Comparing the gut microbiota of Sichuan golden monkeys across multiple captive and wild settings: roles of anthropogenic activities and host factors.

BACKGROUND: Captivity and artificial food provision are common conservation strategies for the endangered golden snub-nosed monkey (Rhinopithecus roxellana). Anthropogenic activities have been reported to impact the fitness of R. roxellana by altering their gut microbiota, a crucial indicator of animal health. Nevertheless, the degree of divergence in gut microbiota between different anthropogenically-disturbed (AD) R. roxellana and their counterparts in the wild has yet to be elucidated. Here, we conducted a comparative analysis of the gut microbiota across nine populations of R. roxellana spanning China, which included seven captive populations, one wild population, and another wild population subject to artificial food provision. RESULTS: Both captivity and food provision significantly altered the gut microbiota. AD populations exhibited common variations, such as increased Bacteroidetes and decreased Firmicutes (e.g., Ruminococcus), Actinobacteria (e.g., Parvibacter), Verrucomicrobia (e.g., Akkermansia), and Tenericutes. Additionally, a reduced Firmicutes/Bacteroidetes ratiosuggested diminished capacity for complex carbohydrate degradation in captive individuals. The results of microbial functional prediction suggested that AD populations displayed heightened microbial genes linked to vitamin and amino acid metabolism, alongside decreased genes associated antibiotics biosynthesis (e.g., penicillin, cephalosporin, macrolides, and clavulanic acid) and secondary metabolite degradation (e.g., naphthalene and atrazine). These microbial alterations implied potential disparities in the health status between AD and wild individuals. AD populations exhibited varying degrees of microbial changes compared to the wild group, implying that the extent of these variations might serve as a metric for assessing the health status of AD populations. Furthermore, utilizing the individual information of captive individuals, we identified associations between variations in the gut microbiota of R. roxellana and host age, as well as pedigree. Older individuals exhibited higher microbial diversity, while a closer genetic relatedness reflected a more similar gut microbiota. CONCLUSIONS: Our aim was to assess how anthropogenic activities and host factors influence the gut microbiota of R. roxellana. Anthropogenic activities led to consistent changes in gut microbial diversity and function, while host age and genetic relatedness contributed to interindividual variations in the gut microbiota. These findings may contribute to the establishment of health assessment standards and the optimization of breeding conditions for captive R. roxellana populations.

Scientific activism to protect the world's primates and their environments from extinction: Introduction to the special issue.

Nonhuman primates and their habitats are facing an impending extinction crisis. Approximately 69% of primate species are listed by the International Union for Conservation of Nature as threatened and 93% have declining populations. Human population growth (expected to reach 10.9 billion by the year 2100), the unsustainable demands of a small number of consumer nations for forest-risk commodities, deforestation and habitat conversion, the expansion of roads and rail networks, cattle ranching, the hunting and trapping of wild primate populations, and the potential spread of infectious diseases are among the primary drivers of primate population decline. Climate change will only exacerbate the current situation. The time to act to protect primate populations is now! In this special issue of the American Journal of Primatology, we present a series of commentaries, formulated as "Action Letters." These are designed to educate and inform primatologists, conservation biologists, wildlife ecologists, political leaders, and global citizens about the conservation challenges faced by particular primate taxa and particular world regions, and present examples of specific actions that one can take, individually and collectively, to promote the persistence of wild primate populations and environmental justice for local human populations and impacted ecological communities. As scientists, researchers, and educators, primatologists are in a unique position to lead local, national, and international efforts to protect biodiversity. In this special issue, we focus on primates of the Brazilian Amazon, lemurs of northeast Madagascar, Temminck's red colobus monkey (Piliocolobus badius temminckii), night monkeys (Aotus spp.), long-tailed macaques (Macaca fascicularis), the primate pet trade, and professional capacity building to foster conservation awareness and action. We encourage primatologists, regardless of their research focus, to engage in both advocacy and activism to protect wild primate populations worldwide.

Dynamic foraging strategy adaptation to heterogeneous environments contributes to social aggregation in snub-nosed monkeys.

