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

Fecal particle size provides important information on the feeding and digestion of animals. However, most previous studies focus on grass-eating animals, such as cattle and sheep. It remains unclear what factors influence fecal particle size in animals with more complicated diets, such as primates. To examine the potentially influential factors of this measurement in primates, this study collected and analyzed the diet, dietary toughness, and fecal particle size in Japanese macaques in Yakushima. The results indicate that dietary toughness, age, and sex did not influence fecal particle size. It may be a result of low dietary toughness. In contrast, the shape of some fruits may played important role in the variation of fecal particle size.