Primates最新文献

Habitat fragmentation poses a significant threat to primate populations, necessitating behavioral adaptations in activity patterns and feeding strategies. This study investigated the impact of habitat fragmentation on the endangered San Martin titi monkey (Plecturocebus oenanthe) in the Moyobamba region of Peru. Activity budgets and feeding strategies were compared between groups inhabiting large (400 ha) and small (5 ha) forest fragments. Results revealed that resting was the predominant activity in both habitats, followed by feeding. Notably, individuals in large fragments allocated significantly more time to feeding (30.1%) than those in small fragments (23.0%) did. Social interactions were more prevalent in the small fragments (15.1%) than in the large fragments (9.1%). Fruit was the primary dietary component in both sites, accounting for 59.9% in the large fragment and 44.9% in the small fragment. However, individuals in small fragments exhibited a higher consumption of leaves (13.7%) and prey (14.6%) than those in large fragments (7.1% and 8.5%, respectively). The feeding time for specific food resources varied according to the fragment size and seasonal availability. These findings demonstrate the ecological plasticity of P. oenanthe in adapting to fragmented habitats by modifying their activity budgets and feeding strategies. However, continued habitat degradation may compromise these adaptive mechanisms, highlighting the need for conservation efforts focused on habitat restoration and connectivity to ensure long-term persistence of this endangered primate species.

Comprehensive species distribution data is crucial for assessing threat levels, conservation status and formulating effective conservation strategies. Globally, over half of the primate species remain unstudied, particularly those inhabiting challenging and remote environments. Endemic to the North-Western Himalayas, the Kashmir gray langur (Semnopithecus ajax) is a primarily arboreal forest-dwelling folivorous primate. Its shy behavior and the steepness of the inhabiting terrain in the high-altitude ecosystem makes it highly elusive and challenging to study. We employed an ensemble modeling approach to (i) predict the distribution of species in the Kashmir Himalayas and, (ii) gain insight into the importance of various environmental factors that influence the occurrence of the Kashmir gray langur. Our model, based on 35 environmental variables and 144 occurrence points, depicted forested mountainous areas with moderate slopes at mid elevations and with low human disturbance as suitable habitats for the Kashmir gray langur. The model showed strong discrimination (mean AUC = 0.926; mean TSS = 0.78), with predicted areas corresponding to the observed species locations, thereby supporting both its validity and ecological relevance. Variable response curves indicated a strong association of the species with areas characterized by pronounced precipitation seasonality, moderately sloping terrain, and optimal diurnal temperature ranges. These conditions typify temperate deciduous and coniferous forests, and these forests are increasingly threatened by ongoing climate change and require climate-adaptive management strategies for their conservation. We recommend integrating the findings of this preliminary yet important study into devising effective conservation and management strategies, as well as enhancing regular population monitoring to generate a comprehensive database on the species for long-term conservation implications.

The genes of the major histocompatibility complex (MHC) are vital to vertebrate immunity and may influence mate choice in several species. The extent to which the MHC influences female mate choice in primates remains poorly understood, and studies of MHC-based mate choice in platyrrhines are especially rare. White-faced capuchin monkeys (Cebus imitator) reside in multimale-multifemale groups where alpha males sire most of the offspring, but females related to the alpha male reproduce with subordinate males. In this study, we investigated the potential role of MHC genotypes, in the context of social dominance and relatedness, in determining which mating pairs produced offspring in wild white-faced capuchins in the Sector Santa Rosa, Área de Conservación Guanacaste, Costa Rica. We found that neither the social status nor the siring success of males was associated with their MHC metrics. Using mixed conditional logit models and generalized linear models, we found that MHC metrics did not predict the probability of siring offspring or being an alpha male. Alpha males that were distantly related to reproducing females were significantly more likely to sire offspring regardless of MHC genotype. However, we did find some evidence that subordinate males heterozygous at MHC loci sired significantly more offspring than homozygous subordinate males. Further, one-sided binomial simulations revealed that offspring were more frequently heterozygous at MHC loci than expected given the gene pool. We conclude that in this population, females related to the alpha may preferentially mate with MHC-diverse subordinate males, leading to increased probabilities of MHC-diverse offspring.

