Interactions with humans reduce the success of foraging for anthropogenic food by capuchin monkeys (Sapajus libidinosus) in Brasília National Park, Brazil.

The progressive growth of urban environments has increasingly forced populations of nonhuman primates to coexist with humans in many cities, which has resulted in problems such as behavioral alterations, conflicts with humans, and threats to the health of the monkeys, due to their consumption of anthropogenic foodstuffs. These anthropogenic foods, which are rich in calories, are the principal driver of the proximity between humans and primates, even though the acquisition of these foods tends to be risky for the monkeys and involve a variety of challenges derived from specific features of the urban environment. The present study evaluated the success/risk relationship of foraging for anthropogenic food by tufted capuchins (Sapajus libidinosus) in Brasília National Park. The data were analyzed using a binary logistic regression, with the backward-stepwise Wald method, to investigate the factors related to the foraging success of the capuchins, considering variables such as their sex and age, the type of approach and its context, and interactions with humans. The capuchins were influenced by the anthropogenic context, which affected their foraging strategies and diet. Interactions with humans reduced the success of foraging for anthropogenic foods. Conflicts between humans and the capuchins were common, especially in the context of access to food. The capuchins thus preferred to access feeding resources directly, probably due to the reduced human interference, which resulted in greater foraging success for unattended food brought by park visitors and the raiding of trash cans. Based on the observed behavior patterns, a number of measures can be proposed to mitigate these conflicts. These recommendations include not bringing food into areas frequented by the capuchins, not reacting to approaching animals, and removing all trash generated during a visit. A cleaning team dedicated to the maintenance of the visitation area free of anthropogenic waste is also be recommended.

Mapping nut-cracking in a new population of wild capuchin monkeys (Sapajus libidinosus) at Ubajara National Park, Brazil.

Populations of bearded capuchin monkeys (Sapajus libidinosus) vary in their tool use behaviors, with some of this divergence regarded as culturally determined. The use of stone tools, primarily to crack open encased foods, is widespread among bearded capuchins living in dry habitats (Caatinga and Cerrado). Significant diversity in targets, processed foods, material, and size of tools is observed across populations. However, so far, only a few sites have been systematically studied, and we are still distant from a representative picture of the range of variation in capuchins' culture. In this study, we did a systematic assessment of stone tool use sites in the Ubajara National Park (UNP), in the Caatinga region of Ceará, Brazil, recording and measuring stone tools, processed foods, and available lithic resources as part of an extensive comparative research, the CapCult project. We found indirect and direct evidence that capuchin monkeys at UNP customarily use hammerstones and anvils to process at least two species of palm nuts, macauba (Acrocomia aculeata) and the harder babaçu (Attalea speciosa). Most of the anvils were rock surfaces and had leftovers of only one palm nut species. The hammerstones used to process both palm nuts were not significantly different in weight, although the ones used for Ac. aculeata were longer. We found a higher frequency of nut-cracking sites in the drier lowland area of the park, reflecting differences in the density of the most common palm species, Ac. aculeata, and availability of raw stone material. The stone tool use observed in UNP is within the scope of previously reported in savannah capuchin populations. Our study widens the knowledge of stone tool-use diversity in wild capuchin monkeys, which could contribute to shaping conservation policy, including cultural traits.

Diet and seed dispersal of bearded capuchin monkeys (Sapajus libidinosus) in Brasilia National Park.

