[♪ INTRO] Seeking pleasure comes naturally to us humans, and we experience it through a lot of different ways, including sex.

And while humans, along with most other organisms, do have sex in an effort to pass on their genes, that is not the only reason we do it. And we aren’t alone in this; other organisms also seek the feeling of sexual pleasure, even outside mating purposes.

Scientists started to take notice of this behavior in other animals and figured out that sex likely feels pretty darn good for other species, not just us. But why they experience pleasure in the first place, and what some of the other reasons they keep doing, even when it isn’t leading to offspring, might be… That is what led scientists down an evolutionary rabbit hole. From an evolutionary perspective, it makes a lot of sense for sex to feel good.

I mean, if it is pleasurable, it encourages partakers to keep doing it, increasing reproduction along the way. Scientists have done a lot of research around this, but mostly in the context of male mammals. In rats, for example, sexual behavior has been shown to be very rewarding.

And regardless of other sexual opportunities, ejaculation remained the male rats’ top priority. But ejaculation is a key component of mating after all; pleasure isn’t a requirement. And that’s the challenging part; knowing if non-human species experience pleasure during sexual encounters isn’t as straightforward.

It’s not like researchers can pop by with a clipboard and ask, “hey…was it good for you?” What scientists can do is look for other cues that the animals are in it for the good times. For one, researchers can, well, they can look at their genitals. Take dolphins, for example.

In a 2022 study, scientists uncovered that the clitoris of common bottlenose dolphins is shockingly similar to humans in shape, nerves, and tissue. It’s also positioned in a way that’s very likely to be stimulated during sex. Dolphin behavior also tips us off that this organ seems to function in a pleasure-related way too, considering that female dolphins appear to masturbate and even stimulate each other outside of mating purposes.

But still, it’s pretty tricky to describe sexual pleasure in female dolphins with confidence, so scientists also looked for more easily recognizable climax cues in some of our closer relatives, Stump-tailed macaques. Scientists have observed females-only pairings of this monkey species showing clear signs of climax. They exhibit multiple internal and external cues.

Their bodies tense, their hair stands on end, and they let out repeated vocalizations along with making a conspicuous facial expression. On top of that, they experience internal uterine contractions and an increased heart rate, all followed by a suddenly relaxed state. Very similar to what is documented in humans.

And females kept searching for these experiences, even though the encounters didn’t lead to offspring. A sign to scientists that, in this case, their behavior had little to do with reproduction. Even when it came to male-female interactions, the timing of their ovulation didn’t appear to make a difference.

So fertility didn’t seem to play a role in their heterosexual interactions either. While it makes evolutionary sense that sex might be more pleasurable when pregnancy is most likely, that didn’t appear to be the case for these monkeys, so sexual pleasure is probably a lot more widespread than we currently know. Now, so far, we’ve been pretty focused on mammals, and to be fair, so is the research as a general rule, but sexual pleasure has actually been documented in one of the most famous lab critters… the fruit fly.

In a study published in 2018 in the journal Current Biology, researchers genetically engineered male fruit flies so that exposure to a red light made them…ejaculate. And it turned out these flies really liked hanging out in the red-lit part of their enclosure. As in, they were hanging out there on account of, you know, the automatic release.

Not only did they get some instant and repeated gratification as a result, but it also helped to reduce their consumption of ethanol, the star molecule in things like beer or your favorite cocktail. That’s because the flies tend to seek out other pleasurable experiences in the absence of sex, like drinking alcohol. But pleasurable sex might not always be as simple as leftover evolutionary baggage that encourages us to breed in the first place.

There are other evolutionary advantages to feeling pleasure during sexual activity. For one, pleasure might help prolong the act, increasing the likelihood of successful fertilization. So, to get more bang for their buck, short-nosed fruit bats incorporate oral stimulation during mating to prolong their session.

And it makes a significant difference. For every second of licking, the sex lasted 6 seconds longer. Now, while these observations can’t conclude exactly why this behavior is occurring and how pleasurable it actually is, it is likely that the mating add-on increases the chance of offspring.

