Video reveals twists and turns of genital warfare in ducks

An extraordinary sexual arms race that has played out in duck ponds for thousands of years has been uncovered by evolutionary biologists.

Faced with unwelcome advances from undesirable males wielding large, corkscrew-shaped penises, the females have gone on the defensive. The solution – the result of millennia of evolution – arrived in the form of vaginas that spiral in the opposite direction, so thwarting uninvited males at a stroke.

Some female ducks possess genitalia of labyrinthine complexity, with kinks, dead ends and hairpin bends.



Slow motion footage of male Muscovy ducks showed their penises extend with explosive speed, reaching a full 20cm in 0.36 seconds. "We think this allows the male to actually force copulations on females even as they struggle to escape," said Patricia Brennan, professor of evolutionary biology at Yale University in New Haven, Connecticut.

The males' attempt at insemination was barely impaired by models of straight and only slightly curved female genitalia, but the more tortuous vaginas effectively blocked the males before they got too far.

"It shows in a very clear way how females can regain control of reproduction. Even though they can't behaviourally prevent males from forcing them to copulate, they have regained control of the 'copulatory area' by preventing males from fully everting their penises when they do not want to copulate." "It is really a genital war."

Full story with video here.