Use of salivary steroid analyses to assess ovarian cycles in an Indian rhinoceros at the National Zoological Park

Saliva samples were collected from a female Indian rhinoceros ( Rhinoceros unicornis ) housed at the National Zoological Park, and ether‐extracted for analyses of androgen, estrogen, and progestin metabolites to assess ovarian cycles. Analyses of both salivary androgens and estrogens were found to reliably monitor follicular activity. Although the temporal patterns of the two steroids were significantly correlated (r=0.62; P <0.05), they differed slightly. Salivary androgens increased earlier during the follicular phase, although both peaked at the same time in association with behavioral estrus. Based on salivary androgen profiles, the mean duration of the follicular phase was 11.4 days (ranged=7–15 days; n=17 cycles). Estrous cycle length, as measured by the time between consecutive androgen peaks, was 47.4±3.4 days (range=37–86 days). Salivary progestin measurements were effective for monitoring luteal function. The mean duration of the luteal phase was 15.5±1.5 days (range=10–23 days). In sum, assays were identified for measuring salivary steroids to assess ovarian function in Indian rhinoceroses. However, not all of the assay systems tested were effective, perhaps because of interfering matrix effects. Mate introductions in the Indian rhinoceros often require careful monitoring, and a technique for monitoring hormones in saliva could be an alternative to urine or fecal analyses for identifying estrus and timing breeding in this species. Such a technique would be particularly useful for situations in which it is difficult to collect uncontaminated urine and feces. Zoo Biol 23:501–512, 2004. © 2004 Wiley‐Liss, Inc.