Frog and snake: mimicry or not?

Julius Csotonyi, described by Wikipedia as a Canadian “paleoartist” (illustrator of ancient life) and a natural history illustrator, has done some fantastic artwork, including producing dinosaur images for Canadian coins. You can see a lot of his art at his website. But now Csotonyi may have detected a case of Batesian mimicry between a tree frog and a predatory snake (an emerald tree boa).

I’ll just show you his Facebook posts on the issue, which I have permission to put up. Julius sees a striking resemblance between the waxy monkey tree frog and a coiled emerald tree-boa, including the eyes, the folding of the skin, the color, and the white stripes.

The range overlap is some evidence for his thesis, though mimicry of a model can still have evolved when both now live in different places if the predator is migratory or if the mimicry is an evolutionary relic of a bigger range overlap that occurred long ago.  To me, the frog’s eyes, its posture, and the weird shape of the top of the head also resemble the snake.

I’m calling this a putative case of mimicry, but of course to be sure of this one would have to test it. For one thing, this is usually thought to work when the frog predator learns to avoid the snake through bitter experience, and then transfers that learning to avoiding the frog. If encounters of the frog predator with the snake were always fatal, no learning to avoid the snake appearance would be possible But predator avoidance could also be an innate response. That is, those frog-eaters who lived because they had genes that made them avoid approaching the snake because of its pattern,  and thus more likely to run away when they saw it, would be less likely to be eaten. That would produce an evolved rather than learned fear of things that look like this boa. Batesian mimicry need not always require a learned avoidance.

What do you think? Does this look like mimicry?  Put your answer below (we don’t know the truth, but herp people might take a guess). This may be the first case of Batesian mimicry involving an amphibian as the mimic and a snake as the model, but I’m not sure if other cases are already known.

As your reward for guessing, here’s another mimicry cartoon from SMBC (artist Zach Weinersmith) found by reader David.

Now what’s the erroneous assumption of this case of mimicry.?

47 Comments

  1. Posted December 19, 2017 at 11:12 am | Permalink

    I like the Moby Dick bug. 🙂

    • GBJames
      Posted December 19, 2017 at 12:08 pm | Permalink

      Indeed!

  2. ThyroidPlanet
    Posted December 19, 2017 at 11:31 am | Permalink

    Wow – that is a great observation

    That picture of the frog – is that a live frog? It almost looks cartoonish… did I miss something?

    Can there be gradations of mimicry – thus, strong or weak mimicry?

    And from certain angles? It appears that the mimicry is only apparent at certain viewing angles…

    Hoe interesting- but whaddoo I know…

    • ThyroidPlanet
      Posted December 19, 2017 at 11:32 am | Permalink

      How not hoe

  3. Posted December 19, 2017 at 11:32 am | Permalink

    I say yes…

  4. Gregory Kusnick
    Posted December 19, 2017 at 11:40 am | Permalink

    The relative scale of the head and the “coils” seems wrong. Maybe this means that the target is a juvenile snake, or that the putative predator typically encounters the frog from a perspective that magnifies the “coils” and reduces the head, or maybe the predator’s visual system just doesn’t discriminate such things as relative scale.

    For that matter, there are no scale cues in the photos to tell us how big the frog is compared to the snake.

    On a side note, I’m curious about how to parse “waxy monkey tree frog”. Are there tree frogs specific to waxy monkey trees? Is there a waxy monkey that this tree frog resembles (in addition to resembling a snake)?

    • Gregory Kusnick
      Posted December 19, 2017 at 12:59 pm | Permalink

      Well, it seems the juvenile snakes are orange, and turn green as adults, so there goes that idea. This does make the size and scale disparity more puzzling, though.

      If this is mimicry, the creature being fooled must be pretty easy to fool; sharp-eyed and sharp-witted predators would seem to be ruled out. So maybe the frog is the predator, and its prey is some insect that cohabitates with the snake.

    • Diana MacPherson
      Posted December 19, 2017 at 3:43 pm | Permalink

      I wondered (when I wasn’t thinking about how fat the frog was and how that made him feel) about the angle of predation as well – like how squirrels have white bellies because of hawks and looking flat from above.

      • Michael Fisher
        Posted December 19, 2017 at 5:04 pm | Permalink

        How does that work Diana? I don’t think a white belly will make squirrel appear flat from above.

        Supposedly land [& shallowish water] countershading of animals works this way: dark on top to make it harder for it to be seen from above against the usual dark background. White belly to blend into the lighter sky above when viewed from below. And there’s a flattening effect sideways on under illumination from above.

        • Diana MacPherson
          Posted December 19, 2017 at 5:47 pm | Permalink

          I think it’s called countershading. Dark on top and light on bottom means the place that gets the most light is darker and the part that receives the least light is lighter and this causes a flattening out that makes the animal less obvious.

