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Our aim is general: we want to illustrate how much can be gleaned from mechanical measurement in the field. We ask how mechanics may constrain foraging and feeding on both plants and animals, and how various aspects of mechanical behavior could affect the feeding choices that primates make. Here, we present novel methods for the measurement of the material properties and also the employment of tried and tested methods in novel settings. This review demonstrates how mechanical investigation methods can quantify the environmental factors affecting primate locomotion to and from food, which makes up a large part of a primate's daily energy budget. We indicate that, despite the accumulation of much data on the material properties of primate foods, the introduction of new methods is allowing researchers to pursue new avenues of research and change paradigms in primate feeding ecology. Field methods are presented that could aid in the understanding of the extra-oral processing of foodstuffs by primates and enrich further studies into cognition and culture surrounding these types of behavior. We conclude that the use of in-field measurements and a greater understanding of the physics of primate environments are vital and exciting themes integral to the continued understanding of primate evolution and biology., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In birds and primates, the frequency of behavioural innovation has been shown to covary with absolute and relative brain size, leading to the suggestion that large brains allow animals to innovate, and/or that selection for innovativeness, together with social learning, may have driven brain enlargement. We examined the relationship between primate brain size and both technical (i.e. tool using) and non-technical innovation, deploying a combination of phylogenetically informed regression and exploratory causal graph analyses. Regression analyses revealed that absolute and relative brain size correlated positively with technical innovation, and exhibited consistently weaker, but still positive, relationships with non-technical innovation. These findings mirror similar results in birds. Our exploratory causal graph analyses suggested that technical innovation shares strong direct relationships with brain size, body size, social learning rate and social group size, whereas non-technical innovation did not exhibit a direct relationship with brain size. Nonetheless, non-technical innovation was linked to brain size indirectly via diet and life-history variables. Our findings support 'technical intelligence' hypotheses in linking technical innovation to encephalization in the restricted set of primate lineages where technical innovation has been reported. Our findings also provide support for a broad co-evolving complex of brain, behaviour, life-history, social and dietary variables, providing secondary support for social and ecological intelligence hypotheses. The ability to gain access to difficult-to-extract, but potentially nutrient-rich, resources through tool use may have conferred on some primates adaptive advantages, leading to selection for brain circuitry that underlies technical proficiency., (© 2016 The Author(s).)

The role of invertebrates in the evolution of human diet has been under-studied by comparison with vertebrates and plants. This persists despite substantial knowledge of the importance of the 'other faunivory', especially insect-eating, in the daily lives of non-human primates and traditional human societies, especially hunters and gatherers. Most primates concentrate on two phyla, Mollusca and Arthropoda, but of the latter's classes, insects (especially five orders: Coleoptera, Hymenoptera, Isoptera, Lepidoptera, Orthoptera) are paramount. An insect product, bees' honey, is particularly important, and its collection shows a reversal of the usual sexual division of labor. Human entomophagy involves advanced technology (fire, containers) and sometimes domestication. Insectivory provides comparable calorific and nutritional benefits to carnivory, but with different costs. Much insectivory in hominoids entails elementary technology used in extractive foraging, such as termite fishing by chimpanzees. Elucidating insectivory in the fossil and paleontological record is challenging, but at least nine avenues are available: remains, lithics, residues, DNA, coprolites, dental microwear, stable isotopes, osteology, and depictions. All are in play, but some have been more successful so far than others., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Combinatorial behavior involves combining different elements into larger aggregates with meaning. It is generally contrasted with compositionality, which involves the combining of meaningful elements into larger constituents whose meaning is derived from its component parts. Combinatoriality is commonly considered a capacity found in primates and other animals, whereas compositionality often is considered uniquely human. Questioning the validity of this claim, this multidisciplinary special issue of the International Journal of Primatology unites papers that each study aspects of combinatoriality and compositionality found in primate and bird communication systems, tool use, skills, and human language. The majority of authors conclude that compositionality is evolutionarily preceded by combinatoriality and that neither are uniquely human. This introduction briefly introduces readers to the major findings and issues raised by the contributors. [ABSTRACT FROM AUTHOR]

Tool use diversity is often considered to differentiate our two closest living relatives: the chimpanzee (Pan troglodytes) and the bonobo (P. paniscus). Chimpanzees appear to have the largest repertoire of tools amongst nonhuman primates, and in this species, many forms of tool use enhance food and water acquisition. In captivity, bonobos seem as adept as chimpanzees in tool use complexity, including in the foraging context. However, in the wild, bonobos have only been observed engaging in habitual tool use in the contexts of comfort, play, self-directed behaviour and communication, whilst no tool-assisted food acquisition has been reported. Whereas captive bonobos use tools for drinking, so far, the only report from the wild populations comes down to four observations of moss sponges used at Lomako. Here, we present the first report of tool use in the form of water scooping by a wild bonobo at LuiKotale. An adult female was observed and videotaped whilst using an emptied Cola chlamydantha pod to scoop and drink water from a stream. We discuss the conditions for such observations and the importance of looking out for rare behaviours and attempt to put the observation into the context of the opportunity versus necessity hypotheses. By adding novel information on tool use, our report contributes to the ongoing efforts to differentiate population-specific traits in the behavioural ecology of the bonobo. [ABSTRACT FROM AUTHOR]

