Primates最新文献

Taxonomic classifications of the gracile capuchin monkeys, Cebus, have traditionally been based on cranio-dental and pelage characters. Advances in molecular biology have provided information on the evolutionary history of the genus but the taxonomy and distribution limits of taxa in the northern Andes are still under debate. To assess morphometric disparities and compare the results with hypotheses based on genetic evidence for Cebus taxonomy, we used 2D geometric morphometrics on 206 adult specimens (127 males, 77 females, 2 unsexed) belonging to 12 taxa by assigning Type I landmarks in the frontal (11), lateral (18) and ventral (16) views of the skull, and 14 in the mandible. Our results show that skull shape is more variable than centroid size and that morphometric disparities exist across and within all three geographic groups (Central America, Andes, and Amazon). Although skull shape in Cebus tends to vary slightly, our results suggest differences among some taxa and highlight the utility of studying shape in addition to methods that have focused on size. Some results concur with the taxonomic classifications based on molecular evidence but it is important to note that Cebus species are wide-ranging with high inter- and intraspecific phenotypic variability in diverse ecological conditions. This makes it difficult to provide species diagnoses based just on morphometric or morphological characters and suggests the need to integrate different sources of evidence to resolve uncertainties about the taxonomy and the evolutionary relationships in the genus.

Interspecies interactions present diverse forms and functions, contributing significantly to ecological and social dynamics. This study focuses on the mounting behaviours of Japanese macaques (Macaca fuscata) towards Sika deer (Cervus nippon), a rare and still unexplained phenomenon, with minimal emphasis on the behaviour of the deer. Using video data from two distinct sites, Yakushima and Minoh, Japan, we documented 45 sequences of macaque-deer interactions and analysed macaques' behaviours and deer behaviours using focal and behavioural sampling techniques. We identified four primary activities performed by macaques during mountings-sexual, play, grooming, and resting-with resting being predominant. The study evaluates six hypotheses regarding the functions of these mounting behaviours: (1) interactions are sex-specific, (2) macaques use deer for transportation, (3) mutual warming through physical contact occurs, (4) deer provide support for resting, (5) macaques engage in grooming to consume parasites or play to strengthen interspecies bonds, and (6) aggressive signals relate to resource disputes or rejection of mounting behaviour. Statistical analyses using the Kruskal-Wallis test and Dunn's post-hoc test revealed significant differences between resting and other active behaviours, but no significant differences in behaviour duration between lying and sitting positions. Adults engaged in mounting for longer periods than juveniles, suggesting potential age-related differences in social and reproductive roles. These findings enhance our understanding of interspecies interactions by focusing on macaque behaviours and emphasise the need for longitudinal studies to clarify the ecological and social implications of these interactions.

Gibbons, a type of lesser ape, are brachiators but also walk bipedally and without forelimb assistance, not only on the ground but also on tree branches. The arboreal bipedal walking strategy of the gibbons has been studied in previous studies in relation to two-dimensional (2D) kinematic analysis. However, because tree branches and the ground differ greatly in width, leading to a constrained foot contact point on the tree branches, gibbons must adjust their 3D joint motions of trunk and hindlimb on the tree branches. Furthermore, these motor adjustments could help minimize the center of mass (CoM) mediolateral displacement. This study investigated the kinematic adjustment mechanism necessary to enable a gibbon to walk bipedally on an arboreal-like substrate using 3D measurements. Trials were recorded with eight video cameras that were placed around the substrate. The CoM position on the body, the Cardan angles of the hindlimb joints and trunk, and spatiotemporal parameters were calculated. Asymmetry of thorax, pelvis, trunk, and left and right hindlimb joint motion was observed in the pole and flat conditions. In the pole condition, the narrower step width and the smaller range of motion of the mediolateral CoM displacement were observed with increased hip adduction and knee eversion angles. These kinematic adjustments might place the knee and foot directly under the body during the single support phase, producing a reduced step width and the amount of the mediolateral CoM displacement of a gibbon.

Industrial expansion has brought humans and wildlife into closer contact, and added novel, complex dimensions to human-wildlife relationships. The seven great apes (chimpanzee, Bornean orangutan, Sumatran orangutan, Tapanuli orangutan, Eastern gorilla, Western gorilla, bonobo), the closest extant relatives to humans, have experienced substantial population declines resulting from anthropogenic activities. The effect of human activity on great ape behavioural ecology is therefore an emerging field of inquiry in primatology which has historically been minimally considered. This review explores how wild great apes respond behaviourally to human activities and environmental changes, synthesizing current knowledge and addressing potential outcomes and risks. Using precise search criteria, we found 96 studies documenting changes in great ape behaviour in response to human activity, and despite their broad geographic distribution, we found common patterns and responses across species to increasing human influence. Literature documented shifts in existing behaviour (57), the generation of novel behaviours (53) or reported both (15). Forty-three studies (45%) included direct (23) or indirect (20) assessment of the consequences of these behaviours. Only one study modelled a widespread loss of existing behaviours. The majority of studies included chimpanzees (67), followed by orangutans (19) and gorillas (19), and only 2 included bonobos. We found that the most frequently documented drivers of behavioural responses to anthropogenic activity were wide-scale land-use conversions in ape habitats. In response, apes have adopted crop foraging, and altered nesting behaviour, range use, and social strategies. While these responses appear to allow survival in the immediate sense, they may expose individuals to more risks in the long term. Analysis revealed that under many contexts changing great ape behaviour is putting strain on the human-ape relationship, resulting in injury, harassment, and even the killing of apes. We found examples of tolerant relationships between humans and apes shifting towards conflict, potentially worsening the conservation crisis and inviting inquiry into tolerance thresholds among human communities. We emphasize the importance of community-engaged strategies for reducing competition over resources and conclude that great ape behavioural responses to human activity must be interpreted through a locally specific lens.

