0-5: "anol stage" - fully aquatic - gills, streamlined body with no frills or wings, webbed feet - a Dathri in the anol stage is tiny, barely 2' long at the beginning, topping out at 6' in length at the end of the stage
5-15: "etos stage" - ready to venture onto land - gills and webbing disappear, crest and tail-frill grow in early, wings appear towards the end of the stage - a Dathri in the etos stage is small, starting at about 6' long and 1' tall, topping out at about 22' long, 2'5" tall, and a wingspan of about 20'
15-death: adult stage - capable of spending time on land, in water, or in the sky - wings finish growing in, sexual maturity reached around year 20, Dathri continues to grow - it's important to note that there really is no 'upper limit' on size, as a Dathri will continue to grow until death, gaining between 1" and 2" in height, between 5" and 10" in length, and between 6" and 12" in wingspan per year.
After a successful courtship and mating, female will lay 20 to 30 eggs deep underwater in a hidden grotto that she and the male will build together. At this point, nature vs nurture takes over - for Dathra who were raised by their parents, they will stick around to guard the eggs. Dathra who were not raised by their parents will now leave, split from their partners, and resume their solitary lives.
Five months later, only about 4 to 5 eggs will hatch (the rest being dud decoys). From the moment they hatch, the little anols (larval Dathra) are capable of hunting and caring for themselves, though they lack higher order intelligence and cannot mindspeak. If the parents stuck around, they will care for the anols that hatch - when the anols cannot find enough food, the parents hunt for them, and when predators threaten, the parents defend them.
Anols who reach the etos stage without parents around will immediately scatter to the four winds, becoming intensely territorial and solitary from that moment on. If, however, the parents are still around, the etos stay together to learn from their parents, absorbing the rules of interaction, of how to properly use their telepathy, and the rules of The Mindgame.
At about 13 years of age, the young will start drifting off to find their own niches within the community (or find another community to join). At this point, the majority of parents will also drift apart and go back to their own areas.