Abstract
Benefits and costs of group living may not be equally distributed among all group members when they are organized in dominance hierarchies. In capuchin monkeys, higher-ranking individuals often have privileged access to food sources and reproductive partners. Other group members, particularly females, can benefit from proximity with the alpha male, gaining privileged access to the resources and also protection in the case of conflicts. In this study, a group with 17 individuals was observed for seven months and during this time data on activities and interindividual distances up to 10 meters were collected using animal-focal sampling method. Data were analysed through minimum spanning trees of interindividual distances and shortest directed trees of grooming and agonistic behavior. Dominance hierarchy in capuchins is generally considered stable, without reversions. However, during this study we observed a hierarchy reversal. It involved a period of increase in frequencies of agonistic behavior, caused mainly by conflict among females, and during this time the dominant female was threatened and sometimes attacked by a coalition of three other females. After this period the dominant female moved away from the group centre and the former beta female clearly took over the alpha position. The reversal was probably caused by transition to adulthood by one female and low grooming rates directed to the alpha male and adult females by the former alpha female.
Highlights
1. she had not established strong bonds with the alpha male and the other females, as indicated by grooming relationships (e.g. Janson, 1990, di Bitteti, 1997, Parr et al 1997, Ferreira & Izar, in prep.)
2. she was initially supported by an adult male, Eli, who latter left the group, and so she lost her main supporter
During the period of rank reversal, high frequencies of agonism were accompanied by high rates of grooming, reinforcing the hypothesis of grooming as a reassuring behavior (Dunbar, 1991)
Summary
1. she had not established strong bonds with the alpha male and the other females, as indicated by grooming relationships (e.g. Janson, 1990, di Bitteti, 1997, Parr et al 1997, Ferreira & Izar, in prep.). Only Janete had a direct dominance relationship with Ana (Aa). On the period before the fights and the reversion, the alpha male (Bq) was the centre of the group, with almost all females directly connected to him; the exception was Ana (Aa), who was connected to Bq through her daughter Ada (Ad). Janete (Jn), became a low ranking female, being directly dominated by Física (Fs), Ana (Aa) and Cisca (Cc).
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