Not Exactly Rocket Science

Many humans whinge about not getting oral sex often enough, but for most animals, it’s completely non-existent. In fact, we know of only animal apart from humans to regularly engage in fellatio – the short-nosed fruit bat (Cynopterus sphinx).

The bat’s sexual antics have only just been recorded by Min Tan of China’s Guangdong Entomological Institute (who are either branching out, or are confused about entomology). Tan captured 60 wild bats from a nearby park, housed them in pairs of the opposite sex and voyeuristically filmed their liaisons using a night-time camera. Twenty of the bats got busy, and their exploits were all caught on video.

Male bats create tents by biting leaves until they fall into shape. These provide shelter and double as harems, each housing several females who the male mates with. Fruit bat sex goes like this: the female approaches and sniffs the male, and both partners start to lick one another. The male makes approaches with his thumbs (like the Fonz) and mounts the female (like the Fonz). Sex itself is the typical rhythmic thrusting that we’re used to, and afterwards, the male licks his own penis for several seconds.

But Tan also found that female bat will often bend down to lick the shaft of her mate’s penis during sex itself. This behaviour happened on 70% of the videos, making it the only known example of regular fellatio in a non-human animal. It also prolonged the sexual encounter – males never withdrew their penises when they were being licked and, on average, the behaviour bought the couple an extra 100 seconds of sex over and above the usual 2 minutes. The licking itself only lasted for 20 seconds on average, so each second of it buys six extra seconds of penetration.  



NSFW – short-nosed fruit bats having sex. I will have you know that the music choice came with the video and has nothing to do with me.

Oral sex is rare in other animals. Bonobos do it (but really, what don’t they do?) but it’s more of a form of play among young males, and there’s one anecdotal instance of an orang-utan doing the same. Some animals, such as ring-tailed lemurs, lick each other’s genitals to judge whether they’re ready for mating, but there’s no evidence that they do so as an actual part of sex. As for other bats, it’s entirely possible that they too engage in oral sex. However, given their inaccessible roosts and nocturnal habits, we’re largely in their dark about their sex lives.

Nonetheless, Tan suggests a few possible reasons for the short-nosed fruit bat’s penchant for fellatio, aside from the anthropocentric conclusion of ‘pleasure-giving’. Bat penises contain erectile tissue much like our own. It gets stiffer if it’s stimulated, so females could use oral sex to prolong their encounters with males, by maintain their erections or lubricating it for easier entry.

While many of us might nod sagely at the need for longer sex, Tan suggests that for the bats, it could mean easier transport of sperm to the oviduct, or more secretions from the female that are conducive to fertilisation. It could also be a way of hogging a mate, keeping him away from rival females.

Alternatively, the antiseptic properties of saliva might help to strip the male’s penis of bacteria or fungi, and prevent the spread of sexually transmitted diseases. The fact that males lick their own penises after sex supports this idea.  

And finally, oral sex might help females to pick up chemical traces on her mate that might suggest if he’s a suitable mate. Obviously, they’d already be having sex, but female mammals often exert choice over their sexual partners after the fact, rejecting sperm from inferior males, or encouraging congress with superior ones to displace it. All of these explanations are just hypotheses for the moment, but they could all be tested in the future.

Reference: Tan, M., Jones, G., Zhu, G., Ye, J., Hong, T., Zhou, S., Zhang, S., & Zhang, L. (2009). Fellatio by Fruit Bats Prolongs Copulation Time PLoS ONE, 4 (10) DOI: 10.1371/journal.pone.0007595

More on animal sex:  

 


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Comments

  1. #1 Russell
    October 27, 2009

    While many of us might nod sagely at the need for longer sex, Tan suggests that for the bats, it could mean easier transport of sperm to the oviduct..

    Tan is falling into the fallacy that animals have sex for the purpose of procreation. Or of writing as if. Those bats are having sex because they’re horny, and the fellatio is somehow making their sex more satisfying. That might or might not enhance reproduction. But that is not on the little bats’ minds when they’re busy getting it on.

  2. #2 SJohn
    October 27, 2009

    Me thought dolphins did not only oral sex but blow hole sex too! (punning this is way too easy)

  3. #3 The Science Pundit
    October 27, 2009

    Do you mean that BJ stands for bat jowl?

  4. #4 Captain Skellett
    October 27, 2009

    SJohn: Blow hole sex – a whole new meaning for the word blow job.

    Bats are the Fonz. Love it.

  5. #5 frog
    October 27, 2009

    aside from the anthropocentric conclusion of ‘pleasure-giving’.

    Are you nuts? That’s not anthropocentric — every other explanation is, instead. The bats aren’t making direct computations of relative reproductive success — they’re “feeling good”, and very often “feeling good” is made better by making someone else “feel good” (not assuming that the bats can actually model their partners mind like that).

    Humans have sex for reproductive purposes — I would bet we’re the only ones who are that insane. Everyone else just does what they like to do.

    This is like saying that animal X eats to keep their metabolism going — only a few crazy people do that. Everyone eats because they like eating.

  6. #6 Briana
    October 27, 2009

    Its ridiculous to talk about animal sex like it is fundamentally different than human sex when the behavior is the same. It is like saying that animals drink sugar water just because it gives them a boost of calories so they can better evade predators, while humans do it just because sugar is tasty. I bet that animal thinks sugar is tasty, too.

  7. #7 Christina
    October 27, 2009

    The bats aren’t making direct computations of relative reproductive success — they’re “feeling good”, and very often “feeling good” is made better by making someone else “feel good” (not assuming that the bats can actually model their partners mind like that).

