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The Corkscrew Arms Race
Male ducks have corkscrew-shaped penises that spiral counter-clockwise, while females have vaginas that spiral clockwise — an evolutionary arms race.
Duck
Anatidae
Ducks have engaged in an evolutionary arms race between males and females, resulting in some of the most unusual reproductive anatomy in birds.
Vital Stats
🏷️ TypeWaterfowl (bird)
🌍 Found InWetlands, lakes, rivers, and coastal areas worldwide
📏 Size30-70cm depending on species
⏳ Lifespan5-10 years in wild
🔞 Sexual Maturity1 year
💕 Mating SystemVaries — some monogamous, some promiscuous
📅 Mating SeasonSpring (varies by species)
👶 Offspring5-12 eggs per clutch
🍆 Penis Size40 cm
⏱️ Sex Duration3 seconds
🔬 Notable AnatomyMales have corkscrew-shaped penises up to 40cm; females have counter-clockwise vaginas with dead ends
⚖️ Sexual DimorphismMales often brightly colored; females camouflaged brown