Habitat Octopus tetricus occurs in the
intertidal zone along rocky shores and seagrass beds, and in the ocean, out up to ,
O. tetricus has been observed shifting and transporting sediment and shells to maintain their dens. They tend to have a preference for materials that are free from barnacles and encrustations, although the scale on which this is the case is dependent on foraging success. A solid object can serve as a good den that can also be the start of a new settlement for
O. tetricus. Studies show that
O. tetricus has higher populations in patch reef habitats than broken reef habitats, and were scarcely found on flat reefs. Adult
O. tetricus were also found to occupy coastal reefs in the summer and then disappear around the second week of April, which is the second week of autumn in Australia. Shelters serve a vital role in octopus ecology. When resources are scarce, such as food and dens, they will often attempt to exclude and displace other individuals. It is a territorial species which sits out the day in a lair among rocks and rubble, the rubble being collected to create a defensible lair. The lairs of this species can be identified by the shells of the octopus's prey which it scatters around its home. They move about the rocks by crawling using their arms but they can use their
siphon to propel themselves through the water by generating a jet of water or to move (throw) shells, silt, and algae, sometimes targeting other individual octopus. Throwing is a very rare and uncommon behaviour exhibited in non-humans, only seen in a few other species such as
non-human primates and
dolphins. Females have also been observed storing sperm for up to 3 months after mating, before laying any eggs. The species is generally known to be solitary, but complex social behaviours have been observed by scientists. Animals that predate on
O. tetricus include some species of
dolphin, the
short-tail stingray (
Dasyatis brevicaudata),
southern eagle rays (
Myliobatis goodei),
wobbegong sharks, and some fish. Fish, however, usually attack when in schools, such as
Chinaman leather-jackets. There is no evidence to suggest that any one species solely relies on
O. tetricus as a food source. Generally,
O. tetricus are considered a solitary,
crepuscular species, meaning they emerge from their dens to hunt and feed alone at dusk and dawn before returning to the safety of their enclosures to consume prey and to spend their daytime. Contrary to this, it is believed that the solitary, nocturnal behaviour is context-dependent. In high densities of the species, individuals become much more social and active during the day. This could be due to a greater sense of safety and protection when in larger groups. Differences in behaviour between sexes of the species are apparent, such as males being less likely to modify dens and shelters compared to females. Using properties of skin is a significant element to both combative and courtship types of behaviour. They are also able to communicate with other octopus without disrupting their crypsis, meaning they do not have to be vulnerable in order to communicate with each other. Changes in skin properties can be used to signal that they feel threatened, for example when faced with a predator, or when a female rejects a males advances for mating. However, it does not play a role in females selecting male mating partners. == Fisheries ==