Behavior

Free trade between species

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Science  19 Feb 2021:
Vol. 371, Issue 6531, pp. 794
DOI: 10.1126/science.371.6531.794-a

Macaques have learned to barter for food with humans to return stolen possessions according to how highly an object is valued.

PHOTO: DBIMAGES/ALAMY STOCK PHOTO

The use of tokens as a bartering tool in nonhuman primate studies has taught us much about the willingness of nonhuman primates to engage in economic transactions. The question of whether it reflects a phenomenon that might emerge in natural conditions has received less attention. Long-tailed macaques (Macaca fascicularis) living in a Balinese temple regularly steal visitors' possessions and then barter for food with humans anxious to regain their belongings. Leca et al. discovered that they preferentially steal items of high value (for example, digital devices and wallets) over those with low value (for example, empty bags or hairpins) because higher-value food rewards tend to be offered for items that humans value more. The ability to identify high-value objects increases with age and experience, as does the macaques' skill as thieves. The animals in this group have been stealing and trading for more than 30 years, suggesting that the practice is culturally transmitted.

Philos. Trans. R. Soc. London Ser. B 376, 20190677 (2021).

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