IMPULSE CONTROL AND COOPERATION IN CAPUCHIN MONKEYS (Cebus apella)

The benefits animals derive from living in social groups have produced the evolution of many forms of cooperative behavior. To cooperate, two or more individuals coordinate their actions to accomplish a common goal. One cognitive process that has the potential to influence cooperation is self control. Individuals delaying their impulsive choice for an immediate reward may potentially receive a larger reward later by cooperating with others. In this study, I measured whether brown capuchin monkeys (Cebus apella) were capable of impulse control and whether impulse control was related to cooperation. Impulse control and cooperation were measured using a lazy susan-like apparatus, on which animals could turn a wheel to receive food rewards. The capuchins went through two training phases that taught them how to turn the wheel efficiently to obtain rewards and how to turn the wheel to obtain the larger of two rewards. After training, I tested impulse control by giving the capuchins a choice between a smaller and a larger reward placed at shorter or more distant locations on the wheel. The capuchins demonstrated impulse control in that they tended to inhibit the impulse to select the smaller reward when it was closer and easier to reach and instead selected the larger reward when it was farther away. Cooperation was tested in all possible dyads of seven individuals, a total of 21 dyads, by allowing each dyad 10 trials to work together with effort on the lazy-susan so that each would obtain a reward. Seventeen out of 21 dyads cooperated by simultaneously moving the wheel in the same direction. The correlation between how often a particular dyad cooperated and their average impulse control score was not statistically significant, r(21) = -.125, p = .591. Capuchins demonstrated impulse control and cooperation using this novel apparatus but the two abilities were not related. Other factors such as the unique social relationship between two individuals may play a more prominent role in the motivation to cooperate rather than the cognitive capacity to inhibit behavior.

The Use of Human and Conspecific Gestures By Capuchin Monkeys to Solve an Object-Choice Task

Most primates live in highly complex social systems, and therefore have evolved similarly complex methods of communicating with each other. One type of communication is the use of manual gestures, which are only found in primates. No substantial evidence exists indicating that monkeys use communicative gestures in the wild. However, monkeys may demonstrate the ability to learn and/or use gestures in certain experimental paradigms since they¿ve been shown to use other visual cues such as gaze. The purpose of this study was to investigate if ten brown capuchin monkeys (Cebus apella) were able to use gestural cues from monkeys and a pointing cue from a human to obtain a hidden reward. They were then tested to determine if they could transfer this skill from monkeys to humans and from humans to monkeys. One group of monkeys was trained and tested using a conspecific as the cue giver, and was then tested with a human cue-giver. The second group of monkeys began training and testing with a human cue giver, and was then tested with a monkey cue giver. I found that two monkeys were able to use gestural cues from conspecifics (e.g., reaching) to obtain a hidden reward and then transfer this ability to a pointing cue from a human. Four monkeys learned to use the human pointing cue first, and then transferred this ability to use the gestural cues from conspecifics to obtain a hidden reward. However, the number of trials it took for each monkey to transfer the ability varied considerably. Some subjects spontaneously transferred in the minimum number of trials needed to reach my criteria for successfully obtaining hidden rewards (N = 40 trials), while others needed a large number of trials to do so (e.g. N = 190 trials). Two subjects did not perform successfully in any of the conditions in which they were tested. One subject successfully used the human pointing cue and a human pointing plus vocalization cue, but did not learn the conspecific cue. One subject learned to use the conspecific cue but not the human pointing cue. This was the first study to test if brown capuchin monkeys could use gestural cues from conspecifics to solve an object choice task. The study was also the first to test if capuchins could transfer this skill from monkeys to humans and from humans to monkeys. Results showed that capuchin monkeys were able to flexibly use communicative gestures when they were both unintentionally given by a conspecific and intentionally given by a human to indicate a source of food.

Stone tool use by adult wild bearded capuchin monkeys (Cebus libidinosus). Frequency, efficiency and tool selectivity

Chimpanzees have been the traditional referential models for investigating human evolution and stone tool use by hominins. We enlarge this comparative scenario by describing normative use of hammer stones and anvils in two wild groups of bearded capuchin monkeys (Cebus libidinosus) over one year. We found that most of the individuals habitually use stones and anvils to crack nuts and other encased food items. Further, we found that in adults (1) males use stone tools more frequently than females, (2) males crack high resistance nuts more frequently than females, (3) efficiency at opening a food by percussive tool use varies according to the resistance of the encased food, (4) heavier individuals are more efficient at cracking high resistant nuts than smaller individuals, and (5) to crack open encased foods, both sexes select hammer stones on the basis of material and weight. These findings confirm and extend previous experimental evidence concerning tool selectivity in wild capuchin monkeys (Visalberghi et al., 2009b; Fragaszy et al., 2010b). Male capuchins use tools more frequently than females and body mass is the best predictor of efficiency, but the sexes do not differ in terms of efficiency. We argue that the contrasting pattern of sex differences in capuchins compared with chimpanzees, in which females use tools more frequently and more skillfully than males, may have arisen from the degree of sexual dimorphism in body size of the two species, which is larger in capuchins than in chimpanzees. Our findings show the importance of taking sex and body mass into account as separate variables to assess their role in tool use. (C) 2011 Elsevier Ltd. All rights reserved.

