Recent studies — and generations of experience — show that many animals have a rudimentary sense of fair play and equity.
I think an example of that shows up in the cases where a female animal will “adopt” and nurse a baby from another species.
I had two cats once. One was the most unfriendly animal I have ever been around. That cat was my xwife’s. The other cat I called Punkin Kitty. Real sweetie. I got from the pound. Born to a feral mother. Was like a little puppy. The other cat(Puff) use to boss it around.
However if another cat came around Punkin kitty, Puff was on it like lighting. Taking care of Punkin Kitty. Really interesting behavior.
John