Pii: S0039-128x(01)00126-x

Fecal extracts from a pregnant black rhinoceros, Diceros bicornis, were analyzed by radioimmunoassay, HPLC, and by GC-mass spectrometry. From 40 g of dried feces a total of 33 pregnanes in the C21O2 series, including a number of novel 17 epimers were identified. No progesterone was recovered. The principal progesterone metabolite by mass was 5 -pregnan-3 ,20 -diol (44.5%), which did not cross react with the antibody used in our RIA. The antibody recognized progesterone and pregnanes with 20-one configuration, which when combined made up less than 15% of the total C21O2 steroid mass. Of the 33 pregnanes in the C21O2 series identified, 81%, by mass, were in the 5 -configuration. These results are compared with studies in other rhinoceros species (Asian and Sumatran) in which pregnanes in the 5 -configuration are the major fecal metabolites, and the white rhinoceros in which pregnanes in the 5 -configuration are the dominant form. © 2001 Elsevier Science Inc. All rights reserved.