Search Results (60)

Alpha male replacement occurs in many group-living non-human primates, but its characteristics remain under-explored. Species of the genus Macaca live in multi-male, multi-female groups and are structured into four levels of social styles, which may impact alpha male replacement. Rhesus monkeys (Macaca mulatta) are classified as Grade 1, yet little is known about alpha male replacements in this species. This study investigated the occurrence and characteristics of alpha male replacements in rhesus monkeys inhabiting the southern end of Taihang Mountains, China. The types of alpha male replacements included succession (8/11), Rank Reversal (1/11), and Group Fission (2/11). The average age at which adult males took the alpha rank was 10.2 (±4.1, n = 11) years of age. Their average social rank prior to attaining alpha rank was 3.91 (±3.05, n = 11). The average tenure of alpha males after 2017 was 2.6 (±1.4, n = 5) years, which appeared shorter than that before 2017 (>7.5 ± 2.9 years, n = 4). The occurrence of alpha male replacements did not significantly correlate with group sizes, natality, the ratio of adult males to adult females, or the proportion of immatures. Compared with tolerant Macaca species, alpha male replacement in rhesus monkeys tend to be biased toward Succession, a pattern that may be linked to their extremely despotic social style. This study suggests that social style could interact with changes in social structure, deepening our understanding of the evolution of primate social systems. Full article

The common marmoset (Callithrix jacchus) is a New World Monkey that frequently serves as a model in biomedical research. Our knowledge of its anatomy is the fundament of the provision of the correct environment, housing, and care together with provision of accurate medical care in the case it gets wounded. In this anatomical research article, the focus is on the hand musculature, as it plays a pivotal role in the interaction with the environment and conspecifics. Surprisingly, anatomical works on the common marmoset are scarce. The available books and atlases are either outdated in terms of illustrations, providing only simplified line drawings, and/or fail to recapitulate the anatomy of the hand using contemporary anatomical nomenclature. The present work describes the myology of the hand, based on dissections of common marmoset cadavers. Color photographs taken during the subsequent steps of the examinations lead the reader through the textual descriptions. Dorsal and palmar views of the antebrachial muscles with influence on the wrist and hand as well as the intrinsic hand musculature are scrutinized. The findings are finally discussed in view of potential contradictions with the available literature. In addition, comparison is made with the rhesus monkey (Macaca mulatta) whose hand musculature was recently revisited. It is concluded that the hand musculature of both species is highly similar, although remarkable differences are present. This work could serve as an anatomical foundation for medical interventions of the injured hand. Full article

Comprehensive epidemiological reports on the incidence and pathogenicity of Yersinia spp., specifically Yersinia pseudotuberculosis and Yersinia enterocolitica, in rhesus macaques (Macaca mulatta) are not prevalent. Here we report findings from a retrospective analysis of microbial culture results, necropsy reports, and histology records collected over 24 years (2000–2024) in a large captive rhesus macaque colony at the Oregon National Primate Research Center (ONPRC). Findings are compared between animals infected with either Y. pseudotuberculosis or Y. enterocolitica to evaluate the prevalence of infection within the population and determine whether Y. pseudotuberculosis is more likely to be associated with systemic disease and higher mortality than Y. enterocolitica. Among 101 affected animals, Y. pseudotuberculosis was the predominant species (75.2%), followed by Y. enterocolitica (22.7%) and Y. kristensenii (2.0%). Overall mortality among animals with confirmed yersiniosis was 25.3%, with comparable mortality rates for Y. pseudotuberculosis (23.7%) and Y. enterocolitica (30.4%) infections. Y. pseudotuberculosis was most frequently associated with systemic illness, spontaneous death, or significant clinical decline. Overall, these findings emphasize the importance of continued surveillance and targeted management strategies to mitigate the impact of Yersinia infections in captive nonhuman primate colonies. Full article