The use of complex technologies by humans (Homo sapiens) and their ancestors is a key feature of our evolution, marked by the appearance of stone tools 3.3-million years ago. These technologies reflect cognitive complexity and an advanced understanding of materials and mechanics. Studying current primates, especially those that use stones, offers insights into the evolution of human behaviours. In particular, stone manipulation by macaques suggests that some complex behaviours in humans, such as creation of cutting and biface tools, could have emerged unintentionally. The Japanese macaques (Macaca fuscata) of Shodoshima were observed to leave marks on the ground with stones and chalk. By analysing this manipulation of stones, I suggest that drawing in humans could have appeared unintentionally; these unintentional origins of mark-making behaviours may represent early precursors to human drawing.

Huddling behaviour is present in many animal species. This behaviour involves maintaining close physical contact with conspecifics to minimise heat loss and, in general, reduce energy expenditure. Additionally, this behaviour also facilitates complex social interactions within a population. In Japanese macaques, this behaviour is observed in many populations across Japan, including Shodoshima, where huddling clusters can reach up to 100 individuals in winter. Based on several studies on this species, it appears that huddling, or sarudango in Japanese, is influenced by both meteorological factors and social relationships between individuals. The objective of this study is to understand the determinants that drive the expression (presence or absence) and the organisation (number of individuals and identities) of huddling clusters. Two hypotheses were formulated. The first hypothesis posits that the formation and variations in the size and number of clusters are influenced by meteorological factors, while the second hypothesis suggests that the number and position of individuals within a cluster are related to existing relationships between individuals. To test these, data on the number, size, and individuals composing a cluster were collected, allowing building huddling social networks. Simultaneously, meteorological measurements were taken, along with observations on dominance and grooming interactions between individuals. This allowed us to create several statistical models and social networks for comparison. Our results suggest that the probability for observing huddling is mainly related to solar radiation energy, while variations in number and size could be explained by temperature. Moreover, the organisation within a cluster is not random but reflects relationships between individuals. The ones sharing more grooming and having similar dominance ranks have more probabilities to be in the same huddling cluster.

Drawings serve as a profound medium of expression for both humans and apes, offering unique insights into the cognitive and emotional landscapes of the artists, regardless of their species. This study employs artificial intelligence (AI), specifically Convolutional Neural Networks (CNNs) and the interpretability tool Captum, to analyse non-figurative drawings by Molly, an orangutan. The research utilizes VGG19 and ResNet18 models to decode seasonal nuances in the drawings, achieving notable accuracy in seasonal classification and revealing complex influences beyond human-centric methods. Techniques, such as occlusion, integrated gradients, PCA, t-SNE, and Louvain clustering, highlight critical areas and elements influencing seasonal recognition, providing deeper insights into the drawings. This approach not only advances the analysis of non-human art but also demonstrates the potential of AI to enrich our understanding of non-human cognitive and emotional expressions, with significant implications for fields like evolutionary anthropology and comparative psychology.

The selection of sleeping sites of animals provide valuable insights into their adaptations to a changing environment. We collected data on the sleeping sites used by a group of François' langurs (Trachypithecus francoisi) from September 2005 to August 2006 at the Nonggang National Nature Reserve in southwest China. Our results showed that the langurs utilized four sleeping sites on cliffs throughout the year. They foraged in the feeding patches close to their sleeping sites, showing a multiple central place foraging strategy. Notably, two sleeping sites were predominantly used during the dry season with least available young leaves and fruits, suggesting food seasonality may have a significant impact on the sleeping sites utilization. Moreover, the langurs used the sleeping sites in the peripheral area less than expected. They repeatedly and continuously slept at the Site 1, with a frequency of 79.8% of all recorded sleeping nights, and a maximum of eight consecutive nights. In conclusion, the sleeping site choices of François' langurs are mainly influenced by dietary factors, rather than range and resource defense, predator avoidance, thermoregulation, or parasite avoidance. This study highlights the significance of food resource and foraging efficiency to karst-dwelling François' langurs when selecting sleeping sites.