Diversity of nutcracking tool sites used bySapajus libidinosusin BrazilianCerrado

A new addition to the toolbox: stone tool use in blonde capuchin monkeys (Sapajus flavius)

The use of tools played a central role in human culture and evolution. Early studies with apes demonstrated the tool use; however, currently the works have focused on Platyrrhine, particularly capuchin monkeys. Blonde capuchin monkeys, Sapajus flavius, have been observed using sticks to fish for termites in the Atlantic Forest, where this species has been extensively studied. In this study, we presented the first evidence of stone tool use by the blonde capuchin monkeys, as well as the dimensions and weight of these tools. We gathered data from three areas of Caatinga dry forest where we discovered this new tool use among the species. The mean weight of the hammers was 475.7 g (± 142 SD). The mean height of the anvils was 48.3 cm (± 18.7 SD), while the mean surface area of the anvils was 1.2 m2 (± 0.4 SD). We identified fruits and/or nuts from three plant species-Prunus dulces, Cnidoscolus quercifolius, and Syagrus coronate-near the anvils at the study sites. Additionally, we passively observed six instances of stone tool use by blonde capuchin monkeys. Their use of stones to crack encased foods mirrored behaviors previously reported in Sapajus libidinosus, a species well known for using stone tools to exploit hard nuts. Our findings place blonde capuchin monkeys among the list of primates that utilize stones as tools, highlighting the species' adaptability in exploiting resources within the Caatinga. Long-term studies are essentials to comprehend the use pattern of stone tools (across both general and seasonal perspectives) and the influence of variables, such as fruit hardness, distance to watercourses, and fruit availability on the use of this technology by this primate.

Nut-cracking success and efficiency in two wild capuchin monkey populations

Capuchins can employ several strategies to deal with environmental challenges, such as using stone tools to access encapsulated resources. Nut-cracking is customary in several capuchin populations and can be affected by ecological and cultural factors; however, data on success and efficiency are only known for two wild populations. In this work, using camera traps, we assessed palm nut-cracking success and efficiency in two newly studied wild bearded capuchin populations (Sapajus libidinosus) and compared them with other sites. We tested the hypothesis that the overall success and efficiency of nut-cracking would be similar between sites when processing similar resources, finding partial support for it. Although using hammerstones of different sizes, capuchins had a similar success frequency. However, efficiency (number of strikes to crack a nut) was different, with one population being more efficient. We also tested whether success and efficiency varied between sexes in adults. We predict adult males would be more successful and efficient when cracking hard nuts. We found no differences between the sexes in one site but found sex differences in the other, although also for the low-resistant nut, which was unexpected. Our data add to the knowledge of capuchin nut-cracking behaviour flexibility, variance and potential cultural traits.

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.

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.

Stone tools differences across three capuchin monkey populations: food's physical properties, ecology, and culture

Robust capuchin monkeys (Sapajus) are known for processing mechanically challenging foods, having morphological adaptations to do so. However, several populations go beyond body limitations by using stone tools to expand their food range. Those populations use stones in a variety of ways, goals, and with different frequencies. Stone tool size correlates with the food's resistance within some populations. However, we have no detailed comparisons to identify if this correlation is the same across populations. This study described and compared stone raw material availability, food's physical properties (hardness and elasticity), and stone tool weight in three populations of bearded capuchin monkeys (Sapajus libidinosus), including a newly described site (Chapada dos Veadeiros National Park, CVNP). The differences we observed regarding stone tool weight selection among sites were not correlated to the food's physical properties we analyzed. Lithic resource availability could partly explain some differences in the stone tools used. However, the tool weight differences are larger than the raw material variance across sites, meaning some distinctions are possible behavioral traditions, such as the same fruit (Hymenaea) being processed with bigger than needed tools in CVNP than in the other two sites. Capuchin monkey behavioral variability in stone tool use can be caused by several interacting factors, from ecological to cultural.

