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.

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.

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.

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.

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.

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.

Chromatic discrimination in fixed saturation levels from tufted capuchin monkeys with different color vision genotypes.

Recent research has proposed new approaches to investigate color vision in Old World Monkeys by measuring suprathreshold chromatic discrimination. In this study, we aimed to extend this approach to New World Monkeys with different color vision genotypes by examining their performance in chromatic discrimination tasks along different fixed chromatic saturation axes. Four tufted capuchin monkeys were included in the study, and their color vision genotypes were one classical protanope, one classical deuteranope, one non-classical protanope, and a normal trichromat. During the experiments, the monkeys were required to perform a chromatic discrimination task using pseudoisochromatic stimuli with varying target saturations of 0.06, 0.04, 0.03, and 0.02 u'v' units. The number of errors made by the monkeys along different chromatic axes was recorded, and their performance was quantified using the binomial probability of their hits during the tests. Our results showed that dichromatic monkeys made more errors near the color confusion lines associated with their specific color vision genotypes, while the trichromatic monkey did not demonstrate any systematic errors. At high chromatic saturation, the trichromatic monkey had significant hits in the chromatic axes around the 180° chromatic axis, whereas the dichromatic monkeys had errors in colors around the color confusion lines. At lower saturation, the performance of the dichromatic monkeys became more challenging to differentiate among the three types, but it was still distinct from that of the trichromatic monkey. In conclusion, our findings suggest that high saturation conditions can be used to identify the color vision dichromatic phenotype of capuchin monkeys, while low chromatic saturation conditions enable the distinction between trichromats and dichromats. These results extend the understanding of color vision in New World Monkeys and highlight the usefulness of suprathreshold chromatic discrimination measures in exploring color vision in non-human primates.

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.

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.

Evidence that highly canalized fetal traits are sensitive to intergenerational effects of maternal developmental nutrition.

OBJECTIVES: Maternal experiences before pregnancy predict birth outcomes, a key indicator of health trajectories, but the timing and pathways for these effects are poorly understood. Here we test the hypothesis that maternal pre-adult growth patterns predict pregnancy glucose and offspring fetal growth in Cebu, Philippines. METHODS: Using multiple regression and path analysis, gestational age-adjusted birthweight and variables reflecting infancy, childhood, and post-childhood/adolescent weight gain (conditional weights) were used to predict pregnancy HbA1c and offspring birth outcomes among participants in the Cebu Longitudinal Health and Nutrition Survey. RESULTS: Maternal early/mid-childhood weight gain predicted birth weight, length, and head circumference in female offspring. Late-childhood/adolescent weight gain predicted birth length, birth weight, skinfold thickness, and head circumference in female offspring, and head circumference in male offspring. Pregnancy HbA1c did not mediate relationships between maternal growth and birth size parameters. DISCUSSION: In Cebu, maternal growth patterns throughout infancy, childhood, and adolescence predict fetal growth via a pathway independent of circulating glucose, with stronger impacts on female than male offspring, consistent with a role of developmental nutrition on offspring fetal growth. Notably, the strength of relationships followed a pattern opposite to what occurs in response to acute pregnancy stress, with strongest effects on head circumference and birth length and weakest on skinfolds. We speculate that developmental sensitivities are reversed for stable, long-term nutritional cues that reflect average local environments. These findings are relevant to public health and life-history theory as further evidence of developmental influences on health and resource allocation across the life course.

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.

Diagnostic efficacy and safety of radial probe endobronchial ultrasound-guided transbronchial needle aspiration for adjacent lesions in segmental or subsegmental bronchi: a single-center retrospective study.

