Bearded dragons (Pogona vitticeps) often appear frustratingly androgynous to their keepers, but you can usually determine your pet’s gender by examining the creature's tail base. Other clues lie in your pet’s build, size and behavior, but these are often impractical criteria if you don't have numerous dragons to compare. If you cannot determine the answer yourself, your veterinarian can likely provide a definitive answer.
Male lizards have paired reproductive organs, called hemipenes. They hold these structures in the bases of their tails when not in use. Often, the hemipenes create two distinct bulges at the base of a male bearded’s tail. To observe them, hold your lizard in the palm of your hand and gently arch the tail backward, across the lizard’s body. The hemipenes should be visible immediately behind the vent -- often, the depression between the two hemipenes is easier to discern than the bulges are. Females lack these paired bulges and the central depression; in some cases, they display a small, bump in the middle of the tail.
It often helps to gently twist the bearded’s tail from one side to the other while looking for the bulges.
Behavioral clues are most helpful when you can watch bearded dragons interact with each other. Males are more likely to monopolize the best basking site, and they often bob their heads to assert their dominance. Females tend to run from aggressive males or wave their arms in a submissive gesture. However, two beardeds of the same sex may exhibit similar behavioral patterns, so a dominant specimen need not necessarily be a male, a submissive one not necessarily a female.
Male bearded dragons typically grow longer than females do and have larger heads relative to their body size. Many males have black beards, but females may as well. However, in most cases, beard color is a poor criterion to consider, as the color and richness of the beard color can change drastically in a short time.
Bearded dragons develop hemipenal bulges and secondary sexual characteristics gradually over the first 3 months to 12 months of their lives. While some skilled breeders are capable of discerning gender of month-old lizards with reasonable accuracy, it is often necessary to wait until the young are at least 4 months or 5 months old before you can reasonably easily distinguish between the two. In practice, this often means that males can be definitively sexed at a younger age.
Your veterinarian’s knowledge of lizard reproductive anatomy is doubtless superior to your own, so she may be able to discern subtle details that you missed. Alternatively, if she is unable to determine your pet’s gender via a basic examination, she may be able to force the lizard’s hemipenes to evert if they are present, or she may probe your lizard with a small steel rod. If nothing else provides a positive identification, endoscopic procedures allow your vet to visualize your pet's internal sex organs, which provides a positive identification.