Just how long could wildlife that dont live in the ground on in the ground survive. Animals would need rest but these walkers never have to stop
I think that wildlife would actually thrive in this type of scenario. Less roadkill, less human intervention with their habitats, less hunting, etc... and walkers are generally slow and stupid... smaller animals have to be hard for them to catch. I can't imagine them often being able to catch rabbits, squirrels, etc.
As for the walkers never having to stop, in the comics there is evidence that eventually they "run out of gas." I'm a bit behind in the comics to see if this was really explained in much detail.