Xuecong Liu

Kinship plays an essential role in the evolution of mammalian social behavior. The mechanisms of kin discrimination have attracted enduring interest, and phenotype matching and familiarity through prior association are the most likely ones among mammals. Previous studies on the mechanisms of kin discrimination based on acoustic signals have obtained inconsistent results. Golden snub-nosed monkeys (Rhinopithecus roxellana) are well-known for their multilevel social structure composed of several distinct units, the formation and stability of which largely depend on genetic relatedness among adult females. Taking advantage of the long-term demographic monitoring of a provisioned free-ranging group in Shennongjia National Park, China, this study provided a systematic acoustic analysis for contact calls of adult females in relation to kinship and familiarity. Results showed that structural similarities of contact calls between individuals did not vary among nonkin, distant kin, or close kin, while the calls exhibited clear individuality. Structural similarities of the calls between individuals significantly increased initially and then showed a tendency to decrease as the length of time co-resident in the same social unit (an index of familiarity) increased. Collectively, the acoustic structure was likely to reflect a dynamic tradeoff between maintaining social bonds and advertising individual identities. In addition, acoustic similarities decreased with age differences between individuals, likely due to age-related morphological changes in vocal apparatus. The results of this study improved the understanding of specific functions of contact calls and provided a basis for investigating kin discrimination mechanisms via acoustic signals in a primate living in multilevel societies.

Knowledge on the home range size of a species or population is important for understanding its behavioral and social ecology and improving the effectiveness of conservation strategies. We studied the home range size of two different-sized groups of golden snub-nosed monkeys (Rhinopithecus roxellana) in Shennongjia, China. The larger group (236 individuals) had a home range of 22.5 km2 from September 2007 to July 2008, whereas the smaller group (62 individuals) occupied a home range of 12.4 km2 from November 2008 to July 2009. Both groups exhibited considerable seasonal variation in their home range size, which was likely due to seasonal changes in food availability and distribution. The home range in any given season (winter, spring, summer, or winter+spring+summer) of the larger group was larger than that of the smaller group. As the two groups were studied in the same area, with the confounding effects of food availability thus minimized, the positive relationship between home range size and group size suggested that scramble feeding competition increased within the larger group.

Vocal individuality is a prerequisite for individual recognition, especially when visual and chemical cues are not available or effective. Vocalizations encoding information of individual identity have been reported in many social animals and should be particularly adaptive for species living in large and complexly organized societies. Here, we examined the individuality in coo calls of adult male golden snub-nosed monkeys (Rhinopithecus roxellana) living in a large and multilevel society. Coo calls are one of the most frequently occurring call types in R. roxellana and likely serve as the signals for contact maintenance or advertisement in various contexts including group movement, foraging, and resting. From April to October 2016, April to July 2017, and September to October 2017, we recorded a total of 721 coo calls from six adult males in a provisioned, free-ranging group and one adult male in captivity in Shennongjia National Park, China. We selected 162 high-quality recordings to extract 14 acoustic parameters based on the source-filter theory. Results showed that each of all parameters significantly differed among individuals, while pairwise comparisons failed to detect any parameter that was different between all pairs. Furthermore, a discriminant function analysis indicated that the correct assignment rate was 80.2% (cross-validation: 67.3%), greater than expected by chance (14.3%). In conclusion, we found evidence that coo calls of adult male R. roxellana allowed the reliable accuracy of individual discrimination complementarily enhanced by multiple acoustic parameters. The results of our study point to the selective pressures acting on individual discrimination via vocal signals in a highly gregarious forest-living primate.

Vocal signaling represents a primary mode of communication for most nonhuman primates. A quantitative description of the vocal repertoire is a critical step in in‐depth studies of the vocal communication of particular species, and provides the foundation for comparative studies to investigate the selective pressures in the evolution of vocal communication systems. The present study was the first attempt to establish the vocal repertoire of free‐ranging adult golden snub‐nosed monkeys (Rhinopithecus roxellana) based on quantitative methods. During 8 months in Shennongjia National Park, China, we digitally recorded the vocalizations of adult individuals from a provisioned, free‐ranging group of R. roxellana across a variety of social‐ecological contexts. We identified 18 call types, which were easily distinguishable by ear, visual inspection of spectrograms, and quantitative analysis of acoustic parameters measured from recording samples. We found a great sexual asymmetry in the vocal repertoire size (females produced many more call types than males), likely due to the sex differences in body size and social role. We found a variety of call types that occurred during various forms of agonistic and affiliative interactions at close range. We made inference about the functions of particular call types based on the contexts in which they were produced. Studies on the vocal communication in R. roxellana are particularly valuable since they provide a case about how nonhuman primates, inhabiting forest habitats and forming complex social systems, use their vocalizations to interact with their social and ecological environments.

The gastrointestinal tract of primates harbors a complex microbial community, playing an essential role in the degradation of otherwise indigestible structural carbohydrates. The phylogenetic and functional diversity of the bacterial community in the feces as a surrogate for the gastrointestinal tract of wild Sichuan snub‐nosed monkeys (Rhinopithecus roxellana, N = 6) was characterized based on sequence analysis of 16S rRNA genes. A sex comparison was conducted, with a prior hypothesis that the abundances of the bacterial taxa and/or functional categories associated with energy and nutrient metabolism would be higher in adult females (N = 3) due to the higher reproductive costs compared to adult males (N = 3). Ten phyla were identified in all samples, among which Bacteroidetes and Firmicutes were the predominant. Included in the above two phyla, the members of Prevotellaceae (Prevotella in particular) and Ruminococcaceae were highly abundant, which are common bacteria in the gastrointestinal tract of primates and can degrade various structural carbohydrates such as cellulose, hemicellulose, and pectin. This functionality was in line with the high abundances of the metagenomes associated with carbohydrate metabolism. Consistent with our hypothesis, the abundances of the metagenomes associated with energy metabolism, folding/sorting and degradation, glycan biosynthesis and metabolism, and metabolism of amino acids were higher in adult females relative to adult males. Sex differences were also detected in the bacterial community structure, although no sex differences in the proportions of any bacterial taxa were found likely due to the small sample size. These results suggested that gastrointestinal bacterial communities may aid adult females in increasing energy and nutrition utilization efficiencies compared to adult males. Fecal bacterial communities were found to be more similar between individuals in adult females than in adult males. Our study presented the first examination of the fecal bacterial diversity of a little‐studied, endangered foregut fermenter.

Natural disasters can negatively affect primate population demography and social group structure. A clear understanding of these effects has important implications for wildlife conservation. The worst snow storms in nearly five decades hit portions of southern and central China between January 10 and February 6, 2008, presenting a unique opportunity to observe their immediate effects on a previously studied group of Hubei Golden Snub‐nosed Monkeys (Rhinopithecus roxellana hubeiensis) in temperate forests in Shennongjia Nature Reserve, Hubei Province, China. We recorded social and demographic characteristics of the group before and after the snow storms. The average group size decreased from 270 individuals before the storms to 197 individuals after the storms, a reduction of 27.2%. Adult females (30.1%), juveniles (38.1%) and infants (55.4%) suffered higher mortality than did adult males (15.7%). Despite age and sex‐based differences in mortality, the ratios of adult males to adult females, adults to immatures and adult females to immatures remained similar before and after the storms. However, higher mortality among females, juveniles and infants may reduce the group's long‐term potential for growth. Am. J. Primatol. 71:523–526, 2009.