The left side of the face is a mirror image of the right. There was another animal there that blocked part of the face. Originally, I was just going to use the clone tool to fix what was missing but ended up going with this symmetrical look instead.
a very arresting image .. i looked at it for some time thinking how stunning your photograph and process was .. and then i read your comment .. great solution to a common problem !! :) ...
Just realised that this IS a reflected image! Amazing how attuned we are in scanning even animal faces: something seemed odd....but it took me a while for it to click. The effect works really well.