A fish living in coral reefs near Australia uses scent to deter predators, exclusively eating the Acropora coral to ingest its chemicals and take on its smell.
This unique tactic allows orange-spotted filefish to hide from cod and other predators, National Geographic reported.
The findings, which were published on Dec. 9 in the journal Proceedings of the Royal Society B, mark the first time researchers have found that an animal uses its diet to guard against predators.
"Most of the literature on camouflage focuses on visual methods, but many animals use smell more. For these animals, chemical camouflage may be far more important to stay hidden," said lead researcher Rohan Brooker, as quoted by National Geographic.
Brooker and his colleagues took filefish from water close to the Lizard Island Research Station on the Great Barrier Reef and split them into two groups: one that ate the fish's usual Acropora diet and one that consumed Pocillopora damicornis coral.
The team tested to see if the fish smelled like coral by using two species of small crab that live in the respective kinds of coral. The crabs that typically live in Acropora coral strongly favored the filefish that consumed that type of coral, and some of them even treated the fish as if they were coral.
"Crabs also exhibited a similar preference for the odor of filefish fed their preferred coral and odor directly from that coral, suggesting a close chemical match," the researchers wrote in the study abstract.
For the next step, the researchers placed a predatory cod species in the aquariums to find that the cod spent less time hunting near the filefish that regularly ate Acropora, suggesting that the cod couldn't find the filefish that consumed that particular coral.
"This is, we believe, the first evidence of diet-induced chemical crypsis in a vertebrate," the researchers said.
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