![]() ![]() For a start, they are flexible when erect. Now, she has found further evidence that these complex genitals are the result of a long-lasting war of the sexes.ĭuck penises (and those other birds) work in a different way to human ones. Two years ago, Brennan showed that duck species whose males have the longest penises tend to have females with the most elaborate vaginas. They are organic chastity belts, evolved to limit the effectiveness of the males’ lengthy genitals. Their vaginas are equally long and twisting, lined with dead-end pockets and spirals that curve in the opposite direction. These extreme penises are even more unusual when you consider that 97% of bird species lack any penises whatsoever.īut female ducks have developed countermeasures. To gain the edge in these conflicts, drakes have evolved large corkscrew phalluses, lined with ridges and backward-pointing spines, which allow them to deposit their sperm further into a female than their rivals. ![]() But rival males often violently force themselves onto females. Many ducks form bonds between males and females that last for a whole mating season. Duck penises are a wonderful example of the strange things that happen when sexual conflict shapes the evolution of animal bodies. The whole process takes just a third of a second and Brennan captures it all on high-speed camera. When the time for mating arrives, the penis explodes outwards to a fully-erect 20cm, around a quarter of the animal’s total body length. ![]() Normally, the duck keeps its penis inside-out within a sac in its body. Patricia Brennan from Yale University is trying to encourage male Muscovy ducks to launch their ballistic penises into test tubes. ![]()
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