Fecal metabolite and blood steroid concentration patterns in relation to reproductive behavior during the ovarian cycle of African lions (Panthera leo)

Abstract

To develop successful ex-situ breeding programs for the conservation of threatened wildlife, an understanding of reproductive endocrinology in the species of interest is essential. Fecal hormone metabolite patterns are widely used in this regard, but limited information is available regarding how these reflect blood hormone profiles. This study aimed to longitudinally monitor and compare circulating progestagen (sP) and estrogen (sE) concentrations, as well as fecal progestagen (fPM) and estrogen (fEM) metabolite concentrations with observed reproductive behaviors of African lionesses. For 18 months, blood sampling (n=309) from five captive lionesses took place 1-7 times per week during positive reinforcement training. In parallel, over a period of 9 months, fecal samples (n=129) from four of these lionesses were searched for daily and collected when found. Daily behavioral monitoring of all females enabled classification of reproductive stage according to presence/absence of characteristic behavioral events (i.e., “allowing mount”, “copulation”, “flirting run”, “lordosis”, “purring”, and “rolling”). Competitive enzyme immunoassays were used for steroid quantification. In total, 11 an-ovulatory and 16 ovulatory cycles (7 pregnancies and 9 pseudo-pregnancies) were assessed. When compared, the pattern of fecal hormone metabolite concentrations matched reproductive behavior more reliably than circulating steroid concentrations. Both sP and fPM patterns were correlated (n=51; r=0.86) and enabled identification of luteal phases, which helped to distinguish between pregnant and non-pregnant females. In contrast, detection of estrus by measurement of sE and fEM was not accurate regardless of the matrix evaluated.