Female Dolphins Have Weaponized Their Vaginas to Protect Themselves

Female Dolphins Have Weaponized Their Vaginas to Protect Themselves

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In nature, it’s common for males and females to attempt to one-up one another with different reproductive strategies, but female dolphins might well have one of the most advanced systems around for protecting themselves from unwanted males.

During mating, male bottlenose dolphins will form small groups that will surround a female, isolating her. Generally, she’ll mate with all of them, but this isn’t great for her. One, she doesn’t have much choice in the matter, and the psyche of the dolphin has been shown to be complex enough that I’m fairly certain this would be traumatic.

Regardless, female bottlenose dolphins have evolved a type of defense. Their vaginas are extremely complex with many folds that may allow them to isolate their preferred partner and only allow that one’s sperm to fertilize her eggs. Ducks, for example, use a similar system to protect themselves from “forced copulation,” to use the eerily detached scientific term.

Scientists only learned all this recently, though. Dolphin penises had been well studied in dolphins and their parent group, cetaceans (these include whales, porpoises, and other intelligent marine mammals), but female genitalia had been rarely studied.

Dara Orbach of Dalhousie University in Canada wanted to fill in those gaps. To do this, they created silicone molds of various cetaceans to study their anatomy and see what there was to learn.

“There’s this unparalleled level of vaginal diversity that we had no idea existed before,” Orbach told New Scientist. Because ducks are one of the only other species with such complex features, Orbach wanted to test if cetaceans were using their specialized genital anatomy to control fertilization like ducks.

To do this, they gathered parts from several specimens that had died of natural causes. Then, they’d inflate penises with a saline solution and compare them against the vaginal samples of that species. Both common dolphins and seals evolved to make sex easy and straightforward. But porpoises and bottlenose dolphins had much more diverse vaginal folds and structures.

“She may not choose who she mates with, but might be able to choose which male or, more precisely, which sperm, fertilizes her egg,” Janet Mann of Georgetown University told New Scientist.

All of them also required very precise positioning for penetration to work at all. Both Orbach and Mann, matched up their study of the anatomical molds with mating patterns that the two had observed in the wild. But, the fact that the folds are complex and that the positioning required is so precise, the two researchers suggest, the female may be able to make subtle movements during sex to prevent fertilization.

“It might appear behaviorally that females are very passive,” Orbach said. “But looking at the reproductive anatomy, we’re learning that they have all sorts of cryptic ways to control paternity.”

Either way, this whole situation seems just a bit messed up. Dolphins, like we said, are more than complex enough to know what trauma is. They mourn their dead, and have complex, nuanced relationships. The idea that ducks would, essentially, sexually assault one another is a little weird, but can kinda be dismissed on the basis of their relative simplicity. Dolphins though? They’re just messed up. Then again they also commit genocide, so clearly they aren’t the best moral role models around.

Well, at least the females have one more to tool to protect themselves.