Fluorescent Mammals Are Much More Common Than You'd Think

An anonymous reader quotes a report from The Conversation: Recently, several mammals have been reported to 'glow' under ultraviolet (UV) light, including our beloved platypus. But no one knew how common it was among mammals until now. Our research, published in Royal Society Open Science today, found this glow -- known as fluorescence -- is extremely common. Almost every mammal we studied showed some form of fluorescence. We started with the platypus to see if we could replicate the previously reported fluorescence. We photographed preserved and frozen platypus specimens under UV light and observed a fluorescent (although rather faint) glow. We repeated this process for other mammals and found clear evidence of fluorescence in the white fur, spines and even skin and nails of koalas, Tasmanian devils, short-beaked echidnas, southern hairy-nosed wombats, quendas (bandicoots), greater bilbies and even cats. Both fresh-frozen and chemically treated museum specimens were fluorescent. This meant it wasn't preservation chemicals such as borax or arsenic causing the fluorescence. So, we concluded this was a real biological phenomenon.

Using specimens from the Western Australian Museum's collection, we took the experiment to the next stage. We recorded every species of mammal that was fluorescent when we exposed the specimens to UV light. As a result, we found 125 fluorescent species of mammal, representing all known orders. Fluorescence is clearly common and widely distributed among mammals. In particular, we noticed that white and light-colored fur is fluorescent, with dark pigmentation preventing fluorescence. For example, a zebra's white stripes fluoresced while the dark stripes didn't. We then used our dataset to test if fluorescence might be more common in nocturnal species. To do this, we correlated the total area of fluorescence with ecological traits such as nocturnality, diet and locomotion. Nocturnal mammals were indeed more fluorescent, while aquatic species were less fluorescent than those that burrowed, lived in trees, or on land.

Based on our results, we think fluorescence is very common in mammals. In fact, it is likely the default status of hair unless it is heavily pigmented. This doesn't mean fluorescence has a biological function -- it may just be an artifact of the structural properties of unpigmented hair. However, we suggest florescence may be important for brightening pale-colored parts of animals that are used as visual signals. This could improve their visibility, especially in poor light -- just like the fluorescent optical brighteners that are added to white paper and clothing.

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