American Journal of Primatology最新文献

{"title":"Quantifying Facial Gestures Using Deep Learning in a New World Monkey","authors":"Filippo Carugati,&nbsp;Dayanna Curagi Gorio,&nbsp;Chiara De Gregorio,&nbsp;Daria Valente,&nbsp;Valeria Ferrario,&nbsp;Brice Lefaux,&nbsp;Olivier Friard,&nbsp;Marco Gamba","doi":"10.1002/ajp.70013","DOIUrl":"https://doi.org/10.1002/ajp.70013","url":null,"abstract":"<p>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.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 3","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajp.70013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143513459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ecological and Social Pressures Influence Diel Activity Patterns in Wild Tibetan Macaques","authors":"Pei-pei Yang,&nbsp;Wen-bo Li,&nbsp;Margaret C. Crofoot,&nbsp;Pritish Chakravarty,&nbsp;Xi Wang,&nbsp;Tong Zhang,&nbsp;Jin-hua Li","doi":"10.1002/ajp.70016","DOIUrl":"https://doi.org/10.1002/ajp.70016","url":null,"abstract":"<div>\u0000 \u0000 <p>The nighttime behavior of diurnal species is a “black box.” Although diurnal animals spend approximately half their lives in the dark, research has, for too long, relied on the simplifying assumption that what we can't observe isn't important. Advances in our ability to monitor nighttime behavior reveal that this is incorrect; essential biological and behavioral processes play out in the dark which are critical for understanding a species' ecology and evolution. We conducted our study from November 2021 to January 2022, using noninvasive 4G solar-powered night-vision cameras to quantitatively assess the impact of environmental and social factors on the diel activity patterns of wild Tibetan macaques at Mt. Huangshan, China. We find that Tibetan macaques maintain high levels of sleep throughout the night, as is typical for diurnal animals. However, non-sleep activity still accounted for 18.28% ± 0.45% of the total nighttime period, with activity occurring throughout the night. Notably, there was a peak in activity at midnight, including resting, movement, and social. Low temperatures significantly reduced daytime activity levels, while increasing nighttime activity, indicating that extreme temperatures have divergent impacts on activity levels during the day versus the night. Additionally, social activities were more frequent among females during the day, whereas males were more socially active at night. The distinct patterns of social activities during the day and night highlight the crucial role of social factors in nocturnal activities. The night-vision cameras have proven to be an effective research tool, allowing for a deeper understanding of primate behavior patterns and social structures. This provides new avenues for future research into the drivers of nighttime behavioral patterns across species.</p></div>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 3","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143497064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Color Biases and Preferences in Zoo-Housed Chimpanzees (Pan troglodytes), Gorillas (Gorilla gorilla gorilla), and Japanese Macaques (Macaca fuscata)","authors":"Jesse G. Leinwand,&nbsp;Priyanka Joshi,&nbsp;Gillian Vale","doi":"10.1002/ajp.70008","DOIUrl":"https://doi.org/10.1002/ajp.70008","url":null,"abstract":"<div>\u0000 \u0000 <p>Colors are an important signal for many primate species and have the potential to influence behavior and cognition. Primates may consciously or unconsciously prioritize their attention toward certain color stimuli to quickly identify consequential events, conspecifics, or resources. On the other hand, primates' color preferences can be modulated by memory, experiences, and affective responses. Few studies have explored the multifaceted nature of attention to colors in primate species that vary in their socioecologies and phenotypes, both of which may influence their responses to specific colors. The colors that rapidly capture primates' attention, and those they prefer, thus remain poorly understood. In a series of touchscreen experiments, we investigated responses to 9 perceptually distinct colored squares by 7 chimpanzees (<i>Pan troglodytes</i>), 11 gorillas (<i>Gorilla gorilla gorilla</i>), and 10 Japanese macaques (<i>Macaca fuscata</i>). We controlled for contextual cues known to influence color responses and assessed attentional biases using a dot probe task (Experiment 1) and preferences using a two-item forced-choice task (Experiments 2 and 3). In Experiment 1, we found that chimpanzees and gorillas showed the strongest attentional bias toward black, whereas the Japanese macaques showed the strongest bias toward red. These attentional biases suggest a potential relationship between species coloration and their attention to colors. In Experiments 2 and 3, all three species preferentially selected red, with Japanese macaques showing the strongest preference, supporting earlier findings that highlighted red as a particularly salient color to primates. Future research is needed to investigate the role of prior experience on primates' responses to colors.