“If this doesn’t get him noticed, nothing will”: the marvels of sexual selection

Just when you think you’ve seen everything amazing that animals can do to attract a mate, you find something even more bizarre. This short video from BBC Earth shows a male pufferfish off Japan working tirelessly to build a stunning “sand castle” to attract females. Narrated by David Attenborough (of course), this video blew me away.

As National Geographic reports, the circles are two meters wide, take ten days to build, and, if one pleases a female, she lays her egg in the nest, and then the male fertilizes them and guards them till they hatch six days later. Then the male builds a new nest all over again. The discovery was made by Hiroshi Kawase et al. and published in 2013 in Nature Scientific Reports (reference and free link below).

A beautiful nest:

A male pufferfish (center) made this nest to lure females in Japan in 2012. Photograph courtesy Kimiaki Ito


Kawase, H., Y. Okata, and K. Ito.  2013. Role of huge geometric circular structures in the reproduction of a marine pufferfish, Nature Scientific Reports 3, Article number: 2106 (2013) doi:10.1038/srep02106


  1. Zach
    Posted April 15, 2017 at 3:22 pm | Permalink

    As a male member of Homo sapiens, I am thoroughly humbled.

  2. BJ
    Posted April 15, 2017 at 3:25 pm | Permalink

    Absolutely remarkable. It’s adorable how happy he looks while doing it at about 30 seconds into the video (I know I’m just anthropomorphizing here).


    1) He says the fish has to work 24 hours a day for a week, or the current will wash away all his work. Does this mean this fish can actually go without sleep for a full week? Is this a common thing for fish (I know almost nothing about fish except for what types I like when having sushi).

    2) He describes the building of this “castle” as “a plan of mathematical perfection.” My question — and I don’t know if anyone can truly answer this — is whether this fish (and other animals with complex mating rituals) actually are performing an at least rudimentary thought process while performing such rituals, or are they acting purely on instinct?

    • Posted April 15, 2017 at 3:29 pm | Permalink

      I can’t answer the first question, but no, the fish must be acting on instinct, but an instinct honed so finely by natural selection that the animal’s genes get it to produce this amazing and symmetrical structure.

      Plants, likewise, produce mathematically complex structures, like Fibonacci spirals, yet they have no mentation at all,

      • Posted April 15, 2017 at 4:57 pm | Permalink

        The nest in the photo has 30 virtually equally-spaced ridges. 30 has the factors 2 X 3 X 5, which might mean that the fish first divides the circle in half, then divides each half into thirds, then divides each third into fifths.

        That’s pretty amazing.

        • Posted April 15, 2017 at 5:11 pm | Permalink

          Oops! The one at the end of the video has 23 ridges, a prime number. So much for that hypothesis.

          • Mark Sturtevant
            Posted April 15, 2017 at 5:56 pm | Permalink

            Maybe they just keep going around, plowing their furrows over and over. Its gotta even out eventually.

      • BJ
        Posted April 16, 2017 at 9:48 am | Permalink

        Thanks very much for this reply, Jerry. Very helpful.

      • BJ
        Posted April 16, 2017 at 10:00 am | Permalink

        Jerry, after thinking over your answer, I’m afraid I need some clarification.

        You compare what the puffer fish has done to a some plants’ Fibonacci spirals. When you mention the latter, aren’t you talking about how they grow? By extension, aren’t you comparing the structure of the growth of such plants (via natural selection) to a physical activity actually performed by an animal (here, the puffer fish)? If this is the case, I fail to see what one has to do with the other, or, perhaps more aptly, how the example of the plants rules out or contradicts the idea of rudimentary thought process by the fish.

        Further, do we really know enough about the structure and capabilities of the puffer fish’s brain to rule out at least semi-conscious thought process?

        • BJ
          Posted April 16, 2017 at 10:06 am | Permalink

          I guess what I’m saying in my first paragraph is that growth is not an active physical activity (in the sense that one can or must think about it to do it), but rather a passive one that happens as a result of genetics. One cannot say, “I want to be tall” and grow up to be tall; they will be whatever height their genes (and environmental factors, if things such as malnourishment come into play) cause them to be.

          Carrying out active physical activity is completely different. It requires precise movements of the body and, possibly, thought process. I’m not denying that it’s possible the fish performs such complex physical activity over long periods by instinct, I’m just asking whether we can be sure that this is the case and rule out a thought process behind it.

