Dietary adaptations of Assamese macaques (Macaca assamensis) in limestone forests in Southwest China

Abstract

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.

Seasonal Variation in Activity Budget of Assamese Macaques in Limestone Forest of Southwest Guangxi, China

“…Regarding primates, only a handful of taxa depend almost exclusively on bamboo leaves (excluding cases of seasonal consumption of new bamboo shoots). These taxa include three bamboo lemurs: golden bamboo lemur (Hapalemur aureus), grey bamboo lemur (H. griseus) and greater bamboo lemur (H. simus) in Madagascar [Overdorff et al, 1997;Tan, 1999Tan, , 2000; Bale monkey (Chlorocebus djamdjamensis) in Ethiopia [Mekonnen et al, 2010[Mekonnen et al, , 2018; golden monkey (Cercopithecus mitis kandti) in Uganda [Twinomugisha et al, 2006] and Assamese macaque (M. assamensis) in Southwest China [Zhou et al, 2011;Huang et al, 2015a]. Normally, bamboo leaf eaters rest at a favourable place when budgeting their activity time likely because of their extremely folivorous diet [Overdorff et al, 1997;Mekonnen et al, 2010Mekonnen et al, , 2017Mekonnen et al, , 2018 and because bamboo leaves have much lower energy than leaves of most plants [Chongtham et al, 2011].…”

“…Limestone hills are an unusual habitat for primates. The limestone forest located in Southwest Guangxi, China, is characterised by seasonally variable rainfall, which influences the yield of young leaves and fruits, thus subjecting the resident primates to marked fluctuations in food availability [Fan et al, 2012;Huang et al, 2015a]. Unlike their congeners living in other habitats, Assamese macaques in the limestone forest are generally folivores, although they prefer fruits.…”

“…Unlike their congeners living in other habitats, Assamese macaques in the limestone forest are generally folivores, although they prefer fruits. They predominantly consume the young leaves of Bonia saxatilis year-round (a shrubby, karst-endemic bamboo; monthly feeding time: 48.8-94.1%), and they depend on leaves more heavily than other Asian macaques (77.3 vs. 25.1%) [Huang et al, 2015a]. Data on activity budget and behavioural adaptation strategies in response to changes in ecological factors of Assamese macaques are not available.…”

“…We first describe their activity budget and then examine the influences of diet, food availability, temperature and day length on activity budget. Finally, we discuss the behavioural adaptations of Assamese macaques to the limestone forest by testing the following predictions: 1 Assamese macaques in the limestone forest depend heavily on young bamboo leaves containing less energy than leaves of other plants [Zhou et al, 2011;Huang et al, 2015a]. We predicted that the macaques would spend less time on active behaviours (feeding and moving) than on inactive behaviours (resting and grooming), which would be similar to the behavioural patterns of folivorous primates but different from those of frugivorous primates [Hendershott et al, 2016;Yap et al, 2019].…”

“…We predicted that the macaques would spend less time on active behaviours (feeding and moving) than on inactive behaviours (resting and grooming), which would be similar to the behavioural patterns of folivorous primates but different from those of frugivorous primates [Hendershott et al, 2016;Yap et al, 2019]. 2 Assamese macaques in the limestone forest are highly folivorous while still preferring fruits [Huang et al, 2015a]. Normally, primates spend more time moving according to fruit availability [Richard, 1985].…”