I was making an area for some wolves in creative mode when I heard a wolf taking damage. It was getting hurt because it walked into a wall and got stuck in it and started suffocating. If you put a wolf in a 1x1 pen surrounded by solid blocks and hold a bone, it will jump through the blocks around it like they aren't there but still take suffocation damage. I tried this with other mobs, and they fell into blocks and suffocated when they tried to jump over them. I also tried spawning mobs on top of a pillar, and they fell until they reached ground level and suffocated too.