On March 18, 2021, author Lance Karlson posted a video to Instagram of an octopus in shallow water lunging toward him in an aggressive manner. "Oh. Golly," he responded in what would become the latest viral cephalopod video:
There is no reason to think the video is anything but legitimate. The video was filmed in Dunsborough, Western Australia. This region is home to the Western Australian common octopus — closely related to the common Sydney octopus but recently determined to be its own species. This species, as seen in the video, is "commonly found in and around inshore reef systems and sandy benthos" and it "completes its life cycle in nearshore and continental shelf waters."
Speaking to The New York Times, Peter Ulric Tse, a professor of cognitive neuroscience at Dartmouth College who studies octopus cognition, said that octopuses, in general, "can express what we would call aggression when they feel threatened or when they feel their territory is under threat.” Tse said that the behavior captured in Karlson's video is likely a warning not an attempted attack.
My guess is that the octopus here is sending a warning meaning 'back off' … Octopuses will lunge or shoot an arm out when they feel a fish, another octopus or a human is in their space. I think this is often pre-emptive aggression, meant to signal ‘don’t mess with me,’ rather than aggression seriously meant to harm the 'invader.'
Sadly, this cephalopod's potential warning shot was not heeded. "Amused by the interaction but ultimately unfazed, [Karlson] returned ... to the water about 20 minutes later," the Times reported. "About 30 meters out, he noticed a pile of crab shells piled neatly together. He dove underwater to take a look, and he remembered a documentary that he had watched in which he learned octopuses tended to pile up crab shells." At this juncture, Karlson was whipped on his arm and on his back by an octopus, causing modest amounts of pain.
The Western Australia common octopus is indeed a fan of crabs. In fact, the lunging behavior seen in the video resembles the tactics employed by another Western Australia octopus that went viral for successfully capturing a crab — on land — in 2015:
That video was filmed in Yallingup, Western Australia, which is right next to Dunsborough, where Karlson filmed his interaction with the defensive octopus.
Because the behavior and setting are consistent with what is known about octopuses in general, and the Western Australia common octopus specifically, we do not doubt the video's authenticity. As such, the claim is "True."