Then why do you think they get bigger in the wild? I haven't had that be the case with any properly cared for iguana in captivity. I think that often people offer poor husbandry and try to keep the animals in too small of an environment and get tired of preparing a proper iguana salad everyday. But every iguana that I know of who has been kept in a proper environment, with proper UV and a good diet has grown as large, if not larger, than any wild iguana.