Sponge-Wielding Dolphins Teach Their Daughters How to Use Tools

By Eliza Strickland | December 10, 2008 9:03 am

dolphin spongeCertain bottlenose dolphins off the coast of Western Australia have picked up an unusual trick, a new study reports: When they head off to forage for a meal, they first grab sponges and hold them in their beaks as they dive down to the seafloor. These dolphins dive to the bottom of deep channels and poke their sponge-covered beaks into the sandy ocean floor to flush out small fish that dwell there…. Foragers then drop their sponges, gobble up available fish and retrieve the implements for another sweep [Science News]. This complicated procedure is the first confirmed example of tool use by dolphins, researchers say.

Scientists had previously observed some dolphins in Australia’s Shark Bay carrying around sponges, but the purpose was unclear. The new study documents this unusual behavior, which only a subset of a larger dolphin population engages in, and also probes the remaining mysteries. Researchers still aren’t sure why most of the “spongers” are female, and they haven’t determined whether the behavior conveys a real evolutionary benefit, although they have hypotheses to explore on both points.

In the study, published in the journal PLoS ONE, lead researcher Janet Mann explains that while mothers show both their male and female calves how to use sponges, female calves are almost exclusively the only ones to apply this knowledge. “The daughters seem really keen to do it,” says Mann. “They try and try, whereas the sons don’t seem to think it’s a big deal and hang out at the surface waiting for their mothers to come back up” [New Scientist]. Mann speculates that this could be because sponging is a time-intensive and solitary occupation, with more work required per meal; she thinks it’s possible that male dolphins aren’t willing to give up the socializing that could give them access to fertile females.

Despite the isolation, Mann found that spongers give birth to calves at the same rate as non-spongers, suggesting that the work-intensive behavior doesn’t put the tool-using dolphins at a disadvantage. Spongers hunt only in underwater channels with sandy bottoms. Their foraging grounds are a few metres deeper than the sand flats where other dolphins hunt, meaning they spend more energy on feeding. “But ultimately they’re doing as well as others,” says Mann. Mann believes they may be exploiting an otherwise unused larder, as the density of females in channels is lower than out on the sand flats [New Scientist]. But even if the spongers are profiting from exploiting a forgotten niche in the ecosystem, researchers don’t think that gives them an evolutionary edge: If it did, all the other dolphins in Shark Bay would have caught on to the behavior by now, Mann says.

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Image: Ewa Krzyszczyk

CATEGORIZED UNDER: Living World, Mind & Brain
  • http://clubneko.net nick

    “If it did, all the other dolphins in Shark Bay would have caught on to the behavior by now, Mann says.”

    One only needs to take a quick glance back at the human race to see what utter poppycock this statement is.

    Smoking, doing drugs, racing motorcycles, BASE jumping, engaging in wars and invasions and the brutal suppression of entire populaces… these are not giving humans an evolutionary edge, yet you don’t see people flocking from those behaviors to become doctors and yoga swamis, who by all accounts live far more healthily than the aforementioned humans and have a definite evolutionary edge.

    In fact, I would have to say that, according to how the human race works, the fact that only a few dolphins are doing it makes it more likely that it gives an evolutionary edge – only the best and luckiest few survive to pass on their genes , why else would we say that all humans trace their genetics back to 7 common female ancestors from around the European/Asian/African realms (though I suspect that number will fluctuate with time, I doubt it’s going to suddenly become 700 or 7000).

    It’s known that all throughout histories, scientific breakthroughs came from single people or small groups, that there was always a sizable population that resisted them, thought they were stupid, whatever. I’m sure the friends of the people that left Africa stayed behind and thought them fools that would never be seen from again.

    So, anyway, just because one animals performs a smart behavior and other animals ignore it doesn’t signify that the smart behavior doesn’t have any advantage, it may just signify a fact we know: large populations of a given life form can be stupid, or maybe just too comfortable to want to change.

  • Bystander

    “Smoking, doing drugs, racing motorcycles, BASE jumping” ~ Do not make you less likely to reproduce any more or less than anyone else so those behaviors do not lack any ‘evolutionary edge’.

    “engaging in wars and invasions and the brutal suppression of entire populaces” ~ These on the other hand *may* indeed affect your reproductive success.

    ‘to become doctors and yoga swamis, who by all accounts live far more healthily than the aforementioned humans and have a definite evolutionary edge.” ~ While I’ll admit that an avid yoga practitioner may increase their life span and therefore the possibility of more reproductive years, doctors or any other ‘moral’ profession will not give you any ‘ evolutionary edge’.

    *offers you a bag* Here, this is for your bias.

  • Bystander

    btw… This article reminded me of the ‘fishing bird’ I read about years ago. Apparently, this crane had been loitering by a pond in a park watching people feed the fish with pieces of bread. So when the people went on their way, the crane swooped over the water and retrieved a piece of bread yet uneaten by the fish and returned to the shore. The bird then proceeded to repeatedly drop the bread in the water, wait for a fish to come nibble at it and it would eat it, then pick up and drop the bread again.

    Interesting story but unfortunately this is the only recorded incident of this kind that I’m aware of. I know it’s not an ‘animal uses tool’ story but how can you not be at least a little awed by the simple genius of that crane ;)

  • Mike

    Sorry to burst your bubble guys but “engaging in wars and invasions and the brutal suppression of entire populaces” does in fact give an evolutionary edge. By making war we cause a large amount of people to be killed and yet at the same time this same activity spurs an tremendous effort to be as creative as possible in creating what might be new weapons. This then translates into new tools and technology for the general advancement of mankind. I’m not saying that war is a good thing just that because it affects our creative efforts (thus new tools) it does have an evolutionary impact.

  • brenatevi

    “Their foraging grounds are a few metres deeper than the sand flats where other dolphins hunt, meaning they spend more energy on feeding. “But ultimately they’re doing as well as others,” says Mann. Mann believes they may be exploiting an otherwise unused larder, as the density of females in channels is lower than out on the sand flats [New Scientist]. But even if the spongers are profiting from exploiting a forgotten niche in the ecosystem, researchers don’t think that gives them an evolutionary edge:”

    I don’t think it gives them an edge but helps them compensate for a disadvantage, like a lot of tools do. A spear helped man compensate for not having claws and mass.

  • Mathme

    This may also be an example of gendered behavior and a possible hint that dolphins have not only a sense of sex but also a socially prescribed notion of gender. Surely male dolphins can see this behavior as well. Are they “choosing” not to emulate it? Is it “women’s work,” so to speak? It would certainly be one thing if all the dolphins were using tools, but since it’s not all, it’s only one sex, then it may suggest even further sophistication in understanding. Of course, genderbias and certain attitudes may not be considered sophisticated, but the gender schemata used by the dolphins to attach meaning to what appears to be a simple tool is pretty astounding.

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