Common in the Solitary Islands Marine Park. In Australia recorded from the southern half of the continent including northern Tasmania, north to around Exmouth in Western Australia and to the Moreton Bay area of southern Queensland.
Frequents intertidal rocky shores and coastal rocky reefs. It is commonly seen in estuaries and there has been the suggestion it occurs in rocky habitat during the breeding season, spending the rest of its life in soft sediment areas.
Octopus tetricus is best recognised by a typical mottled brown to grey appearance, by the eyes which are usually white, and long tapered arms which have orange/red under surfaces adjacent to the suckers. This octopus is territorial and constructs a lair which is usually hidden behind dead shells, rocks and rubble. Females produce numerous small eggs which are attached to the upper surfaces of rock crevices and caves. The eggs hatch into planktonic young, in which state they are thought to exist for between 35 and 60 days. O. tetricus is primarily nocturnal and feeds on crabs and molluscs such as snails and bivalves. It is a master of camouflage and able to change colour and skin texture almost instantaneously. It grows to a mantle length of 30 cm and leg span of up to 2 m.
Davie, Peter. Wild Guide to Moreton Bay and Adjacent Coasts. Second Edition. Published by Queensland Museum. Vol 2, p. 188.
Australian Museum. https://australianmuseum.net.au/common-sydney-octopus-octopus-tetricus. Accessed 12/07/18.