Animal reproductive systems and practices can be incredibly complex - often more complicated than our own human mating rituals and reproductive cycles. Most research in the animal sciences field focuses on male genitalia and sex habits. Researchers found that of 364 published research papers, only 8% focused on female animals and their genitalia.
However, sexism might not be the definitive reason for this gender gap. Due to their internal nature, vaginas are inherently more difficult to study than penises. Even with such little research, the things we do know about the vaginas of the animal kingdom are incredibly interesting. Hopefully, in the future, the scientific community will put an equal amount of research focus on female reproductive systems in the animal world - because there are some interesting ones out there.
While marsupials are mammals, they have some anatomical features that make them unique in the animal kingdom. They are probably best known for the unique practice of carrying their young in pouches, but that’s only one of many amazing facts about the marsupial reproductive system.
Females technically have three vaginas and two uteruses (or uteri); one is strictly used for giving birth, while the other two are connected to their uteruses. This adaptation allows animals like kangaroos to be 24/7 baby-making machines. They can have two fetuses gestating at once, a newborn in their pouch, and a juvenile by their side all at the same time. Not only can they have a lot of babies, they can also practice a form of self-regulated birth control in times of drought, postponing pregnancies until they determine they are ready.
The desert grassland whiptail lizard is an all-female species of reptile that is native to the Southwestern United States and Mexico. They reproduce through a process called parthenogenesis, an ability that allows them to cross their own chromosomes and give birth to clones of the mother.
Astonishingly, this process can be triggered by female-to-female pseudo sex between two whiptail lizards. This phenomenon is known as pseudocopulation, and basically consists of the two females mounting each other, intertwining tails and wriggling as if copulating.
Female ducks are unique because they have vaginas - most birds don't have vaginas or penises but a single opening known as a cloaca (or vent) responsible for all reproductive and digestive needs. Female duck genitals are also distinctive because of their shape. The shape of a duck's vagina is elongated and spiraled to deter unwanted entry.
Male ducks are known for their sexual aggression and deviance, and a sort of genital competition has developed between the two sexes. To enter a female, a male duck's penis must be the correct shape, much like a corkscrew, and must spiral in the correct direction. That means if the female has a vagina that spirals clockwise and the male has a penis that goes counter-clockwise, the male cannot successfully enter and reproduce with the female.
Hyena social dynamics are determined by the females, with an alpha female leading the pack. In hyena society, the alpha eats first, followed by the rest of the females, and then finally the males are allowed to join in at the end. This allows female hyenas to grow bigger and stronger than their male counterparts, and they even have tougher immune systems than the males.
They also have one of the most unique reproductive organs in the world. Hyena females come equipped with the largest clitoris of any animal, with some growing to 7 inches in length. They have been referred to as pseudo-penises due to a phallic appearance, and are used for everything from sex, to urination, to birth. Birth requires females to push two pound infants through a birth canal in the clitoris with a one inch diameter. The process often leads to clitoral tears, which can be fatal, as evidenced by a high death rate in first-time hyena mothers.