The Jianfengling region on southwestern Hainan Island is a sanctuary for a diverse range of wild animals. However, the exact extent of mammal species diversity and conservation status in Jianfengling remains largely unknown. Using camera-trapping data spanning from October 2020 to November 2021, this study focused on the diversity and distribution status of mammal species in Jianfengling, Hainan Tropical Rainforest National Park, China. The survey, with 41,571 camera days and 8091 independent detections, revealed 15 mammalian species belonging to 6 orders and 10 families. Among these detected species, one was categorized as Critically Endangered, and one as Near Threatened on the IUCN Red List. According to the Red List of China’s Vertebrates, one was categorized as Critically Endangered, one as Endangered, three as Vulnerable, and three as Near Threatened. Additionally, one was designated China’s national first-class key protected wildlife, and five were designated China’s national second-class key protected wildlife. Notably, populations of the Chinese pangolin (Manis pentadactyla) were confirmed to persist in the wild of Jianfengling. Occupancy modeling results showed that the occupancy of Rhesus monkey (Macaca mulatta), Hainan muntjac (Muntiacus nigripes), common palm civet (Paradoxurus hermaphroditus), and Mainland leopard cat (Prionailurus bengalensis) increased with increasing elevation. Vegetation type would only affect the occupancy of the Rhesus monkey. Normalized Difference Vegetation Index and anthropogenic activities had no obvious effect on the occupancy of mammals. In terms of the relative abundance index (RAI) of mammals captured by camera traps, the most prevalent species identified was the Asiatic brush-tailed porcupine (Atherurus macrourus), followed by the wild boar (Sus scrofa), Pallas’s squirrel (Callosciurus erythraeus), and Hainan muntjac. The monitoring also captured a significant number of images of domestic dogs and humans. These findings establish a baseline for species richness and occupancy of mammals in a typical island tropical rainforest in Hainan Tropical Rainforest National Park. We hope that our findings could be used to assess the effectiveness of conservation monitoring programs in the coming years, as species richness surveys provide an important baseline for conservation planning. Full article

The rhesus macaque (Macaca mulatta) is a valuable model for pregnancy research due to its physiological similarity to humans and the ability to conduct studies in a controlled environment. Our previous work used non-invasive imaging methods to assess placental hemodynamics across gestation with correlative tissue analysis post-delivery. Here, we expand access to longitudinal timepoints from ongoing pregnancies by obtaining placental biopsies using ultrasound-guided needle aspiration. This approach aligns with New Approach Methods (NAMs) and supports animal welfare by reducing the number of animals required. We describe a chorionic villus sampling (CVS) simulation model which facilitates training to gain proficiency in technical skills prior to performing the procedure on animals. We report outcomes from three rhesus macaques that underwent CVS three times between gestational days 40 to 106 (term: 165 days). Although biopsy samples are smaller than whole placenta, tissue yields were sufficient for multiple uses. We demonstrate (1) appropriate histology from aspirated samples, (2) good RNA quality and yield, and (3) the ability to isolate trophoblast organoids, an advancement in NAMs that reduces the need for first-trimester surgical delivery. No spontaneous preterm delivery occurred following serial CVS procedures, supporting the use of this sampling method to maximize animal utilization in longitudinal pregnancy studies. Full article

Background/Objectives: Traumatic spinal cord (SC) injury (SCI) is a debilitating neurological condition. Minimally invasive approaches to monitor in real time the functional state of the neuromotor apparatus in animal models of SCI (at rest and movement) to assess effectiveness of therapy are needed in preclinical studies. We aimed to develop such a bioethically acceptable platform for SCI studies on non-human primates (Rhesus macaques). Methods: Epidural and myographic electrode implantation (EI) (wireless and wired, connected via a head plug) was performed. After EI, motor responses caused by electrical stimulation of the SC at the level of the cervical and lumbar thickening were recorded; electromyography of the limb muscles was recorded during quadrupedal movement of the animal on a treadmill with simultaneous assessment of movements’ kinematic parameters. Five weeks after EI, three animals underwent lateral hemisection of the SC in the C4–C5 segment under the control of a surgical microscope and intraoperative recording of motor- and sensory-evoked potentials. Results: Within 30 days after SCI, during treadmill testing, a decrease in electromyographic activity of the limb muscles and the volume of angular movement in the joints on the side of the injury was detected. Electrical stimulation at the L2–S1 segments of the SC at a frequency of 30 Hz led to the appearance of a locomotor pattern in the muscles of the hind limbs and an increase in the range of motion. Conclusions: Our platform can be used for pathophysiological studies of various neuromodulation modes and as a basis for the development of control neurointerfaces. Full article

