My bearded dragon waves at me, should I wave back?
Sometimes when I walk into the room where my bearded dragons terrarium is located, he waves an arm up and down in my direction.
Does he expect me to wave back to him?
Odd. I've been told that Uros and Beardies are very similar in their behavior, and none of my Uros have ever done this.
This is a pretty common thing for beardies, and definitely appears to be some kind of greeting.
The reasons that a bearded dragon will wave their arm is not entirely explained. However, it does seem to be a form of communication. A common belief is that arm waving is a passive message, to indicate submission when a larger or more dominant beardie is near by.
So, he is acknowledging your dominance, which is healthy; you're the one who knows where the food is. In this case, you don't really need to reply; he's essentially being polite.
However, they can wave for other reasons:
One meaning is species recognition. If a bearded dragon waves at another bearded dragon, it tells the other dragon that he/she is aware of their presence.
Alternatively, the age of your beardie can affect the meaning.
Young bearded dragons may do a slow "wave" with one of their arms to signal, "I'm just a baby! Don't hurt me!" Your young beardie may even do this when he sees you walking up to him if he is intimidated by you...
While this is a not-so-nice thought, he may grow out of it. We have to remember that even reptiles are not robots; they have moods and personality quirks too that change over time.
All in all, it can't hurt to wave back. A best, he'll be comforted (you're being submissive too), at worst he'll be confused. They wave back and forth to each other quite frequently, so he may well appreciate a reply, even if he isn't expecting one.