American Journal of Primatology最新文献

{"title":"Detecting a Stalker: The Effect of Body Posture, Gaze Direction, and Camouflage Pattern on Predator Detection.","authors":"Pedro Z de Moraes, Pedro Diniz, Daniel M A Pessoa","doi":"10.1002/ajp.23699","DOIUrl":"10.1002/ajp.23699","url":null,"abstract":"<p><p>The success of a predatory attack is related to how much a predator manages to approach a prey without being detected. Some carnivore mammals use environmental objects (e.g., leaves and branches) as visual obstacles during stalking behavior, allowing them to expose only parts of their bodies while approaching and visual monitoring their prey. Here, we investigate the influence of carnivores' body postures, gaze direction, and camouflage pattern on their detection by prey. To do so, we photographed taxidermized carnivore models (cougar, ocelot, and lesser grison) in their preserved natural habitats and presented these images to human dichromats (i.e., colourblinds) and trichromats (i.e., normal color vision). Our findings highlight the importance of body outline and gaze as search images during predator detection tasks. We also demonstrate that coat and facial color patterns can camouflage predator's body outline and gaze. This is the first behavioral evidence that the facial coloration of natural predators might mask their gaze to potential prey. Furthermore, we observed that carnivore coat color patterns may serve as an additional cue for trichromats, particularly in hidden carnivore detection tasks that proved to be more challenging for dichromats. Our results show possible strategies that evolved between predator and preys, in which prey make use of body outlines, gaze direction, and coat color to improve predator detection, while predators potentially evolved stalking behavior and body/gaze camouflage as counter strategies to cope with the improvements in prey's perception and conceal their presence.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":" ","pages":"e23699"},"PeriodicalIF":2.0,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142646705","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":"Teeth Baring as a Model to Understand Complex Facial Signals in a Tolerant Macaque Species.","authors":"Federico Fantoni, Veronica Maglieri, Nicolò Giusti, Chiara Scopa, Virginia Pallante, Antonio Lorenzo Loprete, Elisabetta Palagi","doi":"10.1002/ajp.23697","DOIUrl":"https://doi.org/10.1002/ajp.23697","url":null,"abstract":"<p><p>Facial communication regulates many aspects of social life in human and nonhuman primates. Empirically identifying distinct facial expressions and their underlying functions can help illuminate the evolution of species' communicative complexity. We focused on bared-teeth faces (BTFs), a highly versatile facial expression in the tolerant macaque Macaca tonkeana. By employing a diverse array of techniques (MaqFACS, unsupervised cluster analysis, Levenshtein distance, NetFACS), we quantitatively discriminated two distinct BTFs: bared-teeth (BT) and open mouth bared-teeth (OMBT), and evaluated their distribution across peaceful, playful, and agonistic contexts. Neither BT nor OMBT were context-specific, although BT frequently occurred during peaceful interactions and with low levels of stereotypy. OMBT was highly stereotyped during play, a context involving strong unpredictability. The presence of tongue-protrusion during OMBT was exclusive to peaceful contexts whereas the presence of glabella-lowering during BT and OMBT was specific to agonistic contexts. Hence, BT and OMBT per se are not context-specific, but their contextual relevance hinges on the inclusion of specific key elements. Moving forward, concurrent analyses of stereotypy and specificity should extend beyond our study to encompass other primate and non-primate species, facilitating direct comparisons and revealing how communicative and social complexity coevolve.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":" ","pages":"e23697"},"PeriodicalIF":2.0,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142643244","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":"Stable Isotopes Analysis of Black Lion Tamarins Reveals Increasing Arthropod Consumption When Fruit Productivity Decreases in Forest Fragments.","authors":"Amazone Raskin, Olivier Kaisin, Loïc N Michel, Benjamin Lejeune, Gilles Lepoint, Rodrigo Gonçalves Amaral, Gabriel Pavan Sabino, Márcio Silva Araújo, Gabriela Cabral Rezende, Fany Brotcorne, Laurence Culot","doi":"10.1002/ajp.23698","DOIUrl":"https://doi.org/10.1002/ajp.23698","url":null,"abstract":"<p><p>Given the cryptic and elusive nature of prey consumption, quantifying its contribution to the diet of free-ranging primates using behavioral