Why do all my Donkies/Yaks always huddle together on the left side?

Not the best screenshot but they would all be on the left side rather than spread out for a long time.

Is that the only place where they can eat from?

I can’t remember the specifics, but I think there’s something in the code that makes animals favor the left side of the screen rather than the right. Any mob that can walk around freely like your yaks and donkeys will tend to do that. It doesn’t matter whether their food access is on that side or not.