Reproductive steroids are detectable in the faeces of dugongs

Abstract

Reproductive steroid (oestradiol and testosterone) levels were measured in the faeces of ten wild dugongs (Dugong dugon) from Moreton Bay Australia, using radioimmunoassay (RIA). All faecal samples, including from both genders and from both immature and mature dugongs contained detectable levels of oestradiol and testosterone. Faecal testosterone levels were high relative to oestradiol concentrations in all samples, regardless of gender. The highest levels of testosterone occurred in adults (body lengths ≥250 cm), in both males (1146.7 ng g-1 dry weight faeces) and females (691.1 ng g-1 dry weight faeces). The highest oestradiol levels were recorded in adult females (37.2 ng g-1 dry weight faeces). In mature dugongs, the ratio of testosterone to oestradiol was higher in adult males than in females, suggesting that this ratio may be a better indicator of sex than levels of individual steroids. This study represents the first step in an investigation into assessing the reproductive status of free-ranging dugongs.