The dietary ecology of a species can provide information on habitat requirements, food resources, and trophic interactions, important to guide conservation efforts of wildlife populations in endangered habitats. In this study, we investigated the dietary ecology of bearded capuchin monkeys (Sapajus libidinosus) in Brasilia National Park, in the endangered Cerrado biome of central Brazil. To obtain diet composition and evaluate the role of these primates as seed dispersers of local tree species, fecal sample collections and feeding observations were performed for a 7-month period. To determine whether seeds germinated better after passing through a primate gut, we conducted germination trials with (i) pulped seeds from trees, (ii) depulped seeds from trees, (iii) seeds from feces planted with feces, and (iv) seeds from feces planted without feces. During experimental procedures, 7308 seeds from 8 families and 10 species were planted. We found that S. libidinosus spent more time feeding on fruits than on any other food item and the diet consisted of 33 plant species from 21 families. However, 20% of their diet consisted of anthropic food. Most seeds planted with feces germinated faster compared to seeds in other experimental treatments, suggesting that passing through the gut and being deposited with fecal material is advantageous. The bearded capuchins also defecated many medium- (5 species) and large-sized (2 species) seeds that may be inaccessible to smaller arboreal frugivores. The results obtained emphasize the important role of bearded capuchins as seed dispersers for the maintenance and conservation of the endangered Cerrado biome.

Phylogeography, genetic diversity, and intraspecific genetic structure of the black-horned capuchin (Sapajus nigritus).

Recent molecular studies have clarified the overarching taxonomy of capuchin monkeys, but intraspecific genetic diversity remains unexplored for most capuchin species. One example is Sapajus nigritus, the southernmost capuchin monkey, found in Brazil and Argentina; its phenotypic diversity has been recognized as two geographic subspecies, but the intraspecific genetic structure of this taxon is poorly known. Here, we sampled across most of this species' geographic distribution, producing a newly sequenced data set for genetic analyses that included 78 individuals from 14 populations. We investigated the intraspecific diversity, genetic structure, and evolutionary history using three mitochondrial markers. Our results indicated that S. nigritus populations exhibited high levels of genetic structure. We found strong support for two monophyletic clades within this species with a deep phylogenetic split, and clear separation from other related taxa. Vicariance events seem to have played a prevalent role in shaping S. nigritus genetic differentiation. The Paraíba do Sul River may have driven the deep divergence between southern and northern clades, whereas the Tietê River may have had a weaker, more recent effect on the divergence of populations within the southern clade.

Observation of Masturbation After Visual Sexual Stimuli From Conspecifics in a Captive Male Bearded Capuchin (Sapajus libidinosus).

Masturbation is part of the natural behavioral repertoire of primates, with visual sexual stimuli known to trigger this behavior. Here, we report masturbation events triggered by visual sexual stimulus (VSS) in the South American primate Sapajus libidinosus. We observed a multi-male multi-female captive colony of 17 bearded capuchins between January and October 2014. Over this period, we registered 11 copulation events, 68 attempt copulations, and five masturbation events. The same low-ranking male (named Fu) performed all masturbation events. Fu directly looked at other individuals engaged in sexual displays while he masturbated in three events. The masturbation events associated with VSS lasted up to 2 min and 40 s. Our observations show that VSS can trigger masturbation in capuchin monkeys. The low hierarchy rank of the male, and the consequent lack of mating opportunities in the multi-male multi-female recently formed group in captivity, may have prompted the masturbation events.

Impacts of climate change and habitat loss on the distribution of the endangered crested capuchin monkey (Sapajus robustus).

The crested capuchin monkey (Sapajus robustus) is endemic to the Atlantic Forest and its transition areas within Cerrado in Brazil. The species is currently threatened by habitat loss and has been classified as endangered by the IUCN Red List of Threatened Species since 2015. We used ecological niche models built with MaxEnt to predict the potential impact of climate change on the distribution of this species. The models were projected onto the reference climate, considering six climate scenarios (three Global Climate Models and two Representative Concentration Pathways) from IPCC for 2050 and 2070. We showed that while the amount of suitable area is expected to change little across the species' range in most evaluated climate scenarios, climatic conditions may significantly deteriorate by 2070 in the pessimistic scenario, especially in currently warmer and dryer areas to the west. As seen on other capuchin monkeys, the potential use of tools by crested capuchins may increase the chances of the species adaptation to novel harsher environmental conditions. The major negative impacts across the species range also include habitat loss and fragmentation so that the conservation of the species relies on the protection of the forest remnants in the center of its distribution, which can harbor populations of the species in current and future climate scenarios.