        • Gregory Kusnick
          Posted April 16, 2017 at 1:53 pm | Permalink

          In what sense is growth not physical activity? It’s the result of coordinated action by an organism’s cells.

          I think what Jerry’s getting at is that the form of adult plants is generated by the expression of simple rules at a local level during growth. This nest-building might be similar in that the fish doesn’t necessarily have a picture of the resulting nest in mind, but just takes action locally to satisfy certain rules. Those local actions add up to produce the overall form of the nest, but not through any conscious planning on the part of the fish.

          • Posted April 16, 2017 at 3:10 pm | Permalink

            Yes, that’s what I meant, but you expressed it much better than I did!

          • BJ
            Posted April 16, 2017 at 3:30 pm | Permalink

            I think you and Jerry misunderstood my point, though I did try to make a clear distinction between what is essentially passive physical activity (growth) and active physical activity (building something). How does the fact that natural selection influences passive growth rule out the idea that the puffer fish is not, in fact, carrying out thought in its actions?

            • Gregory Kusnick
              Posted April 16, 2017 at 4:38 pm | Permalink

              It doesn’t rule it out. But it means you need evidence other than the complexity of the nest to differentiate conscious planning from local rule-following.

              • BJ
                Posted April 16, 2017 at 4:57 pm | Permalink

                I’m not sure we really can say for certain one way or the other, thus making the case one where both sides need evidence. My personal intuition is that it’s instinct, but I’m not sure and won’t act like I’m even 99% sure considering how little we know about how the fish’s brain works. I mean, we’ve been studying human brains nonstop for decades and still have very little understanding of how they function. Further, it wasn’t until the last couple of decades that we widely realized that animals like pigs or corvids carry out pretty high-level thought processes. I guess my point is that we shouldn’t be so sure we know what’s going on here. Though I really didn’t have an original point and was just hoping there was more information out there on such things than I personally knew.

            • Gregory Kusnick
              Posted April 16, 2017 at 4:40 pm | Permalink

              Also, growth is building something. It’s just that the building is being done by cells rather than by brains and muscles.

              • BJ
                Posted April 16, 2017 at 4:51 pm | Permalink

                I know, but we know cells don’t have brains, and therefore can’t be doing anything on a conscious level. We don’t have to question whether they’re thinking about it because there is no question to be asked. This is why I made the explicit delineation between passive physical action and active physical activity.

              • rickflick
                Posted April 16, 2017 at 6:57 pm | Permalink

                I think you are right to see growth and behavior as involving somewhat different mechanisms. However, it is growth which assembles the brain which determines the behavior. It is the way neurons are assembled during development that dictate that a bird will build a nest in a particular way out of particular materials and of a particular size. The idea that a bird or fish might “reflect” on her behavior while behaving is not totally ruled out, but it does not appear to be in any way required.

              • BJ
                Posted April 16, 2017 at 8:14 pm | Permalink

                I completely agree it’s neither ruled out nor required. I was really just hoping someone had some solid info on any of this, but I should have guessed that nobody did. Considering how little we know about our own brains after so much study, I don’t know why I thought there might be well-evinced answers.

              • Michael Waterhouse
                Posted April 17, 2017 at 11:07 pm | Permalink

                I think there is significant difference between the fishes actions and a plants growth.
                A growth is constrained by the mechanics of the material and the biological processes and it unfolds accordingly.
                The fish is a separate agent, acting on the environment, and making adjustments as the process unfolds.

                There must be some evaluation of the pattern in such a dynamic environment, some feedback and refinement, otherwise patterns would be often higgaldy piggadly.

                I don’t see that the same can’t be said of humans as well, just with much more detail and sophistication.

    • Posted April 15, 2017 at 3:54 pm | Permalink

      I’ve seen a few papers that attempt to address whether certain species of bird (usually corvids or parrots) actually have a rudimentary understanding of mathematical operations. There is some evidence that they can genuinely count and do simple algebra (like 3 = 1 + x). Obviously this requires high cognitive function though, something this little pufferfish lacks.

      Still, it is a stunning display, and a beautiful creation.

      • BJ
        Posted April 16, 2017 at 9:50 am | Permalink

        Oh, there’s no question that certain species of birds have thought processes, some of them perhaps even complex. Crows, grey parrots….

      • BJ
        Posted April 16, 2017 at 10:13 am | Permalink

        I remember seeing a video of a crow who would come to someone’s farm every day. One day, it showed up with porcupine quills stuck in its body. The family approached the crow and, amazingly, the crow allowed them to pull out each quill, wincing with each one.

