There has been a spike in killer whales attacking boats off the coast of Spain, causing them to sink.

It's believed that they might have been doing this after an incident that involved their matriarch, who it's believed was either struck by fishermen or caught in fishing nets.

The insight has come from experts who have been keeping a record of over 100 orca 'interactions' that have been happening since 2020, in which orcas have rammed boats or spun them around.

So far, three boats have sunk due to attacks from gangs of whales.

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The most recent attack came this week when British sailor April Boyes had her yacht destroyed by a group of killer whales that continuously rammed into the vessel for over an hour.

The attack happened just off the coast of Gibraltar and resulted in the four-person crew onboard having to be rescued by Spanish coastguards.

Boyes, 31, posted a video on Instagram highlighting the attack with the description: "What started off as a seemingly unique encounter ended with orcas breaking off our rudder from the boat, then proceeding to tear bits off the boat for an hour.

"A huge hole in the hull meant we had water ingress to other parts of the boat and the engine room, and I can honestly say it was a scary experience. We are all safe. I’m feeling grateful for the coastguard."

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But why are these attacks occurring?

It's believed that the behaviour among the sea-dwelling mammals is spreading across the pods due to social learning. In fact, each 'attack' follows the same pattern, showing that the orcas are likely to be mimicking actions they've already seen.

The assaults are mostly directed at sailing boats, with orcas approaching the vessel from the stern in an attempt to strike the rudder.

However, once the boats stopped, the killer whales often lose interest and find something else to occupy them.

Perhaps to them it is a game, but the incidents have caused some fear in sailors and resident boaters in the area.

Alfredo López Fernandez, a biologist at the University and representative at Atlantic Orca Working Group, believes that a female matriarch called White Gladis who suffered a 'critical moment of agony' is the catalyst for the series of attacks.

"That traumatized orca is the one that started this behaviour of physical contact with the boat," explained López Fernandez.

He continued: "We do not interpret that the orcas are teaching the young, although the behavior has spread to the young vertically, simply by imitation, and later horizontally among them, because they consider it something important in their lives."