Japanese macaques (Macaca fuscata)
Japanese macaques are omnivorous primates that prefer nuts over soft mast. Tsuji et al. (2020) found that in a year when the preferred nut resource was low in abundance, high-ranking individuals monopolized this resource, forcing low-ranking individuals to consume and disperse soft mast. Low-ranking individuals also provided higher-quality seed dispersal as subordinates had lower rates of seed mastication (Fig. 2A). In contrast, during the masting year for nuts, there were no differences between social ranks in seed dispersal effectiveness. Since subordinate individuals had greater access to nuts, they consumed and dispersed less soft mast. Dominant individuals continued to be low-quantity seed dispersers, but the quality of seed dispersal increased during the mast year due to lower rates of seed mastication.