They sound like a typical couple. A male and a female share a home. They go about their business during the day but come together for meals. After dinner, they have sex, entwined in a face-to-face embrace.

Typical, perhaps, for humans. Yet this couple is a pair of larger Pacific striped octopuses, and their behavior defies what scientists thought they knew about these denizens of the deep.

The larger Pacific striped octopus had been studied only once before, in the 1970s, by Arcadio Rodaniche of Panama’s Naos Island Marine Laboratory. Rodaniche’s reports that these octopuses were social creatures, even mating “beak-to-beak,” were dismissed. That’s because octopus sex was considered the worst one-night stand in history; it often ends in murder and even cannibalism. Males mate as far from females as possible—they even have an arm, the hectocotylus, evolved for sex from a safe distance.

But researchers from the University of California at Berkeley led by Ray Caldwell, an invertebrate biologist, spent two years in the lab observing twenty-four larger Pacific striped octopuses, who proved to be exactly as randy as Rodaniche had claimed. When they mate, these octopuses wind their arms around each other tightly, each beak—emerging from the animal’s flowerlike mouth, centered where its many arms join—touching. Their chameleon-like skin shivers from dark to light. Their bodies pulse with deep breaths.

Larger Pacific striped octopuses pair this intimacy with a level of commitment surprising for a famously antisocial cephalopod. Females will mate multiple times a week, even when they are protecting a brood of eggs. Post-coitus, they share food with males and will even let him stay in their den. Such behaviors had never been seen before in octopuses.

Caldwell hopes to continue his research on the deep, sandy mud plains off the coasts of Nicaragua and Panama, where larger Pacific striped octopuses live. Their homes are so deep—as much as 150 feet below the surface—that it is difficult and even dangerous for human divers to reach them. As a result, they’ve been seen in the wild only five times. It remains a mystery whether the social behavior Caldwell’s team observed in the lab is common out in the deep blue.

“We think we know a fair amount about octopus…when in fact we know almost nothing,” Caldwell says. “All the studies have been conducted on just a handful of species. So there are other octopus out there, living in weird places, doing things just as strange, or even stranger, than the larger Pacific striped octopus. And until we observe them in the field, we aren’t going to have much of an understanding.”