two years on average, best to let them grow to full size before breeding, that can take one to two years depending on how much you feed them. they have been known to breed after one year, though I havn't had it happen even though mine normally reach full size after 12 months. I find the males arnt that interested, they head bob but fail to follow it through, though a one year old female may have no choice if paired with a two year old male.