Some of you may be familiar with the long-tailed monkey crime ring who reside around the Uluwatu Temple in Bali, Indonesia, who were thrown into infamy a few years ago for stealing from tourists and insuring the ransom until they were paid for in food. As if the look weren’t mind-boggling enough, a new study found that some of the monkeys intentionally steal items that are most valued by humans for the best reward.
Conducted by researchers at Lethbridge University in Canada and Udayana University in Indonesia, the study found that monkeys performed “unprecedented economic decision-making processes” when they stole things and kept them for rescue. The researchers said that this practice – which has also been analyzed in similar studies with monkeys in captivity in the laboratory – is specific to the population, prevalent, intergenerational, learned and socially influenced. It may be the first example of a symbolic economy maintained culturally in wild animals, they wrote.
The study was published last week in Philosophical transactions of the Royal Society B Diary.
However, not all monkeys steal at the same level. The researchers found that age plays a role in this process, with older monkeys stealing items that are most valued by humans. (The study literally referred to adult monkeys as “the most skilled thieves”.)
G / O Media can receive a commission
“[T]he is more skilled [sic] and selective individuals seemed to make economic decisions, as evidenced by clear behavioral associations between symbolic possession based on value and quantity or quality of rejected and accepted food rewards, ”wrote the authors.
To get to the bottom of this monkey business, the researchers analyzed 333 free monkeys for 273 days from September 2015 to August 2016. An additional set of 15 monkeys was analyzed in December 2019. Observational data was collected by video recording of the monkeys that looked for possible human targets and reached about 16 feet from them (five meters). Human targets were defined as visitors to the temple wearing or carrying at least one non-edible object that was “more or less likely” to be exchanged for food if stolen, according to the study.
He grouped the types of tokens targeted by monkeys into six groups: empty containers (phone cases and camera bags); accessories (hairpins and key rings); hats (headgear and caps); shoes (flip flops, heeled sandals); glasses (glasses and sunglasses); and electronic devices and wallets (cell phones, cameras and bags). The researchers then classified these items into groups of low-value tokens, medium-value tokens, and high-value tokens, according to how often humans wanted to trade with monkeys.
Low-value tokens, such as empty containers and accessories, were rarely exchanged for humans, the study found. Medium-value tokens, such as hats and shoes, were frequently exchanged. While high-value tokens, such as glasses, electronic devices and wallets, were almost always exchanged for humans.
Let’s go back to the era. According to the study, monkeys were much more likely to steal a coveted item the older they were. Sub-adult monkeys were more successful than juveniles, while adults were more successful than sub-adults and juveniles. But it is one thing to steal something, another thing to negotiate and be rewarded for it. In this respect, adults and sub-adults once again came out first, while juveniles were last.
With age comes wisdom, or more specifically, in this case, the ability to differentiate between low, medium and high value tokens. The study found that young monkeys didn’t really care about the types of objects they could get their hands on, but that sub-adult monkeys and adults preferred high-value to low-value, or medium-value tokens to low-value tokens.
Finally, the researchers decided to take a look at the “most skilled [sic] and selective individuals ”, or the sub-adult and adult monkeys. In terms of quantity, both groups of monkeys waited to receive more food rewards before returning the item when they considered it to be of high value. Adult monkeys were even more demanding when it came to quality and rejected more of their less preferred types of food rewards when holding an item of higher value.
Talk about being a tough negotiator.
Dr. Jean-Baptiste Leca, the study’s lead author and associate professor of psychology at the University of Lethbridge, said the Guardian that stealing and trading is an expression of the apes’ cultural intelligence.
“These behaviors are socially learned and have been maintained by generations of monkeys for at least 30 years in this population,” he said.
In the end, this study was a fascinating look at the brains of these little thieves. It also kind of reminds me of something a crime network would do on a Netflix show. I would watch.