Patricia Brennan from Yale University is trying to encourage male Muscovy ducks to launch their ballistic penises into test tubes.
Normally, the duck keeps its penis inside-out within a sac in its body. When the time for mating arrives, the penis explodes outwards to a fully-erect 20cm, around a quarter of the animal’s total body length. The whole process takes just a third of a second and Brennan captures it all on high-speed camera. This isn’t just bizarre voyeurism. Duck penises are a wonderful example of the strange things that happen when sexual conflict shapes the evolution of animal bodies.
Childhood… violated… Innocence… lost… SCIENCE!Many ducks form bonds between males and females that last for a whole mating season. But rival males often violently force themselves onto females. To gain the edge in these conflicts, drakes have evolved large corkscrew phalluses, lined with ridges and backward-pointing spines, which allow them to deposit their sperm further into a female than their rivals. These extreme penises are even more unusual when you consider that 97% of bird species lack any penises whatsoever.
But female ducks have developed countermeasures. Their vaginas are equally long and twisting, lined with dead-end pockets and spirals that curve in the opposite direction. They are organic chastity belts, evolved to limit the effectiveness of the males’ lengthy genitals. Two years ago, Brennan showed that duck species whose males have the longest penises tend to have females with the most elaborate vaginas. Now, she has found further evidence that these complex genitals are the result of a long-lasting war of the sexes.
Duck penises (and those other birds) work in a different way to human ones. For a start, they are flexible when erect. Human penises stiffen thanks to an onrush of blood; for ducks, it’s lymph that does the job. Finally, human males get erections before having sex but drakes evert their penis directly into the female’s vagina.
That presents a problem. To really study the mechanics of a duck penis, you can’t just fluff the animal. You need to give it something to have sex with. That’s where the glass tubes come in. Brennan used four different shapes: a straight tube; a counterclockwise helix that matches the spiral of the male’s penis; a clockwise spiral going in the opposite direction; and a tube with a sharp 135 degree kink, that mimics the position of the first cul-de-sac pouch in the female’s vagina.
Brennan took these tubes to a commercial duck farm in California, where Muscovy drakes provide semen for artificial insemination. She watched as the handlers placed a female in the same cage as a randy drake, and waited until the male mounted her. Just as he was getting ready to mate, Brennan intercepted him with one of the four oiled tubes, touching it to a pair of sensitive spots that immediately trigger the explosive erection and ejaculation.
Her videos revealed the process of duck erection in painstaking detail, including how long it takes to evert the different parts of the penis, how fast the ejaculate is and how long it takes to retract the appendage (around 2 minutes). They showed that the drakes easily launched their penises into the straight tubes and the ones that matched the direction of their spiral. The tubes that spiralled in the wrong direction or bent at a sharp angle proved to be more challenging, and mostly stopped the males from achieving a full erection.
So 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. Clearly, it’s not size that matters, but what she lets you do with it that counts.
Reference: Brennan, P., Clark, C., & Prum, R. (2009). Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2009.2139
Update: Check out Carl Zimmer’s excellent take on this story
More on animal penises and sexual conflict:
- South African wildlife – Wait, that’s not a trunk…
- Traumatic insemination – male spider pierces female’s underside with needle-sharp penis
- Horrific beetle sex – why the most successful males have the spikiest penises
- Holy fellatio, Batman! Fruit bats use oral sex to prolong actual sex
- Male chimps trade meat for sex
- Frigid echidna sex – competition drives males to mate with hibernating females
December 22nd, 2009 at 10:43 pm
I imagine they make a noise like “sploink!”
December 22nd, 2009 at 10:53 pm
I’ll never look at Donald and Daisy the same again
December 23rd, 2009 at 5:45 am
Wow, this is what I call heart warming science. Please keep us updated.
December 23rd, 2009 at 7:31 am
Fascinating. That really is a brilliant illustration of an evolutionary arms race. I will have to make use of it somewhere.
“Evert” is now my word of the day.
December 23rd, 2009 at 8:58 am
It does help to explain why Donald has no pants, doesn’t it?
December 23rd, 2009 at 9:33 am
Now, why does that make me think of this story?
December 23rd, 2009 at 2:19 pm
I’m not quite sure; is this relevant?
December 23rd, 2009 at 3:04 pm
Excellent! And if it is not topologically fancy penises, then it is sperm motility enhancing foam! Meanwhile, humans pay for things like ExtenZe® and lubricants and get UTIs . . .