methods is challenging. In this context, the use of carbon and nitrogen-stable isotopes represents a promising alternative approach. Here, we used stable isotope analysis to estimate the proportion of arthropods and fruits in the diet of black lion tamarins (Leontopithecus chrysopygus), an endangered primate endemic to the Brazilian Atlantic Forest. To do so, we ran stable isotope mixing models using isotopic data from hair samples of black lion tamarins living in six forest fragments showing different levels of habitat quality. Furthermore, we ran linear mixed models to assess the influence of habitat quality-fruit productivity (estimated by tree total basal area) and arthropod biomass - and individual characteristics (sex and body mass) on tamarins' δ¹⁵N values (a proxy for trophic position). Our results revealed that arthropods contributed more to black lion tamarins' diet than reported in previous behavioral studies, suggesting that behavioral observations may considerably underestimate the importance of arthropodivory in the diet of arboreal primates. The degree of arthropodivory and frugivory was similar within groups, in line with the strong group cohesion and synchronization of feeding behaviors of this species and supporting the role of site-specific habitat characteristics on dietary choice. Arthropod consumption was higher in areas with lower fruit productivity and did not increase when arthropod biomass increased, suggesting that fruits represent a limiting but preferred resource for this species. These results demonstrate the dietary plasticity of black lion tamarins in areas of lower forest quality, where they manage to compensate low fruit productivity by shifting to a diet richer in arthropods. Considering that this species occurs within a highly fragmented landscape, preserving and protecting small forest patches remains crucial for the conservation of this species.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":" ","pages":"e23698"},"PeriodicalIF":2.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142612278","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":"The Effect of Sampling Schedule on Assessment of Dietary Measures: Evidence From Blue Monkeys (Cercopithecus mitis stuhlmanni).","authors":"Amanda Johnston, Marina Cords","doi":"10.1002/ajp.23696","DOIUrl":"https://doi.org/10.1002/ajp.23696","url":null,"abstract":"<p><p>Accurately assessing primate diets is important in studies of behavioral ecology and evolution. While previous research has compared sampling methods (scan, focal), we examined how sampling schedule influences accuracy of dietary measures. We define sampling schedule as the combined distribution (random vs. consecutive) and frequency of sampling days within a given month. Under field conditions, time may be required to locate a study group, and we therefore also subtracted 1, 2, or 3 h from the beginning of all non-consecutive days in each sampling schedule to mimic observation time lost to search. From a dense (near daily) 5-year record of feeding behavior derived from focal animal follows of adult females in five wild blue monkey (Cercopithecus mitis) groups, we created data subsets matching various sampling schedules, and compared monthly dietary measures calculated from each subset to those based on the full data set. These measures included (1) the proportion of observation time feeding on fruit, (2) diet composition (three top-ranked food items), (3) species richness of plant diet, (4) Shannon-Wiener diversity index based on plant species, and (5) Holmes-Pitelka index expressing dietary overlap with the previous month. We used generalized linear mixed models to assess how frequency and sampling type (a combination of distribution and hours lost) relate to a subset's deviation from the full data set, where a smaller deviation (or higher chance of matching, for diet composition) implies greater accuracy. For all dietary measures, increasing observation frequency increased accuracy. The response to distribution varied among measures, but sampling types generally differed more at lower frequencies. Deviation varied widely within and between dietary measures, and some sampling schedules resulted in values with large percentage differences from the \"full\" data. Accordingly, when designing and comparing studies, researchers should consider how sampling schedules may influence the accuracy of the dietary measures of interest.