Not The Ducks' Nuts
Newcastle Herald
Tuesday August 7, 2007
THE male Argentine lake duck has a phallus that is longer than 30 centimetres as long as itself that is shaped like a corkscrew.
The female Argentine lake duck, not surprisingly, has a spiralling vagina, but in the opposite direction.Patricia Brennan, a biologist at Yale University, is studying the vaginas and penises of various species of duck.There is a widespread theory that the vagina has evolved to receive a penis, but Brennan's hypothesis is that the female's reproductive tract evolved to keep out unwanted male penises. Only 3 per cent of male birds have a penis, but long penises exist in species where the male duck must compete to mate with the same female. Those with longer penises are able to get sperm further down the oviduct than others, increasing the chances of impregnation. Brennan says many species force themselves on females, despite them already choosing a mate. Without full co-operation a complicated, reverse-spiral vagina would make the possibility of impregnation by an intruder small. Some duck vaginas even have pockets and cul-de-sacs.Brennan describes it as an evolutionary arms race, in which both sexes are adapting to gain control of reproduction. But Brennan believes the male member evolved to adapt to the convoluted vaginas, not the other way round.Brennan still does not know how the males benefit from their corkscrew-shaped members, but she is hoping to get clues by coaxing male ducks to mate with a female decoy with an anatomically correct vagina made from a thick glass tube to see how the penis fits.
© 2007 Newcastle Herald
