Food Habits of Sympatric Formosan Sambar (Rusa unicolor swinhoii) and Formosan Serow (Capricornis swinhoei) in a Subalpine–Alpine Habitat of Mount Yushan, the Highest Peak of Taiwan

Knowledge of inter- and intraspecific variation in food habits is essential for understanding both species life histories and the mechanisms facilitating coexistence among closely related species. However, such information remains limited for forest-dwelling ruminant ungulates in East Asia. In this study, we examined the food habits of sympatric Formosan sambar (Rusa unicolor swinhoii) and Formosan serow (Capricornis swinhoei) in a subalpine–alpine habitat of Mount Yushan, Taiwan, using fecal analysis. The proportion of graminoids in sambar feces ranged from 73.3% to 80.3%. Together with findings from previous studies, this result suggests that the food habits of sambar are flexible, with a graminoid-based diet becoming more prevalent in habitats dominated by graminoids. In contrast, the proportion of conifer leaves in serow feces ranged from 62.6% to 63.0%. This finding differs from previous reports from cloud coniferous forests, suggesting that serows also modify their diets according to habitat characteristics. Consequently, clear dietary segregation between the two species was observed, which may contribute to their coexistence.