Salmon hats are back in vogue: nearly 40 years later, orcas are displaying unusual behavior once again.

Oceans cover a vast portion of the Earth's surface and are home to an astonishing variety of species: many of these are well-studied, yet they continue to amaze scientists. One of the most intriguing species is the orca, as noted by IFLScience.

Anyone who follows fashion knows that certain trends can resurface after a long hiatus. Orcas, it seems, are also not immune to the whims of fashion: after a 37-year absence, these whales have been spotted once again with a dead salmon on their heads.

Orcas are incredibly intelligent and social animals, renowned for their playful demeanor and the transmission of specific cultural traditions. Some of these behaviors can be quite beneficial, while others can be destructive. For instance, for several years now, orcas have been known to attack boats in the Strait of Gibraltar and teach this behavior to their peers.

According to scientists, different populations often exhibit distinct dietary specializations, featuring numerous stable behavioral traditions linked to their divergent foraging practices. It is known that some populations can also develop unusual and temporary behavioral "fashion trends" that likely do not serve any obvious adaptive purpose.

One example of such "fashion trends" is a behavior observed in 1987, when orcas began carrying the carcasses of dead salmon on their noses. Over the next five to six weeks, this behavior spread, and by the end of that period, orcas from their own pod and two others were sporting "hats" made of dead salmon.

Later, scientists observed that this behavior ceased to be widespread and eventually disappeared altogether, except for a few instances the following summer. However, just recently, this fashion trend has returned. Researchers noted that orcas belonging to the J pod off the northwestern coast in Puget Sound were again seen with dead salmon on their noses in October.

Researchers point out that we still do not know why orcas behave this way. It is possible that some of them were around during the last phase of the salmon hat trend and are bringing it back now that salmon stocks are abundant.

However, some scientists believe that the whales use their heads as storage, keeping excess salmon caught during times of abundance for later feeding. Thus, the peculiar behavior of orcas may not be a trend at all, but rather a way of using their heads as a "lunch box."

Another intriguing cultural behavior of orcas has been observed in the Salish Sea, involving the pursuit of harbor porpoises, and sometimes their killing. According to Deborah Giles, Director of Research at Wild Orca, these cetaceans do not actually eat harbor porpoises but seem to play with them to the point of death.

Near the west coast of the United States, young orcas have been spotted playing with fishing gear, moving crab and shrimp traps, and wrapping themselves in lines, possibly as a form of play. However, scientists are still unable to pinpoint the exact reason for this behavior.