Emesis is one of the most common side effects of ketamine sedation; however, predictors like species and sex have not been studied in macaques. This study aimed to determine the incidence and predictors of emesis in macaques undergoing ketamine sedation and to assess the efficacy of orally administered antiemetics in preventing emesis. A retrospective analysis was performed using medical records from rhesus and cynomolgus macaques who received ketamine sedation for veterinary examination events from August 2023 to April 2024. Among the 70 sedations performed using IM ketamine, the overall incidence of emesis was 26%. Cynomolgus macaques had a significantly higher risk of emesis (odds ratio (OR) 46.14, 95% confidence interval (CI): 7.08–493.9; p < 0.0001), with an emesis incidence of 55%. Females showed a higher incidence of emesis (75%) with an odds ratio of 3.72 (95% CI: 0.55–17.91; p = 0.24), though this difference was not statistically significant. In a prospective, randomized study, we compared the prophylactic use of oral maropitant citrate at a dose of 2 mg/kg or oral ondansetron at a dose of 1 mg/kg versus placebo for the prevention of emesis in cynomolgus macaques undergoing veterinary examination. Emesis was reduced from 58% in the control group to 50% in the maropitant group and 33% in the ondansetron group. However, the reduction in relative risk with either treatment did not reach statistical significance. Prophylactic oral administration of maropitant appears ineffective in preventing emesis in cynomolgus macaques. In contrast, prophylactic oral ondansetron is a more effective alternative in preventing emesis in these animals. Full article

The gut microbiota of macaques, highly homologous to humans in biological characteristics and metabolic functions, serves as an ideal model for studying the mechanisms of human intestinal diseases and therapeutic approaches. A comprehensive characterization of the macaque gut microbiota provides unique insights into human health and disease. This study employs metagenomic sequencing to assess the gut microbiota of wild M. mulatta brevicaudus across various ages, sexes, and physiological states. The results revealed that the dominant bacterial species in various age groups included Segatella copri and Bifidobacterium adolescentis. The predominant bacterial species in various sexes included Alistipes senegalensis and Parabacteroides (specifically Parabacteroides merdae, Parabacteroides johnsonii, and Parabacteroides sp. CT06). The dominant species during lactation and non-lactation periods were identified as Alistipes indistinctus and Capnocytophaga haemolytica. Functional analysis revealed significant enrichment in pathways such as global and overview maps, carbohydrate metabolism and amino acid metabolism. This study enhances our understanding of how age, sex, and physiological states shape the gut microbiota in M. mulatta brevicaudus, offering a foundation for future research on (1) host–microbiome interactions in primate evolution, and (2) translational applications in human health, such as microbiome-based therapies for metabolic or immune-related disorders. Full article

The ecological drivers of wildlife crop-foraging behavior—whether as a compensatory response to natural resource scarcity or as opportunistic exploitation of anthropogenic food sources—remain poorly understood in human–wildlife conflict research. Traditional methodologies, which primarily rely on direct observation and morphological identification, have limitations in comprehensively quantifying wildlife dietary composition, particularly in accurately distinguishing between morphologically similar plant species and conducting precise quantitative analyses. This study utilized DNA metabarcoding technology (rbcL gene markers) to identify and quantify plant dietary components through fecal sample analysis, systematically investigating the dietary composition and patterns of agricultural resource utilization of wild rhesus macaques (Macaca mulatta) in human–wildlife interface zones of southwestern China. A total of 29 rhesus macaque fecal samples were analyzed (15 from spring and 14 from winter), identifying 142 plant genera, comprising 124 wild plant genera, and 18 crop genera. The results revealed distinct seasonal foraging patterns: crops accounted for 32.11% of the diet in winter compared to 7.66% in spring. Notably, rhesus macaques continued to consume crops even during spring when wild resources were relatively abundant, challenging the traditional hypothesis driven by resource scarcity and suggesting that crop-foraging behavior may reflect an opportunistic, facultative resource selection strategy. This study demonstrates the significant value of DNA metabarcoding technology in wildlife foraging behavior research, providing scientific evidence for understanding human–primate conflict ecology and developing effective management strategies. Full article

Rhesus macaque (Macaca mulatta), the iconic species of genus Macaca, is characterized by the greatest geographical distribution of all nonhuman primates and is an important resource in many wildlife-related tourism areas, especially in China. In the current study, the genetic diversity was assessed by ten microsatellite loci with DNA obtained from muscle tissue of deceased individuals of free-ranging but tourist-habituated rhesus population naturally inhabiting the Wulongkou Scenic Area, Jiyuan, China, where they have been exploited for tourism since the early 1980s. The results showed that the genetic diversity for the studied rhesus population was relatively lower compared with its wild and captive counterparts, and the samples collected from the population subdivision in the studied area could mask the finding. Therefore, we proposed that a group-based study of the genetic diversity would help to clarify the genetic structure/diversity of rhesus macaques in this area, and then reasonable management recommendations could be provided for the sustainable development of local wildlife-dominated tourism. Full article

