Scientists Prank Monkeys With Fake Poop For Real Research


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

monkey shit

A monkey deciding whether to eat food sitting on some real and fake poop. Sarabian and MacIntosh/Biology Letters

Proving that there really is a job for everyone, scientists at the University of Kyoto have pranked monkeys with plastic made to look like poop, and got a paper published out of it.

PhD student Cecile Sarabian and Dr Andrew MacIntosh report in Biology Letters on what happens when you give monkeys food and put it on top of real and fake feces.


Their study was done on 16 Japanese macaques. Over a series of 151 trials, the two researchers lured one monkey at a time to an area of beach out of the line of sight of the rest of the troop, presumably so no one would know what disgusting things they were about to do. There the monkeys found a toy shop piece of plastic that looked like poop, some actual droppings from another macaque and a brown notebook. Each had either a peanut or a grain of wheat on top of it.

A second experiment dispensed with the feces, real and imitation, and used sweet potato instead – sometimes washed, but sometimes covered in sand.

All the monkeys ate the food placed on the notebook, because why not? In 56 percent of cases they also ate the wheat placed on top of the plastic poop, while 37 percent of the time they were desperate enough to eat wheat placed on real feces. Apparently all those stories about “paying peanuts and getting monkeys" are true, because not once did any of the monkeys pass up a peanut, no matter how disgusting its location. The fact that the plastic poop got a reaction in between the other two suggests that the decision making relies on a mix of sight and smell.

The sweet potatoes were also always eaten, but sometimes the monkeys, particularly the females, took steps to get the sand off them first. The authors connect this to the fact that among many mammals, Japanese macaques included, males are more likely to be infected by internal parasites.


The brave researchers then examined fecal samples from the monkeys to check for parasites. Perhaps unsurprisingly, they found those willing to eat wheat that had been sitting on some other monkey's fecal matter carried a heavier parasite load.

Sarabian and MacIntosh will probably tell you that this was important research about how monkeys respond to the danger of taking in parasites through exposure to feces. And let's face it, they convinced the editors of a highly respected peer-reviewed journal that they were right. But we still wonder whether they weren't just living the dream of all the school children who make up the normal market for plastic that is shaped and colored to gross their elders out.


  • tag
  • parasites,

  • Japanese macaques,

  • primate hygiene,

  • fake poop