Fire salamanders already look like they were painted by a toddler with only two crayons: shiny black with bright yellow spots. Turns out they had a secret colour too.
The glow
Under ultraviolet light, fire salamanders glow green and cyan. This is called biofluorescence: the animal soaks up UV light and gives it back as a different colour.
The glow comes mostly from glands in the skin and from the toxic liquid they release to defend themselves. And here's the strange part: that liquid keeps glowing for more than 24 hours after it leaves the animal.
What is it for?
Nobody knows yet. Maybe salamanders use it to talk to each other. Or maybe it makes their warning signal louder for predators: "Don't eat me, I'm poisonous, and now I'm glowing about it."
"We still don't know what the compound responsible for this fluorescence is," says Salvador Carranza, one of the researchers. The study was led by Bernat Burriel-Carranza of the Museum of Natural Sciences in Barcelona, with the Max Planck Institute for Chemical Ecology, and published in Royal Society Open Science.
Why it matters
Fire salamanders are listed as "vulnerable" on the international Red List. The poison itself was identified more than a century ago, yet this glow went unnoticed until now. Proof that even well-known animals still have surprises.
And if you find one on a forest walk? Look, enjoy, don't touch. The glow is cool. The poison is not.