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Duck Mating: The sex lives of ducks

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Rape is not typically something you associate with those darling “duckies” who bob along the surface of the water to the delight of children and adults at the local pond. It’s a shock to discover that male ducks are the rapists of the bird world. Often, a gang of three or four of them attacks a female duck, sometimes resulting in her injury or death.  While ducks are not the only species in the Animal Kingdom to display aggressive sexual behavior, they are the most aggressive of bird species.

What could possibly be the reason for such behavior?

Consenting adults

Female ducks are just as interested as the next species in selecting a particularly outstanding partner for fathering their offspring. However, when a female makes her choice and ducks pair up, one or several males get left out of the mating opportunity. Since male ducks don’t share in the raising of their young, their programming doesn’t include protecting the mother of their children -- they only stick around until the eggs are laid. Their real interest is in copulating with as many females as they can get their feathers on. Competition in the insemination war is ferocious and if you’re not partnered up, any female is fair game.

Why are ducks wired so differently from the 97 percent of bird species who have consensual sex?  The answer is that males, also known as drakes, are among the 3 percent of birds with a penis. Aquatic birds (according to one theory) may need penises to prevent their semen from being washed away.

When you think about it, if you’re a bird, not having a penis makes sense. With all that flying about, it would create drag and could easily get in harm’s way. For most birds, the superior design is the joining of the individual male and female holes known as the cloaca. Sperm passes from the male to the female during “the cloacal kiss.”

The need for cooperation of both parties to achieve this union has led to elaborate courtship rituals -- the call and response of bird attraction, moving the pair closer to the point of their mutual engagement.

Is size really important?

Ducks have enormous sex organs -- spiraling tentacles that can be as long as the drake itself. The Argentine lake duck’s phallus probably holds the record at 16 inches. If that isn’t bizarre enough, add the fact that in the fall, a drake’s genitalia will disappear, only to reappear next spring. Nobody knows why this happens.

The reason for huge penises is better understood. The classic explanation is that it allows males to have sex without the cooperation of the female. However, a deeper understanding is offered by Dr. Patricia Brennan, a female behavioral ecologist. Studying these oversized phalluses led her to ask a question that no one had asked before.

"So what does the female look like? Obviously you can't have something like that without some place to put it in. You need a garage to park the car."

Feminine Wiles

As reported in the May 1, 2007 issue of New York Times Science, Brennan concluded that the elaborate anatomy of female ducks had evolved in response to, and as a countermeasure against, aggressive males.

“Once they choose a male, they’re making the best possible choice, and that’s the male they want siring their offspring,” she said. “They don’t want the guy flying in from who knows where. It makes sense that they would develop a defense.”

Females protect themselves from undesired insemination through their long and complex oviduct (the equivalent of the vagina in birds). Brennan found that the vaginal tubes were not straight but had “all these weird structures, these pockets and spirals.” This served to impede the sperm’s fertilization mission; unwanted sperm could be stored in side chambers to be ejected later. The success of this design is proven by the fact that as many as one in three duck matings are rapes, but in nine out of ten of these, the offending sperm is eliminated, so 97 percent of all duck offspring are the result of the choice of the mother.

Nature versus nurture

As crazy as such extreme genital development seems, it makes sense in the context of an evolutionary struggle to control reproductive success. When it comes to mating rituals, birds are at the mercy of the purely physical solutions wrought by nature. We, on the other hand, have the ability to modify our nature with our minds and hearts. Nurture plays as significant a role as nature in our partnering. We are lucky to have behavioral choices that some of our bird-brained friends simply don’t have.

Coming attractions: Pet Sex

Can we talk about the sex lives of our cats and dogs? Is that like talking about the sex lives of family members? Ewww! (Or would that be Mee-oww?!)

Credit: Reviewed by Dr. Amy I. Attas 
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