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Limestone hills are an unusual habitat for primates, prompting them to evolve specific behavioral adaptations to the component karst habitat. From September 2012 to August 2013, we collected data on the diet of one group of Assamese macaques living in limestone forests at Nonggang National Nature Reserve, Guangxi Province, China, using instantaneous scan sampling. Assamese macaques were primarily folivorous, young leaves accounting for 75.5% and mature leaves an additional 1.8% of their diet. In contrast, fruit accounted for only 20.1%. The young leaves of Bonia saxatilis, a shrubby, karst-endemic bamboo that is superabundant in limestone hills, comprised the bulk of the average monthly diet. Moreover, macaques consumed significantly more bamboo leaves during the season when the availability of fruit declined, suggesting that bamboo leaves are an important fallback food for Assamese macaques in limestone forests. In addition, diet composition varied seasonally. The monkeys consumed significantly more fruit and fewer young leaves in the fruit-rich season than in the fruit-lean season. Fruit consumption was positively correlated with fruit availability, indicating that fruit is a preferred food for Assamese macaques. Of seventy-eight food species, only nine contributed >0.5% of the annual diet, and together these nine foods accounted for 90.7% of the annual diet. Our results suggest that bamboo consumption represents a key factor in the Assamese macaque's dietary adaptation to limestone habitat. Am. J. Primatol. 77:171-185, 2015. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Information on the positional behavior and habitat use of primates can help elucidate relationships among species' morphology, behavior, and environment, and contribute to our understanding of species' behavioral and ecological adaptations. Limestone habitats provide a unique and challenging habitat for primates, but there have been few detailed studies of the genus Macaca in such habitats, making a comparative understanding of extant limestone primates' behavioral adaptations incomplete. We collected data on positional behavior and habitat use by sympatric Assamese macaques ( Macaca assamensis) and rhesus macaques ( M. mulatta) in limestone habitat at Nonggang Nature Reserve, southwestern Guangxi, China, and examined the effects of morphological and ecological factors on positional behavior and habitat use. Our results indicate interspecific differences in positional behavior, showing different preferences for locomotor modes and substrates. Rhesus macaques tended to walk horizontally, whereas Assamese macaques more often climbed vertically. Rhesus macaques used smaller substrates (twigs) more frequently than did Assamese macaques. Time spent in different zones of limestone hills and forest strata also varied significantly between the two macaques. Assamese macaques most often used cliff faces, and tended to be terrestrial. Rhesus macaques were most likely to stay low on the hillsides, and spent most of their time in the lower strata of trees. These differences in positional behavior and habitat use are linked to differences in limb length and body size in the two species, and may be explained by the spatial distribution of preferred foods and structure of the forest in different areas of the limestone hills. [ABSTRACT FROM AUTHOR]