For decades, scientists have assumed so-called gloomy octopuses (or octopus tetricus) were just a bunch of loners. But now there's evidence these marine creatures hang out in small octo-cities, sometimes tens of them at a time.
An international team of marine biologists found a site of 15 of the common Sydney, Australia, cephalopods in Jervis Bay, off of Australia's eastern coast in December 2016, and appropriately named the city "Octlantis."
Lead researcher David Scheel of Alaska Pacific University told Quartz.com the discovery, published in the journal Marine and Freshwater Behavior and Physiology this month, was a surprise.
“These behaviors are the product of natural selection, and may be remarkably similar to vertebrate complex social behavior. This suggests that when the right conditions occur, evolution may produce very similar outcomes in diverse groups of organisms,” he said.
But this isn’t the first time a site like this was discovered. In 2009, researchers found another gloomy octopus site near Jervis Bay with up to 16 animals. That site was named “Octopolis.”
According to study co-author Stephanie Chancellor, both Octopolis and Octlantis had several seafloor rock outcroppings on otherwise flat and featureless grounds.
"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. These shell piles, or middens, were further sculpted to create dens, making these octopuses true environmental engineers," she said in a statement.
Does this mean octopus behavior is changing? According to Scheel, it's more likely that humans' ability to observe behavior has improved with better cameras and technology, Quartz reported.
And just because these sites may exist, doesn’t mean they’re common.
“Congregations such as these probably occur wherever shelter is limited to small patches of habitat, and food is plentiful,” he said, but added that he suspects gloomy octopuses have been socializing for a long time.
