Kinkiness Beyond Kinky

By Carl Zimmer | December 22, 2009 7:55 pm

There comes a time in every science writer’s career when one must write about glass duck vaginas and explosive duck penises.

That time is now.

To err on the side of caution, I am stuffing the rest of this post below the fold. My tale is rich with deep scientific significance, resplendent with surprising insights into how evolution works, far beyond the banalities of “survival of the fittest,” off in a realm of life where sexual selection and sexual conflict work like a pair sculptors drunk on absinthe, transforming biology into forms unimaginable. But this story is also accompanied with video. High-definition, slow-motion duck sex video. And I would imagine that the sight of spiral-shaped penises inflating in less than a third of second might be considered in some quarters to be not exactly safe for work. It’s certainly not appropriate for ducklings.

So, if you’re ready, join me below the fold.

This story is actually a sequel. Back in 2007, I wrote in the New York Times about the work of Patricia Brennan, a post-doctoral researcher at Yale, and her colleagues on the weirdness of duck genitals. The full story is here. (Brennan also appeared in a Nature documentary, starting at about minute 38:35.)

In brief, Brennan wanted to understand why some ducks have such extravagant penises. Why are they cork-screw shaped? Why do they get so ridiculously long–some cases as long as the duck’s entire body? As Brennan dissected duck penises, she began to wonder what the female sexual anatomy looked like. If you have a car like this, she said, what kind of garage do you park it in?

Brennan discovered that female ducks have equally weird reproductive tracts (called oviducts). In many species, they are ornamented with lots of outpockets. And like duck penises, duck oviducts are corkscrew-shaped. But while male duck penises twist clockwise, the female oviduct twists counterclockwise.

Brennan speculated that all this bizarre anatomy is the result of a peculiar form of evolution known as sexual conflict. A strategy that allows females to reproduce the most offspring may not be so good for males, and vice versa. For example, male fruit flies inject their mates with lots of chemicals during sex, and those chemicals make her less receptive to other males, thereby boosting his chances of fathering her eggs. But those chemicals are harsh and will make female flies sick. Females, in turn, have evolved defenses against those chemicals, blunting their effects.

With many examples of sexual conflict in nature, Brennan wondered if sexual conflict between male and female ducks was giving rise to their weird genitals. Female ducks pair off with male partners for the breeding season, but they also get harrassed by other males, sometimes being forced to have sex (and sometimes dying from the attacks). A third of all duck matings are forced.

And yet only 3 percent of the ducklings that female ducks produce come from such forced matings. Brennan speculated that the female ducks can block forced copulations with their mismatched spirals. And they might also be controlling which drake got to fertilize their eggs by socking away the sperm of different mates in different pockets. And the extravagant penises of males might be the result of an evolution around those defenses.

As I reported in 2007, Brennan discovered a pattern that supported this hypothesis. Among 16 species of water fowl, species in which the males grew long phalluses also had females with more turns in their oviduct and more side pockets. The ducks were escalating an arms race, genital for genital.

But Brennan didn’t actually know how duck penises actually moved through the labirynthine oviduct, and how the oviduct’s shape might affect the drake’s delivery of sperm. So she traded calipers and rulers for high-speed video.

Brennan and her colleagues traveled to a California duck farm, where workers are expert at collecting sperm from drakes. The first step in the collection is to get a drake excited by putting a female duck in his cage. The drake climbs on top, and then the penis emerges. Before its emergence, a drake’s penis is usually completely hidden from view, tucked inside his body like an inside-out sock. Drakes unfurl their pensises differently than male mammals. In mammals, the penis becomes erect as blood flows into the spongy tissue. Ducks pump lymph fluid instead. And as the fluid enters the penis, it does not simply become engorged. It flips rightside-out.

Here’s how it happens, in slow motion. A Muscovy drake everts his penis in about a third of a second, at speeds of 1.6 meters per second.

