Dolphins are intelligent, family-oriented mammals very much like us land-loving humans, and a new soon-to-be-published study suggests that we share more than just social structures with our cetaceous friends – well, at least half of us.
Presenting the findings today at the American Association of Anatomists annual meeting, researchers have determined that a dolphin’s clitoris is remarkably similar to that of a human's and, just like most of us ladies, female dolphins may even experience sexual pleasure from its arousal.
What a time to be alive.
"All female mammals have a clitoris, but there have been very few studies that look at the functionality of the clitoris to see if it is for the actual pleasure of the female," study author Dara Orbach told IFLScience. "What's unusual about cetaceans is that they copulate year round even though they can't conceive during certain parts of the year."
To determine the purpose of this year-round sex, Orbach and co-author Patricia Brennan analyzed 11 dolphins that had died of natural causes by creating 3-D tomography (CT) scans, dissecting the animals in order to characterize the morphology of the clitoris, and lastly by creating a histology of the different tissues to see them in different colors and patterns.
"What really surprised us the most is that what we found appears to be nerve bundles that are very large and very abundant," said Orbach, adding that the nerve bundles here look different than they do in other parts of the body. "Just the size of [these nerves] and the abundance is really, really surprising. If they have these nerve bundles, then we can guess this is where their feeling and sensation is passing through their nerves."
Specifically, the researchers note that dolphins have a clitoral hood where these erectile tissues merge into one in a manner similar to the human clitoris. In both species, the erectile tissue of the clitoris is larger than the hood, suggesting the clitoris expands when its sensitivity is increased. In a fashion similar to aroused women, the structure of a dolphin's clitoris tissue suggests it may expand when stimulated, while the skin under the hood contains bundles of nerves that can increase sensitivity, and as such pleasure, just like the human clitoris.
Studies suggest that sex could contribute to the social bonding of dolphins in the same way it does for other mammalian species with year-round copulation, such as humans and bonobos, where sex is pleasurable for females often through clitoral stimulation.
It also appears bottlenose dolphins know something we don't. The clitoris is centrally positioned on the dolphin's belly at the vaginal entrance.
"That means during copulation it is highly likely it is in position to be stimulated by the penis. I can’t think of any position where the male penis wouldn’t be in contact with that clitoris during copulation," said Orbach. However, the researchers note that they did not find evidence of a vestibular bulb, an area of sensitive erectile tissue surrounding the vaginal opening in humans and contributes to orgasm.
Very little is known about female reproductive morphology in most vertebrate species, says Orbach. Her team's research provides a comparative framework to explore other functions of sex that may not be unique to humans.
"Humans we know are really interested in sex. We have an innate interest in sexual experiences and there is a tendency to anthropomorphize animals that is not necessarily justified," said Orbach. "The more we understand about them, the more we can relate and show compassion. It's sex, it's charismatic dolphins, and it's exciting."