Orcas have sunk 3 boats in Europe and appear to be teaching others to do the same. But why?

‘Scientists think a traumatized orca initiated the assault on boats after a “critical moment of agony” and that the behavior is spreading among the population through social learning….’ (Live Science)

Related: Video: Orcas bite hole in boat off the Iberian coast

‘A group of orcas slammed into a sailing boat off the Iberian Coast, tearing a hole in the bottom of the ship. Orcas sank three boats earlier this year, among other attacks. CNN’s Christina Macfarlane reports….’  (CNN)