Do the twist. The male duck’s penis is spiral-shaped: like a corkscrew, it twists in a counter-clockwise direction so that sperm will target the oviduct on the female’s left-hand side.

Scientists have elucidated the mechanism by which female ducks thwart forced copulations. Unwanted sex is an unpleasant fact of life for many female ducks. After carefully selecting a mate ...

Julia A. Clarke is at the Jackson School of Geosciences, The University of Texas at Austin, Austin, Texas 78712, USA. All steamer ducks also walk proficiently on land, and dive to feed and to ...