I have a theory about mirrors. I think most chams fireup at the mirror itself rather than their reflection. Ive never been able to get a response from mine (several times), he's simply not intimidated. "Its a mirror, what? me worry?"
I think to a cham theres probly a big difference between another living animal and its reflection, something we dont see, or/and smell perhaps, thats missing from a reflection, despite their great vision.
lightwaves given off the skin in colors we cant see, pheramones etc.
Im sure some chams do fire up, but maybe its the shape/movement only they recognise?
Ive had chams DVD running in line of sight with homer, same species too, no interest at all, no reaction.