This octopus preys — and mates — a little differently

Aug 28, 2015

“I like other marine animals, but octopuses — they’re aliens on our planet. They're the closest thing we're going to get to that.”

So says Richard Ross, a senior biologist at the Steinhart Aquarium in the California Academy of Sciences. “They have eight arms, they have suckers all over the place, they have great eyesight, they can make ink, they can swim, they have jet propulsion…The more we learn, the more interesting they become,” Ross says.

Now, Ross has discovered, in the larger Pacific striped octopus, some new and unexpected practices.

“They [have] a bunch of the weird behaviors,” Ross says. “The two biggest, weirdest behaviors are the way this octopus mates and the way it hunts food. The hunting of food is pretty spectacular.”

You know when you're sitting or standing with somebody and you reach around to tap them on the shoulder, but they don't know it's your arm behind them? That’s what these octopuses do to their prey, Ross says.

“Most other octopuses just pounce,” Ross explains. “These guys stalk up and slowly reach an arm up and over the shrimp and tap it behind it and make it run towards the octopus.”

Researchers have no idea whether the tapping trick is a learned behavior or something hardwired into their genes — but they sure would love to know, Ross says.

The mating behavior is even weirder, according to Ross. In general, octopuses want to get away from each other, because they tend to eat each other — or at least, that's the prevailing wisdom, Ross says. So normal octopuses mate either from a safe distance away, with the male's special spermatophore-depositing arm reaching out across the female, or the male will mount the female up on the mantle, behind her and away from her arms and mouth. The larger Pacific striped octopus has a different approach.

“These guys mate beak to beak, or sucker to sucker,” Ross says. “Underneath the octopus where the arms all go together and the suckers come to a point — that’s where their mouths are. And these guys mate with their faces pressed together, their arms touching and their suckers all lined up. It’s incredibly unusual, very strange.”

The larger Pacific striped octopus also lays its eggs differently than almost every other octopus, except its cousin, the lesser Pacific striped octopus. The females lay multiple clutches of eggs and when the female is brooding, she sits at her den with her mouth parts and her suckers exposed at the entrance, presumably to protect them, Ross says.

“You know how around Mother's Day we get that story about the octopuses — that the mother gives all and she tends her eggs and then she dies? These guys, not so much,” Ross says.

By the way, if you want to appear insufferably smart to your friends, you can teach them the correct plural of octopus.  

“‘Octopus’ comes from Greek,” Ross explains, “so the right way to say the plural of octopus would be ‘octopodes’ (oc-TAH-po-dees)— but people will hit you if you say that, so I don't recommend it. ‘Octopuses’ is more correct, but ’octopi’ is also acceptable, because when you bring words in from other languages to English you can Latinize them. But we all use ‘octopuses.’”

This article is based on an interview that aired on PRI's Science Friday with Ira Flatow