Demographic studies provide critical data for understanding the evolution, ecology, social organization and mating systems of primates. One influence on the demographic structure of a population is the pattern of emigration of individuals from their natal groups. In cooperative breeders, the offspring may stay in their natal group even after maturity, and many researchers are investigating the possible ecological and social factors responsible for this pattern and the resulting reproductive skew that occurs within these populations. In Callithrix jacchus, the common marmoset individuals disperse from their natal groups as adults, females disperse more frequently than males, and dispersals are more frequent during the rainy season than during the dry season. However, neither group size nor tertiary sex ratio is correlated with dispersal. Captive animals that undergo experimental procedures that simulate natural conditions after emigration (isolation from a group followed by movement into a new environment) trigger different physiological and behavioral responses in each sex. Males increased significantly in cortisol levels after separation, and upon placement in a new environment together with other males, they intensified their affiliative relationships and cooperated in tasks to acquire food. Females were less affected by isolation (as measured by changes in cortisol levels) and significantly increased piloerection and scent-marking behaviors when they were moved (as dyads) to a new environment. These differences suggest that males and females have evolved different strategies for dispersal and breeding success, and the dynamics of social relationships between females seem to be the main determinant of the demographic profile of common marmoset populations. Moreover, besides adaptations related to reproduction, females show additional behavioral and physiological mechanisms that may be selected to cope with social isolation following emigration.