"Researchers are unsure... but theories include that it is a playful manifestation of the mammals’ curiosity, a social fad or..."

"... the intentional targeting of what they perceive as competitors for their favourite prey, the local bluefin tuna."

From "Yacht sinks after latest incident involving orcas in strait of Gibraltar/Vessel measuring 15 metres in length sank after encounter with the animals, Spain’s maritime rescue service reports" (The Guardian). 

Also: "Experts believe them to involve a subpopulation of about 15 individuals given the designation 'Gladis.'"

From last year in The Guardian: "The orca uprising: whales are ramming boats – but are they inspired by revenge, grief or memory?" That's a much more interesting article....

There are two fascinating things about this. First, of course, what are the orcas doing? But the second is about another species entirely: us. Why do we like this story so much? Because we do: people – including me – love the idea of orcas attacking boats. Browsing through orca memes, there’s an orca as the sickle in the hammer and sickle, with the headline “eat the rich”, and a Soviet-style graphic of a heroic orca emerging under a superyacht. “What if we kissed while watching the orcas take back the ocean,” reads one tweet with 1m views, while a much-used image of an arm holding a microphone up to a captive orca has been repurposed endlessly to highly entertaining effect – I like one where it’s “singing” a bespoke version of the Meredith Brooks classic: “I’m a bitch / I’m an orca / Sinking yachts /Just off Majorca [sic] / I’m a sinner I’m a whale / Imma hit you with my tail.”... 

The fibreglass hulls of sailing boats might just feel nice – and orcas enjoy the sensory feedback: some Canadian pods seem to enjoy rubbing themselves on smooth pebbles (you can watch them on a webcam); or it might just be a trend. As Mustill explains, a number of observed orca fads are not obviously examples of “adaptive” behaviour (meaning “useful”) – most famously the one for wearing salmon as hats....

Salmon hats??? It happened back in 1987:

In the Puget Sound area of the northeast Pacific, one female orca from k-pod began carrying a dead salmon around on her nose. Over the next 5-6 weeks, the behavior spread, and by the end of it, orcas from her own and two other pods were wearing dead salmon hats. Then all of a sudden, the fad was over. Bar a few times the following summer – latecomers, like humans just now deciding to wear Uggs – the trend has never been seen again....

Back to the "Orca uprising" article: 

The Atlantic Orca Working Group 2021 report also suggested the interactions might be responding to individual orcas’ experiences: “A behaviour induced by an aversive incident, and therefore a precautionary behaviour.” Given a single “matriarch” orca, “White Gladis”, appears to have started these interactions, it has been suggested a prior injury or entanglement could have led her to act. Does that make it revenge? King doesn’t dismiss the idea out of hand. “If we’re talking about capacity, it’s not outside the realm of reasonable expectation and it would not necessarily be anthropomorphic,” she says, though, “I’m not suggesting this in support of an ‘uprising’ at all.”... 

As demonstrated by the actions of White Gladis, orca society is matriarchal, and females can live to 100: “They will have a memory, almost a generational memory, of a time when the ocean was not dominated by human beings; when there were not seismic surveys, steam engines then diesel engines, military sonar … The most important thing for them is sound: there will be individual whales that remember when the sea was not that noisy.” 

So they know what we’ve done and we know what we’ve done too. I think one of the reasons the #orcauprising resonates is our sense of collective guilt or, as Mustill puts it, “We feel like there’s something deeply unfair happening in the ocean.”... 

One very human-coloured notion is the idea that orcas aren’t just taking back the ocean but are somehow fomenting revolution, since the yachts they are ramming are so intimately associated with the ultra-wealthy. White Gladis has been called “a communist orca”. As one post reads: “The orcas have done more for the working class than our elected officials ever have”.......