Histochemistry profile of the biceps brachii muscle fibres of capuchin monkeys (Cebus apella, Linnaeus, 1758)

A general analysis of the behaviour of "Cebus" shows that when this primate moves position to feed or perform another activity, it presents different ways of locomotion. This information shows that the brachial biceps muscle of this animal is frequently used in their locomotion activities, but it should also be remembered that this muscle is also used for other development activities like hiding, searching for objects, searching out in the woods, and digging in the soil. Considering the above, it was decided to research the histoenzimologic characteristics of the brachial biceps muscle to observe whether it is better adpted to postural or phasic function. To that end, samples were taken from the superficial and deep regions, the inserts proximal (medial and lateral) and distal brachial biceps six capuchin monkeys male and adult, which were subjected to the reactions of m-ATPase, NADH-Tr. Based on the results of these reactions fibres were classified as in Fast Twitch Glycolitic (FG), Fast Twitch Oxidative Glycolitic (FOG) and Slow Twitc (SO). In general, the results, considering the muscle as a whole, show a trend of frequency FOG>FG>SO. The data on the frequency were studied on three superficial regions FOG=FG>SO; the deep regions of the inserts proximal FOG=FG=SO and inserting the distal FOG>FG=SO. In conclusion, the biceps brachii of the capuchin monkey is well adapted for both postural and phasic activities.

Temporal changes in calcium-binding proteins in the medial geniculate nucleus of the monkey Sapajus apella

The subdivisions of the medial geniculate complex can be distinguished based on the immunostaining of calcium-binding proteins and by the properties of the neurons within each subdivision. The possibility of changes in neurochemistry in this and other central auditory areas are important aspects to understand the basis that contributing to functional variations determined by environmental cycles or the animal's cycles of activity and rest. This study investigated, for the first time, day/night differences in the amounts of parvalbumin-, calretinin- and calbindin-containing neurons in the thalamic auditory center of a non-human primate, Sapajus apella. The immunoreactivity of the PV-IR, CB-IR and CR-IR neurons demonstrated different distribution patterns among the subdivisions of the medial geniculate. Moreover, a high number of CB- and CR-IR neurons were found during day, whereas PV-IR was predominant at night. We conclude that in addition to the chemical heterogeneity of the medial geniculate nucleus with respect to the expression of calcium-binding proteins, expression also varied relative to periods of light and darkness, which may be important for a possible functional adaptation of central auditory areas to environmental changes and thus ensure the survival and development of several related functions.

Spatial reference of black capuchin monkeys in Brazilian Atlantic Forest: egocentric or allocentric?

Wild primates occupy large home ranges and travel long distances to reach goals. However, how primates are able to remember goal locations and travel efficiently is unclear. Few studies present consistent results regarding what reference system primates use to navigate, and what kind of spatial information they recognize. We analysed the pattern of navigation of one wild group of black capuchin monkeys, Cebus nigritus, at Atlantic Forest for 100 days in Carlos Botelho State Park (PECB), Brazil. We tested predictions based on the alternative hypotheses that black capuchin monkeys navigate using a sequence of landmarks as an egocentric reference system or an allocentric reference system, or both, depending on availability of food resources. The group location was recorded using a GPS device collecting coordinates at 5 min intervals, and route maps were generated using ArcView v9.3.1. The study group travelled through habitual routes during less than 30% of our study sample, and revisited resources from different starting points, using different paths and routes, even when prominent landmarks near feeding locations were not visible. The study group used habitual routes more frequently when high-quality foods were scarce, and navigated using different paths when revisiting food sources. Results support the hypothesis that black capuchin monkeys at PECB navigate using both egocentric and allocentric systems of reference, depending on the quality and distribution of the food resource they find. (C) 2010 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Cone photopigment variations in Cebus apella monkeys evidenced by electroretinogram measurements and genetic analysis

We investigated the color vision pattern in Cebus apella monkeys by means of electroretinogram measurements (ERG) and genetic analysis. Based on ERG we could discriminate among three types of dichromatic males. Among females, this classification is more complex and requires additional genetic analysis. We found five among 10 possible different phenotypes, two trichromats and three dichromats. We also found that Cebus present a new allele with spectral peak near 552 nm, with the amino acid combination SFT at positions 180, 277 and 285 of the opsin gene, in addition to the previously described SYT, AFT and AFA alleles. (C) 2009 Elsevier Ltd. All rights reserved.