Tool use by animals, traditionally studied mainly in captive primates due to its relevance to human evolution, has been investigated in both free-ranging and captive mammals. Here, I present a report on tree bark and branch use behaviours by a free-ranging Japanese marten (Martes melampus). The marten put its face in a water-filled container, looking for something, and then it proceeded to make a scooping motion with a bark held in its mouth. Subsequently, it picked up a branch with its mouth and tried to scoop something from the water with it. Upon inspecting the container approximately 2 weeks later, I found a larva belonging to the family Syrphidae. While it is unclear if the marten was trying to catch this larva, its behaviour resembled reach extension behaviour seen in chimpanzees. The use of bark or branches may provide an advantage by allowing access to objects in hard-to-reach positions. [ABSTRACT FROM AUTHOR]

Object interactions play an important role in human communication but the extent to which nonhuman primates incorporate objects in their social interactions remains unknown. To better understand the evolution of object use, this study explored how objects are used in social interactions in semi-wild chimpanzees (Pan troglodytes). We used an observational approach focusing on naturally occurring object actions where we examined their use and tested whether the production of object actions was influenced by the recipients' visual attention as well as by colony membership. The results show that chimpanzees adjusted both the type of object used, and the modality of object actions to match the visual attention of the recipient, as well as colony differences in the use of targeted object actions. These results provide empirical evidence highlighting that chimpanzees use objects in diverse ways to communicate with conspecifics and that their use may be shaped by social factors, contributing to our understanding of the evolution of human nonverbal communication, language, and tool use. [ABSTRACT FROM AUTHOR]

The modern human hand is an intriguing mix of primitive morphology and derived function. Traditionally, its form and function are explained as a functional "trade‐off" between the requirements of locomotion and manipulation, but recently acquired comparative, experimental and fossil evidence suggests that this functional trade‐off is more complex than conventional wisdom suggests. Moreover, when studying hand evolution within the hominin clade, the only morphological evidence comes from the hard‐tissues, and evidence about hand function must be inferred indirectly from the archaeological record. We lack information about critical aspects of hand form (e.g., soft tissues) and function (e.g., neurology) as well as non‐lithic evidence about behavior. Thus, comparative anatomical, experimental and ethological studies of modern humans and other primates are critical to making more informed inferences about hand use in the past. We review the relevant fossil and archaeological evidence within the relevant comparative context (e.g., other extant apes and dexterous monkeys) in an attempt to reconstruct hand evolution within the hominin clade. We conclude by summarizing our current understanding—or lack thereof—of the evolutionary history of the modern human hand. [ABSTRACT FROM AUTHOR]

While tool use has been widely reported in non-human animals for food acquisition, the use of tools for drinking has been largely overlooked, with primates being a notable exception. We documented tool-assisted water scooping and drinking in several Balinese long-tailed macaques (Macaca fascicularis), living in Ubud, Indonesia, over a period of four years. We observed repeated tool-assisted water scooping using leaves, nuts, pits, and stones. Our results indicate that this behaviour is associated with manual drinking and can be performed in a playful context. This population habitually engages in a cultural form of stone-assisted object play known as stone handling, and it has an overall propensity to manipulate objects in water. We discuss the relationship between instrumental and non-instrumental object-assisted actions, as well as the possibility for this behaviour to be a tradition in this population. This report offers new insights into the limited literature on tool-assisted drinking in monkeys. [ABSTRACT FROM AUTHOR]

We documented evidence of idiosyncratic but repeated twig-assisted genital stimulation by Balinese long-tailed macaques (Macaca fascicularis), living in Ubud, Indonesia. This population is known to customarily engage in genital stone-tapping/-rubbing, a behaviour expressed by males and females of different age classes as part of a broader cultural repertoire of stone-directed and overall playful actions known as stone handling. However, genital stimulation using other objects has never been reported in this population and species. We observed repeated and extensive twig-assisted genital stimulation in one adult female and one adult male. We also recorded three instances of twig-assisted genital stimulation in three additional individuals. Our results indicate that this behaviour is not accidental and may be sexually motivated; that is, it may be another form of tool-assisted masturbation in this primate population. This report provides a valuable addition to the increasing literature on tool-assisted behavioural innovations pertaining to self-care and possibly pleasure. [ABSTRACT FROM AUTHOR]

Several primate species use tools for a wide variety of functions, such as probing or obtaining out-of-reach food, both in captivity and in the wild. Given the ubiquitous presence of plants, the study of plant tool use may serve as a proxy to reconstruct archeologically invisible aspects of early human behavior. Chimpanzees (Pan troglodytes) are the most prolific non-human primate tool users. We evaluated the use of two artificial mounds filled with food in two groups of sanctuary-housed chimpanzees (N = 14) at Fundació Mona (Girona, Spain). We assessed how the group, the use and size of tools, posture, and the type of substratum affected chimpanzee behavior during an enrichment task that replicated termite fishing observed in wild chimpanzees. We also focused on the grasping postures and explored the manual laterality of individuals performing the task. We analyzed 290 min of video footage, including 5736 bouts of extractive foraging. Our results showed that individuals mainly performed the task alone, sitting on the ground, and probing with larger, rather than smaller, tools. Ten individuals showed manual preference: two showed a preference for using the left hand, while eight showed a preference for the right. Additionally, chimpanzees tended to use a variety of unimanual grip strategies. This study highlights the impact that enrichment activities that mimic realistic scenarios can have on the manual capacities of captive chimpanzees, enhancing the opportunity to develop further comparative studies with wild chimpanzees to understand the evolution of the manual abilities in human and non-human primates. [ABSTRACT FROM AUTHOR]

