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Background Snub-nosed monkeys are highly endangered primates and their population continues to decline with the habitat fragmentation. Artificial feeding and breeding is an important auxiliary conservation strategy. Studies have shown that changes and imbalances in the gut microbiota often cause gastrointestinal problems in captive snub-nosed monkeys. Here, we compare the gut microbiota composition, diversity, and predicted metabolic function of three endangered species of snub-nosed monkeys ( Rhinopithecus bieti , R. brelichi , and R. roxellana ) under the same captive conditions to further our understanding of the microbiota of these endangered primates and inform captive conservation strategies. 16 S rRNA gene sequencing was performed on fecal samples from 15 individuals ( R. bieti N = 5, R. brelichi N = 5, R. roxellana N = 5). Results The results showed that the three Rhinopithecus species shared 24.70% of their amplicon sequence variants (ASVs), indicating that the composition of the gut microbiota varied among the three Rhinopithecus species. The phyla Firmicutes and Bacteroidetes represented 69.74% and 18.45% of the core microbiota. In particular, analysis of microbiota diversity and predicted metabolic function revealed a profound impact of host species on the gut microbiota. At the genus level, significant enrichment of cellulolytic genera including Rikenellaceae RC9 gut group , Ruminococcus , Christensenellaceae R7 group , UCG 004 from Erysipelatoclostridiaceae, and UCG 002 and UCG 005 from Oscillospiraceae, and carbohydrate metabolism including propionate and butyrate metabolic pathways in the gut of R. bieti indicated that R. bieti potentially has a stronger ability to use plant fibers as energy substances. Bacteroides , unclassified Muribaculaceae , Treponema , and unclassified Eubacterium coprostanoligenes group were significantly enriched in R. brelichi . Prevotella 9 , unclassified Lachnospiraceae , and unclassified UCG 010 from Oscillospirales UCG 010 were significantly enriched in R. roxellana . Among the predicted secondary metabolic pathways, the glycan biosynthesis and metabolism had significantly higher relative abundance in the gut of R. brelichi and R. roxellana than in the gut of R. bieti . The above results suggest that different Rhinopithecus species may have different strategies for carbohydrate metabolism. The Principal coordinate analysis (PCoA) and Unweighted pair-group method with arithmetic mean (UPGMA) clustering tree revealed fewer differences between the gut microbiota of R. brelichi and R. roxellana . Correspondingly, no differences were detected in the relative abundances of functional genes between the two Rhinopithecus species. Conclusion Taken together, the study highlights that host species have an effect on the composition and function of the gut microbiota of snub-nosed monkeys. Therefore, the host species should be considered when developing nutritional strategies and investigating the effects of niche on the gut microbiota of snub-nosed monkeys.

Aim This study aims to propose a conservation network that contains suitable habitat and connectivity corridors for mitigation due to habitat transformation and fragmentation of Yunnan snub‐nosed monkeys (Rhinopithecus bieti). Further, we also aim to understand the effects of land‐use changes on the conservation network of R. bieti from 1990 to 2020. Location Three Parallel Rivers Region (TPRR) on the Qinghai–Tibetan Plateau (QTP) of China. Methods We used a GIS‐based niche model to predict habitat suitability and extracted highly suitable habitats with an area above 30 km2 as potential core habitats (PCH patches). We designed a normalized importance value index (NIVI) to select PCH patches with the top 5 NIVI values designated as priority protection habitats (PPHs), and we selected a circuit model to build connectivity corridors among PPHs and five protected areas (PAs) from 1990 to 2020. Results Unsuitable areas and lowly suitable habitats increased 69.3 and 46.8 km2, respectively, from 1990 to 2020. In particular, the area of PPHs dramatically decreased from 212.1 km2 in 1990 to 101.6 km2 in 2020. Average length of connectivity corridors among PCH patches and PPHs decreased from 75.9 km in 1990 to 56.8 km in 2020. Main conclusion Habitat loss and fragmentation are common phenomena as evidenced by decreasing in highly and moderately suitable habitats of R. bieti and increasing in lowly suitable habitats and unsuitable areas. Five PAs are central to build a conservation network and to protect populations and wild groups of R. bieti. Land use changes the conservation network of R. bieti in the past 30 years. Based on re‐planning boundaries of PAs to incorporate all protection network of R. bieti, it has practical significance to re‐adjust the system of PAs that conservation network of R. bieti should be as fundamental management unit for PA development.

