Since May 2020, a baffling and dangerous behavioral trend has emerged among a subpopulation of orcas (Orcinus orca) off the Iberian Peninsula. These marine mammals, often referred to as ‘killer whales,’ have begun intentionally ramming and damaging the rudders of sailboats, primarily in the Strait of Gibraltar and along the coasts of Spain and Portugal. With over 700 recorded “interactions”—some resulting in the sinking of vessels—scientists are racing to understand the root cause of this novel phenomenon. The behavior, attributed to a small group of around 15 individuals collectively dubbed the ‘Gladis’ orcas, is a stark example of social learning, or ‘culture,’ spreading through an endangered, intelligent population, raising profound questions about the complex inner lives and social structures of these oceanic giants. This unprecedented situation challenges our understanding of cetacean cognition and underscores the need for new mitigation strategies to ensure both human safety and the conservation of this critically imperiled orca population.
The Highly Specific Mechanics of the ‘Gladis’ Interaction
The orca encounters, which have caused alarm among the international sailing community, are not random acts of aggression but rather highly focused and coordinated behaviors. Since the first reported incident, researchers from the Atlantic Orca Working Group (GTOA) have meticulously documented the pattern: the orcas target slow-moving, medium-sized sailboats, with the primary objective being the vessel’s rudder. They typically approach stealthily from the stern, often without the crew initially noticing their presence.
The physical contact involves a combination of ramming, nudging, and biting, almost always concentrated on the rudder. Orcas have been observed using their powerful heads to push against the rudder blade or their bodies to create a lever effect, resulting in the rudder’s rotation and, in many cases, its total destruction. This focused action—sometimes lasting over an hour—can compromise the vessel’s steering, cause flooding through the rudder stock, and ultimately lead to the boat’s sinking. However, experts note that the whales generally retreat and lose interest once the rudder is disabled, suggesting their intent is to stop or dismantle the steering mechanism rather than to deliberately harm the humans on board.
Theory A: A Spreading Cultural ‘Fad’ Among Bored Juveniles
One of the most compelling scientific explanations for the boat-ramming is that it is a form of social ‘fad’ or game, primarily initiated and propagated by juvenile orcas. Orcas are known to be incredibly curious and playful animals, and their societies possess a complex “culture” that supports the rapid spread of non-genetic behaviors. This theory suggests that the interaction originated from a simple, perhaps accidental, playful nudge that was found to be stimulating.
The recent increase in the population of their main food source, the Atlantic bluefin tuna, following years of scarcity, provides a possible environmental context. With an abundance of prey, young orcas may have more “leisure time” for playful and exploratory activities. The motion and resistance of a boat’s rudder, particularly those made of fiberglass, might provide a novel and exciting sensory experience, akin to a child playing with a new toy. An individual orca may have discovered the satisfying feedback loop of impacting the rudder until it breaks, and through the process of imitation and social learning—a hallmark of orca culture—the game spread horizontally among the young whales, becoming a widely adopted tradition within the pod.
Theory B: The Hypothesis of a Traumatic Trigger
An alternative, equally weighted hypothesis centers on a defensive response stemming from a prior traumatic event involving a vessel. This theory is often associated with a specific adult female, nicknamed “White Gladis,” who is believed to be the individual that first initiated the behavior. Researchers propose that White Gladis suffered a “critical moment of agony”—such as a painful collision with a boat, an entanglement in an illegal fishing net, or a severe injury from a propeller—that resulted in a lasting psychological and physical trauma.
In this context, the initial ramming was a learned defensive strategy: a reaction aimed at neutralizing the source of the trauma by stopping or disabling the vessel. Given the matriarchal structure of orca society, where post-menopausal females are crucial carriers of knowledge, this protective behavior would have been quickly adopted and taught. Her offspring and pod-mates would observe the perceived effectiveness of this action in preventing harm and integrate it into their collective behavioral repertoire. While this theory is difficult to prove, it offers a powerful narrative consistent with the high intelligence, long memory, and deep social bonds that define the killer whale species.
Culture and the Critical State of the Iberian Population
Regardless of whether the underlying motivation is play or trauma, the rapid transmission and perpetuation of boat-ramming highlights the undeniable existence of culture in orca society. The speed with which this behavior has spread among the small, critically endangered Iberian subpopulation—which numbers fewer than 40 individuals—demonstrates a remarkable capacity for social learning.
This pod, distinct from other orca populations, has had to adapt to significant human-related pressures, including heavy maritime traffic in the Strait of Gibraltar, intense noise pollution, and competition for tuna. The emergence of the ‘Gladis’ behavior adds another layer of complexity to their already precarious conservation status. Scientists are concerned that if the behavior continues or intensifies, it could lead to increased intervention from authorities or the public, potentially putting the whales at greater risk. The situation serves as a critical, real-time case study illustrating how human activity can inadvertently trigger or shape novel cultural behaviors in wild cetacean populations.
Conservation Strategies and Future Mitigation Efforts
In response to the hundreds of interactions recorded, conservationists, marine biologists, and maritime authorities are collaborating to develop strategies that ensure human safety while protecting the endangered orcas. Measures implemented include issuing real-time radio warnings to vessels about the orcas’ presence and briefly banning smaller sailing vessels from navigation in designated “hot zones.”
Furthermore, scientists are investigating practical, non-lethal deterrents. Suggestions include utilizing acoustic devices to gently discourage the whales, or altering the design of rudders to make them less appealing to the orcas—for instance, by changing the shape, texture, or composition of the material. Researchers strongly advocate against misinterpreting the incidents as intentional “attacks” or “revenge,” as such anthropomorphic language can lead to sensationalism and potentially justify harmful actions against the whales. The focus remains on understanding the behavior as a natural, albeit dangerous, manifestation of cetacean culture, curiosity, or trauma response, with the ultimate goal of finding a path to peaceful coexistence between the sailing community and the Iberian orcas.
