Gonadal Activity in Male and Female Captive Fossas (Cryptoprocta ferox) During the Mating Season

Madagascar is known for its high number of endemic species including all eight Malagasy carnivore species with the fossa as the main predator. Due to the ongoing habitat destruction in Madagascar, a large decline in fossa population is noted, and today the species is considered to be endangered. The wild Fossa population is estimated at 2500 individuals (3). The total population of captive fossas was calculated as 85 individuals worldwide including 35 males and 23 females housed in 16 European zoos (4).

Fossas reproduce poorly in captivity, and characterizing basic endocrine norms is essential for assessing reproductive competence. Therefore we analyzed fecal testosterone and progesterone metabolites to investigate the seasonal course of gonadal activity in male and female fossas, respectively.

We used the non-invasive hormone analysing technique based on measurements of fecal hormone metabolites. We first validated a fecal androgen enzyme immunoassay (EIA) for use in the fossa: immunoreactive fecal androgen metabolites were separated and analysed by high performance liquid chromatography (HPLC). When passing through the non-polar (reversed phase) column the metabolites were retained and separated based on differences in their polarity.
HPLC profiles from samples collected during the breeding season showed one major peak of immunoactivity exactly corresponding to dihydrotestosterone (DHT) representing approximately 83% of immunoactivity. No significant amount was associated with the position of testosterone (T). The DHT finding fits with data from androgen analyses in blood plasma (1) where both T and DHT had been measured but also with fecal metabolite analyses in a previous study (2). A seasonal profiling of fecal DHT concentrations revealed highest concentrations in May, the breeding season of fossas in the northern hemisphere.
To monitor female reproductive activity we first aimed to characterise the immunoreactive gestagen metabolites present in a fecal extract of a female fossa. For a closer metabolite characterisation, an enzymatic hydrolysis using Helix pomatia enzymes was performed to liberate steroids from their conjugates. In addition, the crude methanolic extract was subjected to a solvent distribution against diethylether. We used a progesterone assay (P4) and a 5a- pregnane-3-ol-20-one (5a-P) assay. The column was calibrated with known standards (progesterone, P4; 5 -pregnane-3-ol-20-one, 5α-P; Dihydroprogesterone, DHP). Four main immunoreactive metabolites were detected in the fecal extract with two major peaks, one belonging to conjugated steroids – which disappeared after hydrolysis - and one consisting of an unknown metabolite. Native progesterone was likely not to be present whereas one metabolite was similar to 5α-P based on its elution position. Therefore, the 5α-P assay was used for subsequent measurements. In one pregnant female, gestagen concentrations increased after observed mating activities (daily copulations from May 5th till 9th) peaking approximately 10 days later (May 17th) with concentrations being 80fold higher compared to pre-mating levels. One month (July 25th) after parturition (June 25th) the gestagen concentrations had again dropped to baseline level. Those females, in which no mating activity had been observed, showed irregular metabolite patterns including short term elevations to concentrations being at maximum 20fold higher than those out of the mating season. At present our sample collection only includes samples from a single pregnant female, but further collections are in progress to discriminate between pregnant and non-pregnant females based on fecal gestagen metabolite measurements. Elevated concentrations in non- pregnant female fossas might indicate that the phenomenon of pseudo-pregnancy is prevalent in this species.