Comparative morphofunctional analysis of axial skeleton excluding the skull of primates based on the anatomical, radiographic, and tomographic description of the black-striped capuchin (Sapajus libidinosus Spix, 1823).

Comparative anatomy the basis for studies of evolution, and radiographic and tomographic aspects, as auxiliary methods in the investigation of anatomical particularities, reinforce evolutionary research. Therefore, the aim of this study was to describe the vertebrae, sternum, and ribs of the capuchin monkey (Sapajus libidinosus) by means of anatomical dissection and radiographic and tomographic images. To this purpose, four cadavers were used in the anatomical analysis and five living animals for the imaging exams. The bones were described and compared with data from other primates species found in literature. Student's t-test for independent samples was performed. The vertebral column of the comprises seven cervical, 13 or 14 thoracic, five or six lumbar, two or three sacral, and 23 or 24 caudal vertebrae. The atlas is characterized by three foramina on the wing. The seventh cervical vertebra had a transverse foramen in one specimen. The anticlinal vertebra is always the penultimate thoracic one, the ninth pair of ribs is always the last sternal pair, and the last two are buoyant. The sternal was composed of five or six sternebrae. The lumbar vertebrae showed a bifurcated spinous process. Three different sacral morphologies were observed. The structures identified macroscopically could be well determined through radiographic and tomographic images. S. libidinosus presented anatomical characteristics more similar to those of man and of platirrinos monkeys. The knowledge obtained by macroscopic anatomy and tomographic and radiological exams contributes significantly to comparative evolutionary studies.

Ontogenesis of sociability of wild immature capuchin monkeys (Sapajus libidinosus): Sex more than personality explains interindividual variation.

Sociability is a fundamental trait that social animals need to survive and reproduce in societies. Sociability predicts how an individual can consistently interact with its conspecifics across time and situations. By studying capuchin monkeys (Sapajus libidinosus), a neotropical primate with complex social behavior and high cognitive capacity, our research aims to analyze the development of the social axis of personality of immature individuals, from birth to the third year of life. We studied wild monkeys belonging to a group with infants, juveniles, and adults of both sexes that inhabits northeastern Brazil. We analyzed the behavior of 12 immature capuchins (6 males and 6 females) in 94 h of videos recorded weekly from birth until 36 months, through daily focal sampling. We verified whether there was intraindividual consistency throughout development by fitting regression models for the effect of age on initiating affiliative social behaviors, controlling for monkey identity and sex. Our results indicate that the individuals of this study exhibit high variation in the initiation of behaviors at the beginning of infancy; there was low repeatability and high intra-individual variation during the first 3 years of life of these individuals, indicating that the social personality is not consolidated in this period. Immature females were more sociable than immature males. Therefore, differences in sociability in early life of bearded capuchin monkeys are best explained by sex rather than personality. We suggest that the high initial behavioral variation in the social axis of personality allows for plasticity influenced by the environment throughout development. The high sociability of females in infancy may be related to female philopatry and their high sociability in adulthood.

Influence of landscape structure on previous exposure to Leptospira spp. and Brucella abortus in free-living neotropical primates from southern Brazil.

The environments in which neotropical primates live have been undergoing an intense fragmentation process, constituting a major threat to the species' survival and causing resource scarcity, social isolation, and difficulty in dispersal, leaving populations increasingly vulnerable. Moreover, the proximity of wild environments to anthropized landscapes can change the dynamics of pathogens and the parasite-host-environment relationship, creating conditions that favor exposure to different pathogens. To investigate the previous exposure of free-living primates in Rio Grande do Sul State (RS), southern Brazil, to the bacterial agents Leptospira spp. and Brucella abortus, we investigated agglutinating antibodies against 23 serovars of Leptospira spp. using the microscopic agglutination test and B. abortus acidified antigen test in primate serum samples; 101 samples from primates captured between 2002 and 2016 in different forest fragments were used: 63 Alouatta caraya, 36 Alouatta guariba clamitans, and 02 Sapajus nigritus cucullatus. In addition, the forest remnants where the primates were sampled were characterized in a multiscale approach in radii ranging from 200 to 1400 m to investigate the potential relationship of previous exposure to the agent with the elements that make up the landscape structure. The serological investigation indicated the presence of antibodies for at least one of the 23 serovars of Leptospira spp. in 36.6% (37/101) of the samples analyzed, with titers ranging from 100 to 1600. The most observed serovars were Panama (17.8%), Ballum (5.9%), Butembo (5.9%), Canicola (5.9%), Hardjo (4.9%), and Tarassovi (3.9%); no samples were seropositive for Brucella abortus. Decreased forest cover and edge density were the landscape factors that had a significant relationship with Leptospira spp. exposure, indicating that habitat fragmentation may influence contact with the pathogen. The data generated in this study demonstrate the importance of understanding how changes in landscape structure affect exposure to pathogenic microorganisms of zoonotic relevance. Hence, improving epidemiological research and understanding primates' ecological role in these settings can help improve environmental surveillance and conservation strategies for primate populations in different landscapes.

