Radiographic Measurements of the Hip Joint in Capuchin Monkeys (Sapajus spp.).

BACKGROUND: Radiographs are useful for the initial evaluation of the hip joints. The information can be utilized for the betterment of animal health or other goals such as anatomic studies and gait analysis, among others. Therefore, this study aimed to evaluate radiographic measurements of the hip joint in capuchin monkeys, kept under human care at a reference center for wildlife. METHODS: Twelve capuchin monkeys (Sapajus spp.) (three adult males, seven adult females, and two sub-adult females) were evaluated. Ventrodorsal radiographic views were taken under chemical restraint. All measurements on the digital images were performed in triplicate by one examiner. RESULTS AND CONCLUSIONS: None of the measurements evaluated were statistically different between males and females. No statistical differences were found between hind limbs. The mean (±SD) Norberg angle was 104.92° (±2.82°) and the Wiberg angle was 15.26° (±1.86°). The percentage of the femoral head covered by the acetabulum was 68.57% (±3.65%) and the acetabular index depth to width ratio was 54.66% (±3.85%). In conclusion, the radiographic measurements showed certain morphological features of the hip joint in Sapajus spp. that contribute to improving species knowledge.

Wild capuchin monkeys as a model system for investigating the social and ecological determinants of ageing.

Studying biological ageing in animal models can circumvent some of the confounds exhibited by studies of human ageing. Ageing research in non-human primates has provided invaluable insights into human lifespan and healthspan. Yet data on patterns of ageing from wild primates remain relatively scarce, centred around a few populations of catarrhine species. Here, we introduce the white-faced capuchin, a long-lived platyrrhine primate, as a promising new model system for ageing research. Like humans, capuchins are highly social, omnivorous generalists, whose healthspan and lifespan relative to body size exceed that of other non-human primate model species. We review recent insights from capuchin ageing biology and outline our expanding, integrative research programme that combines metrics of the social and physical environments with physical, physiological and molecular hallmarks of ageing across the natural life courses of multiple longitudinally tracked individuals. By increasing the taxonomic breadth of well-studied primate ageing models, we generate new insights, increase the comparative value of existing datasets to geroscience and work towards the collective goal of developing accurate, non-invasive and reliable biomarkers with high potential for standardization across field sites and species, enhancing the translatability of primate studies.This article is part of the discussion meeting issue 'Understanding age and society using natural populations'.

Ontogenetic biomechanics of tufted (Sapajus) and untufted (Cebus) capuchin mandibles.

OBJECTIVES: Cortical bone geometry is commonly used to investigate biomechanical properties of primate mandibles. However, the ontogeny of these properties is less understood. Here we investigate changes in cortical bone cross-sectional properties throughout capuchin ontogeny and compare captive versus wild, semi-provisioned groups. Tufted capuchins (Sapajus spp.) are known to consume relatively hard/tough foods, while untufted capuchins (Cebus spp.) exploit less mechanically challenging foods. Previous research indicates dietary differences are present early in development and adult Sapajus mandibles can resist higher bending/shear/torsional loads. MATERIALS AND METHODS: This study utilized microCT scans of 22 Cebus and 45 Sapajus from early infancy to adulthood from three sample populations: one captive Cebus, one captive Sapajus, and one semi-provisioned, free-ranging Sapajus. Mandibular cross-sectional properties were calculated at the symphysis, P3, and M1. If the tooth had not erupted, its position within the crypt was used. A series of one-way ANOVAs were performed to assess differences between and within the sample populations. RESULTS: Mandible robusticity increases across ontogeny for all three sample populations. Sapajus were better able to withstand bending and torsional loading even early in ontogeny, but no difference in shear resistance was found. Semi-provisioned, free-ranging Sapajus tend to show increased abilities to resist bending and torsional loading but not shear loading compared to captive Sapajus. DISCUSSION: This study helps advance our understanding of the primate masticatory system development and opens the door for further studies into adaptive plasticity in shaping the masticatory apparatus of capuchins and differences in captive versus free-ranging sample populations.

Tool skill impacts the archaeological evidence across technological primates.

