Fecal Steroid Profiles in Black-Footed Ferrets Exposed to Natural Photoperiod

We monitored seasonal ovarian and testicular activity in adult, captive black-footed ferrets (Mustela nigripes) using non-invasive fecal steroid metabolite analyses. In females, radioimmunoassay of liquid chromatography-separated fecal extracts revealed that estrogen immunoactivity coincided with unconjugated estradiol-17β, whereas progestogen immunoactivity corresponded with a single conjugated and several unconjugated steroid forms, only 8% of which co-eluted with progesterone. In males, androgen immunoactivity was associated with several unconjugated metabolites, ∼7% of which co-eluted with testosterone. We collected fecal samples 3 times per week from 5 female and 6 male black-footed ferrets for 18 consecutive months for longitudinal assessment of gonadal activity. Assessment of 7 pregnancies and 9 pseudopregnancies revealed no differences in temporal or quantitative fecal estradiol and progestogen metabolite excretion between these 2 reproductive states. We found elevated concentrations of fecal estradiol were associated with mating activity and an increase in the percentage of superficial cornified epithelial cells in vaginal lavages. Fecal progestogen concentrations increased about 1 week after breeding, peaked at midterm and then declined to baseline at parturition. Males exhibited seasonal fluctuations in fecal androgen excretion with increased concentrations observed ∼2 months before females entered estrus. Our results indicate that fecal steroid analyses can be used effectively to evaluate gonadal function in the black-footed ferret and might prove valuable for aiding captive breeding strategies to improve species conservation.