First, it was the salmon hats. Orcas in the Pacific Northwest (PNW) were observed placing dead fish on their heads—an odd, unexplained behavior. Then, across the Atlantic, in the waters off Spain and Portugal, another mystery emerged: orcas started attacking boats, specifically targeting their rudders.
At first glance, these two behaviors seem entirely unrelated. One looks like play, the other like aggression. But what if they’re both responses to the same underlying issue?
The Common Factor: Underwater Noise Pollution
Both the PNW and the Iberian coast have heavy maritime traffic. Low-frequency noise from ships disrupts orca communication and echolocation, forcing them to shout louder and expend more energy just to navigate and hunt.
A 2022 study linked rising orca stress hormones (cortisol) to vessel traffic—when ship noise increased, their stress levels rose; when noise decreased, so did their stress.
We know orcas are intelligent, adaptive problem-solvers. If increasing noise is causing them stress and interfering with their ability to function, they may be finding different ways to cope with or mitigate the disruption.
The Salmon Hats: Noise-Filtering in the Pacific Northwest?
Theories about the salmon hats range from social play to hunting rituals. But what if there’s a functional reason?
- Salmon tissue absorbs and scatters sound—especially low-frequency noise.
- By placing the fish over their melon (the organ responsible for echolocation), an orca may be experimenting with a natural noise filter.
- If ship noise is interfering with their echolocation, a salmon hat could act as a dampening shield, helping them focus their sonar signals.
This behavior might not be widespread because only certain pods are experimenting with this sensory modification technique.
The Boat Attacks: Disabling the Source of the Noise?
Meanwhile, across the ocean, the Iberian orcas aren’t wearing salmon hats—they’re ripping rudders off boats and swimming away with them.
This isn’t random. They specifically target the rudder, the very part of the boat that:
- Generates underwater vibrations, creating noise that could interfere with their echolocation.
- Controls the boat’s movement, meaning disabling it stops the vessel.
In numerous attack videos, an orca tears off the rudder and then swims away with it—not attacking the rest of the boat, not feeding, just removing the rudder.
If noise is a major stressor, this could be a learned, intentional strategy:
- They aren’t just striking boats randomly. They’re targeting the part of the vessel that generates the most disruptive vibrations.
- They’re not capsizing every boat—they’re removing rudders, effectively stopping the vessel from functioning.
This isn’t playful mischief—it looks like deliberate action.
Two Different Adaptations to the Same Problem?
In the PNW, orcas experiment with a possible noise-canceling solution (salmon hats).
In the Iberian Peninsula, orcas physically remove the source of disruptive noise (rudders).
Both behaviors emerge in regions with heavy ship traffic, both coincide with high-stress periods, and both involve sensory interactions with objects (a dead salmon in one case, a boat’s rudder in the other).
If the common factor is noise pollution, this would explain:
- Why the behaviors appear in different regions—orca populations develop unique cultural behaviors, but they face the same environmental stressor.
- Why the Iberian orcas aren’t wearing salmon hats—they’re dealing with noise in a different way.
- Why the rudder attacks are so specific—they’re targeting the primary source of wave-induced underwater sound on the boats.
Testable Predictions
If these behaviors are noise-related, we should see patterns:
- Do salmon-hat-wearing orcas frequent noisier waters more than others?
- Do rudder attacks correlate with higher ship traffic in the Iberian region?
- Does the removal of a rudder result in a noticeable reduction in underwater noise?
- Would quieter boats experience fewer attacks?
If so, the real question isn’t why orcas are doing this—it’s why we’re still ignoring the environmental stressor that could be causing it.
Maybe the orcas aren’t playing. Maybe they’re sending a message. And maybe it’s time we started listening.