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":" ","pages":"e23696"},"PeriodicalIF":2.0,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142612289","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":"Primate field research during a pandemic: Lessons learned from the SARS-CoV-2 outbreak","authors":"Katharine M. Jack,&nbsp;Nelle K. Kulick","doi":"10.1002/ajp.23551","DOIUrl":"10.1002/ajp.23551","url":null,"abstract":"<p>The COVID-19 pandemic abruptly halted most primate field research in early 2020. While international travel bans and regional travel restrictions made continuing primate field research impossible early on in the pandemic, ethical concerns of transmitting the virus from researchers to primates and surrounding human communities informed decisions regarding the timing of resuming research. Between June and September 2020, we surveyed field primatologists regarding the impacts of the pandemic on their research. We received 90 completed surveys from respondents residing in 21 countries, though most were from the United States and Canada. These data provide a valuable window into the perspectives and actions taken by researchers during the early stages of the pandemic as events were still unfolding. Only 2.4% of projects reported continuing research as usual, 33.7% continued with some decrease in productivity, 42.2% reported postponing research projects, and 21.7% reported canceling projects or postponing research indefinitely. Respondents most severely impacted by the pandemic were those establishing new field sites and graduate students whose projects were postponed or canceled due to pandemic-related shutdowns. Fears about increased poaching, the inability to pay local assistants, frozen research funds, declining habituation, disruptions to data collection, and delays in student projects were among the top concerns of respondents. Nearly all the projects able to continue research in any capacity during the early months of the pandemic were run by or employed primate habitat country primatologists. This finding is a <i>major lesson learned</i> from the pandemic; without habitat country scientists, primate research is not sustainable.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"85 11","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajp.23551","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10598688","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":"Picking pithy plants: Pith selectivity by wild white-faced capuchin monkeys, Cebus imitator.","authors":"Allegra N DePasquale,&nbsp;Alice C Poirier,&nbsp;Megan A Mah,&nbsp;Cinthia Villalobos Suarez,&nbsp;Adrian Guadamuz,&nbsp;Saul Cheves Hernandez,&nbsp;Ronald Lopez Navarro,&nbsp;Jeremy D Hogan,&nbsp;Jessica M Rothman,&nbsp;Omer Nevo,&nbsp;Amanda D Melin","doi":"10.1002/ajp.23549","DOIUrl":"https://doi.org/10.1002/ajp.23549","url":null,"abstract":"<p><p>Understanding diet selectivity is a longstanding goal in primate ecology. Deciphering when and why primates consume different resources can provide insights into their nutritional ecology as well as adaptations to food scarcity. Plant pith, the spongy interior of plant stems, is occasionally eaten by primates, but the context is poorly understood. We examine the ecological, mechanical, chemical, and nutritional basis of plant pith selection by a wild, frugivorous-omnivorous primate (Cebus imitator). We test the hypothesis that pith is a fallback food, that is, consumed when fruit is less abundant, and test for differences between plant species from which pith is eaten versus avoided. We collected 3.5 years of capuchin pith consumption data to document dietary species and analyzed \"pith patch visits\" in relation to fruit availability, visits to fruit patches, and climatic seasonality. We analyzed dietary and non-dietary species for relative pith quantity, mechanical hardness, odor composition, and macronutrient concentrations. Capuchins ate pith from 11 of  ~300 plant species common in the dry forest, most commonly Bursera simaruba. We find that pith consumption is not directly related to fruit availability or fruit foraging but occurs most frequently (84% of patch visits) during the months of seasonal transition. Relative to common non-dietary species, dietary pith species have relatively higher pith quantity, have softer outer branches and pith, and contain more terpenoids, a class of bioactive compounds notable for their widespread medicinal properties. Our results suggest that greater pith quantity, lower hardness, and a more complex, terpenoid-rich odor profile contribute to species selectivity; further, as pith is likely to be consistently available throughout the year, the seasonality of pith foraging may point to zoopharmacognosy, as seasonal transitions typically introduce new parasites or pathogens. Our study furthers our understanding of how climatic seasonality impacts primate behavior and sheds new light on food choice by an omnivorous primate.