Assuming the iguana has been properly cared for it should reach sexual maturity at about 18 months old. Gender can be determined when the SVL is 8-9 inches: about the time they are a year old.
I haven't had coffee yet.....tell me again...how big is Dudley? (SVL and STL)
Someone help me out here, I've never had a baby ig....the femoral pores are visible even as babies arent they? My spiny tailed is only 3.5" SVL and I can see his...same with my uromastyx who is right at 5" SVL
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If you know what you're looking for you can tell at a year...for the rest of us:
The changes in the femoral pores will be most prominent in the male during the first breeding season of the year when he is between 18 months and 2 years old if given the right care. The female will stay relatively small.
You will also be able to see the hemipenal bulges at the base of a males tail which shows a slight indent down the center vertically between the bulges. Females do not have this. Their tail is fully rounded.