Golden snub-nosed monkeys (Rhinopithecus roxellana) live in multilevel societies of over 100 individuals. Despite exploiting low visibility high-altitude forests and home ranges of 14 km2, they maintain large and cohesive social networks that serve to coordinate travel and daily activities effectively. During traveling, foraging, and feeding, golden snub-nosed monkeys communicate using contact or coo calls. These contact calls are conspicuous (70–75 decibels), directional, and function to communicate affiliative intention, identity, and location. Based on social network analyses, we found that golden snub-nosed monkeys exchanged contact calls among individuals within their resident one-male multi-female unit (OMU) and with conspecifics from neighboring OMUs. Within each OMU, there were more frequent call exchanges among more spatially separated members than among closely located individuals. In the case of contact calls between OMUs, there were more frequent contact call exchanges among closely located leader males. These findings demonstrate that contact call exchanges communicate individual identity and location, promote social bonds, and contribute to OMU and inter-OMU coordinated behavior that is essential to a well-functioning multilevel or tiered social network. In addition, given that 34% of all contact call exchanges were initiated by adult males (twice the number given by adult females), male OMU leadership appears to play a critical role in coordinating activities, directing travel, and promoting group cohesion. Moreover, given that higher-ranking males initiated more contact call exchanges than lower-ranking males, higher-ranking males appear to play a more important role in leading and coordinating travel and the fission–fusion dynamics of this multilevel society.Significance statementPrimates living in a large multi-level society face significant challenges in coordinating group movement and promoting social cohesion. We found that golden snub-nosed monkeys use contact coo calls to regulate spatial proximity and social interactions within their resident one-male multi-female unit (OMU) and with neighboring OMUs. Adult males are the primary call-givers. Within OMUs, there were significantly more frequent call exchanges between more spatially separated members. In contrast, between OMUs, there were more frequent contact call exchanges between leader males, especially when they were in close spatial proximity. Contact calls, which are given at an average distance of 5-200 m, communicate information concerning caller identity, location, and intention. Given that more than 90% of contact call exchanges occurred during foraging and traveling, this call type is critical in coordinating activities and regulating fission-fusion dynamics in this large multi-level society.

Since its initial discovery in 2010 in the Gaoligong Mountains on the Sino–Myanmar border, there remains no direct information on the feeding habits of the black snub-nosed monkey (Rhinopithecus strykeri). This species is on the verge of extinction, with an estimated remaining population of < 400 individuals. Due to difficulties in following these monkeys across steep mountainous terrain, during 203 observation days (September 2015–January 2017) we recorded 80 h of behavioral records of a wild population (Luoma group). Our preliminary results identified 14 plant species and four lichen species consumed by the monkeys. In addition, we provided the only two captive individuals of this species with a cafeteria diet composed of > 600 wild-collected plant species that were gathered from known R. strykeri habitats to determine which plant species and food items were considered palatable. Our results indicate that the captive monkeys freely consumed young and mature leaves, fruits/seeds, buds, flowers, twigs, and bark from 170 different species of trees, bushes, and herbs representing 76 genera and 41 plant families, as well as 15 species of lichen. All foods consumed by the wild monkeys were also consumed by the captive individuals. Food plants consumed by R. strykeri were found principally in intact subtropical evergreen broadleaf forests and hemlock-broadleaf mixed forests at an altitude of 2200–3000 m. Strict enforcement of habitat protection and access to resources across this elevation zone appear to be essential for the conservation and survivorship of this critically endangered primate.