Changes in Intraspecific Diversity of the Arbuscular Mycorrhizal Community Involved in Plant-Plant Interactions Between Sporobolus robustus Kunth and Prosopis juliflora (Swartz) DC Along an Environmental Gradient.

The intensification of biological processes coping with salt stress became a major issue to mitigate land degradation. The Sine-Saloum Delta in Senegal is characterized by salt-affected soils with vegetation dominated by salt-tolerant grass Sporobolus robustus and shrubs like Prosopis juliflora. Plant experiments in controlled conditions suggested that arbuscular mycorrhizal (AM) fungi might be the key actors of facilitation process observed between S. robustus and P. juliflora, but the AM fungal community determinants are largely unknown. The current field-based study aimed at (1) characterizing the environmental drivers (rhizosphere physico-chemical properties, plant type and season) of the AM fungal community along an environmental gradient and (2) identifying the AM fungal taxa that might explain the S. robustus-mediated benefits to P. juliflora. Glomeraceae predominated in the two plants, but a higher richness was observed for S. robustus. The pH and salinity were the main drivers of AM fungal community associated with the two plants, negatively impacting richness and diversity. However, while a negative impact was also observed on mycorrhizal colonization for S. robustus, P. juliflora showed opposite colonization patterns. Furthermore, no change was observed in terms of AM fungal community dissimilarity between the two plants along the environmental gradient as would be expected according to the stress-gradient and complementary hypotheses when a facilitation process occurs. However, changes in intraspecific diversity of shared AM fungal community between the two plants were observed, highlighting 23 AM fungal OTUs associated with both plants and the highest salinity levels. Consequently, the increase of their abundance and frequency along the environmental gradient might suggest their potential role in the facilitation process that can take place between the two plants. Their use in ecological engineering could also represent promising avenues for improving vegetation restoration in saline Senegalese's lands.

Haematology, physiological parameters, morphometry and parasitological status of rescued bearded capuchin monkeys (Sapajus libidinosus).

BACKGROUND: There are few studies on the physiology and haematology of rescued bearded capuchin monkeys. These are necessary to better understand the health and welfare status of the animals, including when performing reintroductions, and to avoid zoonoses. METHODS: We aimed to obtain physiological and haematological values, morphometry and parasitological status of 26 bearded capuchins in two rescue centres in Northeast Brazil. RESULTS: We found sex- and age-related differences in respiratory rate, body weight and body mass index, but not haematology. The haematological values obtained were significantly different from published data but within the reference intervals for the species. Animals infected with Ancylostoma spp. had significantly lower values in the parameters: haemoglobin concentration, mean corpuscular volume and mean corpuscular haemoglobin concentration than non-infected individuals. CONCLUSION: Physiological and haematological values of rescued capuchins were similar to those found in previous studies. Ancylostomiasis appears to cause alterations to haematological values of this species.

Prevalence and description of dental disorders in skulls of free-living wild primates from Paraná State, Brazil.

