The strategies used by individuals to deploy altruistic behaviors have long captured research attention. Two general mechanisms can account for the decision-making process underpinning the deployment of altruistic behaviors among nonkin. The first mechanism, referred to here as "temporal...

Variations in birth sex ratios in primates are notoriously inconsistent and have been repeatedly suggested to be mainly owing to stochastic processes. An examination of temporal consistency within primate populations revealed that the effect of dominance rank on birth sex ratio tends to remains...

Grooming among female Japanese macaques (Macaca fuscata) was studied to test some predictions derived from the application of biological market theory. Contrary to expectations, Japanese macaques did not time match the duration of grooming episodes, their degree of reciprocation was not related...