Understanding Orca Behaviour: A Deep Dive into Recent Incidents

Since 2020, a series of unusual events has captured global attention: orcas attacking and sinking boats off the Iberian Peninsula. What began as rare occurrences have evolved into a complex behavioural puzzle. This situation raises questions not only about orca cognition but also about their welfare and relationship with human activity.

On May 4, 2023, three orcas sank a yacht in the Strait of Gibraltar. Then, on September 13, 2025, another group sank a yacht near Lisbon, marking the fourth documented sinking. These incidents typically involve targeted attacks on boat rudders, especially of monohull yachts. They have become more frequent and exhibit clear signs of deliberate strategy and social learning.

What’s Behind the Behaviour?

Researchers have proposed two main hypotheses to explain these behaviours:

1. A Social Game

   Similar to how other orca populations have developed quirky, socially shared behaviours—such as wearing dead fish like hats or pushing marine mammals onto shorelines—this could be the latest in a long line of orca play. Juveniles often innovate, and behaviours, especially playful or exploratory ones, can spread rapidly through social learning.

   
   

2. A Stress Response

   Some researchers believe that these behaviours may stem from negative past experiences, such as boat collisions or fishing gear entanglement.

   
   

Nobody knows for sure why the orcas have suddenly started showing these behaviours. In my opinion, at Animal Welfare Expertise, they represent a form of play. A few original orcas may have discovered that they could easily break rudders, and this behaviour has continued.

Regardless of the origin, the pattern is striking. Orcas approach from behind, bite or ram into the rudder, and scrape the hull. This sometimes results in mechanical failure and, in a few cases, the boat sinking. These events reflect not just high intelligence but remarkable coordination, suggesting both intentionality and social communication.

Photo credit Andre Estevez

The Welfare Angle

The ramming of rudders and boats could seriously injure the animals. Unfortunately, humans can only prevent this by stopping all sailing boats from entering the region.

Moreover, the Iberian orca subpopulation is endangered. Their welfare is already compromised by several factors:

• Heavy boat traffic and underwater noise pollution

• Reduced prey availability, particularly bluefin tuna

• Potential negative impacts from tourist or fishing boat interactions

  
  

Addressing the Challenges

To effectively address these challenges, we must consider the welfare of orcas while ensuring human safety. This phenomenon underscores the cognitive complexity of orcas and the importance of interpreting behaviour through a welfare lens.

What Can Be Done to Protect the Orcas?

We need to develop coexistence strategies, including:

• Modified Boating Practices

Implementing modified boating practices in high-risk zones can help reduce interactions.

• Research into Behavioural Ecology

More research into the behavioural ecology of this subpopulation is essential. Understanding their behaviour will help us create effective protection measures.

• Prioritising Orca Welfare

Protection measures must prioritise orca welfare while ensuring human safety.

Photo Credit: Adam Ernster

How Can Tourists Safely Sail in the Region Again?

Ultimately, orcas are wild animals, and we cannot stop them from interacting with boats. However, there are some mitigation measures that might help. Some of these actions can be implemented now:

• Avoiding Known Orca Activity Areas or Times

Authorities and research groups have issued warnings for boating in certain zones at specific times (e.g., near the Strait of Gibraltar, Gulf of Cádiz). Use maps, apps, or local tracking data to know where orcas are known to be.

• Distance and Course Adjustments

Keeping a reasonable distance (2-3 km) away from orcas when detected is crucial. If you see orca pods, change course and move away. Despite mixed advice, it seems sensible not to reduce speed, as this allows the orcas to more easily ram the rudder or stern. However, avoid increasing speed or making erratic movements, as this could put the orcas at risk.

• Avoid Provoking the Orcas’ Curiosity

Minimising noise, engine revving, or other actions that might attract orcas’ curiosity is essential. Avoid confrontational responses, as banging hulls or using deterrents could escalate behaviour.

If these mitigation strategies do not work and orcas continue interfering with boats over the next few years, yachts may need to adopt:

• Reinforced Boat Design/Rudder Protection

Reinforcing rudders and using more robust materials or designs less susceptible to damage is advisable. Some sailboat owners are investigating stronger rudder stocks or protection shielding. Design changes to the stern or hull that offer less leverage or vulnerability to orca attacks may also be necessary.

• Early Warning Systems

Local authorities will likely need to establish systems that use a combination of social media reports, marine mammal observer networks, or apps to share sightings in real-time. If offshore controllers or authorities can alert sailors when orcas are nearby, sailors can take precautions.

Concluding Thoughts

While these interactions are likely a case of playful curiosity, they reveal much about orca intelligence and our evolving responsibilities in managing our impact on wild marine mammals. Researchers continue to investigate these behaviours. If it is indeed play behaviour, and therefore inherently reinforcing for the animals, it will likely not stop. We will need to modify our own behaviour if we want to continue sharing these waters safely with the orca!

Photo Credit: Dianne Maddox