Duck Sex: Competition between sexes leads to crazy anatomy

Eversion in air: from from Carl Zimmer on Vimeo.

That, ladies and gentlemen, is a duck penis. Science blogger Ed Yong has a great article up today about these freaky, corkscrew behemoths and the equally freaky, labyrinthine duck vaginas. A researcher from Yale has been studying both, and thinks these rather baroque naughty bits evolved in competition with one another, as female ducks tried to evade rape (or, rather, impregnation by a rapist) and male ducks tried to get around those barriers.

The shape of the female duck's vagina is a physical barrier that prevents the male from launching forth his ballistic penis to its fullest extent. It won't stop a drake from ejaculating (and those in Brennan's trials always did), but it does limit how far the semen is deposited along the vaginal tract. Not all males are hit equally hard by these defences. Those that the female actually wants to mate with have an easier time. If she's into a male, she strikes a pose that signals her receptiveness, keeping her body level and lifting her tail feathers high. She repeatedly contracts the walls of her genital tract, relaxing them for long enough for favoured suitors to achieve full penetration.

Males who try to force themselves upon her receive no such help and have to cope with vigorous struggling. The female may not be able to resist such advances, but her convoluted vagina gives her ultimate control over where the sperm of her current partner ends up. The fact that only 3% of duck offspring are born of forced matings suggests that females are indeed winning this battle of the sexes.

Not Exactly Rocket Science: Ballistic Penises and Corkscrew Vaginas (There's more video!)



  1. Duuuude. I have ducks. While I am glad their duck love in consensual, I am a little eeked out that there is a penis like that wandering around my property. Jesus Christ I had no idea that’s what was happening every morning. O_o

  2. Yeah, well… well… I’ve got a great personality!

    (Emasculated by a duck and it’s not even noon. Gonna be one of those days.)

  3. Jesus Christ, this means that somewhere out there on the internet is a video of a guy with a duck on his face doing something not just horrifying, but like something out of the most screwed up tentacle porn you’ve ever seen.

    I want to travel back in time and warn myself not to read boing boing today.

  4. I dunno…I just stuck my hand up a duck’s ass and pulled it’s guts out just three days ago, and *I* didn’t see anything like that. I guess I wasn’t looking hard enough. Wish I’d seen this post first..or glad I didn’t!

    Sure made me glad I’m a vegetarian, though :P

    1. Probably because it doesn’t really look like a penis when flacid. It lays flaccid inside the cloaca until the bird gets excited. It probably wouldn’t look like much.

      Ducks, geese, swans (Anatidae) and ostriches, kiwis and tinamous (Struthioniformes/ratites) all have penises. Weird, huh?

  5. Nothing says “Happy birthday, Jesus” like spouting duck penis!! And now I can mark “duck” on my animal penis bingo card. Thanks!

  6. And we all remember this thigh slapper: C.W. Moeliker, of Natuurmuseum Rotterdam, the Netherlands, for documenting the first scientifically recorded case of homosexual necrophilia in the mallard duck.
    [REFERENCE: “The First Case of Homosexual Necrophilia in the Mallard Anas platyrhynchos (Aves: Anatidae)” C.W. Moeliker, Deinsea, vol. 8, 2001, pp. 243-7.

  7. I’m not surprised by #15’s link. We have ducks, and they aren’t very picky about what they hump – female or male, or anything that looks like it might be a duck. Every once in a while a female will start mounting other ducks too.

  8. I had an brief affair with a lady duck years ago. At least I THOUGHT it was an affair. Turns out she was a pro. I didn’t realize it until we were finished, and she presented me with her bill.

    ba da bump!

  9. I’m just relieved the females appear to be winning this evolutionary arms race before the emergence of vagina dentata…

  10. barf just barf aaaack heave barf If a girl duck ever had to lay her eyes on that there would be NO ducks today.

    pornithology heheheHAHAHAHAHA

  11. I find it more interesting to consider the time frame required to achieve this morphology; that’s the product of a million years of rape. Good grief.

