Normally, the duck keeps its penis inside-out within a sac in
its body. 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. The whole process takes just a third of a
second and Brennan captures it all on high-speed camera. This
isn’t just bizarre voyeurism. Duck penises are a wonderful
example of the strange things that happen when sexual conflict
shapes the evolution of animal bodies. Childhood… violated…
Innocence… lost… SCIENCE!Many ducks form bonds between males and
females that last for a whole mating season. But rival males
often violently force themselves onto females. 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. These extreme penises are even more unusual when
you consider that 97% of bird species lack any penises
whatsoever. But female ducks have devel