For the past four years, orcas have been ramming and sinking luxury yachts in European waters, puzzling scientists. Recent findings reveal that these destructive behaviors are not driven by aggression or territorial disputes but are, in fact, playful activities of juvenile orcas. The study, conducted by biologists, government officials, and marine industry representatives, highlights that young orcas are engaging in boat-bumping due to their inherent curiosity and playfulness, combined with ample free time.
The resurgence of the bluefin tuna population in the region, a primary food source for the critically endangered Iberian killer whales, has significantly reduced their foraging time. This abundance, partly attributed to climate change, means that the orcas no longer need to hunt continuously, providing them with more leisure time. This has led to the development of new ‘hobbies’ such as interacting with boats.
“In addition, climate change could be playing a role, leading to these tuna being in the Gulf of Cádiz continuously rather than seasonally,” the scientists noted. “This year-round abundance means that there appears to no longer be a need for the whales to pursue every fish encountered.”
Data collected from observations indicate that these interactions typically involve a few orcas from a core group of 15, mainly male juveniles and teens, known for their curious and exploratory nature. This behavior, which started as harmless head-bumping on boat rudders around 2017, has become more impactful as the orcas have grown larger. Interestingly, orcas over the age of 25, when males reach full maturity, have not been seen participating in these activities. Younger orcas likely mimic their older siblings’ playful behaviors, with some females observed in these interactions, possibly overseeing the younger ones.
Killer whales are known to exhibit playful behaviors that can sometimes lead to damage. In the southern resident killer whale population in Washington, USA, orcas have been observed playing with harbor porpoises to the point of killing them, which may reflect a similar escalation from less harmful interactions.
“Killer whales are known to play with other objects or animals in their environment to the point of damaging them (in the southern resident killer whale population of Washington, USA, which feed on salmon, individuals will ‘play’ with harbour porpoises to the point of killing them, which may be a similar escalation of an initially less harmful interaction), so this behaviour seems on that spectrum,” the scientists wrote.
These animals are also susceptible to trends, with new behaviors spreading quickly through a pod, akin to social media challenges. Historical instances, such as the ‘fish hat’ fad in 1987 where orcas carried dead salmon on their heads, exemplify this tendency.
“Different populations often have distinct dietary specialisations that are maintained by cultural transmission, and these ‘ecotypes’ typically have a variety of persistent behavioural traditions that are related to their divergent foraging,” the authors wrote. “Some populations may also develop unusual and temporary behavioural ‘fads’ and other idiosyncrasies that do not appear to serve any obvious adaptive purpose. Understanding the recent boat interactions by Iberian killer whales may benefit from an examination of such ephemeral traditions in other well-studied killer whale populations.”
The orca’s boat-bumping behavior is seen as a temporary trend that might fade over time, although it currently poses a significant concern for boat owners and authorities. The Atlantic Orca Working Group (GTOA) reports 673 interactions between orcas and watercraft since 2020, including four boat sinkings. One recent incident involved orcas repeatedly ramming a 49-ft yacht, leading to its sinking in the Strait of Gibraltar.
The Spanish maritime rescue agency has advised boat owners to avoid open waters and refrain from anchoring in high-risk zones. The study concludes that these interactions are not aggressive but rather playful, and terms like ‘attack’ are misleading and should be avoided. Understanding the orcas’ behavior as playful rather than aggressive can help better manage these interactions and mitigate risks to both vessels and the whales.
“In an ideal world, there would be a simple strategy for mariners to follow when killer whales interact, which would avoid vessel damage and harm to the whales. Unfortunately, there appears to be no such panacea,” the authors of the study wrote. “The singular agreement amongst the experts at this workshop is that the interactions between Iberian killer whales and vessels are not aggressive. The interactions have more elements consistent with fad behaviour or play/socialising than aggression. The use of such terms as ‘attack’ to describe these interactions is thus inappropriate, misleading and should cease.”
