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.