The way in which animals grasp objects to perform subsequent action execution allows studying their anticipatory abilities. We examined whether 11 capuchin monkeys (Sapajus spp.) were able to prospectively grasp a magnetic dowel to use it as a tool to retrieve a baited metallic container from a plexiglas box placed in front of them. We investigated whether and how initial dowel orientation (horizontal vs vertical) affected grasping and using the dowel to retrieve the container in two testing conditions: (1) 2-FE condition in which the dowel had two functional magnetic ends; (2) 1-FE condition in which the dowel had only one functional magnetic end. In the 2-FE condition, capuchins had to take into account the initial dowel orientation since both ends were functional, whereas in the 1-FE condition capuchins had also to take into account the initial functional end position when grasping the dowel. Capuchins were trained to grasp the dowel to put one functional end in contact with the metallic container. However, they did not learn to associate the functional end of the 1-FE dowel to successful retrieval. Capuchins showed better anticipatory planning (1) in 2-FE than in 1-FE condition and (2) when the dowel was initially positioned on the horizontal plane than on the vertical one. Moreover, hand preferences affected planning in the 1-FE condition. Results were discussed within the frameworks of primates' abilities to use abstract cues and on their abilities to process functional features and spatial cues and to perform mental rotations. [ABSTRACT FROM AUTHOR]

Once considered only a human behavior, reports of tool use by a variety of animals have accumulated. Likewise, various definitions of tool use have also amassed. Although some researchers argue that understanding the evolutionary drivers of tool use is more important than identifying and describing these behaviors, the central issue of defining what constitutes tool use has not been fully addressed. Here we analyze prominent definitions of tool use and review the application of these definitions in scientific and educational literature. We demonstrate that many behaviors recently described as tool use do not meet criteria for prevalent definitions, while other neglected behaviors may constitute a form of tool use. These examples show how the use of inconsistent definitions of tool use in research can result in different conclusions from the same observations. Our aim is to demonstrate that a universally acceptable definition of tool use based on traditional, evolutionary, and operational understanding of behavior is needed. The rationale is that this review will stimulate the consistent and explicit use of specific terminology in tool use research. This would help define specific examples of each natural observation from a common measuring stick, allowing better comparative studies and classification of these unique behaviors.//

Nonhuman great apes show remarkable behavioural flexibility. Some individuals are even able to use water as a tool: They spit water into a vertical tube to make a peanut float upwards until it comes into reach (floating peanut task; FPT). In the current study, we used the FPT to investigate how visual feedback, an end-state demonstration and a social demonstration affect task performance in nonhuman great apes in three experiments. Our results indicate that apes who had acquired the solution with a clear tube maintained it with an opaque one. However, apes starting with an opaque tube failed to solve the task. Additionally, facing the peanut floating on a water-filled tube (i.e., an end-state demonstration) promoted success independent on the availability of visual feedback. Moreover, experiencing how water was poured into the tube either by a human demonstrator or by a water tap that had been opened either by the ape or a human did not seem to be of further assistance. First, this study suggests that great apes require visual feedback for solving the FPT, which is no longer required after the initial acquisition. Second, some subjects benefit from encountering the end-state, a finding corroborating previous studies. [ABSTRACT FROM AUTHOR]

The ability to select the necessary means for a familiar task while the task itself or the respective tools are out of sight suggests a rudimentary form of planning. Here we investigated if and how a non-specialized tool using bird, the Goffin's cockatoo, can prospectively or retrospectively select the functional tool in a decision-making task featuring two different types of apparatuses and their corresponding tools. Each apparatus could only be employed with one specific type of tool. Either the apparatus was presented and occluded prior to the presentation of the tools (prospective condition) or the tools were presented and occluded prior to the presentation of the apparatus (retrospective condition). Our results suggest the birds can prospectively but not retrospectively select the correct tool, paralleling previous research in tool using apes, and indicate at least simple forms of prospective selection in the tool use of a species distantly related to primates. [ABSTRACT FROM AUTHOR]

Cultural diversity among social groups has recently been documented in multiple animal species. Investigations of the origin and spread of diverse behaviour at group level in wild-ranging animals have added valuable information on social learning mechanisms under natural conditions. Behavioural diversity has been especially informative in the case of dispersal, where the transfer of individuals between groups leads to a sudden exposure to unfamiliar behaviour. Little is known, however, about the underlying costs and benefits of cultural transmission in animals and humans alike, as efficiency of cultural variants is often difficult to measure. The chimpanzees, Pan troglodytes , of the Taï National Park in Ivory Coast are known to exhibit a number of cultural differences between social groups, including hammer selection for nut cracking. This provides the unique opportunity to quantify the efficiency of cultural variants. We compared foraging speed and number of hits applied during nut-cracking events between three neighbouring chimpanzee groups. Our results showed significant differences in nut-cracking efficiency, caused by hammer material selection and differences in the applied power of impact per nut. Persistent behavioural coherence within the respective groups implies that immigrants adjust their behaviour to local nut-cracking techniques, even when individual foraging success might be compromised. This suggests that the benefit of belonging to a social group might outweigh the benefits of maximizing individual foraging efficiency. The differences in nut-cracking efficiency between chimpanzee groups add to the ever-growing body of cultural variants in wild chimpanzees and expand our knowledge of the importance of group belonging and conformity in wild chimpanzees. [ABSTRACT FROM AUTHOR]

