I read through the posts and one thing to keep in mind is that there are only guidelines. Some will "fit" better than others.
The Barkers write that females will reach "probable sexual maturity" at about 1000 grams. They also state that "the first potential breeding season for most females is their 3rd winter". They also suggest that this might be on the small side and females may produce smaller clutches and (more) infertile eggs. These facts have been backed by many breeders.
Just because the female is ready to breed (or more likely mature enough) does not mean it's the best time to breed her. A 1000 gram female would likely have a small clutch and be unable to breed for at least two seasons. Breeding also depends on size. I have a couple females in the 3000 gram area that are still light for their length and thus will not breed/ovulate.
I had light females (over 2000 grams) copulate yet produce nothing.
Suggested weight for males is 600-650 grams. At this point they may reach "probable sexual maturity" and produce sperm-plugs, but may not breed. Mine would not breed until he hit 800 grams.
My general rule of thumb:
1500 grams for females
600 grams for males
Would/could I breed a female at 1000 grams. Sure you can. Just keep in mind that you may (most likley) expect a smaller clutch, potentially infertile eggs and a couple years until the next breeding season. I might do this if I was trying to prove out a female. But mostly, I would not.
I cannot comment on maternal incubation. I'm not brave enough for that. I have a clutch in the "oven" now where the mother discarded one of the eggs. So far, the discarded egg candles fine. July 28th, I'll know for sure.
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Jay A. Martin