Image: Charles Sharp, Wikimedia Commons

A new study shows that monkeys are capable of both robbing and bartering with humans.

Macaques living near the Uluwatu Temple on the Island of Bali have developed a habit of stealing from tourists and bartering items back for food.

Fany Brotcorne, a primatologist at the University of Liège in Belgium, set out to determine the evidence behind reported observations of these unusual events. She studied the groups of monkeys that lived around the temple for four months and witnessed the thievery firsthand on many occasions.

Brotcorne concluded that the exceedingly social monkeys were the most prone to stealing, especially groups with a predominant population of young males.

These monkeys excel at swiping valuable items from tourists, including sunglasses, hats, and cameras. They then proceed to hold the items ransom until temple staff offers them a trade in the form of food.

Image: Shankar S., Flickr

Long-tailed macaques are opportunistic feeders that take advantage of their proximity to humans and commonly consume human waste, although their diets in the wild consist of fruit, small birds, eggs, and lizards. The desire for food is the predominant driving factor behind the encounters.

Brotcorne speculates this thieving and bartering behavior is a cultural one, and is transmitted down through generations.

This insight into the psychology of primates serves as a stepping stone for understanding the evolution of cognition.

Brotcorne stated to New Scientist, “Bartering and trading skills are not well known in animals. They are usually defined as exclusive to humans.”

Further research into this phenomenon will lead to a better understanding of learned animal behavior, as it is found no where else in the world.

The full study is published in Primates.