Snakes present a hazard to primates, both as active predators and by defensive envenomation. This risk might have been a selective pressure on the evolution of primate visual and cognitive systems, leading to several behavioral traits present in human and non-human primates, such as the ability to quickly learn to fear snakes. Primates seldom prey on snakes, and humans are one of the few primate species that do. We report here another case, the wild capuchin monkey ( Sapajus libidinosus), which preys on snakes. We hypothesized that capuchin monkeys, due to their behavioral plasticity, and cognitive and visual skills, would be capable of discriminating dangerous and non-dangerous snakes and behave accordingly. We recorded the behavioral patterns exhibited toward snakes in two populations of S. libidinosus living 320 km apart in Piauí, Brazil. As expected, capuchins have a fear reaction to dangerous snakes (usually venomous or constricting snakes), presenting mobbing behavior toward them. In contrast, they hunt and consume non-dangerous snakes without presenting the fear response. Our findings support the tested hypothesis that S. libidinosus are capable of differentiating snakes by level of danger: on the one hand they protect themselves from dangerous snakes, on the other hand they take opportunities to prey on non-dangerous snakes. Since capuchins and humans are both predators and prey of snakes, further studies of this complex relationship may shed light on the evolution of these traits in the human lineage. [ABSTRACT FROM AUTHOR]

Summary: O'Hara et al. (Current Biology, 31, 4512–4520, 2021) show that wild Goffin's cockatoos (Cacatua goffiniana) exhibit tool-related abilities at levels previously demonstrated by nonhuman primates or, in birds, only by those raised in captivity. Their data provide information about the cognitive and ecological underpinnings of this behavior and provide the impetus to search for additional examples of convergent evolution in avian and mammalian lines. [ABSTRACT FROM AUTHOR]

Culture extends biology in that the setting of development shapes the traditions that individuals learn, and over time, traditions evolve as occasional variations are learned by others. In humans, interactions with others impact the development of cognitive processes, such as sustained attention, that shape how individuals learn as well as what they learn. Thus, learning itself is impacted by culture. Here, we explore how social partners might shape the development of psychological processes impacting learning a tradition. We studied bearded capuchin monkeys learning a traditional tool-using skill, cracking nuts using stone hammers. Young monkeys practice components of cracking nuts with stones for years before achieving proficiency. We examined the time course of young monkeys' activity with nuts before, during, and following others' cracking nuts. Results demonstrate that the onset of others' cracking nuts immediately prompts young monkeys to start handling and percussing nuts, and they continue these activities while others are cracking. When others stop cracking nuts, young monkeys sustain the uncommon actions of percussing and striking nuts for shorter periods than the more common actions of handling nuts. We conclude that nut-cracking by adults can promote the development of sustained attention for the critical but less common actions that young monkeys must practice to learn this traditional skill. This work suggests that in nonhuman species, as in humans, socially specified settings of development impact learning processes as well as learning outcomes. Nonhumans, like humans, may be culturally variable learners. [ABSTRACT FROM AUTHOR]

Over a 6 month period during the dry season, from the end of October 2014 to the beginning of May 2015, we studied tool use behavior of previously unstudied and non-habituated savanna chimpanzees ( Pan troglodytes verus) living in the Comoé National Park, Ivory Coast (CI). We analyzed all the stick tools and leaf-sponges found that the chimpanzees used to forage for ants, termites, honey, and water. We found a particular behavior to be widespread across different chimpanzee communities in the park, namely, dipping for water from tree holes using sticks with especially long brush-tip modifications, using camera traps, we recorded adults, juveniles, and infants of three communities displaying this behavior. We compared water dipping and honey dipping tools used by Comoé chimpanzees and found significant differences in the total length, diameter, and brush length of the different types of fluid-dipping tools used. We found that water dipping tools had consistently longer and thicker brush-tips than honey dipping tools. Although this behavior was observed only during the late dry season, the chimpanzees always had alternative water sources available, like pools and rivers, in which they drank without the use of a tool. It remains unclear whether the use of a tool increases efficient access to water. This is the first time that water dipping behavior with sticks has been found as a widespread and well-established behavior across different age and sex classes and communities, suggesting the possibility of cultural transmission. It is crucial that we conserve this population of chimpanzees, not only because they may represent the second largest population in the country, but also because of their unique behavioral repertoire. [ABSTRACT FROM AUTHOR]

Cláudia Sousa was a founding member of the newly emerging and interdisciplinary field of primate archaeology. This discipline employs an archaeological approach to the study of nonhuman primates through the observation of their material culture - i. e. objects produced during tool use and manipulation - and has significant implications in the study of human evolution. [ABSTRACT FROM AUTHOR]

For several decades, it was largely assumed that stone tool use and production were abilities limited to the genus Homo. However, growing palaeontological and archaeological evidence, comparative extant primate studies, as well as results from methodological advancements in biomechanics and morphological analyses, have been gradually accumulating and now provide strong support for more advanced manual manipulative abilities and tool-related behaviours in pre-Homo hominins than has been traditionally recognized. Here, I review the fossil evidence related to early hominin dexterity, including the recent discoveries of relatively complete early hominin hand skeletons, and new methodologies that are providing a more holistic interpretation of hand function, and insight into how our early ancestors may have balanced the functional requirements of both arboreal locomotion and tool-related behaviours. [ABSTRACT FROM AUTHOR]

