I believe it is certainly a display of dominance- I learned the hard way a long time ago, when I first started keeping U. henkeli. I had two males housed in a very large enclosure with no visbile fighting or wounds for over one year; one night a awoke to a very loud shrill, I turned on the light to find that the more dominant male (the one that always slept on top of the other) bit the tail of his cagemate, as it was flopping around in his mouth. I keep all my males seperate now. Aggresion/intimidation may be more subtle in Uroplatus, but it can not be ignored for the sake of the long term health of the subordinate animal.