So, I just started painstakingly recording all of the rewards I get for feeding these animals: Spreadsheet here
As you can see, this would take forever to fill out with enough info to be statistically significant. My progress alone will be incredibly slow.
If you want to help, feel free to make your own copy of my "Template" sheet for your own records. Then, link it here so that I can copy it from time to time. I'd be grateful. If the way this system works is known, I would very much appreciate an explanation or a link to one. Even if it's just a theory.