American Journal of Primatology最新文献

Understanding primate dietary plasticity provides insights into trait evolution and resilience to environmental change. Here, we investigate the feeding ecology of mandrills (Mandrillus sphinx), a species that forms groups of close to 1000 individuals, which presumably impacts feeding ecology by creating exceptionally high feeding competition. Mandrills are also threatened by habitat loss and climate change, and a full understanding of their dietary plasticity is essential to ongoing conservation efforts. Evidence suggests that mandrills are generalist feeders and consume a wide variety of resources to compensate for shortfalls in fruit availability. However, a lack of long-term data on fruit production within the mandrill geographic range means that it is unknown whether the flexible feeding strategies observed previously are stable over multiple years. We combined two rare data sets comprising 8 years of fecal collection and fruit availability to assess the dietary flexibility of mandrills in Lopé National Park, Gabon. We found fruit to be the most frequently consumed resource and fruit consumption covaried positively with fruit availability, peaking during periods of fruit abundance. Mandrill dietary diversity increased during periods of fruit scarcity, through greater consumption of animal prey, leaves, seeds, and other plant fibers. These results demonstrate that mandrills are primarily frugivorous, but that they are also highly flexible feeders, able to respond to temporal variation in fruit production over several annual cycles. In addition, we found that mandrills varied in the extent to which they preferred different fruit taxa. Lipid-rich oil palm (Elaeis guineensis) fruits were by far the most frequently consumed resource and may constitute a staple resource for mandrills in the study site. Our multiyear study provides robust evidence for generalist feeding behavior by mandrills, which may be driven by extreme group sizes or past environmental fluctuations and provide resilience to future environmental change.

The primary goal of captive primate management is to ensure optimal health and welfare of the animals in our care. Given that the gut microbiome interacts closely with host metabolism, immunity, and even cognition, it represents a potentially powerful tool for identifying subtle changes in health status across a range of body systems simultaneously. However, thus far, it has not been widely tested or implemented as a monitoring tool. In this study, we used longitudinal microbiome sampling of newly arrived chimpanzees at Chimp Haven to explore the feasibility of using the gut microbiome as a health and welfare biomarker in a sanctuary environment. We also tested the hypothesis that a transition to a new living environment, and integration into new social groupings, would result in temporal changes in chimpanzee gut microbiome composition. The collection of longitudinal microbiome data at Chimp Haven was feasible, and it revealed temporal shifts that were unique to each individual and, in some cases, correlated to other known impacts on health and behavior. We found limited evidence for microbial change over time after arrival at Chimp Haven that was consistent across individuals. In contrast, social group and enclosure, and to a lesser extent, age and sex, were associated with differences in gut microbiome composition. Microbiome composition was also associated with overall health status categories. However, many of the effects we detected were most apparent when using longitudinal data, as opposed to single time point samples. Additionally, we found important effects of technical factors, specifically outdoor temperature and time to collection, on our data. Overall, we demonstrate that the gut microbiome has the potential to be effectively deployed as a tool for health and environmental monitoring in a population of sanctuary chimpanzees, but the design must be carefully considered. We encourage other institutions to apply these approaches and integrate health and physiology data to build on the utility of gut microbiome analysis for ensuring the welfare of captive primates in a range of contexts.

Phylogenetic trees are analytic tools used in primate studies to elucidate evolutionary relationships. Because of its relative ease to sequence and rapid evolution compared to nuclear genomes, mitochondrial DNA is frequently used for phylogeny building. This project evaluated the effectiveness of using individual or grouped mitochondrial genes (mtGenes) as a proxy for the mitochondrial genome (mtGenome) in phylogeny building within two nested primate datasets, Cebidae and Platyrrhini, with differing divergence dates. mtGene utility rankings were determined based on congruence values to the mtGenome tree. mtGenes trees were also assessed on tree resolution and ability to sort nested clades. We found that most individual mtGenes, including ribosomal genes (12S and 16S), COX genes, most ND genes, and d-Loop are not appropriate for use as proxies for the mtGenome when tree building in either the Cebidae or Platyrrhini set. On average, grouped mtGenes outperformed individual mtGenes in both sets, and mtGene and grouped mtGene rankings varied between sets. Pairing CYB and COX3 together or pairing ND2 and CYB worked well in both the Cebidae set and the Platyrrhini set. We also found that nucleotide diversity is not a predictor of mtGene performance. Instead, it may be that unique mtGene or mtGene system evolutionary history impacts mtGene performance.