Of course, drakes don’t mate with the air. Having made this video, Brennan still needed a way to see how a duck penis actually performs its appointed task. Unable to film duck penises in a real female oviduct, she built a fake oviduct out of silcone. She then managed to get a drake to mate with it. But the overwhelming force of the explosive penis broke the fake oviduct.

So Brennan turned to glass. Her new fake oviducts were strong enough to handle the drakes, and she started filming. Here’s what she saw.

As Brennan had predicted, the counterclockwise turns of an oviduct slow down the expansion of the duck penis, compared to a straight tube or a clockwise one. Brennan suspects that female ducks slow down males trying to force a mating, but they can also let their partner’s penis move faster through the oviduct. They have been observed to relax and contract their muscles arond the oviduct.

Female ducks can’t stop an unwanted male from delivering his sperm, but the obstacles in their oviducts may give them control over what happens to that sperm. The female ducks may use their oviducts to slow down the expanation of the penis, so that by the time the drake ejaculates, the sperm are delivered in the lower reaches of the oviduct. A female ducks’s partner, with her cooperation, can deliver sperm further up the oviduct. With the wanted and unwanted sperm delivered to different places in the oviduct, a female duck may be able to store the sperm in different pockets. And then she can choose which drake will father her duckling. For all the explosiveness male ducks may display, it’s the female ducks that get the final say.

[Postscript: I tell Brennan's story in more detail in my new book, The Tangled Bank: An Introduction to Evolution. It opens the chapter on sex--where I show how the same processes that explain these strange genitalia explain many other things in the natural world.]

Reference: Patricia L. R. Brennan et al, “Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia,” Proceedings of the Royal Society of London, doi: 10.1098/rspb.2009.2139

[Update: 12/23--a couple misspellings fixed]

CATEGORIZED UNDER: Evolution, The Tangled Bank

Comments (88)

Links to this Post

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  1. Jeebus, whatever happened to the gentle cloacal kiss?

  2. Apparently there’s a lot more involved in duck sex than making a poultry effort.

  3. Jason

    When will the prolific duck rape make it on to Law and Order: SVU? It’s time to break the silence.

  4. HG

    The comments so far have been terribly unfunny.

    [CZ: Well, HG, I think you'll have to step up to the plate and post a joke of your own. Them's fighting words.]

  5. I think HG is just egging us on.

    We just bought a male duck for Christmas. I now think I’ll let GrrlScientist do the dissectiondressing. We might have to ask a female duck about stuffing, as they seem to be the experts.

  6. Jen

    Wow, those are amazing ovi-ducks.

  7. Boo

    My goodness, why aren’t those scientists wearing sanitary gloves? Ewwwwww.

  8. Well, as long as we’re on the subject of kinky duck sex, I seem to recall that there was an ignobel award given out a few years ago on the subject of necrophilia between male ducks.

    So, since I went there, it also seems like a good time to mention this recent story Bug powder causes male bedbugs to stab each other to death with their penises.

  9. Ermine

    Don’t get your feathers ruffled, HG!

  10. Morton & Co
  11. Morton & Co
  12. Jennifer

    There’s a bunch of ducks near my work, so every spring I get to watch several duck gang rapes. One time I did see the duck’s penis and OMG.

    I’m glad to hear the lady ducks have at least some defense against this crazy behavior…

  13. doug

    If nothing else, the use of those glass models prove that males will mate with basically anything.

  14. ra ra ra

    I have now seen things that can never be unseen. I did not know that there were clips of male duck genitalia out there, and I did not know how little I wanted to see it. Interesting!

    Merry christmas, folks and ducks.

  15. Alexander

    ‘So Brennan turned to glass. Her new fake oviducts were strong enough to handle the drakes, and she started filming. ‘

    A different meaning in a different context, eh?

  16. X

    So why isn’t the same thing happening with humans, or is it?

  17. reasonablehank

    No wonder Donald was so uptight. He was with the wrong lady all that time. I’d be angry too.

