In Brief
What do you call a hidden civilization of octopuses? Octlantis, of course, and that's not a joke. This recently-discovered cephalopod city, occupied by 15 tentacled residents, has shown scientists that the supposedly loner Sydney octopus might actually have a healthy social life.

Getting By With a Little Help

Just because they have eight tentacles doesn’t mean they have all the company they need. It turns out, octopuses found in the subtropical waters off northern New Zealand and Australia aren’t the loners they were previously thought to be. Marine biologists recently discovered that these Sydney octopuses (octopus tetricus) have a tendency to hang-out in a small “city” — dubbed Octlantis.

The international team of researchers led by David Scheel from the Alaska Pacific University found Octlantis off Eastern Australia in an area called Jervis Bay. Octlantis had 15 of these supposedly loner-type octopuses grouped together. “We recorded frequent interactions, signaling, mating, mate defense, eviction of octopuses from dens, and attempts to exclude individuals from the site,” the researchers wrote in the abstract of a study published in the journal Marine and Freshwater Behavior and Physiology.

Octalantis isn’t the first discovered city of cephalopods. Back in 2009, in what was thought to be a fluke, scientists found Octopolis — yes, they name them like that — not far away from Jervis Bay. These two hang-out spots suggests that Sydney octopuses don’t just meet once a year to mate.

octlantis animal social behavior evolution
Image credit: Scheel et al.

Environmental Engineers

Stephanie Chancellor from University of Illinois-Chicago, co-author of the new study, suggests that the Sydney octopuses are home-builders, congregating in areas with multiple seafloor rock outcroppings. “In addition to the rock outcroppings, octopuses who had been inhabiting the area had built up piles of shells left over from creatures they ate, most notably clams and scallops,” Chancellor said in a press release. “These shell piles, or middens, were further sculpted to create dens, making these octopuses true environmental engineers.”

There are number of factors the scientists will continue to study regarding this communal behavior. It’s clear, though, that it’s an evidence that animal social behavior evolves. “These behaviors are the product of natural selection, and may be remarkably similar to vertebrate complex social behavior,” Scheel told Quartz. “This suggests that when the right conditions occur, evolution may produce very similar outcomes in diverse groups of organisms.”

Octolantis and Octopolis also affirm what we know about the world’s oceans and its inhabitants: that we don’t know enough. Like deep space, the ocean’s depths have so much more to show us.