There’s an octopus city off the coast of Australia. ‘Octlantis’ is home to about 15 octopuses who built their dens with beer bottles and leftover shells from their prey. They’ve been observed living together, mating, forming gangs to keep intruders away, and even evicting each other from their dens, which suggests they may not be such solitary creatures after all. Source Source 2 Source 3