The golden snub-nosed monkey ( Rhinopithecus roxellana ) is a rare and endemic species in China. The population of golden snub-nosed monkeys in Sichuan Province has an isolated genetic status, large population size, and low genetic diversity, making it highly vulnerable to environmental changes. Our study aimed to evaluate the potential impact of climate and land-use changes on the distribution and dispersal paths of the species in Sichuan Province. We used three general circulation models (GCMs), three greenhouse gas emission scenarios, and three land-use change scenarios suitable for China to predict the potential distributions of the golden snub-nosed monkey in the current and 2070s using the MaxEnt model. The dispersal paths were identified by the circuit theory. Our results suggested that the habitats of the golden snub-nosed monkey were reduced under all three GCM scenarios. The suitable habitats for the golden snub-nosed monkey would be reduced by 82.67%, 82.47%, and 75.17% under the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively, compared to the currently suitable habitat area. Additionally, we found that the density of future dispersal paths of golden snub-nosed monkeys would decrease, and the dispersal resistance would increase. Therefore, relevant wildlife protection agencies should prioritize the climatically suitable distributions and key dispersal paths of golden snub-nosed monkeys to improve their conservation. We identified key areas for habitat preservation and increased habitat connectivity under climate change, which could serve as a reference for future adaptation strategies.

The principle of acoustic allometry—the larger the animal, the lower its calls' fundamental frequency—is generally observed across terrestrial mammals. Moreover, according to the Acoustic Adaptation Hypothesis, open habitats favor the propagation of high-frequency calls compared to habitats with complex vegetational structures. We carried out playback experiments in which the calls of the Guizhou snub-nosed monkey (Rhinopithecus brelichi) were used as stimuli in sound attenuation and degradation experiments to test the hypothesis that propagation of Guizhou snub-nosed monkey calls is favored above vs through the forest floor vegetation. We found that low-pitched Guizhou snub-nosed monkey vocalizations suffered less attenuation than its high-pitched calls. Guizhou snub-nosed monkeys were observed emitting high-pitched calls from 1.5 to 5.0 m above the ground. The use of high-pitched calls from these heights coupled with the concomitant behavior of moving about above the understory may provide a signal for receivers which maximizes potential transmission and efficacy. Our results support the Acoustic Adaptation Hypothesis and suggest that by uncoupling its vocal output from its size, this monkey can produce a high-pitched call with a broad spectral bandwidth, thereby increasing both its saliency and the frequency range over which the animal may more effectively communicate in its natural habitat.

A novel bacterium, WQ 047T, was isolated from the faeces of Rhinopithecus bieti, a highly endangered primate endemic to China. The cells were aerobic, oval/rod-shaped, Gram-stain-negative, non-motile, catalase positive, and produced yellow pigmented colonies on Columbia Agar. The taxonomic position of WQ 047T was clarified by applying a polyphasic study based on 16S rRNA gene sequence phylogenetic analysis, extensive biological typing, and whole genome sequencing. Phylogenetic analysis indicated that stain WQ 047T belonged to the genus Sphingobacterium and its 16S rRNA gene sequence exhibited 96.47% pairwise similarity with that of the closest relatives Sphingobacterium nematocida M-SX103T. The calculated whole genome average nucleotide identity (ANI) value between strain WQ 047T and strain M-SX103 was 72.3%. The digital DNA-DNA hybridization value of strain WQ 047T and M-SX103T was 15.73%, which was obtained by calculating the genome-to-genome distance. The major fatty acids were C15:0 iso, C17:0 iso 3-OH, Summed Feature 3 (C16:1 ω7c/C16:1 ω6c) and Summed feature 9 (iso-C17:1ω9c and/or 10-methyl C16:0). The predominant polar lipids were PE, PL and APL. MK-7 was the predominant menaquinone. The G + C content of WQ 047T was 34.89 mol% according to genome analysis. All these characteristics were consistent with those of the genus of Sphingobacterium. Therefore, based on these results, we propose a novel species for which the name Sphingobacterium rhinopitheci sp. Nov. is proposed, with the type strain WQ 047T (= CCTCC AA 2020026T = KCTC82393T).

