Infanticide in wedge-capped capuchin monkeys, Cebus olivaceus

Three cases of infanticide are reported from a well-studied population of wedge-capped capuchin monkeys, Cebus olivaceus, located in the Venezuelan llanos. For each case, we examined the social context and the consequences to the reproductive success of the infanticidal male. In 1 case, the male probably killed his own son. In 2 cases, the male killed an unrelated animal. In all 3 cases, the female conceived in the following breeding season, but in only 1 case did the infanticidal male possibly enhance his own reproductive success. These data are interpreted in the light of current hypotheses for infanticide.     

Grooming,rank, and agonistic support in tufted capuchin monkeys

Studies investigating the relation between allogrooming and social rank in capuchin monkeys (genus Cebus) have yielded inconsistent results. In this study, we investigated the relation between grooming, agonistic support, aggression and social rank in a captive group of tufted capuchin monkeys (C. apella). Differently from most previous studies, we based our analyses on a relatively large database and studied a group with known genealogical relationships. Tufted capuchin females did not exchange grooming for rank‐related benefits such as agonistic support or reduced aggression. Coherently with this picture, they did not groom up the hierarchy and did not compete for accessing high‐ranking grooming partners. It is suggested that a small group size, coupled with a strong kin bias, may make the exchange of grooming for rank‐related benefits impossible or unprofitable, thus eliminating the advantages of grooming up the hierarchy. We provide several possible explanations for the heterogeneity of results across capuchin studies that have addressed similar questions. Am. J. Primatol. 71:101–105, 2009. © 2008 Wiley‐Liss, Inc.     

Endowment effect in capuchin monkeys

In humans, the capacity for economically rational choice is constrained by a variety of preference biases: humans evaluate gambles relative to arbitrary reference points; weigh losses heavier than equally sized gains; and demand a higher price for owned goods than for equally preferred goods that are not yet owned. To date, however, fewer studies have examined the origins of these biases. Here, we review previous work demonstrating that human economic biases such as loss aversion and reference dependence are shared with an ancestrally related New World primate, the capuchin monkey (Cebus apella). We then examine whether capuchins display an endowment effect in a token-trading task. We identified pairs of treats (fruit discs versus cereal chunks) that were equally preferred by each monkey. When given a chance to trade away their owned fruit discs to obtain the equally valued cereal chunks (or vice versa), however, monkeys required a far greater compensation than the equally preferred treat. We show that these effects are not due to transaction costs or timing issues. These data suggest that biased preferences rely on cognitive systems that are more evolutionarily ancient than previously thought-and that common evolutionary ancestry shared by humans and capuchins may account for the occurrence of the endowment effect in both species.     

Conceptual learning in capuchin monkeys

This paper reviews concept learning in Cebus monkeys, focussing on their ability to use the identity relation, oddity and natural concepts. Capuchins are similar to other primate genera in their use of these concepts. The extant data on learning in primates generally reflect historical concerns with general processes of learning. An alternative approach which considers the tasks the animal faces in its natural environment may be better suited to the discovery of species-unique characteristics of learning. This approach has not yet been applied to Cebus.     

True anting by the capuchin,Cebus capucinus

I observed capuchins (Cebus capucinus) putting ants (Camponotus sericeiventris) in their fur at Corcovado National Park, Costa Rica. The behavior was similar to “anting” in passerine birds. The literature on anting in birds is reviewed and compared with the relevant references on self-annointment behavior in mammals.     

Schistosoma haematobium: experimental infection in capuchin monkey, Cebus apella

South American capuchin monkeys (Cebus apella) have been included in a series of nonhuman primates under evaluation for their potential use as models in a study of the basic biology of Schistosoma haematobium. Emphasis has been given to involvement of the urogenital system, a prominent feature of infection in man. Preliminary observations on Cebus apella with moderate numbers of S. haematobium from Iran showed that there may be serious involvement of the urogenital system with development of pronounced hydronephrosis accompanied by pathobiological alteration of the urinary bladder, ureters, and kidneys. There were heavy deposits of parasite eggs in the major viscera.     

