Link to layman's article Link to research article While studying museum specimens, scientists have discovered that the duck billed platypus is bioflourescent, making it the 3rd known mammal to exhibit this trait. The other 2 are the flying squirrel and the water opossum. Pictures of the platypus under different wavelengths of light The male and female specimens biofluoresced in the same patterns and intensity, within this limited sample. For the curious, this is a water opossum Interestingly, all 3 known bioflourescent mammals are nocturnal/crepuscular (active overnight/at dusk & dawn.) This discovery has set scientists on a journey to see if other mammals exhibit this trait.