Sexual dimorphism exists widely in animals, manifesting in different forms, such as body size, color, shape, unique characteristics, behavior, and sound. Of these, body mass dimorphism is the most obvious. Studies of evolutionary and ontogenetic development and adaptation mechanisms of animals’ sexual dimorphism in body mass (SDBM), allow us to understand how environment, social group size, diet, and other external factors have driven the selection of sexual dimorphism. There are fewer reports of the ontogenetic development of sexual dimorphism in body mass in Rhinopithecus. This study explores the ontogenetic development pattern of SDBM in wild black-and-white snub-nosed monkeys (R. bieti), and the causes resulting in extreme sexual dimorphism compared to other colobines. A significant dimorphism with a ratio of 1.27 (p < 0.001) appears when females enter the reproductive period around six years old, reaching a peak (1.85, p < 0.001) when males become sexually mature. After the age of eight, the SDBM falls to 1.78, but is still significant (p < 0.001). The results also indicate that males had a longer body mass growth period than females (8 years vs. 5 years); females in larger breeding units had a significantly higher SDBM than those in smaller ones (2.12 vs. 1.93, p < 0.01). A comparative analysis with other colobines further clarifies that Rhinopithecus and Nasalis, which both have multilevel social organization, have the highest degree of SDBM among all colobines. The large SDBM in R. bieti can be explained through Bergman’s and Rensch’s rules. Overall, environmental adaptation, a distinctive alimentary system, and a complex social structure contribute to R. bieti having such a remarkable SDBM compared to other colobines. In addition, we found that females’ choice for males may not be significantly related to the development of SDBM.

As an endemic primate species with one of the highest priorities in wildlife conservation in China, Sichuan snub-nosed monkeys ( Rhinopithecus roxellana ) have undergone a sharp decline and range reduction in recent centuries. Here, we used maximum entropy modelling (MaxEnt) integrated with four types of environmental variables, including three biological climate variables (Bio17, precipitation of the driest quarter; Bio6, min. temperature of the coldest month; and Bio2, mean diurnal range), three topographic variables (altitude, slope, and aspect), two anthropogenic variables (Human Footprint Index and human disturbance), and three vegetation-related variables (enhanced vegetation index, normalized difference vegetation index, and Wet Index) to identify the spatial distribution of suitable habitats for Sichuan snub-nosed monkeys in Baihe Nature Reserve (BNR), which is located in the Minshan Mountains. The average training AUC of our model performance is 0.929 ± 0.003. The model predicted 9.6 km 2 of high suitability habitats and 14.1 km 2 of moderate suitability habitats for Sichuan snub-nosed monkeys, adding up to only 11.7% of the total area of concern for the study in the BNR. The top four variables ranked in the model (altitude, Human Footprint Index, human disturbance, and Bio17) accounted for relative gain contributions of 23.3%, 19.3%, 14.2%, and 13.4%, respectively. The predicted suitable habitats were confined to an altitude range of 1971–3198 m, Human Footprint Index of mainly 3–5 values, low human disturbance (mainly livestock), and precipitation of the driest (or coldest) quarter of 9–22 mm. Additionally, the suitable habitats were mainly distributed in the core zone (36.1%), buffer zone (26.8%), and experimental zone (29.5%). The remaining habitats (7.6%) were distributed in the 0.5-km buffer zone of the reserve border. The predicted suitable habitats indicated limited suitable habitat space for the Sichuan snub-nosed monkeys, with most of the suitable habitat distributed outside the core zone in the BNR. Our findings highlighted that human activities in all three functional zones could be the most negative factor on suitable habitat distribution of Sichuan snub-nosed monkeys in the BNR.