</p></div>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143447058","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Validating a Mixed Qualitative Behavioral Assessment for Adult Western Lowland Gorillas (Gorilla gorilla gorilla) I: Baseline Monitoring","authors":"Kylen N. Gartland,&nbsp;Emily Bovee,&nbsp;Grace Fuller","doi":"10.1002/ajp.70005","DOIUrl":"https://doi.org/10.1002/ajp.70005","url":null,"abstract":"<div>\u0000 \u0000 <p>Traditional qualitative behavioral assessments (QBAs) employ a unique whole-animal approach to measure animal welfare with a focus on affective elements. QBAs require comprehensive validation including reliability across multiple raters, subjects, and institutions, as well as consistency with other validated assessment measures. In 2016, the Detroit Zoological Society developed and began internally validating the Gorilla Behavioral Assessment Tool (GBAT), followed by internal applications of a revised GBAT in 2021. This study continues these validation efforts through the multi-institutional application of the GBAT in baseline conditions. Five zoological institutions participated in this study, creating a study population of 15 adult male western lowland gorillas (<i>Gorilla gorilla gorilla</i>) and more than 40 staff. Care staff collected fecal samples from each gorilla, and two staff from each institution completed the GBAT for each gorilla daily. Three of the five institutions collected focal behavioral data. We calculated inter-rater reliability using Gwet's AC₂, establishing near-perfect reliability across all tested items. We found no significant variation in reliability between institutions. We used the behavioral data and fecal glucocorticoid metabolites for construct validation. A combination of Spearman's correlations and generalized linear mixed models demonstrated statistically significant relationships between seven of the 12 tested GBAT items and other established measures. Integration of physical and behavioral indicators of welfare alongside affective indicators alters the GBAT from a traditional QBA into what we propose as a mixed or M-QBA. Our work demonstrates how an M-QBA allows for a more comprehensive assessment of animal welfare with implications for broader research applications.</p></div>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143447057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of Rhesus Macaque (Macaca mulatta) Facial Musculature: Implications for Macaque Social Behavior Ontogeny","authors":"Jordan T. Pater,&nbsp;Clare M. Kimock,&nbsp;Sarah E. Downing,&nbsp;Bridget M. Waller,&nbsp;Anne M. Burrows","doi":"10.1002/ajp.70003","DOIUrl":"https://doi.org/10.1002/ajp.70003","url":null,"abstract":"<div>\u0000 \u0000 <p>Rhesus macaques (<i>Macaca mulatta</i>) have long been used as a model for the evolution of some aspects of human social behavior and they are among the most completely understood species of the macaque genus. Rhesus macaques have a despotic dominance hierarchy with a well-documented facial display repertoire. However, we know little about the ontogenetic changes in gross facial musculature and how this might relate to corresponding facial display behavior. In an effort to illuminate our understanding, we dissected facial masks from 13 <i>M. mulatta</i> cadavers that died naturally, shortly after birth or were stillborn, and we compared these results to those from adult rhesus macaques. Results reveal that, unlike the adults in the present study, infant rhesus macaques have extrinsic external ear muscles and muscles associated with the lower lip that are very gracile and poorly developed. Musculature associated with the upper lip and nares are well developed, individually distinct, and robust, like those of the adults in our sample and adult <i>M. mulatta</i>. However, we were unable to locate the zygomaticus major muscle in any fetal/infant sample. These results may reflect simple variation in mimetic muscle ontogeny, differences related to facial allometry, or they could reflect a behaviorally meaningful adaptation to different life stages of macaque ontogeny.</p></div>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143431113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing the Determinants of Platyrrhine Quadrupedal Gait Kinematics in an Ecological and Phylogenetic Framework","authors":"Liza J. Shapiro,&nbsp;Noah T. Dunham,&nbsp;Allison McNamara,&nbsp;Jesse W. Young,&nbsp;Tobin L. Hieronymus","doi":"10.1002/ajp.70009","DOIUrl":"https://doi.org/10.1002/ajp.70009","url":null,"abstract":"<div>\u0000 \u0000 <p>Laboratory studies have broadened our understanding of primate arboreal locomotor biomechanics and adaptation but are necessarily limited in species availability and substrate complexity. In this field study, we filmed the locomotion of 11 species of platyrrhines (Ecuador and Costa Rica; <i>n</i> = 1234 strides) and remotely measured substrate diameter and orientation. We then explored ecological and phylogenetic influences on quadrupedal kinematics in multivariate space using redundancy analysis combined with variation partitioning. Among all species, phylogenetic relatedness more strongly influenced quadrupedal kinematics than variation in substrate. Callitrichines were maximally divergent from other taxa, driven by their preferred use of higher speed asymmetrical gaits. Pitheciids were also distinctive in their use of lower limb phases, including lateral sequence gaits. The biomechanical implications of interspecific differences in body mass and limb proportions account for a substantial portion of the phylogenetic-based variation. Body mass and kinematic variation were inversely related–whereas the larger taxa (atelids) were relatively restricted in kinematic space, and preferred more stable, symmetrical gaits, the smallest species (callitrichines) used faster, more asymmetrical and less cautious gaits along with symmetrical gaits. Intermembral index