Collective decision-making in white-faced capuchin monkeys

In group-living animals, collective movements are a widespread phenomenon and occur through consensus decision. When one animal proposes a direction for group movement, the others decide to follow or not and hence take part in the decision-making process. This paper examines the temporal spread of individual responses after the departure of a first individual (the initiator) in a semi-free ranging group of white-faced capuchins (Cebus capucinus). We analysed 294 start attempts, 111 succeeding and 183 failing. Using a modelling approach, we have demonstrated that consensus decision-making for group movements is based on two complementary phenomena in this species: firstly, the joining together of group members thanks to a mimetic process; and secondly, a modulation of this phenomenon through the propensity of the initiator to give up (i.e. cancellation rate). This cancellation rate seems to be directly dependent upon the number of followers: the greater this number is, the lower the cancellation rate is seen to be. The coupling between joining and cancellation rates leads to a quorum: when three individuals join the initiator, the group collectively moves. If the initiator abandons the movement, this influences the joining behaviour of the other group members, which in return influences the initiator''s behaviour. This study demonstrates the synergy between the initiator''s behaviour and the self-organized mechanisms underlying group movements.     

Female-female social relationships in wild white-faced capuchin monkeys,Cebus capucinus

A single social group of wild white-faced capuchin monkeys was studied for a period of 26 months at Lomas Barbudal Biological Reserve, Costa Rica. A total of 604 hr of focal animal data was collected on six adult females in a group of 21 monkeys. Females could be ranked in a stable, linear dominance hierarchy. Adult females spent much more time in proximity to other adult females than to adult males. Females groomed other females twice as often as they groomed males, and about 55 times more often than males groomed males. Females tended to groom up the dominance hierarchy, and dyads with smaller rank distances groomed more often. Higher-ranking females nursed infants other than their own at lower rates than did lower-ranking females; however, females nursed infants of females ranked both above and below them. Although lower-ranking females were more likely than higher-ranking females to be the victims of aggression, higher-ranking females were not necessarily more aggressive than lower-ranking females. In 96% of female-female coalitions vs. a female, the victim was lower-ranking than both coalition partners; in the remaining 4%, the victim was intermediate in rank between the two coalition partners. Higher-ranking female-female dyads formed coalitions more often than did lower-ranking dyads. Those female-female dyads that groomed more frequently also formed coalitions more frequently. The patterning of social interactions indicates that Cebus capucinus at Lomas Barbudal are female bonded. © 1996 Wiley-Liss, Inc.     

Distributed leadership in semifree-ranging white-faced capuchin monkeys

We investigated the initiation of group movements in white-faced capuchin monkeys, Cebus capucinus, with the aim of determining whether a single individual with high dominance status consistently leads movements or whether leadership is distributed between group members. The group studied was reared in semifree-ranging conditions. A multivariate analysis followed by univariate analyses demonstrated that leadership was not concentrated on a single individual in this species. All individuals could initiate a collective movement. Nearly half of group members regularly succeeded in recruiting at least three followers. Although both sexes had similar rates of start attempts, females succeeded more frequently than males. We found no significant effect of the dominance status on the percentage of successful attempts. The use of a slow speed, looking back towards the other group members, or trills by the initiator heightened the likelihood of success in group movement initiation. An initiator starting from a core position in a clumped group was more successful than one starting from an edge position in a clumped group or from a dispersed group. Furthermore, the probability of successful start attempts was higher when the group remained stationary for a long period. Leadership in white-faced capuchins appears to be distributed between group members rather than exclusively concentrated on high-ranking individuals. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.      

