Animals Masturbate Too- And Why That Matters

Juvenile rhesus macaque at the Beijing zoo. (Not Peanut.) Source.

Juvenile rhesus macaque at the Beijing zoo.  Source.

I have had my leg humped by a very small monkey named Peanut.

Peanut herself did not think that this was anything out of the ordinary; in fact, as she enthusiastically gyrated on my thigh, she kept glancing backwards to meet my eyes, her little face arranged in what seemed to be a contented expression.

At the time, Peanut and her companions at the rhesus macaque nursery I volunteered at were all less than three months old. They were just beginning to develop more complex behaviors than the scream-eat-poop trifecta (not that those three were any less present). The males were beginning to manipulate their own penises, and both sexes would frequently engage in enthusiastic humping sessions with objects and other monkeys. The other monkeys weren’t always thrilled about this.

I suppose this would make you imagine that the nursery just became a masturbatory frenzy at this point, but that really wasn’t the case. The vast majority of the time wasn’t spent in sexual exploration but in actual exploration, of their home spaces, of toys, of social behaviors like grooming, playing, and fighting.

I guess where I’m going with this is that when many humans are confronted with the idea of animal sex, they tend to fly to extremes: either animals are sex purists and only have it with the intent of reproduction (and NEVER use contraception!) or animals are hedonistic, lustful creatures that will spend every moment that they can touching themselves.

I think that this is because admitting that sexual behaviors- reproductive or not- make up a small but important part of an animal’s life is somehow more uncomfortable than either of those options. Perhaps it just hits a little too close to home.

But, as the title states, I am about to argue about why the study of animal masturbation (and other aspects of animal sex) is important. It matters. It matters for the ethical treatment of animals, it matters for conservation, and it matters because the study of something shouldn’t be limited by the fact that many people want to pretend that it never happens.


Why are people so freaked out by animals having sex?

Well, there’s obviously the cultural aspect- and I have to admit here that I can only speak for the more Western part of society; I can’t speak much on the attitudes of other cultures (though I do find the effects of the Japanese depictions of the tanuki and its giant testicles hilarious on Western viewers).

I'd be startled by this sight too. (Side note, I actually couldn't find a picture of actual tanuki balls for comparison.)

I’d be startled by this sight too. (Side note, I actually couldn’t find a picture of actual tanuki balls for comparison. And yes, I looked…)

You could argue that here in the west, we have a cloistered view of sex. It’s generally agreed upon that it is a private act, used for reproduction. We also seem to agree that it is sometimes- perhaps more often than sometimes- an act done for pleasure.

People just seem to get really squirmy when you put forth the idea that animals also experience pleasure during sex, which leads them to do things like masturbating or performing sexual acts with others that in no way whatsoever will ever lead to reproduction.

My theory on why this is is that most people aren’t used to thinking about sex in a non-sexual way. All right, I know that’s one hell of a sentence, but hear me out.

I think in a lot of ways, people thinking about animals having sex is like people thinking about their parents having sex: ick, no way, please not that mental image! But why such an immediate aversive response? I think it’s because both our parents and animals are things we adamantly do not want to view in a sexual way; therefore we try not to associate sex with them at all.

I think that this is actually kind of a problem. No, not that I want people attracted to their parents or animals, absolutely not. But the fact that we can only think about sex if it involves something we are sexually attracted to is very worrying.

And guys: I hate to say it, but chances are, your biological parents did have sex. Sorry. It’s really okay.

And this mindset leads to another issue: the suspicion directed towards those who study sex in science. You study animal sex? What, like, do you wanna screw animals?

This isn’t just limited to those who study animal sex, mind you; it’s directed towards those who study human sex in a major way, though thankfully it’s gotten better over the years. Those of you who have seen the movie Kinsey will have seen a depiction of the prejudice and difficulty the earliest sex researchers faced.

But at least the study of human sex relates back to humans. People have a much harder time understanding why you would ever find it necessary to ask for a research grant to study oral sex in fruit bats.

But it is necessary.

Jerking It At The Zoo, and other ethical considerations

Primatologists will tell you that there’s a reason bonobos aren’t displayed in zoos.