The dynamics of animal social structures are heavily influenced by environmental patterns of competition and cooperation. In folivorous colobine primates, prevailing theories suggest that larger group sizes should be favored in rainforests with a year-round abundance of food, thereby reducing feeding competition. Yet, paradoxically, larger groups are frequently found in high-altitude or high-latitude montane ecosystems characterized by a seasonal scarcity of leaves. This contradiction is posited to arise from cooperative benefits in heterogeneous environments. To investigate this hypothesis, we carried out a six-year field study on two neighboring groups of golden snub-nosed monkey ( Rhinopithecus roxellana), a species representing the northernmost distribution of colobine primates. Results showed that the groups adjusted their movement and habitat selection in response to fluctuating climates and spatiotemporal variability of resources, indicative of a dynamic foraging strategy. Notably, during the cold, resource-scarce conditions in winter, the large group occupied food-rich habitats but did not exhibit significantly longer daily travel distances than the smaller neighboring group. Subsequently, we compiled an eco-behavioral dataset of 52 colobine species to explore their evolutionary trajectories. Analysis of this dataset suggested that the increase in group size may have evolved via home range expansion in response to the cold and heterogeneous climates found at higher altitudes or latitudes. Hence, we developed a multi-benefits framework to interpret the formation of larger groups by integrating environmental heterogeneity. In cold and diverse environments, even smaller groups require larger home ranges to meet their dynamic survival needs. The spatiotemporal distribution of high-quality resources within these expanded home ranges facilitates more frequent interactions between groups, thereby encouraging social aggregation into larger groups. This process enhances the benefits of collaborative actions and reproductive opportunities, while simultaneously optimizing travel costs through a dynamic foraging strategy.

Climate change and anthropogenic activities shrink the range and dispersal of an endangered primate in Sichuan Province, China.

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.

Species variations in the gut microbiota of captive snub-nosed monkeys.

Introduction: Snub-nosed monkeys are species in danger of extinction due to habitat fragmentation and human activities. Captivity has been suggested as an Auxiliary Conservation Area (ASA) strategy. However, little is known about the adaptation of different species of snub-nosed monkeys to captive environments. Methods: This study compared the gut microbiota between Rhinopithecus bieti, R. brelichi, and R. roxellana under identical captive conditions to provide insights for improving captive conservation strategies. Results: The results showed that these three Rhinopithecus species shared 80.94% of their Operational Taxonomic Unit (OTU), indicating high similarity in gut microbiota composition. The predominant phyla were Firmicutes and Bacteroidetes for all three Rhinopithecus species, but differences were observed in diversity, characteristic bacterial communities, and predicted function. Significant enrichment of cellulolytic families, including Ruminococcaceae, Clostridiales vadinBB60 group, Christensenellaceae, and Erysipelotrichaceae, and pathways involved in propionate and butyrate metabolism in the gut of R. bieti suggested that it may have a superior dietary fiber utilization capacity. In contrast, Bacteroidetes, Ruminoccaceae, and Trichospiraceae were more abundant in R. brelichi and R. roxellana, and were associated with saccharide and glycan metabolic pathways. Moreover, R. brelichi and R. roxellana also had higher similarity in microbiota composition and predicted function. Discussion: In conclusion, the results demonstrate that host species are associated with the composition and function of the gut microbiota in snub-nosed monkeys. Thus, host species should be considered when formulating nutritional strategies and disease surveillance in captive snub-nosed monkeys.

Leopard predation on wild Sichuan snub-nosed monkeys.

Predation is widely recognized as a powerful selective pressure on primate behavior and ecology, although knowledge of predator-prey relationships remains limited partly due to the rarity of directly observed attacks on primates. Here, we describe four confirmed or suspected instances of leopard (Panthera pardus) predation on free-ranging Sichuan (golden) snub-nosed monkeys (Rhinopithecus roxellana), a highly endangered colobine species endemic to China. We recorded predation events and the reactions of monkey group members. We suggest that the evolution of a multilevel society may be an adaptive response by Sichuan snub-nosed monkeys to the risk from leopards as well as other potential predators, one that balances the pressures of predation and intra-species competition and conflict.

Comparative study of the gut microbiota in three captive Rhinopithecus species.

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.

Lineage-specific accelerated sequences underlying primate evolution.