Recovering evidence of past human activities enables us to recreate behaviour where direct observations are missing. Here, we apply archaeological methods to further investigate cultural transmission processes in percussive tool use among neighbouring chimpanzee communities in the Taï National Park, Côte d'Ivoire, West Africa. Differences in the selection of nut-cracking tools between neighbouring groups are maintained over time, despite frequent female transfer, which leads to persistent cultural diversity between chimpanzee groups. Through the recovery of used tools in the suggested natal territory of immigrants, we have been able to reconstruct the tool material selection of females prior to migration. In combination with direct observations of tool selection of local residents and immigrants after migration, we uncovered temporal changes in tool selection for immigrating females. After controlling for ecological differences between territories of immigrants and residents our data suggest that immigrants abandoned their previous tool preference and adopted the pattern of their new community, despite previous personal proficiency of the same foraging task. Our study adds to the growing body of knowledge on the importance of conformist tendencies in animals. [ABSTRACT FROM AUTHOR]

Background: New Caledonian crows use a range of foraging tools, and are the only non-human species known to craft hooks. Based on a small number of observations, their manufacture of hooked stick tools has previously been described as a complex, multi-stage process. Tool behaviour is shaped by genetic predispositions, individual and social learning, and/or ecological influences, but disentangling the relative contributions of these factors remains a major research challenge. The properties of raw materials are an obvious, but largely overlooked, source of variation in tool-manufacture behaviour. We conducted experiments with wild-caught New Caledonian crows, to assess variation in their hooked stick tool making, and to investigate how raw-material properties affect the manufacture process. Results: In Experiment 1, we showed that New Caledonian crows' manufacture of hooked stick tools can be much more variable than previously thought (85 tools by 18 subjects), and can involve two newly-discovered behaviours: 'pulling' for detaching stems and bending of the tool shaft. Crows' tool manufactures varied significantly: in the number of different action types employed; in the time spent processing the hook and bending the tool shaft; and in the structure of processing sequences. In Experiment 2, we examined the interaction of crows with raw materials of different properties, using a novel paradigm that enabled us to determine subjects' rank-ordered preferences (42 tools by 7 subjects). Plant properties influenced: the order in which crows selected stems; whether a hooked tool was manufactured; the time required to release a basic tool; and, possibly, the release technique, the number of behavioural actions, and aspects of processing behaviour. Results from Experiment 2 suggested that at least part of the natural behavioural variation observed in Experiment 1 is due to the effect of raw-material properties. Conclusions: Our discovery of novel manufacture behaviours indicates a plausible scenario for the evolutionary origins, and gradual refinement, of New Caledonian crows' hooked stick tool making. Furthermore, our experimental demonstration of a link between raw-material properties and aspects of tool manufacture provides an alternative hypothesis for explaining regional differences in tool behaviours observed in New Caledonian crows, and some primate species. [ABSTRACT FROM AUTHOR]

There is now growing evidence that some animal species are able to plan for the future. For example great apes save and exchange tools for future use. Here we raise the question whether chimpanzees, orangutans, and bonobos would produce tools for future use. Subjects only had access to a baited apparatus for a limited duration and therefore should use the time preceding this access to create the appropriate tools in order to get the rewards. The apes were tested in three conditions depending on the need for pre-prepared tools. Either eight tools, one tool or no tools were needed to retrieve the reward. The apes prepared tools in advance for future use and they produced them mainly in conditions when they were really needed. The fact that apes were able to solve this new task indicates that their planning skills are flexible. However, for the condition in which eight tools were needed, apes produced less than two tools per trial in advance. However, they used their chance to produce additional tools in the tool use phase-thus often obtaining most of the reward from the apparatus. Increased pressure to prepare more tools in advance did not have an effect on their performance. Am. J. Primatol. 77:254-263, 2015. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

We investigated the process of nut-cracking acquisition in a semi-free population of tufted capuchin monkeys ( Sapajus sp) in São Paulo, Brazil. We analyzed the cracking episodes from monkeys of different ages and found that variability of actions related to cracking declined. Inept movements were more frequent in juveniles, which also showed an improvement on efficient striking. The most effective behavioral sequence for cracking was more frequently used by the most experienced monkeys, which also used non-optimal sequences. Variability in behavior sequences and actions may allow adaptive changes to behavior under changing environmental conditions. [ABSTRACT FROM AUTHOR]