had a positive relationship with limb phase, consistent with higher limb phases in atelines compared to pitheciids. Substrate alone accounted for only 2% of kinematic variation among all taxa, with substrate orientation influencing kinematics more than diameter. Substrate effects, though weak, were generally consistent with predictions and with previous laboratory and field-based research. Excluding callitrichines and asymmetrical gaits, the influence of substrate alone remained low (2%), and the phylogenetic signal dropped from 31% to 8%. The substantial residual kinematic variation may be attributable to substrate or morphological variables not measured here, but could also reflect basic biomechanical patterns shared by all taxa that serve them well when moving arboreally, regardless of the challenges provided by any particular substrate.</p></div>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143431112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using 3D Photogrammetry to Quantify Usable Space in Zoo-Housed Primate Habitats","authors":"Charles P. Ritzler,&nbsp;Stephen V. Mather,&nbsp;India T. Johnson,&nbsp;Patricia M. Dennis,&nbsp;Kristen E. Lukas,&nbsp;Diana C. Koester","doi":"10.1002/ajp.70002","DOIUrl":"https://doi.org/10.1002/ajp.70002","url":null,"abstract":"<p>Studies of zoo animal space use typically use ground-level measurements as a proxy for “usable space,” but this method ignores above ground areas that are behaviorally relevant to arboreal species. Previous work has proposed different methods to calculate usable above ground space, but each has presented different limitations, ranging from the estimation of areas of dense complexity to the significant manual effort needed to physically measure spaces. To address these limitations, we tested a new, 3D photogrammetry-based method (“3DP method”) for calculating usable space in the habitats of two zoo-housed primate species (crowned lemur [<i>Eulemur coronatus</i>], and Bornean orangutan [<i>Pongo pygmaeus</i>]). 3D photogrammetry generates a 3D point cloud and subsequent mesh, using physically captured images, with geometric, measurable properties. Our method was compared to a previously published method, based in SketchUp, (“MSU method”) for both quantification of usable space (surface area, volume) and efficiency of model generation (active and passive work required). The 3DP method generated similar results for both usable surface area and volume for the crowned lemur habitat, while requiring 82% less active work from the user. Furthermore, the 3DP method was able to calculate usable space in a habitat (Bornean orangutan) that was 13,274% larger than the crowned lemur habitat, and substantially larger than any habitat where the MSU method has been applied in published work. Overall, the 3DP method decreased the ratio of active to passive work required for calculating usable space in zoo habitats with complex vertical space, and is flexible enough to be applied to habitats of varying sizes.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajp.70002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143423996","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Social Rank, Female Competition for Food, and Behavioral Time-Budgets in the Golden Snub-Nosed Monkey Rhinopithecus roxellana Multi-Level Society","authors":"Shujun He,&nbsp;Yi Yang,&nbsp;Zhenfeng Hu,&nbsp;Fan Wu,&nbsp;Chengliang Wang,&nbsp;Wenyong Tian,&nbsp;Rui-Feng Bai,&nbsp;Gao Qi,&nbsp;Yule Xie,&nbsp;Baoguo Li,&nbsp;Songtao Guo,&nbsp;Derek W. Dunn","doi":"10.1002/ajp.70007","DOIUrl":"https://doi.org/10.1002/ajp.70007","url":null,"abstract":"<div>\u0000 \u0000 <p>Competition within primate groups often translates to a social hierarchy, with high-rank individuals gaining privileged access to resources, especially food. Golden snub-nosed monkeys <i>Rhinopithecus roxellana</i> live in a multi-level society, with multiple one-male units (OMUs), each containing a single adult male and several females, forming a breeding-band. High-rank males have increased access to high-value foods and spend less time feeding and more time being groomed by females, potentially enhancing social cohesion within their OMUs. The adults of each OMU mainly feed and socialize together, with food competition predominantly acting at the OMU level. We thus predicted that adult females by association attain the rank and feeding privileges of their OMU leader males, and make similar time-budget trade-offs. By food-provisioning a wild breeding-band during winter and spring, when natural foods are abundant or limited, respectively, we found that females of high-rank OMUs ate more provisioned foods at higher rates, especially during winter when provisioned foods had increased value. In winter, females of low-rank OMUs fed for longer on natural foods and females of high-rank OMUs longer on provisioned foods. Females of high-rank OMUs spent longer being groomed by other OMU members, especially during winter. Our results are consistent with females attaining the feeding privileges of their OMU leader male, enhanced during winter due to increased value of provisioned foods, high thermal demands, and reduced natural food availability. Importantly, the feeding privileges attained by females of high rank OMUs were less pronounced than those previously found for leader males, possibly due to higher tolerance between females of different OMUs. We suggest that behavioral time-budget effects of food competition in female <i>R. roxellana</i> enhance cohesion in high-rank OMUs, contributing to OMU integrity and, hence, the social structure of this multi-level society.