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":" ","pages":"e23549"},"PeriodicalIF":2.4,"publicationDate":"2023-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10553268","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":"Examining postmounting grooming in male golden snub-nosed monkeys to investigate the functions of same-sex mounts","authors":"Pengzhen Huang,&nbsp;Gu Fang,&nbsp;Julie A. Teichroeb,&nbsp;Endi Zhang,&nbsp;Min Chen","doi":"10.1002/ajp.23550","DOIUrl":"10.1002/ajp.23550","url":null,"abstract":"<p>Same-sex mounting behavior has been documented across primate species and several biological functions, that are often difficult to differentiate, have been proposed. Postmounting affiliative behaviors (e.g., embracing and grooming) have been partly overlooked and their performance may more clearly reveal the function of same-sex mounts for different age-sex classes. Here, considering postmounting grooming behaviors (PMG), we tested the <i>affiliation</i> hypothesis for same-sex mounts in an all-male unit (AMU) of captive golden snub-nosed monkeys (<i>Rhinopithecus roxellana</i>) (<i>n</i> = 7−8) and the <i>needing to learn</i> hypothesis in the juveniles of the AMU (<i>n</i> = 4) and the juvenile male from the neighboring one-male unit in Shanghai Wild Animal Park, China from November 2014 to June 2015. A total of 1986 same-sex mounts were recorded from the AMU individuals and the juvenile of the neighboring one-male unit. We found that neither dyadic proximity-based association nor grooming-based affiliation predicted the occurrence of mounts in the AMU, and PMG was more likely to occur in nontense than tense social contexts, providing no support for the <i>affiliation</i> hypothesis. Although dyadic grooming-based affiliation predicted the occurrence of PMG, it exerted no influence on the occurrence of mounts, which was necessary to support the hypothesis. However, consistent with the <i>needing to learn</i> hypothesis, from ages two to four, juveniles' mounting duration increased and they performed pelvic thrusting during mounting more and more often as they grew older. Reciprocated series mounts were much more common among juveniles than other mounting dyads, providing learning opportunities for both participants. The mounter was more likely to groom the mountee at the end of a mount among juveniles than other mounting dyads, suggesting that juvenile mounters may profit from mounting and groom mountees in return for providing them with opportunities to learn copulatory skills. A hypothesis that merits further investigation.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"85 11","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10553260","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":"Removal from the wild endangers the once widespread long-tailed macaque","authors":"Lief Erikson Gamalo,&nbsp;Kurnia Ilham,&nbsp;Lisa Jones-Engel,&nbsp;Mike Gill,&nbsp;Rebecca Sweet,&nbsp;Brooke Aldrich,&nbsp;Phaivanh Phiapalath,&nbsp;Tran Van Bang,&nbsp;Tanvir Ahmed,&nbsp;Sarah Kite,&nbsp;Sharmini Paramasivam,&nbsp;Hun Seiha,&nbsp;Muhammad Z. Zainol,&nbsp;Daniel R. K. Nielsen,&nbsp;Nadine Ruppert,&nbsp;Agustin Fuentes,&nbsp;Malene F. Hansen","doi":"10.1002/ajp.23547","DOIUrl":"10.1002/ajp.23547","url":null,"abstract":"<p>In 2022, long-tailed macaques (<i>Macaca fascicularis</i>), a once ubiquitous primate species, was elevated to Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. In 2023, recognizing that the long-tailed macaque is threatened by multiple factors: (1) declining native habitats across Southeast Asia; (2) overutilization for scientific, commercial, and recreational purposes; (3) inadequate regulatory mechanisms; and (4) culling due to human–macaque conflicts, a petition for rulemaking was submitted to the United States Fish and Wildlife Service to add the species to the US Endangered Species Act, the nation's most effective law to protect at risk species. The long-tailed macaque remains unprotected across much of its geographical range despite the documented continual decline of the species and related sub-species and the recent IUCN reassessment. This commentary presents a review of the factors that have contributed to the dramatic decline of this keystone species and makes a case for raising the level of protection they receive.