Line, S. W., Morgan, K. N., Markowitz H. 1991. Pair formation among adult female long-tailed macaques (Macaca fascicularis). American Journal of Primatology 24, 115-116 (Abstract).

Most social units were formed by choosing partners at random and removing a partition between adjacent cages. Thirteen of 15 pairs, and [only] 1 of 4 trios, remained compatible for 4 months or longer following resocialization. Two additional successful pairs were formed from the members of unsuccessful trios. Grooming increased significantly in the first 3 months following resocialization. Abnormal behaviors including pacing, stereotypic actions, bizarre postures, and self-abuse did not change significantly, however.