Why Do These Whales Keep Rubbing Themselves on the Same Beaches?

​For humans, family tradition might mean getting drunk on a holiday long weekend. For some whales, tradition could mean getting together for a nice family rub on the beach.

​An amateur video of a rare beach-rubbing behaviour in a pod of northern orca whales is providing a unique glimpse into one of the animals' most complex and poorly understood social rituals. Certain resident northern populations are the only orcas known to engage in beach rubbing, and genetically similar southern pods never go rubbing at all.

Many researchers believe that beach-rubbing is a prime example of genuine animal culture—the idea that sub-populations of species can form and maintain learned behaviours over generations. These northern populations seem to teach new calves to return to only certain very short stretches of beach for rubbing, and this preference persists for a whale's entire life.

Orca can live up to 90 years, so even after decades-long disturbances in their migration patterns, an orca matriarch can lead the way to an area's best old rubbing haunts.

University of British Columbia zoologist and Vancouver Aquarium whale researcher Lance Barrett-Lennard has gotten to see this unusual ritual many times over his career. He said it generally begins out at sea when a pod, or small group of pods, starts to vocalize, "loud enough you can hear them through the hull of your ship."

Rubbing pods then race toward their chosen beach at a very high speed. When they arrive, the whales empty their lungs to lose buoyancy, and drop to the seafloor, where they kick along the bottom for some time. As seen in the video, the whales often appear to take turns rubbing themselves, and once finished, swim away very slowly. "By the time they're ready to leave a beach, the excitement's over," Barrett-Lennard said.

This is unusual behaviour for most orcas—sometimes referred to as killer whales—which are normally very cautious about approaching shallow water. However, rubbing beaches tend to have steep slopes with loose rocks for easy wriggling back to safety. Careful, reliable beach selection ensures that there's only minimal risk to the behaviour, but that could actually be part of the fun.

"The danger [of beaching] may be part of what the whales enjoy," said Barrett-Lennard. "Shared risk is what gives these sorts of activities value, that's what we know in humans… Pushing [themselves] up onto a beach is inherently risky, and that may be part of the excitement." Similarly rare and isolated Patagonian pods engage in the much more dangerous practice of shallow water seal hunting, as seen in this video.

Experts don't think the rubbing serves much of a physical purpose for the whales, which shed their outer layer of skin at a very high rate, eliminating the need for much grooming. The whales may simply be enjoying the cold stone massage. But as implied by the idea of shared risk, rubbing may also play an important social role amongst tightly knit family groups.

In 2002, conservationists rescued an an orca calf named Springer that had been separated from her pod and released her back to her family. Though the pod initially rejected Springer, she followed for several days until the group stopped to rub at its usual stretch of British Columbia coastline. Springer tried to join in.

While rubbing didn't immediately earn Springer a place back in her old pod, it did seem to start a weeks-long process of acceptance. If whales do use rubbing to cement social bonds, it makes sense that Springer tried to participate.

Rubbing behaviour was apparently known to local Aboriginal tribes long before its re-discovery by science in the 1970s. Having missed the chance to see the behaviour form, culture advocates lack the final piece of evidence required to prove that beach rubbing isn't just an instinct.

For example, some simpler animals like sea turtles have been shown to use the alignment of the Earth's magnetic field to guide them on long journeys to specific locations. But whales have no such physiology—and there doesn't seem to be a great correlation between genetic similarity and beach selection, either.

That's where this video could end up being important. It shows an area of the BC coast that, likely due to loss of food sources, resident orca whales have largely avoided for more than 20 years. Now that the whales have begun to return, locals confirm that pods are reappearing at precisely the same rubbing beaches they used in the past. And the reliability of their beach preference means it is very likely those locals were witnessing some of the same individual whales, too.

Of course, it's far too easy to ascribe human meaning to such odd quirks of behaviour, from heedless enjoyment to full-on exhibitionism, but evidence is mounting that at their core, those kinds of characterizations might not be as far-fetched as previously thought.