Ontogeny of manipulative behavior and nut-cracking in young tufted capuchin monkeys (Cebus apella): a Perception-action perspective

How do capuchin monkeys learn to use stones to crack open nuts? Perception-action theory posits that individuals explore producing varying spatial and force relations among objects and surfaces, thereby learning about affordances of such relations and how to produce them. Such learning supports the discovery of tool use. We present longitudinal developmental data from semifree-ranging tufted capuchin monkeys (Cebus apella) to evaluate predictions arising from Perception-action theory linking manipulative development and the onset of tool-using. Percussive actions bringing an object into contact with a surface appeared within the first year of life. Most infants readily struck nuts and other objects against stones or other surfaces from 6 months of age, but percussive actions alone were not sufficient to produce nut-cracking sequences. Placing the nut on the anvil surface and then releasing it, so that it could be struck with a stone, was the last element necessary for nut-cracking to appear in capuchins. Young chimpanzees may face a different challenge in learning to crack nuts: they readily place objects on surfaces and release them, but rarely vigorously strike objects against surfaces or other objects. Thus the challenges facing the two species in developing the same behavior (nut-cracking using a stone hammer and an anvil) may be quite different. Capuchins must inhibit a strong bias to hold nuts so that they can release them; chimpanzees must generate a percussive action rather than a gentle placing action. Generating the right actions may be as challenging as achieving the right sequence of actions in both species. Our analysis suggests a new direction for studies of social influence on young primates learning sequences of actions involving manipulation of objects in relation to surfaces.

Food Competition in a Semi-Free-Ranging Cebus apella Group

The competitive regime faced by individuals is fundamental to modelling the evolution of social organization. In this paper, we assess the relative importance of contest and scramble food competition on the social dynamics of a provisioned semi-free-ranging Cebus apella group (n=18). Individuals competed directly for provisioned and clumped foods. Effects of indirect competition were apparent with individuals foraging in different areas and with increased group dispersion during periods of low food abundance. We suggest that both forms of competition can act simultaneously and to some extent synergistically in their influence on social dynamics; the combination of social and ecological opportunities for competition and how those opportunities are exploited both influence the nature of the relationships within social groups of primates and underlie the evolved social structure. Copyright (c) 2008 S. Karger AG, Basel

ELECTROCARDIOGRAPHIC PARAMETERS OF CAPTIVE TUFTED CAPUCHINS (CEBUS APELLA) UNDER CHEMICAL IMMOBILIZATION

This study presents the electrocardiogram findings from 97 captive tufted capuchin monkeys (Cebus apella) at the Sao Paulo Zoo (Sao Paulo, Brazil) while under ketamine anesthesia. The results did not differ greatly from data of domestic carnivores or other studied primate species. The most common rhythm recorded was normal sinus rhythm, followed by normal sinus rhythm with wandering pacemaker. Electrical axis varied from 0 degrees to -150 degrees but was most commonly between +60 degrees and +90 degrees. QRS complexes were predominantly positive in leads DI, DII, DIII, and AVF. These findings allow for the recognition of abnormal rhythms in these primate species and can contribute to future investigations into the cardiovascular diseases routinely diagnosed in primates and humans.

Anatomical and radiographic appearance of the capuchin monkey thoracic cavity (Cebus apella)

The capuchin monkey is widespread both north and south of the Legal Amazon and in the Brazilian cerrado. Ten clinically healthy capuchin monkeys were submitted to an anatomical and radiographic study of their thoracic cavities. The radiographic evaluation allowed the description of biometric values associated with the cardiac silhouette and thoracic structures. Application of the VHS (vertebral heart size) method showed positive correlation (P<0.05) with depth of the thoracic cavity, as well as between the body length of vertebrae T 3, T 4, T 5 and T 6 and the cardiac length and width. The lung fields showed a diffuse interstitial pattern, more visible in the caudal lung lobes and a bronchial pattern in the middle and cranial lung lobes. The radiographic examination allowed preliminary inferences to be made concerning the syntopy of the thoracic structures and modifiication of the pulmonary patterns and cardiac anatomy for the capuchin monkey.

