In 1987, a female orca near Puget Sound began wearing a dead salmon on her head. Other whales in her pod, along with two other pods, joined in on the fashion trend and also started wearing salmon hats. Fashion trends among cetaceans must be fleeting because no more salmon hats were observed by the following summer.
Last month, the curious behavior was observed again in Puget Sound, and scientists still have no explanation for it.
We still don't understand why the orcas – or killer whales – behave this way. "Honestly, your guess is as good as mine," says Giles. But that doesn't mean we will never find an explanation.
This trend seems to be specific to the west coast orcas, and given their long lifespan, it could have spread through the same whales that wore fish as hats decades earlier. "It does seem possible that some individuals that experienced [the behaviour the] first time around may have started it again," says Andrew Foote at the University of Oslo, Norway.
Drones now make it much easier to observe the whales than in 1987, so scientists will be able to gather more information about their behavior this time.
Orcas seem to enjoy a fun trend as much as humans. At least this fad doesn't involve disabling sailboats.
Previously: Idiot attempts to "body slam" endangered killer whale (video)