Group fission in Moor macaques (Macaca maurus)

This is the first report of group fission in a wild group of Moor macaques (Macaca maurus) in South Sulawesi, Indonesia. The subject group, which has been observed on the basis of individual identification since 1988, showed no sign of fission in April 1999. In August 1999 the group had split in two , with the same number of mature females in each new group. For the most pa rt, mothers and their offspring joined the same groups. Dominance relations and association patterns established during the previous year among adult females did not strongly affect new group membership. The difference in fem ale reproductive state between the two branch groups was a prominent charac teristic. The m-male of the original group visited both groups at the first stage of group mission, even though otherwise the compositions of the new groups were stable. After the division, six adult males from outside the or iginal group immigrated exclusively into the group that did not contain the cr-male of the original group. Severe intergroup encounters occurred betwe en the two groups. We discuss the process of the fission and the resultant pattern in relation to the egalitarian dominance style among females, lack of seasonality in reproduction, and resemblance to one-male type social org anization.