BACKGROUND: Peripheral lung lesions can be sampled using various techniques, including computer tomography-guided transthoracic needle aspiration, electromagnetic navigation bronchoscopy, virtual navigation bronchoscopy, and radial probe endobronchial ultrasound transbronchial lung biopsy. Mediastinal lesions can be sampled using techniques like convex probe endobronchial ultrasound-guided transbronchial needle aspiration (CEBUS-TBNA) and endoscopic ultrasound-fine-needle aspiration. However, effective, safe techniques for lesions adjacent to the segmental or subsegmental bronchi are lacking. Herein, we retrospectively evaluated the diagnostic yield and safety of radial probe endobronchial ultrasound-assisted transbronchial needle aspiration (REBUS-TBNA) for lesions adjacent to the segmental bronchi, and explored the factors related to diagnostic yield. METHODS: We retrospectively analyzed the diagnostic yield and safety of REBUS-TBNA cases performed in our department from January 2019 to December 2022. Observation group patients had undergone REBUS-TBNA for lesions adjacent to the segmental bronchi; control group patients had undergone CEBUS-TBNA for mediastinal or hilar lesions. Patient characteristics and lesion sizes, diagnostic yield, adverse events, and relations between diagnostic yield and clinical characteristics were analyzed. RESULTS: There were not statistically significant between-group differences in sex, age, diagnostic yield, or rate of adverse events. The observation group (n = 25; 17 male, 8 female) had a mean age of 64.76 ± 10.75 years. The average lesion size was 4.66 ± 1.07 cm, and lesions were predominantly in the upper lobes (80%). REBUS-TBNA diagnostic yield was 84%, with no adverse events reported. Diagnostic yield was not associated with lesion size or extent of bronchial stenosis; however, it was positively correlated with number of punctures. Patients with > 3 punctures had a significantly higher diagnostic yield than those with ≤ 3 punctures. CONCLUSIONS: REBUS-TBNA is a safe, effective diagnostic technique, particularly for lesions adjacent to the segmental or subsegmental bronchi of the upper lobe. Performing more than three punctures during the procedure improves the diagnostic yield. Larger-scale studies are warranted to confirm these results, and to further explore the clinical value of REBUS-TBNA.

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.

Climate change effects on the distribution of yellow-breasted capuchin monkey (Sapajus xanthosternos (Wied-Neuwied, 1826)).

The magnitude of recent climatic changes has no historical precedent and impacts biodiversity. Climatic changes may displace suitable habitats (areas with suitable climates), leading to global biodiversity decline. Primates are among the most affected groups. Most primates depend on forests and contribute to their maintenance. We evaluated the potential effects of climatic change on the distribution of Sapajus xanthosternos, a critically endangered primate whose geographical range encompasses three Brazilian biomes. We evaluated changes between baseline (1970-2000) and future (2081-2100) climates using multivariate analysis. Then, we compared current and future (2100) climatic suitability projections for the species. The climatic changes predicted throughout the S. xanthosternos range differed mostly longitudinally, with higher temperature increases in the west and higher precipitation reductions in the east. Climatic suitability for S. xanthosternos is predicted to decline in the future. Areas with highest current climatic suitability occur as a narrow strip in the eastern part of the geographic range throughout the latitudinal range. In the future, areas with highest values are projected to be located as an even narrower strip in the eastern part of the geographical range. A small portion of forest remnants larger than 150 ha located in the east has larger current and future suitability values. At this large scale, the spatial heterogeneity of the climate effects reinforce the importance of maintenance of current populations in different areas of the range. The possibility that phenotypic plasticity helps primates cope with reduced climatic suitability may be mediated by habitat availability, quality, and connectivity.

DNA barcoding of marine teleost fishes (Teleostei) in Cebu, the Philippines, a biodiversity hotspot of the coral triangle.

A morphology-based barcoding library of market teleost fishes (Teleostei) in Cebu is built based on cytochrome c oxidase subunit I (COI) sequences and voucher specimens which aimed to establish a reliable reference of frequently traded fishes in the province, a biodiversity hotspot at the center of the Philippine archipelago. A total of 1721 specimens were collected from 18 fish markets and landing sites around the province, in which 538 specimens were sequenced belonging to 393 species from 229 genera, 86 families, and 37 orders. Most speciose families are coral reef or reef-related shallow-water species. Twelve species from 11 families are newly recorded in the Philippine waters, among which 7 species are deep-sea inhabitants, while 3 species have expanded their distribution range. Only 20 taxa could not be identified to the species level due to the difficulty in morphological examinations, absence of matched reference sequences in online databases, and/or problematic species awaiting further studies. This first comprehensive DNA barcoding survey of Cebu fishes can facilitate further taxonomic research as well as the conservation and management of fisheries in the Philippines.

