Orcas Have Fads. One Of Them Is Wrecking Boat Rudders

In the summer of 1987, a female killer whale in Puget Sound started doing something peculiar.

She swam around with a dead salmon balanced on her head.

There was no obvious advantage to wearing a fish as a hat. But within weeks, other orcas were doing it.

The behavior spread to whales in two neighboring pods.

Then, as quickly as the fashion appeared, it disappeared. By the following summer, the salmon hats were gone.

Orcas, it turns out, can have fads.

That history has become particularly interesting as scientists try to understand a much more expensive behavior spreading among a small group of killer whales off Spain and Portugal.

Since 2020, Iberian orcas have repeatedly approached sailboats and struck or pushed their rudders.

More than 700 encounters have occurred, and at least eight vessels have been lost, according to the Atlantic Orca Working Group.

The behavior has produced an irresistible explanation: revenge.

One widely repeated theory holds that an adult female was injured by a boat and began attacking vessels in response, eventually teaching younger whales to do the same.

It’s a compelling story.

But researchers studying the whales have no evidence that revenge motivates them.

A less dramatic possibility may fit the observations better.

The whales could be playing.

Why The Rudder?

A 2022 study published in Marine Mammal Science examined the interactions and found that the whales weren’t simply striking boats at random.

They showed particular interest in the rudder.

That distinction matters.

A sailboat’s rudder is a large movable object in the water. When the boat moves and someone steers, the rudder responds.

For an intelligent, curious animal, that creates something to manipulate.

Researchers also observed that the whales tended to lose interest when the vessel stopped moving.

That behavior doesn’t fit neatly with the idea of an animal determined to attack or sink a boat.

Instead, it suggests that movement itself may keep the whales interested.

The rudder moves.

The whale pushes it.

The rudder reacts.

For an animal capable of sophisticated social behavior and play, that interaction may be rewarding even if it serves no obvious purpose.

Unfortunately for sailors, an orca is an extremely powerful playmate.

Repeated contact can break a rudder or damage its steering system, leaving a vessel unable to maneuver. In severe cases, the damage can contribute to the boat’s loss.

The result can therefore be dangerous and expensive regardless of what the whale intends.

The Revenge Story Is Hard To Prove

The idea that orcas deliberately take revenge on boats has attracted widespread attention because it gives the behavior a familiar human motive.

But observing what an animal does is easier than explaining why.

Researchers can document which whales participate, what parts of the boats they touch, and how the animals respond when a vessel changes speed or direction.

Determining whether a whale is acting out of anger over a past event is considerably harder.

Scientists can see a behavior that has spread socially among a relatively small number of animals.

Only about 15 orcas have been involved, out of an Iberian population numbering fewer than 50.

That makes the earlier salmon-hat episode particularly useful as a comparison.

There was no apparent survival advantage to carrying dead salmon on the head. One whale started doing it, others copied her, and eventually they stopped.

In other words, not every behavior that spreads through an orca population needs to serve an obvious purpose.

Sometimes animals seem to do things because other animals do them.

And sometimes they may simply find an activity interesting.

What Sailors Are Told To Do

The play explanation also helps explain some of the advice given to sailors encountering the whales.

Spanish maritime authorities have advised boaters in affected situations to stop the vessel, lower the sails, and avoid holding the wheel.

Boats that remove the movement and resistance from the interaction have experienced less damage.

The logic is straightforward.

If the attraction is a moving rudder that responds when pushed, make it less interesting.

That doesn’t make an encounter with several killer whales harmless. A damaged rudder can create a serious problem at sea, and sailors in the area need to follow current maritime guidance.

But it changes what may be happening beneath the surface.

The whale may not see a sailboat and think “enemy.”

It may see something that moves when pushed.

The distinction is difficult to appreciate if you’re aboard the boat being pushed.

Still, understanding it matters.

Orcas are highly social animals that can learn behaviors from one another. Their communities can develop distinctive habits, and some behaviors can spread without an obvious connection to feeding, reproduction, or survival.

The salmon hats of 1987 demonstrated how strange those temporary traditions can look to humans.

The Iberian rudder interactions may be another example, although one with much greater consequences.

A dead salmon balanced on a whale’s head costs people nothing.

A broken sailboat rudder can cost thousands — or the boat itself.

But from the orca’s perspective, the difference may not matter much.

One object sits on your head.

The other moves when you push it.

And eventually, if history is any guide, the whales may simply decide that something else is more interesting.