The reason is, of course, that the suite of normal bonobo behavior includes a lot of sexual behavior, including same-sex interactions, sexual interactions between individuals of all different ages and blood relations, et cetera, et cetera. People don’t want to see it and they really don’t want their children seeing it.

However, even sans bonobos, a lot of public sexual behavior occurs in zoo animals, even those that aren’t provided opposite-sexed mates. A lot of masturbation occurs too, much to the delight and terror of zoo visitors. (The linked video involves a male walrus and is very nsfw.)

Early scientists just didn’t know what to say about this behavior. Supposedly, pleasuring oneself was a carnal human act, not an act of animals that instinctually obeyed Darwinistic laws of survival of the fittest. Most of the scientists in the 50s and 60s didn’t even believe that animals could feel pleasure.

This confusion and discomfort led- and still leads- to animal owners punishing their animals for displaying masturbatory behaviors.

Horses are a good example of this. Stallions are known to masturbate by rubbing or bouncing their erect penis against their own abdomen (though it is rarely done to ejaculation) while mares are known to rub their genitals on objects like posts.

Diagram of typical stallion masturbatory behaviors.

Diagram of typical stallion masturbatory behaviors.

When people saw their stallions masturbating, their response was startlingly brutal:

Commercially available or custom-made equine anti-masturbatory devices that have been developed and used for decades include constricting bands (made of metal, plastic, or fabric) known as “stallion rings,” abrasive devices such as a nail patch or stiff bristled brush applied to the ventral midline at the point of belly contact during masturbation, metal or fabric constricting “cages” or “baskets” applied to the prepuce or glans penis, and electronic shock collars, or girth straps similar to dog-training collars…

Simple physical punishment, for example, striking the belly, penis, or hind legs of the stallion with a riding crop or whip, is a fairly common technique employed to interrupt SEAM. More elaborate punishment schemes employed by horsemen to eliminate SEAM that have been reported anecdotally include abrading and lacerating the penis before applying caustic topical preparations, and severely beating the erect penis with blunt or sharp objects resulting in trauma. (McDonnell & Hinze, 2005)

What warranted such a violent response to this behavior? I’ve read that some believed that masturbation would reduce a stallion’s virility, that it would reduce a stallion’s athletic fitness, that it was a stable vice (stereotypy), that it would somehow lead to homosexual behaviors…

Aside from the fact that none of these things are true, at least one study has shown that using aversive conditioning to try to stop a stallion from masturbating actually suppresses their sexual arousal and breeding ability with a dummy mount- and also doesn’t reduce masturbatory behavior at all.

And yet the idea that stallions should be stopped from masturbating still persists among some horse owners today. And it’s not because there’s any truth to the claims that it somehow causes infertility. It’s because they find the behavior embarrassing. And because they find it embarrassing, they punish the horse.

This is a major reason why research on animal masturbation is important: because it can stop attitudes like this that lead to animal cruelty.

I think (I hope) that most people can agree that punishing an animal for masturbating is wrong, but what about addressing the reason why an animal masturbates? I mentioned earlier that some people think that masturbating is a stable vice or stereotypic behavior, meaning a repetitive behavior that is performed out of stress or frustration. Stereotypies usually come about in captive animals that are restricted from performing their normative behaviors.

Do stallions masturbate because they are frustrated and understimulated in captivity?

Well, given that research has shown that feral horses masturbate with about the same frequency that domestic horses do… probably not. (That frequency? About ten times a day.) Wild equids such as zebras and wild asses also show the same patterns. Essentially, no, masturbation is not a stable vice or stereotypy, at least in horses. It’s actually normal, natural behavior.

So why is masturbation a normal behavior in wild equids? Or wild animals in general?

This is an interesting question that unfortunately also gets obscured by a squeamish mentality. People have come up with all sorts of reasons to explain why animals masturbate other than “they just like it.” My favorite- by which I mean my absolute least favorite- is the “dog humping equals dominance” theory.

I’m not going to go into the serious problems with the popular view of dog “dominance” in this article- that’s a later topic. But let it be known that it is problematic in a big way.

Mounting and humping is part of that. I walk dogs as a part-time job and boy do I cringe every time I hear an owner explain to me that “Fifi’s dominant over Fido, so she mounts him.” The problem with this is that there is actually very little evidence that mounting in canines has anything at all do with a rank in a dominance hierarchy. Believe me, I’ve scoured what’s available.

