Dirty Monkey Business: Macaques Learn to Use Stones as Sex Toys

  • We’re not sure if this news is surprising or something we totally should’ve expected.

Those monkeys are up to something. There have been strangely many stories popping up lately about macaques.

In Japan, the authorities recently executed a macaque that had been attacking people. But in Indonesia, the macaques are… Well, doing something completely different.

There’s no tactful way to put this so we’ll just be blunt. The macaques are masturbating — with sex toys.

In a recent study, published in the journal Ethology, researchers observed groups of long-tailed macaques in Bali’s Sacred Monkey Forest. They noticed that the monkeys were using stones on their genitals.

Puzzled by the behavior, the scientists tried to figure out if there was some kind of deeper reason for it. But as it turns out, the most likely explanation is that it just makes the monkeys feel good.

On one hand, it’s common knowledge that some monkeys can use primitive tools. On the other, we didn’t really expect them to…

Oh, who are we kidding? Our ancestors probably did the exact same thing as soon as they learned to pick up a stone.

Pictures: The face of a macaque discovering a new use for stones.

Spanking the Monkey

But let’s take a step back and establish what the macaques are actually doing with the stones. By the way, we will talk about monkey genitalia, so you might want to stop reading here if that makes you uncomfortable.

Still with us? Alright, let’s get dirty.

So, the researchers gathered their data — mostly in the form of video — between 2016 and 2019. They observed many instances of monkeys playing with stones of various sizes.

Sometimes, the activity was clearly just play or mental stimulation. The macaques would gather piles of stones, clack them together, throw them around, stick them in their mouths, and whatever other things you’d expect them to do with a bunch of rocks.

But then there was the… Other behavior.

The researchers noticed that both the male and female macaques had a habit of rubbing or tapping stones on their genitals. With the male monkeys, it was pretty obvious what was going on.

According to the study, the male macaques would rub their dongs with stones more often and for a longer time if they also had an erection. Clearly, they were spanking the monkey.

But with the females, things weren’t quite so clear-cut.

“For females, it’s a little bit harder because we don’t really have an easy signifier of arousal,” Camilla Cenni, the study’s lead author and Ph.D. candidate at the University of Lethbridge, Canada, told Vice.

However, the females were weirdly picky about which stones received the honor of caressing their lady parts. They seemed to prefer stones with a grainy texture or ones with prominent edges.

You can probably imagine why that might be. Naughty, naughty.

Creativity from Boredom

It’s not unusual to see macaques using or playing with stones. For example, Japanese macaques do it very commonly, as do the ones in Bali.

Masturbation isn’t a rare phenomenon, either. Many primates do it, from macaques to chimpanzees and — yes — Homo sapiens like you and me.

But seeing macaques put two and two together and use stone tools for masturbation is a rare sight to behold. How could they have learned this behavior?

One explanation could be that the macaques are simply so bored that they discovered sex toys.

Cenni’s team and other researchers have noted that macaques living near humans are more likely to play with stones. The reason for that is that they can get plenty of food, both from visiting tourists and by stealing it from human settlements.

With the abundance of food, the monkeys won’t have to be constantly looking for their next meal. Consequently, they have many hours in the day that they don’t really need to do anything.

“I think we can probably confidently say that the free time they have as a result of provisioning, it’s a big explanation for [playing with stones],” said Cenni.

While messing around with stones, one macaque probably figured out that rubbing them on their genitals feels kind of nice. Throw in some monkey see, monkey do, and soon the whole group knows about the joys of sex toys.

“It’s hard to give a very solid explanation, but it really seems that they do it because it feels good. There is some sort of tactile stimulation from the contact of those stones with their genitals and it feels good. And there is no reason to stop,” summarized Cenni.

It Started with Masturbation

Alright, so we’ve learned that macaques have figured out what sex toys are. What do we do with this revelation?

Well, funny as the thought of a monkey using a stone dildo is, the observation could have significant scientific merit. It may lead to a better understanding of how tool use develops in primates.

It was using tools that helped our predecessors conquer the planet. And (as we joked in the beginning) it’s possible that they, too, once went from stuffing stones in their mouths to sticking them into other orifices on their way to discover more advanced technology.

“Our results support the view that tool use evolves in stages from initially non-functional behaviors, such as object play, through affordance learning,” the researchers note in the study.

In other words, the macaques have learned to use stones for a purpose. Who knows, rubbing a rock on its genitals might just be the first step on the road that leads to a macaque inventing a monkey wrench.

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