Tool-using dolphins and living fossils

August 30, 2011 • 6:22 am

Well, here’s another putative example of “tool use” that people can debate, but this seems to qualify as the real thing—even given the various and conflicting definitions of animal tools (the one I like best involves carrying an object for future use). reports that, in Shark Bay in western Australia, bottlenose dolphins (Tursiops aduncus) have been seen surfacing with a conch shell in their mouths, which they shake.  This dislodges any small fish inside the shells, which are promptly nommed by the dolphins.  Further, the behavior may be spreading—an example of cultural evolution:

A dolphin “conching” (photo from

It’s not clear whether the dolphins actually herd the fish into the shells to trap them, simply carry empty shells to the surface to capture any fish that may be inside (but how do they know that the shells don’t have the conch inside, which can’t be eaten?), or, as some researchers suggest, set out the shells, open side down, as fish traps to be harvested later.

Shark Bay” may ring a bell with some of you.  It’s not only a World Heritage Site, a marine reserve harboring large numbers of dugongs and dolphins, but also one of the few places on earth where we can see groups of living organisms, cyanobacteria (formerly called “blue-green algae”), that form structures nearly identical to some of the earliest traces of life on earth.  These living bacteria form layers of biofilms that trap sediments which, over time, build up into dome-like structures called stromatolites.

You can see living stromatolites at only a few places on Earth, for they require special conditions, especially extremely salty water that precludes grazing animals who would quickly destroy the domes. Here are some stromatolites in Shark Bay:

Some fossil stromatolites, of undoubted biological origin, are 3.5 billion years old: the layers that they form are unmistakable, and absolutely similar to the layers of the modern, life-containing domes.  Here’s an ancient stromatolite.

Photo copyright 2006 b y Andrew Alden
The 3.5 bya date makes them 100 million years older than the earliest true fossils of individual microbes (remember, fossil stromtolites are traces of bacteria), fossils that I wrote about recently.
Like many biologists, I would dearly love to see stromatolites in situ in Shark Bay (and all the other cool biology stuff that’s there), but its location does not afford easy access:
I’m betting, though, that at least one reader has been there, and if you have, do leave a comment and a description.

21 thoughts on “Tool-using dolphins and living fossils

  1. The dolphins would surely know what is inside a large shell from the ‘bounce’ of the sound…? Hard to use tools without hands of some type, & nice to see the barriers we have tried to erect between us and out fellow animals being reduced. We are not so special.

  2. I think what you’re seeing here, Jerry, is audition outtakes for dolphins not savvy enough to get the part in ‘The Day of the Dolphin’. Sure shaking some conchs is dandy, but can they talk? Hrm?

  3. I have not been to Shark Bay, but author Bill Bryson has. He included a description in his book about Australia, In a Sunburned Country. Here is the link to his discussion of stromatolites and his trip to Shark Bay: (you can also get it by Googling “Bill Bryson In a Sunburned Country stromatolites”)

  4. Some fossil stromatolites, of undoubted biological origin, are 3.5 billion years old:

    Is that really true? The paper you linked to (I could only read the summary paragraphs) seems to say it presents evidence of biological origin in stromatolites that are 2.724 billion years old. I’ve been looking around for more info on earlier stromatolites, and mostly what I’m finding is that biological origin on the earliest ones (3.5 bya) is still dubious.

    1. I always thought Allwood et al results, that combine micro- and macrostructure information, was rather untouched by Brasier et al excellent critque. (But I’m no paleontolog, just a new student of astrobiology, so I don’t know the inside track on this one.)

      Also, it is from the same Strelley Pool Formation that the latter now found a good preservation volume in. As I understand it from the same series of ridges defining its location (see the figures in respective supplements).

      But the recent trace fossils are from the underlying sandstone, the stromatolites are from the silicified carbonate just on top of it. [How do geologists compare these stratigraphic logs anyway? It looks like an art!]

      1. Thanks for that link. Much of it is too technical for me, but it appears that evidence of biological origin in those early stromatolites is not as dubious as I first thought.

  5. “…man had always assumed that he was more intelligent than dolphins because he had achieved so much — the wheel, New York, wars and so on — whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man — for precisely the same reasons.”

    –Douglas Adams

  6. (but how do they know that the shells don’t have the conch inside, which can’t be eaten?)

    Apprarently you’ve never ordered scungilli in an Italian restaurant. If a dolphin can’t manage to eat a conch, that would be a property of the dolphin, not of the conch, which certainly is edible.

    Back on topic, I would not consider it tool use if the dolphin is merely peeking inside the shells ultrasonically and shaking the ones that have fish in them. That’s just smart hunting.

    On the other hand if the dolphin is in fact herding the fish into the shells in the first place, or setting out the shells as traps, then that would qualify as tool use in my book.

    1. I’d expect any dolphin problem with eating conchs would be getting them out of the shells in the first place. Shaking won’t do it…

  7. Obviously seeing stromatolites was on my bucket list, but I figured I had to visit my uncle in Australia to do so.

    However, on recommendation of some friends of our family, my whole family went to Exuma, an island in the Bahamasm during the summer a few years ago for scuba diving, snorkeling, and just general relaxing. We chose Exuma because it is relatively undiscovered as Caribbean islands go, so there are few hotels and lots of pristine beaches. It is also a short plane ride from Fort Lauderdale, Florida (just outside of Miami).

    When I was reading the materials in the hotel, I screamed out “They have stromatolites!” My parents and sister, who had never heard of them, thought there was something there that was going to kill us I was so loud. According to wikipedia, it is the only place in the world where they live in ordinary open ocean.