          • Michael Fisher
            Posted December 19, 2017 at 5:57 pm | Permalink

            “…angle of predation […] like how squirrels have white bellies because of hawks and looking flat from above”

            I called it countershading in my comment & explained how I thought it worked. I still can’t see how white bellies makes a squirrel look flat from above – or is it I’m misunderstanding your wording in the quote above? Not that it matters much – we agree broadly 🙂

            • Diana MacPherson
              Posted December 19, 2017 at 6:10 pm | Permalink

              I don’t know how it works other than I saw pictures that explained it once and it seemed like it made sense.

      • BJ
        Posted December 19, 2017 at 9:57 pm | Permalink

        “…when I wasn’t thinking about how fat the frog was and how that made him feel…”

        He wouldn’t feel so bad if people would just stop mentioning it! This is why the waxy monkey tree frog community has such a serious problem with low self esteem.

        • Diana MacPherson
          Posted December 19, 2017 at 10:00 pm | Permalink

          🐸✨🐸✨

  5. Alpha Neil
    Posted December 19, 2017 at 11:42 am | Permalink

    Could it be a simple case of both adapting their camouflage to the same visual environment that results in a similar appearance? If both perch on branches in the day time and their surroundings are made up of green leaves interrupted by narrow views of sky you could end up favoring green with white linear features. I’m not dismissing the idea of mimicry in this case, just offering an alternative explanation.

    • ThyroidPlanet
      Posted December 19, 2017 at 11:48 am | Permalink

      Good point but I think there’s the predator-prey factor here ….

      Not that I know anything

    • Mark Sturtevant
      Posted December 19, 2017 at 3:30 pm | Permalink

      That is a good point.

  6. Posted December 19, 2017 at 11:44 am | Permalink

    Is there something to the book being “mimicked” in the comic being _Moby Dick_, specifically?

    • Gregory Kusnick
      Posted December 19, 2017 at 11:51 am | Permalink

      Presumably it’s being cited as an exemplar of the category of books that people think they ought to own but can’t be bothered to actually read.

      • Keith
        Posted December 19, 2017 at 12:14 pm | Permalink

        I wonder what species of insect is mimicking the Bible in millions of homes.
        Metaphoria Ludicrisa?

      • Posted December 19, 2017 at 12:34 pm | Permalink

        A wonderful book and a classic. But it does drag in places. I’ve put it down without finishing before. But then, as I’ve read it through a couple of times, that’s not such a big deal.

        • BJ
          Posted December 19, 2017 at 9:59 pm | Permalink

  7. Torbjörn Larsson
    Posted December 19, 2017 at 11:57 am | Permalink

    Possible frog/snake problems:
    – Narrow overlapping range means nothing fixes the adaptation, if it ever did.
    – Is there a size ratio requirement for Batesian mimicry? Frog becomes max 8 cm, snake max 180 cm; 20 times size ratio in developed, patterned adults.

    This looks more likely to be eager pattern recognition in the human meme host (to channel Dawkins), in my rather uninformed opinion. But as always, testing is needed.

    Possible bug/book problems:
    – No differential reproduction issue from touching, or at least it is a … whale … lot easier to evolve robustness against that. (Bug may evolve spikes instead.)
    – Moby Dick is a rather modern classic…

  8. Posted December 19, 2017 at 12:16 pm | Permalink

    I think the erroneous assumption in the cartoon is that evolution has an ultimate purpose (“so that humans will keep it safe…”). Or maybe it is the apparent absence of a model.

  9. nicky
    Posted December 19, 2017 at 12:57 pm | Permalink

    I fail to understand the first explanation, while the second one appears to make more sense to this tired brain.
    I think it probably is Batesian mimicry. Possibly in ‘early stages’ and not very impressive, but these things have to start somewhere. Even if it would deter/discourage only 1 in a 100 predator encounters, it still would be an adaptive advantage. [That is, of course, eminently testable].
    It makes me think of Cheetah cubs, which, with sparse white hairs on their backs, superficially look like ratels (honey badgers: real badass and feared animals*) from a distance. Not very impressive, but it still may give a small advantage.

    *[Don’t mess with a ratel, small as they are, you are very likely to com second best]

  10. John Scanlon
    Posted December 19, 2017 at 1:29 pm | Permalink

    I’d like to see it demonstrated that the features involved in the mimicry evolved as apomorphies in a localised part of phylogeny, not just that they occur together in a particular species. It seems that there are a lot of Phyllomedusa species, most are green with some white markings, and they all have big eyes, usually with prominently vertical pupils. The more vertical posture, white verticals, chest rolls and inflated glandular ridge behind the eye presumably evolved in a much later ancestor of P. sauvagii. Do we know its closest relatives?

  11. rickflick
    Posted December 19, 2017 at 1:39 pm | Permalink

    Almost as cute as a kitten!

  12. Mark Sturtevant
    Posted December 19, 2017 at 3:32 pm | Permalink

    It is certainly an interesting possibility. But why not the other way around? Frogs often have poison skin, so also possible the snake is mimicking the frog.

    • ThyroidPlanet
      Posted December 19, 2017 at 3:59 pm | Permalink

      Good point!

