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Bottlenose Dolphin (Tursiops truncatus) swimming in Hawaii.

Flip Nicklin/Minden Pictures

Everything you always wanted to know about dolphin sex—but were afraid to ask

Whales and dolphins have surprisingly interesting sex lives, replete with various positions, elaborate vaginas, and a rare type of penis that’s always mostly erect. Dara Orbach, a marine mammologist at Dalhousie University in Halifax, Canada, has been studying these elaborate cetacean hookups for 7 years—and she’s made some shocking discoveries, some of which she’ll be presenting today at the Experimental Biology 2017 meeting.

Science sat down with Orbach to chat about her work—and the best part about studying the sex habits of some of the ocean’s most famous creatures.

This interview has been edited for clarity and length.

Q: Let’s start with the most obvious question: Why study this?

A: Copulation is the most direct possible interaction between males and females, but we know so little about it largely due to the physical challenges of studying it, especially with underwater creatures. So it’s only by looking internally at the animals while they’re copulating that we can understand more about these mechanisms. We do this by looking at tissue samples from animals that died of natural causes. We use whole penises and whole vaginas. 

Q: And then you go into the lab and put them together like puzzle pieces?

A: Yeah. But what makes our study more unique is that Diane Kelly, one of my co-authors, found a way to inflate these penises to their full erect size, which hasn’t been done before. If you think about a specimen that is postmortem, it’s going to start to shrivel up. We found a way to inflate them so they would be the most close mimic of what a real intromission would look like.

The bottlenose dolphin's vagina, seen here in gray, contains a number of intricate folds and flaps which the male's penis (red) must navigate if he is to deposit his sperm as close to the egg as possible. 

Dara Orbach/Dalhousie University

Q: How does one inflate a dead dolphin’s penis?

A: We used pressurized saline, so essentially we had a nitrogen tank and we filtered the air under pressure into a smaller keg—like a beer keg—which was full of saline, and then pumped that into the penis.

Q: What are female genitals like to work with?

A: They’re amazing just because of this diversity, which has never been documented before. You open them up and you’re not really ever sure what you’re going to see inside. Is it going to be relatively simple? Or will there be these spirals? Or will there be deep folds? Or shallow ones? Opening up each reproductive tract is unique, and you never know what you’re going to see with a new species.

Q: In the wild, how do dolphins copulate?

A: It’s very variable. Some species, like dusky dolphins, copulate belly to belly. Bottle nose dolphins seem to make a T-formation, where the male crosses the female exactly at her midline. Harbor porpoises are really unique in that they wait for the female to come to the surface of the water to take a breath and then they leap out of the water and try to hook her with their penises.

Q: Could it be that some of the positions are just for fun?

A: This is what the whole purpose of the research is to understand. They have sex all year round even when they can only conceive for certain periods of the year. By looking at how the genitals align, we can now say certain body positions are more likely to lead to successful fertilization than others, which might be for purposes other than reproducing. Is it play? Is it working out hierarchies? Is it establishing dominance? Is it learning? There could be many functions of sex.

Q: What is the best and worst thing about this line of research?

A: I think the best thing is how exciting it is. I’ve never told anyone what I’ve done, and they’ve been bored with listening to me talk about it. Also, it was so faux pas to study sex and sexual behavior and genitalia for a long time that it really is an understudied field and there’s this huge opening in terms of new research directions. It seems like the sky is the limit.

The worst part? I don’t know if there is a worst part. I really, really love my job.