The octopus is not the most social species on the planet. Though they are very intelligent, they also tend to be very solitary, and they have a tendency to eat each other given the chance. They’re also incredibly secretive, hiding and camouflaging themselves to avoid predators and sneak up on their next meal, making them pretty hard to study.
But new evidence from a group of octopuses studied in captivity indicates that the animals aren’t always so solitary. In fact, they can be downright social, cohabitating in dens and exhibiting other behaviors strikingly unusual for octopus species, as researchers report in PLOS ONE this week. The scientists—from the Monterey Bay Aquarium Research Institute, the California Academy of Sciences, and the Smithsonian Tropical Research Institute—observed 24 adult larger Pacific striped octopuses over the course of two years.
After some of the octopuses were able to mate without eating each other (females tend to strangle and devour their mates), four pairs of octopuses were moved into communal tanks. Unusually for octopuses, these pairs mated beak-to-beak (the octopus beak is at the center of all its legs), instead of mating from a distance (using its long “special” arm). The mated pairs also spent an unusual amount of time together, with some of them even sharing a den. And the females spent an inordinate amount of time caring for their young relative to other octopuses, which often die around the time their eggs hatch. These octopuses laid eggs for up to six months and incubated them for up to eight months, laying more eggs and mating again after their first eggs had hatched.
This study confirms anecdotal evidence of similar behaviors referenced in the scientific literature from the 1970s, when the species was first being described. It suggests that we may not know the octopus as well as we think we do. However, since these behaviors were only observed in captivity among a few dozen octopuses, it remains to be seen whether wild octopuses behave in similar ways.