Indigenous trackers are able to tell by looking at a fallen leaf as to whether it was natural shed or was traumatic removed by a passing animal. I presume that this was done by examining the petiole of the fallen leaf and in particular the abscission zone. I have examined many leaves both shed and removed and cannot see a difference. Do you have any hints as to how this differentiation is made?

No idea. I often read native (US) pages on Facebook. You could ask one of them.
I have always found the state ag divisions of any state to be very knowledgeable.
The botany department of a college or university.
I would imagine that you might find some clues in the entire leaf and the entire plant - time of year, health of plant, dryness of leaves, spots and signs of disease, if any other leaves fell....

I don't think it is that complicated. What type of plant (perrenial) deciduous tree, forest environment, are u referring to. A residential area of maple trees, shrubs, what ?
if you examine the petiole and it seperates easily, it is either from trauma at the root, not enough water or over watering. It is a grab bag. If it has seperated from an animal passing through, then, it will be a tear.