This is a Western Terrestrial Garter Snake found in a tree in Sierra Vista, AZ. He was not to fond of having his picture taken... But I got the shot anyway. (sorry buddy)
I am sorry this guy didn't want to pose for you. When I took a picture of a lizard it seemed more curious of it and even posed a few times ha ha. VERY NICE you got the tongue and everything for a unwanting subject.
I've not taken many shots of a snake and those that I have done were from a visit to a zoo (so not the best of conditions) but they were all very disappointing results so when I see a good shot like this it makes me appreciate it all the more
IDK, sometimes I just get lucky I guess...