Like many turtles, gopher tortoises (Gopherus polyphemus) have temperature-dependent sex determination, but young individuals lack any visible external difference between males and females — making it hard to track how a warming climate might be skewing sex ratios in wild populations. The current gold standard, laparoscopic surgery, requires specialized equipment, a trained surgeon, and months of captive rearing. This study tests three non-surgical alternatives — baseline blood testosterone, testosterone after a hormone challenge, and morphological measurements — across neonates, hatchlings, and juveniles, validating each against laparoscopy.
Baseline testosterone turned out to be by far the simplest and most reliable option once tortoises reached 4-8 months of age (hatchling stage), correctly separating the sexes with a single blood draw and a simple threshold. Juveniles were sexed with essentially no error using the same approach, while neonates were harder to classify with any method due to substantial overlap between male and female testosterone levels shortly after hatching. For researchers with access to a rearing facility and basic hormone assay equipment, this offers a much more scalable way to monitor sex ratios in this species of conservation concern.
Citation: Loope, K.J., Rostal, D.C., Walden, M.A., Shoemaker, K.T., Hunter, E.A. 2022. A comparison of non-surgical methods for sexing young gopher tortoises (Gopherus polyphemus). PeerJ 10:e13599. https://doi.org/10.7717/peerj.13599