The cassowary already had a reputation as the most dangerous bird on the planet, capable of seriously injuring someone with a single claw. What no one suspected was that beneath that fierce appearance it held another secret, one visible only under ultraviolet light.
It all started by accident. Museum caretakers were using black light to detect fungi in taxidermied specimens when they noticed that the bird’s bony casque lit up blue-green. A team led by Todd L. Green confirmed the phenomenon in 95 cassowaries, including live birds and preserved specimens, and published it in Scientific Reports in February 2026.
Most intriguing of all: each species—Casuarius bennetti, C. casuarius, and C. unappendiculatus—glows with a different pattern, like its own signature of light. Scientists suspect it could be a way for them to recognize one another in the dim light of the forests of Australia and New Guinea, although there is still no evidence that it serves that function in nature. We had been studying this bird for more than a century without noticing it.