The archaeological record offers insights into our evolutionary past by revealing ancient behaviour through stone and fossil remains. Percussive foraging is suggested to be particularly relevant for the emergence of tool-use in our lineage, yet early hominin percussive behaviours remain largely understudied compared to flaked technology. Stone tool-use of extant primates allows the simultaneous investigation of their artefacts and the associated behaviours. This is important for understanding the development of tool surface modification, and crucial for interpreting damage patterns in the archaeological record. Here, we compare the behaviour and the resulting material record across stone tool-using primates. We investigate the relationship of nut-cracking technique and stone tool modification across chimpanzees, capuchins, and long-tailed macaques by conducting standardized field experiments with comparable raw materials. We show that different techniques likely emerged in response to diverse nut hardness, leading to variation in foraging success across species. Our experiments further demonstrate a correlation between techniques and the intensity of visible percussive damage on the tools. Tools used with more precision and efficiency as demonstrated by macaques, show fewer use wear traces. This suggests that some percussive techniques may be less readily identified in the archaeological record.

Wild capuchin monkeys use stones and sticks to access underground food.

Primates employ different tools and techniques to overcome the challenges of obtaining underground food resources. Humans and chimpanzees are known to tackle this problem with stick tools and one population of capuchin monkeys habitually uses stone tools. Although early hominids could have used stones as digging tools, we know little about when and how these could be useful. Here, we report a second primate population observed using stone tools and the first capuchin monkey population to habitually use the 'stick-probing' technique for obtaining underground resources. The bearded capuchin monkeys (Sapajus libidinosus) from Ubajara National Park, Brazil, use 'hands-only' and 'stone-digging' techniques for extracting underground storage organs and trapdoor spiders. Males also use 'stick-probing' and 'stone-stick' techniques for capturing trapdoor spiders. Tool use does not increase success in obtaining these resources. Stone-digging is less frequent in this population than in the only other known population that uses this technique. Females use stones in a lower proportion of their digging episodes than males in both populations. Ecological and cultural factors potentially influence technique choice and sex differences within and between populations. This population has a different pattern of underground food exploration using tools. Comparing this population with others and exploring the ecological and cultural factors under which capuchin monkeys employ different tools and techniques will allow us to better understand the pressures that may have shaped the evolution of those behaviors in primates.

Ontogenetic changes in jaw leverage and skull shape in tufted and untufted capuchins.

The ontogeny of feeding is characterized by shifting functional demands concurrent with changes in craniofacial anatomy; relationships between these factors will look different in primates with disparate feeding behaviors during development. This study examines the ontogeny of skull morphology and jaw leverage in tufted (Sapajus) and untufted (Cebus) capuchin monkeys. Unlike Cebus, Sapajus have a mechanically challenging diet and behavioral observations of juvenile Sapajus suggest these foods are exploited early in development. Landmarks were placed on three-dimensional surface models of an ontogenetic series of Sapajus and Cebus skulls (n = 53) and used to generate shape data and jaw-leverage estimates across the tooth row for three jaw-closing muscles (temporalis, masseter, medial pterygoid) as well as a weighted combined estimate. Using geometric morphometric methods, we found that skull shape diverges early and shape is significantly different between Sapajus and Cebus throughout ontogeny. Additionally, jaw leverage varies with age and position on the tooth row and is greater in Sapajus compared to Cebus when calculated at the permanent dentition. We used two-block partial least squares analyses to identify covariance between skull shape and each of our jaw muscle leverage estimates. Sapajus, but not Cebus, has significant covariance between all leverage estimates at the anterior dentition. Our findings show that Sapajus and Cebus exhibit distinct craniofacial morphologies early in ontogeny and strong covariance between leverage estimates and craniofacial shape in Sapajus. These results are consistent with prior behavioral and comparative work suggesting these differences are a function of selection for exploiting mechanically challenging foods in Sapajus, and further emphasize that these differences appear quite early in ontogeny. This research builds on prior work that has highlighted the importance of understanding ontogeny for interpreting adult morphology.

A new approach to geostatistical synthesis of historical records reveals capuchin spatial responses to climate and demographic change.

