Juvenile orcas attacking sailing yachts could be imitating the behaviour of one individual adult orca named White Gladis, scientists believe. Orcas have now sunk three yachts off the Iberian coast in the past 18 months and have attacked over 100 other yachts in increasingly aggressive behaviour.

‘Our theory is that this orca, White Gladis, had an ‘adverse moment’, perhaps related to a fishing boat while hunting tuna. We think that this orca had an incident and that she is trying to stop all boats,’ biologist Monica Gonzalez told Yachting Monthly.

‘We think that the other orcas are juveniles and are copying her behaviour because she is an adult and they think that as an adult “we need to do this to survive”’, said Gonzalez, who works with CEMMA, the Spanish NGO group that coordinates the study of marine mammals and is part of the working group of the Groupo Trabajo Orca Atlantica (GTOA).

The group of orcas attacking yachts around the Iberian peninsula appears to number 13 juveniles and two adults – the other named Grey Gladis – out of a larger group of 39. ‘Gladis is not training the juveniles,’ said Gonzalez, and is not necessarily present at every attack. ‘This group is not always together. They don’t swim together every day, preferring smaller groups of 5-6 orcas.’

The orca interactions with boats appears to be linked to the migration of tuna exiting the Mediterranean through the Strait of Gibraltar and heading west and north around the Iberian Peninsula into the Bay of Biscay.

Photo: Getty Images

‘The behaviour of orcas varies wildly, sometimes it is a single orca that approaches or sometimes they come in a group. Sometimes it appears that adults are standing off and directing juveniles,’ said John Burbeck, orca project leader at the Cruising Association. ‘Sometimes the orcas come at the yacht with a violent blow and cause significant damage immediately. Sometimes a group of orcas come in and play with the boat for extended period of up to 90 minutes’

Although most encounters between orcas and yachts are harmless, scientists are struggling to explain the orcas’ increasingly aggressive behaviour. Orcas are intelligent, social creatures that can easily learn and reproduce behavioural patterns.

Data from the Cruising Association, which works alongside Spanish and Portuguese scientists at the GTOA, shows that the number of orca attacks on yachts has increased in the last few months. ‘In the first three months of this year, there has been a dramatic increase (16 incidents as opposed to 2 last year),’ said Burbeck. ‘In May, with 10 incidents reported, it has already exceeded the total for last year and it doesn’t look like it is going to let up. May has been very, very busy.’

In 2022, there were 132 interactions with orca, with 99 yachts damaged and two sinking, data from the CA showed. There were also 256 uneventful passages. Around 25% of the damaged yachts needed to be towed to port.

The latest yacht to be struck was on the night of May 4 when three orcas left the Swiss yacht without a rudder, causing the crew to abandon ship. The Spanish coast guard towed the yacht but it sank before reaching port.

The orcas specifically attack the rudders, bumping them, chewing them and breaking them off. The interactions last between 10-90 minutes and involve between 1-6 orcas. The interactions take place during the day and night, although are slightly more common at dawn and dusk.

The majority of the 2022-23 interactions are down near Gibraltar (69 interactions), with Galicia, northwest Spain, the next most common location (43).

‘Our advice at first is to avoid the orcas,’ said John Burbeck. ‘To avoid interactions, stay less than two miles off shore and navigate in less than 20 metres of water.’

The GTOA operates a traffic light information system on orca sightings. There are also two apps: GT Orca and Orcinus which give information. A Facebook page Orca Attack Reports gives information as does Orca Discussions on Telegram.

The CA this month launched an updated orca information portal. It is urging all sailors to report interactions and safe passages at the portal: www.theca.org.uk/orcas

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