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Determining Sex in Lizards

Clinician's Brief (Capsule)

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Because fights between territorial male lizards are violent and often fatal, reptile breeders frequently request sex determination before adding a new lizard to their group, especially for species that do not show evidence of sexual dimorphism. 

This study aimed to evaluate diagnostic sensitivities of ultrasound, contrast radiography, and plain and contrast computed tomography (CT) for sex determination by identifying hemipenes in 4 popular lizard species: bearded dragons (Pogona vitticeps), Egyptian spiny-tailed lizards (Uromastyx aegyptia), blue-tongued skinks (Tiliqua scincoides), and Sudan plated lizards (Gerrhosaurus major). 

Lizards of known sex (n = 19; 10 female, 9 male) were each subjected to all 4 imaging modalities, with blinded evaluators. In a few subjects, thick tail scales prevented ultrasound. Otherwise, all imaging was easily accomplished on nonsedated patients within 5 to 10 minutes; contrast agents were gently instilled through the cloaca. Contrast radiography and contrast CT were highly sensitive for detection of hemipenes (8/9 = 88.9% and 9/9 = 100%, respectively). With ultrasound and noncontrast CT, hemipenes were often difficult to distinguish from surrounding tissues. Although these results cannot be assumed to apply to other lizard species or juveniles, the methods and results from this study can serve as a reference for future research. 


This article offers a safe, accurate method of determining sex in lizards. Although this article discusses several imaging modalities, the most clinically useful procedure for the exotic practitioner is radiography. Unlike other procedures in exotic pet practice that require expensive equipment and advanced training, the radiographic procedures detailed here uses readily available radiological equipment and water-soluble contrast media. The radiographic procedure is safe, minimally invasive, does not require anesthesia, and has a high degree of accuracy. It is important to recognize the different radiographic appearance of urogenital anatomy between species. Based on accuracy, cost, and availability between the different imaging modalities, it is an easy decision to choose contrast radiography for sex determination in lizards.—Ajay Sharma, BVSc, MVSc, DVM, DACVR


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