FEW birds have penises, but the Argentine lake duck Oxyura vittata is one
sizeable exception. Its corkscrew-shaped member was thought to be about 20
centimetres long—half the duck’s body length.
But Kevin McCracken of the University of Alaska found one aroused specimen
whose penis was out of the body sac where it usually resides. It measured a
whopping 42.5 centimetres.
“This is the first record of the penis ‘hanging out’ in its natural form,”
says McCracken. He suggests that this highly promiscuous bird displays its penis
to attract females, which might explain why evolution has favoured length
(Nature, vol…