Understanding the mechanisms underlying phenotypic innovation is a key goal of comparative genomic studies. Here, we investigated the evolutionary landscape of lineage-specific accelerated regions (LinARs) across 49 primate species. Genomic comparison with dense taxa sampling of primate species significantly improved LinAR detection accuracy and revealed many novel human LinARs associated with brain development or disease. Our study also yielded detailed maps of LinARs in other primate lineages that may have influenced lineage-specific phenotypic innovation and adaptation. Functional experimentation identified gibbon LinARs, which could have participated in the developmental regulation of their unique limb structures, whereas some LinARs in the Colobinae were associated with metabolite detoxification which may have been adaptive in relation to their leaf-eating diet. Overall, our study broadens knowledge of the functional roles of LinARs in primate evolution.

Terrestriality as reflected in the humerus of Mesopithecus delsoni (Cercopithecidae, Colobinae) from Hadjidimovo, Bulgaria.

The fossil colobine genus Mesopithecus is the oldest European monkey, ranging from the Late Miocene to the earliest Pleistocene. It is one of the most successful genera of Old World monkeys since the late Neogene. Its ecology, as an indicator of Late Miocene environments, is of particular interest. Several investigations have clarified the locomotor adaptations of the middle and late Turolian Balkan Mesopithecus pentelicus, but such studies are virtually absent for the earliest known taxon, the early Turolian Mesopithecus delsoni, due to the lack of fossil material. However, a large collection of postcranial material of M. delsoni from the Bulgarian Early Turolian locality of Hadjidimovo provides the first opportunity for such an analysis. The present study examines the functional morphology of the fossil humeri of M. delsoni from Hadjidimovo, Bulgaria, and of M. pentelicus from Bulgarian and Greek fossil localities. We provide detailed comparative qualitative descriptions and use univariate and multivariate quantitative analyses of one angular and 12 linear measurements in comparison with 149 extant Cercopithecidae, representing 14 genera and 34 species. Our analyses demonstrate that the humeral elements from Hadjidimovo show important morphological differences from those of M. pentelicus from Pikermi, Kalimantsi, and Gorna Sushitsa, suggesting strong terrestrial tendencies for M. delsoni. This finding, when considered together with the paleobiologial inference of semiterrestriality for the early cercopithecoid Victoriapithecidae, might indicate that the first colobines (still unknown) were also semiterrestrial. Finally, the morphological features related to terrestriality in M. delsoni, which differ from those of the later M. pentelicus, provide additional data in support of the idea that the older taxon represents a separate species.

Aspects of molar form and dietary proclivities of African colobines.

This study investigates aspects of molar form in three African colobine species: Colobus polykomos, Colobus angolensis, and Piliocolobus badius. Our samples of C. polykomos and P. badius are from the Taï Forest, Ivory Coast; our sample of C. angolensis is from Diani, Kenya. To the extent that protective layers surrounding seeds are hard, we predicted that molar features related to hard-object feeding would be more pronounced in Colobus than they are Piliocolobus, as seed-eating generally occurs at higher frequencies in species of the former. We further predicted that among the colobines we studied, these features would be most pronounced in Taï Forest C. polykomos, which feeds on Pentaclethra macrophylla seeds encased within hard and tough seed pods. We compared overall enamel thickness, enamel thickness distribution, absolute crown strength, cusp tip geometry, and flare among molar samples. Sample sizes per species and molar type varied per comparison. We predicted differences in all variables except overall enamel thickness, which we expected would be invariant among colobines as a result of selection for thin enamel in these folivorous species. Of the variables we examined, only molar flare differed significantly between Colobus and Piliocolobus. Our findings suggest that molar flare, an ancient feature of cercopithecoid molars, was retained in Colobus but not in Piliocolobus, perhaps as a result of differences in the seed-eating proclivities of the two genera. Contrary to predictions, none of the aspects of molar form we investigated tracked current dietary differences in seed-eating between the two Colobus species. Finally, we explored the possibility that molar flare and absolute crown strength, when analyzed together, might afford greater differentiation among these colobine species. A multivariate t test of molar flare and absolute crown strength differentiated C. polykomos and P. badius, possibly reflecting known niche divergence between these two sympatric Taï Forest species.

