Female mallards and other wildfowl have evolved vaginas with spiral channels, dead-end pouches, and twists that run in the opposite direction to the male’s penis. These features are a series of barriers and obstacles within the vaginal canal that make forced copulation difficult and help prevent fertilization by unwanted males.
Female mallards and other wildfowl have evolved vaginas with spiral channels, dead-end pouches, and twists that run in the opposite direction to the male’s penis. These features are a series of barriers and obstacles within the vaginal canal that make forced copulation difficult and help prevent fertilization by unwanted males.