What Is Octlantis and Why Did Octopuses Build an Underwater City?

Octlantis is an underwater octopus settlement discovered in 2017 off the coast of Jervis Bay, Australia, where up to 15 gloomy octopuses live together in a complex social community. This remarkable discovery challenged everything scientists thought they knew about octopus behavior, as these creatures were previously considered strictly solitary animals.

The Discovery That Changed Marine Science

In 2017, marine researchers made an extraordinary discovery beneath the waters of Jervis Bay, Australia. At a depth of 10-15 meters, they found what appeared to be an impossible sight: an octopus city. Named Octlantis by the scientific team, this underwater settlement represents only the second recorded octopus colony ever found on Earth.

The site spans an impressive 18 meters by 4 meters of seafloor, creating a bustling neighborhood where multiple gloomy octopuses (Octopus tetricus) coexist. What makes this discovery truly groundbreaking is that octopuses have long been classified as solitary, antisocial creatures that avoid contact with their own species except during mating.

How Octopuses Built Their Own City

Perhaps the most fascinating aspect of Octlantis is its construction. The entire settlement sits atop mountains of discarded scallop shells—the accumulated leftovers from generations of octopus meals. In an remarkable example of accidental urban planning, previous octopus residents unknowingly created the foundation for future generations.

These shell middens provide the perfect substrate for den construction, offering both protection and elevation above the sandy seafloor. The octopuses have modified and expanded these structures, creating a complex network of dens and territories that can support multiple residents simultaneously.

Complex Social Behaviors in Action

Researchers observed sophisticated social interactions that were previously thought impossible for mollusks. The octopuses at Octlantis engage in clear communication through dramatic color changes, flashing dark pigmentation across their bodies to signal dominance or territorial claims.

These interactions go far beyond simple coexistence. Scientists documented octopuses actively evicting rivals from prime dens, chasing away intruders, and establishing clear territorial boundaries. Some individuals were observed stretching upright in intimidating postures—behaviors typically associated with social vertebrates, not solitary cephalopods.

Rewriting the Textbooks on Octopus Behavior

The discovery of Octlantis has forced marine biologists to reconsider fundamental assumptions about octopus social structure. For decades, scientific literature described these intelligent creatures as loners who actively avoided their own kind. The complex society observed at Octlantis suggests that under the right environmental conditions, octopuses are capable of sophisticated social organization.

This revelation has broader implications for our understanding of intelligence and social evolution in marine ecosystems. It demonstrates that complex social behaviors can emerge even in species not traditionally considered social, challenging our preconceptions about animal cognition and community formation.