In the context of the ManyPrimates initiative, our long-tailed macaques (Macaca fascicularis) rarely exchanged a given food item for a larger food reward at a later time. We tested whether possession of a high-value food item affected their performance and found that macaques displayed improved abilities when the value of the exchange item is reduced. This suggests that the possession of a high-value item contributed to the low performance of the monkeys in the original exchange protocol.

Water is an essential commodity for life and is fundamental for metabolic processes. In free-living environments, species may use different strategies, abilities, and resources to access water. Here, we report on water consumption by Ateles chamek and Sapajus apella from the same tree source. These observations show that species use different strategies to access and consume water.