How can you tell a baby boy iguana from a baby girl iguana?

It's up to you however they both have their pros and cons.

First off let me say that you cannot tell whether you have a male or female iguana until they have reached sexual maturity which does not depend on age but on their snout-to-vent length. A sexually mature iguana's snout-to-vent length is about 10 inches.

Females will lays eggs regardless of whether or not they have had a male companion and sometimes this can result in egg binding if the female is not given a moist box to lay her eggs in. If anything goes wrong with the eggs inside of her then that could result in huge veterinary bills or even her death.

Males won't have that problem but they tend to become VERY VERY aggressive during breeding season. Regardless of whether or not they are tame during regular parts of the year they can become monster from hell in breeding season, biting, whipping, which can result in stitches for you.

So you can decide which you prefer