Transport of Functionally Appropriate Tools by Capuchin Monkeys (Cebus apella)

Capuchin monkeys are notable among New World monkeys for their widespread use of tools. They use both hammer tools and insertion tools in the wild to acquire food that would be unobtainable otherwise. Evidence indicates that capuchins transport stones to anvil sites and use the most functionally efficient stones to crack nuts. We investigated capuchins’ assessment of functionality by testing their ability to select a tool that was appropriate for two different tool-use tasks: A stone for a hammer task and a stick for an insertion task. To select the appropriate tools, the monkeys investigated a baited tool-use apparatus (insertion or hammer), traveled to a location in their enclosure where they could no longer see the apparatus, made a selection between two tools (stick or stone), and then could transport the tool back to the apparatus to obtain a walnut. Four capuchins were first trained to select and use the appropriate tool for each apparatus. After training, they were then tested by allowing them to view a baited apparatus and then travel to a location 8 m distant where they could select a tool while out of view of the apparatus. All four monkeys chose the correct tool significantly more than expected and transported the tools back to the apparatus. Results confirm capuchins’ propensity for transporting tools, demonstrate their capacity to select the functionally appropriate tool for two different tool-use tasks, and indicate that they can retain the memory of the correct choice during a travel time of several seconds.

Audience Effects in COgnitive Task Performance in Capuchin Monkeys (Cebus apella)

Primates as a taxonomic Order have the largest brains corrected for body size in the animal kingdom. These large brains have allowed primates to evolve the capacity to demonstrate advanced cognitive processes across a wide array of abilities. Nonhuman primates are particularly adept at social learning, defined as the modification of behavior by observing the actions of others. Additionally, primates often exploit resources differently depending on their social context. In this study, capuchin monkeys (Cebus apella) were tested on a cognitive task in three social contexts to determine if social context influenced their performance on the task. The three social contexts included: alone, having a dominant individual in an adjacent compartment, and having a subordinate individual in the adjacent compartment. The benefits to this design were thatthe social context was the only variable influencing performance, whereas in previous studies investigating audience effects other animals could physically and directly influence a subject's performance in an open testing situation. Based on past studies, Ipredicted that the presence of a dominant individual would reduce cognitive task performance compared to the other conditions. The cognitive test used was a match-tosample discrimination task in which animals matched combinations of eight geometric shapes. Animals were trained on this task in an isolated context until they reached a baseline level of proficiency and were then tested in the three social contexts in a random order multiple times. Two subjects (Mt and Dv) have successfully completed trials under all conditions. Results indicated that there were no significant difference in taskperformance across the three conditions (Dv x^2 (1) = 0.42, p=0.58; Mt x^2 (1) = 0.02, p=0.88). In all conditions, subjects performed significantly above chance (i.e., 39/60 trials determined by a binomial distribution). Results are contrary to previous studies thatreport low status monkeys 'play dumb' when testing in a mixed social context, possibly because other studies did not account for aggressive interference by dominants while testing. Results of this study suggest that the mere presence of a dominant individualdoes not necessarily affect performance on a cognitive task, but rather the imminence of physical aggression is the most important factor influencing testing in a social context.

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.

