was the first to start doing it, and she only does it when we are talking to her, playing in the pool with her (she has a splashing game she plays) or when she thinks the other girls are doing something they shouldn't.... Like climbing up the iguana screens, she really gives 'em heck for that, then she makes this really loud constant grunting sound to the other dragons. One day Myst started doing it back, none of the others have ever made any sound but the hissing when startled or unhappy.
I wonder if it has anything to do with thembeing dominate females, we can not put them together as they both are so bossy, but then can go in with all the other girls with no problem.