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Anti-Fouling Paint May Be Cause of Orca Attacks on Yachts

A fascinating article from Marine Industry UK has offered an interesting explanation for the increase in Orca attacks on yachts.

The attacks have made global headlines over the past three years as the whales have become increasingly brazen and methodical.

Most of the attacks have occurred near the Strait of Gibraltar off the coast of Portugal and Spain, but there are also reports globally describing similar attacks where Orcas have systematically rammed boats to inflict damage.

The rush by scientists to explain the uptick in assaults has proposed everything from Orcas becoming increasingly protective of their young, to echo sounders from ships frustrating the whales' ability to use their echolocation.

One of the first theories to gain traction in 2020 suggested the whales were being protective of injured members of their pod.

At the time, Alfredo López, a biology professor at the Coordinator for the Study of Marine Mammals (CEMMA), told Newsweek: "It's not revenge. They're just acting out as a precautionary measure, even if eventually damage is done." According to eyewitnesses, injured whales were visible in some groups and the remaining members of the pod were seemingly trying to keep vessels from getting closer.

Nevertheless, the problem has grown to such a level that Spain's Ministry of Transport has stepped in, banning sailing vessels under 49-feet between Cabo Prioriño Grande and Punta de Estaca de Bares where the majority of attacks have taken place.

"Interactions with killer whales have affected, above all, medium-sized sailboats, with a length equal to or less than 15 meters (49 feet)," the ministry said in a statement. "All the encounters with the killer whales took place between 2 and 8 nautical miles from the coast and the sailing speed ranged between 5 and 9 knots, either exclusively under sail or sail and motor."

In an interview with The Guardian, sailor Victoria Morris described one such attack where nine Orcas surrounded her 46-foot boat off Cape Trafalgar in Spain and rammed it continuously for an entire hour.

"The noise was really scary," Morris said. "They were ramming the keel, there was this horrible echo, I thought they could capsize the boat. And this deafening noise as they communicated, whistling to each other. It was so loud that we had to shout."

Since 2020, there have been over 100 'interactions' where boats have been spun around, pushed, rammed, or damaged. According to Marine Industry UK, initially scientists identified three culprits. By 2022, however, the number is up to 17 individual Orcas who have participated in the attacks.

Now, a new theory has emerged with statistical evidence to back it up.

Black anti-fouling paint, a common outer coating applied to ships and yachts to prevent or slow the growth of marine organisms on the hull, may be the culprit. The coating prevents discolouration, corrosion, and the attachment of barnacles.

According to John Burbeck and the Cruising Association, who are leading a taskforce to address the problem, after six months of collecting data they've discovered a high percentage of boats in the attacks have black anti-fouling paint on their hull. Sailors and yacht owners can also report occurrences on the Cruising Association to help with data collection. Those being attacked are also almost entirely sailboats, and all under 49-feet.

According to Burbeck, “There are a high percentage of boats that are attacked that have got black antifouling. A low percentage of boats with black antifouling are having trouble-free voyages. If, on trouble-free voyages, you’ve only got 25 per cent of boats with black antifouling, why on the attack side, have you got more than 50 per cent with black?”

Burbeck is quick to note that other factors may be at play and that the anti-fouling theory could be a red herring. However, the evidence suggests that midsize sailboats with black anti-fouling are becoming targets at a rate of 2:1 compared to light coloured hulls.

The hull colour trigger may also start what Burbeck and other scientists theorize is simply Orcas being Orcas. Given their high level of intelligence and the fact they can both learn from one another and pass knowledge down through generations, families of Orcas may simply be enjoying toying with slow-moving black painted sailboats.

“Some of the attacks come completely out of the blue. There’s a crash and the rudder’s broken. Other times it’s obvious that they’re playing with the boat, because they spin it round and push it, and are clearly having the time of their lives playing until eventually the rudder breaks off and they lose interest. Some boats have been pushed up to four knots. They’re clearly playing, and other times they come in like a bullet and smash it off. If they always did it one way, you could say ‘it’s because’. Sometimes it’s a single Orca, and sometimes it’s up to six,” says Burbeck.

However, as the data continues to accumulate, Burbeck and others are starting to understand more about the Orcas' motivation.

“The Orcas can have three motivations when they approach the boat (competition for speed, curiosity, and skill, for example) and when they stop the boat, we are reducing the motivations to two. That is the reason for stopping the ship. If we increase the speed, in addition to not reducing motivations, we are increasing a new one: increased activity, blood pressure, adrenaline and excitement. At this point, things can get dangerous."

In other words, minimizing the factors that seem to encourage an Orca attack might be the key. Avoiding black anti-fouling, traveling at higher speeds through known areas, and staying in shallow water may all help reduce interactions. This, in turn, will discourage the enjoyment Orcas are seemingly getting, which only leads to more attacks.

Burbeck summed it up nicely, stating: “A euphoric Orca after having beaten the ship in speed and stopped the ship with the broken rudder, will be drunk with victory, therefore increasing his feeling of power and consequently his danger."

For now, the best recourse is to travel in shallow water, less than two miles offshore, and to travel quickly and in groups.

“We’ll need to travel in groups, have a guide, stay in shallow water, and travel even faster, rather than ambling through as we always have done, where the wind and sun takes you. I wouldn’t do that now," said Burbeck.

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