Monitoring ovarian cycle activity via progestagens in urine and feces of female mountain gorillas: A comparison of EIA and LC-MS measurements.

Understanding the reproductive biology of endangered mountain gorillas (Gorilla beringei beringei) is essential for optimizing conservation strategies, determining any demographic impact of socioecological changes, and providing information for comparative studies of primates. Non-invasive techniques have been used to assess the reproductive function of many primates and the importance of validating the measurements of hormones metabolites is widely recognized because they may vary even within closely related species. To determine if it is possible to non-invasively monitor ovarian activity in wild mountain gorillas, we used enzyme immunoassays (EIA) to quantify both urinary and fecal excretion of immunoreactive pregnanediol-3-glucuronide (iPdG), defined as all metabolites detected by a pregnanediol-3-glucuronide immunoassay (PdG EIA). Simultaneously, we performed the liquid chromatography mass spectrometry (LC-MS) to quantify the excretion of pregnanediol in urine and feces. Samples were analyzed over nine cycles of five females from the habituated gorillas monitored by Karisoke Research Center, Rwanda. As an additional indicator for ovulation timing, estrone conjugates (E1C) were measured in a subset of urine samples. The concentrations of iPdG and pregnanediol measured in the same samples were significantly correlated. Urinary concentrations of iPdG and pregnanediol fluctuated over the menstrual cycle but did not reveal any cyclic pattern, whereas a typical preovulatory urinary E1C surge and postovulatory increases of fecal iPdG and pregnanediol were detected. The luteal peaks of iPdG and pregnanediol levels in feces were on average 2.8 and 7.6 times higher, respectively, than averaged levels in the corresponding follicular phase. The relative number of days with observed matings was higher within the presumed fertile window than in the preceding period. Overall, the results indicate that fecal analysis of iPdG and pregnanediol is suitable for detecting ovulation in female mountain gorillas. Urinary measurements using both EIA and LC-MS appeared to be uninformative for monitoring ovarian activity in this primate.