When you think of bats, you generally think of pitch-black caves and vampires. Maybe you think of the dark Batcave, while Bruce Wayne dons his batsuit and says, “They think I’m hiding in the shadows. But I am the shadows.” All of these are fitting descriptions, but six North American species of these nocturnal creatures have defied their perceived “darkness”, showcasing their own glow.
The results were reported on 20th October, stating that six bat species in North America emit a green fluorescent glow under UV light. These flying mammals are the first instance of such a glow in this specific region. Scientists have not yet discovered why mammals glow under UV light.
“What was already really established before this project, was that a lot of mammals glow under UV light. So, then the question was: Why do they glow?” said study coauthor Steven Castleberry, a professor in wildlife ecology and management at the University of Georgia. “We’re trying to learn more about bats and how they function in their environments and how they contribute to the ecosystem. … If we can figure out the function, if there is a function, it can help us to better conserve and manage these species.”
The lead author, Briana Roberson, an undergraduate at the University of Georgia, was deeply inspired by a paper on flying squirrels that stated that these mammals glow under UV light. In 2023, a study reported that around 125 mammals in Australia fluoresce. Scientists also found that the toes of Mexican free-tailed bats glow under UV.
Roberson studied big brown bats, eastern red bats, Seminole bats, southeastern myotis, gray bats, and Brazilian free-tailed bats. She shone UV light on 10 bats from every species at the Georgia Museum of Natural History in Athens, experimenting on 60 bats of different species. The hind limbs and wings showed photoluminescence.
She, along with her team, explored why the bats emitted this glow by analyzing their glow at its peak wavelength. Initially, the team thought these bats used the glow to camouflage themselves while roosting in leafy foliage during summer. However, on comparing the wavelength of the emitted glow with that of chlorophyll, this theory is unusable.
The other theory revolved around the possibility of using this glow for recognizing the opposite gender and other bats. However, there was no difference in emitted glow. Although no function of the fluorescence was uncovered, it’s one for the future. However, one theory suggests that the glow has no ecological function, or that it might have been an essential part of their life in the evolutionary past but has no apparent function right now.
Halloween might have gone, but not the spooky surprises of science. Maybe next year, you can flash UV light at Dracula, and he would possibly glow, and might not suck blood out of your neck, out of sheer joy at his newfound abilities. Don’t Count on it, though!
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