Both male and female dogs are known to mount other dogs regardless of their partners’ sex or social rank. In one study, females actually performed 55% of the mounts recorded, but it seems as though most studies record more mounts by males than females. Object mounting and thrusting is also common in both sexes, fixed or not; I dogsit a spayed dog who has her own special stuffed animal that she mounts periodically. It is less common in male dogs that are neutered than in intact males.

Mounting in dogs seems to occur mainly in three contexts: first, during play; second, during times of heightened excitement; and finally, without apparent cause. Play and excitement mounting are probably quite similar- the direction of the dog’s energy simply turns sexual for a moment. In one study researchers found that puppies viewing two other puppies play-fighting would often go up and mount whoever was on top, a particularly interesting finding considering that in the same study most playful-aggressive behaviors from a third party were directed towards the puppy on the bottom (i.e., the more submissive-looking one).

Mounting also seems to occur as a redirection of energy or frustration- when told “no” for some other behavior, a dog may start humping something.

When a dog starts mounting something or somebody without any apparent cause or excitement, it’s probably just plain old masturbation. A handbook for veterinarians on behavior problems of dogs and cats advises this for both species:

For masturbation and mounting of other pets, the behavior may be allowed to continue if it is doing no harm or the pet directed to an alternative acceptable outlet. (Landsberg et al., 2012)

In other words, there’s a veterinarian’s seal of approval that masturbation is normal in both dogs and cats. I wish there was more research available on it, but there you go.

Jerking It In The Wild, or why masturbatory behaviors exist

Masturbation is found in almost every family of mammals and in a few non-mammalian species as well, like turtles, cockatiels, and penguins. (I spoke of the rock-humping penguins in an earlier article, and yes those two links are NSFW.)

Again, it’s not as if it’s hyper-prevalent. Those of us with our own pets know that they aren’t constantly going hump-crazy; many animals never appear to masturbate at all (same goes for some people). But it happens, and it’s being seen more and more in studies of animals in the wild as well as in captivity.

The question for decent scientists is, then, what purpose does this behavior serve? Essentially any behavior exists because it evolved, and most behaviors become fixed in a species due to a biological advantage that they infer. That’s basic evolutionary theory.

The simplest explanation for why animals masturbate is what I like to call the orchid wasp theory. Male thynnid wasps are regularly found masturbating on top of certain orchid species. There is a specific reason for this, however: the orchids mimic the look and shape of a female wasp to trick males into mating with them and thereby pollinate them.

Fly orchid. (Photo by Ann Mead.)

Fly orchid. (Photo by Ann Mead.)

The orchid masturbating causes a loss of sperm and energy for the wasp and in general is a behavior that it would be evolutionarily salient to throw out the window. Yet the wasps haven’t lost it. Why? Because the more discriminating they end up being with the flowers, the more discriminating they end up being with the ladies. The wasp that passes over flowers as well as females is worse off in terms of reproductive success than the wasp that fucks everything it can find (hopefully lots of ladies included).

Animal masturbation could simply be an extension of this: better to have a couple of misfires than miss the boat altogether. And in many species this does seem to be true: in penguins that mount rocks (and dead individuals of their own species), the mounting seems a result of a fixed action pattern: penguin sees something that vaguely resembles a female penguin’s butt, penguin flies into a frenzy of lust.

But this explanation doesn’t really account for everything. For starters, much of animal masturbation occurs in contexts that are pretty clearly not going to get them laid. Animals frequently masturbate with their paws, mouths, and anything available (like a stick or a beheaded fish).

This type of masturbation might be explained (at least for males) by the fact that there is some evidence that frequent ejaculation helps get rid of older and hence less fertile sperm. There’s positive support for this idea in species such as crickets (male crickets seem to spontaneously deposit old sperm packets). There’s also some evidence that this comes into play in primate species who masturbate (including humans), but this is slightly controversial.

In male African ground squirrels, which tend to masturbate soon after copulating with females, the masturbation seems to function as a way to clean out their urethra (they lick the head of their penis as well) to prevent sexually transmitted diseases.

