Debate arises as orcas attack boats: Aggression or social learning?

Posted on 29 May 2023 By Tsoku Maela

Recent incidents of orcas allegedly attacking and causing boats to sink off the southwestern tip of Europe have raised concerns about the intentions of these animals and whether they are learning aggressive behaviour from one another.

Since 2020, there has been a growing number of encounters between orcas, also known as killer whales, and boats, although no human injuries or deaths have been reported. While most cases did not result in the sinking of vessels, a series of incidents have drawn significant attention.

A scientist in Portugal suggested that these attacks might indicate a deliberate intent by the whales to damage sailing vessels. However, some experts remain sceptical, suggesting that while the behaviour may be coordinated, it does not necessarily signify aggressive intentions.

Monika Wieland Shields, the director of the Orca Behavior Institute, a nonprofit research organization in Washington state, believes that the motivation behind the behaviour might not necessarily be aggression. She points out that the attacks are often interpreted as aggressive due to the resulting damage but suggests that other factors could be at play.

In 2020 alone, there were 15 reported interactions between orcas and boats off the Iberian coast, as documented in a study published in the journal Marine Mammal Science. In response to these incidents, Portugal’s National Maritime Authority issued a statement warning sailors about the ‘curious behaviour’ displayed by juvenile killer whales, advising caution due to their potential attraction to rudders and propellers.

The most recent incident occurred on May 4 off the coast of Spain, where three orcas struck the rudder and side of a sailing yacht, leading to its eventual sinking, as reported in the German publication Yacht.

Alfredo López Fernandez, a biologist at the University of Aveiro in Portugal, proposed a theory that suggests the aggression might have originated from a female orca that was possibly struck by a boat, leading her to retaliate by ramming sailing vessels. López Fernandez believes that other orcas could have learned this behaviour through social learning, a known characteristic of whales.

Shields, on the other hand, argues that historically, orcas have not displayed aggression towards humans, even in circumstances where they were hunted or held captive. She suggests that if revenge or direct aggression were motivations for the recent attacks, there would have been prior instances of such behaviour.

She explains that the recent boat attacks are more likely to be categorized as ‘fad’ behaviour, temporary and novel conduct initiated by one whale and mimicked by others. Shields parallels observations in the Pacific Northwest, where Southern Resident killer whales displayed fad behaviour by carrying dead salmon on their heads for a period before abruptly ceasing the behaviour.

Shields believes that the behaviour of orcas off the Iberian coast might be temporary, similar to a fad, where one whale discovered a playful interaction with rudders and shared it with others, making it a current trend within that population of orcas.

While Shields does not dismiss the trauma response theory entirely, she highlights the challenge of confirming it without more direct evidence. She acknowledges the complex emotional capabilities of orcas. Still, she emphasizes that there is no documented evidence of revenge behaviour or direct aggression towards humans, despite opportunities for them to display such behaviour in the past.

Watch the encounter below:

 

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