Recent proliferation of GPS technology has transformed animal movement research. Yet, time-series data from this recent technology rarely span beyond a decade, constraining longitudinal research. Long-term field sites hold valuable historic animal location records, including hand-drawn maps and semantic descriptions. Here, we introduce a generalised workflow for converting such records into reliable location data to estimate home ranges, using 30 years of sleep-site data from 11 white-faced capuchin (Cebus imitator) groups in Costa Rica. Our findings illustrate that historic sleep locations can reliably recover home range size and geometry. We showcase the opportunity our approach presents to resolve open questions that can only be addressed with very long-term data, examining how home ranges are affected by climate cycles and demographic change. We urge researchers to translate historical records into usable movement data before this knowledge is lost; it is essential to understanding how animals are responding to our changing world.

An open-source MRI compatible frame for multimodal presurgical mapping in macaque and capuchin monkeys.

BACKGROUND: High-precision neurosurgical targeting in nonhuman primates (NHPs) often requires presurgical anatomical mapping with noninvasive neuroimaging techniques (MRI, CT, PET), allowing for translation of individual anatomical coordinates to surgical stereotaxic apparatus. Given the varied tissue contrasts that these imaging techniques produce, precise alignment of imaging-based coordinates to surgical apparatus can be cumbersome. MRI-compatible stereotaxis with radiopaque fiducial markers offer a straight-forward and reliable solution, but existing commercial options do not fit in conformal head coils that maximize imaging quality. NEW METHOD: We developed a compact MRI-compatible stereotaxis suitable for a variety of NHP species (Macaca mulatta, Macaca fascicularis, and Cebus apella) that allows multimodal alignment through technique-specific fiducial markers. COMPARISON WITH EXISTING METHODS: With the express purpose of compatibility with clinically available MRI, CT, and PET systems, the frame is no larger than a human head, while allowing for imaging NHPs in the supinated position. This design requires no marker implantation, special software, or additional knowledge other than the operation of a common large animal stereotaxis. RESULTS: We demonstrated the applicability of this 3D-printable apparatus across a diverse set of experiments requiring presurgical planning: 1) We demonstrate the accuracy of the fiducial system through a within-MRI cannula insertion and subcortical injection of a viral vector. 2) We also demonstrated accuracy of multimodal (MRI and CT) alignment and coordinate transfer to guide a surgical robot electrode implantation for deep-brain electrophysiology. CONCLUSIONS: The computer-aided design files and engineering drawings are publicly available, with the modular design allowing for low cost and manageable manufacturing.

Bearded capuchin monkeys as a model for Alzheimer's disease.

The absence of a natural animal model is one of the main challenges in Alzheimer's disease research. Despite the challenges of using nonhuman primates in studies, these animals can bridge mouse models and humans, as nonhuman primates are phylogenetically closer to humans and can spontaneously develop AD-type pathology. The capuchin monkey, a New World primate, has recently attracted attention due to its skill in creating and using instruments. We analyzed one capuchin brain using structural 7 T MRI and performed a neuropathological evaluation of three animals. Alzheimer-type pathology was found in the two of the capuchins. Widespread ß-amyloid pathology was observed, mainly in focal deposits with variable morphology and a high density of mature plaques. Notably, plaque-associated dystrophic neurites associated with disruption of axonal transport and early cytoskeletal alteration were frequently found. Unlike in other species of New World monkeys, cerebral arterial angiopathy was not the predominant form of ß-amyloid pathology. Additionally, abnormal aggregates of hyperphosphorylated tau, resembling neurofibrillary pathology, were observed in the temporal and frontal cortex. Astrocyte hypertrophy surrounding plaques was found, suggesting a neuroinflammatory response. These findings indicate that aged capuchin monkeys can spontaneously develop Alzheimer-type pathology, indicating that they may be an advantageous animal model for research in Alzheimer's disease.

The Joint Simon task is not joint for capuchin monkeys.

