‘Some of the orcas off North America’s west coast have taken to wearing dead salmon on their heads, resurrecting a curious trend that was first reported in the 1980s.

Local photographers noticed the salmon-wearing orcas last month – and so did researchers. Deborah Giles, science and research director for the non-profit organisation Wild Orca, was observing the marine mammals in South Puget Sound in south-west Washington a few weeks ago. “We saw one with a fish on its head,” she says. “So that was fun – it’s been a while since I’ve personally seen 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….’ (Colin Barras via New Scientist)