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Bali’s Thieving Monkeys Know Your Smartphone Is Valuable, Study Finds

By observing interactions at the Uluwatu temple in Bali, researchers found that the macaques have learnt to steal only high-valued items from tourists in exchange for food.
bali monkeys temple
Photo: Kutan Ural, courtesy of Unsplash

Last year, the monkeys of Indonesia made news globally for their baby-stealing antics. But while that was only a case of “street entertainment gone wrong”, it turns out the country does have some monkeys skilled at stealing things. Long-tailed macaques at a popular temple in Bali are known to frequent the tourist site, looking to snatch away possessions of visitors and refusing to return them unless offered food as ransom. 


Now, a study has found that this might be a calculated move by the monkeys to only steal items they’ve determined to be particularly valuable to the tourists, in order to maximise their own gain. 

Researchers from the University of Lethbridge, Canada, and Udayana University, Indonesia, studied the behaviour of monkeys at Bali’s Uluwatu Temple. They found that these monkeys are more likely to go after articles that tourists value and are more likely to exchange for food, such as electronics, and ignore knick-knacks of low value, like hairpins. Skilled at judging which objects are likely to fetch them greater returns, the monkeys mostly tend to go for mobile phones, wallets or purses, cameras, tablets, and prescription glasses, among other items dear to visitors. 

The research, published in the Royal Society Journal, was conducted over 273 days from 2015 to 2016, with further observations conducted in 2019. The researchers filmed over 2,000 interactions between unsuspecting visitors and the brazen monkeys, who could be observed demanding higher ransom for higher-valued items. 

Often, temple staff would have to intervene and negotiate a barter between the visitors and the monkey robbers in proceedings that’d last several minutes. The longest it took to get an item back was 25 minutes, involving 17 long minutes of negotiation with the monkey. For lower-valued items, the monkeys would concede faster and accept a lesser reward. By observing their preference for the incentives temple staff offered to the tourists who wanted their stuff back, scientists identified the relative values of food rewards for the monkeys: raw eggs, bags of fruit and crackers.


“These monkeys have become experts at snatching them from absent-minded tourists who didn’t listen to the temple staff’s recommendations to keep all valuables inside zipped handbags firmly tied around their necks and backs,” Dr Jean-Baptiste Leca, an associate professor in the psychology department at the University of Lethbridge and lead author of the study, told The Guardian.

Unlike many previous studies that have examined similar behaviour, the macaques at the Hindu temple are free-ranging animals and were studied in their natural habitat, not in a laboratory setting. 

Such behaviours are learned by the monkeys throughout their childhood until they are four years old, according to the research, which was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Alberta Gambling Research Institute (AGRI).

These observations hint towards a deeper understanding of economics that the monkeys have socially acquired over time. “Token-robbing and token/reward-bartering are cognitively challenging tasks for the Uluwatu macaques that revealed unprecedented economic decision-making processes,” the authors told CNN.

“This spontaneous, population-specific, prevalent, cross-generational, learned and socially influenced practice may be the first example of a culturally maintained token economy in free-ranging animals.”


However, these monkeys are not the only ones posing trouble for locals and tourists alike. The monkey “mafia” of the Hindu temple town of Vrindavan in north India are known for similar behaviour, wherein they snatch away visitors’ possessions, sometimes violently, and demand specific food items such as fruit juice in exchange, with locals having to step in and negotiate a barter. India has also suffered much more serious damage at the hands of monkeys, who stole blood samples of COVID-suspected patients from a laboratory in the Indian city of Lucknow, raising fears of further spread of the virus if they mishandled them.

Macaques are also known to wreak havoc in many other parts of South and Southeast Asia. These human-monkey conflicts have piqued the interest of many scientists in the past, who have not only observed these interactions closely, but also ways in which to best communicate with monkeys in locations such as Sri Lanka where monkeys are increasingly becoming a pain, as they raid villagers’ kitchens and rummage through their garbage bins on the daily. Like most other things, this elevation of the human-monkey conflict can also be blamed upon humans themselves. 

In communities where Hindu mythology is popular, monkeys are seen by many as representing the Hindu deity Hanuman, and thus carry a cultural and religious significance not enjoyed by most other species of wildlife. Many tourist sites see people leaving behind food for these primates. But these acts of faith might be leading to an increase in primate infiltration of areas inhabited by humans, thus giving rise to increased human-monkey conflicts.

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