Fruit bats engage in fellatio, obviously, but does this sexual behavior decrease or increase total copulation time? A group of researchers videotaped and carefully analyzed bat mating behavior and found that fellatio strongly correlated with longer copulation time. Lu and Tirth discuss this incredible study on S01E01 of the Recreational Science podcast (timecode 7:08):
Lu: Tirth, this paper I picked specifically for you because you’re going to love it.
Tirth: I’m hyped, as the kids say.
Lu: This study was published in 2009. It’s an oldie but a goodie. It’s in PLoS ONE, one of the greatest journals ever, in my opinion.
Tirth: One of your favorite journals, if I recall.
Lu: The title is, “Fellatio by fruit bats prolongs copulation time.” Let’s break that down, all right? Let’s break that down.
Tirth: Yeah, let’s go. Word by word.
Lu: The title of this paper is not “Fruit bats engage in fellatio,” But that fellatio increases copulation time.
Tirth: I have so many questions.
Lu: Yeah, well let me give you the introduction and then you can jump in with your questions, okay?
Tirth: Yes.
Lu: So, Tirth, you might not know this, but fellatio is often used in human foreplay. Okay? You know that? You probably didn’t. That’s okay.
Tirth: No, news to me.
Lu: But it’s rarely been recorded in non-human animals. So this group from China decided to examine whether fellatio occurs in fruit bats. The specific species of fruit bats are the short-nosed fruit bats. The Latin name is Cynopterus sphinx. And not much is known about their sexual behavior because they are nocturnal and it’s very hard to observe such matters in the dark.
Tirth: Indeed. I guess my first question is, do they have sex hanging upside down? How does that work?
Lu: That’s a great question. Yes, they do hang upside down and yes, Tirth, I know what you’re thinking. There are videos available, included with the study.
Tirth: There are? Can you send me the links?
Lu: Of course.
Tirth: For science, of course.
Lu: Yeah, of course. So this study was conducted in Guangzhou, China. This group captured and marked 30 females and 30 males of this species of bat and placed them into cages. They were fed, provided nesting material. They did exclude young bats and also pregnant females and lactating females.
Tirth: Why young bats?
Lu: Like prepubescent bats were excluded, for obvious reasons.
Tirth: Okay, that makes sense. Well I just, I don’t know how young, maybe they were inexperienced and they’re worried they couldn’t have sex.
Lu: Mm no. The equipment they used is a Pico 2000 series multimedia digital video recorder. Very fancy, very high-tech.
Tirth: Is this is this top of the line?
Lu: It’s top of the line. They recorded from 7:00 p.m. to 7:00 a.m.
Tirth: Wow.
Lu: Yeah. And uh… Look, one criticism right away. The entire 12 hours of footage is not available. I looked, it’s not available. You know, that’s one criticism. Not all the data were made available. And they ended up observing 20 copulations from different pairs.
Tirth: In a single night.
Lu: Well they had 30 females and 30 males. Twenty different copulations from different pairs. So, what did they find? Well, in 14 of the 20 copulations, the female licked the shaft or the base of the male penis frequently. The average duration of penis licking was 19.14 seconds plus or minus 3.45 seconds, which is about 8.7% of the average duration of copulation.
Tirth: So the average copulation was less than two minutes.
Lu: So here is the main point of the paper: if no fellatio occurred, the average copulation time was 122 seconds. Just over two minutes.
Tirth: That’s pretty long as it is.
Lu: Well, for you. For you, not for the rest of us, okay Tirth? Please, speak for yourself.
Tirth: I think people lie a lot, at least I’m being honest.
Lu: Yeah, sure. So that’s no fellatio, just over two minutes. But if fellatio did occur, the average copulation time went up to 220 seconds.
Tirth: Wow.
Lu: It went up by 100 seconds.
Tirth: Wow. I would pay obscene amounts of money to last that long.
Lu: And there’s a strong correlation between fellatio time and copulation time. The Pearson’s correlation, R, is 0.828.
Tirth: Wow.
Lu: Very strong correlation.
Tirth: I’ve almost never seen an R that high in anything I’ve seen or read. I think even for smoking and lung cancer, the R isn’t that high.
Lu: That’s how you know this is a good study. So, you might ask, what did they conclude from all this?
Tirth: Yes.
Lu: Well, they suspect that prolonged copulation may be a method of mate guarding by the female. You keep the male on you for 100 seconds longer, that’s 100 seconds less time they’re going to spend chasing after other mates.
Tirth: Or playing video games.
Lu: Or, yes. Okay, good joke.
Tirth: Thank you.
Lu: And then also, potentially, prolonged copulation stimulates the pituitary gland in the female, which might increase the chances of fertilization. It’s very speculative, but you know, the results speak for themselves, I think. There’s a clear correlation between fellatio and copulation time.
Tirth: I’m convinced. I mean, I would just like to know what motivated this study in the first place. Are these people zoologists?
Lu: They are zoologists, I believe. Or bat hobbyists. I’m actually not 100% sure. Motivation, you know, motivation is an interesting question. You’re asking about the significance, right? Why did they do this?
Tirth: Basically, yes. Is there a fertility crisis amongst fruit bats?
Lu: That’s a good question. These fruit bats they noted are near threatened in terms of conservation status. So, potentially, if they ever become endangered, this could be useful information to help them repopulate. But more important than that, I think this really gets at “what is science?” Right?
Tirth: Mhmm.
Lu: Science as we know is fundamentally about evidence and data right?
Tirth: Yes.
Lu: It’s about empiricism. It’s about a posteriori knowledge, not a priori knowledge.
Tirth: Well, sometimes it’s informed heavily by a priori knowledge.
Lu: Yes, but ultimately, it’s about a posteriori knowledge.
Tirth: Which then becomes a priori knowledge going forward, right? I mean it’s a chain.
Lu: Mhmm. Meaning you can make hypotheses and assumptions, but they’re not worth much unless you have evidence.
Tirth: Correct.
Lu: So Tirth, look, you can assume that fruit bats engage in fellatio.
Tirth: Uh-huh.
Lu: You can assume that fruit bat fellatio prolongs copulation time because fruit bats don’t have lips, and so the fellatio doesn’t feel as good. So it doesn’t, you know, it doesn’t do anything for the male.
Tirth: They can’t get there.
Lu: You can assume all these things, but you just can’t know until you have the actual video evidence.
Tirth: Until you actually do it and record it for 12 hours.
Lu: And record it for 12 hours. Like I said, the video is available on the journal’s website and I kid you not, it is set to music.
Tirth: No, it’s not.
Lu: It is set to music. I encourage everyone to go and watch it.
Tirth: Wait, is it jazz music?
Lu: It’s not the kind of music you would expect.
Tirth: It’s not jazz music?
Lu: It’s not jazz music. It’s an interesting choice. I’ll just say that. Everyone should go and watch it for science. All right, what do you think Tirth?
Tirth: That was quite incredible. Let me ask you this. 12 hours of video footage of 30 mating pairs is a little, that’s a lot. Who do you think was tasked with watching every single minute of this footage? Was it an undergraduate? Was it a graduate student? Or was it the postdoc or was it the PI?
Lu: I would assume everybody had a go. They probably took turns.
Tirth: Just like the bats themselves, I suppose. This is incredible.
Article citation
Tan et al., 2009. Fellatio by Fruit Bats Prolongs Copulation Time. PLoS One. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0007595
Leave a Reply