Many animals can see things that we cannot. For example, cats can see at night when it is too dark for us. However, we do not know what animals actually perceive. There is an important difference between merely having light illuminate our retina, and actually understanding what we are seeing.
The role of color vision in an animal's perception, behavior, and ecological setting, and its underlying retina and neuronal mechanisms vary enormously in different groups of animals. Although color as a perceptual category with cognitive significance obviously plays a great role in human life, there is, with the exception of hymenopterous insects, still little evidence about the roles of color perception in nonhuman animals, especially non-primates. Current research finds that color vision in non-primate mammals is very limited, and probably bears little resemblance to humans. Many animals also have an additional structure called the tapetum—a reflective layer that lies under the retina and acts as a mirror, bouncing light back toward the retina a second time.
A common question among nature lovers is whether animals have color vision like humans. As a general rule of thumb, one only needs to look at a taxonomic group's coloration for a probable answer. Since most mammals are primarily brown or black or gray, it's likely they have not evolved color vision and depend instead on acute powers of smell and hearing. Likewise, most bird species are brightly colored and probably see colors as least as well as we do (although they also seem to have hearing that is superior to ours).
To take this logic further, frogs and toads are probably "color-blind," but many insects such as butterflies and beetles have noticeable colors and patterns that seem to indicate their color vision is well-developed (Menzel and Backhaus, 1991). There's the possibility, of course, that animals............
