Lizards, birds and fish often sport vivid colors, from neon pink to deep violet, but most mammals are fairly drab. So why don't mammals match the vibrant hues of other animals?A number of factors culminate in the browns, blacks and whites that make up most mammalian coats. The first has to do with color expression. Matthew Shawkey, an evolutionary biologist at Ghent University in Belgium, explained that animals generally express color in two main ways: through pigments and through structures. Pigments exist within the skin and coat of the animal itself and reflect and absorb light to create certain colors. Structural coloration, on the other hand, involves nanoscale shapes and patterns on top of skin, feathers or scales that can distort light to produce bright, iridescent colors. Animals can use one method, or sometimes both, to express color. According to Shawkey, however, mammals don't really use either. Of the many color-producing pigments — such as carotenoids, porphyrins and pterins — mammals have just one type: melanin. The presence of that one pigment generates all of the colors seen in mammals, Shawkey said, and its absence creates the white regions seen in animals like zebras and pandas.
