Scientists in Georgia have confirmed an eerie trait in familiar night fliers. Six North American bat species emit a distinct green glow under ultraviolet light. The find came from a careful survey of 60 museum specimens and revealed a consistent pattern across sexes, ages, and species. Wings, hind limbs, and the tail membrane lit up every time.

As the University of Georgia’s Steven Castleberry put it, “It’s cool, but we don’t know why it happens. What is the evolutionary or adaptive function?” reports University of Georgia News.

North American bats are emitting a green glow under ultraviolet light.

What the Study Saw—and Didn’t

The team worked inside the Georgia Museum of Natural History, not in caves or forests. That control mattered. Each of the 60 specimens—big brown, eastern red, Seminole, southeastern myotis, gray, and Brazilian free-tailed—displayed the same shade and placement of green photoluminescence.

The uniformity means the glow is unlikely to help with mating or species ID. UV-triggered light also appeared regardless of how long a specimen had been archived, according to Discover.

The phenomenon was first confirmed by scientists at the University of Georgia.

A Clue in Common Ancestry

The identical wavelength and body-map suggest a shared lineage for the trait.

“The data suggests that all these species of bats got it from a common ancestor. They didn’t come about this independently,” Castleberry said, as noted by Phys.org. If so, the glow could be a vestige—useful long ago, less so today—or it could still carry subtle behavioral value that field studies have not yet captured.

Can Bats Even See the Glow?

Bats likely perceive the emitted wavelengths. But that doesn’t solve the puzzle. Night roosts are dark, and moonlit skies aren’t UV-rich. Whether enough natural light exists to trigger meaningful signals in the wild remains uncertain, reports ScienceAlert. The glow’s placement—on wings and lower limbs visible in flight—hints at communication potential, yet proof will require live, behavioral research.

Six species were found to share this glowing trait.

More Than a Halloween Trick

Other mammals glow, too—platypuses, squirrels, and pocket gophers among them. Yet function keeps slipping from scientists’ grasp. In rats, removing fur glow didn’t change behavior toward models, suggesting photoluminescence may sometimes be neutral, according to Discover.

Lead author Briana Roberson stresses the open questions: “It’s possible for glowing functions to be more diverse than we previously thought,” she told University of Georgia News.

Next Steps in the Dark

Proving function means watching live bats under natural conditions. If the glow enables communication—between mothers and pups, or among foraging groups—researchers will need to catch those signals in action. For now, the green sheen looks inherited and widespread. The mystery is why it stuck around.

“We’re trying to understand why these animals glow,” Castleberry told Phys.org. Until fieldwork brings answers, the bats keep their secret.