Estrogen excretory patterns in the Indian rhinoceros (Rhinoceros unicornis), determined by simplified urinary analysis.

Daily urine samples obtained at random from 3 mature Indian rhinoceroses (Rhinoceros unicornis) were evaluated for immunologic estrogen concentration and were indexed by creatinine (Cr) concentration. Chromatographic separation and enzyme hydrolysis of the estrogenic components indicated that the major urinary estrogen in this species is immunoreactive estrone (greater than 95%). Cyclic variations of immunoreactive estrogens (basal values of 0.1 to 0.3 microgram/mg of Cr. peak values of 5.8 to 12.5 microgram/mg of Cr) were observed at an interval of 43 +/- 2 days (4 cycles) which appear to reflect the apparent ovarian cycles. The method presented offers a practical approach for the monitoring of ovarian events in large, nontractable species.