While we were looking for the most frequently googled terms associated with cetaceans we encountered the terms “dolphin sex” and “whale penis”. Generally, penises have been far more in the spotlight than vaginas for a long time. For instance, the Icelandic Phallological Museum was established in 1997 in Reykjavík (including a range of cetacean specimens). The Vagina Museum, in contrast, was opened twenty years later, in 2017 in London. So it’s no surprise that even in science, penises have received more attention than vaginas for way too long. Research in biology is not free of single-sex bias. But we are here to change that… and talk about dolphin vaginas.
Luckily, a few scientists have been shedding some light on the mysteries around the cetacean lady parts in recent years. For marine mammals, some of this work has been the first analysis of female reproductive anatomy in more than 100 years.
What does a dolphin vagina look like?
The most striking feature about dolphin vaginas is their shapes. Scientists have known for a long time that dolphin vaginas contained inner flaps and folds. We have to thank curious naturalists for this knowledge who didn’t back off from dissecting whales and dolphins when they washed ashore in the past. Even Greek philosopher Aristotle took note of their internal reproductive organs – more than 2,300 years ago!
So how do scientists conduct their research? Well, one way of investigating how the different parts are connected and arranged in three dimensions is to make silicone models of the vaginas of cetaceans. Using this technique, scientists made an astonishing discovery: Each dolphin species have a special combination of flaps and folds, spirals and twists. Female bottlenose dolphins, for example, have a complex spiral-shaped vagina, while the female harbor porpoises have up to thirteen different folds. These findings brought up more questions than they answered: What is such a complex shape good for? Doesn’t it make it more troublesome for the dolphin penis and the sperm to find the way? Well, that is precisely the point!
A spiral-shaped vagina as a defense strategy
To understand why females of some cetacean species have evolved vaginas looking like cork-screws, you need to know a few things about dolphin sex that might be disillusioning. Reproduction in dolphins is not always a romantic undertaking. For example, in bottlenose dolphins, an alliance of 2-3 males will typically surround a female and capture her. In the vast ocean, it’s presumably beneficial for males to work together to find potential mates and “monopolize” a female. If they cannot gain her sympathies, they won’t shy away from aggression and will prevent any attempts by the female to escape. This behavior of the male dolphins is called herding and can go on for days or even weeks.
The first studies reporting male coercion in dolphins were published almost 30 years ago. However, possible female counterstrategies have been less well studied. Mating in water without arms and legs or anything to hold on to seems tricky already. It requires particular positions of both partners to be successful. Females might be able to avoid mating with a particular male by rolling away from them. However, in case that doesn’t work, she needs another way of keeping control over paternity.
This is where her weirdly-shaped vagina comes into play. In case a female cannot avoid a certain male mating with her, she can reposition herself during copulation. This way, she can steer the penis and sperm away from her valuable egg into a “dead end” – i. e. into one of the flaps. Thus, fertilization becomes unlikely, and the female regains control over who will sire her next offspring.
Looking at dolphin sex internally
And the research on marine mammal genitals doesn’t stop there. Taking it a few steps further, the scientists wanted to know how the dolphin penis and dolphin vagina fit together during copulation. It is a bit graphic, but to do that, they artificially inflated post-mortem dolphin penises, put them in corresponding vaginas, and sewed them together. After staining them, they made C.T. scans and digital 3D models to simulate various rotations of the genitalia. These confirmed that the vaginal complexity was able to limit penetration.
Only species that are known to force mating show these complex genital morphologies. In contrast, the vagina of the common dolphin and the common seal seem to be somewhat accessible. Maybe you have heard the term evolutionary arms race before – this is an arms race between the sexes. Males and females have conflicting interests and try to gain control over reproduction.
Just for pleasure?
Dolphins are one of many species – including humans – to mate, not just for reproductive purposes. Female dolphins can only conceive for specific periods of the year; however, they do have sex all year round, supposedly for pleasure. Studies suggest dolphins have more sex than bonobos, the hippies among the great apes, known for their liberal sex life. Other possible reasons for these activities might be learning, play, dominance, or establishing a hierarchy among several animals. Maybe sometimes it’s just for fun? This is what research may help to understand in the future.
A look beyond cetaceans
Female cetaceans are not alone with complex genitalia. Female ducks and geese were among the first species discovered to also have vaginas formed to prevent unwelcome mating attempts. And if you want to go on a virtual tour inside a duck’s vagina, you can do so with an app called the “VR Duck Genitalia Explorer”.
Reproductive organs come in all forms and sizes and show a greater variety in shape than any other organ. In spiders, the anatomy of the reproductive organs is even essential for the determination of some species. Suppose you want to learn more about musical penises, disposable penis tips, and some crazy badass strategies females use to control which male gets to fertilize her eggs. In that case, I recommend the video below made by Dutch evolutionary biologist Menno Schilthuizen from the Naturalis Biodiversity Center in the Netherlands. There’s still so much to be learned – let’s hope female genitalia will receive the attention they deserve sooner rather than later.
Sources & further reading
- Orbach DN, Marshall CD, Mesnick SL, Würsig B (2017) Patterns of cetacean vaginal folds yield insights into functionality. PLoS ONE 12(3): e0175037. https://doi.org/10.1371/journal. pone.0175037
- Orbach DN, Kelly DA, Solano M, Brennan PLR (2017) Genital interactions during simulated copulation among marine mammals. Proc. R. Soc. B 284: 20171265. http://dx.doi.org/10.1098/rspb.2017.1265
- Ah-King M, Barron AB, Herberstein ME (2014) Genital Evolution: Why Are Females Still Understudied? PLoS Biol 12(5): e1001851. doi:10.1371/journal.pbio.1001851
- Connor RC, Smolker RA, Richards AF (1992) Two Levels of Alliance Formation among Male Bottlenose Dolphins (Tursiops sp.). PNAS USA 89: 987–990.
Did you like our article on dolphin vaginas? You might enjoy reading more about marine mammal biology here. You can also check out our post on sexual pleasure in dolphins:
Hanna is a biologist from Germany with focus on marine mammals. During her university days she was involved in research projects in Italy, Australia and also Iceland. This is where she has spent most of her time since receiving her Master’s degree. Here she has been working as a naturalist for whale watching companies in different parts of the country. Since starting to work as a guide and lecturer on polar expedition cruises in 2017, she has been migrating between Iceland and Antarctica sharing her passion for cetaceans and seals.