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There is still a great deal of controversy over these theories and more research is needed to establish one way or another which theory or theories best explains the co-evolution of mallard sexual organs. One way or another, sexual conflict is at the heart of why drakes have complex intromittent organs, and why females have developed elaborate defensive vaginas. Females invest far more in the offspring than the males do, and this trait preserves their ability to select for better mates. Better mates increase her own chances of survival directly, but more importantly, they give her offspring higher fitness. This ensures that her own genes will be more likely to spread throughout the population, even if she still had to do most of the work on her own.

Sexual deviance in mallards

Did you know that mallards are one of the few species that have been observed practicing homosexuality and one of even fewer that have been noted to practice homosexual necrophilia?

In 2001, a researcher sitting at his desk at the Natuurmuseum of Rotterdam heard a loud bang and looked outside his window to find two mallard drakes; one was in full breeding plumage while the other in post-breeding moult. It was found that the breeding male was chasing the other drake in an attempted rape flight before the latter smashed into the building’s wall instantly dying, but still not losing his undesired partner’s interest (Moeliker).

What followed for the next 75 minutes was an unprecedented torrent of passion captured on camera by the researcher who eventually ended the scene by removing the mallard corpse. C.W. Moeliker would go on to publish his findings and earn one of the ten 2003 Ig Noble Prizes (Moeliker 2001).

Free love in Anatidae

Homosexual behavior in animals has been documented but not well studied. Ducks in particular have often been observed practicing male homosexuality. Mallards in particular have been noted to have up to 19% of pairs be homosexual (Bagemihl 1999).

It’s up to brilliant future researches like yourself to uncover the mysteries behind this act which seems to have no apparent fitness benefit, and in fact doomed one species to extinction. The blue duck species pictured below is now going extincti as the last three individuals, a female and two males, have chosen sterile relationship paths. The males have bonded while the female remains solitary. Future studies of this duck species will be impossible, so comparative methods with other duck species will have to be used to understand this bizarrre phenomenon.

A blue duck
From<http://en.wikipedia.org/wiki/File:Whio_(Blue_Duck)_at_Staglands,_Akatarawa,_New_Zealand.jpg>.

Discussion questions:

  1. Which gender do you think first began to evolve the complexity leading to sexual conflict?
  2. What is the social monogamy in mallards like?
  3. Why don’t males in other species practice forced copulation?
  4. Why would matching male and female genital complexity exist in certain species and how does this apply to mallards?
  5. Why might the hen’s unconditional resistance be selected for and how might this affect selection on the drake’s phalluses?
  6. Ethics bonus question: Can mallard drakes be held morally responsible for forced copulation?

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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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