        Now, that’s amazing in itself (knowing that the quills needed to be removed, he couldn’t do it himself, and he was willing to tolerate what might be another threatening animal to help him), but the truly remarkable event was what occurred over the next few months: every day, the crow would drop off rounded pieces of luminescent glass, gems, and rocks that looked like jewelry at the farm’s doorstep. It did this for weeks. It was giving them gifts (and had perhaps noticed they liked shiny things) for having helped him.

    • Heather Hastie
      Posted April 15, 2017 at 7:10 pm | Permalink

      I loved the look on his face at the beginning too – reminded me of a kid having a great time playing at the beach!

      This is so cool! The designs are absolutely remarkable and beautiful. I’m blown away by this too.

  3. John
    Posted April 15, 2017 at 3:33 pm | Permalink

    The effort we have to go through to get the goods.

    The expense of spirit in a waste of shame
    Is lust in action; and till action, lust
    Is perjured, murderous, bloody, full of blame,
    Savage, extreme, rude, cruel, not to trust,
    Enjoy’d no sooner but despised straight,
    Past reason hunted, and no sooner had
    Past reason hated, as a swallow’d bait
    On purpose laid to make the taker mad;
    Mad in pursuit and in possession so;
    Had, having, and in quest to have, extreme;
    A bliss in proof, and proved, a very woe;
    Before, a joy proposed; behind, a dream.
    All this the world well knows; yet none knows well
    To shun the heaven that leads men to this hell.

    Perhaps not the sonnet I was looking for, but appropriate enough.

    • BJ
      Posted April 16, 2017 at 9:50 am | Permalink

      The things a fish will do to get some, eh?

  4. Randy schenck
    Posted April 15, 2017 at 3:37 pm | Permalink

    The Michelangelo of the fish world.

  5. Mark Sturtevant
    Posted April 15, 2017 at 4:19 pm | Permalink

    Very much amazeballs. I remember seeing pictures of this mysterious pattern somewhere, without explanation.

  6. Ann German
    Posted April 15, 2017 at 4:20 pm | Permalink

    I couldn’t help but wonder if the constant action of using his fins to shape the sand was wearing down the fins . . . so often those reproductive rituals are inimical to survival.

  7. rickflick
    Posted April 15, 2017 at 4:47 pm | Permalink

    As a recreational diver, I wonder if I came across this pattern in the sand on a dive off Japan, what would I think it was? I’ve seen many times where simple circular depressions indicate the presence of some fish’s reproductive arena, but the elaboration seen here would have been a real challenge to my imagination.

  8. Oro Lee
    Posted April 15, 2017 at 5:12 pm | Permalink

    “Dunno – perhaps you should ask a pufferfish,” I shall reply if a theist asks where humans get their appreciation of art if not from god.

  9. Ken Kukec
    Posted April 15, 2017 at 5:53 pm | Permalink

    Brings to mind the Charles Atlas ads appearing in the comic books of my youth, in which a scrawny weakling would get sand kicked in his face at the beach, only to return later as a strongman facing down the bullies after embarking on the super-secret exercise program that a few bubblegum wrappers and a couple of bob sent to Mr. Atlas would fetch.

  10. aljones909
    Posted April 15, 2017 at 6:50 pm | Permalink

    I hope that little guy has some conscious appreciation of the wonder he’s constructed.

  11. Posted April 15, 2017 at 9:16 pm | Permalink

    Sorry to spoil the celebration, but nature’s greatest artist? I don’t think so.*

    While I love the video, such phrasing to my ears is old fashioned. In fact isn’t it unhelpful if one is trying to understand our own biological place within nature?

    *I haven’t watched the entire series so perhaps it is clarified how we fit into nature too.

  12. loren russell
    Posted April 16, 2017 at 12:04 am | Permalink

    Looks like the anal fin is used to hold a straight line..

  13. Gamall
    Posted April 16, 2017 at 6:09 am | Permalink

    Pretty, but structurally, aren’t wasp nests or anthills more impressive?

    Admittedly they are not strictly speaking the product of one individual…

  14. Andrea Kenner
    Posted April 16, 2017 at 7:54 am | Permalink

    Well, I’m impressed!

  15. Mike
    Posted April 20, 2017 at 9:15 am | Permalink

    Gobsmacked doesn’t even come close.!

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