    This is true. However, what “feels good” is determined by evolutionary processes, which in turn are shaped by what makes reproduction more successful. If this oral sex didn’t improve reproductive success in some way, it wouldn’t've been selected for.

    So, yes, on the level of the individual animal, they are not making cold-blooded calculations of reproductive success. But such factors do determine what feels good

    However, I do feel that there is too much emphasis on the actual sex act. I think Joan Roughgarden made some good points in Evolution’s Rainbow, for example, about sexual activities often having purposes beyond simple fertilization, such as forming bonds between packmates and the like. For example, oral sex may be a way of strengthening the male-female bond. The female could be giving her mate oral sex in order to strengthen their bond, and ensure that she has a more secure place in his harem (assuming that the females have some choice in the matter). For the male, it would be beneficial to find fellatio pleasurable, as it would ensure that he would be bonded with a female who intends to remain with him, while from the female’s perspective, giving fellatio is presumably pleasurable for the same reason – to strengthen her position in the male’s harem. This is just one possibility. Knowing nothing about the bats beyond this article, I can only speculate about what possible advantages there might be.

  8. #8 MariaA
    October 28, 2009

    ” In fact, we know of only animal apart from humans to regularly engage in fellatio”

    Um, ever heard of bonobos? Our close relatives? yeah, those.

  9. #9 Gunnar
    October 28, 2009

    Oh, how much easier it would be to popularise biology if people were taught the difference between ultimate and proximated causes earlier. On the level of genes (and thus evolution), sex is mainly for procreational purposes. On the level of the individual (at least among mammals, probably also among many other animals), sex is mainly fun.

    If we view the oral sex in these bats as an evolved behaviour, we must look at it as helpful in reproduction. If it is a cultural feat, it may or may not be. These students should look at bats from other populations of the same species; maybe even making transplants of females.

    I am not sure whether the pair-bonding effect of sex is subject to selection in the same way the recreational effect is; Wouldn’t it be far too easy to evolve misleading signals? Oral sex is not necessarily a pair-bonding activity; if it indeed has direct effects on reproductive output we have no grounds to assume that it does have. Also, in evolutionary logic, there is no reason for a harem-male to care whether the pairing is stable; if he is able to attract females to mate with him without supplying parental care, that is exactly what he should care about – regardless of whether the females stay faithful or not, his genes will make up a significant part of the next generation.

    On a quite different note; Calvin & Hobbes (1989) presented a convincing case once that bats are insects.

  10. #10 Kapitano
    October 28, 2009

    1) If female fruitbats give oral sex because they like it – in the same way that humans do – you’d expect to see some lady fruitbats doing it a lot, some not at all, and others gaining a taste for it over time. Is this what we see?

    2) If fruitbat sex is partly recreational, you’d expect to sometimes see homosexual sex among fruitbats – and indeed group sex. Is this what we see?

    3) We’d also see sex that is purely oral – all tongue, no penetration. Do we see this?

    I don’t know the answers – I’m just asking.

  11. #11 brooks
    October 28, 2009

    frog:

    Are you nuts? That’s not anthropocentric — every other explanation is, instead. The bats aren’t making direct computations of relative reproductive success — they’re “feeling good”, and very often “feeling good” is made better by making someone else “feel good” (not assuming that the bats can actually model their partners mind like that).

    you’re missing the point– an anthropocentric consideration of ‘pleasure-giving’ means modeling one’s partners mind to figure out what makes them feel good, and that’s exactly what ed is saying they’re not doing.

    MariaA:

    Um, ever heard of bonobos? Our close relatives? yeah, those.

    ever heard of RTFA? fifth paragraph? yeah, that one. jeez.

  12. #12 piratebrido
    October 28, 2009

    “Fruit bat sex goes like this: the female approaches and sniffs the male, and both partners start to lick one another. The male makes approaches with his thumbs (like the Fonz) and mounts the female (like the Fonz). Sex itself is the typical rhythmic thrusting that we’re used to, and afterwards, the male licks his own penis for several seconds.”

    If only, eh lads!

    Lads..?

  13. #13 Dennis
    October 30, 2009

    Join us in promoting this paper for the Ig Nobel 2010 Prize in Biology!

    http://www.facebook.com/home.php#/group.php?gid=171824655811&ref=nf

  14. #14 Bjørn Østman
    November 2, 2009

    @1: Tan is falling into the fallacy that animals have sex for the purpose of procreation. Or of writing as if. Those bats are having sex because they’re horny, and the fellatio is somehow making their sex more satisfying. That might or might not enhance reproduction. But that is not on the little bats’ minds when they’re busy getting it on.

    In fact, this is not a bad hypothesis. It can be applied to all forms of sex (e.g. homosexual behavior): Humans and other animals don’t have an instinct to procreate, but an instinct to have sex. This is not the same thing, but it clearly works quite well anyway. Instinct tells males to ejaculate because that is the way to impregnate. That it doesn’t always impregnate only means that it’s not a perfect instinct. Masturbation and other sexual behavior that leaves sperm far from the egg can be explained this way.

  15. #15 Marc Abian
    November 3, 2009

    Eeeeeeeeeeeeeehhhhhhhhhhhh

  16. #16 Johan
    November 5, 2009

    Min Tan of China’s Guangdong Entomological Institute (who are either branching out, or are confused about entomology).

    :D

    //JJ

  17. #17 David Dobbs
    November 5, 2009

    I just read this article for the article.

  18. #18 Andreas Kyriacou
    November 8, 2009

    At last we have a partial answer to Thomas Nagel’s old question «what’s it like to be a bat?».