RESUMO
Socioecological models predict that disputes between primate groups will be more intense than those within groups, given that the systematic loss of contests over a given resource will restrict the access of all of the members of that group to that resource. Higher levels of aggression are also expected for provisioned resources that have a more lucrative cost:benefit ratio. The levels of aggression in and between two free-ranging tufted capuchin monkey (Sapajus libidinosus) groups in the context of daily provisioning with bananas were evaluated. The aim of a complementary analysis was to identify possible predictors of the frequency of disputes at the site of the provisioned resource. The disputes were recorded using all-events sampling, while the social behaviour of the study groups was recorded by instantaneous scan sampling. The data were analysed using t-test, Mann-Whitney's U, and generalised linear modelling. Between-group disputes were no more intense than within-group events, and did not involve more individuals, or more adult females. The frequency of disputes increased as the number of individuals eating bananas increased. No evidence was found that disputes between groups were any more intense than those within groups. Dominance patterns may have affected these findings, by mediating intergroup disputes. An increase in the number of competitors affected the frequency of disputes at the site of the provisioned resource.
Assuntos
Cebinae , Dissidências e Disputas , Feminino , Animais , Comportamento Social , Agressão , Sapajus apella , CebusRESUMO
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 fragment in the city of Goiânia, Brazil. One of the groups was dominant and had priority of access to both native and provisioned resources. Anthropic resources were available in two relatively small areas within this forest, but varied in their quality. We hypothesized that intergroup dominance and the seasonality of native resources would have different impacts on the foraging strategies and use of space by the two study groups. Data on the location of the members of the two groups, their behavior, and consumption of different food items were collected during five dry season and five rainy season months. The members of the dominant group spent more time in the provisioned area where anthropic food was less costly to obtain and consumed more provisioned fruit and vegetables than the members of the subordinate group. The differences between groups were exacerbated during the dry season, when sources of native fruit were less abundant. The results of the present study illustrate how capuchins may respond to the variation in proximate factors, such as intergroup dominance and seasonality. These factors were determinants to the variation in the diet and the use of space observed between the two study groups.
Assuntos
Comportamento Alimentar , Sapajus apella , Animais , Cebinae , Cebus , Florestas , Frutas , Estações do AnoRESUMO
Asymmetries in resource-holding potential between opposing groups frequently determine outcomes of intergroup contests. Since both numerical superiority and high intergroup dominance rank may confer competitive advantages, group members should benefit from assessing the relative strength of rivals prior to engaging in defensive displays. However, differences in individual assessment may emerge when cost-benefit trade-offs differ among group members. We examine the influence of numerical superiority and intergroup dominance relationships on individual participation in intergroup encounters in black howler monkeys (Alouatta pigra) and tufted capuchin monkeys (Sapajus nigritus). Black howlers responded with longer vocal displays during encounters with neighbours with an equal number of resident males, while tufted capuchins increased their participation with increasing relative male group size. Within each species, males and females responded similarly to varying numerical odds, suggesting that despite pay-off asymmetries between males and females, both sexes were similarly influenced by numerical asymmetries in deciding to participate in collective group defence. Whereas the outcome of contests among tufted capuchins was determined by relative male group size, reflected in a pronounced intergroup dominance hierarchy, the absence of dominance relationships among black howler groups may have provoked prolonged vocal displays in order to assess rival groups with matching competitive abilities.