Variations in diet composition of sympatric Trachypithecus francoisi and Macaca assamensis in the limestone habitats of Nonggang, China

Abstract

Comparative studies of sympatric species are essential for understanding behavioral and ecological adaptation as well as the mechanisms that can reduce resource competition to allow coexistence. François' langurs (Trachypithecus francoisi) and Assamese macaques (Macaca assamensis) are sympatric primate species found in the limestone seasonal rainforests of Nonggang Nature Reserve, southwestern Guangxi, China. To explore their different adaptation strategies, we collected data on diet using scan sampling at 15-min intervals. Our results revealed that François' langurs showed a more flexible diet composition than Assamese macaques. François' langurs increased dietary diversity and mature leaf consumption in response to seasonal scarcity of preferred young leaves and fruits, whereas Assamese macaques relied heavily on young bamboo leaves (Indocalamus calcicolus) in most months. These variations reflect the differences in digestive physiology, morphology, and the temporal and spatial distribution of food resources.