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.     

Food-washing among wedge-capped capuchin monkeys (cebus olivaceus)

Four cases of spontaneous food-washing and others novel behaviours are reported forCebus olivaceus. The individuals observed are either wild or captive born members of wedgecapped capuchin monkey groups from two zoological parks in Caracas, Venezuela. Those cases seem to represent the resolution of particular and circumstantial problems, rather than indication of learning, transmission or imitation processes.     

The function of food-associated calls in white-faced capuchin monkeys, Cebus capucinus, from the perspective of the signaller

In many species, call recipients respond to food-associated calls by approaching the signaller. For this reason, most studies of food-associated calls focus on the benefits to a signaller of attracting a particular audience to a food source. Although call recipients respond as if they have been informed about the location of a food source, it is not necessarily the case that the primary function of food-associated calls is to inform others. I combined naturalistic observations and food placement experiments to investigate the environmental and social influences on call production in white-faced capuchin monkeys to assess other possible functions of food-associated calls. Individuals did not call under the circumstances predicted by an information-sharing hypothesis. The quantity of food and the age-sex composition of the audience did not influence call production, but food type did. Individuals produced more food-associated calls when they discovered fruit compared with insects or eggs. Results of observations of social interactions after food discovery indicated another possible function of food-associated calls. Individuals who called when they discovered food were less likely to be approached by others who were in visual contact than individuals who remained silent. Individuals who did not call when they discovered food were more likely to call subsequently if a higher-ranking, as opposed to a lower-ranking, animal approached them. Furthermore, individuals who called when approached by higher-ranking animals were less likely to receive aggression than individuals who did not call. Therefore, food-associated calls may function to announce food ownership, thereby decreasing aggression from other individuals.     

Social diffusion of novel foraging methods in brown capuchin monkeys (Cebus apella)

It has been reported that wild capuchin monkeys exhibit several group-specific behavioural traditions. By contrast, experiments have found little evidence for the social learning assumed necessary to support such traditions. The present study used a diffusion chain paradigm to investigate whether a novel foraging task could be observationally learned by capuchins (Cebus apella) and then transmitted along a chain of individuals. We used a two-action paradigm to control for independent learning. Either of two methods (lift or slide) could be used to open the door of a foraging apparatus to retrieve food. Two chains were tested (N1=4; N2=5), each beginning with an experimenter-trained model who demonstrated to a partner its group-specific method for opening the foraging apparatus. After the demonstration, if the observer was able to open the apparatus 20 times by either method, then it became the demonstrator for a new subject, thus simulating the spread of a foraging tradition among 'generations' of group members. Each method was transmitted along these respective chains with high fidelity, echoing similar results presently available only for chimpanzees and children. These results provide the first clear evidence for faithful diffusion of alternative foraging methods in monkeys, consistent with claims for capuchin traditions in the wild.     

Look before leaping: foraging selectivity of capuchin monkeys on acacia trees in Costa Rica

Acacia trees in Costa Rica have an obligate mutualism with three species of Pseudomyrmex ants, which vigorously defend their host tree from insect and mammalian herbivores. Depending on the size and species of ant colony, individual acacia trees may be differentially protected. For animals able to discern between weakly and highly aggressive ant colonies, costs of ant stings from less active colonies might be offset by nutritional value acquired from feeding on acacia fruit or ant larvae in swollen thorns. We examined foraging selectivity of capuchin monkeys on acacia trees in Santa Rosa National Park, Costa Rica. We measured four characteristics of the acacia trees from which capuchins fed and of acacias immediately adjacent to those in which the monkeys fed: diameter at breast height (DBH), accessibility, species of closest tree and ant species present. We found that capuchins prefer to forage in acacias that are large and accessible. We also made two measurements of ant colony activity on each tree, one before and one after disturbing the ant colony. We found that the three species of mutualistic ants differ in baseline activity levels and that mutualistic ants are more active than non-mutualistic ant species found in acacia trees. We also found that capuchins foraged more frequently in trees colonized by non-mutualistic ants, but the explanatory value (r ²) of this model was low. Furthermore, monkeys did not discriminate between acacias on the basis of baseline ant activity or the ant colony’s response to disturbance. We conclude that these monkeys select acacia trees in which to forage based on characteristics of the trees rather than the ants. In addition, our study suggests that white-faced capuchins act as predators on the acacia ants but they probably benefit the dispersal and reproductive success of acacia trees. Capuchins may in fact function as an additional mutualistic partner for acacia trees via seed dispersal, but they must overcome the ants’ defense of the trees to do so.     

Increasing foraging opportunities for a group of captive capuchin monkeys (Cebus capucinus)

Capuchin monkeys often employ complex manipulative skills while recovering food items. Five captive Cebus capucinus were presented with two identical feeders that required the monkeys to lift up flaps, search through hay, and perform coordinated hand movements in order to obtain food items. The intent of this study was not to merely increase the amount of time the animals spent feeding, but to provide opportunities for greater expression of species-typical foraging behavior. In addition to their regular diet, figs and various types of unshelled nuts were placed inside the feeders. The monkeys avidly searched for and removed food from the feeders, displaying a wide variety of manipulative abilities. The amount of time the animals spent foraging significantly increased (p less than 0.05) whereas the amount of time the animals spent locomoting and resting significantly decreased (p less than 0.05) when the feeders were available. The feeders were portable, durable, easy to clean, and relatively inexpensive.     

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.     

Parasitic nursing behavior in the wedge-capped capuchin monkey (Cebus olivaceus)

Juvenile and adult females in two wild groups of wedge-capped capuchin monkeys (Cebus olivaceus) were observed nursing from other adult females. The context of the interactions varied with participants but always involved a higher-ranking female nursing from a lower-ranking female. This behavior appears to be an example of an exploitative interaction in which the suckling female benefits at the expense of the nursing female.     

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.     

Time budget and foraging strategies of two provisioned groups of tufted capuchin monkeys,Sapajus libidinosus,in a small,seasonal urban forest fragment

Primates - Studies of urban monkeys provide important insights into the behavioral flexibility of primate species. We studied two provisioned groups of capuchin monkeys that inhabit a small forest...     

Piagetian object-permanence in Cebus capucinus,Lagothrica flavicauda and Pan troglodytes

Object-permanence was studied with one chimpanzee (Pan troglodytes) and two New World monkeys (Lagothrica flavicauda and Cebus capucinus). The chimpanzee and the capucinus attained stage VI, while Lagothrica reached stage Va. The data show that tests of object-permanence are suitable for comparison among species. This study also attempts to propose an experimental scheme that could allow for a more valid comparison among species. Use of an operant conditioning procedure is suggested and discussed.