Stone tools improve diet quality in wild monkeys

Tool use is a fundamental feature of human evolution. Stone tools are in the archaeological record from 3.4 Ma, even before Homo,¹ and the use of stone tools probably predated the split between hominins and panins.² Using tools (hereafter, tooling cf Fragaszy and Mangalam³) is hypothesized to have improved hominins' foraging efficiency or access to high-quality foods.^4-7 This hypothesis is supported if feeding with tools positively contributes to diet quality in extant non-human primates or if foraging efficiency is increased by tooling. However, the contribution of tooling to non-human primates' foraging success has never been investigated through a direct analysis of nutritional ecology.^8,9 We used multi-dimensional nutritional geometry to analyze energy and macronutrients (nonstructural carbohydrates, lipids, and protein) in the diets of wild capuchin monkeys (Sapajus libidinous) that routinely crack palm nuts with stone hammers.^10,11 We show that eating nuts obtained through tooling helps monkeys to achieve more consistent dietary intakes. Tooling increased the net energy gain by 50% and decreased the proportion of fiber ingested by 7%. Tooling also increased the daily non-protein energy intake. By contrast, protein intake remained constant across foraging days, suggesting a pattern of macronutrient regulation called protein prioritization, which is also found in contemporary humans.^8,9 In addition, tooling reduced dispersion in the ratio of protein to non-protein energy, suggesting a role in macronutrient balancing. Our findings suggest that tooling prior to tool making could have substantially increased the nutritional security of ancestral hominins, sowing the seeds for cultural development.^5,7 VIDEO ABSTRACT.

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.

Optional tool use: The case of wild bearded capuchins (Sapajus libidinosus) cracking cashew nuts by biting or by using percussors

Tool use in humans can be optional, that is, the same person can use different tools or no tool to achieve a given goal. Strategies to reach the same goal may differ across individuals and cultures and at the intra-individual level. This is the first experimental study at the intra-individual level on the optional use of a tool in wild nonhuman primates. We investigated optional tool use by wild bearded capuchins (Sapajus libidinosus) of Fazenda Boa Vista (FBV; Piauí, Brazil). These monkeys habitually succeed in cracking open the mesocarp of dry cashew nuts (Anacardium spp.) by pounding them with stones and/or by biting. We assessed whether availability of a stone and resistance of the nut affected capuchins' choice to pound or to bite the nuts and their rates of success. Sixteen capuchins (1-16 years) received small and large dry cashew nuts by an anvil together with a stone (Stone condition) or without a stone (No-Stone condition). In the Stone conditions, subjects used it to crack the nut in 89.1% (large nuts) and 90.1% (small nut) of the trials. Nut size significantly affected the number of strikes used to open it. Availability of the stone significantly increased the average percent of success. In the No-Stone conditions, monkeys searched for and used other percussors to crack the nuts in 54% of trials. In all conditions, age affects percentage of success and number of strikes to reach success. We argue that exclusive use of stones in other sites may be due to the higher abundance of stones at these sites compared with FBV. Since capuchins opened cashews with a tool 1-2 years earlier than they succeed at cracking more resistant palm nuts, we suggest that success at opening cashew nuts with percussors may support the monkeys' persistent efforts to crack palm nuts.

Habitual stone-tool-aided extractive foraging in white-faced capuchins, Cebus capucinus

Habitual reliance on tool use is a marked behavioural difference between wild robust (genus Sapajus) and gracile (genus Cebus) capuchin monkeys. Despite being well studied and having a rich repertoire of social and extractive foraging traditions, Cebus sp. rarely use tools and have never been observed using stone tools. By contrast, habitual tool use by Sapajus is widespread. We review theory and discuss factors which might explain these differences in patterns of tool use between Cebus and Sapajus. We then report the first case of habitual stone tool use in a gracile capuchin: a population of white-faced capuchins (Cebus capucinus imitator) in Coiba National Park, Panama who habitually rely on hammerstone and anvil tool use to access structurally protected food items in coastal areas including Terminalia catappa seeds, hermit crabs, marine snails, terrestrial crabs and other items. This behaviour has persisted on one island in Coiba National Park since at least 2004. From 1 year of camera trapping, we found that stone tool use is strongly male-biased. Of the 205 camera trap days where tool use was recorded, adult females were never observed to use stone tools, although they were frequently recorded at the sites and engaged in scrounging behaviour. Stone tool use occurs year-round in this population; over half of all identifiable individuals were observed participating. At the most active tool use site, 83.2% of days where capuchins were sighted corresponded with tool use. Capuchins inhabiting the Coiba archipelago are highly terrestrial, under decreased predation pressure and potentially experience resource limitation compared to mainland populations-three conditions considered important for the evolution of stone tool use. White-faced capuchin tool use in Coiba National Park thus offers unique opportunities to explore the ecological drivers and evolutionary underpinnings of stone tool use in a comparative within- and between-species context.

