Understanding the basic reproductive biology of wild felids by monitoring of faecal steroids.

The ability to track gonadal activity is essential for understanding the fundamentals of reproduction. Faecal steroid metabolite monitoring is a well established tool for evaluating reproductive processes in diverse mammalian species, including felids. Domestic cats were used as a model and injection of radiolabelled oestradiol, progesterone, testosterone and cortisol revealed that > 85% of metabolites were excreted in faeces with a time lag of 12-24 h. Steroids were extracted by boiling faecal material (wet or dry) in 90% aqueous ethanol followed by immunoassay with group-specific antibodies that crossreact with excreted metabolites. This approach was used to illustrate the diversity of oestrous cycle characteristics, gonadal responses to photoperiod and ovulatory sensitivity within the felid taxon. Longitudinal analyses demonstrated that faecal oestradiol increases with observed oestrus, and that the duration of the oestrous cycle varies among felid species. Seasonality in gonadal activity was observed in some species (for example clouded leopard, Pallas' cat), whereas other species (for example margay, cheetah, oncilla) are cyclic all year round. Although cats are considered induced ovulators, non-mating and spontaneous ovulation occurred in some species (for example domestic cat, clouded leopard, lion, leopard, margay) with varying frequency. There was also evidence that suppressed ovarian activity and oestrus occurred in group-housed cats (for example cheetahs). As assisted reproductive techniques, such as artificial insemination, are becoming increasingly important for managing zoo species, steroid metabolite monitoring has been especially useful for examining the efficacy of associated hormonal therapies. Exogenous gonadotrophins used to induce ovulation often caused ovarian hyperstimulation, which resulted in a maternal endocrine environment that differed from that of naturally mated cats. Finally, there is evidence that the adrenal status of animals managed under different husbandry conditions can be assessed non-invasively, thereby enhancing our understanding of how social and environmental factors affect animal well-being and reproductive fitness. In summary, understanding the basic endocrinology of endangered felids generates knowledge that can be used to improve management strategies. Because of its enormous utility and non-invasive nature, faecal hormone monitoring is one of the most powerful tools available in zoo research today.