Female ducks can thank evolution for avoiding becoming impregnated by undesirable but aggressive males endowed with large corkscrew-shaped penises: vaginas with clockwise spirals that thwart oppositely spiraled males. That's right, males are literally screwed.
The research on this evolutionary 'battle of the sexes' at the genitalia level were described 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."
The research builds upon a 2007 Yale study that first described the strange morphology of a duck's sexual organs. While most birds have no phalluses, ducks turn out to have relatively large, flexible penises—up to 20 centimeters—tucked inside their bodies. During sex, male ducks extend, or evert, their phalluses inside the female. Brennan and her Yale colleagues used high-speed video to document the erection of the duck penis for the first time and found the whole process takes less than half a second—an act the Yale team described as "explosive."
Such large phalluses are supposed to give males a reproductive advantage when there is much forced mating. However, the Yale team hypothesized that females could make copulation difficult for the males with their complex genitalia. And, they wondered, do the convoluted vaginas of some waterfowl help those females exclude forced copulation?
To test the hypothesis, Brennan and colleagues examined duck penis eversion in a set of glass tubes with different shapes. 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.
The anatomical evolutionary race to control reproduction is one of the more dramatic examples of sexual conflict in nature.
"Although we predict that sexual conflict should be ubiquitous, finding a system where the 'arms race' between the sexes is so dramatic is exceedingly rare. Ducks are providing us with an incredible opportunity to understand the evolutionary consequences of conflict," said Brennan.
Other authors on the paper are Christopher J. Clark and Richard O. Prum, both from Yale. The study was funded by Yale University.
Comments
Hank Campbell | 12/28/09 | 05:26 AM
Just imagine...
[You venture to the local park and suddenly you get the overwhelming urge to feed the ducks some of your Happy Meal (which by the way is PROHIBITED, but for all intensive purposes I will expand on this scenario). Joy illuminates from your children's face while they watch Donalds and Daffys swallow up your freedom fries.
One of your offspring points to a lonely brown duck and proclaims, "That duck is my most favoritest duck ever!"
"That's right Offspring, she's the most beautiful, innocent and humanitarian duck in all the world!"
You then proceed to ponder, "Oh glorious day, nothing can ruin you."
(or can it?...)
Suddenly, out of a bush from nowhere, there is an emergence of three green ducks. You notice that these ducks most definitely have their eyes set on your rug rat's beloved brown duck (well in reality, each duck probably has just one eye looking at the brown duck since ducks have eyes on the side of their heads thus lacking the frontal predatory vision). Being the stellar analyst you are, you recall observing the prevalence of enlarged squirrel testicles on the way to the pond, and then BAM! Two neurons connect and you remember that it's springtime and incidentally, those aren't just three male ducks, they're actually horny outlaw ducks up to no good!
Having just read the Yale study on ducks and also being a hater of evolution, you attempt to remedy the situation before it happens (just like in that minority movie starring Tom Cruise). Unfortunately, you loose your footing on unearthed squirrel nuts, thus rendering yourself useless.
While incapacitated, you and your impressionable loved ones watch in horror and agony (the same feeling we got when we saw Janet Jackon's nipple on TV) while two duck thugs hold down someone's daughter while the other duck thug has its way with her.
The lady duck says, "QUACK! QUACK!"
But to no avail, the fertilization process via multiple rare corkscrew bird penis has already taken place.
Because AFLAC insurance doesn't cover certain "procedures" our young brown duckling will now have to prematurely endure all the responsibilities a full grown hen has to. Not to mention how many more Happy Meals it's going to take to get your kids to stop crying (fast food is expensive in this economy, mind you). ]
Now you understand the horrible consequences of duck rape.
I personally have witnessed many duck rapes in the University of California Davis arboretum, and obviously I've suffered psychological problems as a result.
Furthermore, there might be some of you who are "pro duck rape" and your argument might be, "She had it coming with the way she waddled her tail like that." Well, first of all, you're sick! And secondly, I assure you that that argument won't hold up in a court of law.
So please, let's unite and stop the violence!
Thank you.