Okay, here are a bunch of orcas (killer whales, Orcinus orca) rubbing their bellies on pebbles in very shallow water in Dog Bay, Canada. They come amazingly close to the observers (almost within nomming distance), and you can see how large their dorsal fins are. It’s amazing behavior:
Scientists. . . [say that] this “rubbing” doesn’t just happen anywhere. Carla Crossman, a research biologist at the Vancouver Aquarium, said this beach is not one where this behaviour is commonly seen. She said the orcas are very selective about the beaches they rub on and usually choose areas with smooth stones about an inch in size.
“We don’t know why they’re doing it, but they’re very picky,” she said, adding, “It’s very specific. This population of northern residents is one of the only populations in the world in which we see this behaviour.”
. . . The rubbing action is only seen in a few places between Vancouver and Alaska, and scientists aren’t sure of its purpose.
“It’s probably something social,” Crossman said. “Maybe kind of a ritualistic behaviour because they’re very specific in the beaches that they go to. They get really excited coming into these beaches. We see them kind of jumping up a little bit more, squealing, and making a lot of noise underwater.”
Though the rubbing looks like the orcas could be scratching their bodies, Crossman says that is unlikely. “If they were trying to shed off dead skin or maybe exfoliate their skin, we would expect to see it in other populations,” she said.
Actually, based on this scanty information, I still favor the exfoliation hypothesis: perhaps they’re trying to rub off parasites. After all, this is probably learned behavior, so the fact that it’s limited to one population doesn’t militate against the rubbing hypothesis any more than it favors the “social ritual” hypothesis.
Or maybe they just want a belly rub, and this is one of the few places they can get it.
Add your own hypotheses below
I saw this once in a David Attenborugh doc and the young males were rather excited so I’m going with sexual gratification.
Some of those whales had small, curved dorsal fins, so they’re either female or juvenile. But hey, sexual gratification is OK for females and young too. 🙂
(I’m a couple of days behind, I see this is well covered below)
Well, it’s nice to be independently confirmed.
😀
If it only happens in that geographic region, then maybe it has something to do with the water in that region?
Alternate theory: orcas are conservatives. Being too close to Canada makes them itchy. 🙂
Whether or not the behavior itself is learned, the locations of suitable beaches would need to be learned.
The ones with the really tall dorsal fins are the males. It looks like both males and females were doing it, but I cannot rule out sexual gratification. If it were just the males, then yeah.
My hypothesis is that it probably just feels good. That they are picky about choosing beaches composed of pebbles about an inch across seems to support that very well. It feels good to me to be massaged on my back with a well designed massager, not so good with a belt sander, and a cell phone on vibrate would probably be ineffectual.
“Feels good” is a reasonable proximal explanation, but it’s probably not the whole story. Sex feels good and food tastes good, but the immediate sensory experience is not the whole story behind those behaviors. There are deeper reasons why natural selection programmed us to perceive those sensations as good, and something similar may be going on here as well.
I’ll channel Larry Moran here and say maybe it’s a spandrel. Maybe the pleasure they feel when they rub on certain-sized stones was not selected for, but is an accidental by-product of selection for some other kind of adaptive behavior (such as sexual or social interactions).
Fair enough. But even so, “it feels good” is still just the beginning of the explanation, not the end of it.
Yes. Every attribute of an organism has some basis in its evolutionary history. Not every behavior that organisms have the evolved capacity to engage in has been selected for, or is a significant factor in their evolutionary history. I think it is a given that these animals have evolved a nervous system with the capacity to experience pleasure and pain induced by various sensory inputs including tactile sensation. That part of the story is already known fairly well. Given the complexity involved it is a sure thing that behaviors that are not evolutionarily significant will occur.
Specific to this article and the OPs question, the reasons given by Carla Crossman quoted in the article do not support the speculation that the behavior is ritualistic any better, less so I think, than that it feels good and or is fun for the animals. The speculations offered in the article are so general that they could apply to virtually any behavior of any animals that have some degree of sociality.
Re. sexual gratification, the males are also rubbing their sides apparent at about 3:00 in, and since the females are doing it too, not so sure – good hypothesis though. Exfoliation seems the most logical to me, or perhaps it’s a combination of sexual gratification and exfoliation.
Beluga whales (Delphinapterus leucas) congregate in certain areas during summer solely (?) to rub/shed. I’m uncertain how widespread this behavior is among cetaceans.
Smith, T.G., St. Aubin, D.J., and Hammil, M.O., Rubbing behaviour of belugas, Delphinapterus leucas, in a high arctic estuary. 1992. Can. J. Zool. 70:2405–2409.
Well, I’ve got a rug with knobbly tufts all over it and once in a while I like to take my socks off and rub my feet with it- it feels fantastic!
Comments 4 and 6 seem to be saying that if females are doing it, then it’s less likely to be for sexual gratification? I don’t understand why that would be the case.
I was wondering that, too…Male perception bias? 😀
A female whale would have a hard time with the rub, that is all. Protuberances help with that. I hope that is not male perception bias.
Do you have any idea how difficult it is to find out much about female whale reproductive anatomy with a quick Google search? (Especially compared to how easy it is to find pictures and descriptions of male whale organs?)
The closest I got to a description concerned blue whales: “The females have a long vulva with two nipples on each side to nourish newborns. They go in heat any time of the year, but the most common is during the migration to warmer waters for mating season.”
Nothing in that suggests to me that females wouldn’t enjoy a little ventral rubbing as well…
😀
Wait there’s a little diagram here that supports that possibility:
https://books.google.com/books?id=ASIVAAAAIAAJ&pg=PA94&lpg=PA94&dq=female+whale+reproductive+organs&source=bl&ots=g3p6z8PYxT&sig=HZ6Sst738fDSl-ho-9LrKR01w10&hl=en&sa=X&ei=lZXQVMexGIeogwT-xYIg&ved=0CCQQ6AEwAQ#v=onepage&q=female%20whale%20reproductive%20organs&f=false
Not that I’m favoring the sexual stimulation explanation for this behavior; only questioning why those who did thought that female participation weakened their hypothesis.
Yes, I agree that a good rub is not exclusive to males and I retract my previous assumption.
After doing the search, did you clear your browser history? Just kidding…but out of context, that could be strange 😉
Ooh, good point!
😀
Exfoliation was my first thought too, as bears have been described scratching their backs against trees.
I think that is scent-marking behavior.
Why didn’t any of them grab a two-legged snack?
They were *standing* in the water. Near *orcas*.
After a quick Google search, it seems wild orcas just do not nom Home Sapiens. Weird. Are we not tasty enough?
Probably not. We don’t have enough blubber. Much in the same way that most shark attacks are, I read, no more than a disagreeable taste test (for the shark).
Saying that, I personally wouldn’t put it to the test around these beasts.
😀
I’m going with “Feels good, man…” as my hypothesis.
That vid is just sooooo cool! I’d would so love to see this is real life.
I think it’s a combo of getting rid of stuff and feels good.
Also, just because we don’t see other whales doing it, doesn’t mean they don’t – they may do it underwater and it’s just that no-one’s seen them do it yet. There’s a huge amount we don’t know about what goes on in the oceans.
The rubbing/shedding hypothesis seems most plausible to me, I don’t really know. I do know that orcas are super-cool. If you were gonna cast a cetacean as Johnny in The Wild One, it would definitely be an orca. They are under-utilized as a sports mascot, as well.
My hypothesis is that those Canadians standing at the water’s edge have never watched videos like this one.