You may notice that something is missing from this sad little list of theories I have gathered: namely, females. None of these theories explain why female animals masturbate- which they do, often in creative ways. I can think of two reasons for this: one, female masturbation may be harder to observe given that they don’t have a massive erect phallus to swing around (usually- spotted hyenas are an exception). Two, if male animal masturbation is gross and funny to the western mind, female animal masturbation is, uh…

You know, folks, it really does happen.

Unfortunately, I have yet to find any research on masturbation in female animals. (There also isn’t much on masturbation in female humans! Whereas you could fill oceans with the sperm of male masturbation study participants.)

But frankly speaking, if we can argue that there are evolutionary reasons why male animals masturbate, we should do the same for females.

In summation: masturbation is a normal behavior in many animal species in many different animal families. Studying when it is normal and when it is an indication of stress can help animals in captivity. Studying how it increases reproductive fitness can help in the conservation of animals in the wild.

But I also think that if this behavior and other types of nonreproductive sexual behaviors get their time in the sun, we can get over our childish refusal to acknowledge that they exist. That doesn’t help anyone.

I also would like a lot of my colleagues in the science community to get over the notion that animals don’t experience sexual pleasure. I suspect that not all masturbatory behaviors will be explainable by some reproductive benefit. And I think that’s just fine.

More study is needed.

Read on: I’ve written quite a bit on animal sexual behavior. For information on female monkeys who take two male mates at a time, check out polyandrous chimeric monkeysFor examples and explainations of why same-sex sexual behaviors occur in birds, check out my post on bird yaoi (and bird yuri). To learn about why ridiculous sexual displays evolve, toddle over to my article on chase-away sexual selection. And for the things that sometimes happen after sex, have a look at my posts on how coots make terrible parents but cowbirds make awesome (if terrifying) ones.

References and Further Reading

Dubuc, C., Coyne, S. P., & Maestripieri, D. (2013). Effect of Mating Activity and Dominance Rank on Male Masturbation Among Free‐Ranging Male Rhesus Macaques. Ethology119(11), 1006-1013.

Landsberg, G. M., Hunthausen, W. L., & Ackerman, L. J. (2012). Behavior Problems of the Dog and Cat. Elsevier Health Sciences.

McDonnell, S. M., & Hinze, A. L. (2005). Aversive conditioning of periodic spontaneous erection adversely affects sexual behavior and semen in stallions. Animal reproduction science89(1), 77-92.

McDonnell, S. M. (2000). Reproductive behavior of stallions and mares: comparison of free-running and domestic in-hand breeding. Animal reproduction science60, 211-219.

McDonnell, S. M., Henry, M., & Bristol, F. (1991). Spontaneous erection and masturbation in equids. J. Repro. Fert.(Suppl.)44, 664-665.

Perumal, P., Vupru, K., Khate, K., Veeraselvam, M., Verma, A. K., Nahak, A. K., & Rajkhowa, C. (2013). Spontaneous Erection and Masturbation in Mithun (Bos frontalis) Bulls. International journal of Bio-resource and Stress Management4(4), 645-647.

Reinhardt, K., & Siva‐Jothy, M. T. (2005). An advantage for young sperm in the house cricket Acheta domesticus. The American Naturalist165(6), 718-723.

Russell, D. G., Sladen, W. J., & Ainley, D. G. (2012). Dr. George Murray Levick (1876–1956): unpublished notes on the sexual habits of the Adélie penguin. Polar Record, 48(04), 387-393.

Schiestl, F. P., Peakall, R., Mant, J. G., Ibarra, F., Schulz, C., Franke, S., & Francke, W. (2003). The chemistry of sexual deception in an orchid-wasp pollination system. Science302(5644), 437-438.

Ward, C., Trisko, R., & Smuts, B. B. (2009). Third-party interventions in dyadic play between littermates of domestic dogs, Canis lupus familiaris. Animal Behaviour78(5), 1153-1160.

Waterman, J. M. (2010). The adaptive function of masturbation in a promiscuous African ground squirrel. PloS one5(9), e13060.

About Koryos

Writer, ethology enthusiast, axolotl herder. Might possibly just be a Lasiurus cinereus that types with its thumbs.
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