Age-sex analysis for the diet of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in Shennongjia National Nature Reserve, China

Abstract

Age-sex differences in diet have been reported in many nonhuman primates, and body size, reproductive costs, and growth are three mutually non-exclusive factors often proposed to explain such differences. Smaller animals tend to feed on high quality foods (high in protein/energy) more often than larger animals due to their higher metabolic requirements per body weight. Animals of different sizes tend to use different substrate levels, leading to dietary differences if food resources are unevenly distributed along substrate levels. Adult females and juveniles experience additional metabolic requirements for reproduction and growth, respectively, and tend to feed on high quality foods more frequently than adult males. We conducted an age-sex analysis for the diet of Sichuan snub-nosed monkeys (Rhinopithecus roxellana) in Shennongjia, China. In spite of general age-sex similarities, we found that adult males ate herbs more frequently than juveniles and adult females, most likely because they were more terrestrial. As predicted, juveniles ate high quality foods (young leaves, fruits, seeds, and buds) more frequently, and meanwhile ate low quality foods (barks and lichens) less frequently than adult males across the study year or in some seasons when these food types were eaten. However, we found high similarities in diet between adult females and adult males. The most likely reason was that the low diversity of food sources and strong phenological synchrony did not allow adult females to select foods based on quality to cope with their higher metabolic constraints compared to adult males. Surprisingly, the only sex difference in diet except herbs was that adult females ate lichens more frequently in autumn. One plausible reason was that lactating females experienced their highest metabolic requirements in the middle period of infant care (autumn), and had to disproportionately increase the intake of lichens due to the limited availability of plant foods.

Cafeteria‐style feeding trials provide new insights into the diet and nutritional strategies of the black snub‐nosed monkey (Rhinopithecus strykeri): Implications for conservation

“…Longma in autumn (CP: 11.01%, Huang, Huo, Yang, Cui, & Xiao, 2010). The crude protein content of young leaves consumed by the captive R. strykeri was, however, similar to young leaves consumed by wild R. roxellana in spring at two different field sites (CP: 19.97%, Hou, 2018; CP: 22.69%, Li, 2015). The mean NDF of leaves consumed by the captive R. strykeri in spring and in autumn in Mt.…”

“…The protein‐to‐fiber ratio of food items consumed by R. strykeri in our study was higher than for nonconsumed items, which is consistent with previous findings for African and Asian colobines ( Procolobus badius, C. guereza , Wasserman & Chapman, 2003; Presbytis rubicunda , Hanya & Bernard, 2015; R. bieti ; Huang et al, 2010; and R. roxellana , Hou et al, 2018). However, the fiber content of leaves consumed by R. avunculus in Khau Ca (ADF; Lan Anh et al, 2014), R. bieti in the Longma Mountains (NDF; Huang et al, 2010), R. roxellana in Shennongjia (Crude Fiber; Liu, Stanford, Yang, Yao, & Li, 2013; ADF, Li, 2015), R. roxellana in the Qingling mountains (NDF & ADF, Hou, 2018), and R. brelichi in Fanjingshan (NDF, ADF, and lignin; Bleisch et al, 1998) did not differ from that of nonconsumed leaves. Similarly, we also found that ADF and ADL of food items consumed by captive R. strykeri did not differ significantly from nonconsumed food items.…”

Improving conservation effectiveness of nature reserve for golden snub‐nosed monkey, a niche‐based approach

“…The activity area for Rhinopithecus roxellana is based on published records of Li et al. (), data of the SNR authority and data from the current study…”

“…Rhinopithecus spp. are known to select different habitat and food between summer–autumn and winter–spring periods (Li, ; Li, Stanford, & Yang, ). Our preliminary analysis of the data indicated that activities of the golden snub‐nosed monkey differed both spatially and between winter–spring and summer–autumn (Figure ).…”

Dietary diversity, feeding selectivity, and responses to fruit scarcity of two sympatric Bornean primates (Hylobates albibarbis and Presbytis rubicunda rubida)

“…For example, in mountain gorillas ( Gorilla beringei) , females and growing juveniles eat more food, and consume more protein per kilogram of body mass, than males [57]. Significant differences in dietary composition between age and sex classes have also been described for sifakas ( Propithecus verreauxi [58]), green monkeys ( Cercopithecus sabaeus [59]), and snub-nosed monkeys ( Rhinopithecus roxellana [60]). We collected feeding observations from the first individual detected along the transect line or a randomly selected focal animal, regardless of age or sex class, so there are no inherent biases in our methods towards certain types of individuals.…”