Infant cross-fostering in rhesus monkeys (Macaca mulatta): A procedure for the long-term management of captive populations.

Because of the constraints of captivity, captive populations are generally closed to the introduction of unrelated individuals and may eventually experience inbreeding depression and its associated problems. As a means of increasing genetic diversity in established social gropus of rhesus monkeys at the California Primate Research Center, 36 infants were used as subjects in a cross-fostering experiment in which 27 infants (75%) were successfully integrated into non-natal groups by fostering them onto unrelated females. These results have important practical implications for maintaining self-sustaining populations of captive rhesus monkeys and may eventually be extended to other captive species. Cross-fostering infants between captive social populations may be an important means of minimizing the higher mortality and morbidity and reduced fertility effects associated with inbreeding depression. Furthermore, this procedure causes a minimum of social disruption and reduces the chances that older animals introduced into new groups will be traumatized.