Is My Iguana a Boy or a Girl?
The only definitive way to tell whether your young iguana is a boy or a girl is by taking a blood sample and having a DNA test run. Obviously, the average iggie owner isn't going to want to go to this trouble.
So how does the average person know whether to name their new ig companion Betty or Bert?
There are hints and clues to an iggies sex that can be observed even in iguanas barely a year old. If your young iguana shows a definite hemipenal bulge, then it's a pretty safe bet that you have a boy on your hands. The photo below shows the very pronounced hemipenal bulges of Xander when he was less than a year old.
Another external clue can be "notches" in the dewlap. In some species of iguana, males have pronounced and quite noticable notches in their dewlaps while females do not. Our Bailey and Mary are perfect examples of this as you can see in the two photos below. On the left, Bailey, our male; on the right, Mary, our female.
Next we have what are affectionately referred to as brain bumps. These are fatty deposits on the top of an iguana's head. In males, these bumps or bulges can get quite large - the older the iggie, the larger the bumps. In females, these bumps are often practically non-existent. In the photos below you can see Bailey on the left and Mary on the right.
If your iguana is a teen or adult, you can check the femoral pores to find out what sex it is. The femoral pores run along the underside of the hind legs. In the next pair of photos, you can see male femoral pores on the left and female on the right.
Of course, you can be absolutely certain your iguana is a boy if he shows you one of these:
