It is a surprising and previously unexplained phenomenon: In some mammals such as flying squirrels, platypuses or pocket rats, the fur glows bluish, greenish or reddish in a dark environment in UV light. Researchers previously suspected that photoluminescence or biofluorescence is used for camouflage, attraction or communication with conspecifics. Now a working group led by Séverine Toussaint from the Humboldt University of Berlin has examined the skins of various mammalian preparations in museums and found: Apparently, the glow has no ecological function, but is simply a side effect.
As the researchers report in the journal "Integrative Zoology", the substance porphyrin causes the play of colors. Porphyrins are chemical dyes of organic origin. In the mammalian body, they serve as building blocks for various proteins. If too many of them accumulate, the body stores them in the hairiness. Otherwise, the fabric threatens to make the animals' skin sore.
Basically, porphyrin should be in the hair of many mammals. However, it quickly disintegrates under the influence of sunlight. This is likely to explain why researchers have so far documented the photoluminescence, especially in night and twilight-active animals. They are less exposed to the sunlight, the porphyrin remains in their fur longer.
The scientists around Toussaint therefore do not attribute a special function for camouflage or intraspecific communication to fur glowing. Also because the radiation only occurs under special circumstances, when a concentrated UV beam hits the fur in a dark room. In nature, this situation probably almost never occurs.
The phenomenon of photoluminescence has been known for a long time. For example, in invertebrates such as scorpions. They emit bluish light in the ultraviolet. Experts have so far explained the glow of scorpions as sun protection, a lure for reproductive partners or to ward off parasites.
