Gonadal activity in male and female captive fossas (Cryptoprocta ferox) during the mating season

Contents The fossa is an endangered, mongoose-like carnivore species endemic to Madagascar with a breeding season (BS) in the southern hemisphere spring. For the present study, faecal samples of captive fossas were collected for over 1 year for five males and four non-pregnant females, and for two pregnant animals during the reproductive period. The goal was to assess gonadal activity using non-invasive hormone measurements of faecal testosterone (T) and gestagen metabolites using assays previously established in our laboratory and further validated in this study. All study animals were housed in northern hemisphere zoos. In males, the seasonal T metabolite profile revealed a peak in spring (March). High performance liquid chromatography (HPLC) analysis was used to characterize the faecal hormone metabolite composition. The highest immunoreactivity was detected in the position of dihydrotestosterone, whereas native T was not detected. In the two pregnant females, gestagen metabolite concentrations increased 4–9 days after the initial matings and remained elevated throughout gestation with concentrations dramatically higher than those of the non-pregnant females during the BS. In these females, gestagen metabolite analyses did not reveal a seasonal pattern similar to the males. The HPLC-analysis revealed that the major proportion of immunoreactivity was associated with an unknown metabolite, whereas native progesterone was undetectable. The seasonal hormone pattern of male fossas gives proof of the reproductive seasonality of this species. The elevated 5α-pregnan-3β-ol-20-one levels in pregnant animals allows for the characterization of pregnancy in the fossa based on analysis of faecal steroid metabolite concentrations.