Model of interactive visualization of diffusion processes from different strains, and source routes and spatial diffusion of capuchin monkeys over the past 6 million years

Source routes and Spatial Diffusion of capuchin monkeys over the past 6 million years, rebuilt in the SPREAD 1.0.6 from the MCC tree. The map shows the 10 different regions to which distinctive samples were associated. The different transmission routes have been calculated from the average rate over time. Only rates with Bayes factor> 3 were considered as significantly different from zero. Significant diffusion pathways are highlighted with color varying from dark brown to red, being the dark brown less significant rates and deep red the most significant rates.

A Comparative Assessment of Hand Preference in Captive Red Howler Monkeys, Alouatta seniculus and Yellow-Breasted Capuchin Monkeys, Sapajus xanthosternos

There are two major theories that attempt to explain hand preference in non-human primates-the `task complexity' theory and the `postural origins' theory. In the present study, we proposed a third hypothesis to explain the evolutionary origin of hand preference in non-human primates, stating that it could have evolved owing to structural and functional adaptations to feeding, which we refer to as the `niche structure' hypothesis. We attempted to explore this hypothesis by comparing hand preference across species that differ in the feeding ecology and niche structure: red howler monkeys, Alouatta seniculus and yellow-breasted capuchin monkeys, Sapajus xanthosternos. The red howler monkeys used the mouth to obtain food more frequently than the yellow-breasted capuchin monkeys. The red howler monkeys almost never reached for food presented on the opposite side of a wire mesh or inside a portable container, whereas the yellow-breasted capuchin monkeys reached for food presented in all four spatial arrangements (scattered, on the opposite side of a wire mesh, inside a suspended container, and inside a portable container). In contrast to the red howler monkeys that almost never acquired bipedal and clinging posture, the yellow-breasted capuchin monkeys acquired all five body postures (sitting, bipedal, tripedal, clinging, and hanging). Although there was no difference between the proportion of the red howler monkeys and the yellow-breasted capuchin monkeys that preferentially used one hand, the yellow-breasted capuchin monkeys exhibited an overall weaker hand preference than the red howler monkeys. Differences in hand preference diminished with the increasing complexity of the reaching-for-food tasks, i.e., the relatively more complex tasks were perceived as equally complex by both the red howler monkeys and the yellow-breasted capuchin monkeys. These findings suggest that species-specific differences in feeding ecology and niche structure can influence the perception of the complexity of the task and, consequently, hand preference.

Evaluation of dental pulp repair using low level laser therapy (688 nm and 785 nm) morphologic study in capuchin monkeys

The aim of this study was to evaluate the hypothesis that low-level laser therapy (LLLT) 688 nm and 785 nm accelerate dentin barrier formation and repair process after traumatic pulp exposure. The sample consisted of 45 premolars of capuchin monkeys (Cebus apella) with pulp exposure Class V cavities. All premolars were treated with calcium hydroxide (Ca(OH)(2)), divided in groups of 15 teeth each, and analyzed on 7(th), 25(th), and 60(th) day. Group GI - only Ca(OH)(2), GIF- laser 688 nm, and GIII - laser 785 nm. Laser beam was used in single and punctual dose with the parameters: continuous, 688 nm and 785 nm wavelength, tip`s area of 0.00785 cm(2), power 50 mW, application time 20 s, dose 255 J/cm(2), energy 2 J. Teeth were capped with Ca(OH)(2), Ca(OH)(2) cement and restored with amalgam. All groups presented pulp repair. On 25(th) day the thickness of the formed dentin barrier was different between the groups GI and GII (p < 0.05) and between groups GI and GIII (p < 0.01). On 60(th) day there was difference between GI and GIII (p < 0.01). It may be concluded that, LLLT 688 nm and 785 nm accelerated dentin barrier formation and consequently pulp repair process, with best results using infrared laser 785 nm. (c) 2009 by Astro Ltd. Published exclusively by WLLEY-VCH Verlag GmbH & Co. KGaA

Distribution of potential suitable hammers and transport of hammer tools and nuts by wild capuchin monkeys

