In my experience of breeding tortoises (40 plus years), TSD works much better in some species of tortoises than in others. With G. elegans and G. platynota, higher temps (88-90F) produce females and lower temps (84-85F) produce males with almost 100% certainty. In Radiated Tortoises, the results are not nearly as reliable. There may actually exist a situation in Radiateds where the length and/or temperature of a cool down period prior to incubation as well as the incubation temp itself may influence the sexes of the hatchlings.

I cannot speak for the reliability of TSD in sulcata, Leopards, or other species, but my findings above (garnered from personally hatching a minimum of 138 of each race/species mentioned and tracking as many as possible to sexual maturity), indicate that it is to be considered fairly accurate (near 100%) in Star Tortoises and somewhatless reliable in Radiated Tortoises.

When buying animals represented as having been TSD incubated (or as a Sri Lankan vs. an Indian Star), you must buy only from people that you know and trust implicitly to avoid being duped. It is very similar to buying "hets" of a hot new Ball Python morph. If you don't personally own the snake's parents, what makes you really believe your normal baby is a "het" of whatever morph you hope to breed? Unfortunately, there are some unscrupulous types out there who take advantage of eager buyers by misrepresenting animals. This is more common when they know the truth will not even be learned for a few years, so the buyers must use common sense and caution to avoid disappointments.

With the advent of endoscopy as a feasible veterinary measure in tortoises, the sexes of young tortoises can be determined as early as 6 months of age now, and I expect that more and more reliable breeders will begin to offer "endoscopically sexed" tortoises in the future as opposed to "TSD sexed" tortoises. The cost might be slightly higher, but at least you can and will know exactly what you are getting from the outset. The other side of this coin is that after testing a good number of youngsters via endoscopy, breeders will know how their attempts at TSD are working, and then possibly can eliminate the need for endoscopy of their youngsters, (though there is a certainty therein which doesn't exist with TSD).

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