Why orcas wear dead salmon as 'hats' remains a mystery, scientists say

In what may seem like a call-back to 1980s whale culture, a resident orca off the coast of Washington state was recently spotted sporting a dead salmon on its head. 

The phenomenon was first documented in 1987 when whales from three separate pods were seen wearing salmon on their heads, like a human wears a hat.

But scientists never understood why, and experts are still scratching their heads as they contemplate the most recent incident, documented in October. 

The director of the University of British Columbia's Marine Mammal Research Unit, Andrew Trites, said there's no obvious reason for the behaviour.

"Maybe it's to impress another member [of the pod]," he told CBC Radio West guest host Brady Strachan. "Maybe they just like the smell of dead fish."

But he and his colleagues suspect it's playfulness.

"It's probably being done by young animals and is probably something [that] others may catch on and do because they're very good at mimicking … in the same way that young kids can pick up tricks from others, sometimes to the disapproval of their parents."

Trites added that it wouldn't be to carry the food, because the salmon wouldn't be secure. Furthermore, orcas have other ways of carrying food — such as underneath their pectoral flipper.

The recent sighting was in Puget Sound, Wash., on Oct. 25. The person who saw it grabbed a photo and sent it to the Orca Network, a non-profit that tracks whale activity.

"Check out this photo of J27 Blackberry sporting a salmon hat, taken from Point No Point! May they continue to find lots of fish during their stay here in inland Puget Sound," reads a blurb accompanying the photo in the organization's recent newsletter. 

Howard Garrett, who co-founded Orca Network in 2001, said while the behaviour is a mystery, he believes it's a form of communication. Although he's not a marine biologist, Garrett has a degree in sociology and has been observing orcas since 1981.

"Orcas are the most socially bonded mammals known to science, they stay in their families and their extended families for life," he said.

"They're completely social, so this is some sort of social communication. And what it indicates is that they are using the fish as some kind of symbol. A symbol of what, I don't know."

Both Trites and Garrett say the behaviour could be related to the abundance of fish in the area.