For four months, a team of researchers - including Fany Brotcorne from the University of Liège - studied the behavior of a long-tailed macaque population (Macaca fascicularis) living around the Uluwatu temple in Bali (Indonesia ). They quickly identified many cases of robbing / bartering by primates to temple tourists. While the phenomenon of exchange is widely known in captive populations, it has so far been reported only anecdotally in primates in total freedom.

Since 2009, the Research Group in Primatology (Marie-Claude Huynen) of the University of Liège, is interested in the behavioral ecology and the management of the Balinese macaques (Macaca fascicularis) in Indonesia. These wild macaques called "commensals of man" show an extraordinary flexibility in their ecology and behavior. This allows them to survive in highly modified and anthropized environments. The behavior of robbing (of objects) and bartering (in exchange of food) is a striking example of this flexibility. This practice usually occurs in two stages: after srobbing non-edible objects (for example, glasses) from toursits, macaques seem to use them as exchange tokens with the humans to give them back their object in exchange fof food.

As part of her post-doctoral research, Fany Brotcorne focused on these robbing and bartering behaviors that are observed daily in the Uluwatu Temple, but absent in other populations on Bali. The frequency of these practices varies between the four groups of macaques living in the temple. An article, which for the first time describes this behavior in a scientific way, has just been published in the journal Primates(1).

This research demonstrates that variations in the frequency of these rob/bartering practices could be explained by different opportunities for interaction with tourists, and thus for learning these rob and battering skills. The team of scientists is continuing its research and is now analyzing the individual, social and cognitive mechanisms involved in the learning process of these skills in order to test the hypothesis that these rob/bartering practices in Uluwatu could be a new behavioral tradition in this species.

Fany Brotcorne, did her post-doctoral work under the direction of Dr. Jean-Baptiste Leca of the University of Lethbridge in Canada, and now works as an assistant (Pr Pascal Poncin) in the Behavioral Biology Unit at the University of Liège.

(1)Brotcorne et al., Intergroup variation in robbing and bartering by long-tailed macaques at Uluwatu Temple (Bali, Indonesia), Primates, may 2017. https://link.springer.com/article/10.1007/s10329-017-0611-1