In Bali’s sacred monkey forest, food is everywhere and masturbation is rampant.
The thousands of long-tailed macaques living in this hedonistic hotbed are really, really good.
Every day, 10,000 tourists pass through the reserve on their way to three local temples, feeding the monkeys as they go. Park staff also regularly provide the creatures with three meals of fruit and vegetables.
In their little Eden, these monkeys are full, have nothing to worry about, and have plenty of leisure time – self-indulgence is their main game.
In recent years, both male and female macaques have been regularly found rubbing and tapping stones on their genitals, leading scientists to propose the “sex toy” hypothesis.
The hypothesis posits that Balinese macaques are using the stones for self-directed, tool-assisted masturbation, similar to what is seen in chimpanzees, porcupines, dolphins, and us.
Unlike our own species, however, masturbation rarely causes other males to actually ejaculate. This makes it difficult to determine how much fun the monkeys actually get from the stone game.
That said, male macaques did get erections when they rubbed or tapped their genitals with stones, which did not happen when they touched the stones to other parts of their bodies.
What’s more, female macaques are very picky about which shape of rock they choose to please themselves, suggesting that they are choosing the rock best suited for the task at hand, such as one with sharp edges (!) or a grainy texture.
“Therefore,” the researchers concluded, “it can be concluded with confidence that these behaviors were not accidental.”
“Overall,” they add, “our data partially support the ‘sex toy’ hypothesis, suggesting that rocking and rubbing the genital and groin area are sexually motivated behaviors.”
frameborder=”0″ allow=”accelerometer; autoplay; clipboard writing; encrypted media; gyroscope; picture-in-picture “allow fullscreen>
The research is based on video footage of the Sacred Monkey Forest collected by scientists between 2016 and 2019.
The authors collected hundreds of examples of tool-assisted masturbation used by local groups of macaques during this period.
Most monkeys observed rubbing or tapping stones on their genitals were males, although there was no shortage of females to give it a try.
In non-human primates, female masturbation is almost undocumented. This could be due to human bias, or it may be harder to tell when a woman is sexually aroused. or both.
It’s hard to say why Bali’s macaques use rocks to touch themselves, but researchers think the simplest answer may be right: It feels good.
After all, these monkeys have few other pursuits.
“I think we can probably say with confidence that they have free time as a result of the configuration, which is a big explanation [stone play]’ evolutionary ecologist Camila Senny told Vice World News.
“but [free time] Not an adequate explanation,” she added. “I think it’s just part of the story.Another part, it’s hard to be sure because you have to see the first [monkey] doing. “
Long-tailed macaques aren’t the only non-human animals caught using possible “sex toys.”
Some animals even use other animals for sexual gratification. Male and female Japanese macaques were recently photographed jumping and charging hard on the back of a deer.
It also made headlines a few years ago when a male dolphin was caught using dead fish for his own amusement.
Hard, lifeless stones are easier to manage. This is the tool used by macaques. Playing with stones is a regular feature of macaque society and may be a way to practice true foraging or foraging.
Over time, the researchers suspected that this adaptive play was incorporated into a nonfunctional behavior that provided only short-term pleasure.
Now, Bali’s macaques are using their instinctive affinity for rocks for a different type of game. And this one is more interesting.
The study was published in Behaviour: International Journal of Behavioural Biology.