  18. Julia

    I just hope the person in these videos is a bona fide scientist, not a mere duck fluffer.

  19. nuada_oz

    So what does your daddy do?

    Oh he films drakes having erections!?!?

  20. Sean p

    #24 i think you might be on to something.

  21. Wow. People who think furries are freaky ought to check out real life.

  22. I hope you bought that duck dinner first.

  23. Total Duck pr0n! Do we know if these ducks were of age and this site was in compliance? On a serious note- this is fascinating. Was it Brennan who debunked the cyber myth about dolphins having prehensile penises? Good work Patricia. I look forward to further research.

  24. TC

    If you were any kind of a science writer you would use the proper latin plural of penis: penes. “Penises” might be as acceptable a variation the same as “ain’t” is for “isn’t,” but it is not correct. So, the next time any of you boys and girls see more than one penis, please, say PENES.

    CZ: Penises is perfectly acceptable. You can look it up in a dictionary. Or you can read the paper about which I’m writing. Let me quote: “The erect penises of mammals and turtles are stiff hydrostats supported by axial-orthogonal layers of inextensible collagen fibres.”

    Forgive me if I don’t retire early.

  25. Sam

    If he’s clockwise and she’s counterclockwise, it seems like while he’s screwing, she would be unscrewing and they would never get anywhere.

  26. marisano

    But why are drake penises curved at all? If they were straight, those males forcing sex would be at less of a disadvantage regardless of whether female genitalia curved clockwise or counterclockwise. [Does this imply that the two flip directions periodically?]

  27. David

    While TC was kind of an asshole about it, he does seem to be right about this rather pedantic issue.

    Here’s a quote from the dictionary.com page that you linked. “The proper plural is penes.” You have to scroll down to the heading “Word Origin and History.”

    It seems that “penises” is the dominant form in current usage, but this is a change from the latin origins and historical English spelling. The issue is that the word has passed out of the hands of the medical and scientific communities, and the general public has abandoned the Latin pluralization for the dominant English form. This development is relatively recent in historical linguistic terms.

    I’m sure that your editors know what’s best for their readership. It’s all just a piece in the ever-changing tapestry of modern language.

    Great article, btw.

    [CZ: Thanks, David, on the post. TC wasn't talking about a historical shift, but actually claiming that penises was the equivalent of ain't. But ain't is considered non-standard, while penises is perfectly acceptable according to several dictionaries and is used by scientists themselves in scholarly publications.]

  28. Ayse Saygin

    I hope that now people will stop suggesting rape is “natural” giving the duck example from “nature”, without considering the complexities of evolution and how it works within and across species.. Until humans develop twisty, penis biting vaginas, put rapists in jail please, where they belong. Thanks!

  29. Ziggy

    So, now we know why Walt always drew pants on Donald!

  30. Silus

    On the topic of ‘Penes’ versus “Penises”…
    The use of language is to communicate. Another example that comes to mind is that of ‘Octopus’. People often try to say ‘Octopi’ for the plural of Octopus, when the word originally came from Greek, not Latin. IIRC, the technically correct plural of it is ‘Octopetes’. If I actually used ‘Octopetes’ in a sentence, though, no one would have any idea what I really meant. In everyday English, we should just say ‘Octopuses’, because others will know what we’re talking about. While ‘Penes’ is technically correct, I find ‘Penises’ to be perfectly acceptable.

    On the subject of animal rape: It may be ‘natural’, but that does not make it right or good. Murder occurs ‘naturally’ among many species, but we won’t stop putting people in jail for that!

  31. Emily

    @Naked Bunny: I can see a whole new furry(or rather, feathery) sexual subculture emerging from this. (If it doesn’t exist already– not like I’d know.)

  32. yclept

    The pic of the strung up drake at the top of the article leads me to believe there will soon be a BDSM site for this, with some very creative and intricate CBT equipment devised.

    Seriously though…ducks, and their observers, have been around for ages; so why is this not already common knowledge?

