Female Muscovy ducks have spirally, squiggly vaginas that keep out undesired penises. For desired penises, they simply relax their muscles to allow entry. They have evolved this capacity while male Muscovy ducks have evolved 8-inch penises that get fully-erect in a third of a second.
Friends, duck sex is a high-stakes world.
My name is Jeff, and I write this blog. I work as an interface designer in Denver, CO. I am also an amateur musician and an atheist.