With non-human animals, though, aren't there much fewer possibilities than with humans? Most animals don't have the kind of food surpluses humans have, and so have can't afford to spend energy on things that aren't hunting or gathering food, fighting over territory, or reproducing.

So if an animal is doing something prominently that isn't hunting or fighting or mating or raising young and others are watching but not getting upset by it, mating display is probably a reasonably safe assumption.