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Ultraviolet Mammals: Black-Lit Beasties Come Out of the Shadows

Black lights aren’t just for stoners any more. Scientists have revealed some startling surprises, prompting a bit of a craze among zoologists. It turns out that shining an ultraviolet light into the dark night has brought to light spectacular specimens in the forests of North America and Australia.

Tasmanian devils emit blue light.

Over the last few weeks platypuses and then wombats were discovered to remit absorbed light, a trait known as biofluorescence. And now Tasmanian devils have been added to the list. This might lead you to think that this is a new thing among mammals or that only mammals from Australia glow. The truth is far more inclusive.

A wide range of creatures fluoresce under black light for a variety of reasons. The most common biofluorescent animals are fish, reptiles, amphibians, and birds. However, the trait was first revealed in mammals in 1983 in the Virginia opossum. In 2019, biofluorescence was documented in all flying squirrel species throughout North and Central America.

Flying squirrels glow pink.

The most recent addition to the list, Tasmanian devils, radiate blue light while flying squirrels glow pink. The fur of other species biofluoresces in red, orange, yellow, purple, or lavender.

But why do they glow? What do these biofluorescent animals have in common? They are all nocturnal, creatures most active at night. This could mean that they use biofluorescence to detect night-time light levels as in the case of scorpions that exhibit the trait. Animals might also use it to camouflage themselves from UV-sensitive predators, although just how they do this is no yet understood. Unlike male birds that biofluorescence to attract mates, the same way they use daylight displays of color, platypuses, at least, emit a uniform glow in both males and females, ineffective for sexual signaling.

Platypus glow green to cyan. The evidence of this trait in monotremes, the oldest mammalian species, suggests that biofluorescence maybe be an ancient animal adaptation.

What luminous critters are on the horizon? Potentially a horde! Scientists need only throw open the collection drawers of all the museums of the world and shine a black light on age-old specimens to flush out more vibrant varmints. Then the next step is confirmation in the wild. New discoveries of this type could soon be legion.

Let’s hope cryptozoologists take note. Perhaps some application of black light could join night vision as a tool in the hunt for other mysterious nocturnal creatures like the thylacine and Bigfoot. These discoveries could also be relevant to the search for extraterrestrial life. In 2018, two U.K. scientists argued that large, biofluorescent animals, such as corals, could mark the light reflected from planets during UV flares with a distinct biosignature.

These bright, new discoveries drop yet another veil on our perception, uncovering an array of glimmering reminders that we haven’t seen everything yet. Humanity still has so much to learn about what’s out there. Maybe someday we’ll be invited to the bestial rave.