A snake mimics a spider

If you like evolution and natural history, you should already be reading Ed Yong’s terrific site Not Exactly Rocket Science at National Geographic. In his short post “This snake has a tail that looks like a spider,” he describes a remarkable and newly found type of mimicry.

The snake is, appropriately, the spider-tailed viper (Pseudocerastes urarachnoides), first described formally only 7 years ago from Iran.  It was known since the sixties, but the one specimen’s tail was dismissed as a tumor or deformity. We now know from other specimens that this is indeed a species-specific trait. As Yong notes:

The tail is bizarre. If you saw a close-up photo of it, you’d struggle to believe that there was a snake at the other end. There’s a large orange or grey bulb at the tip, and the scales just before that are bizarrely long and thin. Together, these features look a bit like the legs and abdomen of a spider or their close relatives, the solpugids or ‘camel spiders’.

Spider_tailed_viper2

Credit: Omid Mozaffari

A close-up photo:

Spider_tailed_viper

Credit: Omid Mozaffari

This video shows the snake waving its tail, and the “appendages” of the mock spider look amazingly lifelike.

Now what is this bizarre appendage for? Two possibilities come to mind: the mock spider could be used to scare off potential predators, or it could be used as a lure to attract prey. Given that this viper has a pronounced threat display (see Yong’s piece), the latter seems more likely.  And tests show that the “lure” hypothesis is probably correct:

And then there’s the tail. It’s probably a lure, like a fisherman’s fly. By resembling a tasty morsel, it draws potential prey into the snake’s striking range. Fathinia tested this idea by putting a chick into the same enclosure as his captive viper, which duly undulated its tail.

“It was very attractive and looked exactly like a spider moving rapidly,” Fathinia wrote. “After approximately half an hour, the chick went toward the tail and pecked the knob-like structure. The viper pulled the tail structure toward itself, struck and bit the chick in less than 0.5 seconds. The chick died after 1 hour.” A sparrow met the same fate.

Yong notes that “caudal lures” aren’t uncommon in snakes, but this one is extraordinarily elaborate. A more normal lure is present in the northern death adder from Australia (Acanthophis praelongus); it’s a wormlike tip of the tail that’s moved to attract prey while the rest of the snake remains absolutely still:

h/t: Ben

18 Comments

  1. Posted July 13, 2013 at 10:27 am | Permalink

    Not only is that tail mind-blowing, but that head is basically invisible. Anybody else notice the way the patterning continues across the eyes? It’s almost amazing that anybody ever spotted the snake in the first place, and hardly surprising that it took so long to do so.

    b&

    • Diane G.
      Posted July 13, 2013 at 11:01 am | Permalink

      Agree that the crypsis is superb, here. But I suspect this might be a yet another case of the animal being known to locals for some time, but just recently to biologists.

      Very cool mimicry in both snakes!

      (FWIW, “Death Adder” is a much better name than “Worm-tailed Adder” would have been. Too bad the first one isn’t “Viper of Doom” or something…)

      • Diana MacPherson
        Posted July 13, 2013 at 11:32 am | Permalink

        I really like the Death Adder’s mimicry – so fluid! It even has a “come over here” appeal to me as a human!

  2. Diana MacPherson
    Posted July 13, 2013 at 11:02 am | Permalink

    I’d be totally scared of the fake spider tail & not afraid of the snake at all! It go like this: ahhhh a spider!!!! :( ooooo a snake! :) Ahhh, it bit me!

    • Diane G.
      Posted July 13, 2013 at 11:06 am | Permalink

      I too have arachnophobia (which I try hard to overcome) but not ophidiophobia.

      (Which is interesting only because I believe there are some data showing these fears to be inborn to an extent. :) )

      • Mark Joseph
        Posted July 13, 2013 at 11:12 am | Permalink

        Hello Diane:

        Suggestion: “Spiders: Learning to Love Them,” by Lynne Kelly. She had arachnophobia to the point where she was becoming unable to function. She finally realized she needed to do something about it, and (of course) ended up as an arachnophile. The book was really interesting.

