Dominance and Reciprocity in the Grooming Relationships of Female Long-Tailed Macaques (Macaca fascicularis) in Indonesia

It has been long known that females form the stable core of macaque societies (Bernstein and Sharpe 1966; Vandenbergh 1967; Drickamer 1976). They have strong relational ties and develop lifelong relationships with other females in their groups, thus they are considered to be female-bonded (Wrangham 1980). They have particularly close relationships with kin that are characterized by high levels of affiliation (Sade 1965; Drickamer 1976; Kurland 1977; Chapais 1983; Gouzoules and Gouzoules 1987; Kapsalis 2004; Silk 2006). This pattern results because females are philopatric and remain in their natal group for life, while males disperse and emigrate from their natal groups shortly after reaching sexual maturity (van Noordwijk and van Schaik 1985; Pusey and Packer 1987). Since female family lineages generally remain in the same location across generations, macaque groups are based on a cross-generational matrilineal social structure of closely related females. Macaque groups are typically multi-male/multi-female, and consist of several female matrilines (i.e., families), their young, and unrelated immigrant adult males that have migrated from neighboring communities and maintain transient relationships with the females until they emigrate again (de Ruiter and Geffen 1998). Due to the matrilineal structure of macaque societies, females must maintain long-term affiliative relationships with other females in their group. Consequently female cercopithecine primates, such as macaques, are equipped with adaptations for developing and maintaining close female-female bonds because females that can develop larger relationship networks tend to have higher fitness (Silk et al. 2003; Silk 2007).