    1. I recommend not reading up on the phrase “traumatic insemination”. There are species out there that make this freaky duck stuff sound like a light romance.

  12. Where can I get a high-speed webcam with an artificial hand (with ruler!) mounted on the front? I’ve got some movies to shoot!

  13. Ha ha! That reminds me of a ‘rugby song’ I learned at my English boarding school:

    There was a young man whose name was Dick
    And he had, poor fellow, a corkscrew pri
    He spent his time in a lifelong hunt
    To find a girl with a spiral c

    He finished his search in far Glamorgan
    Where he found a girl with such an organ.
    But on their wedding night he dropped down dead,
    For he found the girl had a left hand thread!

  14. That is not how evolution works. The ducks may be “trying” something for whatever reason but it is not their so-called trying that causes evolution to occur. Natural selection and mutant genes of the OFFSPRING lead to evolution.

    Now when somebody shows me that there is causation between the desire of a parent wishing future offspring to have certain traits and those traits appearing in said offspring, I’ll gladly change my tune. It’s a day I have long been awaiting.

    Still… and until then:

    Both laymen AND scientists must quit attributing the desire of an ancestor that directly caused the apparent evolution to occur. Desire, schmire. God cares not about your prayers. He’s long gone. Desire, schmire. Nature takes care of its own: unequivocally and without mercy.

    recaptcha rebuttal: “be Enforced” :)

    1. No… but wouldn’t the theory of evolution favor those females that could choose their mates? And wouldn’t evolution then also favor those males that could thwart that choice? See the text on this blog entry on Selective Mating.

    1. A chaser not featuring a unicorn would be nice. I suspect a unicorn’s horn would just remind me of the horror.

  15. Where does he store that thing? Are duck genital orifices actually dimensional rifts to some screwed-up tentacle universe?

    1. @45 : oh, thank you for that. As if the video wasn’t enough.

      Hope it’s not sausage for lunch. Or pasta. Or…I don’t think I’ll have lunch, in fact.

      More seriously, this is an interesting question – that think must take a whole lot of space inside Daffy.

  16. You know how Daffy is always bouncing around? As if he had some sort of, you know, spring inside him?… Yeah.

  17. Bugs strained at the cords until the bedposts creaked, then sank exhausted. Face down, spreadeagled, tail in the air, he could not break free.

    If only he hadn’t taken that left turn…

    Behind him there was a quiet chuckle. Bugs craned his neck wildly, trying to see over his shoulder, only glimpsing a dark shape silhouetted by the light in the doorway.

    His dauntless nerve failed him. “Eh… What’s up…?”

    As he spoke, something uncoiled wildly from the figure’s crotch and curled about in the air like silly string before stiffening into a dripping, glistening tentacle, bumpy and screwy, squamous and rugose, knotted in places, pulsing in the light like the urge of an elder god made manifest. Bugs screamed, struggled uselessly as the figure approached…

    A gloating, lisping voice spoke close into Bug’s ear, spraying him with droplets of saliva, a hint of the horror that was about to unfold within him…

    “It’s rabbit season,” the voice said.

  18. Now I’m trying to decide if I’m going to name the band “Ballistic Penis” or “Convoluted Vagina”. Or are those just AOL passwords?

  19. Thx, #42. People say the dumbest things when talking about evolution. It had nothing to do with trying and everything to do with already having an adaptation that helps you succeed. To call it trying is to imagine the duck willing its penis or vagina into a new shape. One thing evolution hasn’t brought about is less stupid talk about evolution.

  20. If females are winning, why do drakes have these long schlongs? Apparently there is evolutionary benefit for having such a long apparatus.

  21. Strange explanation. There is no evolutional advantage for a female in avoiding rape – on the contrary: if her offspring are ‘rapist ducks’ themselves, their chances of procreation vastly increase.

  22. Actually the evolutionary objective for a female is to procreate with the mate of HER choosing.  You don’t want random babies just to have them, you want the fittest ones possible.  Thus the corkscrew vagina develops.  At least that’s my interpretation.

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