Unilateral ovarian absence in two capuchin monkeys

Background Ovarian absence is a rare condition with congenital or traumatic origin. Methods Gross and microscopic examination of two capuchin monkeys were performed. Results Case 1 had absence of the right ovary and distal uterine tube, bilateral absence of fimbriae, and a rudimentary uterus. Case 2 had unilateral ovarian absence, but a functional contralateral ovary, and a normal uterus. Conclusions Unilateral ovarian absence was confirmed in two capuchin monkeys for the first time.     

Scream-embrace displays in wild black-horned capuchin monkeys

Reintroduction of capuchin monkeys (Cebus apella) into their social group in captivity can elicit sirena screams and embraces. Captive scream-embrace displays are male biased, and females never perform sirena screams. One hypothesis is that scream-embrace displays serve a tension-reduction or reconciliatory function between males with conflicting interests. Alternatively, these displays may function to maintain strong affiliative bonds between friendly male dyads. Scream and/or embrace displays in wild Brazilian black-horned capuchins were analyzed for social and ecological contexts, behavioral components, and individuals involved. Seventy-two displays were observed during the 199-day study period. Among the 66 displays for which both members could be identified by sex, there were 42 occurrences of male-male dyads, 17 of male-female dyads, and seven of female-female dyads. Scream-embrace dyads were male-male pairs significantly more often than expected from group membership, and the alpha male was the only male to engage in scream-embrace displays with females. Female-female pairs did embrace, but never emitted sirena screams. Displays most commonly occurred in "reunion" contexts, primarily the reuniting of subgroups after hours or days out of contact, but also after intergroup encounters, and across groups in "intergroup" displays. Displays were rare, but socially contagious, and subgroup reunions could elicit multiple displays in rapid succession. Although the occurrence of screams and embraces was positively correlated, both behaviors also occurred independently, and their functions may be different. Male sirena screams may be honest advertisements of united alliances, directed toward a third party, whereas the embrace may be a risky affiliative signal, directed primarily within the dyad.     

Food-exchange with humans in brown capuchin monkeys

To assess how brown capuchin monkeys (Cebus apella) delay gratification and maximize payoff, we carried out four experiments in which six subjects could exchange food pieces with a human experimenter. The pieces differed either in quality or quantity. In qualitative exchanges, all subjects gave a piece of food to receive another of higher value. When the difference of value between the rewards to be returned and those expected was higher, subjects performed better. Only two subjects refrained from nibbling the piece of food before returning it. All subjects performed two or three qualitative exchanges in succession to obtain a given reward. In quantitative exchanges, three subjects returned a food item to obtain a bigger one, but two of them nibbled the item before returning it. Individual differences were marked. Subjects had some difficulties when the food to be returned was similar or equal in quality to that expected.     

Response to changes in food palatability in tufted capuchin monkeys, Cebus apella

Palatability of plant foods may change over time in relation to the concentration of toxic secondary metabolites. We investigated the behavioural response of capuchin monkeys to this type of change and assessed the influence of social conditions. Twenty-seven tufted capuchin monkeys were presented in Social or Individual conditions with a familiar palatable food (phase 1), with the same familiar food to which pepper had been added, making it unpalatable (phase 2), and with the same familiar palatable food of phase 1 (phase 3). Five sessions were carried out in each phase. The capuchins adapted quickly to the change in food palatability by reducing (phase 2) and increasing (phase 3) the amounts of food eaten. The unpalatable food prompted an increase in olfactory exploration and in food processing. The experimental conditions (Social versus Individual) did not influence consumption, or any of the other behaviours. In addition, capuchins were more often near subjects with food in phases 2 and 3 in which palatability changed than in phase 1. These findings show that capuchins readily adjust to changes in flavour and palatability of a familiar food and that sudden unpalatability has no carry-over effects. Therefore, capuchins behave differently towards a familiar food whose palatability has changed than they do towards novel foods. Copyright 2000 The Association for the Study of Animal Behaviour.     

