Effect Measure

Ducks and the shape of things to come

The natural home for influenza viruses is aquatic waterfowl, including ducks and geese (anseriformes). So I’ve read a fair amount about swabbing the claocae (rectums) of these animals as part of avian influenza surveillance. Recently it has been suggested that avian influenza is actually a sexually transmitted disease, so the question of anseriform sex is now on the agenda. It’s not just consensual sex. It turns out that male ducks and geese haven’t heard that rape (aka forced copulation) is frowned up in civilized society and, unusual among birds, they go in for it in a big way. Big in lots of ways. Because ducks seem to have prodigiously large penises. I was reading about a just published paper on duck penises and vaginas and decided to Google the subject and came upon a great post from scibling, Darren Naish at Tetropod Zoology:

Male ducks have large – often very, very large – penises. The text-book example is the Argentine lake duck Oxyura vittata, originally reported to have a 20-cm-long penis (this in a bird about 40 cm long in total), but later shown to sometimes have a penis that hangs for a length of 32.5 cm but stretches to 42.5 cm when fully unwound. The Argentine lake duck is a stifftail, a group of ducks that have been described as ‘promiscuous and boisterous in their sexual activity’. (“Duck humps dog, and other stories from the world of waterfowl sex,” Tetrapod Zoology)

Stifftail ducks, indeed. This is a great post from last July that also has an embedded YouTube video with the coy title, “duck fucking a golden retriever.”

If you are still in the half of those reading this who haven’t already clicked over to watch the dog getting ducked, there is still more to be said on the subject of duck penises, duck vaginas and forced copulation:

Female ducks have evolved an intriguing way to avoid becoming impregnated by undesirable but aggressive males endowed with large corkscrew-shaped penises: vaginas with clockwise spirals that thwart oppositely spiraled males.

More details of this evolutionary battle of the sexes fought at the level of genitalia are described by Yale researchers in the December 23 issue of the journal Proceedings of the Royal Society B.

“In species where forced copulation is common, males have evolved longer penises, but females have coevolved convoluted vaginas with dead-end cul-de-sacs and spirals in the opposite direction of the male penis,” said Patricia L.R. Brennan, lead author of the paper and postdoctoral researcher in the Yale Department of Ecology and Evolutionary Biology. “This coevolution results from conflict between the sexes over who is going to control fertilization.” (Eurekalert)

I learned that not only do some ducks have very long penises, but that they can be ready extremely quickly “when the time is right,” as they might say in the Cialis for Ducks commercial. In fact ducks can be ready even when the time isn’t right. If you are going to make a porn flick for ducks you need high speed video and the Yale researchers were prepared. Their money shot of a duck erection showed “explosive” penis extension in just a half second (doesn’t leave a lot of time for foreplay). Duck members aren’t just big but can corkscrew shaped. It turns out that duck vaginas can also have distinctive shapes. Brennan et al. wondered if this was one way female ducks might retain some control over reproduction even when there was forced copulation. To test this hypothesis, they did some experiments involving explosive duck penis eversions into glass tubes of various configurations:

A straight tube or a tube that spirals in the same counter-clockwise direction as the male penis doesn’t slow down the eversion process. But glass tubes that mimic the female vaginal shapes with a clockwise spiral or a sharp bend can completely stop the penis from everting. These results suggest females have evolved anatomical mechanisms to impede forced copulation, and provide new insights into the evolutionary consequences of sexual conflict over reproduction, say the scientists.

This is impressive science, but apparently the Yale researchers went to a lot of trouble without collecing any data about which influenza A strains the ducks were carrying. Which made me wonder: What’s the matter with these people? Don’t they know what the public is really interested in?


  1. #1 Coturnix
    December 27, 2009

    Ed Yong and Carl Zimmer had great blog posts about the latest research….including videos 😉

  2. #2 neil
    December 27, 2009

    Revere: Did you wake up today with your head in a weird place? 🙂

    Influenza A and Duck Penises..,

  3. #3 microdot
    December 28, 2009

    As former duck owners, we are still dealing with the trauma….

  4. #4 revere
    December 28, 2009

    microdot: LOL. Since you and Mrs. microdot are two of the least traumatized and most level headed people I know, maybe we should all raise ducks! As for me, the part of the post I was most proud of was the title.

  5. #5 anon
    December 28, 2009


    ducks and other wild birds (except gulls and geese) seem to be different
    in that there are fewer amino-acid mutations and the viruses evolve
    close to a bird-flu-index in the inner segments.

    So, what’s different in these birds from poultry or mammals ?
    Is it transmission through water or sex ?

  6. #6 Path Forward
    December 28, 2009

    Yes, you deserve to be proud of the title! But the part that had me laughing to the point of tears was:

    “What’s the matter with these people? Don’t they know what the public is really interested in?”

    A little too close for comfort, that!

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