December 23rd, 2009 at 4:04 pm
This is Rule 34 material….
December 23rd, 2009 at 8:13 pm
You learn something new every day. I’ve been popping cloacas to sex ducks for years. Good thing I never tried it with a Muscovy. You’d think they warn incipient biologists about this–it’s all fun and games until someone loses an eye.
December 24th, 2009 at 11:49 am
@9 — Oh NOW you’ve done it. Soon they’ll be porn of Donald and Daffy with corkscrew penises.
December 28th, 2009 at 4:00 pm
Hey Ed, not sure if you know this already but your article was featured on Digg.
January 6th, 2010 at 4:36 am
And the worst part? They didn’t even bother to wear gloves.
To be perfectly honest, I don’t won’t to meet the type of person who is that okay with getting duck ejaculate on their person.
March 8th, 2010 at 9:09 am
“his isn’t just bizarre voyeurism.”
jajajaja
ke no dice!
haciendole un pajote al pato donald niño jajajajajajjaja
eso supèra cualquier tratado de Freud!!!
xDD :S
March 26th, 2010 at 6:53 pm
[...] Ballistic penises and corkscrew vaginas – the sexual battles of ducks [...]
May 25th, 2010 at 9:50 pm
I loved the Donald and Daisy comment. I’m glad you did this because for some reason when it comes to the penis and vaginas of animals there isn’t much information out there…so when a kid asks “what’s that huge tumor on the back of his [male chimpanzee] behind?” To which the mother answers, “I dunno”. Then to look it up and realize there’s nothing available. Knowledge is power and you just gave the world more power! Kudos – beautifully done.
June 7th, 2010 at 7:09 am
why the hell is the guy with the ruler not wearing gloves???
October 19th, 2010 at 2:00 am
This all sounds painful for the unwelcome drake.
November 19th, 2010 at 1:00 am
[...] with their 20cm penises… [...]
February 27th, 2011 at 4:15 am
[...] [3]: http://blogs.discovermagazine.com/notrocketscience/2009/12/22/ballistic-penises-and-corkscrew-vagina... [4]: http://feedads.g.doubleclick.net/~a/IrueYzLoXIiaQcupwVeRf4xyWvg/0/di [5]: [...]
March 10th, 2011 at 11:15 am
[...] DNA gets passed on to the next generation. Take for instance, the strategy of the Muscovy duck. Spiny penises have got nothing on this, uh, ballistic adaptation (NSFW). AKPC_IDS += "27331,"; Filed Under: Good Feed Blog, Newsroom Tagged With: androgen [...]
April 14th, 2011 at 5:43 am
[...] duck sex-related stories is an ongoing joke amongst such eminent science writers as Mark Henderson, Ed Yong (parental advisory warning for that post!!) and many others… So the quacking-timer setup had [...]
July 8th, 2011 at 8:58 pm
This is a wonderful post! It’s such an unusual subject, but what a great way to introduce crazy facts and important topics like evolution. We need more of this sort of thing!
July 22nd, 2011 at 4:20 pm
[...] 2. There are other forms of sperm competition than sheer numbers. In promiscuous fruit flies, males have evolved sperm that contain toxins that kill that of other males, often to the detriment of the mother’s health and life expectancy (sperm with frickin’ laser beams on their heads). Closer to home, humans also seem to genetically resemble chimpanzees and bonobos for semen coagulation or ‘mating plugs,’ which could slow any subsequent male’s sperm from traveling through the female reproductive tract (see Eric M. Johnson’s post on this). Finally, as Ryan and Jethá discuss, the shape of the human penis, in particular its rather large size – compared to other primates – and the mushroom shaped glans, makes it particularly effective at displacing semen left by other males from the vaginal tract. Yes, people have tested this (via Jesse Bering). All for science. You should see what they do with ducks. Unbelievable. (Ed Yong). [...]
August 25th, 2011 at 9:42 am
How can I add a hit counter to my blogger blog? Detailed instructions would be appreciated. I searched counter on google and i can get this html code but i dont know what to do with it. Thanks!.
August 29th, 2011 at 2:17 pm
How did the genes that code for a more twisty vagina increase their proportion in the population? Is it that females who can be choosier about their mates have more reproductive success?
December 16th, 2011 at 12:13 am
[...] Where the male bird has a penis. There are several examples of this, ducks are the best known (and for good reason), but other birds, such as ostriches, have them too. The structure is a little different. Instead [...]