Animal Ambush?

Passive mobs, at least in a superflat world, wander off to the farthest render distance in any and all directions. Going to the farthest point of a render distance from spawn shows that the mobs have created a ring around your central location, creepy. Anyway, im pretty sure mobs aren't supposed to wander off that much. (the photo isn't me just spawning a bunch of mobs, this an actual problem)