How tufted capuchin monkeys (Cebus apella spp) and common chimpanzees (Pan troglodytes) align objects to surfaces: insights into spatial reasoning and implications for tool use

This report addresses phylogenetic variation in a spatial skill that underlies tool use: aligning objects to a feature of a surface. Fragaszy and Cummins-Sebree's [Behavioral and Cognitive Neuroscience Reviews 4:282-306, 2005] model of relational spatial reasoning and Skill Development and Perception-Action theories guided the design of the study. We examined how capuchins and chimpanzees place stick objects of varying shapes into matching grooves on a flat surface. Although most individuals aligned the long axis of the object with the matching groove more often than expected by chance, all typically did so with poor precision. Some individuals managed to align a second feature, and only one (a capuchin monkey) achieved above-chance success at aligning three features with matching grooves. Our findings suggest that capuchins and chimpanzees do not reliably align objects along even one axis, and that neither species can reliably or easily master object placement tasks that require managing two or more spatial relations concurrently. Moreover, they did not systematically vary their behavior in a manner that would aid discovery of the affordances of the stick-surface combination beyond sliding the stick along the surface (which may have provided haptic information about the location of the groove). These limitations have profound consequences for the forms of tool use we can expect these individuals to master.     

Flexible and conservative features of social systems in tufted capuchin monkeys: comparing the socioecology of Sapajus libidinosus and Sapajus nigritus

Socioecological models assume that primates adapt their social behavior to ecological conditions, and predict that food availability and distribution, predation risk and risk of infanticide by males affect patterns of social organization, social structure and mating system of primates. However, adaptability and variation of social behavior may be constrained by conservative adaptations and by phylogenetic inertia. The comparative study of closely related species can help to identify the relative contribution of ecological and of genetic determinants to primate social systems. We compared ecological features and social behavior of two species of the genus Sapajus, S. nigritus in Carlos Botelho State Park, an area of Atlantic Forest in S?o Paulo state, and S. libidinosus in Fazenda Boa Vista, a semi-arid habitat in Piauí state, Brazil. S. libidinosus perceived higher predation risk and fed on clumped, high quality, and usurpable resources (fruits) all year round, whereas S. nigritus perceived lower predation risk and relied on evenly distributed, low-quality food sources (leaves) during periods of fruit shortage. As predicted by socioecology models, S. libidinosus females were philopatric and established linear and stable dominance hierarchies, coalitions, and grooming relationships. S. nigritus females competed less often, and could transfer between groups, which might explain the lack of coalitions and grooming bonds among them. Both populations presented similar group size and composition and the same polygynous mating system. The species differed from each other in accordance with differences in the characteristics of their main food sources, as predicted by socioecological models, suggesting that phylogenetic inertia does not constrain social relationships established among female Sapajus. The similarity in mating systems indicates that this element of the social system is not affected by ecological variables and thus, is a more conservative behavioral feature of the genus Sapajus.     

Making space for traditions

For quite some time, the question of continuity across species with respect to culture has been linked in the academic world with definitional issues: What is culture, and how we can identify culture in a nonverbal species? 1 - 4 Behavioral scientists agree that behavioral traditions are that aspect of culture we can study in nonhuman animals, and we recognize that traditions are widespread in the animal kingdom (reviewed in Fragaszy and Perry, 5 see Laland and Hoppitt 6 ). However, confirming candidate traditions in nonhuman primates has proven frustratingly difficult. The difficulties experienced in identifying and studying traditions in nonhuman primates are correctable because they arise more from a combination of poor logic and conceptual confusion than from an inability to collect appropriate data. I argue that explicit evidence concerning social learning is necessary to evaluate the status of a behavioral practice as a tradition, and I suggest some ways that such evidence can be collected in natural settings using correlational methods and longitudinal designs. Clearer understanding of the social basis of traditions in nonhuman animals is essential to make headway in understanding their relation to human culture. No matter what else one includes in a definition of culture, a social basis for its existence is axiomatic.     

Coexistence Between Humans and Capuchins (<Emphasis Type="Italic">Sapajus libidinosus</Emphasis>): Comparing Observational Data with Farmers’ Perceptions of Crop Losses

Foraging on anthropogenic food by wildlife is a prevalent form of human–wildlife interaction. Few studies have evaluated the impact of wildlife crop foraging in Neotropical areas where small-scale agriculture is practiced and the habitat has not been heavily altered. Our objectives were 1) to evaluate the perceptions of small-scale farmers living in southern Piauí (Brazil) of the impact of bearded capuchins (Sapajus libidinosus) on their crops and 2) quantify crop losses due to the monkeys and other vertebrates. In 2013, we interviewed 78 residents about the impact of capuchins on their crops. Subsequently, we recorded foraging by vertebrate animals in corn fields, and evaluated farmers’ crop losses. The farmers showed a positive attitude toward the capuchins and their perceptions of wildlife behavior were generally accurate. The impact of wildlife varied in relation to the field’s location, number of foraging individuals, and time spent foraging, as well as plant growth patterns. Vertebrates consumed between 23 and 100 % of the crops. Capuchins consumed the majority of crop losses, though birds consumed up to a third. The presence of a watchman reduced losses from wildlife by 66 %. In conclusion, although capuchins forage flexibly on anthropogenic crops, in a society relying on subsistence agriculture, their impact is perceived to be moderate overall. Peaceful coexistence between humans and monkeys favors conservation actions targeted toward protection of the capuchins and their habitat, both of which are seriously threatened by industrial agriculture in this region.     

Percussive tool use by Ta? 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.     

Growth and reproduction in captive tufted capuchins (Cebus apella)

We present data on weight and reproduction from a colony of tufted capuchins monkeys (Cebus apella) over a 12 year period. The data constitute a normative record for this species. Weight at birth averages 210 g, and infants gain weight rapidly. Females typically first conceived just after their fifth birthday, and males were fertile by 4 years, 5 months. Interbirth intervals average 576 days. Eighty-seven percent of live-born infants survived past 6 months. Three of eight live-born infants that died prior to 6 months succumbed from trauma inflicted by cage mates. Am. J. Primatol. 44:197–203, 1998. © 1998 Wiley-Liss, Inc.     

Adult and juvenile bearded capuchin monkeys handle stone hammers differently during nut-cracking

Wild bearded capuchin monkeys (Sapajus libidinosus) habitually use stone hammers to crack open palm nuts and seeds on anvils. This activity requires strength, balance, and precise movement of a large stone with respect to the item placed on an anvil. We explored how well young monkeys cope with these challenges by examining their behavior and the behavior of adults while they cracked palm nuts using a stone. Using video records, we compared actions of six juvenile (2–5 years) and six adult (7+ years) wild monkeys during their first 20 strikes with one unfamiliar ellipsoid, quartzite stone (540 g), and the outcomes of these strikes. Compared with adults, juveniles cracked fewer nuts, performed a more diverse set of exploratory actions, and less frequently placed one or both hands on top of the stone on the downward motion. Adults and juveniles displayed similar low frequencies of striking with a slanted trajectory, missing the nut, and losing control over the nut or stone after striking. These findings indicate that young monkeys control the trajectory of a stone adequately but that is not sufficient to crack nuts as effectively as adults do. Compared with juveniles, adults more quickly perceive how to grip the stone efficiently, and they are able to adjust their grip dynamically during the strike. Young monkeys develop expertise in the latter aspects of cracking nuts over the course of several years of regular practice, indicating that perceptual learning about these aspects of percussion occurs slowly. Juvenile and adult humans learning to use stones to crack nuts also master these features of cracking nuts very slowly.