Primates最新文献

In recent years, deep learning has achieved high performance in bioacoustic classification tasks by leveraging automatically processed acoustic features for large datasets. However, few performance evaluations of automatically processed acoustic features have been conducted on small-scale data because deep learning requires large datasets. To test whether mel spectrograms (automatically processed acoustic features) are effective for classifying relatively small acoustic data, we evaluated the performance of two classification machines (random forest and support vector machine) using mel-spectrograms of 651 coo calls of six wild female Japanese macaques on two tasks: 1) individual identification and 2) age-class classification between younger (< 10 yrs) and the older animals (> 20 yrs). For the individual identification task, the mean balanced accuracy was 0.81 for random forest and 0.82 for support vector machine. For the age-class classification task, the mean balanced accuracy was 0.91 for random forest and 0.93 for support vector machine. Considering that of all the calls were recorded in the wild, methods using automatically processed acoustic features, such as mel spectrogram, are effective in classifying small acoustic data for the individual identification task. The high performance in the age-class classification task might be attributable to the potential of mel spectrograms to capture the characteristics of older individuals (e.g. harshness).

Anthropogenic disturbances pose significant challenges for wildlife conservation, especially for threatened primates such as the mantled howler monkey (Alouatta palliata). We investigated whether and how human presence and noise influence the immediate movement responses of mantled howler monkeys inhabiting an agroforestry system in Los Tuxtlas, Mexico. Between January 2020 and April 2021, we recorded monkey and human locations, human activities, and A-weighted equivalent continuous sound pressure levels (LAeq) at 15-min intervals during 823 h of observation. Using generalized linear mixed models, we found that both the occurrence and magnitude of avoidance movement increased significantly with increasing worker numbers and sound pressure levels. Although movement increased throughout the day, movement direction relative to human location remained constant, suggesting that circadian patterns influence when, but not how animals respond to anthropogenic factors. Therefore, howler monkeys avoid human presence while maintaining their characteristic energy-conservative ranging patterns, suggesting a complex balance between risk avoidance and metabolic demands. Our findings have important implications for wildlife management in agroforestry systems, as even relatively low levels of human presence (approximately one person per hectare) and noise (ranging from 40 to 85 dB) can trigger behavioral responses.

Traumatic injuries are a major cause of morbidity and mortality in free-ranging non-human primates (NHPs), often associated with anthropogenic pressures such as habitat loss, urbanization, and interactions with domestic animals. This study characterized some epidemiological, spatial, and pathological patterns of mechanical traumatic injuries in free-ranging non-human primates from anthropogenically altered areas of the Federal District. Of 696 necropsies performed, 215 cases (30.9%) involved mechanical trauma. Black-tufted marmosets (Callithrix penicillata) were the most affected species (90.2%), followed by capuchins (Sapajus libidinosus, 6.5%) and howler monkeys (Alouatta caraya, 3.3%). Adults were more frequently affected than juveniles, with no sex-related differences. Blunt trauma accounted for the majority of cases (82.3%), most commonly as polytrauma, with cranial involvement in 65.2% of animals. Carnivore predation was the leading cause of blunt-penetrating trauma (89.4%), while gunshot injuries were rare. Bone fractures were identified in 65.1% of cases, most often involving the skull and long bones, and internal injuries were frequent in the thoracic and abdominal cavities. These findings demonstrate that mechanical trauma represents a critical threat to NHPs in urban and peri-urban areas, where exposure to human infrastructure and domestic animals is heightened. The results underscore the need for mitigation strategies to reduce mortality and support the conservation of free-ranging primate populations in human-dominated landscapes.

The distribution of African great apes has remained unconfirmed regarding their southern limit, particularly on the western side of the continent. IUCN maps include the Mayombe forest of Angola as part of the estimated distribution of western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes). However, until now, there were no records confirming the continued presence of both species. The Mayombe forest is a key biodiversity hotspot and a potentially important stronghold for the conservation of great ape populations in Africa. Here, we report the first systematic evidence of both species in the Mayombe National Park, Cabinda, Angola. In 2023, a grid of camera traps was systematically deployed, producing the first visual records of gorillas and chimpanzees. Building on these findings, in 2024, a pilot survey including ad libitum field observations was carried out along exploratory trails to maximise data collection. The combination of these records identified a hotspot of great ape activity where six transects were established, and systematic direct and indirect evidence was documented. Chimpanzees were recorded more times across a broader range of evidence categories, while gorillas appeared less and seemed more spatially restricted. Notably, both species were detected at overlapping sites but never simultaneously, indicating sympatric coexistence with spatio-temporal partitioning. These findings confirm the southernmost predicted distribution of both species for this part of Africa, filling critical gaps in the understanding of great ape evolution and biogeography, and providing a baseline for the first demographic and ecological census of great apes in Angola.

