Effects of diet and age–sex class on the fecal particle size of wild Japanese macaques ( <i>Macaca fuscata yakui</i> )

Fecal particle size provides important information on the feeding and digestion of herbivores. Understanding effects potential proximate determinants fecal helps us interpret this widely used measurement. In folivores, previous studies found that diet composition, dietary toughness, age–sex-related factors, such as body tooth wear, influenced size. However, role these factors remains unknown in frugivorous omnivorous primates. This study aims to clarify how age–sex class influence Japanese macaques Yakushima. We expected their variable differences among classes would cause variations simultaneously documented macaques' diet, lowland area Yakushima period from March 2018 April 2019. Unexpectedly, showed limited across months no difference classes. Dietary toughness size, while consumption fruits only a marginally significant negative effect. Our data indicate results chewing were not affected by our subjects, food comminution. lack variation might derive with low toughness. also physical structure preferred foods played an variations. These suggest comminution is less primates compared highly specialized species (e.g., geladas). Factors other than what we examined study, behavior, should be taken into consideration.