Scientists solve the mystery of why killer whales are attacking boats worldwide – as astonishing footage shows a pod of orcas sinking a vessel off Portugal

Astonishing footage has emerged of killer whales targeting two tourist boats in Portugal this weekend^[1]. 

A pod of the animals repeatedly rammed and sank a yacht full of tourists off the coast of Fonte da Telha beach, while a second vessel further north off Cascais was also targeted. 

Thankfully, all nine people on board the two vessels were rescued by nearby tourist boats before official lifeguards reached the scene. 

But they join a long list of orca incidents in the last few years, where vessels have been targeted in the Bay of Biscay, the Moroccan coast, the North Sea, and more. 

Now, scientists reveal why killer whales attack boats – and it turns out we may have misunderstood these highly intelligent creatures. 

In actual fact, the orcas are just playing. 

Renaud de Stephanis, president of the Conservation, Information and Research on Cetaceans (CIRCE) in Spain, said this behaviour is ‘playful, not aggressive’.

‘What is happening with the Iberian orcas and boats is not an attack in the sense of aggression, predation, or territorial defense,’ he told the Daily Mail. 

Footage shows several orcas chasing the boat before they start violently slamming against it, sending the sailors into a panic

This is the astonishing moment a pod of killer whales rammed into a tourist boat and caused it to sink in Portugal

‘This interaction is closer to a game than to an attack. 

‘They are not mistaking the boats for prey, nor are they defending territory.’ 

Despite often being referred to as ‘killer whales’, orcas are actually the largest member of the dolphin family and are not whales at all. 

These marine mammals are recognisable from their distinctive black and white bodies, white eye patches and white bellies. 

They are ‘extremely intelligent and playful animals’, said the expert, and their primary interest in a situation like this is the underside of the boat and moving rudders. 

‘What we have been documenting in the Strait of Gibraltar, the Gulf of Cádiz, and Portugal is a game-like behaviour developed by a small subpopulation of orcas,’ Dr de Stephanis said.  

‘They focus on the rudder of sailboats because it reacts dynamically when pushed – it moves, vibrates, and provides resistance. 

‘In other words, it is stimulating for them.’ 

Orcas called ‘killer whales’ even though they are dolphins. The animals are the apex predators of the ocean, and are known to prey on a wide variety of species, including the calves of humpback and grey whales (stock image of orcas)

In August, Maritime Rescue received an alert about the interaction of several orcas with the German-flagged sailboat Ávila north of Cíes, Spain

Dr Clare Andvik, a marine mammal expert at the University of Oslo, agreed that these orcas are ‘engaging in playful behaviour’. 

She called this recent event in Portugal ‘very unfortunate’ as it is the first time the boat has actually sunk after an interaction. 

‘It is exciting and rewarding for them to play with the rudder of a boat – it is a big object that extends down into the water and moves around when they hit it,’ Dr Andvik told the Daily Mail. 

‘Even more fun for them is if a human is trying to and steer the rudder as well, then they get a bit of resistance and it is almost like a type of tug of war. 

‘Of course from the human perspective this kind of behaviour is not at all fun and it doesn’t seem to them like a game as they are getting knocked around. 

‘And in some cases the rudder can be broken off completely and cause the boat to take on water and eventually sink [which is] fun for the orcas, not for the humans.’ 

According to Dr de Stephanis and CIRCE, the best advice for people on orcas if they spot orcas is ‘do not stop’. 

This actually goes against recommendations given in Portugal, where some authorities advise boats to stop when orcas appear. 

Orcas – also known as killer whales – are one of the most recognisable marine mammals, with their distinctive black and white bodies, white eye patches and white bellies

‘From a scientific perspective, this [advice from authorities] is counterproductive,’ he told the Daily Mail. 

‘Orcas are interested in kinetic energy – they interact with moving objects. If the boat stops, the rudder becomes “easy prey”, and the interaction can last much longer.

‘If the vessel keeps moving, the dynamics make it less interesting and the orcas usually lose interest much sooner.

‘Maintain course and speed (as safely as possible), and the interaction will normally end quicker.’  

Dr Andvik, meanwhile, suggests sailors and cruisers to drop the sails, ‘turn on the motor and drive as fast as possible towards shore’ to avoid damage to the boat. 

She also suggests staying in shallow water where orcas are less likely to be and trying not to steer the rudder back (a ‘do not engage’ approach to their play). 

Orcas are the apex predators of the ocean, and are known to prey on a wide variety of species, including the calves of humpback and grey whales. 

When hunting larger prey, orcas take turns ramming their victim at 35 miles per hour, as well as biting its flesh and blocking its blowhole until it eventually drowns. 

Pictured, an orca encroaches upon a sailing boat during an hour-long attack off the coast of Morocco, 2023

Orcas even target and kill great white sharks and blue whales, the largest animal known to have ever existed. 

But if humans fell into the water they’re very unlikely to become an orca’s next meal.  

‘They are also highly intelligent and do not mistake humans as prey – they can tell we are not a whale or seal or fish,’ Dr Andvik said. 

‘If a human fell in the water while the orcas were killing a blue whale they would not be mistaken for prey, but may end up getting hit by all the flailing fins and being harmed in that way by getting in the way.’