under the sea


Living in the Illawarra, there are not many of us who don't have a passion for our coastline. But there are other, shyer, residents who share this love of the sea

Meet Octopus tetricus, or the Common Sydney Octopus – they are usually hidden in crevices and caves in rockpools, and found at up to about 60m depth. But if you are lucky, you might see one ambling about on the rocks in the Illawarra, in the afternoon at low tide on an overcast day.

Did I say 'ambling'. Yes! At low tide, how else can an octopus move between rockpools to forage or look for a mate? They 'walk' using their eight suckered arms. (Sometimes misnamed tentacles, these are technically arms. It is only the squid and cuttlefishes that have a pair of tentacles.)

While the threat of predators, such as seabirds, makes this a bit of a risky business for an octopus, nevertheless they venture out if they feel the coast is clear. All cephalopods are carnivores and nothing excites an octopus more than a tasty crab, but they also eat other marine invertebrates (animals without backbones) as well as fish. They are even capable of opening or drilling into hard shells to reach their succulent contents.

Sometimes an octopus lair can be found because of the piles of empty shells close to its opening.

The Common Sydney Octopus was, until recently, restricted in distribution to the east coast of mainland Australia, but due to global warming resulting in the warm East Australian Current now extending further and further south, the tiny juveniles have made it to survive in Tasmania.

This was first noticed by lobster fishermen, who found them turning up in their lobster pots. Their passion for crustaceans means they are not welcome competitors to these fishermen, who already have enough of their own resident octopuses to deal with.

Octopuses have gained a bit of a reputation due to their perceived intelligence (which has even been applied to picking football scores). They can successfully negotiate mazes and open jars to extract a tasty food item. But octopuses are just doing what they do naturally. In the wild they need to be able to map read to explore their surroundings to look for food or mates and return to the safety of their lair to hide or lay their eggs. They need to use their arms to extract a prey item from its hiding place. So, we should not be so surprised.

I think we are hugely fortunate to have these fascinating creatures as neighbours, and if you happen to run into one on an afternoon stroll along the Illawarra coastline, be sure to stay quiet, take in its beauty and let it go about its business.

Words: Dr Mandy Reid
Dr Mandy Reid lives in Thirroul and works at the Australian Museum in Sydney, where she is the Collection Manager for Malacology (snails, squid and the like). Her special research interest is in cephalopods (squids, cuttlefish and octopuses) and also has the responsibility for the care of over 11 million mollusc specimens in the museum collections.

Image: Alex Pike