I am often asked how to sex Beaded Lizards (Heloderma horridum) and Gila Monsters (Heloderma suspectum), so I thought I would post the best pictures I have of a proven pair of Beadeds along with an explanation. Juvenile Heloderma are very difficult to sex accurately. No one, including me, can reliably sex an immature animal. Juvenile Heloderma can be sexed by a veterinarian using endoscopy; HOWEVER, the veterinarian must know the difference between ovaries and testes, which most veterinarians do not.
As Heloderma become sexually mature, it becomes easier to sex them from build, tail size, and head size. In older Heloderma, any really giant specimen is undoubtedly a male at 99% probability. A sexually mature male Heloderma will be larger, bulkier, thicker at the base of the tail where the hemipenes are, and have a slightly longer tail.
Upper specimen = male. Lower specimen = female.
Upper specimen = male. Lower specimen = female.
Left specimen = female. Right specimen = male.
Left specimen = male. Right specimen = female.
Left specimen = male. Right specimen = female.
