I've seen several do this. It only seems panthers do this, not that I have experience with all chams... I actually had one die because it managed to bite off chunks of the vine and eat it...I did a necropsy and found he was impacted from the material used to coat the wires for those vines. I have NO idea why they do this and I can't even come up with a good theory....maybe trying to remove bark bits in order to get at grubs or insects that would hide under loose bark on the buttress of trees? I don't know.....
So beware!