11 Surprising Animals That Glow

If you've ever observed fireflies lighting up on a warm summer evening, you've witnessed bioluminescence. However, fewer individuals are familiar with another captivating phenomenon: biofluorescence. In simple terms, this occurs when a living organism absorbs external light and then re-emits it in a different color. This phenomenon often goes unnoticed, as most people cannot see ultraviolet (UV) light with the naked eye. Thankfully, we can use blacklights to uncover the biofluorescent creatures that are hidden around us—like these 11 animals you wouldn't expect to glow.

1. Glowing Flying Squirrels

Beyond their appearances in the Rocky and Bullwinkle cartoons, flying squirrels don’t actually 'fly.' Instead, they glide, using flaps of skin to gently float downward after leaping from high places—something the typical gray and red squirrels in your backyard can’t do. One more fascinating feature that sets certain flying squirrel species apart? They glow. In 2019, scientists revealed that three species of New World flying squirrels have fur that turns a bright pink under a blacklight. Their discovery was published in a paper in the Journal of Mammalogy that year. The purpose (if any) of this biofluorescence remains a mystery.

2. Scorpions

When exposed to UV light, most scorpions emit a “soft blue-green glow,” according to a specialist from Australia's Queensland Museum. These nocturnal arachnids tend to avoid UV light, including moonlight. It’s speculated that this glowing trait serves as an alert system, preventing scorpions from venturing out during bright, moonlit nights when they’re more vulnerable to predators.

3. Corals

Though they may appear plant-like, corals are actually animals—and some of them are biofluorescent creatures that house symbiotic algae providing them with nutrients. These glowing corals can put on stunning light displays, benefiting both nature film crews and the algae. By absorbing light, these corals protect the algae from harmful UV rays and even aid in their photosynthesis process.

4. Catsharks

A 2014 study discovered over 180 species of biofluorescent fish, including eels, rays, and gobies. Some catsharks—small predators with long eyes—were also on the list. Although humans can't see the colors, research using a “shark’s eye camera” revealed that two species, the chain catshark and the swellshark, can see each other’s biofluorescence. Interestingly, the glowing skin patterns of wild swellsharks become more defined as the fish descend deeper.

5. Sea Turtles

While searching for biofluorescent sharks in the Solomon Islands in 2015, marine biologist David Gruber and his team spotted a hawksbill sea turtle. The camera’s blue light caused the turtle to glow, illuminating its shell with neon hues. “It almost [looked] like a red and green spaceship,” Gruber told National Geographic. This was the first recorded instance of biofluorescence in a wild reptile. Since these turtles live near glowing reefs, this adaptation may help them blend into their environment—or it could simply be a side effect of the algae on their shells.

6. Platypuses

With their duck-like bills, beaver tails, and venomous feet, platypuses already seem strange enough. But in 2020, scientists discovered that these egg-laying mammals from Australia are also biofluorescent. Their fur emits a soft glow in blue, teal, and green under UV light. The cause of this colorful glow remains a mystery.

7. Puffins

Found along the rugged coastlines of Ireland, Scandinavia, Russia, France, Northern Canada, and Maine, the Atlantic puffin sports a vivid beak designed to hold fish. In 2018, ornithologist Jamie Dunning observed a UV light illuminating the bill of a puffin carcass, causing certain ridges to glow neon blue. Scientists speculate that this glowing feature may be attractive to potential mates.

8. Budgerigars

Widely popular among first-time bird owners, budgerigars—often called “budgies” or “parakeets”—are available in pet stores worldwide. These friendly and social birds look even more striking under a blacklight. Studies have shown that female budgies use the biofluorescence of their plumage as a way to evaluate potential mates.

9. Opossums

Teddy bears were famously named after U.S. President Theodore Roosevelt. In 1909, toy manufacturers tried to replicate this success with the launch of “Billy Possums,” named after Roosevelt’s successor, William Howard Taft. Unfortunately, these marsupial dolls didn’t last long, and by 1912, they had become a forgotten novelty. Who knows? Maybe Billy Possums would have fared better if the knowledge that real opossums are biofluorescent had been widespread at the time. As with other glowing creatures, the reason behind the opossums' glow is still unknown.

10. Springhares

For years, springhares left scientists scratching their heads. These nocturnal rodents, roughly the size of rabbits and resembling kangaroos in some ways, were initially grouped with other animals before being classified into their own taxonomic family. And just when researchers thought they had them figured out, a new surprise came: In February 2021, scientists revealed that springhares from South Africa and East Africa turn pinkish-orange under UV light. “We were equally shocked and thrilled. We had so many questions,” Eric Olson, one of the scientists behind the discovery, told The New York Times. Unlike other glowing nocturnal animals, the springhare is an Old World placental mammal—the first known species in this group to exhibit biofluorescence.

11. Pac-Man Frogs

In 2020, biologists Jennifer Y. Lamb and Matthew P. Davis studied 32 species of amphibians across 14 different families. They discovered that all of them, including the eastern tiger salamander and Ceratophrys cranwelli, also known as the “Pac-Man frog,” were biofluorescent. Much remains unknown about the reasons behind this glowing phenomenon in amphibians. Speaking to Mytour last year, David said, “Now that we know this phenomenon exists across amphibians, there’s a wealth of interesting avenues that future researchers may explore.”