FURTHER HORMONAL SUPPRESSION OF ELDEST DAUGHTER COTTON-TOP TAMARINS FOLLOWING BIRTH OF INFANTS

Reproductive suppression of females is found throughout the Callitrich ids. However, in many species some evidence of ovarian activity is obs erved in subordinate females. Subordinate cotton-top tamarin females i n our colony have never been observed to ovulate in the presence of a reproductive female. However, ovarian follicular development does occu r, and measurable levels of urinary estrogen and luteinizing hormone a re frequently found in subordinate females. We studied 11 female tamar ins living in family groups with a reproductive female. Each of the 8 eldest daughters had measurable urinary estrogen and LH levels and sho wed a reduction of hormonal levels when new infants were born. The 3 y ounger daughters showed barely detectable hormonal levels that did not change. Following the birth of infants the eldest daughters scent mar ked less frequently, increased time in contact with and grooming group members other than the mother, but they were more often targets of ag gression than immediately prior to infant births. The eldest daughters were somewhat less involved in care of new infants than expected, alt hough they spent much time in proximity to those carrying the infants. These results suggest that the further reduction of hormonal levels i n subordinate females after the birth of infants may function to preve nt these females from competing with mothers during the post-partum es trus rather than recruiting the eldest daughters as helpers for infant care. (C) 1993 Wiley-Liss, Inc.