        But, I’m an arachnophile…

        • Diane G.
          Posted July 13, 2013 at 11:25 am | Permalink

          Thanks, Mark, sounds good. :)

          I’m actually a bit of both, now; -phobe & -phile. I love observing spiders and even have some tarantulas.

          But nothing seems to overcome that chest-tightening when one unexpectedly appears on the arm of the sofa, say. At least it’s fleeting. The feeling, I mean; but often the spider, too. :D

          • Diana MacPherson
            Posted July 13, 2013 at 11:29 am | Permalink

            I actually remember when I became scared of spiders. As a child I wasn’t afraid at all but my mother (who isn’t afraid of them) told me that they’d bite me when I was poking at one (I was about 3). These spiders were small so I don’t know why she thought they’d bite me. The idea of the fangs freaked me out & that’s what freaks me out about them – the fangs. You’d think it was the legs but that’s secondary to the fangs for me.

            I always picked up snakes & lizards and all sorts of bugs & never became afraid of those. I’m not as afraid as I used to be but if I saw a tarantula all of a sudden on my furniture I’d run out of the house shrieking without even thinking about it!

            • Mark Joseph
              Posted July 13, 2013 at 12:23 pm | Permalink

              Hi Diana:

              And you are the one who posted that marvelous meme about spiders the other day; for anyone who missed it, here it is again:
              http://cdn-usa.gagbay.com/2012/10/there_was_a_spider_i_panicked-164083.jpg

              Humorous story about the last line in your post. When just beginning my missionary career, I was studying French in Quebec. One day my neighbor, an attractive twenty-something, saw a spider in her apartment, and came running and shrieking outside, in only her underwear. Yes, I was a fundamentalist, and yes, I had been married for 8 years, and yes, I looked.

              • Diana MacPherson
                Posted July 13, 2013 at 12:25 pm | Permalink

                Ha ha!

              • Diane G.
                Posted July 13, 2013 at 1:18 pm | Permalink

                ” . . . the one who posted that marvelous meme about spiders the other day. . . ”

                Ha, ha, I did miss that. Thanks for reposting! :D

  3. Mark Joseph
    Posted July 13, 2013 at 11:17 am | Permalink

    This mimicry is *so* amazing.

    As is this: I clicked over to Not Exactly Rocket Science,” and in keeping with my arachnophilia, clicked on the post at http://phenomena.nationalgeographic.com/2013/07/08/spider-webs-reach-out-to-flying-insects-cool-but-so-what/ titled Spider Webs Reach Out To Flying Insects. Cool, But So What?” where I learned the following:

    “Bees and other flying insects frequently collide with microscopic mid-air particles like dust and small molecules. These strip electrons from their cuticles—their outer shells—leaving them with a positive electric charge. In this way, a flying bee can build up a voltage of up to 450 volts.”

    Oh. My. Galaxy. That is so cool, and yet another example of something about the natural world that was not discovered or explained by a creationist! (By the way, if you’re interested, the post goes on to talk about the importance of these electric charges).

    • marcoli666
      Posted July 13, 2013 at 12:54 pm | Permalink

      That is cool! So the web kind of reaches out toward the flying insect just before it collides with it.

      • Mark Joseph
        Posted July 13, 2013 at 2:14 pm | Permalink

        God: Ain’t this like a totally awesome thing that I built into creation?

        Insect: Sod off, big guy.

  4. jaxkayaker
    Posted July 13, 2013 at 4:27 pm | Permalink

    Pardon me for nitpicking, but this isn’t a new type of mimicry, as far as I can tell. It seems to be an example of aggressive mimicry, already known in the death adder also shown above, as well as in anglerfish and snapping turtles, which have a tongue which is wormlike in appearance and is wiggled to simulate the movement of a worm, by which the prey is lured close to the mouth for ease of capture and consumption.

    • Achrachno
      Posted July 13, 2013 at 9:24 pm | Permalink

      But this is quite a bit more elaborate than those examples at least. This borders in bizarre.

  5. Marta
    Posted July 13, 2013 at 7:21 pm | Permalink

    Zimmerman found Not Guilty.

    Here we go.

  6. Posted July 15, 2013 at 9:54 am | Permalink

    Reblogged this on Sarvodaya.


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