Flying Squirrels Glow Fluorescent Pink Under Ultraviolet Light

A chance encounter in the forests of Bayfield County, Wisconsin, has led scientists to a startling realization: As Jon Martin, a forestry professor at the state’s Northland College, discovered after pointing his ultraviolet flashlight toward a flying squirrel feasting at a bird feeder, the gliding creature’s fur glows a fluorescent bright pink under the right conditions.

To determine whether this phenomenon was merely a one-time anomaly, Martin recruited the help of several Northland colleagues. Next, Jake Buehler writes for National Geographic, the researchers traveled to the Science Museum of Minnesota and Chicago’s Field Museum, where they analyzed 135 squirrel skins—including those of both flying and non-flying specimens—under visible and ultraviolet light.

Time and again, the scientists report in the Journal of Mammalogy, the team found that members of the Glaucomys genus, also known as New World flying squirrels, emitted that same telltale pink glow.

“The fluorescence was there in the Glaucomys from the 19th to 21st century, from Guatemala to Canada, in males and females, and in specimens collected in all seasons,” senior study author Paula Spaeth Anich, a biologist at Northland, tells National Geographic. In fact, all but one of the Glaucomys specimens studied revealed a fluorescent shimmer.

Significantly, Newsweek’s Katherine Hignett notes, New World flying squirrels were the only specimens that appeared to boast this unusual coloring. Although the researchers tested additional species, such as the eastern gray squirrel, the fox squirrel and the American red squirrel, none yielded the results seen amongst members of the three Glaucomys species.

Technically speaking, fluorescence refers to the luminous glow released by a substance absorbing light or another form of electromagnetic radiation. As the team notes in the study, ultraviolet fluorescence has previously been recorded in plants, marine and terrestrial invertebrates, arachnids, and birds.

In mammals, however, the phenomenon has proven far more elusive. Prior to these new findings, fluorescence had only been observed amongst members of the Didelphidae marsupial family, which consists of about two dozen species of American opossums.

Flying squirrels and opossums don’t appear to have much in common, Buehler explains for National Geographic. They’re not closely related, they live in different ecosystems and they follow distinct diets. Still, the two do share one major characteristic: Both are nocturnal, whereas flying squirrels’ non-flying counterparts are more active during the day.

There are an array of potential explanations for flying squirrels’ fluorescence, study co-author Allie Kohler, a graduate student at Texas A&M University who spent her undergraduate years at Northland, tells Newsweek’s Hignett. It’s possible the glow helps squirrels recognize each other in low-light situations, or perhaps ward off predators.

Then again, Kohler says, “This trait could just be a cool color they happen to produce.”

Speaking with National Geographic’s Buehler, Anich details several additional areas of interest, including night-time perception and communication, navigation in snowy environments, and camouflage or mimicry.

Further testing, particularly of other flying squirrel species spread out across the globe, will better elucidate the team’s initial findings, but as Anich points out, the most enticing question the research raises is whether other animals, completely unbeknownst to humans, also possess snazzy fluorescent shimmers.

Anich concludes, “The lesson is that, from our diurnal primate standpoint, we are overlooking many aspects of animal communication and perception that happen at twilight and night-time.”

Meilan Solly | | READ MORE

Meilan Solly is Smithsonian magazine's associate digital editor, history.