I think it's going to be really difficult to get the indigo to open the mason jar!
Actually, I have had EXACTLY the same experience with eye caps, with my older male couperi, and I feel absolutely sure he knew that I was helping, and was very patient. In spite of the fact that my head-restraining was not close enough or restrictive enough to prevent a bite or crawling away, he allowed me to fight with the caps for ten minutes, without resistance. For future reference, the flat-bladed tweezers worked pretty much instantly, and I used human sterile eye-lubricant to aid the process. The ten minutes was spent trying to use a fingernail.
I've had many thousands of snakes, in my life. Now, only couperi. Personally, I feel that couperi are more intelligent than almost any snakes I've known, with the possible exceptions of King Cobras and all the Mambas. ....But maybe that's no more than proof of what Tim said: that we equate active awareness with intelligence -- certainly, the Mambas and King Cobra are the epitomes of that.
But, on the other hand: I used to put harmless snakes in my shirt a lot, when I was younger: and I've got to admit that only king snakes ever tried to eat me. That really contributed to my thinking of them as pretty stupid (sorry, getulus guys). (Hey, maybe I'M STUPID, too, I tried it maybe ten times, before I quit putting getulus ssp.in my shirt){{I never tried putting elapids in my shirt
}} (Rat snakes never did that ....maybe I just smelled like a snake, so king snakes liked me?)
My indigos also always crap in the same part of the cage.....admittedly, each has a different favorite spot in his or her cage: The '12 girl always craps in the water bowl; the 7 year female always craps around her hide box #2, the youngest boy always goes in the live plants, the youngest girl always in the same corner of her cage: ALWAYS.
Now, I've always had many cats - and they always find the litterboxes. When I had three big dogs, and lived in the desert, I always emptied the cat litter in the same spot of my 40 acres: and the dogs very quickly learned to use that same spot for their own solid waste. Is there not something intelligent there?
(Before you say it's stupid to crap in your water bowl, well, my snakes have 2 bowls in each cage, and they are inspected daily. That girl craps in only 1 of the two bowls, always the same one.)
My '12 couperi absolutely know me from other people; they always try to come back to me, when other people are holding them. This has been proven MANY times. I don't have repeated evidence for the other 3 snakes, but I have not had them long enough, or had other people handle them much.
Maybe I'm just projecting my own wishes: but I personally feel that couperi is the smartest NOT ABSURDLY DEADLY snake I've had the pleasure to know. As for other Drymarchon, I cannot say -but I had ~ a dozen couperi, MANY decades ago - when I owned HUNDREDS of snakes, and I always felt that they were very special and intelligent, even then. I've kept and even bred Masticophis and Coluber constrictor ssp; I have never thought them to be any smarter than your average snake -- and DAMN, THEY ARE ALERT.
Thanks so much, eminart, for introducing the thought-provoking question! Don't anyone get pissed off here, please, this is just for fun!