BACKGROUND: Non-human primates can present oral diseases. However, differences among the dentition of the various species make it difficult to understand their dental features and associated diseases. This research hypothesizes that the prevalence of dental disorders varies in the species studied according to distinct types of diet. METHODS: Forty-five syncraniums of the species Alouatta caraya, Alouatta guariba clamitans, Sapajus nigritus, Callithrix jacchus, and Callithrix penicillata were evaluated by visual inspection, magnifying glasses, and on cone-beam computed tomography. RESULTS: Disorders identified consisted of missing teeth before death, agenesis, dental calculus, dental wear, dental staining, dental fracture, exposure of pulp chamber, alveolar bone resorption, tooth discoloration, and persistence of deciduous teeth. Alouatta guariba clamitans presented the most disorders. CONCLUSIONS: The results suggest that neotropical primates have a high prevalence of dental changes, even in free-living conditions, and that the differences observed among them may be associated with different diet patterns.

Anatomy applied to image diagnosis of the hind limb in the black-striped capuchin (Sapajus libidinosus Spix, 1823).

The knowledge of anatomy and imaging exams emerges as an important tool in the study of evolutionary processes of a species, in the elaboration of diagnosis, and the successful choice of the appropriate clinical and surgical procedures. Therefore, this study aims to describe the osteology of the hind limb of Sapajus libidinosus by means of gross, radiographic, and tomographic images. Four cadavers were used in the macroscopic analysis and five animals for the imaging exams, of which four were eventually euthanized and added to the macroscopic study. For imaging exams, they were kept anesthetized. All bones of the hind limb were documented, their structures were described, and compared with data in the literature from human and nonhuman primates. We have performed Student's t test for independent samples. There was no statistical difference between the sexes regarding the length of the hind limb bones. The coxal bone was largely well described using imaging methods. A small penile bone was present at the tip of the penis and it could be identified by all analysis methods. The femur, as well as the tibia and fibula, were not well portrayed in their proximal and distal epiphyses by radiography (Rx). However, they were well identified on tomography. No third trochanter was observed in the femur and the patella had a triangular shape. All the structures described by gross anatomy of the tarsus and metatarsus could be identified by Rx and tomography. More subtle structures, such as the popliteal notch on the tibia, and the gluteal tuberosity pectineal line and facies aspera on the coxal bone, were not identified by medical imaging. S. libidinosus presented anatomical characteristics that were similar to those of larger New World and Old World monkeys, including man. This suggests it's value as an experimental model for studies in recent primates.

A robust tool kit: First report of tool use in captive crested capuchin monkeys (Sapajus robustus).

Primate tool use is of great interest but has been reported only in a limited number of species. Here we report tool use in crested capuchin monkeys (Sapajus robustus), an almost completely unstudied robust capuchin species. Crested capuchins and their sister species, the yellow-breasted capuchin, diverged from a common ancestor over 2 million years ago, so this study fills a significant gap in understanding of tool use capacity and variation within the robust capuchin monkey radiation. Our study group was a captive population of seven individuals at the Santa Ana Zoo in California. The monkeys were given no prior training, and they were provided with a variety of enrichment items, including materials that could be used as tools as well as hard-to-access resources, for open-ended interactions. In 54 observation hours, monkeys performed eleven tool use actions: digging, hammering, probing, raking, sponging, striking, sweeping, throwing, waving, wedging, and wiping. We observed tool modification, serial tool use, and social learning opportunities, including monkeys' direct observation of tool use and tolerated scrounging of foods obtained through tool use. We also observed significant individual skew in tool use frequency, with one individual using tools daily, and two individuals never using tools during the study. While crested capuchins have never been reported to use tools in the wild, our findings provide evidence for the species' capacity and propensity for tool use, highlighting the urgent need for research on this understudied, endangered primate. By providing detailed data on clearly identified S. robustus individuals, this study marks an effort to counteract the overgeneralization in the captive literature in referring to any robust capuchins of unknown provenance or ancestry as Cebus apella, a practice that obfuscates potential differences among species in tool use performance and repertoire in one of the only species-rich tool-using genera in the world.

