A female bearded dragon has only one characteristic that can definitely differentiate her from a male bearded dragon by appearance. The most definite characteristic of a female bearded dragon is the lack of a hemipenal bulge, whereas the male bearded dragon will have two hemipenal bulges. This characteristic of gender, however, usually isn't visible in hatchling dragons and young juvenile dragons, though it does become easier to determine gender in adult bearded dragons.
The hemipenal bulges are located beneath the male bearded dragon's tail, above the ventral opening. In males, hemipenal bulges will be visible on both sides of the tail. The female lack hemipenes, but there will be a slight bulge in the center of her tail above the ventral opening. Although this is the only characteristic by which to determine with certainty the gender of a bearded dragon, there are other general characteristics that are more common in males than in females, and vice versa.
One of the characteristics of bearded dragons is their ability to puff out their beards and turn their beards dark. Females can do this as well was males, but males generally display this behavior more often than females, and males' beards usually turn darker in color than do the beards of female dragons. The dragon puffs out its beard and turns it dark as part of courtship routines, when the bearded dragon is feeling the need to defend its territory or when bearded dragon feels threatened.
Sizes of bearded dragons aren't a characteristic of gender, although the female bearded dragon will in general have a smaller head than her male counterparts do. Males often have thicker tails than females, although this can't be used to determine gender. A bearded dragon's tail thickens as it ages, so an older female bearded dragon might have a thicker tale than a younger male bearded dragon.
In many instances, female bearded dragons show less-aggressive behavior than male bearded dragons, but as with other characteristics, this isn't always true. Bearded dragons reach sexual maturity as young as eight months. Female bearded dragons will dig, attempting to create burrows in which to lay their eggs. Even if a female bearded dragon doesn't mate, she still might lay eggs, with about 20 eggs in a clutch. A male bearded dragon might also be seen digging burrows, however, because some bearded dragons also dig burrows for sleeping and during times of stress.