Orca interactions with vessels have dramatically increased in frequency and intensity since 2020, capturing global attention. These incidents involve the marine mammals targeting the steering mechanisms of boats, sometimes leading to significant damage and vessel immobilization. Understanding the motivation behind these unusual encounters is urgently needed by mariners, researchers, and conservationists. This situation underscores the challenges of human-wildlife co-existence in increasingly busy marine environments.
Scope and Location of Recent Orca Interactions
These interactions are concentrated along the Iberian Peninsula, primarily occurring in the Strait of Gibraltar and extending north along the coasts of Portugal and Galicia in Spain. The events track the seasonal migration route of the Atlantic bluefin tuna, the main food source for the local orca population. Since the behavior first appeared in May 2020, researchers have documented over 670 interactions through 2023, with the frequency increasing each year.
The vessels most often involved are slow-moving, medium-sized sailboats, typically around 12 meters in length. The orcas’ actions are highly focused, mainly targeting the rudder and occasionally the keel of the vessel. Researchers prefer the term “interaction” over “attack,” as there is no evidence of aggressive intent or hunting behavior towards humans.
While the majority of encounters result in minor damage, approximately 20% lead to severe damage, and at least seven vessels have been sunk or rendered unsteerable. The specific population involved is the critically endangered Iberian subpopulation, consisting of fewer than 40 individuals. Only a small group of about 15 individuals, known as the “Gladis” group, are responsible for these interactions.
Leading Theories Behind the Behavior
The leading explanation for this unique behavior centers on social learning and cultural transmission within the population. This hypothesis suggests the behavior originated with a single adult female, nicknamed White Gladis, who may have had a traumatic encounter with a vessel, such as a collision or entanglement. This negative experience could have led her to target a boat’s rudder, and the behavior was subsequently imitated by other individuals. The behavior then spread through the pod, both vertically from adults to juveniles and horizontally among peers, becoming a socially transmitted custom. The sustained persistence of the behavior since 2020 supports the idea that it is now an established cultural element for this small group.
Another prominent theory suggests the interactions are a form of highly sophisticated play or exploration, especially among the juveniles. Orcas are known for their complex play behaviors involving manipulating objects, and the rudder may offer an irresistible target due to its movement and the mechanical feedback it provides when struck. The goal appears to be disabling or breaking the rudder, not causing harm to the crew or sinking the boat. The fact that this subpopulation has a reliable food source in the bluefin tuna may provide the animals with more free time to engage in such exploratory or recreational activities.
Guidelines for Mariners and Mitigation Efforts
Maritime authorities in Spain and Portugal have published specific recommendations to help mariners navigate the affected areas and respond to an interaction. The primary safety measure focuses on immobilization and remaining passive to discourage the animals’ interest. If an encounter begins, mariners are advised to immediately slow down, stop the engine, and drop the sails to halt forward motion.
If an encounter begins, mariners should follow several steps:
- Turn off the autopilot and leave the rudder free to track, moving away from the wheel.
- Keep noise to a minimum and avoid shouting, hitting, or throwing objects at the orcas.
- Contact the maritime authorities using the designated radio channels as soon as the interaction starts, providing their exact position and the number of orcas involved.
Authorities have implemented temporary regulatory measures, including setting up dynamic avoidance zones and occasionally restricting the movement of small vessels in high-risk areas. Real-time alert systems and “traffic light maps” are maintained by the Atlantic Orca Working Group (GTOA) to help sailors plan their routes based on recent sightings. Long-term strategies include promoting the use of reinforced or composite rudders to minimize vessel vulnerability and developing effective co-existence strategies that protect both the endangered orcas and human safety at sea.