Anesthesia protocols in laboratory-held rhesus macaques (Macaca mulatta) are well described, but fewer reports exist in zoo, safari park or field environments. This study recorded and compared the level of sedation, heart rate (HR), respiratory rate (RR), and induction and recovery times of ketamine–medetomidine (KM), ketamine–dexmedetomidine (KD) and ketamine–xylazine (KX) protocols in ninety-five safari-park-managed rhesus macaques. In total, 31 animals received the KM protocol, which included 25 mg ketamine (6.08 ± 1.54 mg/kg) and 0.15 mg medetomidine (0.04 ± 0.01 mg/kg); 33 animals received the KD protocol, which included 25 mg ketamine (6.19 ± 2.42 mg/kg) and 0.08 mg dexmedetomidine (0.02 ± 0.01 mg/kg); and 31 animals received the KX protocol, which included 50 mg ketamine (12.64 ± 3.79 mg/kg) and 1.2 mg xylazine (0.30 ± 0.09 mg/kg). Anesthesia was reversed with atipamezole. The mean bodyweight of the study population was lower than expected, so actual doses were higher than intended; no adverse effects were reported. Induction and recovery times were longer for KX than KD or KM (p < 0.05) but did not differ significantly between KD and KM (p > 0.05). HR and RR did not differ between protocols (p > 0.05). Sedation score was negatively correlated with bodyweight, and mean sedation score was lower for KX than KM or KD. KD and KM provided more rapid and reliable sedation than KX at the doses described; however, alterations in the KX dose may improve reliability. Full article

The rhesus monkey (Macaca mulatta) is a non-human primate with a genome that is 93.5% identical to that of humans. Both species, therefore, have numerous phenotypical similarities in common. Consequently, this non-human primate is regularly studied in biomedical research. Not only does the rhesus monkey play an important role as an animal model for studying human disease, but it is also often featured in zoos, and there are substantial feral populations that live in Asia. Since they are exploited as research subjects, their appropriate housing and husbandry and the validation of obtained research data benefit from the comprehension of the rhesus monkey anatomy. Unexpectedly, the number of anatomical documents on the rhesus monkey are largely outnumbered by publications on the anatomy of domestic animals. In addition, the limited number of available anatomical books and atlases are, unfortunately, outdated, e.g., by presenting black-and-white photographs and using archaic nomenclature, or failing to cover the in-depth anatomy of various anatomical systems. Since state-of-the-art data on the rhesus monkey anatomy are requested by biomedical researchers and veterinarians responsible for the daily care of these captive animals, the present study describes the musculature of the foot of the rhesus monkey. It builds on a recently published manuscript on the topographical anatomy of the pelvic limb of this non-human primate. Full-color anatomical (stereomicroscopic) photographs are taken during layer-by-layer dissections of the feet of three rhesus monkeys. All the muscles, from the superficial to the deepest layer, are described using veterinary anatomical nomenclature and annotated on multipaneled figures. Although the foot musculature of the rhesus monkey largely parallels that of its human counterparts, the small number of dissimilarities should be recognized when extrapolating these research data. In addition, a solid understanding of the rhesus monkey anatomy by veterinarians can be valuable during medical interventions, such as surgery for foot injuries. Full article

Research facilities have established animal adoption programs for laboratory animals. However, adoption to private owners is not an option for non-human primates (NHPs), so their post-research life presents a unique challenge. Here, we describe a collaborative effort between laboratory animal veterinarians and behavioral management staff in retiring NHPs in place to ensure their quality of life after the completion of research projects. The success of our retirement program hinges on our collaborative efforts to manage clinical diseases such as arthritis, amyloidosis, and diarrhea; to surgically ex-plant previous research hardware; and to evaluate the animals’ behavior and temperament to ensure each individual is placed in a new group or living situation in which they are likely to be successful and to have good welfare. Implementation of a quality-of-life assessment tool for all retired animals allows all staff involved in the animals’ care to proactively and periodically assess the quality of life of these animals. The successful retirement of NHPs living in social groups is rewarding for all personnel and promotes a culture of caring. Research animal retirement is an important way for us to give back and honor the contributions these animals have made to advancing medicine. Full article