Primate richness and abundance is driven by both forest structure and conservation scenario in Costa Rica.

Variation in tropical forest management directly affects biodiversity and provisioning of ecosystem services on a global scale, thus it is necessary to compare forests under different conservation approaches such as protected areas, payments for ecosystem services programs (PES), and ecotourism, as well as forests lacking any formal conservation plan. To examine the effectiveness of specific conservation approaches, we examined differences in forest structure and tree recruitment, including canopy cover; canopy height; seedling, sapling, and adult tree density; and average and total diameter at breast height (DBH) across 78 plots in 18 forests across Costa Rica representing protected areas, private forests utilizing PES and/or ecotourism, and private forests not utilizing these economic incentives. The effectiveness of conservation approaches in providing suitable primate habitat was assessed by conducting broad primate census surveys across a subset of eight forests to determine species richness and group encounter rate of three primate species: mantled howler monkey (Alouatta palliata), Central American spider monkey (Ateles geoffroyi), and the white-faced capuchin monkey (Cebus imitator). Only canopy height was significantly different across the three approaches, with protected areas conserving the tallest and likely oldest forests. Canopy height was also significantly associated with the group encounter rate for both mantled howler and spider monkeys, but not for capuchins. Total group encounter rate for all three monkey species combined was higher in incentivized forests than in protected areas, with capuchin and howler monkey group encounter rates driving the trend. Group encounter rate for spider monkeys was higher in protected areas than in incentivized forests. Incentivized conservation (PES and ecotourism) and protected areas are paragons of land management practices that can lead to variation in forest structure across a landscape, which not only protect primate communities, but support the dietary ecologies of sympatric primate species.

Do they know or just do it? Investigating implicit and explicit sequence learning by capuchin monkeys, human adults and children.

In humans, it is now established that sequential regularities can be learned implicitly (i.e. without acquiring conscious knowledge) or explicitly (with acquisition of conscious knowledge). Is this dual-processing capability also the case for non-human primates? In this study, we designed a non-verbal task to probe implicit and explicit sequence learning in capuchin monkeys (Sapajus sp., n = 12), human adults (n = 12), and children from 5 to 10 years old (n = 64). After learning spatial sequences on a touchscreen, participants' conscious access to the sequences was probed with a forced choice sequence completion test. All performed above chance level in this test, without being instructed or trained to do so. However, only human adults who reported the presence of regularities performed at ceiling level. We suggest future directions that could build on our findings to disentangle implicit and explicit learning in monkeys and children.

State-dependent risky choices in primates: Variation in energy budget does not affect tufted capuchin monkeys' (Sapajus spp.) risky choices.

Economic models predict that rational decision makers' choices between a constant, "safe" option and a variable, "risky" option leading, on average, to the same payoff, should be random. However, a wealth of research has revealed that, when faced with risky decisions, both human and nonhuman animals deviate from economic rationality. According to the risk-sensitivity theory, individuals should prefer a safe option when they are in a positive energy state and a risky option when they are in a negative energy state. The abundance/risk hypothesis proposes that individuals should prefer risky options when diet quality exceeds their nutritional requirements. We tested how energy budget affects decision making under risk by presenting 22 capuchins belonging to two colonies (IT: N = 12, US: N = 10) with a risky choice task. Capuchins had to choose between a constant option (always four food items) and a variable option (one or seven food items with a 50% probability) in two conditions. In the Low-energy condition capuchins were tested before their main meal, whereas in the High-energy condition they were tested following a high-caloric meal. In neither colony did we find a significant difference between conditions, suggesting that the energy budget did not affect risk preferences. However, we found differences between colonies in their general response to risky choices: US capuchins were more risk-prone after selecting a safe option than a risky option and after selecting a bad (one food item) than a good (seven food items) risky option, whereas this did not hold true in IT capuchins. Furthermore, in the IT colony, males were more risk-prone under the High-energy condition compared to the Low-energy condition. Subtle differences in individual characteristics, management conditions, or stochastic founder effects may be implied, with relevant consequences for the outcomes of research on risky decision-making across laboratories.