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

Examined a sample of 84 video-recorded token-robbing events, randomly selected from our observational data, that featured 500 potential human targets

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Findings

• Examined a sample of 84 video-recorded token-robbing events, randomly selected from our observational data, that featured 500 potential human targets
• Considered the food items that the monkey could reach/grab when proposed/tossed to them by the human barterers
• Did not find a significant increase in token-robbing success from juveniles to subadults to adults, Prediction 1b was partly supported owing to the difference between the former and the latter two age classes
• There was no significant difference in the average number of food rewards being rejected by the monkey before accepting a different type of food reward to end the token/reward-bartering sequence when it was holding a high-valued token, compared to a medium-valued token, either in subadults or in adults
• Subadult and adult subjects were significantly more likely to end a successful token/reward-bartering sequence by returning the token in exchange for the least-preferred type of food rewards when they were holding a medium-valued token compared to when they were holding a high-valued token
• Found a significant increase in token-robbing success from juveniles to subadults to adults, whereas the main behaviour patterns required for the successful performance of token/reward-bartering interactions were already in place from around 4 years