Social and paternal female choice for male MHC genes in golden snub-nosed monkeys (Rhinopithecus roxellana).

Genes of the major histocompatibility complex (MHC) play important roles in vertebrate immunocompetence. MHC genes thus offer females indirect benefits to mate choice through the production of offspring of an optimal MHC genotype. Females may choose males with specific MHC haplotypes, dissimilar MHC genotypes, MHC heterozygous males or MHC-diverse males. We tested these four alternatives for both female social and paternal choice in wild golden snub-nosed monkeys (Rhinopithecus roxellana) by examining overall genetic variability (via microsatellites) and four MHC-genes (DRB1, DRB2, DQA1 and DQB1). Monte Carlo randomization tests showed that MHC dissimilarity was favoured for social choice (males to which females were socially affiliated) and intermediate MHC dissimilarity was favoured in paternal choice (fathers of offspring). No evidence of inbreeding avoidance was found for either social or paternal mates. We found that MHC heterozygotes, higher microsatellite multilocus heterozygosity and higher microsatellites diversity were favoured for social mates, and higher microsatellite diversity was favoured for paternal mates. Independent of male age, we found that the formation of male-female social pairings is significantly predicted by compatibility based on the sharing of MHC haplotypes. However, we found no evidence of independent genetic effects on the duration of male-female social pairings, male social status (achieving OMU leader male status or not), the number of females with which individual leader males paired, the likelihood of potential male-female pairings producing offspring, or whether males fathered offspring or not. Overall, our findings suggest different genetic factors are involved in social and paternal choice in R. roxellana.

Gut microbiome variations in Rhinopithecus roxellanae caused by changes in the environment.

BACKGROUND: The snub-nosed monkey (Rhinopithecus roxellanae) is an endangered animal species mainly distributed in China and needs to be protected. Gut microbiome is an important determinant of animal health and population survival as it affects the adaptation of the animals to different foods and environments under kinetic changes of intrinsic and extrinsic factors. Therefore, this study aimed to elucidate gut fecal microbiome profiles of snub-nosed monkeys affected by several extrinsic and intrinsic factors, including raising patterns (captive vs. wild), age, sex, and diarrheal status to provide a reference for making protection strategies. RESULTS: The 16S rRNA gene sequencing was firstly used to pre-check clustering of 38 fecal samples from the monkeys including 30 wild and 8 captive (5 healthy and 3 diarrheal) from three Regions of Shennongjia Nature Reserve, Hubei Province, China. Then the 24 samples with high-quality DNA from 18 wild and 6 captive (4 healthy and 2 diarrheal) monkeys were subjected to shotgun metagenomic sequencing to characterize bacterial gut microbial communities. We discovered that the raising pattern (captive and wild) rather than age and sex was the predominant factor attributed to gut microbiome structure and proportionality. Wild monkeys had significantly higher bacterial diversity and lower Bacteroidetes/Firmicutes ratios than captive animals. Moreover, the gut microbiomes in wild healthy monkeys were enriched for the genes involved in fatty acid production, while in captive animals, genes were enriched for vitamin biosynthesis and metabolism and amino acid biosynthesis from carbohydrate intermediates. Additionally, a total of 37 antibiotic resistant genes (ARG) types were detected. Unlike the microbiome diversity, the captive monkeys have a higher diversity of ARG than the wild animals. CONCLUSION: Taken together, we highlight the importance of self-reprogramed metabolism in the snub-nosed monkey gut microbiome to help captive and wild monkeys adapt to different intrinsic and extrinsic environmental change.

The range and habitat suitability of François' langur (Trachypithecus francoisi) in Mayanghe Nature Reserve, China.