Human cooperation can be facilitated by the ability to create a mental representation of one's own actions, as well as the actions of a partner, known as action co-representation. Even though other species also cooperate extensively, it is still unclear whether they have similar capacities. The Joint Simon task is a two-player task developed to investigate this action co-representation. We tested brown capuchin monkeys (Sapajus [Cebus] apella), a highly cooperative species, on a computerized Joint Simon task and found that, in line with previous research, the capuchins' performance was compatible with co-representation. However, a deeper exploration of the monkeys' responses showed that they, and potentially monkeys in previous studies, did not understand the control conditions, which precludes the interpretation of the results as a social phenomenon. Indeed, further testing to investigate alternative explanations demonstrated that our results were due to low-level cues, rather than action co-representation. This suggests that the Joint Simon task, at least in its current form, cannot determine whether non-human species co-represent their partner's role in joint tasks.

Mother of all bonds: Influences on spatial association across the lifespan in capuchins.

In humans, being more socially integrated is associated with better physical and mental health and/or with lower mortality. This link between sociality and health may have ancient roots: sociality also predicts survival or reproduction in other mammals, such as rats, dolphins, and non-human primates. A key question, therefore, is which factors influence the degree of sociality over the life course. Longitudinal data can provide valuable insight into how environmental variability drives individual differences in sociality and associated outcomes. The first year of life-when long-lived mammals are the most reliant on others for nourishment and protection-is likely to play an important role in how individuals learn to integrate into groups. Using behavioral, demographic, and pedigree information on 376 wild capuchin monkeys (Cebus imitator) across 20 years, we address how changes in group composition influence spatial association. We further try to determine the extent to which early maternal social environments have downstream effects on sociality across the juvenile and (sub)adult stages. We find a positive effect of early maternal spatial association, where female infants whose mothers spent more time around others also later spent more time around others as juveniles and subadults. Our results also highlight the importance of kin availability and other aspects of group composition (e.g., group size) in dynamically influencing spatial association across developmental stages. We bring attention to the importance of-and difficulty in-determining the social versus genetic influences that parents have on offspring phenotypes. RESEARCH HIGHLIGHTS: Having more maternal kin (mother and siblings) is associated with spending more time near others across developmental stages in both male and female capuchins. Having more offspring as a subadult or adult female is additionally associated with spending more time near others. A mother's average sociality (time near others) is predictive of how social her daughters (but not sons) become as juveniles and subadults (a between-mother effect). Additional variation within sibling sets in this same maternal phenotype is not predictive of how social they become later relative to each other (no within-mother effect).

Assessing morphological preservation of gastrointestinal parasites from fecal samples of wild capuchin monkeys (Cebus imitator) stored in ethanol versus formalin.

The copromicroscopic identification of gastrointestinal parasites is a common, cost-effective method vital to understanding host-parasite interactions. However, its efficacy depends on effective preservation of the samples. In this study, we compare the preservation of ethanol and formalin preserved gastrointestinal parasites collected from a wild population of Costa Rican capuchin monkeys (Cebus imitator). Fecal samples were collected, halved, and stored in either 10% formalin or 96% ethanol at ambient temperature, then microscopically screened for the presence of parasites. Parasites were morphologically identified and rated based on their preservation using a newly developed rubric. We identified more parasitic morphotypes in formalin-preserved samples but found no difference in the number of parasites per fecal gram (PFG) between mediums. There was no difference in the PFG of two most prevalent parasite morphotypes, Filariopsis barretoi larvae and Strongyle-type eggs, and while Filariopsis larvae were better preserved in formalin, strongyle eggs showed no preservation difference between mediums. Our results support the suitability of both ethanol and formalin for morphological parasite identification in samples stored over 1 year, describe the morphological changes and challenges associated with parasite degradation, and highlight the potential for future studies to use both morphological and molecular methods in non-invasively collected samples.

Available and unavailable decoys in capuchin monkeys (Sapajus spp.) decision-making.

