Instructions
Look at the underside of your iguana's thigh. Males have large, distinctive femoral pores that contain waxy plugs. Females on the other hand have smaller, non-protruding pores which are often difficult to see and are not filled with a waxy substance.
Look for fat deposits behind the iguana's eyes. Males have large fat deposits on the back of their heads, while females lack these fleshy, protruding deposits.
Observe the shape of the iguana's head and the size of its cheek scales, called the sub-tympanic shield. Males have blockier heads and larger sub-tympanic shields than females, who tend to have sleeker heads.
Observe the length of the dorsal crest, or the row of spines that extend down the iguana's neck and back. In most cases, adult males have larger dorsal crests, especially around the neck.
Look at the iguana's dewlap and jowls. The male's dewlap, or the sagging skin on the neck, will typically be longer and will have small notches on the bottom edge. Males will also tend to have larger, heavier jowls, though some older females will also have this trait.
Feel the area at the base of the iguana's tail very gently. In males, there may be some swelling and bulging at either side of the base of the tail, where the hemipene--the male reproductive organ in iguanas--can be found.
How to Tell Male & Female Iguanas Apart
Attempting to determine whether a reptile is male or female, in a process known as sexing, can be somewhat difficult, as reptiles lack many of the obvious external secondary sex characteristics that birds and mammals have. Not only do iguanas, both male and female, have internal sex organs, but they do not exhibit sex differences that can easily be observed. Depending on the type of iguana and the geographic area from which it comes, males and females may be practically indistinguishable at first glance.