[Fixx]

You can't generally sex an iguana accurately until it is about 2 years old and it begins to take on the characteristics of the adult, as it approaches the first breeding season.

More often than not, as well as males taking on a bulkier appearance and having a much larger dewlap, it is the femoral pores that are the best indicator as the males have enlarged ones in the breeding season.

Hello Les (I take it this is Les from LF who had Gromit).

Another way of telling is to watch them when they defecate, sometimes the males will evert their hemipenis(es?)