INTEREST IN INFANTS VARIES WITH REPRODUCTIVE CONDITION IN GROUP-LIVING FEMALE PIGTAIL MACAQUES (MACACA-NEMESTRINA)

Previous studies of macaques have failed to show a relationship between female reproductive condition and infant-directed behavior. This has led to the view that maternal responsiveness in nonhuman primates is independent from hormonal variables and is mainly regulated by social and experiential factors. The present study reports longitudinal data on interactions between group-living adult pigtail macaque females and other females' infants less than 12 weeks of age during the 6 weeks prior to conception, the 24 weeks of pregnancy, and the first 12 weeks of lactation. These periods represent different hormonal conditions in the reproductive cycle. Infant-directed behavior increased in frequency during early and middle pregnancy, decreased around the time of parturition, and increased again during lactation. The frequency of infant-directed behavior also increased significantly in the 2 weeks after infant loss during lactation. These results are in accord with recent evidence in New World monkeys indicating that maternal responsiveness in nonhuman primates develops during pregnancy and it is probably hormonally regulated.