Killer whales are teaching each other how to capsize boats with people on board, experts say.

Three whales (two smaller and one larger orca) attacked, pierced the rudder, and sank a yacht on May 4 in the Strait of Gibraltar.

Greg Blackburn, an experienced sailor from Leeds, was on the vessel when it was attacked – and reckons the mother was teaching the others what to do.

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He told 9news : "You can see in one of the videos the matriarch coming up and attacking the rudder with calf at the side of her, then she drops back and then the little calf gets in to have a go.

“It was definitely some form of education, teaching going on."

It has been reported that the targets are sailing boats, with the orcas following a clear pattern – they strike the rudder, eventually causing it to break and ultimately sink the vessel.

Reports of aggressive orcas trying to sink ships seemingly began to become more frequent around early 2020, a study published in the journal Marine Mammal Science, warned.

In the paper, entitled ‘Killer whales of the Strait of Gibraltar, an endangered subpopulation showing a disruptive behavior’ co-author Alfredo López Fernandez, a biologist at the University of Aveiro in Portugal, said: "The reports of interactions have been continuous since 2020 in places where orcas are found, either in Galicia or in the Strait.”

Fernandez told Live Science : "The orcas are doing this on purpose, of course, we don't know the origin or the motivation, but defensive behaviour based on trauma, as the origin of all this, gains more strength for us every day."

Experts believe that a female orca they call White Gladis suffered a "critical moment of agony".

This could be a collision with a boat or getting trapped during illegal fishing – and it flipped a behavioural switch "that traumatised orca is the one that started this behaviour of physical contact with the boat".

Orcas are incredibly social creatures that can easily learn and reproduce the behaviours of others.

Lopez said that orcas weren’t teaching the young directly but the behaviour was spreading by imitation.

Talking about the attacks earlier this month in the Strait of Gibraltar, Skipper Werner Schaufelberger told German publication Yacht : "There were two smaller and one larger orca.

"The little ones shook the rudder at the back while the big one repeatedly backed up and rammed the ship with full force from the side."

The skipper witnessed the smaller orcas imitating and mimicking the actions of the larger one.

He added: "The two little orcas observed the bigger one's technique and, with a slight run-up, they too slammed into the boat.

The Spanish coast guards successfully rescued the frightened crew, and while attempting to tow the boat to port, unfortunately, it sank.

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