Thanks again, Ilian: the discussion is interesting and beautiful, because it's also a "philosophical" discussion, I understand well what you write, but I must add few other words, in order to be complete. And I will write about snakes, because they are the only animals I know well, together with human beings... (I'm a medicine doctor... ).
Let's go back to the oxycephalas of Zurich zoo.
I wrote that their "artificial" environment was very near to their natural one in Thailand: a huge, walk in reptilarium, with living plants, water sources and everything else.
You wrote, approximately (correct me if the sense does not correspond): "Beautiful terrarium, but nobody can affirm or deny that the presence of the tourists in front of the terrarium could have a strong effect which influenced the behaviour of the snakes...."
Ok: first objection of mine. Who does affirm one thing, he or she must carry the proofs of his/her affirmation. Otherwise I could also write: "Who can say / deny that the different latitude of Zurich or the stars above Zurich could play a considerable role in oxycephala behaviour?" There is nothing that could let us think towards a similar concept... simply so...
But there's more. And I've got a picture for this.
This G.oxycephala was photographed in Kao Yai, very near a path where hundreds of tourists walked regularly during the day. I was the only tourist who saw the snake. Probably this snake watched at least hundred walkers passing by itself before I could notice its presence.
So: the fact that oxycephalas come in close visual contact with many humans/tourists also "in the wild" is a fact. And a fact that absolutely does not upset oxys behaviour or let them go crazy...
But I would carry another more interesting fact.
If a "visual contact" with humans can happen in the wild and does actually happen, what can we say about snake handling, which is a rather normal practice with captive snakes, even if kept in large walk in terraria?
Could handling cause terrible psychological damages in snakes and deeply alters natural snake behaviour?
Look at this picture, of an aesculapian snake found in spring in Croatia:
I've seen this male aesculapian while it was looking for something: maybe prey but I think more probably a female.
I took the snake up in my hands, photographed it, and after a couple of minutes released it.
It went on searching, as if nothing had happened, and I continued to watch it crawling back and forth for many minutes again and again…
So: handling is not so terribly “harmful” for snakes, and not even for wild ones…