  33. Blaise Pascal

    You learn something new every day. I thought “ain’t” was a contracted form of “am not”, the plural of penis was either penises or penes, and that the plural of octopus was either octopuses, octopodes, or octopi. I guess I was wrong on all counts.

  34. Steve

    Judging by the amount of academic “giggling” here, we haven’t been able to abandon our speciesism roots. Imagine what ducks would write about here. Would they consider their anatomy at all unusual? Would they be saying “ew, gross!”? Fact is, all life is mechanical -no less our own- and there are no morals. It all solves the desires of DNA using the tools at hand (carbon, hydrogen, oxygen mainly). We consider duck penises erotic because we compare them to ourselves. We don’t feel that way about bacteria reproducing; they’re too different. Regarding ducks having erections into glass tubes: is that any different from ourselves? We can be stimulated by a two dimensional image printed on a scrap of paper. We’re all animals; we all work the same way. The brain does the bidding of our genes, not vice versa.

  35. rrtzmd

    …damn, watching that gave me a cramp!

  36. Sounds like quack science to me.

  37. David Harmon

    You lead in with “To err on the side of caution, I am stuffing the rest of this post below the fold. ” Pity your webmaster didn’t agree, as that sentence appeared less than half-way down the height of a photo… which really could have used a fold. (In other words, “YIKES!“)

    Also, that’s a heckuva lot of lymph! Is there a reservoir or something?

  38. David Harmon

    Also Steve #51: “Imagine what ducks would write about here. ” They’d probably snicker at our inadequacy.

  39. Meowsing

    … Why would anyone take this as a “rape is natural, therefore good” idea?

    First, why wouldn’t it be explained by a culture? It’s actually really stupid to believe that other animals don’t have a culture merely because we can’t understand them and we’re too arrogant to learn the inflections of body language and scent.

    Second, this is a defense against rape, or forced sex, or whatever. The female ducks are evolving a defense against their attacker’s offspring, and they can/do encourage their willing partners. So… wouldn’t that be an argument for consensual sex, and against rape as a method of procreation?

    Does it make too much sense? I swear to god, I do not get people these days.

  40. fattpill

    This is the first time I have ever learned something and felt stupid for learning it. Was money really wasted to find this out and people are dying, starving, and plenty of actual wrong going on and here these people are studying duck dicks come on people. figure out how to make the government start using water as fuel.

    [Carl: As a civilization, I would hope we could chew gum and walk at the same time. That is, be able to support basic research on things like evolution while also figuring out new solutions for our energy demands.]

  41. Rick

    It will be interesting to see if this defense becomes their downfall. As Mallard ducks become the predominant species in most of Eastern Canada, this selective breeding defense is less desirable. Mallards now make up the majority of the duck biomass displacing many other species for food and nesting area.
    Could it be that Mallards do not have such similar genitalia??
    Forced mating frenzies are quite common with Mallards with several males taking their turn. It is often a wonder the females do not drown.

  42. Patricia

    This sheds a whole new light on the idea of “screwing”.

  43. SHAJI

    Think,every one has a creator.who make this amazing creations?the answer is only one -THE GOD- then turn to the creator that is only way to victory.for details see the last vedha QUR-AN.

  44. 24601

    @41 Ziggy… um, what? Mickey wore pants, Donald didn’t.

  45. Archwright

    Remember, folks, stuff like this happens all the time in nature. That’s why our ancestors invented walls.

  46. Zoe

    Hmm, maybe Todd Akin was actually talking to duck doctors before he made his ridiculous comments about ‘legitimate rape’.

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The Loom

A blog about life, past and future. Written by DISCOVER contributing editor and columnist Carl Zimmer.

About Carl Zimmer

Carl Zimmer writes about science regularly for The New York Times and magazines such as DISCOVER, which also hosts his blog, The LoomHe is the author of 12 books, the most recent of which is Science Ink: Tattoos of the Science Obsessed.

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