Capuchin monkeys are well known for population variation in the use of stone tools and the types of food items consumed. In order to determine adaptability in stone tool use, we investigated a never before studied population of wild capuchin monkey ( Sapajus libidinosus) displaying terrestrial habits in a Caatinga environment. To carry out this study we recorded physical evidence of the use of stone tools as well as made direct observations through trap cameras. During a 15-month period, we studied a group of Sapajus libidinosus in Serra Talhada, Pernambuco, Brazil. In total, 257 anvils and 395 hammers were identified, characterized, and monitored. We identified five types of food items exploited at these 'tool use sites': Syagrus oleracea (catolé palm), Manihot epruinosa (manioc), Pilosocereus pachycladus (facheiro), Tacinga inamoena (quípa), and Commiphora leptophloeos (imburana de cambão). Five hundred three video clips of capuchin monkeys were recorded, 43 of which involved the use of stone tools. The results indicated evidence of adaptability in tool use by the capuchins. We verified that the rigidity and size of the food item, along with the presence or absence of spines seem to influence the choice of stone tools made by the animals for processing the food. The recurring use of tools for the processing of cacti was especially noteworthy and it appears that the presence of spines predisposes the capuchins to use stones to process them. A significant difference was observed between the characteristics of the anvils and the weight of the hammers according to the food item consumed. The use of tools enabled the animals to access otherwise unavailable or difficult to acquire food items within a Caatinga habitat. Adaptability in the use of stone tools by the capuchin monkey population of Serra Talhada provides an example of the complexity that these primates demonstrate in food processing. Am. J. Primatol. 76:967-977, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Providing adults with relevant information (knowledge that they will be tested at some future time) increases motivation to remember. Research has shown that it is more effective to have this information prior to, rather than after, an encoding phase. We investigated this effect in apes and children in the context of tool-use tasks. In Experiment 1 we presented chimpanzees, orangutans, and bonobos with two tool-use tasks and three different two-tool sets. We had two conditions: prospective (PP) and retrospective (RP). In the PP subjects were shown the task that they would have to solve before they were shown the tools with which they could solve it. In the RP this order was reversed. Apes remembered the location of the useful tool better in the PP than in the RP. In Experiment 2 we presented 3- and 4-year-olds with the same conditions. Both age groups remembered the location of the correct tool in the PP, but only the 4-year-olds did so in the RP. Thus providing apes and preschool children with relevant information prior to, rather than after, the encoding phase enhances memory. These results have important implications for the understanding of the evolution of memory in general, and encoding mechanisms in particular. [ABSTRACT FROM PUBLISHER]

There is extensive evidence for an early vertebrate origin of lateralized motor behavior and of related asymmetries in underlying brain systems. We investigate human lateralized motor functioning in a broad comparative context of evolutionary neural reorganization. We quantify evolutionary trends in the fronto-cerebellar system (involved in motor learning) across 46 million years of divergent primate evolution by comparing rates of evolution of prefrontal cortex, frontal motor cortex, and posterior cerebellar hemispheres along individual branches of the primate tree of life. We provide a detailed evolutionary model of the neuroanatomical changes leading to modern human lateralized motor functioning, demonstrating an increased role for the fronto-cerebellar system in the apes dating to their evolutionary divergence from the monkeys (∼30 million years ago (Mya)), and a subsequent shift toward an increased role for prefrontal cortex over frontal motor cortex in the fronto-cerebellar system in the Homo- Pan ancestral lineage (∼10 Mya) and in the human ancestral lineage (∼6 Mya). We discuss these results in the context of cortico-cerebellar functions and their likely role in the evolution of human tool use and speech. [ABSTRACT FROM AUTHOR]

We examined whether eight capuchins and eight chimpanzees were able to retrieve a reward placed inside a tube, of varying length, by selecting the correct stick from different sets of three sticks differing in length (functional feature) and handle (non-functional feature). Moreover, to investigate whether seeing the stick inside the tube (visual feedback) improves performance, half of the subjects were tested with a transparent apparatus and the other half with an opaque apparatus. Phase 1 included (a) Training 1 in which each stick had a different handle and (b) Transfer 1 in which the handles were switched among sticks, so that the functional tool had the same length but a different handle than before. The seven chimpanzees and one capuchin that passed Transfer 1 received Transfer 2. The other subjects received (a) Training 2, which used the same sticks from Phase 1 with handles switched in every trial, and (b) Transfer 2 in which the tube was longer, all sticks had the same new handle, and the formerly longest tool became intermediate in length. Eight chimpanzees and three capuchins passed Transfer 2. Results showed that (1) chimpanzees applied relational structures in tool using tasks more quickly than capuchins and (2) capuchins required more varied experience to attend to the functional feature of the tool. Interestingly, visual feedback did not improve performance in either species. [ABSTRACT FROM AUTHOR]

The article presents information on a study which reported the spontaneous modification and use of sticks to fish for termites observed in one group of endangered Neotropical primates, wild blonde capuchins, Cebus flavius, living in a fragment of Atlantic Forest. Techniques utilized sequentially by the capuchins during termite fishing are nest tapping an stick rotation. The effectiveness of the fishing techniques used by the primates was also tested.

Three capuchin monkeys (Cebus apella) were tested on a 2-choice discrimination task designed to examine their knowledge of support, modeled after Hauser, Kralik, and Botto-Mahan's (1999) experiments with tamarins. This task involved a choice between 2 pieces of cloth, including 1 with a food reward placed on its surface, and a second cloth with the food reward next to its surface. After reliably solving the basic problem, the capuchins were tested with various alternations of the original food reward and cloth. The capuchins were able to solve the initial task quickly, and generalize their knowledge to additional functional and nonfunctional variations of the problem. In comparison to the tamarins previously tested on this problem (Hauser et al., 1999), the capuchins were able to reach criterion faster during the training and food size conditions and showed a greater ability to inhibit reaching toward larger food rewards that were unavailable. [ABSTRACT FROM AUTHOR]