Stone tool use by wild capuchin monkeys (Sapajus libidinosus) at Serra das Confusões National Park, Brazil

Capuchin monkeys (Sapajus spp.) are proficient tool users, and the use of stone tools occurs in several populations, mostly to crack open encased foods. Two well-studied Brazilian populations of Sapajus libidinosus inhabit Fazenda Boa Vista and Serra da Capivara National Park and present different behavioral sets regarding tool use. Serra das Confusões National Park (SCoNP) lies between those sites, but little is known about the capuchin monkey population that lives there. To begin unraveling the capuchin behavior in this area, we conducted a brief survey for tool use sites. We found indirect evidence that capuchin monkeys at SCoNP use stone hammers to crack open at least four species of seeds and fruits. Plant reproductive parts there are processed with stone tools in a similar pattern to the other sites. Further study is needed to directly observe tool use by capuchin monkeys at SCoNP, verify the occurrence of other possible types of tool use in this population, and thus fully compare their tool use repertoire to that of other populations.

The mammalian faunas endemic to the Cerrado and the Caatinga

We undertook a comprehensive, critical review of literature concerning the distribution, conservation status, and taxonomy of species of mammals endemic to the Cerrado and the Caatinga, the two largest biomes of the South American Dry-Diagonal. We present species accounts and lists of species, which we built with criteria that, in our opinion, yielded results with increased scientific rigor relative to previously published lists - e.g., excluding nominal taxa whose statuses as species have been claimed only on the basis of unpublished data, incomplete taxonomic work, or weak evidence. For various taxa, we provided arguments regarding species distributions, conservation and taxonomic statuses previously lacking in the literature. Two major findings are worth highlighting. First, we unveil the existence of a group of species endemic to both the Cerrado and the Caatinga (i.e., present in both biomes and absent in all other biomes). From the biogeographic point of view, this group, herein referred to as Caatinga-Cerrado endemics, deserves attention as a unit - just as in case of the Caatinga-only and the Cerrado-only endemics. We present preliminary hypotheses on the origin of these three endemic faunas (Cerrado-only, Caatinga-only, and Caatinga-Cerrado endemics). Secondly, we discovered that a substantial portion of the endemic mammalian faunas of the Caatinga and the Cerrado faces risks of extinction that are unrecognized in the highly influential Red List of Threatened Species published by the International Union for Conservation of Nature (IUCN). "Data deficient" is a category that misrepresents the real risks of extinction of these species considering that (a) some of these species are known only from a handful of specimens collected in a single or a few localities long ago; (b) the Cerrado and the Caatinga have been sufficiently sampled to guarantee collection of additional specimens of these species if they were abundant; (c) natural habitats of the Cerrado and the Caatinga have been substantially altered or lost in recent decades. Failures either in the design of the IUCN criteria or in their application to assign categories of extinction risks represent an additional important threat to these endemic faunas because their real risks of extinctions become hidden. It is imperative to correct this situation, particularly considering that these species are associated to habitats that are experiencing fast transformation into areas for agriculture, at an unbearable cost for biodiversity.

The manifold use of pounding stone tools by wild capuchin monkeys of Serra da Capivara National Park, Brazil

The use of pounding stone tools (PSTs) is a customary behaviour in several wild populations of capuchin monkeys; most of these monkeys use PSTs primarily to open hard palm nuts. Here, we describe the use of PSTs in two not previously studied groups of capuchin monkeys (Sapajus libidinosus) in Serra da Capivara National Park (SCNP), northeastern Brazil, and compare them to other groups and populations. Capuchins from SCNP are one of the only known population that habitually use PSTs for several purposes other than nut processing, including cracking seeds and fruits, breaking and/or enlarging holes in tree trunks or rocks, and pulverizing pebbles. Moreover, they use PSTs sequentially with probe stick tools to access hidden prey. The average size of PSTs was larger than the average locally available stones, suggesting active choice. The two groups exhibited more diversity in the use of PSTs than any other known population to date.

Percussive tool use by Taï Western chimpanzees and Fazenda Boa Vista bearded capuchin monkeys: a comparison

Percussive tool use holds special interest for scientists concerned with human origins. We summarize the findings from two field sites, Taï and Fazenda Boa Vista, where percussive tool use by chimpanzees and bearded capuchins, respectively, has been extensively investigated. We describe the ecological settings in which nut-cracking occurs and focus on four aspects of nut-cracking that have important cognitive implications, namely selection of tools, tool transport, tool modification and modulation of actions to reach the goal of cracking the nut. We comment on similarities and differences in behaviour and consider whether the observed differences reflect ecological, morphological, social and/or cognitive factors. Both species are sensitive to physical properties of tools, adjust their selection of hammers conditionally to the resistance of the nuts and to transport distance, and modulate the energy of their strikes under some conditions. However, chimpanzees transport hammers more frequently and for longer distances, take into account a higher number of combinations of variables and occasionally intentionally modify tools. A parsimonious interpretation of our findings is that morphological, ecological and social factors account for the observed differences. Confirmation of plausible cognitive differences in nut-cracking requires data not yet available.