Talented octopus dupes predators by impersonating fish

The Indonesia mimic octopus doing an impersonation of a toxic flatfish

The Indonesian mimic octopus has the extraordinary ability to pass itself off as many of the toxic fishes or sea snakes that share its habitat.

A new study of its DNA suggests why these abilities evolved.

Instead of blending into the background, the animal impersonator often uses a daredevil strategy of making itself more conspicuous to predators.

Scientists believe the behaviour evolved to scare other animals.

First described by scientists in 1998, the Indonesian mimic octopus (Thaumoctopus mimicus) is able to pass itself off as a number of its near neighbours.

By flattening its head and arms, using a bold brown and white colour display and adopting an undulating swimming technique T. mimicus can fool predators that it is, in fact, a poisonous flatfish rather than a tasty meal.

Because this high risk defence strategy is quite rare, scientists from the California Academy of Sciences and Conservation International Indonesia were keen to understand how its abilities evolved and why they are used.

Dr Christine Huffard from Conservation International Indonesia is one of the authors of the study published in the Biological Journal of the Linnean Society.

"The close relatives of T. mimicus use drab colours and camouflage to successfully hide from predators." she said. "Why does T. mimicus instead draw attention to itself, and repeatedly abandon the camouflage abitilies it inherited from its ancestors in favour of a bold new pattern?"

By analysing its DNA the researchers established when different traits appeared in its ancestors' lineage from its brown-and-white colour displays to its ability to swim like a flatfish using its long arms.

The researchers believe its impersonation skills were advantageous because the mimic could fool predators into thinking it was a poisonous flatfish like the peacock or zebra sole which lives nearby.

Dr Healy Hamilton is Director of the Center of applied Biodiversity Informatics at the California Academy of Sciences.

"While the mimic octopus's imitation of flatfish is far from perfect, it may be 'good enough' to fool predators where it lives... In the time it takes a predator to do a double take, the octopus may be able to get away," she said.

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