Duck penises and sexual selection

Duck penises are long and corkscrew-shaped.  This has been known for a while, but a new report in Proc. Roy. Soc. imputes the evolution of this bizarre structure — and the matching long oviduct in females — to sexual selection: specifically, sexual conflict.   The male’s apparatus twists clockwise, the female’s counterclockwise, and so she has some control over the act . . . .

Anyway read about this result at Carl Zimmer’s Loom and Ed Yong’s Not Exactly Rocket Science. BE SURE to watch the videos (not for the squeamish!). They involve duck farms, sexual frustration, and kinky artificial oviducts. This kind of story is made for science journalists.

You’ll never look at a duck the same way again.

Fig. 1.  The iconic image, reproduced endlessly.  Sad to think that this guy died just so his dangling member could be shown to the world.


Brenna, P. L. R., C. J. Clark and R. O. Prum.  2009.  “Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia,” Proc. Roy. Soc. London doi: 10.1098/rspb.2009.2139.  (You’ll need a site license for access.)


  1. Ed Yong
    Posted December 23, 2009 at 7:46 am | Permalink

    This kind of story is made for science journalists.

    It really, really is, isn’t it? “So, to study the influence of sexual conflict on morphology, you basically cock-blocked some ducks with glass tubes so that you could film their ballistic penises? Mind if I quote you…”

  2. newenglandbob
    Posted December 23, 2009 at 8:55 am | Permalink

    I read this over at and I think this is most bizarre. They fight mean and dirty!

    • newenglandbob
      Posted December 23, 2009 at 8:56 am | Permalink

      over at “The Loom”

  3. Jordan
    Posted December 23, 2009 at 8:56 am | Permalink

    Keep in mind that a loving Creator designed this perfect duck with a massive corkscrew cock. That’s just the kind of thing that God is into!


  4. Posted December 23, 2009 at 9:09 am | Permalink

    Must be a wood duck (drum roll).

  5. Barry
    Posted December 23, 2009 at 9:27 am | Permalink

    But – – but – – I thought evolution for flight would have selected for smaller and lighter.

    • Ed Yong
      Posted December 23, 2009 at 9:38 am | Permalink

      It’s small and light most of the time. It’s basically a big balloon that you pump lymph into. It’s stored inside-out inside the duck’s body.

      • Barry
        Posted December 23, 2009 at 5:51 pm | Permalink

        Well, creative power of natural selection aside, I think it’s obvious what happened to this dead duck. He sprang a woodie at ten thousand feet and crashed into the ice. There will be no increased reproductive advantage for him now.

  6. Posted December 23, 2009 at 10:27 am | Permalink

    And here I thought they had to get by with a tiny cloaca. Way to go, ducks (and swans)!

  7. Marlene Zuk
    Posted December 23, 2009 at 12:02 pm | Permalink

    This is great. I’ve long admired Patricia Brennan’s work — and btw, you left out the last letter of her name in your citation. She had a fantastic quote in an article by Carl Zimmer a while back, about how she wondered not just about the penis but about the female structure, since (to paraphrase what she said), “you have to have a garage to park the car.” To me the interesting part is how the female’s reproductive tract is similarly convoluted, making it much less likely that an attempted forced copulation will succeed in fertilizing the eggs.

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  1. […] Double hat tip for this one: PZ Myers at Pharyngula and Jerry Coyne at Why Evolution is True. […]

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