Acquisition of object-robbing and object/food-bartering behaviours: a culturally maintained token economy in free-ranging long-tailed macaques

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Leca, Jean-Baptiste
Gunst, Noëlle
Gardiner, Matthew
Wandia, I. Nengah
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The Royal Society Publishing
The token exchange paradigm shows that monkeys and great apes are able to use objects as symbolic tools to request specific food rewards. Such studies provide insights into the cognitive underpinnings of economic behaviour in non-human primates. However, the ecological validity of these laboratory-based experimental situations tends to be limited. Our field research aims to address the need for a more ecologically valid primate model of trading systems in humans. Around the Uluwatu Temple in Bali, Indonesia, a large free-ranging population of long-tailed macaques spontaneously and routinely engage in token-mediated bartering interactions with humans. These interactions occur in two phases: after stealing inedible and more or less valuable objects from humans, the macaques appear to use them as tokens, by returning them to humans in exchange for food. Our field observational and experimental data showed (i) age differences in robbing/bartering success, indicative of experiential learning, and (ii) clear behavioural associations between value-based token possession and quantity or quality of food rewards rejected and accepted by subadult and adult monkeys, suggestive of robbing/bartering payoff maximization and economic decision-making. This 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.
Open access article. Creative Commons Attribution 4.0 International License (CC BY 4.0) applies
Token exchange , Bartering , Economic behaviour , Symbolic tool , Material culture , Ecological validity , Food rewards , Object-robbing , Object-bartering , Food-bartering , Long-tailed macaques
Leca, J.-B., Gunst, N., Gardiner, M., & Wandia, I. N. (2021). Acquisition of object-robbing and object/food-bartering behaviours: A culturally maintained token economy in free-ranging long-tailed macaques. Philosophical Transactions of the Royal Society B: Biological Sciences, 376(1819).,