Adult and juvenile sex identification in threatened monomorphic Geocrinia frogs using fecal steroid analysis

A reliable method for the confirmation of sex in Geocrinia frogs is currently unavailable. A captive colony of Geocrinia frogs was used to determine whether fecal steroid analysis could be used as a noninvasive method of sex diagnosis in mature frogs. Linear discriminate analysis, using measured concentrations of fecal hormones, also was applied to establish whether a reliable model could be developed to verify the sex of juvenile frogs. Fecal samples were collected over a 3-month period from all frogs in 2010, and again from 12 frogs in 2011. Samples were pooled for each individual and tested for testosterone metabolites (TMs) and estrone conjugate metabolites (EMs) using enzyme immunoassays. Mature male frogs had higher (P < 0.01) mean TM : EM ratios than those of mature females, with mature male and female ratio ranges being 100% distinct. Mature female frogs had higher (P < 0.01) mean EM concentrations than those of mature males, but EM concentrations overlapped between the sexes in 18.7% of cases. There was no statistical difference (P = 0.28) between mature males and females in mean or range of TM concentration, with overlap between the sexes in 75% of cases. Juveniles had hormone values similar to those recorded for mature male and female frogs. Generated discriminate rules were able to distinguish (100%) between mature males and females and correctly classified the sex of 75% of the juvenile frogs. It was concluded that fecal steroid analysis offers a promising, noninvasive approach to sex identification in Geocrinia frogs. Copyright 2013 Society for the Study of Amphibians and Reptiles