This is an excellent portrait. It is hard to find anything wrong with it. It is quite a dramatic photo. I think you posted some photos of snakes in the past which you were right on top of. LOL, better you than me. Snakes make me very uncomfortable in a very primitive way.
The thing with Cotton's is... when they are in defensive mode they are looing up at you which tends to lead to a better vertical shot... unless you're shooting the whole body. On this image I had someone with me and the Cotton was more worried about him than me... thus he kept his eye on my buddy and I got some great shots.
Getting good tounge flick shots can be a challenge sometimes because the movement is so quick. It's normally a timing issue and I fire a burst when I think it's going to happen.
I got really lucky with that shot and how it kinda bends back over the head.