Self-awareness has most commonly been studied in nonhuman animals by implementing mirror self-recognition (MSR) tasks. The validity of such tasks as a stand-alone method has, however, been debated due to their high interindividual variation (including in species deemed self-aware like chimpanzees), their reliance on only one sensory modality, their discrete outcomes (i.e., pass/fail) and, in general, questionned regarding their ability to assess self-awareness. Therefore, a greater variety of methods that assess different aspects of the self, while simultaneously contributing to a more gradualist view of self-awareness, would be desirable. One such method is the body-as-obstacle task (BAO), testing for another dimension of body self-awareness. The ability to understand one's own body as an obstacle to the completion of a desired action emerges in young children at approximately the same age as mirror self-recognition, suggesting a shared mental representation. Whereas recently some studies showed body self-awareness in nonhuman animals, so far, outside of children no studies have compared how the performances of individuals relate between these two tasks. Therefore, here we study both a MSR and a BAO task in chimpanzees and gorillas. We chose these species particularly because evidence for MSR in chimpanzees is well established, whereas results for gorillas have been mixed, which has been attributed to the study design of MSR tasks, and for which a BAO task might thus provide more conclusive evidence. We find that although only some chimpanzees showed evidence for mirror self-recognition, thus replicating previous findings on interspecies differences in MSR, chimpanzees and gorillas performed equally well in the BAO task. Yet, we further found no correlation between the individuals' performances in both tasks. We discuss the implications of these findings for the interpretation of the results of BAO tasks as a possible alternative paradigm for the study of self-awareness in non-human animals.

Chimpanzees exhibit considerable inter- and intra-community variation in cognitively complex tool use behaviors, often attributed to social, genetic, and environmental factors. Termite fishing is a well-documented chimpanzee tool-using behavior that has been the subject of comparative research exploring behavioral variation between chimpanzee communities. However, termite fishing in the Nigeria-Cameroon chimpanzee (Pan troglodytes ellioti) has been historically underrepresented due to a lack of habituated populations. In this study, we used remote-activated camera traps at several termite mounds for 3 years to study termite fishing near Ganga Research Station in central Cameroon. We aimed to (1) identify elemental variation in chimpanzee termite fishing techniques at Ganga, an understudied community of P. t. ellioti, and (2) compare termite fishing behaviors in the Ganga community among more well-studied chimpanzee communities. We found 46 different combinations of behavioral elements representing termite fishing techniques used by Ganga chimpanzees (n = 9) across five termite mounds. The average technique was between three and four elements long (x̄ = 3.673), and many chimpanzees had unique personal repertoires. Chimpanzees at Ganga shared the most behavioral similarities with two communities of savanna chimpanzees, Dindefelo and Kayan, and the nearby rainforest community of La Belgique in southern Cameroon. This behavioral similarity between Ganga chimpanzees, who inhabit a complex forest/savanna matrix, and two distant savanna-dwelling communities suggests similar environmental contexts contribute to termite fishing similarity. These results add to comparative studies of termite fishing behavior and demonstrate the utility of quantitative ethnographic methodology in exploring chimpanzee behavioral variation.

All great apes build nests. Nests in trees or on the ground provide apes with a safe and comfortable place to sleep and rest at night and during the day. Nest building is a necessary skill and form of tool use that individuals learn and practice early in life, but little is known about its development and about the factors affecting the expression of nest building in infancy. We studied the development of daytime nest building of 72 wild immature chimpanzees (Pan troglodytes schweinfurthii) at Ngogo, Kibale National Park, Uganda. We evaluated the effects of age, sex, and maternal parity on the likelihood of infant nest building (presence or absence), as well as on the rates (frequency/hour) and durations (time from start to finish of each nest) with which infants built nests. Compared to the youngest infants (≤ 1 year), older infants were more likely to build nests, and built them at higher rates, consistent with hypotheses that nest building requires learning in early infancy and a threshold of physical development to manipulate tree branches. Female infants were more likely to build nests and built them more often than male infants, corroborating other developmental markers suggesting females attain functional independence at younger ages than males in some chimpanzee populations. Among infants who were seen to build nests at least once, rates and durations were similar, regardless of age, sex, or maternal parity, which indicated that there was little interindividual variation in nest building development once infants started practicing. The observed patterns of prior and subsequent behaviors to nest building suggested that infants > 4 years old built nests more functionally, for resting, than younger infants. This study underscores the value of nest building as a developmental measure in wild great apes. Studying factors that affect the expression of nest building in infancy allows for a better understanding of the ontogeny and evolution of learning and tool use in hominids.

Facial gestures are a crucial component of primate multimodal communication. However, current methodologies for extracting facial data from video recordings are labor-intensive and prone to human subjectivity. Although automatic tools for this task are still in their infancy, deep learning techniques are revolutionizing animal behavior research. This study explores the distinctiveness of facial gestures in cotton-top tamarins, quantified using markerless pose estimation algorithms. From footage of captive individuals, we extracted and manually labeled frames to develop a model that can recognize a custom set of landmarks positioned on the face of the target species. The trained model predicted landmark positions and subsequently transformed them into distance matrices representing landmarks' spatial distributions within each frame. We employed three competitive machine learning classifiers to assess the ability to automatically discriminate facial configurations that cooccur with vocal emissions and are associated with different behavioral contexts. Initial analysis showed correct classification rates exceeding 80%, suggesting that voiced facial configurations are highly distinctive from unvoiced ones. Our findings also demonstrated varying context specificity of facial gestures, with the highest classification accuracy observed during yawning, social activity, and resting. This study highlights the potential of markerless pose estimation for advancing the study of primate multimodal communication, even in challenging species such as cotton-top tamarins. The ability to automatically distinguish facial gestures in different behavioral contexts represents a critical step in developing automated tools for extracting behavioral cues from raw video data.