Bats That Glow in the Dark? Scientists Are Still Searching for Answers

As Halloween decorations begin to appear—complete with glowing bats dangling from porches and trees—it might sound like pure fantasy to imagine bats that actually glow. But nature, as it turns out, may be even stranger than seasonal décor. According to recent research from the University of Georgia, several bat species across North America emit a faint green glow when exposed to ultraviolet (UV) light.

The discovery has both fascinated and puzzled scientists. While the glowing effect is real and repeatable, no one yet knows why these nocturnal mammals possess such an unusual trait.

An Accidental Discovery in a Museum Setting

Interestingly, this revelation didn’t come from studying bats in the wild. Instead, it emerged during an unexpected experiment involving preserved specimens housed in museum collections.

Researchers examined 60 preserved bats representing six species commonly found in the United States:

• Big brown bats (Eptesicus fuscus)

• Eastern red bats (Lasiurus borealis)

• Seminole bats (Lasiurus seminolus)

• Southeastern myotis (Myotis austroriparius)

• Gray bats (Myotis grisescens)

• Brazilian free-tailed bats (Tadarida brasiliensis)

When these specimens were placed under ultraviolet light, every single one of them emitted a vivid, ghostly green glow. Even more striking was the consistency: the glow appeared in the same regions across all species—primarily on the wings, hind legs, and the thin membranes connecting their limbs. These areas are crucial for flight and movement, suggesting the glow is far from random.

What Is Photoluminescence?

The phenomenon behind this eerie glow is known as photoluminescence. It occurs when a substance absorbs high-energy light—such as UV radiation—and then releases that energy as visible light.

While photoluminescence is common in minerals, fungi, and some marine organisms, it is still considered rare in mammals. That’s what makes this discovery so remarkable: mammals were long thought to be largely absent from the list of naturally fluorescent animals.

Bats Aren’t the Only Glowing Mammals

Even more surprising is that bats aren’t alone. Over the past few years, scientists have discovered photoluminescence in several other mammals:

• Flying squirrels that glow bright pink

• Opossums with subtle fluorescence

• Wombats showing faint luminescent hues

• The platypus, which glows blue-green under UV light

These findings have forced scientists to rethink long-held assumptions about mammalian biology. Rather than being rare anomalies, glowing mammals may be far more common than previously believed.

Still, bats stand out for one reason: every specimen glowed in exactly the same way, regardless of species, age, or sex. This level of consistency suggests a shared biological origin rather than a coincidence.

An Evolutionary Relic From the Distant Past?

The uniform glow across multiple bat species hints at a deep evolutionary root. Scientists suspect that this trait may have been inherited from a common ancestor millions of years ago, before these species diverged.

Steven Castleberry, a wildlife biologist involved in the study, suggests that the glow could be an evolutionary leftover—something that once served a purpose but no longer does.

“It may be an artifact now,” Castleberry explained. “Perhaps glowing had a function in the past, but that function has since disappeared.”

In that sense, the glow could be compared to biological “fossil code”—a remnant of ancient adaptations that persist even after their usefulness fades.

Can Bats Even See Their Own Glow?

Another key question remains unanswered: can bats see this glow at all?

Despite popular belief, bats are not blind. Many species have functional vision, and some can even perceive ultraviolet wavelengths. The green glow emitted by their bodies falls within a range that their eyes could theoretically detect.

However, there’s a major limitation. Bats are nocturnal animals that spend their lives in caves, hollow trees, and dark crevices—environments where UV light is almost nonexistent. Even outdoors at night, UV levels are extremely low.

This strongly suggests that modern bats are unlikely to see their own fluorescence under natural conditions, raising doubts about whether the glow serves any current visual function.

Why Do the Wings Glow?

One detail continues to intrigue researchers: the glow appears mainly on the wings and lower limbs—parts of the body that are most visible during flight.

This pattern has led scientists to propose several hypotheses:

• Communication: The glow may once have helped bats recognize one another in low-light twilight conditions.

• Mating signals: It could have played a role in courtship or sexual selection.

• Predator confusion: The glow might have disrupted predators’ vision at dawn or dusk.

• UV protection: The fluorescent compounds could help shield delicate wing membranes from ultraviolet damage during daylight roosting.

At this stage, all of these ideas remain speculative. The study relied on preserved specimens, making it impossible to observe behavior or ecological function directly.

What Comes Next?

To uncover the true purpose of glowing bats, scientists will need to study living animals. Future research aims to safely expose live bats to controlled UV light to observe whether they respond to the glow or perceive it in any meaningful way.

Researchers also plan to identify the exact chemical compounds responsible for the fluorescence. In other animals, pigments such as porphyrins and pterins are known to cause glowing effects. Finding similar compounds in bats could reveal whether the glow is biologically intentional or simply a byproduct of other processes.

Environmental factors—like diet, habitat, or sun exposure—may also influence how strong the glow appears, opening up another layer of investigation.

A Hidden Light Show in the Natural World

Published in the journal Ecology & Evolution, the study adds yet another mystery to creatures already known for their remarkable abilities, from echolocation to powered flight.

While humans may never see bats glowing as they dart through the night sky, the discovery reminds us that nature still hides astonishing secrets—sometimes right in front of us, waiting for the right light to reveal them.

So the next time you spot a bat silhouetted against the moon, consider this: beneath those dark wings may lie a faint green shimmer, invisible to the naked eye, yet carrying echoes of an ancient evolutionary story still waiting to be told.