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"86 3","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajp.23547","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10251956","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":"Effects of provisioning on the activity budget and foraging strategies of black-and-white snub-nosed monkeys (Rhinopithecus bieti) in the Baima Snow Mountain Nature Reserve, Yunnan, China","authors":"Hong-Bo Li,&nbsp;Jing Sun,&nbsp;Lun-Hong Li,&nbsp;Ying Zhou,&nbsp;Xue-Lan Fang,&nbsp;Bo-Yan Li,&nbsp;Long-Jie Guo,&nbsp;Ying Geng,&nbsp;Chun-Ping Wang,&nbsp;Zhi-Pang Huang,&nbsp;Paul A. Garber,&nbsp;Yin Yang,&nbsp;Liang-Wei Cui,&nbsp;Wen Xiao","doi":"10.1002/ajp.23548","DOIUrl":"10.1002/ajp.23548","url":null,"abstract":"<p>Provisioning can significantly affect the ranging patterns, foraging strategies, and time budget of wild primates. In this study, we document for the first time, the effects of provisioning on the activity budget and foraging effort in an Asian colobine. Over 3-years, we used an instantaneous scanning method at 10-min intervals to collect data on the activity budget of a semiprovisioned breeding band (SPB) of black-and-white snub-nosed monkeys (<i>Rhinopithecus bieti</i>) (42–70 individuals) at Xiangguqing (Tacheng), Yunnan, China. We then compared the effects of provisioning in our study band with published data on a sympatric wild nonprovisioned breeding band (NPB) of <i>R. bieti</i> (ca. 360 monkeys) at the same field site. The SPB spent 25.6% of their daytime feeding, 17.1% traveling, 46.9% resting, and 10.3% socializing. In comparison, the NPB devoted more time to feeding (34.9%) and socializing (14.1%), less time to resting (31.3%), and was characterized by a greater foraging effort (1.74 versus 0.96, foraging effort = (feeding + traveling)/resting; see Methods). There was no difference between bands in the proportion of their activity budget devoted to traveling (15.7% vs. 17.1%). In addition, the SPB exhibited a more consistent activity budget and foraging effort across all seasons of the year compared to the NPB. These findings suggest that the distribution, availability, and productivity of naturally occurring feeding sites is a major determinant of the behavioral strategies and activity budget of <i>R. bieti</i>. Finally, a comparison of our results with data on six nonprovisioned <i>R. bieti</i> bands indicates that caution must be raised in meta-analyses or intraspecific comparisons of primate behavioral ecology that contain data generated from both provisioned and nonprovisioned groups.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"85 11","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10201280","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":"Hand preference in wild crab-eating capuchin monkeys (Sapajus libidinosus) in the coastal area of Northest Brazil","authors":"Roberta Salmi,&nbsp;Kristie Le,&nbsp;Jardeani M. Silva,&nbsp;Daiana P. Conceição,&nbsp;Andrea Presotto,&nbsp;Ricardo Rodrigues dos Santos","doi":"10.1002/ajp.23546","DOIUrl":"10.1002/ajp.23546","url":null,"abstract":"<p>Handedness is a fundamental human trait, although recent research, especially on nonhuman primates, has shown that it is displayed by other animals as well (e.g., chimpanzees, gorillas). In this study, we explore hand preference in wild crab-eating tufted capuchin monkeys (<i>Sapajus libidinosus</i>) inhabiting a mangrove forest located on the coastal area of Northeast Brazil (Maranhão State). Tufted capuchin monkeys at our site use facultatively wooden tools to crack open crabs. We observed hand preference in 12 subjects who spontaneously participated in experiment sessions, in which we provided crabs and tools on wooden platforms. We recorded (using events and bouts) two unimanual tasks, (tool or crab) grabbing and (tool or crab) pounding, and one bimanual task, crab pulling, where one hand kept the crab in place while the other pulled off parts of the crab. Hand preference increased with greater strength needed to perform the task and its complexity. While only 17%−25% of capuchins showed hand preference during grabbing, 44%−64% showed hand preference during pounding, and most subjects 64%−80% displayed a right-hand preference when performing the bimanual task, for which all lateralized individuals were right-handed. Hand preference did not vary between adults and juvenile individuals and was not consistent across tasks. Group-level hand preference was found only for the bimanual task, for which all lateralized individuals were right-handed. Our findings are in concordance with those of other primate studies showing the emergence of hemispheric specialization for bimanual actions, highlight the importance of conducting such studies on diverse type of tasks, and show the feasibility to conduct experimental manipulation under natural conditions.</p>","PeriodicalId":7662,"journal":{"name":"American Journal of Primatology","volume":"85 11","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/ajp.23546","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10119971","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}