American Journal of Primatology最新文献

The perception of sweet taste, which is dominantly mediated by the heterodimeric sweet taste receptor composed of two subunits T1R2 and T1R3 (taste receptor type 1 member 2 and taste receptor type 1 member 3), is crucial for the diet of primates. However, there are only a small number of primate species (primarily non-hominid such as New World monkeys and lemuriforms) whose sweet taste receptors have been functionally identified until now. In this study, we characterized the sweet taste receptor T1R2/T1R3 of a hominid species, chimpanzees, humans' closest living relative, a primate. Although the activities and responses of chimpanzee T1R2/T1R3 are mostly comparable to those of human T1R2/T1R3, an obvious discrepancy in sensitivity is revealed between T1R2s/T1R3s of human and chimpanzee toward a variety of sweeteners, including natural and artificial sweet compounds. Moreover, the difference in sweet taste between humans and chimpanzees could be associated with variation in the sequence and structure of their sweet taste receptors. These results serve as a meaningful basis for further exploring the molecular mechanism of sweet taste as well as its evolution in primates.

Degenerative changes of the vertebral column are common in aging primates; however, patterns of spinal osteopathy remain poorly characterized across small- and medium-bodied primate species, limiting comparative interpretations of skeletal aging. Expanding assessments beyond well-studied taxa provides a broader framework for understanding primate musculoskeletal senescence and generates baseline data essential for interpreting vertebral degeneration in wild and semi-free-ranging populations, where ecological and life-history factors influence skeletal aging. We investigated age-, sex-, and body mass-related variation in vertebral osteopathies radiographically assessed in 70 captive vervet monkeys (Chlorocebus aethiops). Osteophytes were the most frequent lesion (78.6%), followed by discopathy (12.7%), syndesmophytes (2.9%), and scoliosis (1.4%). Age was the primary predictor of osteophyte presence across spinal regions, whereas sex and body mass showed no significant independent effects. In contrast, total osteophyte scores were significantly higher in older, heavier individuals, and females exhibited slightly higher adjusted scores than males. Nonlinear regression models revealed distinct age-related trajectories among spinal regions, with osteophytes emerging earliest in the lumbar spine (~ 1 year), followed by the cervical (~ 7 years) and thoracic (~ 9 years) regions. These findings characterize the natural history of spinal degeneration in vervet monkeys under captive conditions and provide comparative baseline data for distinguishing age-related changes from pathological alterations in both captive and free-ranging primate populations.

Human-driven habitat change is forcing nonhuman primates to exploit anthropogenic landscapes, resulting in primate crop feeding, reduced farmer food security, and human-primate conflict. Here, we investigate the crop feeding behavior of a wild group of rhesus macaques in a farm-forest mosaic in central Nepal. Macaque behavioral data were collected over 12 months using scan- and all-occurrence sampling methods, along with monitoring crop availability. We evaluated the relationship between macaque feeding behavior, crop type, availability, damage, and farmers' actions to reduce crop damage. We found that ~49% of the macaque's annual diet was composed of cultivated crops, with three crops-maize, oranges, and potatoes-accounting for ~52% of macaque crop feeding time. There was a significant positive association between monthly crop productivity and macaque feeding time on these crops. Local farmers attempted to deter macaque crop feeding 83.1% of the time, but their efforts failed to reduce crop damage. During the maize cultivation season, total maize damage caused by macaques was estimated at 1647 kg (~50 kg/ha) of dry kernels, resulting in a loss of 1.5% of total maize yield per hectare. Thus, macaque crop feeding had only a limited effect on farmer food security. We propose a set of practical and low-cost actions that can be taken to continue the current balance between the dietary needs of the rhesus macaques and the economic needs of farm families in the local community.

