Common biofluorescent hues include green, red, orange, and blue. From flying squirrels to platypusīiofluorescence is the phenomenon whereby a substance, such as fur, absorbs light at one wavelength and emits it at a different wavelength. “This adds another observation that many animals are biofluorescent, and it opens up questions about what it might mean, if anything, for the species,” says David Gruber, a National Geographic explorer and researcher who studies fluorescence in marine creatures and who wasn’t involved in the paper. The finding expands science’s knowledge of biofluorescence, which researchers are finding to be more widespread throughout the animal kingdom than previously thought. “I was a little flabbergasted to the platypus is biofluorescent,” says study lead author Paula Anich-especially since it’s already “such a unique animal.”

In a recent study published in the journal Mammalia, scientists found that when illuminated by ultraviolet (UV) light-a spectrum of light not visible to human eyes-the pelts of platypuses give off a blue-green glow. Now, scientists have found yet another odd trait to add to the list: Fluorescent fur. They also have beaver-like tails and duck-like bills, the latter of which they use to sense prey while hunting at night with their eyes closed.

Though mammals, these Australian natives lay eggs and sport venomous spines on their rear legs. The platypus is one of the planet’s strangest creatures on several counts.

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