Females will arm wave to males during mating courtship but babies and non mature dragons of both sexes will arm wave. I think it's a way of saying, 'Here I am, I am no threat, don't eat me, I can move if you really want me to.'
I have seen baby bearded dragons wave at me, eachother other, their reflections etc when in crowded cages in petstores many times. It is neat but I do feel it's a sign of submission, or appeasement. Certainly both sexes will do it, as well as teh head bob. I am sure submissive males will wave to a more dominate male. IT is never a good ideal to house two males in teh same cage, unless it is HUGE! (I am talking room size huge....the males have to be able to get far enough away that the more dominate male can't find them)
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PHLdyPayne