Monitoring reproductive steroids in feces of Arabian oryx: toward a non-invasive method to predict reproductive status in the wild

We measured metabolites of progesterone (progestins) in fecal samples collected from captive Arabian oryx (Oryx leucoryx) females in postpartum (n=8), nonpregnant (n=9), and pregnant (n=8) reproductive stages between 1996 and 1998. We analyzed progestins using enzyme-immunoassays for pregnanediol and 20-oxo-pregnanes, respectively. Progestin concentrations were elevated for 3 days after parturition and then decreased to basal anestrous concentrations. Ovarian cyclicity resumed 25±2.4 days after parturition in 5 of the 8 females monitored. In nonpregnant females, excretion of fecal progestins followed a cyclic pattern increasing 6- to 12-fold from the follicular to the luteal phase. Fecal progestin concentrations allowed discrimination between pregnant and nonpregnant females after 3 months of gestation (P3 months) than during early pregnancy (0–3 months). These data were subsequently used to set criteria for designation of a cow as pregnant in 55 free-ranging Arabian oryx in the reserve of Mahazat as-Sayd, Saudi Arabia sampled in 1998–1999 and 2003. The proportion of pregnant and nonpregnant oryx correctly identified by the test was 81% and 83%, respectively, when using both progestin assays. Despite a limited sample size, our results provide evidence that fecal progestin analysis is a reliable non-invasive method to determine the reproductive status of captive Arabian oryx and that it also can provide reasonably accurate physiological indices of pregnancy status in free-ranging specimens.