The orange-spotted filefish has evolved to absorb and re-emit smelly compounds from the coral it eats, a chemical mask that makes the fish smell like its food. This act of olfactory camouflage means that, to its predators, the filefish seems to blend into the background.
Skilled predators see their prey in more than one way. Whether they're detecting motion or heat, sensing electromagnetic signals or relying on good old fashioned eyesight, many predators take a multi-pronged approach to finding dinner. Avoiding becoming their next meal, then, means working out ways to hide that foil all of these senses at once.
A few years ago researchers detailed the colorful camouflage abilities of the orange-spotted filefish, also known as the harlequin filefish or Oxymonacanthus longirostris. In that research, scientists found that the filefish has spotted markings that match the coral it usually uses as shelter, says Live Science:
They described several adaptations the fish uses to fool its predators into thinking it's a piece of Acropora coral. Its coloration and polka-dot pattern match the pattern of polyps on the surface of the coral colonies, while the lighter coloring of the tip of its caudal fin mimics the coral's growing tip.
But what good is colorful camouflage if the hunter can still sniff you out?
In new research, scientists discovered the filefish can hide their smell as well.
According to National Geographic, when the filefish get to eat and hide amongst Acropora coral, their normal meal, predatory fish have trouble finding them compared to filefish that eat and shelter in a different kind of coral.
Rohan Booker, one of the scientists behind the study, noted that this is the first documented case of a fish using their diet to camouflage in this way. Though that doesn't mean it's the only case, he says: “I suspect that this method of hiding is probably a lot more common than any of us guessed.”