The influence of gut microbiota on vertebrate health, development, growth, and physiology is increasingly evident. Considerable research has concentrated on Primates, not only because many non-human species have long acted as laboratory models to better understand human health, but also to improve our knowledge of the ecology of this mammalian Order with the highest proportion of endangered wild taxa. While bacteria have been the primary focus, other gut components (archaea, protozoa, fungi, viruses, and helminths) also play critical roles in host survival. Only recently have there been microbiota studies examining interactions among gut components and their influence in both captive and wild non-human primates. Here we systematically reviewed all research articles on non-human primates where gut bacteria were studied together with at least one other gut taxon. Studies on humans were included in each comparison where these suggested (i) potential health outcomes of patterns observed in non-human primates, or (ii) how approaches used in human microbiota studies could more effectively advance non-human primate research and conservation. Specifically, we focused on associations (such as covariations in diversity indices or abundance between taxa), direct interactions (one taxon affecting another with experimental evidence), and external influences (e.g., disease, diet, environment) impacting multiple taxa. We found that for non-human primates, direct interactions among bacteria and other gut taxa have rarely been confirmed except under experimental captive conditions, especially for wild species. However, the associated changes in richness, abundance, and/or metabolic pathways indicate interdependence among gut taxa, confirming their links with host nutrition and immunity and, consequently, their potential impact on host health and species conservation.

Only a few records of pigmentation anomalies, particularly hypopigmentation conditions such as albinism, have been reported among Neotropical non-human primates. In Brazil, there are only 14 documented cases of pigmentation anomalies, with just two instances of albinism recorded within the Cebidae family. To our knowledge, no pigmentation polymorphisms have been documented in the Pitheciidae family to date. In this study, we report the first documented case of albinism in Callicebus nigrifrons (the black-fronted titi monkey) within the largest remnant of the Atlantic Forest in the State of Minas Gerais, Brazil. This observation was made using a drone equipped with 4K cameras and thermal infrared sensors. This primate exhibited characteristics such as the absence of pigmentation in its fur, as well as in its palms of its hands and feet, and dark red eyes. It was observed in a group composed of two other individuals displaying typical coloration. The group's behavior was normal, showing no signs of exclusion toward the albino individual. Potential causes of albinism in C. nigrifrons may include genetic or environmental factors, or combined pressures, though these remain speculative. This is the first confirmed case of albinism in the Pitheciidae family and the first record of such a phenomenon using drone technology in the wild. Our findings underscore the potential of drones for detecting low-frequency phenotypic traits in elusive species and reinforce the role of protected areas such as the Rio Doce State Park in safeguarding threatened and genetically distinct individuals.

Predation risk fundamentally shapes primate social structure by influencing cooperation, competition, and spatial organization within groups. Although domestic dogs (Canis lupus familiaris) represent one of the world's most impactful invasive species affecting wildlife, their influence on primate social structure remains largely understudied. We examined how dog presence and barks influence interindividual proximity among group members in mantled howler monkeys (Alouatta palliata). We studied two habituated groups (10 and 8 adults, respectively) in Veracruz, Mexico, combining 242 h of observational data with experimental playbacks of dog barks at different intensities (40 and 80 dB). We calculated proximity indices from instantaneous sampling of interindividual proximity. Howler monkeys were closer immediately following exposure to dogs, partially supporting our hypothesis that interindividual proximity would change in response to dogs. Contrary to predictions, individuals were farther from each other as bark intensity increased and as proximity to dog stimuli decreased. During longer timeframes, individuals were closer when exposed to low-intensity barks compared to periods without dog stimuli. These findings demonstrate that dogs influence howler monkey spatial organization through context-dependent effects that vary with stimulus characteristics and temporal scale. Despite the short-term nature of this study, the consistency between observational and experimental results suggests these patterns are reliable. Therefore, these results contribute to our understanding of how invasive predators affect primate social structure and highlight the importance of managing free-ranging dogs in areas where they overlap with wildlife populations.