Decision-making has been observed to be systematically affected by decoys, i.e., options that should be irrelevant, either because unavailable or because manifestly inferior to other alternatives, and yet shift preferences towards their target. Decoy effects have been extensively studied both in humans and in several other species; however, evidence in non-human primates remains scant and inconclusive. To address this gap, this study investigates how choices in capuchin monkeys (Sapajus spp.) are affected by different types of decoys: asymmetrically dominated decoys, i.e., available and unavailable options that are inferior to only one of the other alternatives, and phantom decoys, i.e., unavailable options that are superior to another available alternative. After controlling for the subjective strength of initial preferences and the distance of each decoy from its target in attribute space, results demonstrate a systematic shift in capuchins' preference towards the target of both asymmetrically dominated decoys (whether they are available or not) and phantom decoys, regardless of what options is being targeted by such decoys. This provides the most comprehensive evidence to date of decoy effects in non-human primates, with important theoretical and methodological implications for future comparative studies on context effects in decision-making.

How can I find what I want? Can children, chimpanzees and capuchin monkeys form abstract representations to guide their behavior in a sampling task?

concepts are a powerful tool for making wide-ranging predictions in new situations based on little experience. Whereas looking-time studies suggest an early emergence of this ability in human infancy, other paradigms like the relational match to sample task often fail to detect abstract concepts until late preschool years. Similarly, non-human animals show difficulties and often succeed only after long training regimes. Given the considerable influence of slight task modifications, the conclusiveness of these findings for the development and phylogenetic distribution of abstract reasoning is debated. Here, we tested the abilities of 3 to 5-year-old children, chimpanzees, and capuchin monkeys in a unified and more ecologically valid task design based on the concept of "overhypotheses" (Goodman, 1955). Participants sampled high- and low-valued items from containers that either each offered items of uniform value or a mix of high- and low-valued items. In a test situation, participants should switch away earlier from a container offering low-valued items when they learned that, in general, items within a container are of the same type, but should stay longer if they formed the overhypothesis that containers bear a mix of types. We compared each species' performance to the predictions of a probabilistic hierarchical Bayesian model forming overhypotheses at a first and second level of abstraction, adapted to each species' reward preferences. Children and, to a more limited extent, chimpanzees demonstrated their sensitivity to abstract patterns in the evidence. In contrast, capuchin monkeys did not exhibit conclusive evidence for the ability of abstract knowledge formation.

Male-biased stone tool use by wild white-faced capuchins (Cebus capucinus imitator).

Tool-using primates often show sex differences in both the frequency and efficiency of tool use. In species with sex-biased dispersal, such within-group variation likely shapes patterns of cultural transmission of tool-use traditions between groups. On the Panamanian islands of Jicarón and Coiba, a population of white-faced capuchins (Cebus capucinus imitator)-some of which engage in habitual stone tool use-provide an opportunity to test hypotheses about why such sex-biases arise. On Jicarón, we have only observed males engaging in stone tool use, whereas on Coiba, both sexes are known to use tools. Using 5 years of camera trap data, we provide evidence that this variation likely reflects a sex difference in tool use rather than a sampling artifact, and then test hypotheses about the factors driving this pattern. Differences in physical ability or risk-aversion, and competition over access to anvils do not account for the sex-differences in tool-use we observe. Our data show that adult females are physically capable of stone tool use: adult females on Coiba and juveniles on Jicarón smaller than adult females regularly engage in tool use. Females also have ample opportunity to use tools: the sexes are equally terrestrial, and competition over anvils is low. Finally, females rarely scrounge on left-over food items either during or after tool-using events, suggesting they are not being provisioned by males. Although it remains unclear why adult white-faced capuchin females on Jicarón do not use stone-tools, our results illustrate that such sex biases in socially learned behaviors can arise even in the absence of obvious physical, environmental, and social constraints. This suggests that a much more nuanced understanding of the differences in social structure, diet, and dispersal patterns are needed to explain why sex-biases in tool use arise in some populations but not in others.

Transcriptomic and metabolomic analysis unveils a negative effect of glutathione metabolism on laccase activity in Cerrena unicolor 87613.