Relatively few studies have explored sex differences in the use of foraging tools among primates other than apes. Although male primates are thought to be more innovative, researchers have reported a female sex bias in the use of feeding tools in wild chimpanzees. We investigate here the nature and extent of sex differences in foraging tool use over 12 mo in a free-ranging group of bearded capuchins (2 males, 5 females, and 3 juveniles) living in the dry Caatinga forests of the Serra da Capivara National Park, Piaui, Brazil. These capuchins used 3 major types of feeding tools: 1) tools for probing; 2) tools for pounding/cracking; and 3) digging stones to extract tubers or roots. Adult males performed 63% ( n = 134) of all events of tool use and used tools significantly more frequently than did females, although male bout lengths across all tools (57 s ± 7.9 SE) were equivalent to those of adult females (47.3 s ± 12.6 SE). Both sexes used digging and cracking tools, although at different rates, whereas adult males used sticks to probe for prey and other rewards far more than females. Differential opportunities to use tools were not apparent: >71% of tool-use events occurred on the ground, and males and females spent equal time on the ground. We suggest that sex differences in tool use may function as opportunities for male signaling of investment quality. [ABSTRACT FROM AUTHOR]

Stone tool use for nut cracking consists of placing a hard-shelled nut onto a stone anvil and then cracking the shell open by pounding it with a stone hammer to get to the kernel. We investigated the acquisition of tool use for nut cracking in a group of captive chimpanzees to clarify what kind of understanding of the tools and actions will lead to the acquisition of this type of tool use in the presence of a skilled model. A human experimenter trained a male chimpanzee until he mastered the use of a hammer and anvil stone to crack open macadamia nuts. He was then put in a nut-cracking situation together with his group mates, who were naïve to this tool use; we did not have a control group without a model. The results showed that the process of acquisition could be broken down into several steps, including recognition of applying pressure to the nut, emergence of the use of a combination of three objects, emergence of the hitting action, using a tool for hitting, and hitting the nut. The chimpanzees recognized these different components separately and practiced them one after another. They gradually united these factors in their behavior leading to their first success. Their behavior did not clearly improve immediately after observing successful nut cracking by a peer, but observation of a skilled group member seemed to have a gradual, long-term influence on the acquisition of nut cracking by naïve chimpanzees. [ABSTRACT FROM AUTHOR]

There is continued debate over the factors influencing handedness in captive and wild primates, notably chimpanzees. Previous studies in wild chimpanzees have revealed population-level left-handedness for termite fishing. Here we examined hand preferences and performance on a tool use task designed to simulate termite fishing in a sample of 190 captive chimpanzees to evaluate whether patterns of hand use in captive chimpanzees differed from those observed for wild apes. No population-level handedness was found for this task; however, significant sex differences in preference and performance were found, with males showing greater left-handedness and poorer performance compared to females. We also found that the hand preferences of offspring were significantly positively correlated with the hand preferences of their mothers. Lastly, older females performed more slowly on the task compared to younger individuals. The overall results neither confirm nor reject previous hypotheses claiming that raising chimpanzees in captivity induces right-handedness, but rather suggest that other factors may account for differences in hand preferences for tool use seen in wild and captive chimpanzees. [ABSTRACT FROM AUTHOR]

The hypothesis that large brains allow animals to produce novel behaviour patterns is supported by the correlation between brain size, corrected for body size, and the frequency of foraging innovations reported in the literature for both birds and primates. In birds, foraging innovations have been observed in over 800 species, and include behaviours that range from eating a novel food to using tools. Previous comparative studies have quantified innovativeness by summing all reports of innovative behaviour, regardless of the nature of the innovation. Here, we use the variety of foraging innovations recorded for birds to see which of two classic hypotheses best accounts for the relationship between innovativeness and brain size: the technical intelligence hypothesis or the opportunistic-generalism intelligence hypothesis. We classified 2182 innovation cases into 12 categories to quantify the diversity of innovations performed by each of 76 avian families. We found that families with larger brains had a greater repertoire of innovations, and that innovation diversity was a stronger predictor of residual brain size than was total number of innovations. Furthermore, the diversity of technical innovations displayed by bird families was a much better predictor of residual brain size than was the number of food type innovations, providing support for the technical intelligence hypothesis. Our results suggest that the cognitive capacity required to perform a wide variety of novel foraging techniques underpins the positive relationship between innovativeness and brain size in birds. We include a summary of innovation data for 803 species as . [Copyright &y& Elsevier]

Wild bearded capuchins (Cebus libidinosus, quadrupedal, medium-sized monkeys) crack nuts using large stones. We examined the kinematics and energetics of the nut-cracking action of two adult males and two adult females. From a bipedal stance, the monkeys raised a heavy hammer stone (1.46 and 1.32 kg, from 33 to 77% of their body weight) to an average height of 0.33 m, 60% of body length. Then, they rapidly lowered the stone by flexing the lower extremities and the trunk until the stone contacted the nut, A hit consisting of an upward phase and a downward phase averaged 0.74 s in duration. The upward phase lasted 69% of hit duration. All subjects added discernable energy to the stone in the downward phase. The monkeys exhibited individualized kinematic strategies, similar to those of human weight lifters. Capuchins illustrate that human-like bipedal stance and large body size are unnecessary to break tough objects from a bipedal position. The phenomenon of bipedal nut-cracking by capuchins provides a new comparative reference point for discussions of percussive tool use and bipedality in primates. [ABSTRACT FROM AUTHOR]

The extent to which tool-using animals take into account the properties of the tool is little explored. The use of percussors to crack open encapsulated fruit is a complex form of tool use, the choice of an adequate tool being a critical aspect in success. Several properties (e.g., material, resistance, friability, shape and weight) affect the suitability of an object to open a hard-shelled nut, with weight being amongst the most important factors. In general, heavier tools require fewer strikes to crack open a nut. [ABSTRACT FROM AUTHOR]

