27th Annual Meeting and Symposium of the
Desert Tortoise Council, March 22-24, 2002
Abstracts

Can We Identify the Sex of Immature Tortoises By Fecal Steroid Assays?

Valentine A. Lance¹ and David C. Rostal^2
1Center for Reproduction of Endangered Species, P.O. Box 120551, San Diego, CA 92112; 
²Georgia Southern University, Statesboro, Georgia

It is important that we know the sex ratio of neonate and immature tortoise populations when studying the ecology of the species. As recognizable secondary sex characters are not evident until the tortoises are sexually mature, often in excess of ten years, a simple and reliable method to identify the sex of immature tortoises is needed. Laparoscopy in the hands of an expert has proven to be 100% reliable, but the equipment is very expensive and it does require that a small incision be made in the body wall of the neonate tortoise. Measuring circulating testosterone is also reliable in some species, but again it requires that a jugular puncture be made to draw the blood sample. Both of these methods are stressful to the young tortoises, and in wild populations under severe environmental stress the added insult of such procedures could prove detrimental to the health of the individual. Our laboratory has considerable experience studying reproductive cycles in birds and mammals, and pregnancy in a variety of mammals by measuring metabolites of steroid hormones in fecal samples. We are currently testing this method using fecal samples from desert tortoises and gopher tortoises. The preliminary results are unclear, but additional tests will be performed. We have looked at testosterone and estradiol in fecal extracts of both species and will present our initial results. Data from animals of known sex will be presented.