Bats that shine in the dark are nature’s Halloween surprise
Bats that shine in the dark
Every October, bats become icons of mystery and folklore. They’re silhouettes on the darkening sky, darting through the chill air. But this year, science has added a new layer of intrigue: some bats glow under ultraviolet light!
Researchers from the University of Georgia’s Warnell School of Forestry and Natural Resources said on October 20, 2025, that six North American bat species emit a green fluorescence when exposed to UV rays. It’s the first documented case of such a phenomenon in bats from this region. And it’s leaving scientists both thrilled and puzzled.
The finding opens a portal into a hidden spectrum of life. For decades, biologists have known that certain insects, fish and birds interact with ultraviolet light, but discovering this trait in bats — animals that have evolved to navigate the night using sound rather than sight — upends existing assumptions.
The scientists published their findings in the peer-reviewed journal Ecology and Evolution on July 28, 2025.
When science meets the supernatural
The research team examined 60 preserved bat specimens from the Georgia Museum of Natural History under ultraviolet lighting. When the UV beam hit them, their wings and hind limbs gave off a subtle but unmistakable green glow. Using light measurement tools, the scientists confirmed the emission was consistent across individuals and species.
That consistency is what makes the discovery so significant. If the glow had appeared only in a few individuals, it might have been dismissed as an environmental artifact. Perhaps a residue from diet, soil or preservation chemicals.
But finding the same green fluorescence in multiple species, across both sexes, suggests something far deeper: a biological trait encoded in the bats themselves. This points to a shared genetic origin or a long-standing evolutionary adaptation. According to lead author Briana Roberson:
The color and placement of the glow point toward a genetic basis. It’s likely not environmental or diet-related.
The glowing group included the big brown bat, eastern red bat, Seminole bat, southeastern myotis, gray bat and Brazilian free-tailed bat.
The enchanted unknown
Steven Castleberry, wildlife ecology professor and co-author of the study, commented:
It’s cool, but we don’t know why it happens. We’re trying to understand whether it serves any evolutionary or ecological function — or if it’s simply a byproduct of something else.
So what purpose could this luminescence serve, if any? The research team ruled out some of the usual suspects. The glow doesn’t differ between males and females, so it probably isn’t used for mate attraction. Nor does it vary across species, suggesting it’s not a form of interspecies signaling.
Instead, the scientists propose that it may be an inherited trait with deep evolutionary roots. Castleberry said:
Our data indicate the trait may have come from a common ancestor. It could be a leftover adaptation — something that once had a function but doesn’t anymore.
Understanding traits like these could help biologists decode how bats have adapted over millions of years and how they might respond to future environmental shifts.
Other creatures that shine
While bats are new members of the UV-glow club, they’re in fascinating company. Several mammals – such as flying squirrels, opossums and even pocket gophers – also fluoresce under ultraviolet light.
In other animal groups, the phenomenon is widespread: parrots’ feathers, scorpions’ exoskeletons and many deep-sea organisms all produce eerie, glowing patterns that can serve purposes from communication to camouflage.
For nocturnal animals, fluorescence might offer an invisible channel of communication. It would be visible to their UV-sensitive eyes but hidden from most predators. Whether bats use it this way remains to be seen, but as Roberson noted:
It’s possible that glowing functions are more diverse than we’ve realized.
The light ahead
As researchers continue to investigate, one thing is certain: this discovery opens an entirely new window into bat biology. What started as an unexpected flash of light in a laboratory could illuminate unseen aspects of how these animals interact, evolve and perceive their world.
For now, the reason behind the glow remains one of nature’s quiet mysteries. It’s an evolutionary ember still flickering in the night. And as Halloween approaches, it’s a reminder that the real magic often lies not in folklore, but in the science that brings those legends to life.
Bottom line: A team of scientists has discovered six species of bats glow under ultraviolet light, but they don’t know why yet. Here’s why this is a mystery.
Read more: Not all bats are bloodsuckers! More on this Halloween icon
Read more: How do bats avoid collisions in massive groups? Now we know!
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