Abstract
Muriquis (Brachyteles arachnoides) are unusual among polygamous primates in the nonaggressive, egalitarian relationships that exist among group members. Yet, despite their relative freedom to express strong preferences in their choice of mates, 18 sexually active females and 10 sexually active males routinely copulated with multiple partners during a 60-month period from July 1990 to June 1995 at the Estação Biologica de Caratinga on Fazenda Montes Claros, Minas Gerais, Brazil. Females with different reproductive and social histories differed in the ways they expressed their promiscuity. The number of different partners was positively related to copulation frequencies for long-term female residents, but not for recent female immigrants or mature or young males. Mother-son matings and matings between recent female immigrants and males from their natal group were rare. Preferential mating occurred between recent female immigrants and young males, while experienced long-term female residents tended to copulate more frequently with mature males. Prior reproductive experience appears to be a less important determinant of muriqui mating patterns than the constraints imposed by avoiding close inbreeding and the preferences exhibited by close social associates.