    There are two main parts of the Exuma, the main island where the hotels are, and across a bay a thinner island that is purposefully left undeveloped except for a small hut where they sell food. Most of the beaches are on the smaller island, and a water shuttle takes you directly from the hotel to the hut. The best beaches are on the bay side, since the ocean side of the smaller island is pretty much entirely lined with stromatolites, some as much 3 or 4 feet tall (some might as gotten as tall as 5 feet).

    When we got there the first time the tide was in so they were just under the water level. We were able to walk on them, they were pretty slimy and slippery so you had to be a little careful, unless you want to get wet (which didn’t end up being an issue since my dad picked my sister up and threw her in the water). It often required jumping to make it across particularly large gaps (although if you walked a bit further out or closer in you could avoid it, but what’s the fun in that?).

    They form a complex network of flat, irregular-shaped stromatolites with deep fissures between them. Some fissures are narrow, an inch or two, but can be as wide as a yard or more. Most fissures go all the way down to bare sand, although not all of them. They stretch from the beach out a good 100, maybe even 200 feet at places I would estimate, and we walked on them for a good half hour without reaching the end.

    We came back several other times with snorkel gear, and snorkeled between them. A lot of smaller fish live in the fissures and pools, and there are a number of small types of seaweed although those were fairly rare. The smallest fish lived in holes in the stromatolites, although I don’t know if these were natural or carved out by the fish themselves, while larger ones just lived in the pools or under overhangs. There were no real large fish, I assume that the twists and turns would make hunting pretty much impossible for anything larger than a couple inches long, and the strong currents caused by the waves passing through the fissures would probably bang them against the walls (although the walls were soft so that probably wouldn’t hurt too much). I saw a few species darting out to take a nibble on the walls of the stromatolites, but not many.

    Besides the stromatolites, they also have really nice beaches, a bunch of really nice coral reefs to scuba dive or snorkel on in the fairly sheltered bay, great food (including live conch), and the local Kaabovelik bear is my favorite bear in the world (although it tastes awful anywhere but the Bahamas).

    You hear so much about Shark Bay, it never occured to me that there could be stromatolites so close to home, not to mention so easily accessible. It was entirely luck that I happened to be there.

    University of Miami has a research facility there particularly to study the stromatolites (there were posts around that I gathered were being used to measure their growth). There is a lot of competition to get stationed there, although I don’t thinkthe stromatolites are the only reason 😉

      1. Alive or very newly dead. They have a whole bunch of live conch in a net. They pull one out, punch a hole in the back of the shell to break its hold on the shell, pull it out, chop it up into pieces, pour some vinegar and lemon juice on it, then give it to you. The whole process take maybe 30 seconds.

        Of course if that is not your thing that have cooked food, like conch fritter, conch burgers (basically conch fritter sandwiches), and various fish dishes.

        That is only on the small island, though, the main island has plenty of restaurants of various types (obviously seafood-focused, but it isn’t only seafood).

        I forgot to mention that a lot of celebrities own islands in the area, including Nicolas Cage, Eddie Murphy, and Johnny Depp. A bunch of scenes movies were also filmed there, including Thunderball and Pirates of the Caribbean.

        According to Wikipedia: “Modern stromatolites are only known to prosper in an open marine environment in the Exuma Cays in the Bahamas”

  8. I went to Shark Bay in 1984. It’s not all that far out of the way. It’s only a 7 hour drive on a coach from Perth. I went on a 3 day tour which overnighted at a road house near the turn off from the main highway to Shark Bay.

    There are two attractions there, the dolphins at Monkey Mia (I’m not certain if they still swim to the beach) and the stromatolites.

    I’m afraid that when I went I didn’t appreciate their significance, and I want to return.

    If you go, just make certain you don’t go in Summer. The UV radiation is severe.

  9. I just saw beautiful Pavilion Lake in British Columbia, Canada – the home of the very rare freshwater stromatolites! What a gorgeous place – and of great biological interest as well! (Apparently Pavilion Lake has the largest-known freshwater stromatolites.)

  10. There are also Stromatolites in Lake Thetis which is only a couple of hours north of Perth near the town Cervantes.. It’s a lovely little lake that you can walk around in a few minutes, yet some berk decided to plough a 4WD track around it just so people can circumnavigate it without getting out of their cars.. The region is also one of those biodiversity hotspots so not far up the highway are some awesome national parks..

  11. Been to Shark Bay, and (contrary to the very good advice above) in the summer, at 50 degrees C. The only advantage was that the stromatolites shimmered in the heat and made it feel like one was at the beginning of the world. But it was HOT.

  12. We are living in Singapore for a while and I insisted on a trip to Australia while we had the chance for a shorter flight. While Googling around for ideas owhere to visit I stumbled on the Hamelin Pool stromatolites, and that tipped the balance in favor of visiting Western Australia instead of Sydney. I new a bunch of microorganisms would probably be a bit boring for the rest of my family, but I couldn’t pass up such a unique opportunity. (I have an undergraduate degree in biology, and am an amateur enthusiast of evolution, so have encountered Hamelin pool frequently in books.)

    It’s a very lonely road approaching Shark Bay, but there were about ten cars visiting the stromatolites when we stopped there. There is a very nice wooden pier that allows you to walk out over the stromatolites and look at them up close. There are several signs posted along the way (featuring a friendly character Stumpy the Stromatolite) to explain the history and significance of the site. One sign points out tracks in the ground from a vehicle that were made 60? (not sure of number) years ago but have been undisturbed due to the efforts to keep the stromatolites undisturbed.

    Also nearby is an interesting site, Shell Beach, where the beach consists entirely of tiny cockle shells instead of sand. Monkey Mia was also fun, though we went in July so the winter weather kept us from seeing any other sea creatures besides the dolphins. The dolphins were very active and really do hunt and hang out right at the beach every morning.

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