Mimic octopus

The mimic octopus lives in warm, shallow seas.

It lives on soft sand and mud, near where rivers flow into the sea. It hides in holes in the sand.

Mimic octopuses live in warm seas in Southeast Asia and nearby areas. In the first study, they were found on silt and sand near river mouths, in water 2 to 12 meters deep. That sea floor is full of worms, crabs, fish and other animals, which dig burrows, tunnels and mounds everywhere.

The octopus does not dig its own home. It moves into empty burrows left by other animals and may stay in one hole for one to four days before moving on.

The IUCN assessment lists the species from Australia (Northern Territory and Queensland), Cambodia, China, Indonesia, Malaysia, New Caledonia, Papua New Guinea, the Philippines, Thailand and Viet Nam, and in the Red Sea region from Eritrea, Saudi Arabia, Sudan and Yemen, at depths of 0.5 to 37 meters. Norman and colleagues (2001) described the habitat as silt and sand substrates off river mouths, 2 to 12 meters deep, rich in burrowing infauna.

SeaLifeBase, citing the FAO catalogue of the world's octopods (Jereb et al. 2014), reports that it occupies the vacated burrows of other animals, either temporarily or as part of a network of lairs within a home range, staying in one hole for one to four days.

The mimic octopus eats small sea animals and fish that hide in the sand.

It pokes its long arms into holes to find them.

Mimic octopuses hunt in the daytime for small crustaceans and fish that live in burrows in the sand. They crawl along the bottom in plain brown colors and poke the tips of their long arms down holes to reach their prey.

They have another trick too. Scientists watched mimic octopuses go right into a tunnel and come out of another hole up to a meter away. The researchers did not know of any other octopus that hunts through underground tunnels.

Norman and colleagues (2001) describe foraging individuals crawling over the substrate in drab brown colors, probing holes with their arm tips and using the flared webs between the arms to trap fleeing prey; the prey are mainly burrowing crustaceans and fishes. SeaLifeBase lists crustaceans and fishes as its food.

The octopuses also threaded their long arms down burrows and, unusually, entered a tunnel completely and emerged from another hole up to 1 meter away. The authors knew of no other octopus that forages through subterranean tunnels.

When a fish comes near, the mimic octopus can pretend to be something else.

It can swim flat like a fish, spread its arms like a lionfish, or wave two arms like a sea snake. That may help keep hungry fish away!

Scientists watched nine mimic octopuses in Indonesia. Here are the disguises they were sure about. Flatfish: the octopus pulls its arms into a flat leaf shape and swims along the bottom, rippling like a sole. Lionfish: it swims with its striped arms trailing out like a lionfish's spines. Sea snake: it hides six arms in a hole and waves the other two, striped and wiggling, like a sea snake.

The sea-snake display was seen when small damselfish attacked the octopus. All three animals it copies can be dangerous to predators, so pretending may help keep hungry fish away.

Norman, Finn and Tregenza observed nine adults over 16 days of daytime dives off northern Sulawesi and Gilimanuk, Bali (1998 to 2000), recording more than 6 hours of video. Mimic octopuses typically sat in burrow mouths. They were confident of three impersonations: a banded sole (Zebrias), seen during fast swimming; a lionfish (Pterois), shown by four individuals; and a banded sea snake (Laticauda), with six arms in a hole and two raised and undulating, elicited on four occasions by attacking damselfish. Two individuals used all three.

They suggested, more tentatively, that arms raised in zigzags may mimic stinging sand anemones and that a slow, sinking display may mimic jellyfish, and noted that human interpretations are subjective. All three firm models carry toxins. Whether the octopus is itself toxic is unknown; its regular camouflage suggests it is not toxic to at least some predators.

Mimic octopuses are not in danger right now.

People can help sea animals like them by keeping trash and pollution out of rivers and the sea.

The IUCN Red List lists the mimic octopus as Least Concern, which means it is not thought to be in danger right now. But scientists do not know whether its numbers are going up or down.

Some are caught alive for home aquariums, and the IUCN warns that pollution from towns, factories and farms, washing out of nearby rivers, could harm it too.

The IUCN assessed Thaumoctopus mimicus as Least Concern (assessed 2016, published 2019), with an unknown population trend. It is harvested for the live aquarium trade, where the assessment notes that high death rates during capture could make collecting a threat, though its scale is unknown; the other listed threats are pollution from domestic and urban waste water, industrial and military effluents, and agricultural and forestry effluents, since it often lives near river outflows.

The species was described only in 2005, and its population trend, life history and the full range of its mimicry are still largely unknown.