If you’ve never tried to imagine the goings-on of an octopus community, you wouldn’t be alone. These highly intelligent animals are known for being loners, preferring their “me time” to congregating in big groups.
But that isn’t always the case. There’s a place off the coast of Jervis Bay, Australia – known as Octopolis – where a surprisingly large consortium of octopuses were caught hanging out together.
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In 2012, researchers revealed this head-scratching discovery. While diving in the area, they happened to find a huge mound of shells where around 16 gloomy octopuses (Octopus tetricus) had made their home.
Gloomy octopuses are typically observed on their own so the scientists were puzzled to see so many all living together.
It seemed like this might be a strange one-off and they put the congregation down to a large piece of scrap metal that initially drew in the animals because it provided shelter. That is, until the scientists found another similar aggregation nearby that had come about naturally.
Here, they saw up to 15 gloomy octopuses getting on with their lives. These individuals weren’t just living close to each other, they were interacting – communicating, mating, fighting and even kicking each other out of dens or trying to ban individuals from the community. They dubbed this site Octlantis.
But both these ‘cephalopod cities’ pale in comparison to the mammoth Octopus Garden. In 2018, MBARI researchers discovered this octopus nursery close to an underwater volcano around two miles deep off the coast of Monterey, California.
Here, female pearl octopuses (Muusoctopus robustus) come to have their babies, finding the perfect crevice in the rock to make a nest. These little gems got their name – pearl octopus – because they looked like a clutch of iridescent pearls scattered across the seafloor when seen from a distance.
The site is teeming with pearl octopuses – scientists counted more than 6,000 individuals and believe there could be as many as 20,000.
But why do they all gather here? The deep sea is known for its chilly waters. At this depth, the water is usually around 1.6 degrees Celsius but the nests in the Octopus Garden were almost 11 degrees Celsius – positively balmy in comparison.
Researchers figured out that the nooks and crannies the mother octopuses were making their nests in were warmed up by hydrothermal springs. These snug nests meant that the eggs could hatch more quickly.
This isn’t down to laziness on the mothers’ part, wanting their little ones to leave the nest as soon as possible (octopus mums die once their eggs have hatched).
When embryos are still developing, they are incredibly vulnerable to being picked off by hungry predators. Being able to hatch more quickly likely improves their chance of surviving to adulthood.
Top image: Monterey Bay Aquarium Research Institute
