Polygyny and female reproductive success in golden lion tamarins, Leontopithecus rosalia

Abstract

Abstract. In an 8-year study of one population of golden lion tamarins in Poço das Antas Reserve, Brazil, female aggression often resulted in the expulsion of nulliparous daughters. Tamarins were polygynous in approximately 10% of group samples and polygyny usually did not last longer than 2 years. Reproductive females in polygynous groups were usually mother and daughter, with the older female (R1) dominant to the younger (R2). A cost-benefit model using estimates of reproductive success for females in this population is presented to predict the circumstances under which polygyny might be expected. Costs to R1 for allowing R2 to breed in the natal group included the expected loss in fitness due to sharing a territory and the possibility of a role reversal in the social dominance hierarchy. The inclusive fitness of R1 was increased by half R2's expected reproductive success in the natal group. Benefits to R2 for being allowed to breed in the natal group included increased survivorship and reproductive success. Costs to R2 for breeding in the natal group included losses in fitness as a result of inbreeding. These results suggest that the benefits a reproductive female gains for expelling her nulliparous daughter from the natal group outweigh the costs only slightly when in breeding is not a factor, but are substantially greater when all adult males in the group are related to the daughter. The number of reproductive females in the group was not correlated with the availability of any sampled territorial resources, except swampland. Polygyny in this study could not be explained by the polygyny threshold model.