Why Do Flying Squirrels Glow Hot Pink in UV Light?

As it turns out, most flying squirrels glow hot pink in ultraviolet light. Learn what researchers think may be the reason in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:02):
Welcome to brain Stuff from How Stuff Works, Hey, brain Stuff,
Lauren Vogel bomb here. It's amazing what you can find
if you shine a flashlight into your backyard trees. A
biologists in Wisconsin have made a rather startling discovery that way,
in part startling because it apparently hadn't been recorded until now.
Three different species of flying squirrels, specifically Southern, Northern, and

(00:26):
Humboldts flying squirrel which are found across North America and
into Central America, sport light brown fur that, when spotlighted
with ultra violet illumination, lights up a hot bubblegum pink.
The phenomenon occurs on both the top and bottom surfaces
of the flying squirrels, though it's the underside of a
flying squirrel's carriage, including the flaps of skin that's spread

(00:48):
out when the squirrel glides from tree to tree that
really glows. Jonathan Martin, a biologist at Northland College in Ashland, Wisconsin,
made the discovery in the forest one evening just by
shining a UVY flashlight into the tree canopy. He was
looking for lichens, which are certain types of frogs and
flora that light up in UVY light. That's when he

(01:08):
heard the chirp of a southern flying squirrel. As the
squirrel glided by, he shined the UVY flashlight on it,
and he saw a flash of fuchia. Martin and his
colleagues soon found themselves examining the skins of flying squirrels
at the Science Museum of Minnesota and the Field Museum
in Chicago. They took photos of the skins under visible
light and ultra violet light. All but one specimen of

(01:31):
the gliders glowed a pink that has been variously compared
to bubblegum, day glow, and licro from the nineteen eighties.
The results of the study were published in the January
twenty nineteen issue of the Journal of Mammalogy. The pink
is caused, the researchers say, by the furs fluorescence, which
is what happens when light is absorbed in one wavelength

(01:51):
and emitted in another. You may remember an episode we
did about how scorpions fluoresce bright green and ultraviolet light.
Some birds also have this trait, some fish too. Few
mammals do, though. Flying squirrels are nocturnal and are most
active at dusk and dawn. No other squirrels in North
America are known to possess this ability to fluoresce, including

(02:13):
tree squirrels like the Eastern gray, though there are over
two hundred and fifty squirrel species around the world, and
to be fair, the researchers have not yet tested other
species for the next question is what purpose could this
fluorescence serve. Humans can't see ultraviolet wavelengths except under special lighting,
but other animals can. One theory suggests the pink is

(02:36):
used to confuse owls, which, as it turns out, also
have undersides that fluoresce. A similar pink. Owls prey on
flying squirrels, among other mammals. Perhaps the squirrels evolved to
mimic owls so as not to be eaten by them.
Another theory, which is already being challenged, is that the
pink attracts potential mates. Flying squirrels have mating seasons, but

(02:57):
their flamboyant fluorescence is available for view it in year round. Anyway,
it's not even clear that squirrels can see in UV wavelengths. Ultimately,
the researchers point out that age old impetus of science.
This is proof of how much we don't know and
still need to learn. The study concluded the ecological significance
of this trait warrants further investigation. Today's episode was written

(03:25):
by Jamie Allen and produced by Tyler Clang for iHeartMedia
and How Stuff Works. For more on this and lots
of other topics, visit our home planet, how stuff works
dot com