</p></div>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143397200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Continuous Provisioning Increases Breeding Success of Black-and-White Snub-Nosed Monkeys (Rhinopithecus bieti) in the Baima Snow Mountain Nature Reserve, Yunnan, China","authors":"Li Cao,&nbsp;Feng Liu,&nbsp;Long-Jie Guo,&nbsp;Qing-Lei Sun,&nbsp;Sang Ge,&nbsp;Bo-Yan Li,&nbsp;Ying Zhou,&nbsp;Xue-Lan Fang,&nbsp;Ying Geng,&nbsp;Wei-Bin Song,&nbsp;Cyril C. Grueter,&nbsp;Yan-Peng Li,&nbsp;Liang-Wei Cui,&nbsp;Wen Xiao","doi":"10.1002/ajp.70006","DOIUrl":"https://doi.org/10.1002/ajp.70006","url":null,"abstract":"<div>\u0000 \u0000 <p>The high energy demands of primates during pregnancy and lactation often limit their breeding success due to the availability of food resources. Until now, few studies have focused on the effects of continuous provisioning on primate reproduction. To assess the impact of continuous provisioning on breeding success, we collected data on female reproductive status (primiparous or multiparous), maternal age of births, births, deaths, and sex of infants in a free-ranging semi-provisioned band (FSB) of <i>Rhinopithecus bieti</i> in China from 2010 to 2023. Our results indicate that provisioning significantly increases infant survival. After 8 years of provisioning, 11 females began a pattern of giving birth to infants in two continuous years, skipping reproduction in the third year, and resuming in the fourth year. Continuous provisioning led to a year-by-year reduction in the interbirth interval (IBI) and a gradual decrease in the primiparous age. The percentage of consecutively breeding females (CBFs) and their offspring increased annually and with the mother's ages. Conversely, the percentage of offspring from non-consecutively breeding females (NBFs) decreased over time and with maternal age. Each CBF annually produced 9.4% more infants compared to NBFs. Compared to NBFs, CBFs had a higher maternal age at births, a higher fertility rate, a higher infant survival rate, and a 11.7% shorter IBI. Furthermore, compared to the non-provisioned wild band (NPB), females in the FSB gave birth 128 days earlier, had an 18.9% annual increase in the number of offspring per female, and showed 1.2 times higher infant survival beyond 12 months. Our study demonstrates that provisioning significantly enhances reproductive success and population size. However, before promoting provisioning as a conservation tool to stabilize and recover endangered wildlife populations, it is essential to thoroughly evaluate its potential risks, such as nutritional imbalances, increased stress, and the transmission of diseases.</p></div>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143397201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Running the Risk: Road-Crossing Behavior in Wild Chimpanzees (Pan troglodytes) in an Anthropogenic Habitat in Uganda","authors":"Marie Tellier,&nbsp;François Druelle,&nbsp;Marie Cibot,&nbsp;Johnmary Baruzaliire,&nbsp;Tom Sabiiti,&nbsp;Matthew R. McLennan","doi":"10.1002/ajp.70000","DOIUrl":"https://doi.org/10.1002/ajp.70000","url":null,"abstract":"<p>Recent research highlights the behavioral flexibility of wild chimpanzees in response to human-induced changes in their environment, including agricultural and infrastructural development. The expansion of road networks threatens chimpanzee populations across Africa. Studying their road-crossing behavior, especially outside protected areas where road impacts are greatest, helps identify factors influencing their choices and flexibility. This study seeks to gain a deeper understanding of how chimpanzees navigate busy roads and assess the danger posed by roads. Such insights are needed to develop effective conservation strategies in regions facing escalating human impact, including recommendations for the design and management of traffic on existing and future roads. Using a dataset of 129 video-recorded road crossings spanning 38 months, we analyzed the behavioral adjustments of chimpanzees in Bulindi, Uganda, when crossing a recently paved, busy main road within their home range. Using generalized linear mixed models, we investigated chimpanzee risk perception, protective and cooperative behaviors, vigilance, and progression order during road crossings. We identified variations in their behavior according to age-sex of individuals, group composition, and level of risk. We found that Bulindi chimpanzees exhibit behavioral strategies to reduce risks of collision or close encounters with humans on the road, as previously described. However, they were less vigilant than expected. We suggest that the chimpanzees have developed tolerance of the risks presented by the road, owing to their long history of crossing it before it was tarmacked and widened, and their familiarity with local people and motor traffic. Our results provide further evidence of the flexibility of wild chimpanzees. However, road crossings remain highly risky for large mammals like great apes, necessitating measures to mitigate the impact of road development on this and other endangered species (e.g. speed bumps, police enforcement, public awareness raising).</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"87 2","pages":""},"PeriodicalIF":2.0,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajp.70000","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143370072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}