Melanin, which creates dark pigmentation in skin, is responsible for giraffe tongues' dark color. Although it is unknown exactly why giraffes have tongues that appear blue, purple and sometimes almost black, scientists believe that the animals' tongues have evolved this way for sun protection.
Giraffes have prehensile tongues that wrap around leaves and can grow to be up to 20 inches in length. When feeding, the animals' tongues are frequently out of their mouths and exposed to sunlight, so the dark coloration serves to prevent them from getting sunburned. The underside of giraffes' tongues is a light pink color because it does not get as much sun and therefore needs less protection.