The distinctive pink coloration of the boto, or Amazon river dolphin, makes it easy to distinguish from other odontocetes. Born with dark gray pigmentation, the dolphins become more translucent with age so that blood circulating beneath their skin gives them a vivid pink appearance, especially on the ventral side. Botos living in clear waters tend to have darker pigmentation than those living in turbid waters. In addition to their unique coloration, botos can be identified by their long beak containing many stiff hairs. Although all dolphins originally have hair, a characteristic of mammals, most lose it soon after birth.
Scientists believe that the botos hairs are used as tactile sensory organs.
These may help make up for reduced eyesight. The mouth of Amazon river dolphins is fairly straight with a slight upturn at the corners. They have heterodont dentition, with conical front teeth and molar-like rear teeth. They eat a wide variety of benthic organisms, including catfish. Heavily armored fish and crustaceans can be crushed with the rear teeth.