Rodent models have provided a detailed body of knowledge on craniodental development. Yet, it is unknown how well altricial mammals such as mice parallel primate and specifically human craniodental development. To address this, here we document the ontogeny of jaw-related structures in a cross-sectional prenatal sample of mouse lemurs (Microcebus spp.). Mouse lemurs follow the same developmental sequence as humans and mice with respect to the earliest appearance of jaw structures. Meckel's cartilage forms before any membranous bone of the mandibular body; mandibular basal bone begins to ossify before teeth enter the bud stage. Lower jaw structures commence morphogenesis before the corresponding maxillary elements. The basal bone of both jaws becomes more complex in larger fetuses. As tooth germs mature, the follicle-a supporting connective tissue outside the papilla and enamel organ-matures into a cellular, loosely fibrous tissue. Surrounding the follicle is a sheet-like connective tissue, the epifollicular membrane. In tooth germs reaching the bell stage, alveolar bone forms within this membrane. One subtle distinction of mouse lemurs to prior descriptions of fetal anthropoids is the lemur's faster maturation of the deciduous canine compared to incisors, the reverse of the anthropoid pattern. However, broadly it appears that all primates studied thus far have a very prolonged duration of dental maturation, which continues long after other facial elements (e.g., hard palate) are fully formed. This scenario contrasts with altricial rodents, in which palate formation occurs near parturition, and only a day before the first permanent molar reaches the bell stage.

Global urbanization of nonhuman primate (hereafter primate) habitats is rapidly increasing the overlap between human and primate populations, often resulting in more frequent and complex human-primate interactions. While such interactions have been extensively documented for several terrestrial primate species, interactions are increasingly occurring with arboreal species, especially in highly urbanized touristic destinations. Here, we describe how the rapid expansion of urban and linear infrastructure (e.g., roads, railways) in the forested areas of the state of Quintana Roo, Mexico, is affecting local Geoffroy's spider monkey (Ateles geoffroyi) populations and reshaping human-monkey interactions. Although human-spider monkey interactions are rarely aggressive, the increasingly close contact between people and monkeys poses serious ecological effects, including changes in spider monkey behavior and diet, as well as increased potential for disease transmission and illegal primate trade. Examples from Quintana Roo, however, demonstrate that coexistence is possible through well-enforced no-feeding policies, participatory monitoring of spider monkey populations, and the integration of ecological data into urban and tourism planning. Our aim is to highlight the urgent need for (1) thoughtful, evidence-based coexistence strategies as cities continue to expand into primate habitats and (2) primatologists, conservationists, urban planners, and policymakers to play an active role in integrating primate ecology into land-use and tourism policies to ensure the long-term persistence of primates and the socio-ecological systems they inhabit.

Nonhuman primates constitute an ideal model to study the evolutionary origins of human language, because of their close phylogenetic distance to humans and their reliance on complex communication systems that include different signal types. In this study, we investigated the vocal repertoire of Macaca maura (moor macaques), a highly tolerant primate species endemic to Sulawesi, Indonesia. We conducted detailed acoustic analyses on 1116 high-quality vocalizations recorded from a well-habituated wild group of 42 individuals. Using discriminant function and random forest analyses, we found that moor macaques show a graded vocal repertoire, with considerable acoustic overlap between several call types and a high number of acoustic parameters needed for accurate classification. These findings were supported by the failure of unsupervised clustering to detect robust categorical structures beyond a two-cluster solution. Our findings provide novel insights into the vocal behavior of a yet understudied species, and provide preliminary evidence that moor macaques show graded communication systems.

Infanticide is understood as any direct or indirect behavior that fatally harms an infant, regardless of whether the perpetrator gains benefits. In non-human primates, males are frequently identified as the perpetrators. Classical studies categorized behaviors like "abuse", "fatal neglect", "kidnapping", and "aunting to death" as forms of infanticide when they resulted in infant death. However, in more recent literature, some of these behaviors are excluded from classifications of infanticide without clear justification, particularly those involving female-related lethal actions. Therefore, we conducted a systematic review spanning 54 years to investigate potential sex biases in primate infanticide literature. Our findings show that female actions leading to infant death are often labeled with terms like "abuse" and "fatal neglect". In contrast, similar male behaviors are consistently classified as infanticide. As a result, infanticide by non-human primate females has been systematically underreported. Classifying all lethal behaviors by females toward infants as infanticide eliminates the sex difference in the frequency of such acts. Our study shows that being consistent with the original definition of infanticide for non-human primates provides a more accurate understanding of infanticide in these animals. Thus, we strongly recommend adhering to the infanticide definition, which integrates the recorded behaviors into established theoretical frameworks, enabling more comprehensive discussions of primate infanticidal behavior.

