,
have no cones and are colour blind.
• Many fish are able to distinguish colours.
Sticklebacks and Siamese fighting fish react vigorously to red and blue in both courtship and
defence of territory.
• Bees are colour-blind to red and orange but are able to see
blues into the ultraviolet range, and many flowers are able to reflect that end of the
spectrum.
• Ants are unable to see red light. We are able to film their nocturnal
activities using red light, which they perceive it as normal darkness.
•
Mosquitoes and other unpleasant flying insects don't see yellow so they are not
attracted to yellow insect-lights. However they do see purple so bug-zappers emit blue to
ultraviolet lights, attracting the insects to a high voltage source which kills them.