How to Tell Your Chameleon's Gender

Male panther chameleons have paired reproductive structures termed hemipenes. When copulating, one of these hemipenes is everted from the vent, and inserted into the female’s cloaca. When not breeding, the hemipenes are held inverted, inside the base of the tail. This causes two bulges to be visible at the base of the tail of mature males, though the bulges aren't always obvious with young animals. Females will have a smooth taper starting from the vent area and moving down the tail.

Some chameleons have elaborate casques, horns or other cranial adornments. Generally these are more prominent on males and are used in male-male combat or as an advertising device. Male Jackson’s chameleons (Chamaeleo jacksonii) have three horns on their faces to battle with other males. The casques of veiled chameleons (Camaeleo calyptratus) are present in both genders, as they are used to collect condensation at night but are much larger in the males.

Veiled chameleons offer an exceptionally easy method of determining gender: The males are equipped with a single small outgrowth on each back leg. Termed tarsal spurs, the spurs are present immediately after hatching, allowing you to determine a lizard’s sex immediately.

Males and females of many chameleon species have different coloring. Chameleons are well known for their color-changing abilities, which they use, at least in part, to communicate with other chameleons. Most chameleon species, like panther chameleons (Furcifer pardalis) and Parson’s chameleons (Calumma parsonii), have boldly colored males, and females who tend to be clad in earth tones. Conversely, carpet chameleon (Furcifer lateralis) females are much more boldly colored than the males of the species, sometimes including blue, white, yellow and purple. Pregnant females of most species will display dark or highly contrasting color schemes, designed to dissuade males eager to breed.

Size can serve as a way to tell mature males from females, but it doesn't help much in sexing preadult specimens. In most species, males grow larger than females. In some of the larger species, like panther chameleons, the difference can be significant, with males almost doubling the size of females. Dwarf chameleons (Brookesia sp.) often display the opposite tendency -- males are usually smaller than females. You'll have to know your species' norms and they'll have to be properly fed adults to sex them by size.

A chameleon's reaction to other individuals of the same species can signify gender in many cases. Healthy, well-acclimated males will often adopt flamboyant coloration and aggressive postures immediately upon seeing another male. Females usually won’t react very much to other females but will usually either adopt receptive or nonreceptive coloration in the presence of males, depending on their reproductive states.