nor it can legally hold copyrightThe owner of the macaque can own copyright. In this case, they probably do.
I don't know whether the pics were taken in the wild, or in a zoo/park. In the latter case, I agree the zoo/parc owner and the photographer may dispute about copyright, and probably be entitled to share it.
the creative action of setting up the environment makes the copyright belong to the photographer.But he didn't: he set up the camera, not the creative environment. If the camera had been fixed with a tripwire of some kind, then the photographer could claim ownership. As soon as the macaque takes physical control of framing the shot, it's no longer the photographer's.
The photographer, according to his version, did make the camera available to the monkeys in a "ready-to-shoot" mode. I claim he was creative enough, up to the point that he's the first man having intentionally made monkeys take a selfie.
If the button was triggered by a motion sensor, I'd say that both author and copyright holder are the photographer (as the motion sensor is inanimate).Correct result, wrong reason. The reason is that your setup of the motion sensor is deterministic: it's known, with a very high degree of certainty, what the framing of the shot will be. The fact that you determined the framing (even if that's in advance) is what makes you the creative force of the photo.
I disagree (respectfully! ;-) ). According to your definition, if I set a random timer, and put my camera on a motorized dolly with random movements, then I give up copyright, because I give up on deciding the timing and framing of my picture. On the contrary, I claim that my act of will of setting up a random timing and framing in a particular environment is my act of creativity, for whose result I own the copyright.
the customer pays a fee to the machine, to hold the copyright of the resultYou're assuming an implicit contract, which would require explicit statutory language, or a long history of common law. I wouldn't accept that assertion from anyone short of an IP lawyer.
Right, I agree I don't remember reading a contract before jumping into one of those automatic booths. (Maybe there's one in small letters somewhere?)