Hand preference in capuchin monkeys varies with age

The purpose of this research was to examine the influence of age on hand preference in capuchin monkeys (Cebus apella). Twenty-two capuchins, aged 6 months to 30 years, were presented with a task that involved reaching for food and a task that involved using sponging tools to absorb juice. Adults exhibited a greater percentage of right-handed actions in each task than did immature subjects. Adults also exhibited a stronger lateral bias than did immature subjects in the sponging task. These results are consistent with hypotheses: a) adult capuchin monkeys are biased toward use of their right hand for reaching; b) adult capuchins exhibit a greater incidence of right-hand preference than do immature capuchins; and c) primates exhibit age-related differences in the strength and direction of hand preference in tasks that involve the use of tools.     

Three-dimensional kinematics of capuchin monkey bipedalism

Capuchin monkeys are known to use bipedalism when transporting food items and tools. The bipedal gait of two capuchin monkeys in the laboratory was studied with three-dimensional kinematics. Capuchins progress bipedally with a bent-hip, bent-knee gait. The knee collapses into flexion during stance and the hip drops in height. The knee is also highly flexed during swing to allow the foot which is plantarflexed to clear the ground. The forefoot makes first contact at touchdown. Stride frequency is high, and stride length and limb excursion low. Hind limb retraction is limited, presumably to reduce the pitch moment of the forward-leaning trunk. Unlike human bipedalism, the bipedal gait of capuchins is not a vaulting gait, and energy recovery from pendulum-like exchanges is unlikely. It extends into speeds at which humans and other animals run, but without a human-like gait transition. In this respect it resembles avian bipedal gaits. It remains to be tested whether energy is recovered through cyclic elastic storage and release as in bipedal birds at higher speeds. Capuchin bipedalism has many features in common with the facultative bipedalism of other primates which is further evidence for restrictions on a fully upright striding gait in primates that transition to bipedalism. It differs from the facultative bipedalism of other primates in the lack of an extended double-support phase and short aerial phases at higher speeds that make it a run by kinematic definition. This demonstrates that facultative bipedalism of quadrupedal primates need not necessarily be a walking gait.     

Primary structure of adult hemoglobin of white-throated capuchin, Cebus capucinus

The alpha and beta chains of White-Throated Capuchin (Cebus capucinus) hemoglobin were separated and digested by trypsin. The tryptic peptides were isolated and sequenced by conventional methods. The peptides in each chain were aligned by the homology of their sequences with those of human adult hemoglobin. The primary structures thus deduced are compared with those of other primate hemoglobins, and we discuss the molecular evolution of hemoglobins, in particular the rate of evolution in New World monkey hemoglobins.     

Unconstrained 3D-kinematics of prehension in five primates: Lemur,capuchin, gorilla,chimpanzee, human

Primates are known for their use of the hand in many activities including food grasping. Yet, most studies concentrate on the type of grip used. Moreover, kinematic studies remain limited to a few investigations of the distal elements in constrained conditions in humans and macaques. In order to improve our understanding of the prehension movement in primates, we analyse here the behavioural strategies (e.g., types of grip, body postures) as well as the 3D kinematics of the whole forelimb and the trunk during the prehension of small static food items in five primate species in unconstrained conditions. All species preferred the quadrupedal posture except lemurs, which used a typical crouched posture. Grasp type differed among species, with smaller animals (capuchins and lemurs) using a whole-hand grip and larger animals (humans, gorillas, chimpanzees) using predominantly a precision grip. Larger animals had lower relative wrist velocities and spent a larger proportion of the movement decelerating. Humans grasped food items with planar motions involving small joint rotations, more similar to the smaller animals than to gorillas and chimpanzees, which used greater rotations of both the shoulder and forearm. In conclusion, the features characterising human food prehension are present in other primates, yet differences exist in joint motions. These results provide a good basis to suggest hypotheses concerning the factors involved in driving the evolution of grasping abilities in primates.