It is most likely a combination of things 1. Vanilla SP minecraft Sheep like to stick to the corner of fences like that. 2. on EMC, sheep only bounce off of each other when sheared and stuff. (no reason to separate unsheared sheep)
animals tend to randomly 'wander' towards the southeast corner. It's a weird phenomenon Just how the game mechanics work.
Do you happen to live next to any power lines? I just think it's an EMC thing. I was building on my res, turned to do something and saw this weird thing on my neighbor's. I went to investigate and it was a bunch of horses doing this. I think if you just push them apart they stop.
This crowding in one corner behavior has been reported as a bug for several versions before the current one. It has not been fixed and doesn't seem to be an issue anyone cares to address. I've heard that jumping in the crowd will make them disperse. I have also seen it suggested that if fence isn't used in the corners, (try cobble blocks) then they don't seem to collect. I can't confirm those tips. The recent changes to EMC mob collision code doesn't play into the behavior that we know of. The collision code change does prevent this buildup from creating massive server lag, so it's not as much of a concern as it used to be.
it is a vanilla mc bug. There was another thread about this before. Put some blocks on top of the fence corner I think someone said fixes it.
