I've found this bug a few times. There are pigs (not wildbores), Bunnymen, and bees all in groups, right next to each other! This has happened on land and ocean. Please fix this bug. I have looked at the bug tracker and nobody else reported this. I was using a mod, but i don't think that's the case. It is not a rare bug, because it has happened like three times, but it is not common. I don't know if it happens multiple times on one world. I found this first around December 2015. Keep up the good work!!
You just have to look around some worlds for it.