The François' langur (Trachypithecus francoisi) is an endangered primate living in limestone forests in Vietnam and China. From October 2017 to August 2018, the habitat preferences and the range of the Francois' langur were surveyed in the Mayanghe Nature Reserve, Guizhou, People's Republic of China. To estimate the range and predict suitable habitat of François' langur, a Gaussian normal kernel density estimation and species distribution models (BIOMOD2) were used along with data on environmental variables and records of the langur's occurrence. The total range of François' langur in the reserve is 68.76 km2, accounting for 22.1% of the total area of the reserve. The elevation of the main utilisation area is 500-800 m, accounting for 48.53% of the total area of the reserve. The maximum slope utilised is 20°-30°, 30.19 km2 and accounting for 30.56% of the total area. The habitat used is largely distributed along valleys, preferred broad leaf forest, lower elevation, and close to rivers. Broad leaf forest is the main habitat type utilised, totalling 25.57 km2 and accounting for 37.19% of the total area. Our models predicted that the suitable habitat in the reserve is 62.46 km2, accounting for 20.08% of the total reserve area, with 32.93-km2 suitable habitat occurring in the core zone, 22.44 km2 in the buffer zone, and 7.02 km2 in the experimental zone. Our results indicate that only limited suitable habitat (51%) adverse reserve zoning exists in the Mayanghe Nature Reserve of François' langur.

A preliminary study on home range and daily travel distance of François' langur in a high-altitude area.

François' langur (Trachypithecus francoisi) is an indicator species living in Karst rocky habitats. To understand the François' langurs ecological adaptation to high-altitude habitat, we used the field tracking method to collect home-range data and daily travel distance of François' langur at high-altitude (800-1400 m) areas of Kuankuoshui National Nature Reserve between April 2008 and March 2009. The results revealed the following: (1) according to the grid cell method, the home range of François' langurs was estimated to be 50.7 ha. The area in the winter-spring season was larger than in the summer-autumn season (37.7 vs. 27.7 ha). According to the minimum convex polygon method by GIS, the home range of François' langurs in the winter-spring season and the summer-autumn season was 123.5 and 68.8 ha, respectively. The whole-year home range of François' was clearly larger than the grid cell method (140.4 vs. 50.7 ha). (2) The home range of François' langurs had clear superposition. Langur's core areas were concentrated in three small areas, which only occupied 18.2% of the home range. (3) The langur had a short daily travel distance (230-1115 m) and significant seasonal differences. The summer-autumn season moving distances being obviously shorter than the winter-spring season (517 vs. 785 m). (4) With the decrease in the availability of food resource in winter-spring season, the home range and daily travel distance of François' langurs significantly increased. (5) Living in the high altitudes, François' langurs tended to form a larger group (≥ 8 individuals), which is larger than other groups at lower altitude, had the larger home range, and had shorter daily travel distance. Our results indicate that colobines' survival strategies tend to form a larger home range and shorter day-traveling distance to adapt to high-altitude and low-temperature habitat.

Assessing the effects of survey-inherent disturbance on primate detectability: Recommendations for line transect distance sampling.

Habitat destruction and over-hunting are increasingly threatening the arboreal primates of Central Africa. To establish effective conservation strategies, accurate assessments of primate density, abundance, and spatial distribution are required. To date, the method of choice for primate density estimation is line transect distance sampling. However, primates fleeing human observers violate methodological assumptions, biasing the accuracy of resulting estimates. In this study, we used line transect distance sampling to study five primate species along 378 km of transects in Salonga National Park, Democratic Republic of the Congo. We tested the effect of different levels of survey-inherent disturbance (i.e., cutting) on the number of observed (i) primate groups, and (ii) individuals within groups, by counting groups at three different time lags after disturbance of the transect, (i) a minimum of 3 h, (ii) 24 h, (iii) a minimum of 3 days. We found that survey-inherent disturbance led to underestimated densities, affecting both the number of encountered groups and of observed individuals. However, the response varied between species due to species-specific ecological and behavioral features. Piliocolobus tholloni and Colobus angolenis resumed an unaltered behavior only 24 h after disturbance, while Lophocebus aterrimus, Cercopithecus ascanius, and Cercopithecus wolfi required a minimum of 10 days. To minimize bias in density estimates, future surveys using line transect distance sampling should be designed considering survey-inherent disturbance. We recommend evaluating the factors driving primate response, including habitat type, niche occupation, and hunting pressure, peculiar to the survey-specific area and primate community under study.

The importance of well protected forests for the conservation genetics of West African colobine monkeys.