Osteology applied to image diagnosis of the forelimb of the black-striped capuchin (Sapajus libidinosus Spix, 1823).

Macroscopic bone analysis and evaluation through imaging methods are essential in the recognition of natural and altered structures. Therefore, this study aimed at describing the osteology the thoracic limb of Sapajus libidinosus in bone pieces, identifying them in radiographic and tomographic images. For this, four cadavers were used in the macroscopic analysis and five animals for the imaging exams, of which four were euthanized and added to the macroscopic stage. For imaging exams, the animals were kept anesthetized. All bones were documented, structures described, and compared with literature data from human and nonhuman primates. There was no statistical difference between males and females regarding the length of the forelimb bones. Most of the bone structures of the scapula were well identified in the imaging methods, being more restricted in the ventrodorsal projection. The clavicle presented very limited visualization. The humerus, as well as the radius and ulna, were not well portrayed in their proximal and distal epiphyses by radiography. However, they were well identified on tomography. All structures described in the macroscopic image of the carpal and metacarpal bones could be identified through radiography and tomography, and the radiographic examination of this region is an excellent method for identifying fractures. The glenoid notch of the scapula was not visualized by any imaging method. S. libidinosus presented anatomical characteristics more similar to those of neotropical primates and man, being a great indicator of an experimental model for studies in these species.

Diet, activity patterns, and home range use in forest and cultivated areas for one wild group of endangered crested capuchin monkeys (Sapajus robustus) in Reserva Natural Vale, Espírito Santo, Brazil.

Robust capuchin monkeys (Sapajus spp.) are distributed widely in the Neotropics and may be able to survive in modified landscapes because of their omnivorous, opportunistic diet. The poorly known and endangered crested capuchin monkey (Sapajus robustus) is endemic to the Atlantic Forest in Bahia, Minas Gerais and Espírito Santo states, Brazil. We collected data on diet and home range for a crested capuchin group with access to forest and cultivated areas. We hypothesized that with access to cultivated exotic fruit, capuchins would use cultivated areas more for feeding during the season of fruit scarcity in the surrounding forest and have a small home range size because of higher fruit availability. Both the forest and the cultivated areas peaked in fruit availability in the wet season, with a low proportion of trees producing fruit in the dry season; cultivated areas had a higher proportion of trees in fruit compared to the forest throughout the study. While monkeys consumed exotic fruits like jackfruit and oil palm, we recorded more samples of them eating forest fruits than exotic fruits in all but 1 month, and they consumed a more diverse array of forest fruits (56 species) but only six exotic species. Home range size was relatively small compared with other studies: 120.5 ha across the year (wet season 102 ha, dry season 111.5 ha). Natural and human-intensified fruit sources in a protected area without hunting may have allowed monkeys to maintain a smaller home range size. The group composition changed during the study; this also likely influenced home range use. Studies focused on robust capuchin groups that utilize agricultural or cultivated foods may underestimate home range needs for groups without access to human-intensified food sources. Studying crested capuchin ecology in additional locations will be important for establishing a sound species conservation program.

Assessment of the technique of the anesthetic block of the Brachial Plexus by Supraclavicular approach in Sapajus libidinosus (SPIX, 1823).

BACKGROUND: The aim of study was to evaluate the efficacy of the supraclavicular brachial plexus block technique in Sapajus libidinosus. METHODS: Were used eight animals, which were sedated, anesthetized, kept under hypnosis, and submitted to plexus block using a neurolocalizer. The physiological parameters, the nociception and response threshold (mA), were evaluated before and after the block. The response to electrical stimulation and cutaneous sensitivity were evaluated. The groups were compared by the Tukey or Friedman test at 5%. RESULTS: The technique promoted blockage of the plexus, and movement of the thoracic limb in response to electrical stimulation decreased after 10 minutes. The applied milliampere increased after 5 minutes. The cutaneous sensitivity reflex decreased. The average time of return of spontaneous limb movement exceeded 50 minutes. CONCLUSIONS: The use of 5mg/kg of lidocaine 2% promoted loss of cutaneous sensitivity and limb muscle relaxation during the evaluation period.

