Instructions
Look at the muscles on either side of the lower jaw; they are large and pronounced in males. The male's head will also appear square and have fatty deposits on the forehead, behind the eyes and above the ears. The female has a smaller head, without the fatty deposits.
Inspect the dorsal spikes along the back. The dorsal spikes in males are longer, especially in the neck area. This alone is not an indicator; other characteristics must be present, since some females have longer spikes.
Look at the femoral pores located along the inner thigh. If they are large and appear to be filled with a waxy substance, the iguana is a male. The female has smaller femoral pores, except for the first three to five nearest the vent, and no waxy substance will be present.
Pay attention to the size of the body. Males are heavier and have a bulge near the base of the tail that is obvious to the touch if not to sight. Press gently to check for the bulge.
How Can You Tell a Girl Iguana From a Boy?
Without a blood test you cannot tell definitively if your iguana is a boy or a girl until after the first breeding season or when it reaches a length of 9 to 12 inches from snout to vent. With proper care and feeding, this typically happens between one and two years of age; at this point, there are several indicators of sex.