I am no expert and haven’t played this game for very long, but I managed to tame a green lizard after a couple of attempts. It even followed me into a shelter and the next morning, it was dead - and I have no clue why. I wasn’t holding anything so I can’t have accidentally speared it, and while it did briefly fight with another green lizard at the start of the cycle, it didn’t behave any different afterwards so I don’t think it was hurt badly.

Is this a glitch or can they die to injury way later?

PS: I was playing as the Monk and had pretty low Karma due to a couple of botched taming attempts, if that makes any difference. Inside of the shelter, I had stored a rock(?) and one of those blue fruit things.