A group of orcas off the west coast of North America has brought back a bizarre fashion trend not seen since the late 1980s: wearing a single dead salmon on their heads as if it were a hat.
Experts are at a loss to explain why orcas would want to wear fish in the first place, let alone why they would want to bring back the practice almost 40 years after it stopped.
The salmon hat craze was first observed in 1987 when a female orca in the Puget Sound area of the northeast Pacific was seen carrying a solitary dead fish on her nose. Within a few weeks the behavior was picked up by members of other pods, suggesting something about it must have appealed.
Strangely, it would be a seasonal fashion. By 1988 the behavior was apparently passé, stopping as suddenly as it started.
Recent observations from photographers and researchers have confirmed it's happening again.
It's not clear if the whales are showing off, or storing food to eat later. Orcas have been known to store pieces of spare food under their pectoral fins, so this may be an adapted form of that behavior.
It's possible there's some significance to the hats within the communities the orcas live in. It could simply be as it seems – whimsical absurdity that amuses the animals on some playful level.
Or it could just feel good. Humpback whales have previously been seen wearing hats of seaweed, which some have speculated is because they like the sensation. Considering orcas can live for up to 90 years, it could be that some of the same whales are involved (it's the same part of the ocean, and it's not been seen anywhere else). Maybe it was just time for a salmon hat revival.
"Honestly, your guess is as good as mine," Deborah Giles, the science and research director at the nonprofit Wild Orca, told Colin Barras at New Scientist.
However, while scientists may be stumped for an explanation right now, efforts are underway to find one. Plans are being made to use drones to monitor the behavior, and to try and figure out what the purpose of these hats are.
Orcas are smart animals, capable of communicating in different ways that facilitates cultural exchange across different regions. They also hunt in groups, devising intelligent hunting schemes to capture prey. Taken together, novel behaviors involving food might be expected to appear and spread from time to time.
Further observations just might reveal hidden details to this remarkable trend that make its functionality crystal clear.
"Over time, we may be able to gather enough information to show that, for instance, one carried a fish hat for 30 minutes or so, and then he ate it," Giles told New Scientist.