Like humans, female bottlenose dolphins experience sexual pleasure through their clitoris, according to new study in Current Biology.
Study author Patricia Brennan, an evolutionary biologist at Mount Holyoke College, examined 11 clitorises from adults, juveniles and calves of naturally deceased dolphins under the microscope and using CT scans. She found several signs that the clitorises were fully functional.
Clitoral erectile tissue in dolphins has inflatable spaces that are similar to humans. In humans, blood rushes to these spaces upon stimulation, making the clitoris swell. In the video abstract, Brennan says this seems to be the case for dolphins as well. The shape of the female dolphin’s erectile tissue changes with maturity, suggesting it becomes functional with age.
Brennan also found large nerve bundles connected to free nerve endings underneath the clitoral skin. The skin itself is three times thinner than other nearby genital tissue, which would make the area prime for higher sensitivity.
The researchers also found structures called genital corpuscles, which are nerve endings found in the skin of human genitalia and nipples. They are involved in the sexual pleasure response in humans, and the study states “their presence suggests a similar function in the dolphin.”
“A lot of people assume that humans are unique in having sex for pleasure,” Justa Heinen-Kay, a researcher at the University of Minnesota who was not involved with the paper, tells the New York Times’ Sabrina Imbler via email. “This research challenges that notion.”
The study’s findings are unsurprising to those who research dolphins, per the Times. Bottlenose dolphins are highly sexual creatures. They have intercourse throughout the year, even during periods when conception is not possible. This activity helps establish and maintain social bonds, the study states. They also frequently engage in homosexual intercourse.
Evolutionarily, it makes sense that intercourse is pleasurable for females, because that would lead to an increase in copulation and reproduction, Brennan says in the video abstract.
“The only thing that surprises me is how long it has taken us as scientists to look at the basic reproductive anatomy,” Sarah Mesnick, an ecologist at NOAA Fisheries who was not involved with the research, tells the Times. She adds that studying social behavior in animals can help researchers better understand their evolution, which could help with management and conservation.
Female sexual pleasure in nature has not been well-researched and scientists didn’t even fully describe the human clitoris until the 1990s, says Brennan. Even in human medical research and in the medical curriculum, clitoral anatomy is largely missing, writes Calla Wahlquist for the Guardian.
“This neglect in the study of female sexuality has left us with an incomplete picture of the true nature of sexual behaviors,” says Brennan in a statement. “Studying and understanding sexual behaviors in nature is a fundamental part of understanding the animal experience and may even have important medical applications in the future.”