In buffalo weavers, a type of songbird or passerine, it appears that pleasure not only helps with male ejaculation, but it might also help them get a leg up when it comes to sperm competition. These birds have a penile-like structure that gets stimulated during mating, inducing orgasm and ejaculation. And for buffalo weavers, sex and mounting can last quite a while, around 12 minutes.

This is pretty odd behavior for birds in general, because birds are pretty notorious for very short sex, lasting mere seconds. Most passerines, along with many other birds, don’t have penises. Both sexes of birds have a cloaca, an opening that serves as the end of both their digestive and reproductive tracts.

Passerine males would normally just get a swollen cloaca around mating season. But not Buffalo weavers, they have this whole penile-like structure outside the front of their cloaca. And when it is rubbed against the female’s cloaca during prolonged mating, it gets stimulated, which researchers found leads to orgasm and ejaculation.

A key part of buffalo weavers mating. You see, these birds breed in colonies, and males are in pretty intense competition with each other when it comes to successfully passing on their genes. One hypothesis is that a penile-like structure requires more stimulation to ejaculate; this takes up a lot more of their mate’s time, so she’s less available to be fertilized by other competitors.

So pleasure that leads to greater sperm success seems like an evolutionary slam dunk in terms of having a reason to experience the good feelings. But how frequently and intensely some animals experience sexual pleasure can be complicated and it isn’t always just about the physical act itself. In some cases, sexual pleasure might have also evolved to send us messages about who we should be doing it with, to begin with.

In a study of Japanese macaques, their partners’ duration and physical efforts played an important role in how pleasurable the sex was. But something else influenced the level of pleasure a female exhibits too: social status. Lower caste females orgasmed when mating with higher ranking males.

But it seems that this power imbalance only worked in one direction, because when higher ranking females were paired with lower status males they weren’t as pleased. Since social hierarchy seems to help determine how pleasurable sex is for these macaques, it might be that these monkeys' orgasms are actually an adaptation to influence mate selection. But we’re starting to figure out that sexual behavior isn’t strictly about reproduction.

Shared pleasure outside of breeding plays important roles in animals’ social lives, which takes us back to dolphins. Long-term studies of bottlenose dolphins have shown that both sexes and a wide range of ages participate in sexual activities year-round, not just during the mating season. And during a long-term study, researchers observed more same-sex encounters, especially between males.

They often form a tight-knit group that can last for 15 to 20 years, and sexual interactions appear to help them create and maintain social bonds with each other. Although we cannot be completely sure that this is the only explanation for this behavior, it does show that pleasure goes beyond reproduction; it also plays a very important role in the social lives of dolphins! For other animals, sexual interactions are also useful to help prevent strained relationships within their community.

Bonobos are extremely close to humans, evolutionarily speaking. And boy, are they famous for their active sex lives. From a young age, bonobos engage in a wide range of sexual interactions with all sex and age combinations.

For many reasons beyond reproduction too, from social bonding to stress reduction. That’s because bonobos are a very social species, and most of their interactions are pretty much egalitarian, but when conflict bubbles up, they take a different approach to conflict resolution. Females are at the center of the community, so they might reconcile differences through sexual behaviors, which works to ease the tension in certain situations, like in conflicts over food availability.

But at the end of the day, although animals experience pleasure in multiple ways, we still don’t know just how widespread sexual pleasure really is. Until an animal translator is created, it will remain very difficult to know the extent of pleasure that other species are feeling. But there is some pretty strong evidence that, much like us, many other animals appear to just really enjoy a wide range of sexual behaviors.

And not only that, they’re seeking sexual contact out for a much more complex range of reasons than we often give them credit for. Thanks for watching this episode of SciShow, which we weren’t ever going to get sponsored by a normal sponsor… So, thanks to our patrons! We have made thousands of educational videos over the years, and we’ve been able to offer them for free because of our patrons.

So, to all of you — thank you for what you do to make SciShow happen. If you are not a patron, but want to learn more about what that means, you can go to Patreon.com/SciShow. [♪ OUTRO]