Selection and transport of objects to use as tools at a distant site are considered to reflect planning. Ancestral humans transported tools and tool-making materials as well as food items. Wild chimpanzees also transport selected hammer tools and nuts to anvil sites. To date, we had no other examples of selection and transport of stone tools among wild nonhuman primates. Wild bearded capuchins (Cebus libidinosus) in Boa Vista (Piaui, Brazil) routinely crack open palm nuts and other physically well-protected foods on level surfaces (anvils) using stones (hammers) as percussive tools. Here we present indirect evidence, obtained by a transect census, that stones suitable for use as hammers are rare (study 1) and behavioral evidence of hammer transport by twelve capuchins (study 2). To crack palm nuts, adults transported heavier and harder stones than to crack other less resistant food items. These findings show that wild capuchin monkeys selectively transport stones of appropriate size and hardness to use as hammers, thus exhibiting, like chimpanzees and humans, planning in tool-use activities.

Frequency of Toxoplasma gondii antibodies in tufted capuchin monkeys (Cebus apella nigritus) from an ecological station in the State of São Paulo, Brazil

A toxoplasmose é uma das zoonoses mais difundidas no mundo, causada pelo Toxoplasma gondii, um protozoário parasita intracelular obrigatório. Uma alta porcentagem de animais apresenta anticorpos específicos causados por exposição prévia, levando a uma infecção crônica. Os felídeos são os hospedeiros definitivos e outros animais homeotérmicos, incluindo os primatas, são os hospedeiros intermediários. Este estudo objetivou determinar a prevalência da infecção por T. gondii em macacos-prego (Cebus apella nigritus) de vida livre da Estação Ecológica localizada na Mata de Santa Teresa, Ribeirão Preto, SP, Brasil. Anticorpos anti-T. gondii foram pesquisados pelo método de aglutinação direta modificada (MAT) em amostras de soro de 36 macacos-prego, utilizando-se o título oito como de corte. Dos animais estudados, 3/36 (8,33%; IC95% 3,0-21,9%) apresentaram anticorpos anti-T. gondii, todos com título 32. Nenhuma diferença significativa (P>0,05) foi observada com relação ao sexo (1/3 machos e 2/3 fêmeas), e à idade (1/3 jovens e 2/3 adultos). Assim, estes resultados demonstram alta prevalência de anticorpos anti-T. gondii em primatas no estado de São Paulo.

Exposure to rabies virus in a population of free-ranging capuchin monkeys (Cebus apella nigritus) in a fragmented, environmentally protected area in southeastern Brazil

The aim of this study is to assess the frequency of rabies antibodies in free-ranging capuchin monkeys (Cebus apella nigritus) in a fragmented, environmentally protected, rural area of southeastern Brazil. Thirty-six free-ranging monkeys were tested by the rapid fluorescent focus inhibition test for detection of antibodies against rabies virus. Four individuals (11.11 %) had neutralizing antibody titers a parts per thousand yen0.25 IU/mL, demonstrating rabies virus exposure.

Effects of cyclosporin, phenytoin, and nifedipine on the synthesis and degradation of gingival collagen in tufted capuchin monkeys (Cebus apella): Histochemical and MMP-1 and -2 and collagen I gene expression analyses

Background: The purpose of this experimental study was to evaluate the collagen fiber distribution histologically after phenytoin, cyclosporin, or nifedipine therapy and to correlate it with collagen I and matrix metalloproteinase (MMP)-1 and -2 gene expression levels.Methods: Gingival samples from the canine area were obtained from 12 male monkeys (Cebus apella). The mesial part of each sample was assessed by reverse transcription-polymerase chain reaction, whereas the distal part was processed histologically for picrosirius red and hematoxylin and eosin stainings, as well as for collagen IV immunostaining. One week after the first biopsy, the animals were assigned to three groups that received daily oral dosages of cyclosporin, phenytoin, or nifedipine for 120 days. Additional gingival samples were obtained on days 52 and 120 of treatment from two animals from each group on the opposite sides from the first biopsies.Results: Picrosirius red staining showed a predominance of mature collagen fibers in the control group. Conversely, there was an enlargement of areas occupied by immature collagen fibers in all groups at days 52 and 120, which was not uniform over each section. There was a general trend to lower levels of MMP-1 gene expression on day 52 and increased levels on day 120. Phenytoin led to increased levels of MMP-2 and collagen I gene expression on day 120, whereas the opposite was observed in the nifedipine group.Conclusion: Cyclosporin, phenytoin, and nifedipine led to phased and drug-related gene expression patterns, resulting in impaired collagen metabolism, despite the lack of prominent clinical signs.

Agricultural crops in the diet of bearded capuchin monkeys, Cebus libidinosus Spix (Primates: Cebidae), in forest fragments in southeast Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Morphometry and histochemistry of the semitendinosus muscle of tufted capuchin monkeys (Cebus apella Linnaeus, 1758)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)