Female Reproductive Endocrinology in Wild Blue Monkeys: A Preliminary Assessment and Discussion of Potential Adaptive Functions

Abstract

In this paper we demonstrate that fecal steroid assays can be used to monitor female reproductive function in wild blue monkeys. Based on mating and birth records from 21 females, we determined that 95% of all pregnancies last between 162 and 190 days. Within the period when conception is likely we identified a clear estrogen peak marking ovulation for three out of four subjects with complete fecal records. We also examined hormonal levels among females of known reproductive state and established a range of values within which a female can be classified unambiguously as cycling or non-cycling. Our data tentatively suggest that blue monkeys typically ovulate just once before conception. Nonetheless, estrogen levels seem to rise before the conception cycle and may promote the early onset of sexual behavior for purposes, such as paternity confusion, that are not directly related to reproduction.