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What looks like coral, smells like coral? A fish

By , 9 January 2015

two colourful fish swimming near coral.

You are what you eat, Harlequin filefish looking and smelling like coral.
Image: Tane Sinclair-Taylor

Written by Beth Askham

Sometimes smelling like your environment is the best way to blend in and hide from predators.

On the Great Barrier Reef, the harlequin filefish shelters in coral branches overnight. Researchers have found that these fish not only look like coral, they smell like it too.

“By feeding on corals, the harlequin filefish ends up smelling enough like its food that predators have a hard time distinguishing it from the surrounding coral habitat,” says study lead author Dr Rohan Brooker, a marine biologist from James Cook University. “For many animals, vision is less important than their sense of smell,” he adds.

On the reef there are many predators, so it’s worth having a good way of camouflaging yourself. Although these sneaky smells are effective, the harlequin filefish still has to be careful. Each fish has to shelter in the same coral it has eaten otherwise predators will sniff it down. And what does it smell like? We will never know, as people can’t smell underwater.

The experiment took place off the coast of far north Queensland, at the science research station on Lizard Island. Researchers studied harlequin filefish and a fish that eats them, the blue-spotted rock cod. They also studied the reaction of a small crab that lives on coral branches.

After the fish had eaten coral, the cod were less likely to notice them. The small crabs couldn’t tell the fish from coral and went towards them, thinking they were shelter.

We don’t know many animals that chemically camouflage themselves by smelling like their environment, but perhaps it’s because we haven’t looked. We tend to use our eyes more than our noses when we investigate the world. This research could be the beginning of following our noses to find a whole new world of smell-a-likes.

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