Temporal and spatial factors regulate the interactions between apex predators, mesocarnivores, and herbivores. Prey adjust their activity patterns and spatial utilization based on predator activities; in turn, predators also adapt to the activities of their prey. To elucidate the factors influencing the daily activity rhythms of animals, 115 camera traps were established from September 2019 to June 2023 to assess the influences of interspecific relationships and seasons on the daily activity rhythms of animals in the southwest mountains of China. The species captured by the cameras included six Carnivora (such as Panthera pardus and Lynx lynx), six Artiodactyla (such as Moschus spp. and Rusa unicolor), one Primate (Macaca mulatta), and two Galliformes (Crossoptilon crossoptilon, Ithaginis cruentus). The results demonstrated that the 15 species exhibited different activity rhythms and peak activities to reduce intense resource competition. There were differences in the species’ activity rhythms in different seasons, with competition among different species being more intense in the cold season than in the warm season. In predation relationships, the overlap coefficient in the cold season exceeded that of the warm season, possibly due to the abundant resources in summer and food scarcity in winter. In competitive relationships, 15 pairs of species exhibited significantly higher overlap coefficients in the cold season compared to the warm season, possibly due to increased demands for energy during the cold period or seasonal changes in predatory behavior. By analyzing the daily and seasonal activity patterns of dominant species in the study area, temporal niche overlaps were established to compare the competition levels between species. These findings indicate that the activity rhythms of the animals in this area not only result from evolutionary adaptation but are also influenced by season, food resources, and interspecific relationships (predation and competition). Thus, efforts should be made to reduce human interference, protect food resources in the winter, and monitor animals’ interspecific relationships to protect animal diversity and maintain the stability of the ecosystem in this biodiversity hotspot in China. Full article

Background. Influenza and SARS-CoV-2 viruses are two highly variable pathogens. We have developed a candidate bivalent live vaccine based on the strain of licensed A/Leningrad/17-based cold-adapted live attenuated influenza vaccine (LAIV) of H3N2 subtype, which expressed SARS-CoV-2 immunogenic T-cell epitopes. A cassette encoding fragments of S and N proteins of SARS-CoV-2 was inserted into the influenza NA gene using the P2A autocleavage site. In this study, we present the results of preclinical evaluation of the developed bivalent vaccine in a non-human primate model. Methods. Rhesus macaques (Macaca mulatta) (n = 3 per group) were immunized intranasally with 7.5 lg EID₅₀ of the LAIV/CoV-2 bivalent vaccine, a control non-modified H3N2 LAIV or a placebo (chorioallantoic fluid) using a sprayer device, twice, with a 28-day interval. The blood samples were collected at days 0, 3, 28 and 35 for hematological and biochemical assessment. Safety was also assessed by monitoring body weight, body temperature and clinical signs of the disease. Immune responses to influenza virus were assessed both by determining serum antibody titers in hemagglutination inhibition assay, microneutralization assay and IgG ELISA. T-cell responses were measured both to influenza and SARS-CoV-2 antigens using ELISPOT and flow cytometry. Three weeks after the second immunization, animals were challenged with 10⁵ PFU of Delta SARS-CoV-2. The body temperature, weight and challenge virus shedding were monitored for 5 days post-challenge. In addition, virus titers in various organs and histopathology were evaluated on day 6 after SARS-CoV-2 infection. Results. There was no toxic effect of the immunizations on the hematological and coagulation hemostasis of animals. No difference in the dynamics of the average weight and thermometry results were found between the groups of animals. Both LAIV and LAIV/CoV-2 variants poorly replicated in the upper respiratory tract of rhesus macaques. Nevertheless, despite this low level of virus shedding, influenza-specific serum IgG responses were detected in the group of monkeys immunized with the LAIV/CoV-2 bivalent but not in the LAIV group. Furthermore, T-cell responses to both influenza and SARS-CoV-2 viruses were detected in the LAIV/CoV-2 vaccine group only. The animals were generally resistant to SARS-CoV-2 challenge, with minimal virus shedding in the placebo and LAIV groups. Histopathological changes in vaccinated animals were decreased compared to the PBS group, suggesting a protective effect of the chimeric vaccine candidate. Conclusions. The candidate bivalent vaccine was safe and immunogenic for non-human primates and warrants its further evaluation in clinical trials. Full article