Color vision in animals. Fromcolor blind seals to tetrachromatic vision in birds

The colors in which we see an object are not only dependent on the spectral composition of the reflected light but also represent an interpretation by our eyes and the trichromatic visual system. How do animals of other species see the world? The majority of mammals do not have three but only two types of cones and therefore have dichromatic color vision. Marine mammals and some nocturnally active mammals even have only one type of cone and are completely color blind. In contrast, birds as well as many fish and reptiles see in the world in more color hues and with four types of cones. Many vertebrates, insects and crustaceans can see not only the spectrum perceived by us but also ultraviolet radiation as light. In order to understand how animals of other species see the world, their visual systems must be understood and the animals must be tested in behavioral investigations.