Wild chimpanzees are known to have a different repertoire of tool use unique to each community. For example, “ant-dipping” is a tool use behavior known in several chimpanzee communities across Africa targeted at driver ants (Dorylus spp.) on the ground, whereas “ant-fishing,” which is aimed at carpenter ants (Camponotus spp.) in trees, has primarily been observed among the chimpanzees of Mahale in Tanzania. Although the evidence for differences between field sites is accumulating, we have little knowledge on how these tool use behaviors appear at each site and on how these are modified over time. This study reports two“ant-fishing” sessions which occurred 2 years apart by a young male chimpanzee at Bossou, Guinea. Ant-fishing had never been observed before in this community over the past 27 years. During the first session, at the age of 5, he employed wands of similar length when ant-fishing in trees to those used for ant-dipping on the ground, which is a customary tool use behavior of this community. Two years later, at the age of 7, his tools for ant-fishing were shorter and more suitable for capturing carpenter ants. This observation is a rare example of innovation in the wild and does provide insights into problem-solving and learning processes in chimpanzees. Am. J. Primatol. 70:699–702, 2008. © 2008 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Primates' understanding of tool functionality has been investigated extensively using a paradigm in which subjects are presented with a tool that they must use to obtain an out-of-reach reward. After being given experience on an initial problem, monkeys can transfer their skill to tools of different shapes while ignoring irrelevant tool changes (e.g., color). In contrast, monkeys without initial training perform poorly on the same tasks. Compared to most monkeys, great apes show a clear propensity for tool using and may not require as much experience to succeed on tool functionality tasks. We investigated this question by presenting 171 apes (Pan troglodytes, Pan paniscus, Gorilla gorilla, and Pongo pygmaeus) with several tool-use problems without giving them initial training or familiarizing them with the test materials. Apes succeeded without experience, but only on problems based on basic properties such as the reward being supported by an object. However, only minimal experience was sufficient to allow them to quickly improve their performance on more complex problems in which the reward was not in contact with the tool. [ABSTRACT FROM AUTHOR]

Studies of wild capuchins suggest an important role for social learning, but experiments with captive subjects have generally not supported this. Here we report social learning in two quite different populations of capuchin monkeys ( Cebus apella). In experiment 1, human-raised monkeys observed a familiar human model open a foraging box using a tool in one of two alternative ways: levering versus poking. In experiment 2, mother-raised monkeys viewed similar techniques demonstrated by monkey models. A control group in each population saw no model. In both experiments, independent coders detected which technique experimental subjects had seen, thus confirming social learning. Further analyses examined fidelity of copying at three levels of resolution. The human-raised monkeys exhibited fidelity at the highest level, the specific tool use technique witnessed. The lever technique was seen only in monkeys exposed to a levering model, by contrast with controls and those witnessing poke. Mother-reared monkeys instead typically ignored the tool and exhibited fidelity at a lower level, tending only to re-create whichever result the model had achieved by either levering or poking. Nevertheless this level of social learning was associated with significantly greater levels of success in monkeys witnessing a model than in controls, an effect absent in the human-reared population. Results in both populations are consistent with a process of canalization of the repertoire in the direction of the approach witnessed, producing a narrower, socially shaped behavioural profile than among controls who saw no model. [ABSTRACT FROM AUTHOR]

During the course of a 3-year ecological study on Cross River gorillas (Gorilla gorilla diehli) at the Kagwene Mountain in Cameroon, we observed three cases of tool use which may be unique to the gorillas of this region and possibly learned through interactions with humans. A non-habituated group of Cross River gorillas threw fistfuls of grass toward humans in display contexts. An individual gorilla was also observed to throw a detached branch toward researchers during another encounter. The third encounter occurred between the focal group and a local man, in which the man threw stones at the gorillas and they reacted by throwing fistfuls of grass back at him. We describe these observations and speculate that this sub-population of gorillas developed this display behavior as a response to particular local conditions. Am. J. Primatol. 69:1307–1311, 2007. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

A trademark of Homo sapiens is the enormous variation in behavioral patterns across populations. Insight into the development of human cultures can be aided by studies on communities of Pan across Africa that display unique combinations of social behavior and elementary technology. Only cross-population comparisons can reveal whether the diversity reflects differential genetics, environmental constraints, or is a cultural variant. However, the recently recognized and most endangered subspecies, Pan troglodytes vellerosus, remains completely unstudied in this respect. We report first evidence from a new long-term study of Nigerian chimpanzees at Gashaka. Their dietary composition is highly varied and they have to cope with high concentrations of antifeedant defenses of plants against consumption. Gashaka chimpanzees use a varied tool kit for extractive foraging. For example, they harvest insects throughout the year, via digging sticks and probes, to obtain honey from stingless-bee and honeybee nests, dipping wands to prey on army ants, and fishing rods to eat arboreal ants. Tools appeared to be custom-made with a considerable degree of standardization in length, diameter, and preferential use of distal ends. Moreover, compared to the rainy season, tools were longer during the dry season when insects retreat further into their nests. Many of the expressions of subsistence technology seem to be environmentally constrained. Most notably, the absence of termite-eating could reflect a low abundance of mounds. Other traits may represent cultural variation. For example, the chimpanzees did not hammer open 2 types of hard-shelled nuts with tools, unlike what occurs elsewhere in West Africa. The prevalence of elementary technology may indicate that the material culture of Gashaka chimpanzees is most related to core cultural tendencies of Central African populations. [ABSTRACT FROM AUTHOR]

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