In tropical forests, anthropogenic activities are major drivers of the destruction and degradation of natural habitats, causing severe biodiversity loss. African colobine monkeys (Colobinae) are mainly folivore and strictly arboreal primates that require large forests to subsist, being among the most vulnerable of all nonhuman primates. The Western red colobus Piliocolobus badius and the King colobus Colobus polykomos inhabit highly fragmented West African forests, including the Cantanhez Forests National Park (CFNP) in Guinea-Bissau. Both species are also found in the largest and best-preserved West African forest-the Taï National Park (TNP) in Ivory Coast. Colobine monkeys are hunted for bushmeat in both protected areas, but these exhibit contrasting levels of forest fragmentation, thus offering an excellent opportunity to investigate the importance of well-preserved forests for the maintenance of evolutionary potential in these arboreal primates. We estimated genetic diversity, population structure, and demographic history by using microsatellite loci and mitochondrial DNA. We then compared the genetic patterns of the colobines from TNP with the ones previously obtained for CFNP and found contrasting genetic patterns. Contrary to the colobines from CFNP that showed very low genetic diversity and a strong population decline, the populations in TNP still maintain high levels of genetic diversity and we found no clear signal of population decrease in Western red colobus and a limited decrease in King colobus. These results suggest larger and historically more stable populations in TNP compared to CFNP. We cannot exclude the possibility that the demographic effects resulting from the recent increase of bushmeat hunting are not yet detectable in TNP using genetic data. Nevertheless, the fact that the TNP colobus populations are highly genetically diverse and maintain large effective population sizes suggests that well-preserved forests are crucial for the maintenance of populations, species, and probably for the evolutionary potential in colobines.

Modifying the diets of captive proboscis monkeys in a temperate zoo to reduce weight loss and renal disease.

In animal husbandry, diets should help in maintaining a healthy body condition, support reproduction, and promote species-specific longevity. It is recommended to feed folivorous primates kept in zoos a high-fiber diet, i.e., leaves, although satisfying such a requirement is challenging in temperate regions because it is difficult to obtain fresh leaves, especially in autumn and winter. As equally important for their appropriate treatment, it is valuable to provide details of clinical reports of medical problems and pathological findings, although such clinical reports are rather limited. Therefore, in foregut-fermenting proboscis monkeys (Nasalis larvatus), we (1) described the individual clinical reports of renal disease and weight loss at the Yokohama Zoological Gardens in Japan, (2) determined the nutritional profile of the diets supplied to these animals because other potential triggers for their renal disease and weight loss could be excluded, (3) modified the diet regimen to minimize weight loss and the development of hypercalcemia and hypophosphatemia, and (4) assessed the effects of such dietary modification by comparing the body weight and the Ca and P concentrations and the Ca/P ratios in the blood before and after diet modification with a comparison of these measurements between zoo and free-ranging individuals. Based on the nutritional profile of the diets, we concluded that the reported cases of renal failure might be caused by consumption of leaves with a Ca/P ratio far above the appropriate level in autumn and winter. Additionally, the dietary modification of minerals and metabolizable energy achieved certain beneficial effects on zoo-kept proboscis monkeys.

Mixed-species association and a record of a hybrid offspring between Trachypithecus pileatus and Trachypithecus phayrei in Bangladesh.

The term mixed-species association has a broad range of definitions, from temporary foraging association to permanent group living. A mixed-species association mostly involves species from closely related taxa and is found in birds, mammals and fish. It ranges from passive association with little interaction to coordinated behavioural interactions between the group members of a mixed-species group. Mixed-species association can result in the production of hybrid offspring in the wild. In this study, we present, to the best of our knowledge, the first observational evidence of mixed-species association between the two threatened primate species Phayre's langur (Trachypithecus pileatus) and capped langur (Trachypithecus phayrei), in fragmented forest patches of northeast Bangladesh. We also report a presumed hybrid offspring between these species. We conducted a short-term study from December 2021 to April 2022 in three forest patches based on information from eco-tourism guides. We confirmed the presence of three mixed-species troops; in two of the groups an adult male T. phayrei had permanently immigrated into a group of T. pileatus, and in the other one an adult male T. pileatus had permanently immigrated into a group of T. phayrei. A long-term detailed study is needed to elucidate the reasons for these mixed-species associations, their behavioural patterns, the fate of the presumed hybrid offspring, and to understand the genetic relatedness between the individuals.