Use Of Conspecific Gestural Cues To Solve An Object-Choice Task In Tufted Capuchin Monkeys (Cebus Apella)

Capuchin monkeys, Cebus sp., utilize a wide array of gestural displays in the wild, including facial displays such as lip-smacking and bare-teeth displays. In captivity, they have been shown to respond to the head orientation of humans, show sensitivity to human attentional states, as well as follow human gazes behind barriers. In this study, I investigated whether tufted capuchin monkeys (Cebus apella) would attend to and utilize the gestural cues of a conspecific to obtain a hidden reward. Two capuchins faced each other in separate compartments of an apparatus with an open field in between. The open field contained two cups with holes on one side such that only one monkey, a so-called cuing monkey, could see the reward inside one of the cups. I then moved the cups toward the other signal-receiving monkey and assessed whether it would utilize untrained cues provided by the cuing monkey to select the cup containing the reward. Two of four female capuchin monkeys learned to select the cup containing the reward significantly more often than chance. Neither of these two monkeys performed over chance spontaneously, however, and the other two monkeys never performed above chance despite many blocks of trials. Successful choices by two monkeys to obtain hidden rewards provided experimental evidence that capuchin monkeys attend to and utilize the gestural cues of conspecifics.

The Expression Of Motor Planning In Squirrel Monkeys (Saimiri sciureus) And Brown Capuchins (Cebus apella)

Multiple recent studies provide evidence that both human and nonhuman primates possess motor planning abilities. I tested for the demonstration of motor planning in two previously untested primate species through two experiments. In the first experiment, I compared the extent to which squirrel monkeys (Saimiri sciureus) and brown capuchins (Cebus apella) plan their movements in a grasping task. Individuals were presented with an inverted cup that required being turned and held upright in order to extract a food reward from the inside of the cup. This task was most efficiently solved by using an initially awkward inverted grasp that affords a comfortable hand and arm orientation at the end of the movement (known as end-state comfort). While certain individuals from both species exhibited end-state comfort, many of the capuchins never demonstrated this type of motor planning. Furthermore, the squirrel monkeys used the efficient grasp significantly more than the capuchins. In the second experiment, I presented the capuchins with another grasping task to test if they would express motor planning abilities in a different context. Here, the capuchins were offered a dowel that was baited on either the left or right end. A radial grasp with the thumb pointing towards the baited end was considered to be the most efficient grasp because it afforded a comfortable final position. The capuchins switched hands and used an overhand radial grasp on the dowel significantly more often than not, thus demonstrating motor planning in this task. The grasps typically utilized by these two closely related species differ considerably in that capuchins are capable of exercising precision grips, whereas squirrel monkeys are limited to whole-handed power grips. Moreover, unlike capuchins, squirrel monkeys are not particularly dexterous nor are they capable of precise manipulative actions. It is therefore more beneficial for squirrel monkeys to plan their movements efficiently because they are less capable of compensating for inappropriate initial grasps. Due to the appreciable variability in the expression of motor planning skills across species, I proposed that morphological constraints might explain the observed discrepancies in movement planning among different primate species.

Brown Capuchins (Cebus apella) Exhibit Self-Control on a Delay of Gratification Food Exchange Task When Food Options Differ Qualitatively

Self-control allows an individual to obtain a more preferred outcome by forgoing an immediate interest. Self-control is an advanced cognitive process because it involves the ability to weigh the costs and benefits of impulsive versus restrained behavior, determine the consequences of such behavior, and make decisions based on the most advantageous course of action. Self-control has been thoroughly explored in Old World primates, but less so in New World monkeys. There are many ways to test self-control abilities in non-human primates, including exchange tasks in which an animal must forgo an immediate, less preferred reward to receive a delayed, more preferred reward. I examined the self-control abilities of six capuchin monkeys using a task in which a monkey was given a less preferred food and was required to wait a delay interval to trade the fully intact less preferred food for a qualitatively higher, more preferred food. Partially eaten pieces of the less preferred food were not rewarded, and delay intervals increased on an individual basis based on performance. All six monkeys were successful in inhibiting impulsivity and trading a less preferred food for a more preferred food at the end of a delay interval. The maximum duration each subject postponed gratification instead of responding impulsively was considered their delay tolerance. This study was the first to show that monkeys could inhibit impulsivity in a delay of gratification food exchange task in which the immediate and delayed food options differed qualitatively and a partially eaten less preferred food was not rewarded with the more preferred food at the end of a delay interval. These results show that New World monkeys possess advanced cognitive abilities similar to those of Old World primates.