This post is invalid due to my process, please disregard my conclusions.
See a later post for the problem.
So, initially I thought this was going to be a time-intensive task. it turned out to be simple.
TLDR: if you want an offensive buff on a pet as shown by the icon, use the recommended food.
List of pets (I limited to these since there was little overlap in preferred food)
Greater bear, sand reaper, spider, multiple hyenas greater and small
I removed all food from the pet feeder, then removed all food from the pets. I then put stacks of honey in the feeder. After some time, all pets had grabbed 5 pieces of honey. Most of the pets still had the buff, but I suspect that was from leftover partial pieces of food.
<Insert Netflix and lunch here while partial pieces of food were exhausted>
With all honey, no pets had the buff except for the bear, which is in his list of preferred food. None of the other pets had the buff; none listed honey as a preferred food.
I then put 1 piece of putrid meat in the feeder and removed all food from the spider.
After a short time, the spider had pulled the putrid meat (a preferred food) and 4 pieces of honey from the feeder. Verifying the putrid meat was gone from the feeder, and the spider had only a 4-stack of honey indicates he ate the meat. He displayed the buff icon.
I repeated the process with the sand reaper and got identical results (putrid meat is on his list). He was farther away from the feeder box.
From that, I can only conclude the TLDR above.
Anyone see holes in the test? Feedback, positive or negative, is encouraged.