Primate research has long depended on the deep ecological and behavioral knowledge of local communities living near or within primate habitats, yet this knowledge has rarely been given the same visibility as academic science. In this collaboratively formulated article we argue that including local and traditional knowledge alongside scientific studies enriches primatology epistemically, ethically, and practically. We introduce the Perspectives Collective Journal, a collaborative multimedia journal-the first of its kind-created to support the direct sharing of local and traditional insights about primates, as well as other species, in their natural habitats. By providing an accessible and flexible platform for storytelling, reflection, and documentation, including written articles, participatory films, interviews, and group discussions, Perspectives invites a plurality of voices and formats into primatological knowledge production. Here we highlight several ways in which local knowledge can contribute to primatology and its complementary relationship to mainstream science by drawing upon materials published in Perspectives and framing it in relation to the mainstream scientific literature on primate behavior. Overall, this paper and the Perspectives project more generally demonstrate the value of allowing diverse knowledge systems to meet on equal footing.

Understanding whether a species' distribution results from recent and/or anthropogenic events or ancient vicariant factors is critical for conservation planning. The Endangered Sanje mangabey (Cercocebus sanjei), endemic to Tanzania's Udzungwa Mountains, is currently divided into two populations located approximately 100 km apart. These represent distinct evolutionary lineages that diverged around 0.77 million years ago (MYA). We aimed to investigate i) the phylogeographic history and recent changes in size and range of the two Sanje mangabey populations, and ii) whether lack of suitable habitat between populations and consequent difficulty to disperse may have influenced the 0.77 MYA divergence time. We used 64 mitochondrial control region sequences obtained from non-invasive DNA. The probability of suitable habitat across Tanzania and the Udzungwa Mountains was modelled at three time points: Mid-Holocene (6,000 YA), Last Glacial Maximum (22,000 YA), and the Last Interglacial period (120,000-140,000 YA). We found six haplotypes, clustered into two haplogroups. Significant differentiation was estimated between populations, which show no evidence for recent range expansion or contraction. The ecological niche modelling revealed fluctuating extents of suitable habitat across southern Tanzania. Large genetic differentiation between populations may have been influenced by a general trend in aridification in East Africa across the last 40,000 years, resulting in a shift of montane forests to gradually higher elevations. Intermediate populations may have become extinct as suitable habitat retracted, leaving relict populations with relatively stable demographic histories ancestral to the present-day populations. This study supports their preliminary designation as separate evolutionary significant units, a conclusion with conservation management implications.

In reverse-reward contingency tasks, the subject chooses between two potential rewards differing in value. To receive the higher-value reward, the subject must reach toward the lower-value reward; any reach toward the higher-value reward results in receiving the lower-value reward. In studies on animals, the rewards are usually food items differing in quantity or quality. Sixteen years after participating in reverse-reward tests, captive adult capuchin monkeys (Sapajus apella) were retested under the same conditions. We asked whether there would be evidence of memory of previous learning, or aging-related effects on performance. As previously, monkeys first experienced a "quantity" condition and then switched to a "quality" condition, or vice-versa. The two best-performing monkeys 16 years earlier showed significantly poorer performance in the present study, indicating possible age-related decline in reverse-reward competence. By contrast, a monkey not yet fully adult 16 years earlier but now 23 years old learned the R-R contingency in the quality condition, which suggests that inhibitory control ability in this species can be expressed at least into their 20s. Other individuals' performances were similar to those of 16 years ago, some associated with side preferences. Assessments of age-related changes in inhibitory control need to consider task characteristics and behavioral biases. Combining longitudinal and cross-sectional approaches may be optimal for clarifying the development and later decline of cognitive abilities across the lifespan.

Leucism, a pigmentation disorder resulting in partial loss of coloration, is rare in neotropical primates. This manuscript presents the first report of a leucistic robust capuchin monkey (Sapajus libidinosus), observed at Ubajara National Park, Brazil. Our findings contribute to the sparse literature on leucism in New World monkeys, emphasizing the importance of long-term studies for monitoring such rare anomalies.