  13. Diana MacPherson
    Posted December 19, 2017 at 3:42 pm | Permalink

    I’m going to contribute to the science here the same way I did on Julius’s FB page:

    He’s just a fat frog that’s thinking about how fat he is and he doesn’t want anyone looking at his tubby little body, so you’re embarrassing him. Look at the expression on his face! It says “I hope no one sees how fat this outfit makes me look. Stupid stripes”.

    • Mark Sturtevant
      Posted December 19, 2017 at 4:16 pm | Permalink

      The vertical stripes make it look taller.

  14. infiniteimprobabilit
    Posted December 19, 2017 at 5:34 pm | Permalink

    Are those really teeth on that snake?

    I know it’s not poisonous but I’d hate to get chomped by it!

    cr

    • John Scanlon
      Posted December 20, 2017 at 1:11 am | Permalink

      Those aren’t teeth, but heat-sensing pits between the labial scales. They work like pinhole cameras in the infrared, like the single pair of pit organs on the face of pitvipers (e.g. rattlers, copperhead etc). Pythons also have rows of such pits on the lip scales, but they evolved convergently and are positioned within (not between) scale boundaries.

      These are the teeth: https://ssl.c.photoshelter.com/img-get/I0000tnSEn2CDz_Y/s/750/750/DB-0100.jpg

      • infiniteimprobabilit
        Posted December 20, 2017 at 1:40 am | Permalink

        Gosh. Those scales look exactly like a well-made set of dentures – ‘smile for the camera, Mr Boa’

        As for the real teeth, they’re no more reassuring 😉

        But thank you for a most informative reply.

        cr

  15. Michael Fisher
    Posted December 19, 2017 at 6:17 pm | Permalink

    The Cartoon: The premise is that in human eyes “Moby Dick” books [MDBs] are desirable to display & preserve, but not to read.

    But for the MDB-mimic to be treated like an MDB by readers & librarians it would have to be closer in appearance & lettering to a MDB rather than any other book which are all desirable.

    So it makes more sense to not resemble any sort of book! Books are attracting the attention this library moth doesn’t want – so there’s a bigger pay off [lower cost] to resemble a patch of painted wall, or other innocuous part of the scene, or have more young, or fly faster etc. etc.

  16. W.Benson
    Posted December 19, 2017 at 6:35 pm | Permalink

    “Extraordinary claims require extraordinary evidence.”

  17. Posted December 19, 2017 at 9:14 pm | Permalink

    For the cartoon, the wording implies that evolution has planning and foresight (I am assuming that, in this cartoon Universe, Moby Dick is a book that people like having around but don’t actually read).

    “it evolved … so that humans will keep it safe indoors and never touch it” implies it evolved with the goal of being kept safe indoors and never being touched. Wouldn’t it be better to say that insects left undisturbed on shelves have a better chance to reproduce which makes looking like Moby Dick advantageous.

    Of course, people usually have only one copy of Moby Dick, so I would expect this species to be sexually dimorphic. The other sex would perhaps look like The Ventriloquist’s Tale by Pauline Melville.

    • Posted December 19, 2017 at 9:17 pm | Permalink

      Or perhaps I’m overthinking it. The organism in the cartoon clearly has a spine so it must be a vertebrate.

      • Jonathan Wallace
        Posted December 20, 2017 at 6:46 am | Permalink

        Sea urchins have spines but they are not vertebrates 🙂

  18. Marcio Fleury
    Posted December 19, 2017 at 10:21 pm | Permalink

    The problem with the MBD insect is that it would not evolve instantly the MDB resemblance and the intermediary steps would not be possible, because a quasi-MDB insect would have no evolutionary advantage over a non-MDB insect.

    • Jonathan Wallace
      Posted December 20, 2017 at 7:16 am | Permalink

      You mean like “the eye could not have evolved because only a perfect eye with all of its components working together would confer any advantage on an animal so selection could not have fixed any intermediate stages between completely eyeless and perfectly sighted”?

      If the ancestral moth looked vaguely like Moby Dick books it might have only a slightly reduced chance of getting squashed by a librarian compared to conspecifics but that differential could have been enough to get the trait selected. Improved similarity to a book would then confer still more advantage as most books spend most of the time undisturbed on bookshelves even if they do not fall into the category of books everyone wants people to believe they have read even if they are too long, dull, difficult, demanding for them to have actually done so.

  19. Aaron
    Posted December 20, 2017 at 8:38 am | Permalink

    Is the erroneous assumption of the cartoon the absence of evolutionary constraints based on a species’ evolutionary history? For instance it would be extremely unlikely for humans to evolve “angel wings” at this point, even if the ability to fly would offer a huge selective advantage, because of how much reconfiguration of our anatomy that would require. Likewise, transforming a moth’s body plan into a book shape would seem to be an insurmountable task for natural selection.

  20. Noah Gordon
    Posted December 21, 2017 at 6:18 pm | Permalink

    Vertical pupils are common in nocturnal reptiles and amphibians and may provide an advantage while foraging. It’s also difficult to argue with what others here have noted: a green body with white bars is excellent camo in tropical forests. So without other evidence I’d have to side with convergence over mimicry


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