The white rot fungus Cerrena unicolor 87613 has been previously shown to be a promising resource in laccase production, an enzyme with significant biotechnological applications. Conventional methods face technical challenges in improving laccase activity. Attempts are still being made to develop novel approaches for further enhancing laccase activity. This study aimed to understand the regulation of laccase activity in C. unicolor 87613 for a better exploration of the novel approach. Transcriptomic and metabolomic analyses were performed to identify key genes and metabolites involved in extracellular laccase activity. The findings indicated a strong correlation between the glutathione metabolism pathway and laccase activity. Subsequently, experimental verifications were conducted by manipulating the pathway using chemical approaches. The additive reduced glutathione (GSH) dose-dependently repressed laccase activity, while the GSH inhibitors (APR-246) and reactive oxygen species (ROS) inducer (H2O2) enhanced laccase activity. Changes in GSH levels could determine the intracellular redox homeostasis in interaction with ROS and partially affect the expression level of laccase genes in C. unicolor 87613 in turn. In addition, GSH synthetase was found to mediate GSH abundance in a feedback loop. This study suggests that laccase activity is negatively influenced by GSH metabolism and provides a theoretical basis for a novel strategy to enhance laccase activity by reprogramming glutathione metabolism at a specific cultivation stage.IMPORTANCEThe production of laccase activity is limited by various conventional approaches, such as heterologous expression, strain screening, and optimization of incubation conditions. There is an urgent need for a new strategy to meet industrial requirements more effectively. In this study, we conducted a comprehensive analysis of the transcriptome and metabolome of Cerrena unicolor 87613. For the first time, we discovered a negative role played by reduced glutathione (GSH) and its metabolic pathway in influencing extracellular laccase activity. Furthermore, we identified a feedback loop involving GSH, GSH synthetase gene, and GSH synthetase within this metabolic pathway. These deductions were confirmed through experimental investigations. These findings not only advanced our understanding of laccase activity regulation in its natural producer but also provide a theoretical foundation for a strategy to enhance laccase activity by reprogramming glutathione metabolism at a specific cultivation stage.

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.

Taphonomy of harpy eagle predation on primates and other mammals.

The goal of this study is to provide a taphonomic analysis of bone fragments found in harpy eagle nests in the Brazilian Amazonia, utilizing the largest sample of prey remains collected to date. Harpy eagle kill samples were collected from nine nests, between June 2016 and December 2020 in Mato Grosso, Brazil. We identified the specimens, calculated the number of identified specimens (NISP) and minimum number of individuals (MNI). These metrics were used to estimate bone survivability and fragmentation. A total of 1661 specimens (NISP) were collected, representing a minimum number of 234 individuals (MNI). We identified at least nine species of primates, which represent 63.8% of the individuals in the kill sample. Harpy eagles preyed mostly on the medium-sized capuchin and bearded saki monkeys (28.2% of the MNI), and two-toed sloths (17.7% of the MNI). The large woolly monkeys also represented a significant portion of the sample (11.5% of the MNI). Three distinct patterns of bone survivability were found, one characterizing two-toed sloths, another characterizing medium-sized monkeys, and a third typical of woolly monkeys. We conclude that harpy eagle predation leaves an identifiable signature on the prey with a bone survivability pattern specific to each taxon. The intertaxon variations observed in the taphonomic signatures of harpy eagle kills should be taken into account when evaluating the potential influence of these raptors as accumulators of bone material in both paleontological and neontological assemblages.

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.

Disputes over provisioned resources are no more intense between groups than within groups in free-ranging Sapajus libidinosus.

Socioecological models predict that disputes between primate groups will be more intense than those within groups, given that the systematic loss of contests over a given resource will restrict the access of all of the members of that group to that resource. Higher levels of aggression are also expected for provisioned resources that have a more lucrative cost:benefit ratio. The levels of aggression in and between two free-ranging tufted capuchin monkey (Sapajus libidinosus) groups in the context of daily provisioning with bananas were evaluated. The aim of a complementary analysis was to identify possible predictors of the frequency of disputes at the site of the provisioned resource. The disputes were recorded using all-events sampling, while the social behaviour of the study groups was recorded by instantaneous scan sampling. The data were analysed using t-test, Mann-Whitney's U, and generalised linear modelling. Between-group disputes were no more intense than within-group events, and did not involve more individuals, or more adult females. The frequency of disputes increased as the number of individuals eating bananas increased. No evidence was found that disputes between groups were any more intense than those within groups. Dominance patterns may have affected these findings, by mediating intergroup disputes. An increase in the number of competitors affected the frequency of disputes at the site of the provisioned resource.