Recent advances in deep learning and transfer learning have revolutionized our ability for the automated detection of acoustic signals from long-term soundscape recordings. Effective automated detection approaches can vastly improve our ability to monitor endangered species, like gibbons. Here, we provide a benchmark for the automated detection of female duet contributions from southern yellow-cheeked crested gibbons (Nomascus gabriellae) recorded in Jahoo, Cambodia. For the benchmarking, we compared the performance of support vector machines (SVMs), a quasi-DenseNet architecture (Koogu), transfer learning with ResNet50 models trained on the "ImageNet" dataset (ResNet), and transfer learning with embeddings from a global birdsong model (BirdNET). Transfer learning models based on BirdNET embeddings had superior performance with a smaller number of training samples, whereas Koogu and ResNet50 models only had acceptable performance with a larger number of training samples (> 200 gibbon samples). We deployed the BirdNET-based model over > 130,000 h of continuous soundscape data, which, after manual review, resulted in > 12,000 verified true positive detections. We found that female gibbon calling events occurred mostly in the early morning hours between 05:00 and 06:00 local time. We had fewer gibbon detections during the monsoon period and found substantial variation in spatial patterns of calling events across months and years that may reflect territorial dynamics of gibbon groups. Reliable automated detection approaches are a critical first step for using passive acoustic monitoring to assess endangered gibbon populations at ecologically relevant temporal and spatial scales.

Climate change and anthropogenic disturbances are significant factors influencing primate distributions and habitat conditions. This study evaluates the influence of climatic and anthropogenic factors on habitat suitability for six macaque species in Thailand: long-tailed macaque (LTM), Rhesus macaque (RSM), stump-tailed macaque (STM), Assamese macaque (ASM), northern pig-tailed macaque (NPM), and Sunda pig-tailed macaque (SPM). Habitat suitability was predicted through Maxent-based species distribution models (SDMs), which integrated bioclimatic and anthropogenic predictors. Occurrence data were collected from field surveys conducted between 2005 and 2025, literature, and citizen science data. The macaque habitat, anthropogenic dependence, and coexistence (MAC) framework was utilized to evaluate habitat quality (HQ). Hierarchical clustering was employed to analyze environmental niche similarities based on variable contribution profiles. Most SDMs exhibited moderate to high discriminatory ability, indicated by a test AUC > 0.7, with the SPM displaying the highest level of consistency. Thermal variables were predominant for the ASM and NPM; temperature seasonality was the primary factor for the RSM and STM, while precipitation influenced the SPM distribution. Anthropogenic factors, particularly artificial light at night (ALAN), significantly impacted the LTM. Hierarchical clustering revealed three distinct clusters. The HQ assessments indicated that the SPM and STM were associated with high-quality, natural forest habitats, whereas the LTM and RSM were primarily correlated with human-modified landscapes. Predicted suitable habitats are extensive for the NPM, STM, and LTM but are increasingly restricted for the ASM, RSM, and SPM. The findings offer comprehensive insights to facilitate monitoring, habitat management, and conservation planning for macaques in Thailand.

A multicenter study was undertaken to generate new weight-for-age growth standards to monitor the growth of infant rhesus and pigtail macaques in research breeding colonies. Previously, single institutions have developed reference growth curves, under the assumption of linear growth, for infants raised in certain settings with a limited scope of benefit to outside institutions. Weight and health records from seven research institutions across the USA were used to build models of body weight by age. Linear and Box-Cox Power Exponential (BCPE) distribution models, which have been adopted from the World Health Organization's methods, were compared to find the best fit of the models. Resultant weight percentiles and growth velocity charts were provided from the best-fit model ranked by generalized Akaike's information criterion. Multiparameter models with the BCPE distribution fit the data better than linear models with normal distributions. The assumption that infant macaque growth is linear was challenged by our findings; growth rates appear to change over the first year of life for infant macaques. Growth standards were integrated into centile charts and a computer application in MS Excel to provide user-friendly weight-for-age percentile charts to access and analyze macaque growth data. The new growth standards provide a unified reference that best represents normal physiological growth for all infant rhesus and pigtail macaques from birth through the first year of life. These standards offer guidance on expected growth trajectories and serve as a benchmark for assessing the healthy development of macaque infants across research breeding colonies.