most facts given are the 'averages'. But there are always those who are above or below the average.
To start breeding it is best to wait till a dragon is at last 350g and 15 months or more of age. It doesn't mean every dragon is going to wait that long to produce infertile eggs. Bearded dragons can mature as early as 8 months, and I think the earliest i have heard of was something like 6 months.
Same with time between clutches. The average is 3-4 weeks, but some, as BDLvr stats, have clutches as early s 2-3 weeks between each clutch..and I am sure there are dragons who take 5-6 weeks between clutches.
For myself personally, I try to stick with 'averages' and 'recommended' facts, but I am very much aware things don't always fall on averages or recommended facts.
A bearded dragon can have eggs at 8 months, and with proper husbandry and sufficient healthy food provided, can gain weight and carry clutches without any health risks. But if any of the requirements are lacking (ie temps aren't exact, not enough space, partially impacted...etc) a 8 month dragon having a clutch of infertile or even fertile eggs, can end up with complications (ie egg binding, calcium crash etc).
Important thing to know is not everything is guaranteed in animal care. Understanding the basics is important and I feel the average care info is best to give out, as it gives a sound range for new people to judge against (or even experienced people) to make sure things are right. For animals that just don't want to fall within that average range, well, they that keeps us on our toes, as it makes us wonder...why is the baby dragon not eating 30 pinhead crickets a day? How come my 10 month old female is trying to dig to China when she's never seen a male much less been bred? She's 4 weeks since her first clutch, how come she hasn't lain her second one?.... thus, we look for answers..even if there is nothing to worry about, better to worry too soon, then worry too late.
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PHLdyPayne