Monkeys on the island of Bali grift hard to get their supper. Researchers have found that light-fingered macaques at one of the most popular temples on the island have learned to steal tourists' possessions, and then barter with them for food before giving them back.
The criminal underworld of long-tailed macaques is seemingly very fruitful – with some of the best purloiners holding their ill-gotten goods to ransom until they are offered only the choice bits of fruit – yet only some populations display this robbing and bartering behavior, leading the researchers to ask whether or not it is a cultural activity.
People have noted before how the tricksy monkey muggers have learned to steal valuable items and then trade them back for food, but it has never been scientifically studied before. Researchers wanted to get a more in-depth view of exactly what was going on, who were the main perpetrators, and how it spread through the monkey population. They spent four months observing the four resident groups of monkeys that lived in and around the Uluwatu Temple on Bali.
Despite other places on Bali having groups of macaques coming into frequent contact with tourists, offering ripe opportunity for extortion, it is only those in the Uluwatu Temple that seem to have figured it out. This suggests that the robbing and bartering behavior is learned, rather than innate. But what the researchers were really interested in was finding out whether or not it was cultural, publishing their results in the journal Primates.
In over half of the cases, monkeys were most likely to make off with a pair of glasses, followed by hats 12.4 percent of the time and – rather curiously – shoes in close to 12 percent of cases.
They found that the two groups that lived in the areas of the temple most popular with visitors had the lightest fingers, displaying the most expertise when holding up tourists, while those further away engaged less often. Not only that, but they also found the groups containing the most adult males also harbored the most criminals, suggesting that there is a sex and demographic bias in the behavior.
Interestingly they did not find that the larger the group, the more likely members would thieve. The researchers thought that bigger groups would mean that there is more of an opportunity that young macaques will see older ones stealing, and thus the behavior would spread more rapidly and be more prevalent. It seems that robbing and bartering is likely passed between males in the groups.
While the results are just a preliminary study, due to the small data set used, the researchers think that the monkeys probably are displaying a new cultural behavior, limited to the groups surrounding Uluwatu Temple, and passed on from individual to induvial.
It's no wonder this one is looking a little tubby, he knows his game well.