Habitat disturbances, including stochastic events such as disease outbreaks, can significantly affect primate populations by reducing population density and demographic structure. The black-and-gold howler monkey (Alouatta caraya, IUCN: Near Threatened) is the southernmost species of the genus Alouatta and inhabits a variety of environments throughout its distributional range. In Argentina, A. caraya is classified as vulnerable, but following a yellow fever outbreak (YFO) between 2007 and 2009, the subpopulations in the province of Misiones were reclassified as Endangered. This study provides, for the first time, density estimates for two sites in southern Misiones where monkey mortality was reported during the 2007-2009 YFO, as well as for four sites in northern Corrientes, where no YFO-related mortality has been documented. All sites are located within the Southern Cone Mesopotamian Savanna (SCMS) ecoregion. We identified 34 groups of A. caraya-17 in Misiones and 17 in Corrientes. In Misiones, we recorded one of the lowest A. caraya densities reported in Argentina, with only 0.33 individuals per hectare (mean = 0.31, SD ± 0.12). In contrast, densities in Corrientes reached up to 1.34 individuals per hectare (mean = 1.11, SD ± 0.18), consistent with previously reported values for the species. These preliminary results suggest that density variation within the same ecoregion may be linked to population declines in areas affected by yellow fever (YF). Nonetheless, the presence of three groups with only three individuals each in Misiones may indicate early signs of recolonization or population expansion in the aftermath of the outbreak.

Food selection in primates is guided by a sensory evaluation of the physical and chemical properties of the foods. These properties vary with plant species, plant part, and plant maturity. Spider monkeys generally consume ripe fruits, but their diet also includes unripe fruits and young and mature leaves from a wide variety of plant species. We evaluated food selection in ten adult black-handed spider monkeys (Ateles geoffroyi) living in a controlled environment in Catemaco (Veracruz, Mexico). We used six plant species which are part of their natural diet and compared selection between ripe and unripe fruits and young and mature leaves, respectively, for the same plant species. We also analyzed the sucrose content, pH, size, and color of fruits and the color and size of leaves of each plant species. For fruit selection, our model showed that 75% of choices depended on an association between the plant species and the stage of maturity. In contrast, our model predicted 52% of the leaf selection, and monkeys considered both the stage of maturity and the plant species. Our results suggest that Ateles geoffroyi exhibit a more specific food selection for fruits than leaves, resulting in different food choices based on the physical and chemical properties of these food items.

Studying nonhuman primates' responses to the death of conspecifics has gained growing interest in comparative thanatology providing wider evolutionary context for our understanding of human responses to death and mourning. Primates exhibit diverse reactions to infant deaths, with infant corpse carrying (ICC) being most frequently reported. We tested existing hypotheses about the functional significance of ICC and describe other behaviors directed towards corpses using 21.7 years of observations on mountain gorillas involving 141 infant deaths. ICC is common in mountain gorilla mothers (60.5% of deaths) with an average duration of 4.9 days. Consistent with primate literature, ICC by mothers occurred less often and for shorter durations after traumatic deaths and with increasing infant age at death. Mothers' parity, season, and whether a mother had previously carried an infant corpse did not affect ICC. Non-mothers across age classes and sexes participated in ICC and directed affiliative and investigative behaviors toward corpses, reflecting the important role that non-mother caregivers can play in infant gorillas' development and survival. Nulliparous and primiparous females were proportionally more often non-mother carriers than multiparous females which supports the 'learning to mother' hypothesis. Our findings suggest that delays in overcoming strong attachment bonds and difficulties in detecting death lead to a greater likelihood and longer duration of carrying after death. Understanding these behaviors in mountain gorillas enriches our knowledge of their social and care systems and contributes to broader discussions on primate cognition and responses to death.