Serological survey and DNA screening of Leptospira spp. in free-living adult tufted capuchin monkeys (Cebus apella nigritus) in a forest reserve Southeast São Paulo State, Brazil.

BACKGROUND: Leptospirosis is an important anthropozoonosis. The study investigated the presence of anti-Leptospira antibodies and detection of Leptospira spp DNA in the urine as well as the biochemical profile in Neotropical wild primates living in a forest reserve from Southeast São Paulo State, Brazil. METHODS: Blood samples were obtained from 50 adult tufted capuchin monkeys (Cebus apella nigritus). Urine samples were obtained only from male primates. The screening for antibodies against Leptospira spp was evaluated by microscopic agglutination test (MAT). Leptospira DNA in the urine was evaluated by polymerase chain reaction (PCR) considering the target gene LipL32. Biochemical profile was evaluated by using a spectrophotometer. RESULTS: The MAT results included 39 (78%) serum reactive animals with the proportions of 28/39 males and 11/39 females. The most frequent reactive serogroups were Icterohemorrhagiae, Canicola, and Autumnalis. All urine samples were negative for leptospiral DNA. There were no significant differences between sexes for aspartate aminotransferase (AST) and alkaline phosphatase values, but alanine aminotransferase (ALT), creatinine, glucose, and urea were significantly higher in males. CONCLUSIONS: Tufted capuchin monkeys were sera reactive against leptospirosis. Prevalence was similar for the 2 sexes. Leptospiral DNA was not detected in the urine of sera reactive primates tested by the MAT method. ALT, creatinine, glucose, and urea values were higher in male animals.

Anticipating future actions: Motor planning improves with age in wild bearded capuchin monkeys (Sapajus libidinosus).

Self-directed object manipulation tasks illuminate development of motor planning. Grasping strategies that lead to good object control to perform the following action(s) reveal second-order motor planning. Motor planning for efficient grips develops slowly in children. Age-related differences in other primates have been poorly investigated. Here, we investigated anticipatory motor planning of infant, juvenile and adult wild capuchin monkeys grasping a horizontally positioned stick baited to the left or right side (a version of the elevated spoon task). We recorded the grasps capuchins used to bring the baited end of the stick to the mouth. The percentage of efficient radial grips positively correlated with age and adults used efficient grips significantly more frequently than infants. Adult wild capuchins' use of radial grips was higher than that reported for adult captive capuchins in similar tasks, suggesting that experience throughout life may influence motor anticipation. Self-directed object manipulation tasks will be useful to compare this aspect of cognition across primates. A video abstract of this article can be viewed at https://youtu.be/a1Zbr_AQkb8.

Ontogeny and sex differences in object manipulation and probe tool use by wild tufted capuchin monkeys (Sapajus libidinosus).

Tufted capuchin monkeys (Sapajus spp.) are the only Neotropical Primates that regularly use tools in the wild, but only one population of bearded capuchin monkeys (Sapajus libidinosus) is known to habitually use sticks as probes. In this population, males are typically the only sex to use stick tools, something unexpected, since there are no obvious physical constraints, and females do use stone tools in the wild and sticks in experimental conditions. We investigated the development of probe tool use in eight infants to clarify whether social influences on learning varied between the sexes, as tool use learning by capuchin monkeys is a socially biased process. We found that in the first 10 months of age, females manipulate sticks as much as males, but after 10-12 months of age, males begin to manipulate them at higher frequencies. We examined if social connections-as opportunities for social learning-could explain this difference and verified that, on close distance social networks, infant males and females have similar connections with older males. However, males observe probe tool use events more often than females when close to such events. The higher frequency of manipulation of sticks, as well as the higher rates of probe tool use observation, appear to be the key to understand why only males are probe tool users in this population. Since there are only male potential models of probe use, a sex motivational bias could explain the sex difference in observation; a bias in observation could explain the differences in manipulation-and manipulation rates would certainly influence the chances of individual, trial-and-error learning (a case of "local/stimulus enhancement").